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Background: This study aims to conduct a finite element analysis (FEA) to assess the bio-mechanical properties of C2 sagittal-parallel pedicle screw (PPS) in fixation for atlantoaxial instability, thereby providing a theoretical foundation for its clinical application., Methods: A total of 5 intact C1-2 finite element models were established. Based on this, instability models were developed and two different fixation methods were applied for each model: C1 lateral mass screw (LMS) combined with C2 sagittal-parallel pedicle screw (C1LMS + C2PPS), and C1 lateral mass screw combined with C2 traditional pedicle screw (C1LMS + C2PS). Under a physiological load of 40 N, a pure moment of 1.5 Nm was used to simulate movements of the cervical spine in flexion, extension, lateral bending, and axial rotation. The von Mises stress of implants and the segment range of motion (ROM) were analyzed and compared statistically., Results: The intact model was validated and showed good consistency with other studies in terms of range of motion (ROM). In flexion and extension, the C1LMS + C2PPS resulted in lower segment ROM (12.4% and 6.3% decrease) and stress concentration (15.9% decrease in flexion) compared to C1LMS + C2PS. However, in lateral bending and axial rotation, the C1LMS + C2PPS exhibited higher segment ROM (42.9% and 5.9% increase) and stress concentration (8.7% and 21.4% increase) compared to C1LMS + C2PS., Conclusion: Both methods were safe and stable for the fixation of atlantoaxial instability. Compared to C1LMS + C2PS, the use of C1LMS + C2PPS may provide better stability and a lower risk of implant failure in flexion and extension. Clinically, it is feasible to utilize the C2 sagittal-parallel pedicle screw in fixing atlantoaxial instability., Competing Interests: Declarations Ethics approval and consent to participate We obtained the upper cervical CT data consent from the patients to be used in our study. This study involving human CT data has been approved by the ethics committee of Zigong Fourth People’s Hospital (No. 02, 2013) and were in accordance with the ethical standards of the 1964 Helsinki declaration. Written informed consent was obtained from all individual participants included in the study and the informed consent phrase is mandatory. Consent for publication Not applicable. Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Background: Patients with L4-S1 lumbar degenerative disease (LDD) with osteoporosis are prone to sacral-screw loosening during spinal internal fixation. We aimed to compare the clinical efficacy and imaging results of sacral bicortical, tricortical, and polymethylmethacrylate (PMMA)-augmented pedicle-screw fixation in the treatment of L4-S1 LDD with osteoporosis., Methods: This is a retrospective study, 72 patients were enrolled and divided into three groups according to the S1-screw fixation method: PMMA-augmented pedicle-screw fixation (Group A, n = 26), bicortical fixation (Group B, n = 22), and tricortical fixation (Group C, n = 24). The visual analog scale (VAS) and Oswestry disability index (ODI) were recorded preoperatively and at the last follow-up, and the postoperative complications, screw-loosening rate, and fusion rate were compared between the three groups., Results: Upon the last follow-up, the VAS and ODI scores of the three groups were significantly improved compared with those recorded preoperatively. The VAS and ODI scores of Group A were significantly smaller than those of Groups B and C (P < 0.05), with no significant difference between Groups B and C. Moreover, the screw-loosening rate of Group A was significantly lower than that of Groups B and C (P < 0.05), with no significant difference between Groups B and C. No significant difference was noted in postoperative complications, bone-cement leakage rates, and intervertebral fusion rates among the three groups. Furthermore, we found that osteoporosis and change of lumbar lordosis(LL) value were independent risk factors for sacral-screw loosening in patients with L4-S1 LDD with osteoporosis., Conclusions: When patients with L4-S1 LDD with osteoporosis undergo lumbosacral fusion and fixation, the use of S1 pedicle screws with PMMA augmentation has better stability and less screw loosening. Furthermore, we recommend this surgery for patients with osteoporosis, and the LL should be increased as much as possible during the operation to restore the matching of lumbar and pelvic parameters., Competing Interests: Declarations Ethics approval and informed consent This study has been reviewed and approved by the appropriate ethics committee of The First Affiliated Hospital of Guangzhou University of Chinese Medicine (NO. K–2024–046). Consent for publication All authors read and approved the final manuscript. Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Background: With the increasing number of surgeries utilizing spinal instrumentation, three-dimensional surgical navigation aims to improve the accuracy of implant placement. However, its widespread clinical adaption has been hindered by factors such as high radiation exposure and interference with standard surgical workflows., Methods: X23D is a novel AI-based fluoroscopy reconstruction technique that generates a 3D anatomical model of the spine from only four fluoroscopy images. Based on this technology, we developed a prototype for the surgical navigation of pedicle screws placement of the lumbar spine, visualizing the 3D-reconstructed spine anatomy and the surgical drill position in real-time. An ex-vivo study was conducted to compare the accuracy of the X23D-based navigation approach with fluoroscopy-aided freehand instrumentation. Five board-certified surgeons placed pedicle screws on six human torsi within a realistic surgical environment. Breach rate, site and extent (Gertzbein-Robbins) were evaluated in postoperative CT scans, as well as execution time, radiation dose, and user experience. Specimens, operating side, and surgeon were randomised., Results: Forty-nine pedicle screws (n = 24 × 23D, n = 25 2D-fluoroscopy) were evaluated, with six breaches occurring in the control group, one of which was considered clinically significant (medial breach grade C). Five breaches with one clinically significant breach were observed in the X23D group. Breach rate, execution time for each lumbar level (X23D 167 s vs. control 156 s), radiation dose (X23D 33.26 mGy vs. control 49.5 mGy), and user experience did not reveal significant differences (p > 0.05) between the groups., Conclusions: Spinal navigation using the X23D-based approach shows promise and performs well in a realistic surgical ex-vivo setting. With further refinements, its accuracy is expected to match clinical-grade navigation systems while reducing radiation dose., Competing Interests: Declarations Ethical approval The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the local ethical committee (Kantonale Ethikkommission Zurich BASEC No. 2021 − 01083). Clinical trial number: not applicable. Consent to participate All human specimens were sourced from Science Care (Phoenix, Arizona). Body donors and their next of kin agreed by written informed consent to the postmortem use of their body for research purposes. Consent for publication All authors have approved the manuscript and agree with its submission to BMC Musculoskeletal Disorders. Written informed consent was obtained from all body donors and their next of kin. Competing interests The authors declare the following personal relationships which may be considered as potential competing interests: Mazda Farshad reports a relationship with X23D AG that includes: equity or stocks. Hooman Esfandiari and Philipp Fürnstahl report a relationship with X23D AG that includes: board membership and equity or stocks. Hooman Esfandiari, Philipp Fürnstahl and Mazda Farshad have a patent #WO2023156608A1 pending to University of Zurich. Hooman Esfandiari, Philipp Fürnstahl, Mazda Farshad, and Sascha Jecklin have a patent ”A computer-implemented method, device, system and computer program product for processing anatomic imaging data” pending to University of Zurich., (© 2024. The Author(s).)

Background: To evaluate the feasibility of C2 laminar screw (C2LS) fixation assisted by double holes and to explore a novel method for judging its safe positioning., Methods: The Digital Imaging in Communications format data of 25 C2 vertebrae specimens were obtained by computed tomography thin-slice scanning, and the data were imported into Mimics software for three-dimensional reconstruction. The bone cortex was removed at the starting and terminal midpoints of the lamina as the observation holes. Points A, M, and P represented the three different entry points of the C2LS. Point M was designated as the central entry point, point A was 1 mm from the extension surface of point M to the ventral side, and point P was 1 mm from the extension surface of point M to the dorsal side. Further classified into groups A, M, and P based on the screw path correlation parameters at each entry point. The distance between holes 1 and 2 (D1 and D2) was measured at the maximum safe inclination, parallel, and maximum safe extroversion positions when the screw-insertion points of C2LS were at the center points A, M, and P, respectively. The data of D1 and D2 of the three groups (A, M, P) in different screw directions were analyzed and compared., Results: Twenty-five specimens were measured in the parallel, maximum safe inclination, and maximum safe extroversion groups. In the parallel relationship, there were significant differences in the D1 and D2 data between the M and P groups. In the introversion relationship, there were significant differences in the D1 and D2 data between the M and P groups. In the extroversion relationship, there were significant differences in the D1 and D2 data among the A, M, and P groups, respectively., Conclusion: Use of the C2LS assisted by double holes was able to determine the safe position of the screw in operation. When D1 is greater than D2, the screw position can be considered relatively safe, with the intraoperative visual manifestation of a deep screw in hole 1 and a shallow screw in hole 2. If D1 is close to D2, it is necessary to ensure that the screws in both holes 1 and 2 are shallow, then the screw position is safe. If the screw in hole 1 is observed to be shallower than in hole 2 during surgery, regardless of the entry point position, there is a significant risk of ventral cortical perforation. Especially when the entry point is more anterior, even when inserting the screw parallel to the lamina, caution must be taken against the risk of ventral cortical perforation., Competing Interests: Declarations Ethics approval and consent to participate The study was performed in accordance with the Declaration of Helsinki and was reviewed and approved by the ethics committee of Ningbo university, China. The number: CHEC2009-066. Informed consent All individuals providing cadaver specimens must sign an informed consent for cadaver donation at the Institute of Anatomy, Ningbo university. This consent includes the use for scientific research. The consent for cadaver donation was obtained from family members. Consent for publication All individuals providing cadaver specimens must sign an informed consent for cadaver donation at the Institute of Anatomy, Ningbo university. This consent includes the use of the cadaver for scientific research and publication. Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Cervical pedicle screws (CPS) provide biomechanically superior fixation compared to other techniques but are technically more demanding. Navigated CPS placement has been increasingly reported as a safe and accurate technique, yet there are few studies comparing different combinations of imaging and navigation systems under comparable conditions. With this study, we aimed to compare different imaging and navigation systems for CPS placement in terms of accuracy, screw placement time and applied radiation dose. For this experimental study, navigated CPS placement was performed at levels C2 to C7 in 24 identical radiopaque artificial spine models by two surgeons with different levels of experience using three different combinations of intraoperative 3D imaging devices and navigation systems. Accuracy, time and radiation dose were compared between the groups. In total, 288 screws were placed. Accuracy was > 98% in all groups with no significant differences between groups or between surgeons (P = 0.30 and P = 0.31, respectively), but the inexperienced surgeon required significantly more time (P < 0.001). Radiation dose was significantly higher with iCT compared to CBCT (P < 0.0001). Under experimental conditions, accuracy rates of > 98% were achieved for navigated CPS placement regardless of the imaging modality or navigation system used. Radiation doses were significantly lower for CBCT compared to iCT guidance., Competing Interests: Declarations Competing interests The research group MINTOS had grants/grants pending and technical support from Siemens Healthineers (Erlangen, Germany) and Nuvasive Inc. (San Diego, California, USA). The funders were not involved in the study conceptualization, design, data collection, analysis, decision to publish or the preparation of the manuscript. PAG serves as unpaid member of a consulting/advisory board for Siemens Healthineers. The other authors declare that they have no financial or non-financial interests to disclose. IRB approval Not applicable due to the experimental character of the study., (© 2024. The Author(s).)

