Screw Density Research Articles

Influence of implant density on mechanical complications in adult spinal deformity surgery.

The purpose was to analyze how rod characteristics, screw density and cages influence the incidence of mechanical complications compared to patient-related factors and alignment in adult spinal deformity instrumented T9-T11 to pelvis. Register data of 302 patients was analyzed. Relative lumbar lordosis (RLL) and relative sagittal alignment (RSA) was measured. Surgical data included rod characteristics, pedicle screw density and interbody cages. Univariate and multivariate logistic regression models were used. Pseudarthrosis occurred in 24.1%. On univariate analysis Odds Ratio (OR) was 0.74 for ≥ 3 cages (p = 0.452), 0.48 for 4 rods (p = 0.008), 4.30 for high screw density (p = 0.001). Patient-related factors were non-significant. Multivariate OR was 0.59 for 4 rods (p = 0.084) and 4.67 for high screw density (p = 0.005). PJK/PJF occurred in 19.2%. Age > 60 had an OR 2.83 (p = 0.023), postoperative RSA malaligned OR 2.84 (p = 0.030), severely malaligned OR 6.54 (p < 0.001). Implant characteristics were non-significant. Multivariate OR was 1.26 for age > 60 (p = 0.657), 2.32 for malaligned RSA (p = 0.097), 5.69 for severely malaligned RSA (p = 0.001). Screw loosening occurred in 8.9%. Univariate OR was 0.95 for ≥ 3 cages (p = 0.920), 1.64 for 4 rods (p = 0.235), 0.25 for high screw density 1.5-2 (p = 0.011). Patient-related factors were non-significant. Multivariate OR for high screw density was 0.23 (p = 0.022). Four rods decrease the pseudarthrosis risk. Cages have a secondary role. High screw density doesn't prevent from pseudarthrosis. Postoperative malalignment is the main PJK/PJF risk factor. Age plays a secondary role. Implant characteristics have a minor influence. High screw density constructs have a lower risk for screw loosening. 3-Retrospective register study.

Achievements and complications related to final fusion surgery in early onset scoliosis at the end of "traditional dual growing rod mission".

Retrospective cohort study. Assess the outcomes of final fusion in early onset scoliosis patients treated with TDGR, particularly with acceptable coronal and sagittal alignment at the end of their growing age. Early onset scoliosis (EOS) poses challenges due to the need for managing spinal deformities while accommodating trunk growth. The dual growing rod (TDGR) technique, a traditional approach, aims to address these concerns by periodic lengthening until spinal growth ceases. Recent shifts propose observation without immediate implant removal after achieving spinal alignment, raising questions about the necessity of final fusion surgery. This retrospective study included 22 EOS patients treated with TDGR who underwent final fusion surgery. Clinical and radiological data were analyzed, including pre- and post-surgery measurements, complications, surgical approaches, and screw density. Patients (average initial surgery age: 6.9years) exhibited significant reductions in main curve angle (preoperative: 65.8°, pre-fusion: 49.1°, post-fusion: 36.3°) and thoracic kyphosis (preoperative: 47°, pre-fusion: 46.6°, post-fusion: 38.7°). Complications included one surgical site infection and four transient intraoperative neuro-monitoring Impairment. High screw density correlated with lower total correction. Final fusion surgery post-TDGR treatment shows promise in correcting EOS-associated deformities. Surgeons and parents should be aware of the procedure's complexity and potential complications.

Axial rod slip at the end-of-construct screw in scoliosis surgery: relevance, occurrence and prevention

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

Comparison Between Resident and Attending Surgeons as Assistants on Adolescent Idiopathic Scoliosis Surgery: No Differences in Outcomes, Complications Rate, or Pedicle Screw Placement Accuracy.

