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Purpose: To identify the technical complications associated with maxillary complete-arch implant-supported fixed prostheses (ISFPs) and to evaluate the survival rates of both dental implants and prostheses. In addition, we sought to analyze the impact that the presence of cantilevers, the type of prosthetic abutment, and the number of implants have on the occurrence of complications. Materials and Methods: Data were obtained from standardized clinical assessments carried out in a single appointment by two calibrated professionals (F.B.A. and I.A.Y.) using information from dental records. Results: The sample consisted of 64 patients rehabilitated with ISFPs classified as hybrid prostheses (metal-resin). The survival rate for implants was 98.6% after 1 to 12 years (5.2 years ± 36.6 months) and was 100% for the prostheses after a follow-up of 12 to 144 months (mean: 48.1 ± 33.94 months). The most frequent complications were occlusal wear (82.8% of patients) as well as loosening of prosthetic screws (16.6%) and abutments (8.1%). The screw loosening frequency was significantly greater in 30-degree abutments compared with straight abutments (P = .008), but no significant difference was found between 17-degree and 30-degree abutments. Prostheses with a higher occurrence of screw loosening had a greater average cantilever length/anteroposterior spread (CL/AP) ratio (0.9 ± 0.5). In addition, abutments placed on distal implants were more likely to loosen (P < .001). The absence of mutually protected occlusion did not significantly influence the loosening of prosthetic screws and abutments. Conclusions: Implant-supported fixed maxillary complete-arch rehabilitations have high survival rates but are subject to technical complications. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the screw loosening and fracture resistance of different hybrid abutment crown restorations after thermomechanical aging. Materials and Methods: Restorations were produced from zirconia, lithium disilicate, and hybrid ceramics with a CAD/CAM system (n = 10). Restorations and titanium bases (Ti-bases) were cemented, and the abutment screws were torqued to 30 Ncm. They were retorqued after 10 minutes, and then the removal torque values (RTVs) were measured. After 250,000 and 500,000 cycles of thermomechanical aging were completed, the RTVs were measured again, and removal torque loss (RTL) ratios were calculated. The specimens were subjected to a fracture resistance test after 750,000 cycles of thermomechanical aging, and the load at failure was recorded as the fracture resistance (N). The results were statistically analyzed (a = .05). Results: Aging was effective on the RTVs and RTL ratios (P < .001). The highest RTV was observed before aging; however, the RTVs significantly decreased and RTL ratios significantly increased after aging (P < .05). The fracture resistance values significantly differed among the ceramic materials. All lithium disilicate and hybrid ceramic specimens showed restoration fracture and most of the zirconia specimens showed Ti-base-related failure. Conclusions: Hybrid abutment crowns made of zirconia, lithium disilicate, and hybrid ceramics can withstand the average occlusal forces in the molar region; however, the ceramic type may affect the failure type. Retightening of the abutment screws after 10 minutes following the first tightening and annually may be beneficial to prevent the adverse effects of screw loosening on the integrity of the implant-abutment connection. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to identify whether the ratio of the vertebral Hounsfield unit to serum pentosidine (H/P ratio), which reflects bone density and quality, can predict screw loosening after spinal fusion surgery. Methods: A retrospective case-control study was conducted in 35 patients (mean age 71 ± 10.4 years, 18 men) who underwent spinal interbody fusion for lumbar spine disease between June 2020 and February 2022. Screw loosening was evaluated by computed tomography at 12 months postoperatively. Information was collected on patient background characteristics, including age, sex, body mass index, diagnosis, dialysis status, smoking history, diabetes, steroid use, and osteoporosis. Imaging parameters, the surgical method used, number of fixed intervertebral segments, intervertebral level (including L5/S1 or not), and the H/P ratio were also investigated. Risk factors associated with screw loosening and pseudarthrosis were examined in univariable and multivariable logistic regression analyses. A P-value of < 0.05 was considered statistically significant. Results: Screw loosening occurred in 14 of 35 patients (40%). Multivariate analysis revealed that the H/P ratio (odds ratio 0.09, confidence interval 0.02–0.53, P = 0.007) was a significant risk factor for screw loosening at 12 months postoperatively. Conclusion: This study demonstrates that the H/P ratio, which reflects both bone density and deterioration of bone quality in the vertebral body, may serve as a predictor of screw loosening at 12 months after lumbar spinal surgery. [ABSTRACT FROM AUTHOR]

Study Design.: Retrospective Cohort. Objective.: (1) To determine if vertebral HU values obtained from preoperative CT predict postoperative outcomes following one to three level lumbar fusion and (2) to investigate whether decreased BMD values determined by HU predict cage subsidence and screw loosening. Summary of Background Data.: In light of suboptimal screening for osteoporosis, vertebral computerized tomography (CT) Hounsfield Units (HU), have been investigated as a surrogate for bone mineral density (BMD). Materials and Methods.: In this retrospective study, adult patients who underwent one to three level posterior lumbar decompression and fusion (PLDF) or transforaminal lumbar interbody and fusion (TLIF) for degenerative disease between the years 2017 and 2022 were eligible for inclusion. Demographics and surgical characteristics were collected. Outcomes assessed included 90-day readmissions, 90-day complications, revisions, patient-reported outcomes (PROMs), cage subsidence, and screw loosening. Osteoporosis was defined as HU of ≤110 on preoperative CT at L1. Results.: We assessed 119 patients with a mean age of 59.1, of whom 80.7% were white and 64.7% were nonsmokers. The majority underwent PLDF (63%) compared with TLIF (37%), with an average of 1.63 levels fused. Osteoporosis was diagnosed in 37.8% of the cohort with a mean HU in the osteoporotic group of 88.4 compared with 169 in nonosteoporotic patients. Although older in age, osteoporotic individuals did not exhibit increased 90-day readmissions, complications, or revisions compared with nonosteoporotic patients. A significant increase in the incidence of screw loosening was noted in the osteoporotic group with no differences observed in subsidence rates. On multivariable linear regression osteoporosis was independently associated with less improvement in visual analog scale (VAS) scores for back pain. Conclusions.: Osteoporosis predicts screw loosening and increased back pain. Clinicians should be advised of the importance of preoperative BMD optimization as part of their surgical planning and the utility of vertebral CT HU as a tool for risk stratification. Level of Evidence.: 3. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim Materials and Methods Results Conclusions Biomechanical performance is a critical factor in the long‐term success of dental implants, with abutment screw loosening being a common clinical issue. This study aimed to examine the impact of abutment screw design and external load loading angles on abutment screw loosening.Abutments and abutment screws with 30°, 60°, 90°, and 180° fitting tapers were fabricated and tested for preload and initial loosening torque. Subsequently, dynamic loosening tests were conducted at loading angles of 15°, 30°, and 45°. Finite element analysis (FEA) was used to calculate the stress and strain distribution of the abutment screws.The findings indicated that large‐taper abutment screws exhibit a higher preload, whereas small‐taper abutment screws demonstrate greater loosening torque values. Additionally, as the loading angle increases, the loosening torque value decreases, and the stress and strain values of the abutment screw increase.Abutment screws with smaller taper heads exhibited superior resistance to loosening. Moreover, the anti‐loosening performance of the abutment screws decreased with higher external load loading angles. [ABSTRACT FROM AUTHOR]

ABSTRACT Objective Methods Results Conclusions Osteoporosis is a crucial risk factor for screw loosening. Our studies indicate that the bone mineral density (BMD) in the screw trajectory is a better predictor of screw loosening than the BMD of the lumbar spine or the screw insertion position. Research has shown that anchorage on the screw tip is the most significant factor for screw anchorage ability, while others argue that decreased bony quality in the pedicle poses a significant risk for screw loosening. This study aimed to determine whether the bony quality of the screw tip, pedicle, or screw‐anchored vertebral body plays the most significant role in screw anchorage ability.A total of 73 patients who underwent single–segment bilateral pedicle screw fixation, along with posterior and transforaminal lumbar interbody fusion (PLIF and TLIF), from March 2019 to September 2020 were included in this retrospective study. The Hounsfield unit (HU) value of the fixed vertebral bodies, the entire screw trajectory, screw tip, screw–anchoraged vertebral body, and pedicles were measured separately. Data from patients with and without screw loosening were compared, and regression analyses were conducted to identify independent risk factors. Additionally, the area under the curve (AUC) values were computed to assess the predictive performance of different parameters. Furthermore, fixation strength was calculated in numerical models with varying bony densities in different regions.HU values were found to be significantly lower in the loosening group across most measuring methods (HU values in the pedicle, 148.79 ± 97.04, 33.06 ± 34.82, p < 0.001). Specifically, the AUC of screw loosening prediction was notably higher when using HU values of the pedicle compared to other methods (AUC in the pedicle > 0.9 and in the screw insertion position > 0.7). Additionally, computational results for fixation strength revealed a clear decline in screw anchorage ability in models with poor BMD in the pedicle region.Pedicle bone quality plays a more significant role in screw anchorage ability than that in other regions. The innovation of bony augmentation strategies should pay more attention to this region to optimize the screw anchorage ability effectively. [ABSTRACT FROM AUTHOR]

