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Study Design: Cohort study., Objective: Our goal was to verify the validity of the global alignment and proportion (GAP) score, SRS-Schwab, and Roussouly theoretical apex of lordosis in predicting mechanical complications in adult spinal deformity (ASD)., Summary of Background Data: Achieving adequate sagittal alignment is critical to obtain favorable outcomes in ASD surgery. It has been proposed that mechanical complications are largely secondary to postoperative spinal alignment., Methods: Retrospective review of consecutive primary ASD cases that underwent deformity correction in the same institution over a 5-year period. Association between the 6-week postoperative spinal alignment classification and occurrence of mechanical complications on the last follow-up was assessed using logistic regressions. The discriminant capacity was assessed using the receiver operating characteristic (ROC) curve analysis., Results: 58.3% (N = 49/84) of patients presented with mechanical complications and 32.1% (N = 27/84) underwent revision surgery. GAP score did not show discriminant ability to predict complications (AUC = 0.53, 95% confidence interval [CI] = 0.40-0.66, P = 0.58). Conversely, the SRS-Schwab sagittal modifier score demonstrated a statistically significant (although modest) predictive value for mechanical complications (AUC = 0.67, 95% CI = 0.54-0.79, P = 0.008). There was a significant association between pelvic tilt (PT) (P = 0.03) and sagittal vertical axis (SVA) (P = 0.01) at 6 weeks postoperatively and the occurrence of later mechanical complications. There was no significant association between matched Roussouly theoretical apex of lordosis and final outcome (P = 0.47)., Conclusion: The results point to the complexity of mechanical failure and the high likelihood that causative factors are multifactorial and not limited to alignment measures. GAP score should be used with caution as it may not explain or predict mechanical failure based on alignment in all populations as originally expected. Future studies should focus on etiology, surgical technique, and patient factors in order to generate a more universal score that can be applied to all populations.Level of Evidence: 4., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Adolescent idiopathic scoliosis (AIS) has been associated with diminished postural stability and a greater prevalence of back pain. Currently, the literature is lacking information on the effect of spinal fusion on both postural stability and its association with back pain. Our objectives were to evaluate the postsurgical effect of spinal morphological changes on static standing balance and assess the influence of these alterations on reported pain throughout the perioperative period., Methods: Twenty consecutive AIS patients schedule to undergo spinal fusion surgery were recruited and followed prospectively at the Shriners Hospitals for Children-Canada. Data was collected at the preoperative, 6 weeks and 6 months postoperative visits. Spinal morphology data was collected through 3D reconstructed simultaneous standing biplanar radiographs using the SterEOS software. Postural balance was assessed through Moticon© sensor insoles and analyzed through their software. The data was simultaneously collected as part of the Global Biomechanical and morphological Assessment. Pain was evaluated through self-reported questionnaires., Results: Morphological curve parameters were significantly reduced after surgery. Balance parameters did not change significantly throughout the perioperative period with the exception of the Center of Pressure of the left foot medial/lateral transient shift (P = 0.017) at 6 weeks. Of note, preoperative balance parameters were associated with the degree of right thoracic Cobb angles (P = 0.029 R = 0.528). Pain scores significantly improved 6 weeks and 6 months after the surgery. Pain intensity diminished in the thoracic and lumbar spine but worsen in the neck region at the 6 weeks and 6 months postoperative time points (P = 0.044). Greater residual Cobb angle difference between Mid thoracic and Thoracolumbar/Lumbar curves was associated with greater pain severity at 6 weeks postop (P < 0.005). In addition, greater residual thoracic deformity was associated with significant pain severity 6 months after surgery (P < 0.05)., Conclusions: Improved spinal morphology of postsurgical AIS patients has no significant impact on their static standing balance. Suggesting that other factors apart from the spinal morphology may contribute to AIS patients' balance during stance. Although balance did not influence pain severity, spinal morphology and its correction appear to have influenced the intensity and location of back pain.

Study Design: Prospective experimental study with on-site simulation., Objective: To compare the accuracy and efficiency of different techniques for pedicle screw instrumentation (PSI)., Summary of Background Data: Improving the safety and efficiency of PSI is a critical step to reduce the complication rates and the cost of scoliosis surgery. Innovative operative techniques for PSI have shown to safely improve efficiency, thereby reducing cost. Surgical simulation is a valuable tool to study different operative techniques., Methods: Five spine fellows instrumented 20 simulation models of a scoliotic spine with 10 pedicle screws per model. Four techniques were studied, including the conventional pedicle probe and the innovative sequential drilling technique, with or without computed tomography (CT)-based navigation. Our primary outcome measures were efficiency and accuracy of PSI. We analyzed the data with bivariate analyses using the Chi-square test for categorical variables and the Student t test or ANalysis Of VAriance with Bonferroni post-hoc tests for continuous variables., Results: The drilling techniques (free hand and navigated) were more efficient as compared with the pedicle probe techniques (P < 0.01). The navigated techniques resulted in better accuracy as compared with the free hand techniques (P = 0.036). Most pedicle breaches were medial (n = 32/52). The concave apical pedicle (T4 right side) had the highest incidence of breaches. There was no significant difference in efficiency comparing the free hand and the navigated pedicle probe techniques (P = 0.261) or comparing the free hand drilling and the navigated drilling techniques (P = 1.00)., Conclusion: On site surgical simulation is a promising concept for teaching advanced procedural skills. Our findings suggest that navigation improves the accuracy of PSI while sequential drilling safely improves efficiency. Combining navigation with sequential drilling can significantly improve the accuracy and the efficiency of PSI in scoliosis surgery, as previously suggested with our published clinical data., Level of Evidence: 4.