Retrospective cohort study. The aim of the present study was to determine if the level of training of the first assistant (resident or attending surgeon) has an influence on the radiographic outcome of AIS surgery and on the accuracy rate of the pedicle screws placement. Adolescent idiopathic scoliosis (AIS) surgery is a challenging procedure that requires a dedicated team of skilled professionals. Therefore, understanding the learning curve is of outstanding importance to guarantee the best outcomes and the highest safety to the patients. A retrospective analysis of patients who underwent surgery for AIS with a minimum follow-up of 2 years was conducted. All patients were operated by an experienced spine surgeon, assisted by and attending surgeon (group A) or a senior resident (group B). Radiographic outcomes were assessed. Through postoperative CT scan, accuracy of pedicle screw placement was measured (using Gertzbein-Robbins classification). Groups were then statistically compared. A total of 120 patients were included (mean age 15.3±3.39y, major curve Cobb 60.7±11.9 degrees). No difference was found between groups in terms of preoperative characteristics and postoperative radiographic (correction rate, thoracic kyphosis, screw density) outcomes or complications. Operative time and estimated blood loss were significantly higher in Group B (P=0.045 and P=0.024, respectively). Of the 2746 pedicle screws inserted (1319 group A and 1427 group B), 2452 had a perfect intrapedicular trajectory (absolute accuracy of 89.29%) and 2697 had a breach <2mm (relative accuracy of 97.56%). No difference was found among groups in terms of absolute or relative accuracy (P=0.06 and P=0.23, respectively). AIS cases assisted by senior residents have longer operative time and higher blood loss, but this does not negatively affect the overall radiographic outcome and does not place the patient at increased risk of complications. III.

The effectiveness of a low implant density in Scheurmann kyphosis in correcting the lumbar lordosis -pelvic incidence mismatch

Purpose To evaluate the effectiveness of using a low implant density in surgical treatment of Scheurmann Kyphosis (SK) in correcting the lumbar lordosis (LL)- Pelvic incidence (PI) mismatch. Methods Patients that were surgically treated for SK by a low screw density with multiple Ponte osteotomies at two institutions from January 2021 to January 2022 were identified and included in the study. Preoperative/postoperative/1- and 2-year follow-up measurements were analyzed from full-spine standing radiographs. Results Thirty patients were enrolled in our study, mean age 20.5 (13–37) years, mean preoperative kyphosis was 85.9 (75–108), a mean preoperative lumbar lordosis-pelvic LL-PI mismatch was 25.9 (23–28). The maximum kyphosis was corrected to 46.2 (37–63) and the LL-PI mismatch was reduced to 7.7. The correction was maintained at 1- and 2-years follow-up with no statistical change in the sagittal angles. Conclusion Surgical correction of SK using low-density implants and multiple Ponte osteotomies is an effective method of correcting the kyphotic deformity and reducing the LL-PI mismatch to normal physiological values.

Impact of bone density and integrated screw configuration on standalone anterior lumbar interbody construct strength

BackgroundIn anterior lumbar interbody fusion (ALIF), the use of integrated screws is attractive to surgeons because of the ease of implantation and no additional profile. However, the number and length of screws necessary for safe and stable implantation in various bone densities is not yet fully understood. The current study aims to determine how important both length and number of screws are for stability of ALIFs. MethodsThree bone models with densities of 10, 15, and 20 pounds per cubic foot (PCF) were chosen as surrogates. These were instrumented using the Z-Link lumbar interbody system with either 2, 3, or 4 integrated 4.5 × 20 mm screws or 4.5 × 25 mm screws (Zavation, LLC, Flowood, MS). The bone surrogates were tested with loading conditions resulting in spine extension to measure construct stiffness and peak force. ResultsThe failure load of the construct was influenced by the length of screws (p=.01) and density of the bone surrogate (p<.01). There was no difference in failure load between using 2 screws and 3 screws (p=.32) or when using four 20 mm screws versus three 25 mm screws (p=.295). ConclusionIn our study, both bone density and length of screws significantly affected the construct's load to failure. In certain cases where a greater number of screws are unable to be implanted, the same stability can potentially be conferred with use of longer screws. Future clinical studies should be performed to test these biomechanical results.

The Influence of Increased Pedicle Screw Diameter and Thicker Rods on Surgical Results in Adolescents Undergoing Posterior Spinal Fusion for Idiopathic Scoliosis.