Objective: This study was aimed to explore the mid-term efficacy of non-contact orthopedic robot navigation in the treatment of lumbar spondylolisthesis., Methods: The clinical data of young and middle-aged patients with lumbar spondylolisthesis were retrospectively analyzed and divided into an observation group and a control group according to surgical methods. The observation group was treated with minimally invasive transforaminal interbody fusion (MIS-TLIF) combined with orthopedic robot-navigated percutaneous pedicle screw fixation; while the control group underwent traditional posterior lumbar interbody fusion (PLIF). Perioperative indicators, waist and leg pain Visual Analog Scale (VAS) scores, Oswestry Disability Index (ODI), and complications were compared between groups., Results: A total of 32 patients with lumbar spondylolisthesis were included in this study, with the average age of 50.3 ± 2.7 years old. There were 17 patients in the observation group and 15 patients in the control group. Although the new surgical technique for the observation group may require longer operative time, it showed significant advantages in reducing intraoperative bleeding, postoperative drainage, and shortening hospital stay. These benefits might result in faster recovery for patients, reduced risk of complications, and improved overall quality of life. The new technology was also significantly better compared to the traditional method in terms of VAS scores and ODI at 1 week, 1 month, 3 months, and 6 months post-surgery. These results provided patients with better treatment options and potentially a faster path to recovery. One case with infectious incision in the observation group and one case with intraspinal hematoma formation in the control group were observed. However, there was no statistical difference in the complication rates between the two groups (P > 0.05)., Conclusion: The non-contact orthopedic robot navigation for the treatment of lumbar spondylolisthesis was demonstrated to be minimally invasive, precise, and stable surgical method. It is a treatment option worth considering for suitable patients., (© 2024. The Author(s).)

Background and Purpose: Percutaneous cement augmentation has been reported as an effective salvage procedure for frail patients with spinal instrumentation failure, such as screw loosening, hardware breakage, cage subsidence, and fractures within or adjacent to stabilized segments. Favorable results were reported during a median follow-up period of 16 months in a retrospective analysis of 31 consecutive procedures performed in 29 patients. In the present study, the long-term effectiveness of this treatment in avoiding or postponing revision surgery is reported., Materials and Methods: Clinical and radiologic data of our original cohort of patients were retrospectively collected and reviewed to provide an extended follow-up assessment. The need for revision spinal surgery was assessed as the primary outcome, and the radiologic stability of the augmented spinal implants was considered as the secondary outcome., Results: An extended radiologic follow-up was available in 27/29 patients with an average of 50.9 months. Overall, 18 of 27 (66.7%) patients, originally candidates for revision surgery, avoided a surgical intervention after a cement augmentation rescue procedure. In the remaining patients, the average interval between the rescue cement augmentation and the revision surgery was 22.5 months. Implant mobilization occurred in 2/27 (7.4%) patients; rod breakage, in 1/27 (3.7%); a new fracture within or adjacent to the instrumented segment occurred in 4/27 (14.8%) patients; and screw loosening at rescued levels occurred in 5/27 (18.5%) patients., Conclusions: In this cohort, cement augmentation rescue procedures were found to be effective in avoiding or postponing revision surgery during long-term follow-up., (© 2024 by American Journal of Neuroradiology.)

Objective: To investigate the correlation between the implantation status of the ROI-C cervical cage plates and the Hounsfield unit(HU) value of the target vertebral endplate during anterior cervical decompression and fusion (ACDF)surgery., Methods: Review of patient data undergoing ACDF from January 2018 to December 2021. Data on gender, age, body mass index, history of hypertension, diabetes, hyperlipidemia, smoking, alcohol consumption, cervical cage plates status, and HU values of the cervical vertebral endplate. Logistic regression analysis was used to evaluate the relationship between the HU values and the plates status., Results: A total of 17 cases (12.1%) had misplaced implants during surgery. There were statistical differences in gender, long-term smoking history, drinking history, and cervical vertebral endplate HU values between the abnormal implantation group and the normal implantation group (P < 0.05). The cervical vertebral endplate HU values in the abnormal implantation group were significantly higher than those in the normal implantation group (729.3 ± 36.2 HU vs. 484.4 ± 59.2 HU, P < 0.001). In the logistic regression analysis, cervical endplate HU value (OR 1.081; 95% CI 1.016-1.375) was an independent factor influencing improper plate implantation. The area under the ROC curve (AUC) for the cervical endplate HU value in predicting implantation difficulty was 0.836 (P < 0.05), with an optimal threshold of 724 HU (sensitivity 83.2%; specificity 90.4%)., Conclusions: The cervical vertebral segment endplate HU value can independently predict whether the implantation of the plates is misplaced during ACDF surgery., (© 2024. The Author(s).)

Porous interbody cages are often used in spinal fusion surgery since they allow bone ingrowth which facilitates long-term stability. However, the extent of bone ingrowth in and around porous interbody cages has scarcely been investigated. Moreover, tissue differentiation might not be similar around the superior and inferior cage-bone interfaces. Using mechanobiology-based numerical framework and physiologic loading conditions, the study investigates the spatial distribution of evolutionary bone ingrowth within randomly distributed porous interbody cages, having varied porosities. Finite Element (FE) microscale models, corresponding to cage porosities of 60 %, 72 %, and 83 %, were developed for the superior and inferior interfacial regions of the cage, along with the macroscale model of the implanted lumbar spine. The implant-bone relative displacements of different porosity models were mapped from macroscale to microscale model. Bone formation of 10-40 % was predicted across the porous cage models, resulting in an average Young's modulus ranging between 765 MPa and 915 MPa. Maximum bone ingrowth of ∼34 % was observed for the 83 % porous cage, which was subject to low implant-bone relative displacements (maximum 50μm). New bone formation was found to be greater at the superior interface (∼34 %) as compared to the inferior interface (∼30 %) for P83 model. Relatively greater volume of fibrous tissue was formed at the implant-bone interface for the cage with 60 % and 72 % porosities, which might lead to cage migration and eventual failure of the implant. Hence, the interbody cage with 83 % porosity appears to be most favorable for bone ingrowth, provided sufficient mechanical strength is offered., Competing Interests: Declaration of competing interest The authors state that there are no potential conflicts of interest with the article's research or publication., (Copyright © 2024 IPEM. Published by Elsevier Ltd. All rights reserved.)

The increasing frequency of cervical and lumbar spine disorders, driven by aging and evolving lifestyles, has led to a rise in spinal surgeries using pedicle screws. Robotic spinal surgery systems have emerged as a promising innovation, offering enhanced accuracy in screw placement and improved surgical outcomes. We focused on literature of this field from the past 5 years, and a comprehensive literature search was performed using PubMed and Google Scholar. Robotic spinal surgery systems have significantly impacted spinal procedures by improving pedicle screw placement accuracy and supporting various techniques. These systems facilitate personalized, minimally invasive, and low-radiation interventions, leading to greater precision, reduced patient risk, and decreased radiation exposure. Despite advantages, challenges such as high costs and a steep learning curve remain. Ongoing advancements are expected to further enhance these systems' role in spinal surgery., (© 2024 The Author(s). Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Background: Lateral lumbar interbody fusion (LLIF) is a minimally invasive fusion technique that can be performed with lateral plate. Insufficient contact between the endplate and bone graft may result in cage subsidence. This study aimed to investigate the potential risk factor for high-grade cage subsidence (HCS) occurring after LLIF supplemented with lateral plate., Methods: Between June 2017 and February 2023, 121 patients (48 males, 73 females; mean age 63.0 years; minimum follow-up period 12 months) undergoing LLIF supplemented with lateral plate were retrospectively reviewed. The incidence of HCS was assessed, and patients were categorized into HCS group or non-HCS group based on the occurrence of HCS. A revision surgery of posterior pedicle screw fixation was performed in patients with cage subsidence and complained with intolerable back pain or radicular symptoms. Comparative analyses were performed on demographic characteristics, surgical variables, and parameters related to endplate-bone graft contact between the two groups. Multivariable logistic regression analysis was employed to identify the potential risk factors associated with HCS. The receiver operating characteristic (ROC) analysis was used to calculate the cutoff values for the risk factors. Clinical outcomes were evaluated using Oswestry Disability Index (ODI), and radiographic fusion at the final follow-up was assessed based on the Bridwell grading system., Results: The HCS group comprised 12 patients, while the non-HCS group included 109 patients. The incidence of HCS occurring after LLIF supplemented with lateral plate was 9.9 %. Compared to non-HCS group, patients in HCS group had lower sagittal and coronal endplate-bone graft contact rates and larger cage-endplate angles. Low sagittal (OR, 1.099; 95 % CI, 1.033-1.169; P=0.003) and low coronal (OR, 1.149, 95 % CI, 1.061-1.243, P=0.001) endplate-bone graft contact rates were determined to be correlated with HCS. The cutoff value of the sagittal and coronal endplate-bone graft contact rate was 63.5 % and 60.9 %. Eleven (91.7 %) patients in HCS group underwent revision posterior pedicle screw fixation. Both HCS and non-HCS groups experienced significant improvements in ODI at the final follow-up, while there were no differences between groups. Ninety-five (87.2 %) patients in non-HCS group, and nine (81.8 %) of the 11 patients who underwent revision surgery in HCS group achieved radiographic fusion at the final follow-up., Conclusions: The incidence of HCS occurring after LLIF supplemented with lateral plate was 9.9%. Insufficient endplate-bone graft contact is an important risk factor of HCS, and sagittal and coronal endplate-bone graft contact rates can be used as effective predictors for HCS., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background and Objectives: Optimal iliac screw position in relation to the sciatic notch remains unknown. In 12 cadavers undergoing S2 alar-iliac (S2AI) screw placement, we tested the pullout strength of screws placed in proximity to the sciatic notch (≤5 mm) vs farther away from the sciatic notch (>5 mm)., Methods: A biomechanical, cadaver-based study was performed on 12 cadavers undergoing bilateral S2AI screw insertion. The position of the S2AI screw regarding the sciatic notch was dichotomized as ≤5 mm from the sciatic notch on the right side and >5 mm on the left side, confirmed using c-arm fluoroscopy. The primary outcome was the pullout strength of the screw (N). Secondary outcomes were stiffness (N/mm), yield force (N), and work to failure (N mm). Ischial tuberosity was embedded into polymethyl methacrylate and secured to a custom 3-axis vise grip mounted to a 14.5-kN load cell. Pullout testing was performed at 5 mm/min. Force and displacement data were collected at 100 Hz and evaluated using MATLAB. The Mann-Whitney test was performed., Results: Of 24 S2AI screws, 3 screws could not be tested because of cement-bone interface failure. A positive though nonsignificant trend of screw pullout strength was found for screws close to the notch compared with those farther from the notch (861.8 ± 340.7 vs 778.7 ± 350.8 N, P = .859). Similarly, screws close to the notch demonstrated a higher trend of stiffness (149.4 ± 145.4 vs 111.34 ± 128.2 N/mm, P = .320) and force to yield (806.9 ± 352.0 vs 618.6 ± 342.9 N, P = .455). Conversely, screws farther from the notch had a higher but similarly nonsignificant area under the force-displacement curve (10 867.0 ± 9565.0 vs 14 196.6 ± 9578.3 N mm, P = .455), which might be due to excess sheer/translation force that could not be reliably quantified., Conclusion: Although placing S2AI screws ≤5 mm of the sciatic notch provided stronger fixation in 3 of 4 biomechanical testing categories, these results were not statistically significant. Therefore, placing S2AI screws ≤5 mm of the sciatic notch did not provide stronger fixation., (Copyright © Congress of Neurological Surgeons 2024. All rights reserved.)