Summary 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

Objective Poor bone quality is a risk factor for postoperative complications after degenerative lumbar fusion surgery. The magnetic resonance imaging-based vertebral bone quality (VBQ) score is a good tool for assessing bone quality, and this is the first meta-analysis performed to summarize the predictive value of the VBQ score for cage subsidence and screw loosening in patients undergoing degenerative lumbar surgery. Methods Studies were comprehensively searched in electronic databases. The quality of the studies was assessed. The pooled sensitivity, specificity and summary receiver operating characteristic curve were calculated. Publication bias was assessed and meta-regression was conducted. Results We ultimately included 9 studies with a total of 1,404 patients with a mean age of 60.4 years and a percentage of females of 57.0%. According to the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies 2) tool to assess methodological quality, the quality of the included studies was relatively low and risks of bias might exist. Results showed that a high VBQ was significantly associated with cage subsidence and screw loosening, and risk factor analysis revealed that the merged odds ratio was 5.37 for cage subsidence and 3.87 for screw loosening. With a VBQ cutoff value of 3.34±0.45, the pooled sensitivity and specificity for the diagnosis of postoperative complications were 0.75 and 0.75, respectively, and the area under the curve was 0.82 (95% confidence interval, 0.78–0.85). Conclusion A high VBQ was associated with a high risk of cage subsidence and screw loosening in patients who underwent degenerative lumbar surgery. The VBQ score could be considered for identifying high-risk patients for further evaluation.

Background: Various strategies have been used to reduce pedicle screw loosening following lumbar instrumented fusion, but all strategies have limitations. In this prospective multicenter cohort study, outcomes of elderly patients with reduced bone density who underwent primary or revision fusion surgery using a novel technique of pedicle screw augmentation with demineralized bone fiber (DBF) anchors were evaluated. Methods: This study included elderly patients (aged >65 years) with dual-energy x-ray absorptiometry-confirmed reduced bone density who required lumbar pedicle screw fixation and were treated with supplemental DBF allograft anchors during primary or revision surgery. The need for DBF anchors was determined by evaluating preoperative computed tomography (CT) scans (for revision surgery) and by the surgeons’ tactile feedback intraoperatively during pedicle screw insertion and removal. After determining the pedicle screw void diameter with a sizing instrument, DBF anchors and pedicle screws of the same diameter were placed into the void. CT scans were obtained on postoperative day 2 to assess pedicle breach, pedicle fracture, or anchor material extrusion and at 6 and 12 months postoperatively to assess screw loosening. Thereafter, to minimize radiation exposure, CT scans were only performed for recurrence of pain. Results: Twenty-three patients (79% women; mean age, 74 years) received 50 lumbosacral pedicle screws augmented with DBF anchors. Most surgeries (n = 18, 78%) were revisions, and most anchors were inserted into revision pedicle screw trajectories (n = 33, 66%). Day-2 CT scans revealed no pedicle breach/fracture or extrusion of anchor material. During a mean follow-up of 15 months (12–20 months), no screw loosening was detected, and no patient required pedicle screw revision surgery. There were no adverse events attributable to DBF allografts. Conclusions: DBF allograft anchors appear to be safe and effective for augmenting pedicle screws during revision surgeries in female elderly patients with reduced bone density. Clinical Relevance: Clinically, DBF reduced the rate of pedicle screw loosening in patients with reduced bone density. A significant reduction in screw loosening can decrease the need for revision surgeries, which are costly and carry additional risks. Enhanced bone integration from the DBF may promote better healing and long-term stability. [ABSTRACT FROM AUTHOR]

Background: Atlantoaxial transarticular fixation, also called the Magerl technique, is said to be the most robust biomechanical method of fixation of the atlantoaxial vertebrae. However, the procedure carries a risk of spinal cord and vertebral artery injury during the insertion process, especially in patients with a high-riding vertebral artery. In this study, a computed tomography (CT)-based navigation system was used for preoperative planning and insertion. This investigation sought to determine the rate and direction of screw perforation as well as the incidence of screw loosening in computer-assisted atlantoaxial transarticular fixation. Methods: Sixty patients (31 men and 29 women; mean ± SD age: 65.3 ± 19.6 years) who received atlantoaxial transarticular screw insertion with preoperative CT navigation were analyzed. We investigated screw position and loosening by CT at the final follow-up. Results: Of the 108 screws inserted, the rate of Grade 2 or higher perforation was 4.6% (5/108). Nine of 81 (11.1%) screws inserted into the 44 patients who were followed for at least 6 months showed loosening. Logistic regression analysis revealed that unilateral insertion (odds ratio: 8.50, 95% confidence interval: 1.53-47.2, P = 0.014) was significantly associated with the incidence of screw loosening. Conclusions: The screw perforation rate of Grade 2 or higher in computer-assisted atlantoaxial transarticular screw fixation was 4.6%, with comparable frequencies of perforation direction. Unilateral insertion was a significant independent factor associated with screw loosening, which occurred in 11.1% of insertions. Clinical Relevance: Spine surgeons should follow up with patients with caution because screws with unilateral insertion are prone to loosening. Level of Evidence: 4. [ABSTRACT FROM AUTHOR]

Summary: 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. [ABSTRACT FROM AUTHOR]

Objective: Poor bone quality is a risk factor for postoperative complications after degenerative lumbar fusion surgery. The magnetic resonance imaging-based vertebral bone quality (VBQ) score is a good tool for assessing bone quality, and this is the first meta-analysis performed to summarize the predictive value of the VBQ score for cage subsidence and screw loosening in patients undergoing degenerative lumbar surgery. Methods: Studies were comprehensively searched in electronic databases. The quality of the studies was assessed. The pooled sensitivity, specificity and summary receiver operating characteristic curve were calculated. Publication bias was assessed and meta-regression was conducted. Results: We ultimately included 9 studies with a total of 1,404 patients with a mean age of 60.4 years and a percentage of females of 57.0%. According to the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies 2) tool to assess methodological quality, the quality of the included studies was relatively low and risks of bias might exist. Results showed that a high VBQ was significantly associated with cage subsidence and screw loosening, and risk factor analysis revealed that the merged odds ratio was 5.37 for cage subsidence and 3.87 for screw loosening. With a VBQ cutoff value of 3.34±0.45, the pooled sensitivity and specificity for the diagnosis of postoperative complications were 0.75 and 0.75, respectively, and the area under the curve was 0.82 (95% confidence interval, 0.78–0.85). Conclusion: A high VBQ was associated with a high risk of cage subsidence and screw loosening in patients who underwent degenerative lumbar surgery. The VBQ score could be considered for identifying high-risk patients for further evaluation. [ABSTRACT FROM AUTHOR]

MRI-based vertebral bone quality (VBQ) score is an effective predictor of pedicle screw loosening after lumbar fusion surgery and has been recognized as a valuable tool for assessing preoperative bone quality. Due to the lateral curvature of lumbar spine of degenerative scoliosis, accurate measurement of VBQ score by conventional measurement methods that capture MRI signal intensity at L1–4 may be limited under certain conditions. To this end, a new simplified S1 VBQ score method has been proposed, which is comparable to the previous L1–4 VBQ score or S1 Hounsfield unit (HU) value, and has high accuracy and reliability. To evaluate the predictive value of MRI-based S1 VBQ score for pedicle screw loosening following surgery for adult degenerative scoliosis (ADS). Retrospective single-center cohort. We reviewed 92 patients who underwent posterior lumbar interbody fusion (PLIF) with pedicle screw fixation for ADS between January 2017 and January 2020. Association between S1 VBQ score and pedicle screw loosening following surgery for ADS. We retrospectively reviewed the records of all patients who performed PLIF between January 2017 and January 2020. The clear zone around pedicle screws≥1 mm can be identified as screw loosening. The S1 VBQ score is calculated from the S1 central-based noncontrast T1-weighted magnetic resonance imaging (MRI). The signal intensity (SI) of the cerebrospinal fluid (CSF) was then measured using ROI placed at the L3 level to normalize the results. Multivariate logistic regression analysis was performed to identify independent risk factors for screw loosening. Then, constructed a receiver operating characteristic (ROC) curve and determined the threshold (cut-off) of VBQ score with high sensitivity and specificity based on Youden Index. A total of 92 patients were included, including 34 males and 58 females. The mean age of the patients was 61.23±1.23 years old. At 1-year follow-up, the screw loosening rate was 56.5% (52/92). The age and levels of fixation were higher in the loosening group than in the nonloosening group (p=.036, p=.025). Patients in the loosening group had a greater VBQ score compared to patients in the nonloosening group (3.31±0.41 vs 3.01±0.28, p=.001). Multivariate logistic regression analysis showed that advanced age (OR, 1.090; 95% CI 1.005–1.183; p=.039) and higher VBQ score (OR, 5.778; 95% CI 2.889–16.177; p=.001) were independent risk factors for screw loosening. In addition, the ROC curve were created to assess the role of VBQ score as predictors of screw loosening with a diagnostic accuracy of 74.6% (95% CI 64.2%–85.1%).The most suitable threshold for the VBQ score as determined by the Youden Index was 3.175 (sensitivity: 76.0%, specificity: 83.3%). Higher S1 VBQ score was significantly associated with pedicle screw loosening following surgery for ADS. The S1 VBQ score can be used as an effective preoperative predictor, which has the potential clinical application. [ABSTRACT FROM AUTHOR]