Background: Modern surgical techniques allow for the correction of spinal deformity, stopping its progression and improving pain relief and social and physical functioning. These instruments have different implant designs, screws, and rod diameters and can be composed of different metal alloys with different hardnesses, which can have a significant impact on the effect of correcting spinal deformities. We designed a retrospective cohort study based on the same surgical technique and spine system using different implant sizes, and compared the results across them. Methods: This is a retrospective review of adolescent idiopathic scoliosis (AIS) patients who underwent posterior spinal fusion (PSF) between 2016 and 2022 with a minimum two-year follow-up (FU) using two spinal implant systems: 5.5 and 6.0 mm diameter screws with double 5.5 mm titanium rods (Group 1 (G1)), and 6.0 and 6.5 mm diameter pedicle screws with double 6.0 mm cobalt-chromium rods (Group 2 (G2)). The evaluated data were as follows: preoperative personal data, radiographic outcomes, complications, and health-related quality of life questionnaire (HRQoL). The parameters were reviewed preoperatively, after the final fusion, and during the FU. Results: The mean age of all 260 patients at surgery was 14.8 years. The average BMI was also similar in both groups and was noted as 21. The mean levels of fusion and screw density were similar in both groups. The mean preoperative major curves (MCs) were 57.6° and 62.5° in G1 and G2, respectively. The mean flexibility of the curves was noted as 35% in G1 and 33% in G2. After definitive surgery, the mean percentage correction of the MC was better in G2 vs. G1, with 74.5% vs. 69.8%, respectively (p < 0.001). At the final FU, the average loss of correction was 5.9° for G1 and 3.2° for G2 (p < 0.001). The mean preoperative (TK) thoracic kyphosis (T2-T5) was 12.2° in G1 and 10.8° in G2. It was corrected to 15.2° in G1 and to 13° in G2. At the FFU, we noted a significant difference in the TK (T2-T5) between the groups, with 16.7° vs. 9.6° for G1 vs. G2, respectively (p < 0.001). Statistical significance was observed between the preoperative sagittal balance and the final follow-up for both groups (p < 0.001). Conclusions: AIS patients surgically treated with screws with a larger diameter and thicker and stiffer rods showed greater correction and postoperative thoracic kyphosis without implant failure. The complication rates, implant density, and clinical outcomes remained similar. The radiographic benefits reported in this cohort study suggest that large-sized screws and stiffer rods for the correction of pediatric spinal deformities are safe and very effective.

A retrospective cohort analysis of failure and potential causes after osteosynthesis of femoral fractures with VA-LCP Condylar plate 4.5/5.0, Depuy Synthes

BackgroundSince 2014, the VA-LCP Condylar Plate 4.5/5.0, Depuy Synthes, has been the preferred implant for these injuries at our institution, however, speculations have been made whether it is more prone to failure compared to other implants. Thus, the aim of the study was to describe the cohort treated with the VA-LCP Condylar Plate 4.5/5.0, Depuy Synthes, at our department from 2014 to 2020, including the number of failures. Secondary, whether specific outcome measures were significantly overrepresented in the failure group. MethodsPatients were identified through the hospital database, and demographic data was extracted from patient files. X-rays were evaluated for injury type, osteosynthesis characteristics, and whether the construct failed during follow-up. Thanks to the national patient record database a minimum of patients was lost to follow-up. ResultsAfter exclusion 159 patients (165 osteosyntheses, descriptive part) and 108 patients (112 osteosyntheses, subgroup analysis) were eligible for inclusion. The VA-LCP Condylar Plate 4.5/5.0, Depuy Synthes, was used for most AO-type fractures and inserted as both neutralization, buttress, and bridging plates. Overall failure was seen in 8 % of osteosyntheses. Significantly more failures were seen in patients with increased Body Mass Index (BMI) (24 vs. 32, p = 0,046) and those treated for a periprosthetic fractures (41 % vs. 89 %, p = 0,005). We did not see an association between failure and plate length, bridge span, screw density or the degree of medial support. ConclusionThe VA-LCP Condylar Plate 4.5/5.0, Depuy Synthes is a versatile plate with failure rates comparable to previously reported studies. This study confirmed that elevated BMI may be a risk factor for failure, while other previously reported risk factors were not associated with failure in this study.

The effect of body weight on interfragmentary fracture strain in plate fixation of distal femur fractures: A finite element analysis