Introduction: The evolution of MCGR technique has led to modifications in the configuration of the proximal construct to decrease the incidence of implant-related complications (IRC) and revision surgeries. However, there is no data characterizing the performance of the most used configurations reducing the risk of complications., Methods: 487 patients were identified from an international multicenter EOS database., Inclusion Criteria: EOS patients, primary dual MCGR, complete radiographs, and minimum of 2-year follow-up. 76 patients had incomplete X-rays, 5 had apical fusions, and 18 had inconclusive complications, leaving 388 patients for review. A digital spine template was created to document UIV; number of levels; number, type, and location of anchors; as well as implant configuration. First available postoperative and latest follow-up radiographs were reviewed by two senior surgeons and two spine fellows. UPROR due to IRC was defined as any change in proximal anchors between the postoperative and final follow-up radiographs., Results: The most common proximal construct configuration: UIV at T2 (50.0%) with 17.5% UPROR, followed by T3 (34.0%) with 12.1% UPROR; number of levels was three (57.1%) with 16.8% UPROR and two (26.0%) with 17.0% UPROR; number of proximal anchors was six (49.9%) with 14.1% UPROR and four (27.0%) with 18.3% UPROR. The most common anchors were all screws (42.0%) with 9.9% UPROR, and all hooks (26.4%) with 31.4% UPROR (P < 0.001). The construct with the lowest rate of UPROR was a UIV at T2, with six anchors (all screws) across three levels (42 cases), with 0% UPROR. Other construct combinations that yielded 0% UPROR rates were UIV of T3, six anchors (all screws) across three levels (25 cases), and a UIV of T3 with six anchors (screws and hooks) across three3 levels (9 cases)., Conclusion: Proximal anchor configuration impacts the incidence of UPROR due to IRC in MCGR. UIV at T2 and T3 compared to T4, and the use of all screws or combination of screws and hooks compared to all hooks were associated with a lower UPROR rate. The most common construct configuration was T2 UIV, three levels, six anchors, and all screws. The use of a combination of six anchors (screws or screws and hooks) across three levels with a UIV at T2 or T3 was associated with a lower UPROR rate. Additional research is needed to further evaluate the variables contributing to configuration selection and their association with IRC., (© 2024. The Author(s), under exclusive licence to Scoliosis Research Society.)

Background Context: Osteolytic lesions caused by infection or metastatic disease of the spine can induce instability. Different surgical strategies are available to restore stability in this scenario, however little is known how various reconstruction techniques affect spinal biomechanics., Purpose: To analyze and quantify the biomechanical effects of three different surgical reconstruction techniques in the treatment of a T12 osteolytic model., Study Design/setting: Finite element analysis of the thoracic spine with a T12 osteolytic lesion., Methods: Using CT scans from a 20-year-old man without structural deformity, simulation of an osteolytic lesion with a 50% defect at the posterior aspect of T12 vertebral body was created by a 490 N vertical force to T9. Next, three common instrumentation techniques treating the osteolytic lesion were modeled and biomechanically tested. These included: Model A, corpectomy with short segment fixation (T11-L1) and two long-segment instrumentations; Model B long segment fixation with triple rod construct; Model C long segment fixation with dual rod construct. A load of 480N was then applied on the spine models in vertically downward direction on T9. Von Mises stresses were measured (MPa) in the discs, vertebrae, and implants., Results: Model A demonstrated the lowest stress on construct material, adjacent vertebral bodies, and discs but increased stress on the instrumented vertebrae. Model B was more rigid and demonstrated lower construct stress compared to Model C. However, Model C had the lowest vertebral body stress in flexion, extension, and lateral bending in the most upper instrumented vertebral body, but the highest screw pull-out stress when compared to Model A and Model B., Conclusions: This osteolytic T12 model provides unique biomechanical data that can help to tailor surgical strategies in select scenarios. While optimal outcomes are best achieved with a construct tailored to a specific patient's need for stabilization, our findings can be generalized for instances of cancerous lesions, low bone density, and infectious causes., Clinical Relevance: The results of this study can help with the choice of appropriate surgical reconstruction technique based on patient-specific characteristics., Competing Interests: Declaration of competing interest One or more of the authors declare financial or professional relationships on ICMJE-TSJ disclosure forms., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Study Design: Retrospective multicenter study., Objective: To examine the shape change of screw-rod constructs over time after short-segment lumbar interbody fusion and to clarify its relationship to clinical characteristics., Summary of Background Data: No study has focused on the shape change of screw-rod constructs after short-segment fusion and its clinical implications., Methods: One hundred eight patients who had single-level lumbar interbody fusion with pedicle screws and cages were enrolled. Three-dimensional (3D) images of screw-rod constructs were generated from baseline CT on the day after surgery and follow-up CT and were superposed on the right and left side, respectively, using the iterative closest point algorithm. The shape change was quantitatively assessed by computing the median distance between the 3D images, which was defined as the shape change value. Among the 5 time-course categories of follow-up CT (≤1, 2-3, 4-6, 7-12, and ≥13 months), the shape change values were compared. The relationships between the shape change values and clinical characteristics, such as age, CT-derived vertebral bone mineral density, screw and rod materials, and postoperative interbody fusion status, cage subsidence, and screw loosening, were evaluated., Results: A total of 237 follow-up CTs were included (≤1 [34 scans], 2-3 [33 scans], 4-6 [80 scans], 7-12 [48 scans], and ≥13 months [42 scans]) because many patients underwent multiple follow-up CTs. There were significant differences in shape change values among the time-course categories ( P <0.001 in Kruskal-Wallis test). Most shape changes occurred within 6 months postoperatively, with no significant changes observed at 7 months or more. There were no significant relationships between the shape change values and each clinical characteristic., Conclusions: The temporal shape changes of screw-rod constructs following short-segment lumbar interbody fusion progressed up to 6 months after surgery but not significantly thereafter., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Objective: The cortical bone trajectory (CBT) technology is an effective substitute for traditional pedicle screw (PS) technology. However, there is still controversy about the CBT screw technology placement strategy. The objective of this study was to simulate cortical screw placement with the help of three-dimensional (3D) software, to discuss the differences in screws between genders and vertebral segments, and to explore a safer and more efficient strategy for cortical screw placement., Methods: Mimics Medical software was used to construct a 3D model of the lumbar spine, and the placement of CBT screws was simulated. The volume of each vertebral body from L1 to L5, the pedicle isthmus height (IH), the pedicle isthmus width (IW), and the sagittal vertebral distance (SAVD) were measured. The transverse distance (TD) and the longitudinal distance (LD) between the ideal starting point (SP) and the clinical SP (the intersection Q of the midline of the superior articular process and the horizontal line 1 mm below the transverse process) were measured. The cephalad angle (CA), lateral angle (LA), maximum screw diameter (MSD), maximum screw length (MSL) of each trajectory of the L1 to L5 vertebral bodies, and the percentage of the screw insertion depth (PSID) into the vertebral body were measured. Data were statistically analyzed using Student's t-test, one-way analysis of variance (ANOVA), and Tukey's test., Results: Vertebral anatomical parameters and CBT screw parameters differed between males and females. Female patients had lower IH, IW, SAVD, CA, LA, MSD, and MSL than males. IH was greatest in L1 (male, 17.81 mm; female, 16.12 mm) and the smallest in L5 (male, 14.11 mm; female, 13.05 mm). IW was smallest in L1 (male, 8.89 mm; female, 7.37 mm) and greatest in L5 (male, 16.59 mm; female, 15.43 mm). The MSD of males was smallest in L1 (6.05 mm) and greatest in L3 (7.06 mm); the MSD of females was smallest in L1 (5.13 mm) and greatest in L4 (6.64 mm). MSL was greatest at L3 (male, 33.63 mm; female, 32.28 mm) and smallest at L5 (male, 31.25 mm; female, 29.97 mm). CA was smallest in L1 (male, 22.80°; female, 21.92°) and greatest in L3 (male, 25.29°; female, 24.33°). LA was smallest in L1 (male 12.37°, female 11.27°) and greatest in L5 (male 13.56°, female 12.96°). Among the males, TD was smallest at L1 (-0.51 mm) and greatest at L5 (1.37 mm), while LD was greatest at L2 (3.46 mm) and smallest at L5 (2.40 mm). In females, TD was greatest at L1 (0.12 mm) and smallest at L3 (-0.51 mm), while LD was greatest at L1 (3.69 mm) and smallest at L5 (2.08 mm). In the overall sample, the incidence of SAVD and PSID gradually increased from L1 to L5., Conclusion: The optimal screw placement strategy for CBT screws varies significantly according to sex and vertebral body segments, particularly noting the specificity of screw placement at L5. The optimal screw placement strategy should be selected based on the patient's sex and segment characteristics before surgery to maximize the safety and accuracy of CBT screw placement., (© 2024 The Author(s). Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Cage subsidence after instrumented lumbar spinal fusion surgery remains a significant cause of treatment failure, specifically for posterior or transforaminal lumbar interbody fusion. Recent advancements in computational techniques and additive manufacturing, have enabled the development of patient-specific implants and implant optimization to specific functional targets. This study aimed to introduce a novel full-scale topology optimization formulation that takes the structural response of the adjacent bone structures into account in the optimization process. The formulation includes maximum and minimum principal strain constraints that lower strain concentrations in the adjacent vertebrae. This optimization approach resulted in anatomically and mechanically conforming spinal fusion cages. Subsidence risk was quantified in a commercial finite element solver for off-the-shelf, anatomically conforming and the optimized cages, in two representative patients. We demonstrated that the anatomically and mechanically conforming cages reduced subsidence risk by 91% compared to an off-the-shelf implant with the same footprint for a patient with normal bone quality and 54% for a patient with osteopenia. Prototypes of the optimized cage were additively manufactured and mechanically tested to evaluate the manufacturability and integrity of the design and to validate the finite element model., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Purpose: To assess the effect of various pelvic fixation techniques and number of rods on biomechanics of the proximal junction of long thoracolumbar posterior instrumented fusions., Methods: A validated spinopelvic finite-element (FE) model was instrumented with L5-S1 ALIF and one of the following 9 posterior instrumentation configurations: (A) one traditional iliac screw bilaterally ("2 Iliac/2 Rods"); (B) T10 to S1 ("Sacral Only"); (C) unilateral traditional iliac screw ("1 Iliac/2 Rods"); (D) one traditional iliac screw bilaterally with one midline accessory rod ("2 Iliac/3 rods"); (E) S2AI screws connected directly to the midline rods ("2 S2AI/2 Rods"); and two traditional iliac screws bilaterally with two lateral accessory rods connected to the main rods at varying locations (F1: T10-11, F2: T11-12, F3: T12-L1, F4: L1-2) ("4 Iliac/4 Rods"). Range of motions (ROM) at T10-S1 and T9-T10 were recorded and compared between models. The T9-T10 intradiscal pressures and stresses of the T9-10 disc's annulus in addition to the von Mises stresses of the T9 and T10 vertebral bodies were recorded and compared., Results: For T10-S1 ROM, 4 iliac/4 rods had lowest ROM in flexion and extension, while 2 S2AI/2 rods showed lowest ROM in rotation. Constructs with 3 or 4 rods had lower stresses on the primary rods compared to 2-rod constructs. At the proximal adjacent disc (T9-10), 4 iliac/4 rods showed lowest ROM, lowest intradiscal pressures, and lowest annular stress in all directions (most pronounced in flexion-extension). Under flexion and extension, 4 iliac/4 rods also showed the lowest von Mises stresses on the T10 vertebral body but the highest stresses on the T9 vertebral body., Conclusions: Dual iliac screws with 4 rods across the lumbosacral junction and extending to the thoracolumbar junction demonstrated the lowest T10-S1 ROM, the lowest adjacent segment disc (T9-T10) ROM, intradiscal pressures, and annular stresses, and the lowest UIV stresses, albeit with the highest UIV + 1 stresses. Additional studies are needed to confirm whether these biomechanical findings dictate clinical outcomes and effect rates of proximal junctional kyphosis and failure., (© 2024. The Author(s).)