Background Context: Zero-profile (also called self-locking, anchored or stand-alone cages) have been recently proposed as an interesting alternative for anterior cervical discectomy and fusion (ACDF), as they are supposed to reduce the rates of post-operative cage extrusion without necessarily incurring in the additional surgical time and increased rates of dysphagia associated with plating. Nevertheless, the exact indications of zero-profile anchored cages have not yet been established in the literature., Purpose: To report the first case of a vertebral body fracture between the blades of zero-profile anchored cages after ACDFs in adjacent levels and to review the available literature on hardware-related complications after multi-level ACDFs with zero-profile anchored cages., Study Design: Case report and systematic literature review., Methods: The authors report the first case of a vertebral body fracture between the blades of zero-profile anchored cages after ACDFs in adjacent levels. The patient presented with refractory mechanical neck pain at the 1-month post-operative follow-up, ultimately requiring a posterior instrumented fusion. A comprehensive systematic literature review on the available data regarding the safety, complications as well as radiological and clinical outcomes of zero-profile anchored cages is also performed., Results: In the reported case, the use of zero-profile anchored cages in adjacent levels on the cervical spine led to a fracture of the vertebral body between the cages at the 1-month follow-up, with anterior avulsion of the part of the vertebral body where the blades from the two cages converged. According to the systematic literature review which included 409 patients from 10 different clinical series (with a total cumulative follow-up of approximately 535 patients-year), there were only two reported hardware-related complications after ACDF with zero-profile anchored cages, none of them involving fracture at the level of convergence of blades or screws., Conclusions: Although hardware-related complications after the use of zero-profile anchored cages seem to be rare events, future biomechanical and clinical studies are warranted in order to evaluate the safety of employing such devices for the treatment of multilevel degenerative disc disease in the cervical spine.

Background: Many practicing spine surgeons believe that instrumentation can be removed during revision surgery in successful posterolateral or anterior spinal fusions, confirmed by computed tomography and intraoperative exploration. The stress-shielding effect of spinal instrumentation was well described in the late 1980s and 1990s but has not received recent attention. Despite the paucity of recent literature, concepts underlying the biology and biomechanics of the spinal fusion mass remain particularly salient given the increasing incidence of revision spinal fusion surgery. The aim of this study was to highlight a potential complication of instrumentation removal owing to stress shielding of instrumentation on the spinal column and fusion mass., Methods: A retrospective review was performed, and a small case series was described., Results: In 3 cases, despite apparent solid fusion demonstrated on preoperative computed tomography and confirmed by intraoperative exploration, new fractures developed after removal of instrumentation. In these cases, fracture occurred at the transition zone between the newly rigid instrumented area and previous fusion. This highlights the relative weakness of the fusion and may be explained by the stress-shielding effect of instrumentation within the fusion mass., Conclusions: Spinal instrumentation revision requires careful consideration, and routine implant removal should not be performed. The presence of a solid fusion on computed tomography and/or at intraoperative exploration may not justify implant removal in these cases. In cases of extension of a fusion, use of a bridging connection to the new implants should be considered. The cases presented demonstrate the consequences of the stress-shielding effect of implants on the spine and fusion mass., (Copyright © 2018 Elsevier Inc. All rights reserved.)