IntroductionDistal femur fractures are difficult to successfully treat due to high rates of nonunion. Obesity is an independent prognostic risk factor for nonunion. Advances in finite element analyses (FEAs) have allowed researchers to better understand the performance and behavior of constructs at the bone-implant interface under a variety of conditions. The purpose of this study is to determine the impact of body weight on fracture strain in a lateral locking plate construct for supracondylar femur fractures and whether additional construct rigidity is beneficial to optimize fracture strain in high body mass patients. HypothesisWe hypothesized that increased loads would produce a higher interfragmentary strain (IFS), which could be decreased by shortening the working length of the construct. Materials and methodsA 3D finite element analysis was performed on two separate femur models with a comminuted supracondylar distal femur fracture fixed with a lateral distal femoral locking plate in bridging mode with Ansys software. Axial forces were varied to recreate the effect of load from normal and high body mass patients. Working length and screw density of the construct were varied for each condition. Measurements of interfragmentary strain and shear motion (SM) were compared. ResultsDoubling the axial load from 70kg (control) to 140kg (high body mass) increased the interfragmentary strain by an average of 76% for the three working lengths (3.38%±1.67% to 4.37%±0.88% at the baseline working length (BWL), 1.42%±1.00% to 2.87%±2.02% at the intermediate working length (IWL) and 0.62%±0.22% to 1.22%±0.42% at the short working length (SWL)). On average, decreasing the working length in the 140kg load reduced the mean IFS to within 15% of the mean IFS of the 70kg load at the longer working length (2.87%±2.02% at IWL 140kg versus 3.38%±1.67% at BWL 70kg and 1.22%±0.45% SWL 140kg versus 1.42±1.00% IWL 70kg). DiscussionIncreased axial load increases interfragmentary strain in an AO/OTA 33A distal femur fracture fixed with a lateral distal femoral locking plate. Decreasing the working length of the fixation construct in the high body mass model decreased interfragmentary strain. Higher loading conditions reflective of high body mass patients should be considered in studies investigating optimization of fracture strain. Level of proofV; Finite Element Analysis (FEA).

Novel Screw Placement Method for Extremely Small Lumbar Pedicles in Scoliosis.

Study Design: Consecutive case series. Objective: To propose a screw placement method in patients with extremely small lumbar pedicles (ESLPs) (<2 mm) to maintain screw density and correction power, without relying on the O-arm navigation system. Summary of Background Data: In scoliosis surgery, ESLPs can hinder probe passage, resulting in exclusion or substitution of the pedicle screws with a hook. Screw density affects correction power, making it necessary to maximize the number of screw placements, especially in the lumbar curve. Limited studies provide technical guidelines for screw placement in patients with ESLPs, independent of the O-arm navigation system. Methods: We enrolled 19 patients who underwent scoliosis correction surgery using our novel screw placement method for ESLPs. Clinical, radiological, and surgical parameters were assessed. After posterior exposure of the spine, the C-arm fluoroscope was rotated to obtain a true posterior-anterior view and both pedicles were symmetrically visualized. An imaginary pedicle outline was presumed based on the elliptical or linear shadow from the pedicle. The screw entry point was established at a 2 (or 10) o'clock position in the presumed pedicle outline. After adjusting the gear-shift convergence, both cortices of the transverse process were penetrated and the tip was advanced towards the lateral vertebral body wall, where an extrapedicular screw was placed with tricortical fixation. Results: Out of 90 lumbar screws in 19 patients, 33 screws were inserted using our novel method, without correction loss or complications during an average follow-up period of 28.44 months, except radiological loosening of one screw. Conclusions: Our new extrapedicular screw placement method into the vertebral body provides an easy, accurate, and safe alternative for scoliosis patients with ESLPs without relying on the O-arm navigation system. Surgeons must consider utilizing this method to enhance correction power in scoliosis surgery, regardless of the small size of the lumbar pedicle.

Navigation-Assisted One-Staged Posterior Spinal Fusion Using Pedicle Screw Instrumentation in Adolescent Idiopathic Scoliosis-A Case Series.

Background and Objectives: Adolescent idiopathic scoliosis (AIS) is a prevalent three-dimensional spinal disorder, with a multifactorial pathogenesis, including genetics and environmental aspects. Treatment options include non-surgical and surgical treatment. Surgical interventions demonstrate positive outcomes in terms of deformity correction, pain relief, and improvements of the cardiac and pulmonary function. Surgical complications, including excessive blood loss and neurologic deficits, are reported in 2.27-12% of cases. Navigation-assisted techniques, such as the O-arm system, have been a recent focus with enhanced precision. This study aims to evaluate the results and complications of one-stage posterior instrumentation fusion in AIS patients assisted by O-arm navigation. Materials and Methods: This retrospective study assesses 55 patients with AIS (12-28 years) who underwent one-stage posterior instrumentation correction supported by O-arm navigation from June 2016 to August 2023. We examined radiological surgical outcomes (initial correction rate, loss of correction rate, last follow-up correction rate) and complications as major outcomes. The characteristics of the patients, intraoperative blood loss, operation time, number of fusion levels, and screw density were documented. Results: Of 73 patients, 55 met the inclusion criteria. The average age was 16.67 years, with a predominance of females (78.2%). The surgical outcomes demonstrated substantial initial correction (58.88%) and sustained positive radiological impact at the last follow-up (56.56%). Perioperative complications, including major and minor, occurred in 18.18% of the cases. Two patients experienced a major complication. Blood loss (509.46 mL) and operation time (402.13 min) were comparable to the literature ranges. Trend analysis indicated improvements in operation time and blood loss over the study period. Conclusions: O-arm navigation-assisted one-stage posterior instrumentation proves reliable for AIS corrective surgery, achieving significant and sustained positive radiological outcomes, lower correction loss, reduced intraoperative blood loss, and absence of implant-related complications. Despite the challenges, our study demonstrates the efficacy and maturation of this surgical approach.