Purpose: Despite standardized biomechanical tests for spinal implants, we recently recognized pedicle screw failure to maintain the rod fixated as a clinical concern in scoliosis surgery. This occurrence study investigates the risk and magnitude of axial rod slip (ARS), its relation with technique and preventive measures., Methods: Retrospective multicenter review of all primary scoliosis cases (2018-2020) with > 1 year FU from three centers, instrumented with uniplanar screws and 5.5 mm CoCr rods (Mesa 2, Stryker Corporation, Kalamazoo, MI, USA). ARS was defined as > 1 mm change in residual distal rod length from the screw in the lowest instrumented vertebra (LIV) and assessed by two independent observers. Slip distance, direction, relation to distal screw density and time of observation were recorded, as well as the effect of ARS on caudal curve increase. To prevent slip, more recent patients were instrumented with a different end-of-construct screw (Reline, NuVasive Inc. San Diego, CA, USA) and analyzed for comparison., Results: ARS risk was 27% (56/205) with a distance of 3.6 ± 2.2 mm, predominantly convex. 42% occurred before 4 months, the rest before 1 year. The caudal curve substantially increased three times more often in patients with ARS. Interobserver reliability was high and slip was in the expected direction. ARS was unrelated to distal screw density. Remarkable variation in ARS rates (53%, 31%, 13%) existed between the centers, while there was no difference in mean screw density (≈1.3 screws/level) or curve correction (≈60%). Revision surgery for ARS was required in 2.9% (6/207). Using the different end-of-construct screw, ARS risk was only 2% (1/56) and no revisions were required., Conclusion: This study demonstrates the prevalence of axial rod slip at the end of construct in scoliosis surgery and its clinical relevance. While minimal ARS can be subclinical, ARS should not be mistaken for adding on. The most severe ARS predominantly occurred convex at the high-loaded distal screw when L3 was the LIV. Longer constructs (LIV L3 or L4) have a higher risk of ARS. The minimal risk of ARS with another end-of-construct screw underscores the influence of screw type on ARS occurrence in our series. Further research is essential to refine techniques and enhance patient outcomes., (© 2024. The Author(s).)

Objective: When implanting the Zero-P device, the screws of Zero-P form a bone wedge with a 40 ± 5° cranial and caudal angle (CCA). However, no study has been performed in the optimal CCA of the Zero-P implant. To investigate whether the cranial/caudal angles (CCA) of the screws affect the clinical and radiological outcomes in patients undergoing ACDF with the Zero-P implant., Methods: From January 2016 to December 2023, we retrospectively analyzed 186 patients who underwent 1-level ACDF with the Zero-P device. The patients were divided into four groups: group A (cranial angle ≤40°, caudal angle ≤40°); group B (cranial angle ≤40°, caudal angle >40°); group C (cranial angle >40°, caudal angle ≤40°); and group D (cranial angle >40°, caudal angle >40°). The clinical outcomes, including Japanese Orthopaedic Association (JOA), neck disability index (NDI), and visual analogue scale (VAS) scores, the radiological parameters, including cervical lordosis (CL), cervical lordosis of operated segments (OPCL), intervertebral space height (ISH) and fusion rate (FR), and the complications, were evaluated and compared. Parametric tests, non-parametric tests, and chi-square tests were conducted to analyze the data., Results: The OPCL of group A was significantly less than that of the other groups at the final follow-up (p < 0.05). The ISH of group D was significantly less than that of group A at the final follow-up (p < 0.05). The subsidence rate of group A was significantly less than that of group D at the final follow-up (p < 0.05). At the final follow-up, the upper adjacent-level degeneration (ASD) of group D was significantly less severe than that of groups A and B (p < 0.05). The clinical outcomes do not differ among groups (p > 0.05)., Conclusion: A larger CCA of the screws (cranial angle >40°, caudal angle >40°) was better for maintaining OPCL and reducing the incidence of ASD. A smaller CCA of the screws (cranial angle ≤40°, caudal angle ≤40°) was better for maintaining ISH and reducing the rate of subsidence., (© 2024 The Author(s). Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Background Context: Facet joint violation by pedicle screws may lead to adjacent-segment disease and postoperative pain. Previous studies have reported the incidence of rostral facet joint violation using various pedicle screw insertion techniques. However, the incidence of facet joint violations with robotic guidance has not been determined., Purpose: To investigate and compare the incidence of rostral facet joint violation by pedicle screws under robotic guidance and computerized tomography (CT) navigation guidance., Study Design/setting: Retrospective matched cohort., Patient Sample: All patients who underwent robotic-assisted lumbar fusion at a major spine center up until 2023 were retrospectively identified and matched 1:3 to patients undergoing CT navigation guidance based by on age, sex, rostral vertebral level, and length of construct. Inclusion criteria consisted of age greater than 18 years, bilateral pedicle screw fixation, and presence of a postoperative CT scan of the lumbar spine or abdomen/pelvis at any point in the postoperative period., Outcome Measures: Rostral facet joint violations., Methods: Descriptive statistics were used to compare cohorts: frequencies, chi-squared analysis for categorical variables, and t-test for continuous variables., Results: A total of 408 rostral pedicle screws were implanted in 204 patients (Robot: 102; Navigation: 306). Overall, 13 (12.3%) rostral facet joint violations were observed in the robot cohort and 75 (24.5%) in the navigation cohort (p=.01). Specifically, fewer robotic violations were observed at the L2 (3.5% vs 32.1%, p=.003) and L3 levels (3.9% vs 18.1%, p=.08) compared to navigation. No difference was observed at L4 and L5. Bilateral violations are significantly reduced with robotic approaches (5.3% vs 14.4%, p=.03). Lastly, more facet joint violations were observed during open approaches (robot: 18.8%, navigation: 27.3%) than percutaneous approaches (robot: 11.6%, navigation: 7.1%) in both groups (p<.001). The rate of L4 facet violations was 18.8% in the robotic cohort and 27.3% in the navigation cohort. The rate of L5 facet violations was 31.3% in the robotic cohort and 29.2% in the navigation cohort., Conclusions: Use of robotic assistance in lumbar pedicle screws significantly reduced the rate of rostral facet joint violations compared to navigation guidance at L2 and L3 levels, but not at L4 and L5, with facet violations approaching nearly one-third of the patients at L5 screws. Rostral facet violations can play a significant role in adjacent segment degeneration and disease. Technical factors and trajectory issues likely play a role and addressing these components should minimize unintended facet violation and proximal adding on., Competing Interests: Declaration of competing interest One or more of the authors declare financial or professional relationships on ICMJE-TSJ disclosure forms., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Purpose: The crankshaft phenomenon (CSP) is a corrective loss after posterior surgery for early onset scoliosis (EOS). However, an accurate method for CSP evaluation has yet to be developed. In this study, we evaluated pedicle screw (PS) length and rotation angle using an inverse trigonometric function and investigated the prevalence of the CSP., Methods: Fifty patients from nine institutions (mean age 10.6 years, male/female ratio 4:46) who underwent early definitive fusion surgery at ≤ 11 years of age were included. The rotation angle was calculated as arctan (lateral/frontal PS length) using radiography. Measurements were taken at the apex and lower instrumented vertebra (LIV) immediate, 2-, and 5-year postoperatively. CSP was defined as a rotation angle progression ≥ 5°. We divided patients into CSP and non-CSP groups and measured the demographic parameters, Risser grade, state of the triradiate cartilage, major coronal Cobb angle, T1-T12 length, T1-S1 length, and presence of distal adding-on (DAO). We compared these variables between groups and investigated the correlation between the measured variables and vertebral rotation. Logistic regression analysis investigated factors associated with CSP., Results: The rotation angle progressed by 2.4 and 1.3° over 5 years for the apex and LIV, respectively. CSP occurred in 15 cases (30%), DAO in 11 cases (22%), and CSP and DAO overlapped in 4 cases (8%). In the CSP group, the T1-T12 length was low immediate postoperatively. The rotation angle was negatively correlated with preoperative height (r = - 0.33), T1-T12 length (r = - 0.35), and T1-S1 length (r = - 0.30). A lower preoperative T1-T12 length was associated with CSP (odds ratio: 0.996, p = 0.048)., Conclusions: CSP occurred in 30% of patients with EOS who underwent definitive fusion. The presence of CSP was associated with a lower preoperative T1-T12 length., Level of Evidence: Diagnosis, level IV., (© 2024. The Author(s), under exclusive licence to Scoliosis Research Society.)

Purpose: Determine the effect of using the modified S-line vertebra (MSLV) as the upper instrumented vertebra (UIV) on postoperative trunk balance, L4 tilt, and clinical outcomes in selective thoracic fusion (STF) for adolescent idiopathic scoliosis (AIS) Lenke type 1C curve., Methods: Twenty-eight consecutive patients (all female; mean age: 15.4±2.0 years) with AIS Lenke type 1C curve were retrospectively enrolled. Primary outcome measures were coronal balance (absolute distance between C7 and the center of the sacral vertical line), L4 tilt, and Scoliosis Research Society (SRS)-22r scores at 2 years postoperatively. The group with the MSLV at the UIV was designated as the MSLV group (18 patients), and the group with the MSLV proximal (12 patients) or distal (4 patients) to the UIV was defined as the non-MSLV group., Results: We observed no significant differences between the groups regarding age, LIV and stable vertebra positioning, or preoperative X-ray parameters. Postoperative coronal balance was significantly better in the MSLV group (0.39±0.08 vs. 1.34±0.22 cm; P., (© 2024. The Author(s), under exclusive licence to Scoliosis Research Society.)

Purpose: The relationship between rod curvature and postoperative radiographic results is a debated topic. One of the reasons of the heterogeneity of the observed results might reside in the lack of a validated and widely employed method to measure the curvature of the rods. Aim of this study was to present and validate a novel method for rod measurement, which is based on routine X-rays and utilizes a regression algorithm that limits manual measurements and the related errors., Methods: Data from 20 adolescent idiopathic scoliosis/Scheuermann kyphosis (AIS/SK) patients and 35 adult spine deformity (ASD) patients for analysis, with 112 rods in total. An orthogonal reference grid was overlaid on the lateral X-ray; seven points were then marked along each rod and their coordinates recorded in a table. Using these coordinates, a third-order polynomial regression was applied to obtain the rod curvature equation (correlation coefficients > 0.97). Three observers (one surgeon, one experienced and one inexperienced observer) independently applied the developed method to measure the rod angulation of the included patients and performed the measurements twice. The reliability of the method was evaluated in terms of intraclass correlation coefficient (ICC), Bland-Altmann plot and 2S R ., Results: The intra-observer ICCs for all measurements exceed 0.85, indicating an excellent correlation. For the AIS/SK group, the surgeon showed a slightly lower reliability compared to the other two evaluators (0.93 vs 0.98 and 0.98). However, the surgeon showed a higher reliability in measurements of the rods at the lumbar level, both for L1-S1 and L4-S1 (0.98 vs 0.96 and 0.89; 0.97 vs. 0.85 and 0.91, respectively). The variability also showed excellent results, with a mean variability ranging from 1.09° to 3.76°. The inter-observer ICCs for the three measurement groups showed an excellent reliability for the AIS/SK group (0.98). The reliability was slightly lower but still excellent for the lumbar measurements in ASD patients at L1-S1 (0.89) and L4-S1 (0.83). The results of the 2S R for each measured segment were 4.4° for T5-T11, 5.4° for L1-S1 and 5.5° for L4-S1., Conclusion: The described method represents a reliable and reproducible way to measure rod curvature. This method is based on routine X-rays and utilizes a regression algorithm that limits manual measurements and the related errors., (© 2024. The Author(s), under exclusive licence to Scoliosis Research Society.)