Purpose: To determine the accuracy of new electronic torque‐limiting devices (ET) when compared to new and used conventional‐style beam‐type (BT) mechanical torque‐limiting devices and hand‐piece style (HS) mechanical torque‐limiting devices. The secondary purpose was to compare any difference in accuracy between new and used mechanical torque‐limiting devices, and any difference in accuracy when used on a straight versus an angled screw channel abutment. Materials And Methods: A total of five torque‐limiting devices were used to obtain 2000 readings under standardized conditions. An implant analog was fastened into a digital torque meter, to which an abutment was connected. Pre‐determined torque values of 15 Ncm and 35 Ncm were applied, and actual torque values were recorded. A straight and an angled abutment were used to record 1000 readings each using the five torque‐limiting devices. An overall Kruskal‐Wallis test was applied to compare the median deviation among devices followed by a pairwise comparison (= 0.05). Results: For a target torque value of 15 Ncm on a straight abutment, the electronic device (ET) was statistically more accurate than the beam type (BT) new (p < 0.001) and used (p < 0.048) devices but less accurate than the hand‐piece style (HS) used device (p < 0.001). On an angled abutment for a target value of 15 Ncm, the electronic device (ET) was statistically more accurate than hand‐piece style (HS) new and used devices (p < 0.001). For a target torque value of 35 Ncm on a straight abutment, the ET was statistically more accurate than the HS new device (p < 0.001) but less accurate than the BT new device (p < 0.001). On an angled abutment for a target value of 35 Ncm, the electronic device (ET) was statistically less accurate than the beam‐type (BT) new device (p < 0.001), the beam‐type (BT) used device (p = 0.001), and the hand‐piece style (HS) used device (p < 0.001). The electronic device (ET) was the only device accurate within the ISO standard of accuracy of 6% for each of the target torque value/abutment design combinations. There was no statistically significant difference related to the type of abutment used (angled vs. straight). Conclusions: Electronic torque limiting devices (ET) are an acceptable method for delivering torque for implant restorations for straight and angled abutments at 15 Ncm and 35 Ncm torque values. Conventional style beam‐type (BT) mechanical torque‐limiting devices are a simple, predictable, validated, and inexpensive tool for delivering accurate torque at 15 Ncm and 35 Ncm torque values. The hand‐piece style (HS) mechanical torque‐limiting devices are predictable to deliver 15 Ncm torque values. [ABSTRACT FROM AUTHOR]

Objective Screw loosening is a common complication of internal fixation of pedicle screw. Therefore, the development of a pedicle screw with low loosening rate and high biosafety is of great clinical significance. This study aimed to investigate whether the application of a porous scaffold structure can improve the stability of pedicle screws by comparing the biomechanical properties of novel porous scaffold core pedicle screws (PSCPSs) with those of hollow lateral hole pedicle screws (HLHPSs) in a porcine lumbar spine. Methods Thirty‐two pedicle screws of both types were implanted bilaterally into the L1–4 vertebrae of four Bama pigs, with our newly designed PSCPSs on the right and HLHPSs on the left. All the Bama pigs were sacrificed 16 weeks postoperatively, and the lumbar spine was freed into individual vertebrae. Biomechanical properties of both the pedicle screws were evaluated using pull‐out tests, as well as cyclic bending and pull‐out tests, while the mechanical properties were assessed using three‐point bending tests. The data generated were statistically analyzed using paired‐sample t‐tests and two independent sample t‐tests. Results We found that the maximal pull‐out forces before and after cyclic bending of the PSCPSs (1161.50 ± 337.98 N and 1075.25 ± 223.33 N) were significantly higher than those of the HLHPSs (948.38 ± 194.32 N and 807.13 ± 242.75 N) (p 0.05 and p > 0.05, respectively). Additionally, both screws buckled rather than broke in the three‐point bending tests, with no statistically significant differences between the maximal bending load and modulus of elasticity of the two screws (p > 0.05 and p > 0.05, respectively). Conclusions Compared with the HLHPSs, the PSCPSs have greater pull‐out resistance and better fatigue tolerance with appropriate mechanical properties. Therefore, PSCPSs theoretically have significant potential for clinical applications in reducing the incidence of loosening after pedicle screw implantation.

Abstract Background Sacral screw loosening is a typical complication after internal fixation surgery through the vertebral arch system. Bicortical fixation can successfully prevent screw loosening, and how improving the rate of bicortical fixation is a challenging clinical investigation. Objective To investigate the feasibility of improving the double corticality of sacral screws and the optimal fixation depth to achieve double cortical fixation by combining the torque measurement method with bare hands. Methods Ninety-seven cases of posterior lumbar internal fixation with pedicle root system were included in this study. Based on the tactile feedback of the surgeon indicating the expected penetration of the screw into the contralateral cortex of the sacrum, the screws were further rotated by 180°, 360°, or 720°, categorized into the bicortical 180° group, bicortical 360° group, and bicortical 720° group, respectively. Intraoperatively, the torque during screw insertion was recorded. Postoperatively, the rate of double-cortex engagement was evaluated at 7 days, and screw loosening was assessed at 1 year follow-up. Results The bicortical rates of the 180° group, 360° group, and 720° group were 66.13%, 91.18% and 93.75%, respectively. There were statistically significant differences between the 180° group and both the 360° and 720° groups (P 0.05).The rates of loosening of sacral screws in the 180° group, 360° group, and 720° group were 20.97%, 7.35% and 7.81%, respectively. There were statistically significant differences between the 180° group and both the 360° and 720° groups (P 0.05). The bicortical 360° group achieved a relatively satisfactory rate of dual cortical purchase while maintaining a lower rate of screw loosening. Conclusion Manual insertion of sacral screws with the assistance of a torque measurement device can achieve a relatively satisfactory dual cortical purchase rate while reducing patient hospitalization costs.

Abstract Background Screw loosening is a commonly reported issue following spinal screw fixation and can lead to various complications. The initial cause of screw loosening is biomechanical deterioration. Previous studies have demonstrated that modifications in screw design can impact the local biomechanical environment, specifically the stress distribution on bone-screw interfaces. There are several different designs of screw tips available for clinically used pedicle screws; however, it remains unclear whether these variations affect the local stress distribution and subsequent screw anchorage ability. Methods This study conducted comprehensive biomechanical research using polyurethane foam mechanical tests and corresponding numerical simulations to investigate this topic. Models of pedicle screw-fixed osteoporotic polyurethane foam were created with two different clinically used screw tip designs (flat and steep) featuring varying tip lengths, taper angles, and diameters, as well as identical flank overlap areas and thread designs. The anchorage ability of the different models was assessed through toggle and pull-out test. Additionally, numerical mechanical models were utilized to compute the stress distributions at the screw and bone-screw interfaces in the different models. Results Mechanical tests revealed superior anchorage ability in models utilizing flat-tipped screws. Furthermore, numerical modeling indicated improved anchorage ability and reduced stress concentration tendency in these models. Conclusion Changes in screw tip design can significantly impact the biomechanical anchoring capability of screws. Specifically, flatter tip pedicle screws may mitigate the risk of screw loosening by alleviating stress concentration on bone-screw interfaces.