OBJECTIVE The aim of this study was to evaluate the anatomical and surgical risk factors for screw-related facet joint violation at the superior level in lumbar fusion. METHODS The authors conducted a retrospective review of a consecutive series of posterior lumbar instrumented fusions performed by a single surgeon. Inclusion criteria were primary lumbar fusion of 1 or 2 levels for degenerative disorders. The following variables were analyzed as possible risk factors: surgical technique (percutaneous vs open screw placement), depth of surgical field, degree of anterior slippage of the superior level, pedicle and facet angle, and facet degeneration of the superior level. Postoperative CT scans were evaluated by 2 independent reviewers. Axial, sagittal, and coronal views were reviewed. Pedicle screws were graded as intra-articular if they clearly interposed between the superior and inferior facet joints of the superior level. Multivariate logistic regression analyses were conducted to assess the factors associated with this complication. RESULTS One hundred thirty-one patients were included. Interobserver reliability for facet joint violation assessment was high (κ = 0.789). The incidence of superior facet joint violation was 12.59% per top-level screw (33 of 262 proximal screws). The rate of facet violation was 28.0% in the percutaneous technique group (14 of 50 patients) and 12.3% in the open surgery group (10 of 81 patients) (OR 2.26, 95% CI 1.09-4.21; p = 0.024). In multivariate logistic regression analysis, independent predictors of facet violation were percutaneous screw placement (adjusted OR 3.31, 95% CI 1.42-7.73; p = 0.006), right-side pedicle screw (adjusted OR 3.14, 95% CI 1.29-7.63; p = 0.011), and facet angle > 45° (adjusted OR 10.95, 95% CI 4.64-25.84; p < 0.0001). CONCLUSIONS The incidence of facet joint violation was higher in percutaneous minimally invasive than in open technique for posterior lumbar spine surgery. Also, coronal orientation of the facet joint is a significant risk factor independent of the surgical technique.

Stand-alone cervical laminectomy for degenerative cervical myelopathy (DCM) has become increasingly rare due to risk of postlaminectomy kyphosis. This article discusses the biomechanics of cervical degeneration and how laminectomy effects spine stability, and summarizes relevant clinical studies to help guide surgical decision-making for the posterior treatment of DCM. Laminectomy and fusion remains a safe and efficacious treatment. Stand-alone laminectomy should only be used for a highly selected patient population with relative stiff lordotic cervical spines, using care to not disrupt facets and C2 and C7 muscle attachments., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Object: Deep wound infections are one of the most common and serious complications of spinal surgery. The impact of such infections on long-term outcomes is not well understood. The purpose of this study was to evaluate the functional status and satisfaction in patients who suffered a deep wound infection after undergoing lumbar arthrodesis for symptomatic degenerative disc disease., Methods: The authors conducted a prospective study in 13 patients with a clinical and radiological diagnosis of symptomatic degenerative lumbar stenosis and instability; after undergoing decompression and instrumentation-augmented arthrodesis, the patients suffered a deep wound infection (infection group). A 3:1 (39-patient) matched cohort was selected for comparison (control group). All surgeries were performed during the same period and by a single surgeon. The postoperative infections were all treated in a similar manner and the instrumentation was not removed. Both groups were followed up and assessed with validated outcome instruments: Numerical Rating Scale of pain, Oswestry Disability Index, 36-Item Short Form Health Survey, Beck Depression Inventory, and Hospital Anxiety and Depression Scale. Patient satisfaction was also determined., Results: The median follow-up duration was 22 months (range 6-108 months). The mean patient age was 62 ± 10 years, and 59.6% of the patients were female. There was no significant difference between the groups in pain, functional disability, quality of life, or depression and anxiety. However, 53.8% of the patients with infection were not satisfied with the procedure at the final evaluation, compared with 15.4% of the patients without a deep wound infection (p = 0.003)., Conclusions: Patients with successfully treated postoperative deep wound infections do not have a difference in functional outcome compared with patients who underwent an identical operation but did not suffer a complicating infection. Patients who suffered an infection were more likely to be unsatisfied with the procedure than patients who did not.

Study Design: Prospective longitudinal cohort., Objective: To evaluate the efficacy of hydroxyapatite (HA) grafts in combination with cervical plates in terms of fusion, restoration, and maintenance of cervical lordosis and to compare clinical and radiologic outcomes of patients who experienced graft breakage with patients who did not., Summary of Background Data: The most common complication related to the use of HA graft for cervical anterior fusion is graft breakage. However, the implication of graft breakage in terms of loss of graft height, cervical alignment, plate migration, and clinical outcomes has not been adequately evaluated., Methodology: A prospective study of 40 patients who underwent anterior cervical fusion in which HA graft and plate systems were used. Clinical and radiologic assessments were made 1 month after surgery and again at the final follow-up., Results: At the final follow-up evaluation, 80% of patients had an excellent clinical outcome, 15% had a good outcome, and 5% had a fair outcome based on Odom's classification. All patients achieved lordotic alignment in the immediate postoperative period. Graft breakage was observed in 25% of cases. Patients who experienced HA block breakage have 21 times more chance to have intervertebral height loss greater than 2 mm, 4.9 times more likely to undergo loss of cervical alignment exceeding 3 degrees, and 12.4 times more likely to present migration of the plates when compared to patients who had normal HA grafts., Conclusion: Despite the positive clinical results observed in this study, breakage of HA grafts was a common complication occurring in 25% of patients. Graft breakage was associated with strut height loss of more than 2 mm, loss of cervical alignment exceeding 3 degrees and a higher rate of plate migration. These changes related to the HA graft breakage demonstrate the necessity to continue searching for better grafting methods to perform cervical interbody fusion.