Study Design: Observational epidemiological study., Objective: This study's primary objective was to examine the risk of recall for novel spine devices over time. Secondarily, we sought to analyze interbody fusion and vertebral body replacement (VBR) devices (corpectomy cages) as a risk factor for recall., Background: The recall risk of a novel spine device over time has not been reported. In addition, FDA regulations were lowered for interbody fusion devices to enter the market in 2007. As well, VBR implants were recently approved by the FDA for use in the cervical spine in 2015., Materials and Methods: Spine devices cleared between January 1, 2008 and December 31, 2018 were identified from the FDA's 510(k) database. All recall data were collected from the database in January 2021 to provide a 2-year minimum follow-up for a recall to occur. Product labels were used to classify interbody fusion and VBR devices. Cumulative incidence function was conducted to compare the overall risk of recall for FDA-cleared spine devices, and the hazard ratio determined for VBR and all other devices versus interbody implants during the study period., Results: A total of 2384 spine devices were cleared through 510(k) in the study period. The hazard of recall at 5 years was 5.3% (95% CI: 4.4%-6.2%) and 6.5% (95% CI: 5.4%-7.7%) at 10 years. No significant difference in recall risk was identified for interbody fusion and VBR devices., Conclusion: The risk of recall at 5 and 10 years of a novel spine device is about half the 12% rate reported for orthopedic devices in general. Despite lowered FDA regulations for interbody fusion devices and recent approval for VBR device use in the cervical spine, no increased risk of recall was detected. Further research is necessary to explain the reason for the lower risk of recall with spine devices., Level of Evidence: 4., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: Magnetically Controlled Growing Rod (MCGR) allows frequent outpatient rod lengthening when treating Early Onset Scoliosis (EOS) patients. But there is lack of expert consensus on the optimal MCGR lengthening interval. EOS 24-Item Questionnaire (EOSQ) is validated for assessing health-related quality of life (HrQOL), family burden, and satisfaction. This is the first study assessing how MCGR lengthening intervals affects patient-perceived outcomes., Methods: This is a multicentred cohort study with subjects recruited from 2012 to 2018 and followed till fusion. EOS subjects who underwent MCGR surgeries were grouped into high, medium or low lengthening interval subgroups based on 16 and 20 week cut-offs. Repeated measure analysis was performed on EOSQ's specified 12 domains. EOSQ results were taken: before index surgery, after index surgery, and prior to definitive treatment. Demographic, clinical and radiographic data were included in model adjustment., Results: 133 subjects with mean follow-up of 3.5 (± 1.3) years were included, with 60 males and 73 females; 45 idiopathic, 23 congenital, 38 neuromuscular, and 27 syndromic patients. Mean Cobb angle at surgery was 67° (± 22°) with mean age of 8.3 (± 2.5) years. Between groups, clinical and radiographic parameters were comparable. Higher EOSQ scores in medium lengthening interval subgroup was present in fatigue (p = 0.019), emotion (p = 0.001), and parental impact (p = 0.049) domains, and overall score (p = 0.046). Trendline contrast between subgroups were present in general health (p = 0.006) and physical function (p = 0.025) domains., Conclusion: Patient-perceived outcome improvements appear similar between lengthening interval subgroups. All MCGR lengthening intervals were tolerated by patients and family, with no negative impact observed., Level of Evidence: Prognostic Level III., (© 2024. The Author(s).)

Background: This study aimed to investigate the impact of three-dimensional (3D)-printed guide plate-assisted percutaneous pedicle screw implantation on minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) surgery., Methods: Overall, 162 patients who underwent MIS-TLIF at Tai'an City Central Hospital were retrospectively reviewed. The studied variables included operative time, volume of intraoperative blood loss, fluoroscopy time, postoperative drainage volume, visual analogue scale (VAS) score, Oswestry disability Index (ODI) score (preoperatively and at 2 weeks, 3 months, 6 months, and 12 months after surgery), and intervertebral fusion rate at 6 months after surgery., Results: The conventional group included 99 patients who underwent a conventional procedure, while the 3D printing group included 63 patients who underwent 3D-printed guide plate-assisted percutaneous pedicle screw implantation. The conventional group required more times of positioning needle punctures than the 3D printing group (22.2 ± 5.9 vs. 16.1 ± 4.9). The operation and fluoroscopy time were also longer in the former group (183.5 ± 51.1 min vs. 148.8 ± 40.3 min and 30.2 ± 5.9 s vs. 24.1 ± 4.9 s, respectively). In 3D printing group, lower back pain VAS scores and ODI scores at 2 weeks and 3 months after surgery were observed. There were no significant differences in terms of the volumes of intraoperative blood loss; postoperative lower limb pain VAS scores; and interbody fusion rate (P > 0.05)., Conclusion: The novel 3D-printed guide plate-assisted percutaneous pedicle screw implantation can achieve better amelioration of back pain and recovery of function. It also reduced the times of positioning needle puncture and fluoroscopy time during percutaneous screw placement surgery and reduced the duration of surgery., (© 2024. The Author(s).)

Background: The self-locking cage (ROI-C, LDR, Troyes, France) has been clinically applied in the treatment of cervical degenerative disc disease (CDDD). However, only a few long-term clinical and radiographic studies have been conducted on the treatment of spinal cord injury without fracture or dislocation (SCIWFD) so far. A comparison between ACDF with either ROI-C or CCP was performed to determine the better treatment for SCIWFD., Methods: A total of 83 patients who underwent ACDF using either ROI-C or CCP were reviewed for radiological and clinical outcomes. The cohort comprised 60 males and 23 females, aged between 32 and 88 years old, with an average age of 58.23 years. All patients exhibited symptoms of nerve injury, including limb numbness, muscle weakness, hypoesthesia or urinary dysfunction. The preoperative ASIA classification of spinal nerve function: 7 cases of grade A, 23 cases of grade B, 34 cases of grade C and 19 cases of grade D were included in the study., Results: A total of 48 patients underwent ACDF with ROI-C, while 35 patients received a conventional cage-plate. They were studied with a follow-up of 28.63 ± 17.41 months and 29.48 ± 15.43 months respectively. No significant difference was found in blood loss, JOA and ASIA between the two groups. No significant difference was found in cervical lordosis (CL) (P > 0.05). However, statistical difference was found in disc height of fused segment and T1 slope between the two groups (P < 0.05). No statistical difference was in the incidence of cage subsidence (P > 0.05). There was significant difference in the incidence of dysphagia. Both of two groups achieved bony fusion at final follow-up., Conclusion: Our study demonstrated that ROI-C has the same efficacy as CCP in improving the cervical stability in treatment of SCIWFD. The migration of cage didn't occur in ROI-C group at final follow-up, showing steadily fixed in cervical column. Moreover, the ROI-C does have the advantages of good therapeutic effect, mis-invasive, shorter operation time and fewer complications., (© 2024. The Author(s).)

Case: 43-year-old man with an adjacent segment C7-D1 left paracentral and foraminal disk and left-hand grip weakness underwent unilateral biportal endoscopic discectomy with O-arm navigation. The patient underwent C5-6 and C6-7 anterior cervical discectomy and fusion (ACDF) 10 years ago and was asymptomatic for nearly 10 years., Conclusion: In revision of the cervical spine with a short neck, cervicothoracic junctional disks can be precisely located using O-arm navigation and effectively removed with a minimally invasive unilateral biportal endoscopy approach., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSCC/C461)., (Copyright © 2024 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: Resecting the facet joint to relieve nerve pain can lead to spinal instability, deformity, and abnormal pressure on the anterior of the intravertebral disc. To mitigate these issues, surgeons often limit the amount of bone removed during facetectomy or stabilize the spine by fusion to maintain lumbar stability. This study aimed to assess how a M-PEEK rod system influenced the stability of the lumbar spine during graded facetectomy., Methods: Facetectomy was performed on a validated L1-L5 finite element model which was then simulated both with and without the M-PEEK rod system., Results: In extension, models implanted with M-PEEK in the interspinous space of L3/L4 experienced a 35.2% decrease in range of motion (ROM) at L3/L4, while others saw an 8.4-24.8% increase. For axial rotation, the ROM at L3/L4 increased by 2.2-5.4% in models with the M-Rod, and by 4.9-12.9% in models without the implant. In lateral flexion, the ROM at L3/L4 increased by 8.4-14.3% in models without a PEEK M-Rod (facetectomy only), with adjacent segments experiencing a 6.5% decrease in ROM in the implanted models. Overall, the difference in ROM between the intact and implanted models was minimal., Conclusions: Facetectomy involving the removal of 50% or more of the facet joint significantly increases range of motion and maximum intradiscal pressure, potentially accelerating disc degeneration, as shown in our finite element study. Stabilizing the segment with an M-PEEK rod may limit excessive motion, providing stability and maintaining intradiscal pressure closer to that of an intact model., (© 2024. The Author(s).)

Background: This study aims to evaluate the long-term outcomes of one-stage posterior hemivertebra resection and short segment fusion with pedicle screw fixation in children with thoracolumbar congenital early-onset scoliosis (TLCEOS). It specifically investigates the durability of spinal correction and the incidence of complications over an average follow-up of 8.97 years., Methods: A retrospective review was conducted on 32 patients treated at a tertiary scoliosis referral center from April 2003 to December 2019. Inclusion criteria were thoracolumbar hemivertebra (T11-L1), treatment via posterior hemivertebra resection and short segment fusion (≤ 5 segments), age under 10 years at surgery, and a follow-up of at least 5 years. Exclusions included idiopathic, syndromic, or neuromuscular scoliosis. Data on demographics, surgical procedures, and radiographic outcomes were collected, and clinical outcomes were evaluated using the Scoliosis Research Society-22 (SRS-22) questionnaire. Statistical analysis was performed using SPSS and R software., Results: The study included 32 patients (22 males, 10 females) with a mean age of 5.00 ± 2.42 years at surgery and an average follow-up of 8.97 ± 2.81 years. On average, 3.47 ± 1.11 segments were fused. The main curve corrected from 38.64° ± 14.12° preoperatively to 9.06° ± 7.29° postoperatively, with a final correction rate of 61%. Significant improvements were observed in the SRS-22 domains of Appearance and Satisfaction with Treatment. There were 17 complications, including neurological, pulmonary, and mechanical issues, with some cases requiring revision surgery., Conclusions: One-stage posterior hemivertebra resection and short segment fusion with pedicle screw fixation effectively correct TLCEOS long-term, offering significant improvements in patient appearance and satisfaction, with a manageable complication profile., (© 2024. The Author(s).)