Background: Screw loosening is a commonly reported issue following spinal screw fixation and can lead to various complications. The initial cause of screw loosening is biomechanical deterioration. Previous studies have demonstrated that modifications in screw design can impact the local biomechanical environment, specifically the stress distribution on bone-screw interfaces. There are several different designs of screw tips available for clinically used pedicle screws; however, it remains unclear whether these variations affect the local stress distribution and subsequent screw anchorage ability. Methods: This study conducted comprehensive biomechanical research using polyurethane foam mechanical tests and corresponding numerical simulations to investigate this topic. Models of pedicle screw-fixed osteoporotic polyurethane foam were created with two different clinically used screw tip designs (flat and steep) featuring varying tip lengths, taper angles, and diameters, as well as identical flank overlap areas and thread designs. The anchorage ability of the different models was assessed through toggle and pull-out test. Additionally, numerical mechanical models were utilized to compute the stress distributions at the screw and bone-screw interfaces in the different models. Results: Mechanical tests revealed superior anchorage ability in models utilizing flat-tipped screws. Furthermore, numerical modeling indicated improved anchorage ability and reduced stress concentration tendency in these models. Conclusion: Changes in screw tip design can significantly impact the biomechanical anchoring capability of screws. Specifically, flatter tip pedicle screws may mitigate the risk of screw loosening by alleviating stress concentration on bone-screw interfaces. [ABSTRACT FROM AUTHOR]

Background: Dynamic lumbar stabilization aims to preserve spinal movement, offering stability and controlled motion. However, screw loosening, especially in patients with osteopenia and osteoporosis, remains challenging. Method: Between 2018 and 2022, a retrospective analysis was conducted on a total of 119 patients diagnosed with osteopenia and osteoporosis who underwent spinal dynamic instrumentation surgery. These patients were categorized into two groups: single-stage surgery (n = 67) and two-stage surgery (n = 52). Over the 48-month follow-up period, the occurrence and percentage of screw loosening were examined at each surgical level per patient, as well as by screw location (pedicular, corpus, tip). Clinical outcomes were evaluated using Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) scores. Results: Total screw loosening rates were significantly lower in the two-stage group (2.83%) compared to the single-stage group (14.63%, p < 0.001). Patient-based loosening occurred in 5 patients (9.6%) in the two-stage group and 16 patients (23.9%) in the single-stage group. Loosening rates were lower in the two-stage group at L2 (7.78%, p = 0.040), L3 (5.56%, p < 0.001), L4 (8.89%, p = 0.002), and L5 (10.00%, p = 0.006), but higher at S1 (21.11%, p = 0.964), T12 (15.56%, p = 0.031), and iliac levels (15.56%, p = 0.001). Pedicular section exhibited the highest loosening (37 cases). VAS and ODI scores improved significantly in both groups, with better outcomes in the two-stage group at the 48. months (p < 0.001). Conclusions: The two-stage surgical approach significantly reduces screw loosening in patients with osteopenia and osteoporosis undergoing dynamic stabilization surgery, offering enhanced stability and better clinical outcomes. [ABSTRACT FROM AUTHOR]

Introduction: Despite modern fixation techniques, spinopelvic fixation failure (SPFF) after adult spinal deformity (ASD) surgery ranges from 4.5 to 38.0%, with approximately 50% requiring reoperation. Compared to other well-studied complications after ASD surgery, less is known about the incidence and predictors of SPFF. Aims/objectives: Given the high rates of SPFF and reoperation needed to treat it, the purpose of this systematic review and meta-analysis was to report the incidence and failure mechanisms of SPF after ASD surgery. Materials/methods: The literature search was executed across four databases: Medline via PubMed and Ovid, SPORTDiscus via EBSCO, Cochrane Library via Wiley, and Scopus. Study inclusion criteria were patients undergoing ASD surgery with spinopelvic instrumentation, report rates of SPFF and type of failure mechanism, patients over 18 years of age, minimum 1-year follow-up, and cohort or case–control studies. From each study, we collected general demographic information (age, gender, and body mass index), primary/revision, type of ASD, and mode of failure (screw loosening, rod breakage, pseudarthrosis, screw failure, SI joint pain, screw protrusion, set plug dislodgment, and sacral fracture) and recorded the overall rate of SPF as well as failure rate for each type. For the assessment of failure rate, we required a minimum of 12 months follow-up with radiographic assessment. Results: Of 206 studies queried, 14 met inclusion criteria comprising 3570 ASD patients who underwent ASD surgery with pelvic instrumentation (mean age 65.5 ± 3.6 years). The mean SPFF rate was 22.1% (range 3–41%). Stratification for type of failure resulted in a mean SPFF rate of 23.3% for the pseudarthrosis group; 16.5% for the rod fracture group; 13.5% for the iliac screw loosening group; 7.3% for the SIJ pain group; 6.1% for the iliac screw group; 3.6% for the set plug dislodgement group; 1.1% for the sacral fracture group; and 1% for the iliac screw prominence group. Conclusion: The aggregate rate of SPFF after ASD surgery is 22.1%. The most common mechanisms of failure were pseudarthrosis, rod fracture, and iliac screw loosening. Studies of SPFF remain heterogeneous, and a consistent definition of what constitutes SPFF is needed. This study may enable surgeons to provide patient specific constructs with pelvic fixation constructs to minimize this risk of failure. [ABSTRACT FROM AUTHOR]

Background: Sacral screw loosening is a typical complication after internal fixation surgery through the vertebral arch system. Bicortical fixation can successfully prevent screw loosening, and how improving the rate of bicortical fixation is a challenging clinical investigation. Objective: To investigate the feasibility of improving the double corticality of sacral screws and the optimal fixation depth to achieve double cortical fixation by combining the torque measurement method with bare hands. Methods: Ninety-seven cases of posterior lumbar internal fixation with pedicle root system were included in this study. Based on the tactile feedback of the surgeon indicating the expected penetration of the screw into the contralateral cortex of the sacrum, the screws were further rotated by 180°, 360°, or 720°, categorized into the bicortical 180° group, bicortical 360° group, and bicortical 720° group, respectively. Intraoperatively, the torque during screw insertion was recorded. Postoperatively, the rate of double-cortex engagement was evaluated at 7 days, and screw loosening was assessed at 1 year follow-up. Results: The bicortical rates of the 180° group, 360° group, and 720° group were 66.13%, 91.18% and 93.75%, respectively. There were statistically significant differences between the 180° group and both the 360° and 720° groups (P < 0.05). However, there was no statistically significant difference between the 360° group and the 720° group (P > 0.05).The rates of loosening of sacral screws in the 180° group, 360° group, and 720° group were 20.97%, 7.35% and 7.81%, respectively. There were statistically significant differences between the 180° group and both the 360° and 720° groups (P < 0.05). However, there was no statistically significant difference between the 360° group and the 720° group (P > 0.05). The bicortical 360° group achieved a relatively satisfactory rate of dual cortical purchase while maintaining a lower rate of screw loosening. Conclusion: Manual insertion of sacral screws with the assistance of a torque measurement device can achieve a relatively satisfactory dual cortical purchase rate while reducing patient hospitalization costs. [ABSTRACT FROM AUTHOR]

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Objective: Screw loosening is a common complication of internal fixation of pedicle screw. Therefore, the development of a pedicle screw with low loosening rate and high biosafety is of great clinical significance. This study aimed to investigate whether the application of a porous scaffold structure can improve the stability of pedicle screws by comparing the biomechanical properties of novel porous scaffold core pedicle screws (PSCPSs) with those of hollow lateral hole pedicle screws (HLHPSs) in a porcine lumbar spine. Methods: Thirty‐two pedicle screws of both types were implanted bilaterally into the L1–4 vertebrae of four Bama pigs, with our newly designed PSCPSs on the right and HLHPSs on the left. All the Bama pigs were sacrificed 16 weeks postoperatively, and the lumbar spine was freed into individual vertebrae. Biomechanical properties of both the pedicle screws were evaluated using pull‐out tests, as well as cyclic bending and pull‐out tests, while the mechanical properties were assessed using three‐point bending tests. The data generated were statistically analyzed using paired‐sample t‐tests and two independent sample t‐tests. Results: We found that the maximal pull‐out forces before and after cyclic bending of the PSCPSs (1161.50 ± 337.98 N and 1075.25 ± 223.33 N) were significantly higher than those of the HLHPSs (948.38 ± 194.32 N and 807.13 ± 242.75 N) (p < 0.05, p < 0.05). In 800 cycles of the bending tests, neither PSCPS nor HLHPS showed loosening or visible detachment, but their maximal pull‐out forces after cyclic bending tests decreased compared to those in cycles without cyclic bending tests (7.43% and 14.89%, respectively), with no statistical significance (p > 0.05 and p > 0.05, respectively). Additionally, both screws buckled rather than broke in the three‐point bending tests, with no statistically significant differences between the maximal bending load and modulus of elasticity of the two screws (p > 0.05 and p > 0.05, respectively). Conclusions: Compared with the HLHPSs, the PSCPSs have greater pull‐out resistance and better fatigue tolerance with appropriate mechanical properties. Therefore, PSCPSs theoretically have significant potential for clinical applications in reducing the incidence of loosening after pedicle screw implantation. [ABSTRACT FROM AUTHOR]

Aim: Evaluate effect of conical hybrid stock and computer-aided design/computer-aided manufacturing (CAD/CAM) abutments on the strain developed around implant and the screw loosening. Patients and methods: Sixteen epoxy resin blocks containing implant assembly (fixture, abutment, abutment screw, cemented zirconia crown) divided into two equal groups (eight blocks) in each group as fallow: group (A): eight blocks with implants attached to Stock abutment with conical hybrid connection to retain the crown to the implant. Group (B): Eight blocks with implants attached to customized CAD/CAM milled abutment with the same size and connection to retain the crown to the implant. The samples were subjected to dynamic cyclic loading 150 000 cycles using chewing simulator. A digital torque gauge was used to evaluate screw loosening by measuring removal torque value (RTV) before and after cyclic loading. Strain gauge was installed around implants in buccal, palatal aspects of each implant, and a load of 100 N was applied vertically and another load of 65 N was applied obliquely by using universal testing machine and the strain was determined using strain meter. Results: For GA, percentage of initial removal torque loss (RTL) was (17.988 ± 1.248%) and significantly increased after loading (30.763 ± 1.176%). For GB, percentage of initial removal torque loss was (24.350 ± 1.239%) and increased significantly after loading (33.313 ± 2.840%). For strain results under vertical and oblique loading, there was no statistically significant difference in both groups in stock and cad cam abutments and the strain measurement under oblique loading were significantly higher than the strains measured under vertical loading in both groups. Conclusions: Screw loosening occurred in both stock abutments and CAD/CAM abutments but CAD/CAM abutments yielded greater removal torque reduction (RTV) reduction% than the stock abutments and stock abutments showed little stress values around implant than CAD/CAM abutment without statistically significant difference. Off-axial loads will generate more stresses around implants. [ABSTRACT FROM AUTHOR]

Background: Dental implant abutment screw loosening is an increasingly common problem, as evidenced by multiple studies that have investigated its causes. The objective of this study was to compare the screw loosening torque values before and after cyclic loading and to determine whether they are affected by the CAD/CAM abutment manufacturing technique (machined or laser-sintered) and abutment angulation. Materials and Methods: Ninety implants were used and divided into two groups: 45 implants received machined abutments (group A) and 45 implants received laser-sintered abutments (group B). Each group was further divided into three subgroups, with 15 implants each, based on the abutment angulation involved (0°, 15° and 20°). The abutments were tightened to the torque recommended by the manufacturer, and the reverse torque value was measured before and after cyclic loading (300,000 cycles). Data analysis was performed using one-way ANOVA and Wilcoxon signed-rank tests. Results: Statistically significant differences were observed between the laser-sintered and machined groups (p < 0.01). Additionally, differences were observed between subgroups with different angulations for both machined (16.2 ± 1.75, 14.7 ± 1.74 and 13.4 ± 1.08 Ncm) and laser-sintered abutments (14.6 ± 1.25, 12.7 ± 1.2 and 11.1 ± 1.35 Ncm) (0°, 15° and 20°, respectively). Conclusions: The final screw loosening torque after cyclic loading was lower than the initial loosening torque. Both abutment angulation and the CAD/CAM manufacturing method exerted a statistically significant influence on the final loosening torque. The abutment angulation factor was estimated to have an influence of 34.5%, while the abutment manufacturing method was estimated to have an influence of 21%. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the factors affecting caudal screw loosening after spinopelvic fixation for adult patients with spinal deformity. This meta-analysis calculated the weighted mean difference (WMD) and odds ratio (OR) using Review Manager ver. 5.3 (RevMan; Cochrane, London, UK). The loosening group was older than the control group (WMD, 2.17; 95% confidence interval [CI], 0.48–3.87; p=0.01). The S2 alar-iliac (S2AI) could prevent the caudal screw from loosening (OR, 0.43; 95% CI, 0.20–0.94; p=0.03). However, gender distribution (p=0.36), the number of fusion segments (p=0.24), rod breakage (p=0.97), T-score (p=0.10), and proximal junctional kyphosis (p=0.75) demonstrated no difference. Preoperatively, only pelvic incidence (PI) in the loosening group was higher (WMD, 5.08; 95% CI, 2.71–7.45; p

To investigate S2 alar screw (S2AS) accuracy and factors associated with S2AS loosening and lumbosacral nonunion. We retrospectively reviewed patients who underwent lumbosacral fusion surgery with S2AS addition under fluoroscopy. S2AS loosening and lumbosacral nonunion were analyzed using a 1-year postoperative computed tomography. S2AS insertion accuracy was originally classified as accurate, short, anterior perforation, lateral perforation, and sacroiliac joint (SIJ) deviation among lateral perforation. Clinical data including sex, age, body mass index, fused segments, fusion procedure, primary or revision surgery, Japanese Orthopedic Association scores and complications were collected. Factors associated with S2AS loosening and lumbosacral nonunion were analyzed. A total of 37 patients (74 screws, age: 63.78 ± 13.57 years, female/male: 14/23 patients, body mass index: 23.11 ± 2.53, fused segments: 1–4 levels, revision: 38%) were included. S2AS loosening and lumbosacral nonunion were observed in 18 screws (13%) and 8 patients (22%) respectively. Only 35 screws (47%) were inserted accurately in our classification. Short, lateral perforation, and anterior perforation were observed in 14 screws (19%), 22 screws (30%), and 3 screws (4.1%). SIJ deviation was seen in 15 screws (20%) Factors associated with S2AS loosening were older age (P = 0.038), fusion levels (P = 0.011), and SIJ deviation (P < 0.001). S2AS loosening affects S1 pedicle screw (S1PS) loosening (P = 0.001). Furthermore, S2AS loosening is a risk factor for lumbosacral nonunion (P = 0.046). S2AS insertion under fluoroscopy is inaccurate. S2AS loosening induces S1PS loosening and lumbosacral nonunion. Surgeons should avoid deviating to SIJ, especially in older patients and relatively longer fusion. [ABSTRACT FROM AUTHOR]

Introduction: This in vitro study aims to biomechanically evaluate the influence of medium contamination for example, saliva, blood, chlorhexidine (liquid and gel), and fluoride mouthwash on the biomechanical behavior of implant abutments' screws under static and dynamic loading. Methods: Forty five Ti6Al4V commercial dental implants and abutments were tested in this study. Two main mechanical tests were carried out in the selected media. The first, static, aimed to evaluate the torque loss after the first tightening. The second, dynamic, involved a random cyclic load range between 0 and 200 N to evaluate torque loss due to mastication. In addition, metallographic longitudinal and cross‐sections of the abutment‐implant apparatus were examined to evaluate the abutment screw–abutment‐implant interface. Results: The static torque test showed that irrespective of the media, no statistical difference in static torque loss was found prior to dynamic loading. For the dynamic tests, torque‐angle evolution analysis during tightening to 30 Ncm and after the spectrum loading, showed the same global mechanical behavior for all media, but the statistical analysis indicated a difference between the groups in reverse torque values (RTV) and in the torque loss due to dynamic loading. The medium groups CHX, CHX‐gel, and Fluoride mouthwash, showed a meaningful torque loss due to loading, but the medium groups, control (no medium), blood and saliva showed an opposite trend and required a higher torque to open the abutment screws. The microstructural analysis revealed clear signs of cold‐welding/galling, post‐dynamic loading in these latter groups. Conclusions: The presence of lubrication/contamination media (CHX mouthwash/CHX‐gel/Fluoride mouthwash) reduces the preload generated due to tightening but prevents damage due to galling. The observed reduction of RTV clearly emphasizes the need for frequent abutment screw retightening for implant‐supported prosthetic long‐term stability. [ABSTRACT FROM AUTHOR]

The adequacy of screw anchorage is a critical factor in achieving successful spinal fusion. This study aimed to use machine learning algorithms to identify critical variables and predict pedicle screw loosening after degenerative lumbar fusion surgery. A total of 552 patients who underwent primary transpedicular lumbar fixation for lumbar degenerative disease were included. The LASSO method identified key features associated with pedicle screw loosening. Patient clinical characteristics, intraoperative variables, and radiographic parameters were collected and used to construct eight machine learning models, including a training set (80% of participants) and a test set (20% of participants). The XGBoost model exhibited the best performance, with an AUC of 0.884 (95% CI: 0.825-0.944) in the test set, along with the lowest Brier score. Ten crucial variables, including age, disease diagnosis: degenerative scoliosis, number of fused levels, fixation to S1, HU value, preoperative PT, preoperative PI-LL, postoperative LL, postoperative PT, and postoperative PI-LL were selected. In the prospective cohort, the XGBoost model demonstrated substantial performance with an accuracy of 83.32%. This study identified crucial variables associated with pedicle screw loosening after degenerative lumbar fusion surgery and successfully developed a machine learning model to predict pedicle screw loosening. The findings of this study may provide valuable information for clinical decision-making. [ABSTRACT FROM AUTHOR]

Objectives Diabetes mellitus (DM) is correlated with poor clinical outcomes in spinal surgery. However, the effect of it on screw stabilization has not been investigated. The aim of this study was to evaluate the screw loosening rate and postoperative outcomes in diabetic patients and to identify potential risk factors associated with loosening. Methods This was a retrospective study. Two hundred and forty‐three patients who received cervical or lumbar internal fixation between 2015 and 2019 were enrolled. Screw loosening was assessed on radiography, and clinical outcomes were evaluated by the improvement of visual analogue scale (VAS), Oswestry disability index (ODI) or Japanese Orthopaedic Association (JOA) scores. The relationship of DM, screw loosening and clinical outcomes were analyzed with chi‐square tests and regression analyses. Results One hundred and twenty‐two patients (50.2%) with diabetes were included in this study. Diabetes led to the increase of the rate of screw loosening in the lumbar spine, while the loosening rate did not vary significantly in the cervical spine. The occurrence of screw loosening in the lumbar spine was more likely to be associated with clinical outcomes for motor performance including walking and sitting. However, no significant effect on JOA and VAS scores in the cervical spine of screw loosening was found. Moreover, the history of DM affected the outcomes of the patients who underwent spinal surgery. Conclusion DM had an adverse effect on screw stabilization. The impaired improvement of clinical outcomes in diabetics after spinal surgery was related to screw loosening. In addition to the direct effects on operative wounds and neural function, the impact on the screws due to DM was also worth noting.