Background: To establish a three-dimensional finite element model of the lumbar spine and investigate the impact of different fixation techniques on the biomechanical characteristics of oblique lumbar interbody fusion (OLIF)., Methods: The study aimed to establish and validate a comprehensive three-dimensional model of the lower lumbar spine (L3-S1) using the finite element method. L4-L5 was selected as the surgical segment, and four distinct OLIF surgical models were constructed: Stand-alone (SA), unilateral cortical bone trajectory screw (UCBT), bilateral cortical bone trajectory screw (BCBT), and bilateral pedicle screw (BPS). The models were underwent a pure moment of 10N·m to simulate lumbar extension, flexion, left bending, right bending, left and right rotation movements. Subsequently, the range of motion (ROM), cage stress, and fixation stress were calculated., Results: In the L3-L5 segment, the BCBT group showed the most limited range of motion (ROM) under exercise load, indicating superior stability within this group. The ROM and cage stress values were found to be highest in the SA group. In contrast, the cage and internal fixation stress in the BPS group were observed to be lowest (9.91 ~ 53.83MPa, 44.93 ~ 84.85 MPa). With the exception of right bending and right rotation, the UCBT group demonstrated higher levels of internal fixation stress (102.20 ~ 164.62 MPa)., Conclusions: The study found that OLIF-assisted internal fixation improved segmental stability and reduced cage stress. The BPS group had advantages over the CBT group in preventing endplate damage and reducing the risk of cage subsidence. However, BCBT group has distinct merits in maintaining surgical segment stability, distributing stress load on the spinal motor unit, and reducing the likelihood of adjacent segment degeneration (ASD)., (© 2024. The Author(s).)

Background: To study the risk factors associated with misplacement of freehand pedicle screws through a posterior approach for degenerative scoliosis., Methods: A total of 204 patients who underwent posterior pedicle screw-rod system surgery for degenerative scoliosis in our hospital from December 2020 to December 2023 were retrospectively analyzed. Patient demographics, radiographic accuracy, and surgery-related information were recorded., Results: A total of 204 patients were included. A total of 2496 screws were placed. 2373 (95.07%) were in good position. Misplacement screws were 123 (4.93%). None of the patients had postoperative spinal nerve symptoms due to screw malposition. The misplacement rate of thoracic (T10-T12) pedicle screws was 11.11% (60/540). Misplacement of pedicle screws in the lumbar spine (L1-L5) was 3.22% (63/1956). Age, gender, surgeon, and operation time had no significant effect on misplacement of pedicle screws (P>0.05). Body mass index, Hu value, number of screw segments, Cobb angle, vertebral rotation, and spinal canal morphology had some correlation with pedicle screw misplacement. Among them, BMI, Hu value, number of screw segments, Cobb angle, and vertebral rotation grade were independent risk factors for PS misplacement (P<0.05). The height of the posterior superior iliac spine had a significant effect on pedicle screw misplacement in the lower lumbar spine (L4/5) (P<0.05)., Conclusion: BMI, Hu value, number of screw levels, Cobb angle, and vertebral rotation grade were independent risk factors for pedicle screw misplacement in patients with degenerative scoliosis. Posterior superior iliac spine height has a large impact on PS placement in the lower lumbar spine. Patients with degenerative scoliosis should be preoperatively planned for the size and direction of the placed screws by X-ray and CT three-dimensional, to reduce the misplacement rate of pedicle screws., (© 2024. The Author(s).)

Study Design: Retrospective cohort study., Objective: The purpose of this study was to investigate the rate of cervical total disc replacement (TDR) device removal or revision., Background: Cervical TDR has gained acceptance as an alternative to anterior cervical discectomy and fusion in appropriately selected patients. There have been concerns over device safety, one measure of which is subsequent surgery related to device problems., Patients and Methods: A consecutive series of 1626 patients undergoing cervical TDR from 2003 to June 2021 were included, consisting of TDRs up to 3 levels and hybrids (TDR and fusion). TDR removal or revision surgeries and reasons for these surgeries, procedures performed, and duration from index procedure were recorded. Data were analyzed to determine the removal/revision rate and factors possibly related to these events., Results: There were 24 removals/revisions (1.48%) in the 1626 patients. Removal was performed in 23 cases (1.41%) and revision in 1 (0.06%). Among removal cases, anterior cervical discectomy and fusion was performed in 18 and TDR was replaced with another TDR in 5. Removals with fusion included 5 cases of osteolysis with/without Cutibacterium acnes , 4 device displacement/migration, 4 posterior spinal pathology, and one for each of the following: metal allergy, approach-related complications, malpositioning, subsidence, and hypermobility. The revision involved TDR repositioning 3 days after index surgery. There were 66 patients for whom a minimum of 10-year follow-up was confirmed, and none had removal/revision surgery 10 or more years after index surgery. There was no relationship between the occurrence of removal/revision and age, sex, body mass index, or physician experience (learning curve). The removal/revision rate was significantly higher in FDA trials versus postapproval (4.1% vs . 1.3%, P < 0.05)., Conclusion: In this large consecutive series of patients, 1.48% of cervical TDRs were removed/revised. The low rate of removals/revisions over a long period of time provides support for the devices' safety., Level of Evidence: Level IV., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Pedicle screw loosening after posterior lumbar fusion is associated with poor bone quality, which often determines screw pull-out strength, insertion torque, and vertebral body loading characteristics. Magnetic resonance imaging (MRI)-based vertebral bone quality (VBQ) score were associated with poor bone quality. Current evidence suggests that pedicle bone quality (PBQ) has a greater impact on screw stability. However, the correlation between MRI-based PBQ score and screw loosening has not been reported., Purpose: To introduce and evaluate an MRI-based PBQ score to determine its effectiveness in predicting pedicle screw loosening following lumbar fusion surgery., Methods: The retrospective study analyzed 244 patients who underwent posterior lumbar interbody fusion (PLIF) with pedicle screws between December 2017 and December 2021, with CT and MRI imaging before surgery. Data collected included patient demographics and preoperative radiological data. Radiographic screw loosening was measured at 12 months postoperatively. Clinical assessments included pain visual analog scale (VAS) and Oswestry Disability Index (ODI) scores. The PBQ score was measured using MRI scans. We use univariate analysis for preliminary screening of the risk factors of screw loosening. Subsequent analysis involved multivariate logistic regression to identify independent predictive factors for screw loosening. We constructed the receiver operating characteristic (ROC) curve to ascertain the discriminative capacity of the PBQ score. The area under the curve (AUC) quantified its predictive accuracy. Additionally, we evaluated the association between PBQ score and screw loosening using Spearman's correlation analysis., Results: Overall, 244 patients who underwent PLIF with pedicle screw fixation participated in this study, including 35 in the loosening group and 209 in the non-loosening group. PBQ score in the loosening group was significantly higher than that in the non-loosening group. On multivariate logistic regression, the higher PBQ score (OR = 8.481, 95% CI: 3.158-22.774; p < 0.001) and the lower mean Hounsfield unit (HU) value of L1-4 (OR = 0.967, 95% CI 0.951-0.984; p < 0.001) were the variables that significantly predicted screw loosening. The AUC for the PBQ score and HU value were 0.751 (95% CI: 0.673-0.828) and 0.702 (95% CI: 0.612-0.791). The PBQ score optimal cutoff to differentiate patients with loosening and with non-loosening was calculated as 3.045 with a sensitivity of 85.7% and specificity of 76.9%, while the optimal cutoff of the HU value was 151.5 with a sensitivity of 64.6% and specificity of 89.5%., Conclusions: The association between the PBQ score and the propensity for lumbar pedicle screw loosening was found to be substantial. As a predictive measure, the PBQ score outperformed the HU value in forecasting the likelihood of screw loosening post-posterior lumbar fusion., (© 2024 The Author(s). Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Objective: The unclear clinical outcomes of two different zero-profile implants with different number of screws in hybrid surgery restricts the choice of patient-specific implants. This study aims to compare two different implants on its postoperative subsidence, motion stabilization and clinical outcomes. It also provides references to the most reasonable implant choice in fusion surgery., Methods: This was a retrospective study. From February 2014 to March 2022, 173 patients who underwent hybrid surgery were included. Among them, 122 received surgery with a four screw implant, while 51 received a two screw implant. We analyzed the significance of patient-specific factors, radiographic factors and clinical outcomes. The Wilcoxon rank sum test, t tests/analysis of variance (ANOVA) test and stepwise multivariate logistic regression were adopted for statistical analysis., Results: No statistically significant difference was observed between the two screw and four screw groups in terms of immediate, middle, and long-term stability and fusion rate (p > 0.05). However, the two screws group had higher FSU height subsidence at 3, 6, and 12 months postoperatively and higher rates of significant subsidence at three and 6 months postoperatively (p < 0.05). Both groups showed significant clinical improvements at the final follow-up., Conclusion: Two screw and four screw implants provide comparable stability, fusion rates and clinical outcomes. However, the two screw implant was inferior to the four screw implant in subsidence prevention. Therefore, the two-screw implant is non-inferior to the four-screw implant in most patients. It can be used as the priority choice in the fusion segment by its easy manageability. However, the patients with a high risk of subsidence such as multilevel surgery, the elderly, lower BMD, bad cervical alignment should receive a four screw implant rather than a two screw implant., (© 2024 The Author(s). Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Objective: To compare the safety, clinical outcomes, and radiological results of anterior cervical discectomy and fusion (ACDF) with zero-profile anchored spacer (ZPAS) versus plate and cage (PC) for 3-level contiguous cervical degenerative disease., Methods: The study was registered at PROSPERO (CRD42024512706). The Web of Science core collection, PubMed, and Embase were searched up to February 12, 2024. Review Manager 5.3 was used. The relative risk (RR) and 95% confidence interval were evaluated for dichotomous data. Continuous data were assessed using the mean difference and 95% confidence interval., Results: Nine studies comparing ACDF with ZPAS versus PC for 3-level contiguous cervical degenerative disease were included. The intraoperative blood loss and operation time in ZPAS were significantly less than those in PC. The subsidence rate, loss of cervical alignment, fusion segmental height, and intervertebral disc height were significantly greater in ZPAS than in PC. The cervical alignment and dysphagia rate within 6 months were significantly lower in ZPAS than in PC. The ASD of ZPAS was significantly lower than that of PC according to the sensitivity analysis when 1 study was excluded. No significant differences were identified in the other aspects., Conclusions: Both ACDF with ZPAS and PC were safe and effective procedures. PC was associated with increased surgical trauma. The ZPAS could better decrease the incidence of ASD and dysphagia. ZPAS was also accompanied by high subsidence rate and poor cervical alignment., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background Context: Cage subsidence is a common complication after lumbar interbody fusion surgery, with low bone mineral density (BMD) being a significant risk factor. Endplate bone quality (EBQ) obtained from clinical MRI scans has been deemed reliable in determining regional BMD. However, the association between EBQ score and cage subsidence following oblique lumbar interbody fusion (OLIF) has not been clearly established., Purpose: This study aims to assess the relationship between EBQ score and cage subsidence in patients who underwent single-level OLIF., Study Design/setting: A retrospective study., Patient Sample: The study included adults with degenerative spinal conditions who underwent single-level OLIF at our institution., Outcome Measures: Cage subsidence, disc height, EBQ score, fusion rate., Methods: This retrospective study analyzed data from patients who underwent single-level OLIF surgery at our institution between October 2017 and August 2022. Postoperative CT scans were used to measure cage subsidence, while the EBQ score was calculated using preoperative noncontrast T1-weighted MRI. To determine the predictive ability of the EBQ score, receiver operating characteristic (ROC) curve analysis was conducted. Additionally, univariable and multivariable logistic regression analyses were performed., Results: In this study, a total of 88 patients were included and followed up for an average of 15.8 months. It was observed that 32.9% (n=29/88) of the patients experienced cage subsidence. The postsurgery disc height was significantly higher in patients who experienced subsidence compared to those who did not. The mean EBQ scores for patients with nonsubsidence and subsidence were 2.31±0.6 and 3.48±1.2, respectively, and this difference was statistically significant. The ROC curve analysis showed that the AUC for the EBQ score was 0.811 (95% CI: 0.717-0.905). The most suitable threshold for the EBQ score was determined to be 2.318 (sensitivity: 93.1%, specificity: 55.9%). Additionally, the multivariate logistic regression analysis revealed a significant association between a higher EBQ score and an increased risk of subsidence (odds ratio [OR]=6.204, 95% CI=2.520-15.272, p<.001)., Conclusions: Our findings indicate that higher preoperative EBQ scores are significantly linked to cage subsidence following single-level OLIF. Preoperative measurement of MRI can serve as a valuable tool in predicting cage subsidence., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Background: Lumbar spondylolysis (LS) poses a potential threat, and there is a need to evaluate and compare the effectiveness of direct pars repair techniques., Objective: To assess and compare the clinical and radiographic outcomes of direct pars repair techniques using the pedicle screw hook system (PSHS) and the pedicle screw rod system (PSRS) in young symptomatic patients with lumbar spondylolysis., Methods: A retrospective study was conducted to compare clinical and radiological data in young symptomatic LS patients after surgery. Records of 45 post-surgery LS patients with a minimum 24-month follow-up (January 2014 to June 2019) were reviewed. A total of 26 patients underwent PSHS, and 19 had PSRS. Treatment outcomes were analyzed using the visual analog pain scale (VAS), Oswestry disability index (ODI), MacNab criteria, lumbar fusion status, and Pfirrmann grading standards. Patient baseline characteristics were also compared between the two groups., Results: No disc degeneration was observed in either PSHS or PSRS groups at 24 months postoperatively, according to the Pfirrmann grading scale. The PSRS group outperformed the PSHS group in operative time, intraoperative blood loss, postoperative drainage, length of hospital stays, ODI, VAS values at 3 months postoperatively, and fusion status at 6 months postoperatively. No notable differences were observed in other parameters during the 24-month follow-up period, and no significant surgical complications were recorded., Conclusions: Direct pars repair techniques using PSHS and PSRS yielded satisfactory clinical and radiographic results in young patients with symptomatic LS. PSRS, compared to PSHS, demonstrated greater effectiveness in young individuals with LS and promoted early recovery.