Objective To develop a novel semi‐cannulated lateral mass screw (SC‐LMS) for cervical posterior fixations and compare the fixation stability and safety of SC‐LMS with regular solid lateral mass screw (S‐LMS) in bone cement augmentation and pullout strength using fresh cadaveric cervical vertebrae. Methods The conventional multiaxial screw for cervical lateral mass fixation was modified to a cannulated screw with two lateral holes, used for bone cement injection in situ. Eight fresh human cervical vertebrae (C3, C4, and C5) were collected and used. μCT scan was performed to evaluate the bone quality of the lateral masses, including bone mineral density (BMD), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp). SCLMS or S‐LMS were randomly inserted into the paired cervical vertebrae and pulled out as a screw loosening model. These screws were reinserted in with bone cement augmentation, scanned by μCT to obtain the bone cement distribution along the screws, and pulled out to test the screw purchase strength. Results Fmax values exhibited strong positive correlations with the local BMD (𝑟 = 0.8640, p

Objective. To analyze the effectiveness and safety of using an orthobiological product in osteoplasty of bone defects of the vertebrae with simultaneous reosteosynthesis. Material and Methods. The results of screw augmentation technology using thrombogel-enriched allogeneic bone were studied in a retrospective, single-center, non-randomized study, which included 17 patients (10 women, 7 men) with instability of the hardware in the form of screw loosening and osteolysis around screws. Results within 12 months were followed up in 17 patients (100 %). We compared preoperative and postoperative instrumental data, clinical parameters in dynamics. Results. The mean age of the patients was 59 (43–75) years. The distribution of patients, according to the primary pathology, was as follows: 11 patients (64.7 %) had a degenerative-dystrophic pathology of the spine, 4 patients (23.5 %) had a traumatic injury, and 2 patients had a kyphotic deformity on the background of Bechterew’s disease (11.8 %). The mean time from primary to revision surgery was 7.06 months (3.1–12.1), mean CRP was 4.48 (0.5–15.0). When observing patients for 12 months, all patients showed a positive trend in the form of a statistically significant regression of back pain according to VAS from 7.0 (6.0; 7.3) to 1.0 (0.0; 1.0) points (χ2 = 47.9, df 3, р < 0.0001). A positive trend was also noted in the form of a decrease in ODI indicators and an improvement in the quality of life of patients from 63.8 (57.1; 69.1) to 3.0 (2.0; 7.5) at 12 months. When comparing the parameters (VAS and ODI), the obtained differences before/after the operation were statistically significant, while these changes have a pronounced correlation. Postoperative CT studies (3, 6, 12 months) showed no instability of the screws. Conclusion. Osteoplasty of vertebral bone defects and screw augmentation using orthobiological approaches have demonstrated their primary efficacy and safety. Further studies with a large sample size are needed to confirm the obtained results.

Background: Surgical treatment of midshaft clavicle fractures is associated with quick recovery and low risk of non-union. However, fixation failure may occur in case of severe comminution fractures. Moreover, clinical outcomes may be affected when clavicle fractures occur in combination with other injuries, particularly those involving the lower extremities, as the use of crutches or walkers may hinder the process of rehabilitation by adding strain on the acromioclavicular (AC) joint, resulting in possible fixation failure. This study aims to identify risk factors for fixation failure of midshaft clavicle fractures and elucidate the role of combined fractures in treatment outcomes. Methods: This study included patients diagnosed with midshaft clavicle fractures who underwent initial surgery between January 2012 and November 2021 at a designated regional trauma center hospital. Retrospective evaluation of fixation failure was carried out in 352 patients with midshaft clavicle fractures using standard clinical evaluation protocols and conventional radiographs. The prevalence of fixation failure and the effects of several demographic variables on the risk of fixation failure and non-union were examined. Multivariate logistic regression analysis was carried out to identify independent risk factors for fixation failure. Results: Fixation failure occurred in 40 patients (11.4%). Multivariate analysis identified comminution [odds ratio (OR) 3.532, p value = 0.003, 95% confidence interval (CI) 1.55–8.05)] and fewer number of screws (OR 0.223, p value = 0.022, 95% CI 0.06–0.80) as risk factors for fixation failure. Surgical techniques using wire cerclage reduced the chances of fixation failure in comminuted fractures (OR 0.63, p value = 0.033, 95% CI 0.05–0.80). Combined fractures that required rehabilitation using walkers or crutches increased the risk of non-union (OR 19.043, p value = 0.032, 95% CI 1.28–282.46). Conclusions: Additional fixation of comminuted fractures using cerclage can reduce the risk of treatment failure, while multiple fractures or rehabilitation for ambulation increases the risk of the same. Level of evidence: III. [ABSTRACT FROM AUTHOR]

Objectives: Diabetes mellitus (DM) is correlated with poor clinical outcomes in spinal surgery. However, the effect of it on screw stabilization has not been investigated. The aim of this study was to evaluate the screw loosening rate and postoperative outcomes in diabetic patients and to identify potential risk factors associated with loosening. Methods: This was a retrospective study. Two hundred and forty‐three patients who received cervical or lumbar internal fixation between 2015 and 2019 were enrolled. Screw loosening was assessed on radiography, and clinical outcomes were evaluated by the improvement of visual analogue scale (VAS), Oswestry disability index (ODI) or Japanese Orthopaedic Association (JOA) scores. The relationship of DM, screw loosening and clinical outcomes were analyzed with chi‐square tests and regression analyses. Results: One hundred and twenty‐two patients (50.2%) with diabetes were included in this study. Diabetes led to the increase of the rate of screw loosening in the lumbar spine, while the loosening rate did not vary significantly in the cervical spine. The occurrence of screw loosening in the lumbar spine was more likely to be associated with clinical outcomes for motor performance including walking and sitting. However, no significant effect on JOA and VAS scores in the cervical spine of screw loosening was found. Moreover, the history of DM affected the outcomes of the patients who underwent spinal surgery. Conclusion: DM had an adverse effect on screw stabilization. The impaired improvement of clinical outcomes in diabetics after spinal surgery was related to screw loosening. In addition to the direct effects on operative wounds and neural function, the impact on the screws due to DM was also worth noting. [ABSTRACT FROM AUTHOR]

Study Design: Retrospective cohort study. Objectives: Pelvic fixation in degenerative spinal deformation is as crucial as demanding. Several pelvic anchoring technics have been described, but loosening rates remain high for most solutions. Here is described the "Kappa" technic, combining ilio-sacral screws to S2A1 screws at 2 years of follow-up. Methods: Thirteen patients that underwent a spinal deformity correction with "Kappa" fixation to the pelvis and with more than 2 years of follow-up were prospectively included in this study. The surgical technic is described, and clinical and radiographic data have been collected for all patients. Results: The population exhibited an important pre-operative sagittal imbalance (mean SVA of 104,4 mm, mean PI-LL mismatch of 22,8°) that had improved significatively after surgery (mean SVA of 75,5 mm and mean PI-LL mismatch of 4,9°). No loosening of pull-out of the implants was to deplore at 2 years of follow-up. Conclusions: The association of ilio-sacral screw, resistant to pull-out because of the traction axis perpendicular to the construct, to S2A1 screws, known to be effective in sagittal balance restoration seems to be an effective and safe option to pelvic fixation for adult spinal deformity correction. Level of Evidence: IV. [ABSTRACT FROM AUTHOR]