Background: Motion-sparing scoliosis surgeries such as the posterior dynamic distraction device (PDDD) are slowly increasing in use. However, there is limited clinical data documenting postoperative motion across the PDDD construct. With this cohort study, we aim to measure sagittal and coronal motion following PDDD. We hypothesize coronal and sagittal spinal motion will be partially preserved across the construct., Methods: Retrospective review of prospectively collected data. Preoperative and minimum 1-year postoperative coronal range of motion across the instrumented levels was compared. Available flexion/extension radiographs were evaluated postoperatively to assess sagittal arc of motion. Radiographs from latest follow-up were used., Results: At a mean of 1.9 years (1 to 5 y), flexibility radiographs were available on 29 patients treated with PDDD (17 thoracic, 12 lumbar). Mean age at surgery was 16 years (12 to 25). Postoperative coronal arc of motion in PDDD patients was 11 degrees (3 to 19 degrees) in the thoracic spine and 10 degrees (0 to 28 degrees) in the lumbar spine. Compared with preoperative motion, the thoracic arc of motion was maintained by 33% (35 to 11 degrees) and lumbar motion was maintained by 30% (34 to 10 degrees). Flexion-extension radiographs were available on 7 patients. Sagittal arc for the upper instrumented vertebral end plate to the lower instrumented vertebral endplate of the cohort was 10 degrees in the thoracic spine (6 to 18) and 14 degrees in the lumbar spine (5 to 21). Sagittal measurements for the changes in the arc of the upper and lower screws on the construct were 4 degrees in the thoracic group (2 to 8) and 9 degrees in the lumbar group (2 to 17). By latest follow-up 11 patients (38%) underwent reoperation, with most cases due to implant breakage (N=4, 14%), extender misalignment (N=2, 7%), and screw misplacement (N=2, 7%)., Conclusion: At mean 1.9 years postoperatively, PDDD preserves measurable spinal motion over the construct both in the coronal and the sagittal plane without evidence for autofusion. Coronal arc of motion averages 10 to 12 degrees and sagittal arc of motion ranged from 4 to 14 degrees, although this varies by patient. This study confirms that PDDD for pediatric scoliosis preserves a measurable degree of postoperative flexibility both in the sagittal and coronal planes., Level of Evidence: Level II-therapeutic study., Competing Interests: A.N.L. is a consultant for ZimVie, Orthopediatrics, DePuy Synthes, Medtronic, and Pacira with all funds directed to Mayo Clinic. A.N.L. and Mayo Clinic receive royalties from Globus. T.A.M. is a consultant to Medtronic with all funds directed to Mayo Clinic. Mayo Clinic has received research funding from Orthopediatrics and Medtronic. M.A. is a consultant for Orthopediatrics and receives royalties from OrthoPediatrics. R.E.-H. has received grants/research support from Depuy Synthes, Medtronic, Orthopediatrics, and ZimVie. R.E.-H. is a consultant for Depuy Synthes, Medtronic, and Orthopediatrics. R.E.-H. is a shareholder for Orthopediatrics, and is on the advisory board or panel for Orthopediatrics, Scoliosis Research Society, and Pediatric Spine Foundation. G.H. is a consultant for Orthopediatrics. Sanford Health has received research funding from Orthopediatrics. The remaining authors declare no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: We defined sagittal S-line tilt (SSLT) as the tilt of the line connecting the upper instrumented vertebra and the lower instrumented vertebra. This study aimed to: (1) examine the correlation between SSLT and proximal junctional angle (PJA) change values, and (2) determine the cut-off value of SSLT with respect to proximal junctional kyphosis (PJK) occurrence., Methods: Eighty-six consecutive patients (81 female and 5 male; mean age: 15.8 years) with Lenke 5C AIS who underwent posterior selective spinal fusion. Pearson's correlation coefficients were used to examine the relationship between preoperative SSLT and changes in PJA from preoperative to 2 years postoperative. The impact of SSLT on PJK at 2 years after surgery was assessed using a receiver operating characteristic (ROC) curve., Results: We observed a moderate positive correlation between preoperative SSLT and change in PJA (R = 0.541, P < 0.001). We identified 18 patients (21%) with PJK at 2 years postoperative. Mean preoperative SSLT in the PJK group and the non-PJK group differed significantly at 23.3 ± 4.1° and 16.1 ± 5.0°, respectively (P < 0.001). The cut-off value of preoperative SSLT for PJK at 2 years postoperative was 18° in ROC curve analysis, with a sensitivity of 94%, specificity of 68%, and area under the ROC curve of 0.868., Conclusion: In selective lumbar fusion for AIS Lenke type 5C curves, preoperative SSLT was significantly correlated with PJA change from preoperative to 2 years postoperative. SSLT was a predictor of PJK occurrence, with a cut-off value of 18°., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: Oblique lumbar interbody fusion (OLIF) has become a popular technique for treating adult degenerative scoliosis (ADS), but traditional OLIF technology often requires repositioning for one-stage or staged posterior fixation. The objective of this pilot study was to describe the surgical technique of simultaneous single-position OLIF and percutaneous pedicle screw fixation (OLIF 360) under O-Arm navigation for modified MISDEF type II ADS., Methods: Between June 2022 and December 2023, six patients classified as having modified MISDEF type II ADS underwent OLIF 360 assisted by O-Arm navigation at our institution. Intraoperative blood loss, duration of operation, and complications related to the OLIF 360 procedure were recorded. The preoperative and postoperative spinal pelvic parameters were measured using X-rays. The accuracy of pedicel screws was recorded in accordance with the modified Gertzbein-Robbins classification on CT. Postoperative MRI was performed to evaluate the indirect decompressive effect. The Japanese Orthopedic Association score for low back pain was used to evaluate surgical outcomes., Results: Navigated OLIF 360 were performed in six ADS patients with 44 percutaneous pedicel screws and 16 cages placement, including four women and two men. The mean operation time was 160.83 ± 33.23 min, and the mean blood loss was 111.67 ± 39.71 mL. Postoperative spinal pelvic parameters and spinal stenosis degree improved significantly on X-ray and MRI. All screws were clinically acceptable according to the Gertzbein-Robbins classification, with 92.7% grade A and 7.3% grade B. No serious intraoperative and postoperative adverse events were recorded in all patients. The JOA scores for low back pain of all patients were significantly improved at postoperative 1 month and the final follow-up., Conclusion: We report on a case series and describe navigated OLIF 360 in treating modified MISDEF type II ADS patients. Navigation-assisted OLIF 360 has shown encouraging surgical outcomes with good spinal imbalance correction and indirect decompression., (© 2024 The Author(s). Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Objective: To investigate the biomechanical properties of pedicle screw reinsertion along the same trajectory in a previously validated synthetic bone model., Methods: Twenty identical acrylonitrile butadiene styrene models of lumbar vertebrae were three-dimensional-printed. Screws were placed in the standard fashion into each pedicle. Models were separated into 2 equal groups, control and experimental. Experimental group screws were completely removed from their testing block and reinserted once. All screws in both groups were then forcibly removed. Continuous torque monitoring was collected on screw insertion torque (IT), removal torque, and reinsertion torque. Pullout strength (PO), screw stiffness (STI), and strain energy (STR) were calculated., Results: There was no significant difference between control and experimental groups for PO (P = 0.26), STI (P = 0.55), STR (P = 0.50), or IT (P = 0.24). There was a significant decrease in reinsertion torque (54.5 N-cm ± 8.2 N-cm) from control IT (62.9 N-cm ± 8.4 N-cm, P = 0.045) and experimental IT (67.5 N-cm ± 7.6 N-cm, P = 0.0026). Strong correlations (Pearson's r > 0.80) were seen between control IT against STR and PO, between each of the experimental torque measurements, and between experimental PO and STI., Conclusions: Despite a significant decrease in insertion torque, there is no significant loss of pedicle screw performance when a screw is removed and reinserted along the same trajectory., (Copyright © 2024. Published by Elsevier Inc.)