Objective: To develop a novel semi‐cannulated lateral mass screw (SC‐LMS) for cervical posterior fixations and compare the fixation stability and safety of SC‐LMS with regular solid lateral mass screw (S‐LMS) in bone cement augmentation and pullout strength using fresh cadaveric cervical vertebrae. Methods: The conventional multiaxial screw for cervical lateral mass fixation was modified to a cannulated screw with two lateral holes, used for bone cement injection in situ. Eight fresh human cervical vertebrae (C3, C4, and C5) were collected and used. μCT scan was performed to evaluate the bone quality of the lateral masses, including bone mineral density (BMD), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp). SCLMS or S‐LMS were randomly inserted into the paired cervical vertebrae and pulled out as a screw loosening model. These screws were reinserted in with bone cement augmentation, scanned by μCT to obtain the bone cement distribution along the screws, and pulled out to test the screw purchase strength. Results: Fmax values exhibited strong positive correlations with the local BMD (푟 = 0.8640, p < 0.0001) and Tb.Th (푟 = 0.6795, p = 0.0038), whereas a negative correlation with Tb.Sp (푟 = −0.5567, p = 0.0251). A significant difference was observed between the Fmax before and after PMMA injection on the SC‐LMS side (p = 0.019). The SC‐LMS exhibited lower risk of cement leakage than S‐LMS after PMMA injection, and a positive correlation was observed between 퐹max and the distribution volumes on the SC‐LMS side. Conclusion: The novel SC‐LMS provides more robust fixation stability and is safer than the S‐LMS for PMMA augmentation, which may be related to the cement‐screw‐cement‐bone complex formation. [ABSTRACT FROM AUTHOR]

Background: Dental implant abutment screw loosening is an increasingly common problem, as evidenced by multiple studies that have investigated its causes. The objective of this study was to compare the screw loosening torque values before and after cyclic loading and to determine whether they are affected by the CAD/CAM abutment manufacturing technique (machined or laser-sintered) and abutment angulation. Materials and Methods: Ninety implants were used and divided into two groups: 45 implants received machined abutments (group A) and 45 implants received laser-sintered abutments (group B). Each group was further divided into three subgroups, with 15 implants each, based on the abutment angulation involved (0°, 15° and 20°). The abutments were tightened to the torque recommended by the manufacturer, and the reverse torque value was measured before and after cyclic loading (300,000 cycles). Data analysis was performed using one-way ANOVA and Wilcoxon signed-rank tests. Results: Statistically significant differences were observed between the laser-sintered and machined groups (p < 0.01). Additionally, differences were observed between subgroups with different angulations for both machined (16.2 ± 1.75, 14.7 ± 1.74 and 13.4 ± 1.08 Ncm) and laser-sintered abutments (14.6 ± 1.25, 12.7 ± 1.2 and 11.1 ± 1.35 Ncm) (0°, 15° and 20°, respectively). Conclusions: The final screw loosening torque after cyclic loading was lower than the initial loosening torque. Both abutment angulation and the CAD/CAM manufacturing method exerted a statistically significant influence on the final loosening torque. The abutment angulation factor was estimated to have an influence of 34.5%, while the abutment manufacturing method was estimated to have an influence of 21%.

Screw loosening is a widely reported issue after spinal screw fixation and triggers several complications. Biomechanical deterioration initially causes screw loosening. Studies have shown that incomplete insertion of pedicle screws increases the risk of screw breakage by deteriorating the local mechanical environment. However, whether this change has a biomechanical effect on the risk of screw loosening has not been determined. This study conducted comprehensive biomechanical research using polyurethane foam mechanical tests and corresponding numerical simulations to verify this topic. Pedicle screw-fixed polyurethane foam models with screws with four different insertion depths were constructed, and the screw anchoring ability of different models was verified by toggle tests with alternating and constant loads. Moreover, the stress distribution of screw and bone-screw interfaces in different models was computed in corresponding numerical mechanical models. Mechanical tests presented better screw anchoring ability with deeper screw insertion, but parameters presented no significant difference between groups with complete thread insertion. Correspondingly, higher stress values can be recorded in the model without complete thread insertion; the difference in stress values between models with complete thread insertion was relatively slight. Therefore, incomplete thread insertion triggers local stress concentration and the corresponding risk of screw loosening; completely inserting threads could effectively alleviate local stress concentration and result in the prevention of screw loosening.

BackgroundIt is supposed that additional posterior fusion may provide additional stability of the pedicle screw; however, the clinical impact of additional posterior fusion in patients treated with TLIF remains uncertain. The objective of this study is to assess the clinical efficacy of circumferential fusion in patients treated with TLIF.Materials and methodsThis is a single-center retrospective evaluation of consecutive 179 patients with degenerative lumbar stenosis and instability of spinal segments. Patients with axial pain and neurogenic claudication or radiculopathy associated with spinal stenosis were enrolled during the period from 2012 to 2018. Transforaminal lumbar interbody fusion (TLIF) with a single cage was used to treat patients. In 118 cases a supplementary posterior fusion was made. The duration of follow-up accounted for 24 months, logistic regression analysis was used to assess factors that influence the complication rate.ResultsThe rate of pedicle screw loosening was growing with radiodensity getting decreased and was more frequent in patients with two level fusion. An increase in pedicle screw loosening rate correlated with anterior nonunion Tan 2 and 3 grade while both posterior complete and incomplete fusion resulted in a decline in the complication rate. Lumbosacral fusion, bilateral facet joints` resection and laminectomy turned out to be insignificant factors. The overall goodness of fit of the estimated general multivariate model was χ2 = 87.2230; P

The key for the long-term success of dental implants is the mechanical stability of the implant and the abutment anchored in it. The conical connection between screwed dental implants and abutments has good mechanical stability. However, with long-term use of the dental restoration fixed on a dental implant in the oral cavity, mechanical deformation of the assembled abutment in the implant and loosening of the fixing screw often occur, which affects long-term functionality. To study these processes, static compression loading tests were performed with various conical angle connections (35°, 55°, 75° and 90°) using Grade 4 and 5 titanium implant materials. After loading the implant and abutment assemblies with up to 500 N, the resulting deformations in length and diameter as well as the reverse-torque of the fixing screw were measured. No significant differences were observed between the results when the tested implant and abutment material was either Grade 4 or 5. Additionally, dynamic compression tests were performed on Grade 4 samples with different conical angles (30°, 45° and 60°). The relative changes in length (strain) of the assembly were determined over 30,000 cycles due to force varying periodically between 100 and 400 N. The reverse torques were also measured after the dynamic loading. The static and dynamic compression tests showed the same trend for different cone angles. Impression of the abutment into the dental implant was observed for lower conical angle connections. On the other hand, lower strain values were observed at larger conical angles. The reverse torque values of the fixing screws were only the half of the forward torque in case of lower conical angles, while high stability was observed with the larger conical angle connections (~ 20-30% reduction in torque). In summary, it is recommended to use a higher angle of the conical connection in order to avoid larger deformations in the lengths and diameters of the assembled implant and abutment system, as well as a significant reduction in the torque of the fixing screw. [ABSTRACT FROM AUTHOR]

This in vitro study evaluated the mechanical behavior of different conical connection implant systems after abutment screw withdrawal. Four conical connection systems were selected based on different conical half-angles: Ankylos (5.7°), Cowell (7.0°), Straumann (7.5°), and Astra (11.0°). In each system, 5 implants and abutments were used (n = 5). According to the recommended value, each abutment screw was torqued to settle the abutment and then withdrawn through a predesigned hole of the cemented crown. The retentiveness of the abutment was evaluated by the following mechanical testing. All specimens were subjected to cyclic loading of 20–200 N, 30°, and 4-mm off-axis to the implant axis, for 106 cycles. The pullout forces and axial displacements of the abutments were measured. The data of the Cowell system was obtained from our previous work. All groups other than Astra group, in which abutment loosened after abutment screw withdrawal, passed the cyclic loading test. Straumann group demonstrated a significantly lower pullout force (27.4 ± 21.1 N) than Ankylos (160.1 ± 41.4 N) and Cowell (183.7 ± 30.5 N) groups. All groups showed abutment rebound after screw withdrawal except Straumann group. In addition, Ankylos, Cowell, and Straumann groups demonstrated axial displacement after cyclic loading. In terms of the retentiveness of the abutment after abutment screw withdrawal examined in this study, Ankylos and Cowell groups had much higher retentiveness than Straumann group, while Astra group had none. Conical angle could be a key design parameter to make abutment screw withdrawal after conical abutment settlement feasible, but more studies must be conducted for clinical application. [ABSTRACT FROM AUTHOR]

Purpose: Though, mechanical dental implant and supported prosthesis failures are considered significant, a comprehensive evaluation is lacking. A systematic review analyzing different aspects related to such failures was therefore done. Methods: - Electronic search was carried out in PubMed/MEDLINE and Cochrane Library for articles published between 1981 and 2021. Articles were selected using predefined criteria. Data extraction was based on mechanical complications associated with dental implants, prosthetic implant failures, survival rate of implants, mechanical failure of implants placed in the maxilla and mandible, and mechanical complications associated with implant supported over dentures. Quality of included studies was assessed. Meta-analysis for heterogenicity testing, publication bias and implant failure assessment was conducted using MedCalc® Statistical Software version 19.7. Results: - Eighteen retrospective and prospective studies were included following PRISMA guidelines. Mechanical complications were more in the initial 9 years but reduced later. Abutment screw loosening was one of the more common mechanical complications (16.21%). Maxillary implant failure was greater compared to mandibular implant failure with an odds ratio of 4.66 (95% CI -3.21- 6.75). Failure of implant supported overdentures due to mechanical complications were 3% in the fixed effect, and 2.9% in the random effect model (P

Objective Pedicle-based dynamic stabilization (DS) has gained popularity outside of America. Although pedicle screw (PS) loosening has always been a concern, it is reportedly innocuous. Cortical bone trajectory (CBT) screw is an emerging option with less invasiveness and similar effectiveness to PS in short-segment lumbar fusion. This study aimed to verify the use of CBT for DS by comparing the outcomes between pedicle- and CBT-based DS. Methods Consecutive patients with lumbar spondylosis or low-grade spondylolisthesis who underwent 1- or 2-level DS between L3–5 with a minimum follow-up of 24 months were reviewed. Screw loosening was determined by computed tomography and the incidences were compared. Results A total of 291 patients who underwent Dynesys DS (235 pedicle- and 56 CBT-based, respectively) were compared. The demographics and preoperative conditions were similar. All the clinical outcomes improved at 24-month postoperation, while the CBT-based group had less operation time and blood loss than the pedicle-based group. The rates of screw loosening were lower in the CBT-based (5.4% per screw and 12.5% per patient) than the pedicle-based group (9% per screw and 26.4% per patient). Furthermore, there were no differences in the clinical outcomes and complication profiles. Conclusion The CBT-based DS for 1- or 2-level lumbar degeneration demonstrated equivalent clinical improvement as the pedicle-based DS. The adaption of CBT-based screws for DS could be a less invasive approach (shorter operation time and less blood loss), with lower chances of screw loosening than the conventional PS-based DS.

Objective Although pedicle screws are widely used to reconstruct the stability of the spine, screw loosening is a common complication after spine surgery. The main objective of this study was to investigate whether the application of the hollow lateral hole structure had the potential to improve the stability of the pedicle screw by comparing the biomechanical properties of the novel lateral hole pedicle screws (LHPSs) with those of the solid pedicle screws (SPSs) in beagle dogs. Methods The cancellous bone of the distal femur, proximal femur, distal tibia, and proximal tibia were chosen as implantation sites in beagle dogs. In each of 12 dogs, four LHPSs, and four SPSs were implanted into both lower limbs. At 1, 2, and 3 months after surgery, four dogs were randomly sampled and sacrificed. The LHPS group and SPS group were subdivided into four subgroups according to the length of their duration of implantation (0, 1, 2, 3 months). The biomechanical properties of both pedicle screws were evaluated by pull‐out and the cyclic bending tests. Results The results of the study showed that no significant difference was found between LHPSs (276.62 ± 50.11 N) and SPSs (282.47 ± 42.98 N) in pull‐out tests at time 0 (P > 0.05). At the same time point after implantations, LHPSs exhibited significantly higher maximal pullout strength than SPSs (month 1: 360.51 ± 25.63 vs 325.87 ± 28.11 N; month 2: 416.59 ± 23.78 vs 362.12 ± 29.27 N; month 3: 447.05 ± 38.26 vs 376.63 ± 32.36 N) (P 0.05). Conclusions The pedicle screw with the hollow lateral hole structure could allow bone to grow into the inner architecture, which improved biomechanical properties by extending the contact area between screw and bone tissue after implantation into the cancellous bone. It indicated that LHPS could reduce loosening of the pedicle screws in long term after surgery.

Introduction: Pedicle screws (PSs) or lateral mass screws (LMSs) are used in posterior cervical spine fixation. The former are more firmly fixed but are associated with the risk of neurovascular injury and should be inserted using intraoperative imaging or navigation, which may prolong the surgical duration and is not feasible in all hospitals. This prospective clinical study aimed to evaluate the outcomes of LMS insertions without fluoroscopic guidance and screw loosening rates at 6 months postoperatively using computed tomography (CT). Methods: We examined 38 patients who underwent posterior cervical spine fusion using 206 LMSs in the C3-C6 range between January 2018 and July 2021. The direction of screw insertion followed the Magerl method, and we inserted screws as bicortically as possible without intraoperative imaging. The screw position was examined using CT at 1 week postoperatively. Screw insertion angles, bicortical insertion rate, facet violation, and neurovascular injury were evaluated. Screw loosening with unicortical and bicortical screws (US and BS, respectively) was investigated using CT at 6 months postoperatively. Results: The average LMS length was 14.1 mm. The average axial and sagittal angles were 33.9° and 29.2°, respectively. Among the 206 LMSs inserted, 167 were BS; of these, 94.6% had screw length protrusion of 0-2 mm. Facet violation was observed in 3.4% of all screws but without neurovascular injury. Six months postoperatively, loosening of 25 screws (12.1%) occurred, including 17 (18.3%) USs and 8 (8.39%) BSs. The screw loosening rate was significantly higher in US than for BS (43.6% [17/39] vs. 4.8% [8/167], P

Anterior cervical discectomy and fusion (ACDF) is a commonly performed procedure for degenerative cervical spine disease. Rare complications of ACDF surgery include hardware failure, in the form of screw loosening and migration, or rod breakage. We present a case in which we removed a migrated screw lodged in the esophagus from a patient with a failed anterior cervical fusion. To present a surgical technique and considerations to remove a migrated screw. The previous ACDF incision was reopened and exposure was gained under the guidance of a head and neck surgeon. Longus coli were mobilized off the spine bilaterally with electrocautery. After dissection, the screw was found lodged in the longitudinal muscle of the esophageal wall and excised with the use of a 15-blade. The integrity of the esophageal mucosa and submucosa was maintained and subsequently checked with rigid esophagoscopy. Fluoroscopy was used to confirm that all hardware was removed, with the exception of the anterior cages. The dislodged screw, which was embedded in the esophagus, was successfully removed. Failure of an ACDF carries a risk of screw migration, which may be asymptomatic even if the screw is lodged in the esophagus. Additional considerations are required with potential violations of the adjacent viscera. [ABSTRACT FROM AUTHOR]

• We showed the method of measuring Hounsfield units (HU) of S1 screw trajectory. • HU of the L1 vertebral body and S1 screw trajectory could predict screw loosening. • We should insert S1 screws in an area with a high HU value in S1. We investigated whether computed tomography (CT) Hounsfield unit (HU) values of the S1 screw trajectory can predict screw loosening after lumbosacral fixation. We analysed 102 patients (58 men and 44 women) who underwent L5–S1 interbody fusion between April 2018 and October 2019. We reviewed the characteristics of patients including body mass index, smoking, comorbidity with diabetes mellitus, and interbody fusion types. Bone mineral density (BMD) was obtained from the lumbar spine and total hip using dual-energy X-ray absorptiometry. Additionally, we reviewed the S1 screw lengths and diameters. HU values of both L1 vertebral bodies and bilateral S1 screw trajectories were measured on preoperative CT. At six months postoperatively, S1 screws on CT were assessed. Screws with a 1 mm or more radiolucent zone were defined as "loosening". Seventeen patients had loosened screws, and 85 patients did not. The patient characteristics did not significantly differ between the two groups. Both total hip BMD and L1 HU values were low in the loosening patient group (both p = 0.03). Of the 204 total S1 screws, 25 screws were loosened, and 179 screws were not. The screw length was short (p = 0.01), and the HU value of the S1 screw trajectory was low (p < 0.001) in the loosening screw group. Based on receiver operating characteristic analyses of these factors, the area under the curve of HU value of the S1 screw trajectory was the highest (0.79). Measuring the HU value of both the L1 vertebral body and S1 screw trajectory aids in predicting screw loosening. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study was to evaluate and compare the effect of plasma nitride-treated abutment screws of two different implant systems on screw loosening and surface topography with and without thermocycling. Settings and Design: This was an in-vitro experimental study. Materials and Methods: Fifty-two abutment screws (Group A: 26 Genesis and Group B: 26 Bredent) underwent plasma nitride treatment and were subdivided into two groups, one without thermocycling and one with thermocycling. Dynamic load was applied and detorque values were evaluated for determining the screw loosening using "independent t-test" with the help of IBM SPSS Statistics 20 and scanning electron microscopy was done to check for surface topography. Statistical Analysis Used: Inter- and intragroup comparisons were done using independent t-test (SPSS: Statistical Package for the Social Sciences software version 20). Results: Plasma nitriding treatment genesis implant system abutment screw showed more screw loosening (P < 0.05) and surface roughness as compared to bredent with and without thermocycling. Conclusion: From the present study, it was shown that plasma nitride-treated abutment screws decreased the occurrence of screw loosening favoring the bredent implant--abutment system more than the genesis implant--abutment system. [ABSTRACT FROM AUTHOR]