Background Context: Clinical trials have demonstrated that cervical disc arthroplasty (CDA) is an effective and safe alternative treatment to anterior cervical discectomy and fusion (ACDF) for cervical degenerative disc disease in the appropriately indicated patient population. Various devices for CDA exist, differing in the level of device constraint., Purpose: To investigate outcomes following Anterior Cervical Discectomy and Fusion (ACDF) versus CDA stratified based on the level of device constraint: Constrained, Semiconstrained, and Unconstrained., Study Design: Systematic review and network meta-analysis., Patient Sample: A total of 2,932 CDA patients (979 Constrained, 1,214 Semiconstrained, 739 Unconstrained) and 2,601 ACDF patients from 41 studies that compared outcomes of patients undergoing CDA or ACDF at a single level at a minimum of 2 years follow-up., Outcome Measures: Outcomes of interest included the development of adjacent segment degeneration (ASD), index and adjacent segment reoperation rates, range of motion (ROM), high-grade heterotopic ossification (HO, McAfee Grades 3/4), and patient-reported outcomes (NDI/VAS)., Methods: CDA devices were grouped based on the degrees of freedom (DoF) allowed by the device, as either Constrained (3 DoF), Semiconstrained (4 or 5 DoF), or Unconstrained (6 DoF). A random effects network meta-analysis was conducted using standardized mean differences (SMD) and log relative risk (RR) were used to analyze continuous and categorical data, respectively., Results: Semiconstrained (p=.03) and Unconstrained CDA (p=.01) demonstrated a significantly lower risk for ASD than ACDF. All levels of CDA constraint demonstrated a significantly lower risk for subsequent adjacent segment surgery than ACDF (p<.001). Semiconstrained CDA also demonstrated a significantly lower risk for index level reoperation than both ACDF and Constrained CDA (p<.001). Unconstrained devices retained significantly greater ROM than both Constrained and Semiconstrained CDA (p<.001). As expected, all levels of device constraint retained significantly greater ROM than ACDF (p<.001). Constrained and Unconstrained devices both demonstrated significantly lower levels of disability on NDI than ACDF (p=.02). All levels of device constraint demonstrated significantly less neck pain than ACDF (p<.05), while Unconstrained CDA had significantly less arm pain than ACDF (p=.02) at final follow-up greater than 2 years., Conclusion: CDA, particularly the unconstrained and semiconstrained designs, appears to be more effective than ACDF in reducing the risk of adjacent segment degeneration and the need for further surgeries, while also allowing for greater range of motion and better patient-reported outcomes. Less constrained CDA conferred a lower risk for index level reoperation, while also retaining more range of motion than more constrained devices., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Navigated pedicle screw placement can be particularly challenging for cervical and upper thoracic levels in obese patients. This technical challenge can be compounded by smaller-diameter tools, which can be flexible and therefore confound navigation. It is imperative to avoid excessive manipulation of surrounding tissues to maintain navigation accuracy in the mobile cervical spine. 1 Robotic-assisted spinal approaches use firm guides to aid drilling and screw placement but are hindered by high costs with equipment acquisition. 2 , 3 Here, we propose a technical nuance that combines robotic surgical principles with tools that are more readily available in many surgical departments (Video 1). We present the case of a 64-year-old woman with a chief complaint of neck pain, irradiating to the left worse than right arm and prior history of C5-7 anterior cervical diskectomy and fusion. Imaging showed multilevel degenerative disease and a solid prior C5-7 anterior cervical diskectomy and fusion with grade I anterolisthesis at C7-T1 due to severe facet degeneration with severe left-sided foraminal stenosis. Given failure of conservative management, the patient was brought to the operating room for left C7-T1 foraminotomy and C7-T1 posterior instrumented fusion. Here, we show the use of a tubular retractor fixed to the surgical bed for solid and reproducible trajectory for all tools to minimize the risk of surrounding tissue manipulation and its effect on navigation accuracy., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Study Design: A multicenter randomized controlled noninferiority trial with intrapatient comparisons., Objective: The aim of this study was to determine noninferiority of a slowly resorbable biphasic calcium phosphate with submicron microporosity (BCP<μm, MagnetOs Granules) as an alternative for autograft in instrumented posterolateral fusion (PLF)., Summary of Background Data: Successful spinal fusion with a solid bone bridge between the vertebrae is traditionally achieved by grafting with autologous iliac bone. However, the disadvantages of autografts and unsatisfactory fusion rates have prompted the exploration of alternatives, including ceramics. Nevertheless, clinical evidence for the standalone use of these materials is limited., Methods: Adults indicated for instrumented PLF (1 to 6 levels) were enrolled at 5 participating centers. After bilateral instrumentation and fusion-bed preparation, the randomized allocation side (left or right) was disclosed. Per segment 10 cc of BCP<μm granules (1 to 2 mm) were placed in the posterolateral gutter on one side and 10 cc autograft on the contralateral side. Fusion was systematically scored on 1-year follow-up CT scans. The study was powered to detect >15% inferiority with binomial paired comparisons of the fusion performance score per treatment side., Results: Of the 100 patients (57 ± 12.9 y, 62% female), 91 subjects and 128 segments were analyzed. The overall posterolateral fusion rate per segment (left and/or right) was 83%. For the BCP<μm side only the fusion rate was 79% versus 47% for the autograft side (difference of 32 percentage points, 95% CI, 23-41). Analysis of the primary outcome confirmed the noninferiority of BCP<μm with an absolute difference in paired proportions of 39.6% (95% CI, 26.8-51.2; p < 0.001)., Conclusion: This clinical trial demonstrates noninferiority and indicates superiority of MagnetOs Granules as a standalone ceramic when compared to autograft for posterolateral spinal fusion. These results challange the belief that autologous bone is the most optimal graft material., Competing Interests: The authors report no conflicts of interest, (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.)

Purpose: Cervical hemivertebrae (C3-6) causing significant osseous torticollis, head tilt and facial asymmetry are rare and complicated. Cervical hemivertebrectomy (CHVE) by a posterior-only approach was never reported because it is highly risky and its efficacy remains controversial. This study is to evaluate the feasibility and preliminary clinical outcomes of posterior-only approach for CHVE and torticollis correction in young children., Methods: Four young children aged 5-9 years old with significant torticollis caused by cervical hemivertebrae underwent deformity correction consisting of cervical pedicle screw (CPS) placement with O-arm-based intraoperative navigation, CHVE using ultrasonic bone scalpel and short-segmental posterior instrumentation and fusion. Details of this novel technique were presented. The preliminary short-term clinical and radiographic outcomes were assessed., Results: On average, the operative time was 312.5 ± 49.9 min, and the surgical blood loss was 375.0 ± 150.0 ml. The structural cervical scoliosis was corrected from 31.5 ± 7.3° to 11.0 ± 4.1°, and the average correction rate was 64.9%. Head tilt was favorably corrected from 11.0 ± 4.2° to 3.5 ± 2.6°. The shoulder balance improved from 6.3 ± 1.3° to 1.5 ± 1.9°. One case with C6 CHVE had convex side radiating nerve root pain but no sign of muscle power weakness. Full recovery was achieved one month after surgery. No other complication occurred., Conclusions: CHVE by a posterior-only approach was a feasible alternative option for the treatment of congenital cervical scoliosis. It could resect the CHV effectively and achieve satisfactory torticollis correction without additional anterior access surgery. Successful CPS placement in this child population was essentially important to enable reliable osteotomy closure and firm posterior instrumentation., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background Context: Establishing good screw-bone structural stability is conducive to reducing the risk of postoperative screw loosening. Screw insertion torque is an objective index for evaluating screw-bone structural stability. Therefore, accurate prediction of screw insertion torque can improve the preoperative evaluation of patients, optimize the surgical plan, and improve the surgical effect. At present, the correlation between different bone assessment methods and screw insertion torque is unclear., Purpose: The aim of this study was to evaluate the correlation between different bone assessment methods and screw insertion torque and to optimize the predictive performance of screw insertion torque through mathematical modeling combined with different radiology methods., Design: Prospective cross-sectional study., Patient Samples: Seventy-seven patients with preoperatively available DXA, CT and MRI data who underwent spinal fixation surgeries between October 2022 and September 2023 and 357 sets of screw data were included in this analysis., Outcome Measures: Spinal, vertebrae-specific and screw trajectory's BMD were measured preoperatively by different imaging modalities. Intraoperative screw insertion torque was measured using an electronic torque wrench., Methods: Pearson linear correlation, scatter plots and univariate linear regression were used to evaluate the correlation between different bone evaluation methods and screw insertion torque. Different bone evaluation methods were fitted into the prediction model of screw torque and the related equations were obtained., Results: Screw insertion torque had the strongest positive correlation with the volumetric bone mineral density (vBMD) of the screw trajectory (Pedicle screw insertion torque (PSIT): R = 0.618, p<.001; Terminal screw insertion torque (TSIT): R = 0.735, p<.001). A weak negative correlation was found between the screw insertion torque and level specific vertebral bone quality (VBQ) (PSIT: R = -0.178, p=.001; TSIT: R = -0.147, p=.006). We also found that the PSIT was strongly correlated with the TSIT (R = 0.812, p<.001)., Conclusions: Compared to other bone quality assessment methods, screw trajectory vBMD may be better predict the magnitude of screw insertion torque. In addition, we further optimized preoperative assessments by constructing a mathematical model to better predict screw insertion torque. In conclusion, clinicians should select appropriate preoperative bone quality assessment methods, identify potential low-torque patients, optimize surgical plans, and ultimately improve screw insertion accuracy and reduce postoperative screw loosening rate., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Objective: To compare the stability of a corticopedicular posterior fixation (CPPF) device with traditional pedicle screws for decompression and fusion in adult degenerative lumbar spondylolisthesis., Methods: Finite element analysis (FEA) was used in a validated model of grade 1 L4-L5 spondylolisthesis to compare segmental stability after laminectomy alone, laminectomy with pedicle screw fixation, or laminectomy with CPPF device fixation. A 500-N follower load was applied to the model and different functional movements were simulated by applying a 7.5-Nm force in different directions. Outcomes included degrees of motion, tensile forces experienced in the CPPF device, and stresses in surrounding cortical bone., Results: At maximum loading, laminectomy alone demonstrated a 1 ° increase in flexion range of motion, from 6.35 ° to 7.39 ° . Laminectomy with pedicle screw fixation and CPPF device fixation both reduced spinal segmental motion to ≤1 ° at maximum loading in all ranges of motion, including flexion (0.94 ° and 1.09 ° ), extension (-0.85 ° and -1.08 ° ), lateral bending (-0.56 ° and -0.96 ° ), and torsion (0.63 ° and 0.91 ° ), respectively. There was no significant difference in segmental stability between pedicle screw fixation and CPPF device fixation during maximum loading, with a difference of ≤0.4 ° in any range of motion. Tensile forces in the CPPF device remained ≤51% the ultimate load to failure (487 N) and stress in surrounding cortical bone remained ≤84% the ultimate stress of cortical bone (125.4 MPa) during maximum loading., Conclusions: CPFF fixation demonstrated similar segmental stability to traditional pedicle screw fixation whereas tensile forces and stress in surrounding cortical bone remained below the load to failure., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Study Design: A systematic review and meta-analysis., Objective: This study aims to compare pedicle screw accuracy, clinical outcomes, and complications between navigated and conventional techniques., Summary of Background Data: In the last decades, intraoperative navigation has been introduced in spinal surgery to prevent risks and complications., Materials and Methods: The search was executed on Cochrane Central Library, PubMed, and Scopus on April 30, 2023. Randomized controlled trials, prospective and retrospective studies that compared pedicle screw accuracy in the thoracic-lumbar-sacral segments, blood loss, operative time, hospital stay, intraoperative and postoperative revision of screws, neurological and systemic complications, Visual Analogue Scale (VAS), and Oswestry Disability Index (ODI) between navigated and freehand or fluoroscopy-assisted techniques were included in this study. The meta-analysis was performed using Review Manager software. Clinical outcomes were assessed as continuous outcomes with mean difference, while pedicle screw accuracy and complications were assessed as dichotomous outcomes with odds ratio, all with 95% CIs. The statistical significance of the results was fixed at P <0.05., Results: This meta-analysis included 30 studies for a total of 17,911 patients and 24,600 pedicle screws. Statistically significant results in favor of the navigated technique were observed for the accuracy of pedicle screws ( P =0.0001), hospital stay ( P =0.0002), blood loss ( P <0.0001), postoperative revision of pedicle screws ( P <0.00001), and systemic complications ( P =0.0008). In particular, the positioning of the screws was clinically acceptable in 96.2% of the navigated group and 94.2% with traditional techniques. No significant differences were found in VAS, ODI, and operative time between the two groups., Conclusion: Navigated pedicle screw fixation has been demonstrated to be a safe and effective technique with high improvement in clinical outcomes and accuracy in patients undergoing spinal fusion compared with conventional techniques., Level of Evidence: Level III., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.)