Do low-density screws influence pelvic incidence in adolescent idiopathic scoliosis correction?

Low-density screw constructs yield significant radiographic and clinical improvements with reduced risk of neurological complications. This study aimed to investigate the relationship between coronal Cobb angle and pelvic incidence (PI) in the correction of adolescent idiopathic scoliosis (AIS) using a low-density construct, as well as the association between PI and functional outcomes. This prospective cohort study involved 60 posteriorly instrumented AIS patients, aged 10-16 years, with Cobb angles ranging from 45° to 90° of various Lenke types. Radiological assessments were conducted pre- and postsurgery at 1, 3, 6, 12, and 24 months. Functional evaluation utilized the Scoliosis Research Society score form (SRS-30). A positive correlation was observed between screw density and operation time, blood loss, and degree of correction with SRS change (P = 0.004). No correlation was found between screw density and hospital stay, loss of correction, correction rate, SRS change, change in PI, or Cobb angle. Correction of AIS through a posterior approach using a low-density construct can lead to satisfactory curve correction, impacting spinopelvic parameters. However, PI alone does not directly influence patient functional outcomes assessed by SRS-30. Low-density implant constructs reduce operative time, blood loss, costs, and complication risks.

Analysis of duration of different stages of surgery in posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS) patients: comparison between severe versus non-severe AIS.

Prolonged surgical duration in severe adolescent idiopathic scoliosis (AIS) patients is associated with increased blood loss and perioperative complications. The aim of this study was to compare the duration of each stage of posterior spinal fusion (PSF) in severe AIS (Cobb angle ≥ 90°) with non-severe AIS patients. This analysis will identify the most time-consuming stage of PSF and help surgeons formulate strategies to shorten operative time. Retrospective study whereby 90 AIS patients (Lenke type 2, 3, 4, and 6) who underwent PSF from 2019 to 2023 were recruited. Twenty-five severe AIS patients were categorized in Gp1 and 65 non-severe AIS patientsin Gp2. Propensity score matching (PSM) with one-to-one with nearest neighbor matching (match tolerance 0.05) was performed. Outcomes measured via operation duration of each stage of surgery, blood loss, number of screws, fusion levels and screw density. Twenty-five patients from each group were matched. Total operative time was significantly higher in Gp1 (168.2 ± 30.8 vs. 133.3 ± 24.0min, p < 0.001). The lengthiest stage was screw insertion which took 58.5 ± 13.4min in Gp1 and 44.7 ± 13.7min in Gp2 (p = 0.001). Screw insertion contributed 39.5% of the overall increased surgical duration in Gp1. Intraoperative blood loss (1022.2 ± 412.5 vs. 714.2 ± 206.7mL, p = 0.002), number of screws (17.1 ± 1.5 vs. 15.5 ± 1.1, p < 0.001) and fusion level (13.1 ± 0.9 vs. 12.5 ± 1.0, p = 0.026) were significantly higher in Gp1. Screw insertion was the most time-consuming stage of PSF and was significantly longer in severe AIS. Adjunct technologies such as CT-guided navigation and robotic-assisted navigation should be considered to reduce screw insertion time in severe AIS.

Risk factors of instrumentation failure after laminectomy and posterior cervical fusions (PCF)

BackgroundFor patients with multilevel degenerative cervical myelopathy, laminectomy and posterior cervical fusions (PCF) with instrumentation are widely accepted techniques for symptom relief. However, hardware failure is not rare and results in neck pain or even permanent neurological lesions. There are no in-depth studies of hardware-related complications following laminectomy and PCF with instrumentation.MethodsThe present study was a retrospective, single centre, observational study. Patients who underwent laminectomy and PCF with instrumentation in a single institution between January 2019 and January 2021 were included. Patients were divided into hardware failure and no hardware failure group according to whether there was a hardware failure. Data, including sex, age, screw density, end vertebra (C7 or T1), cervical sagittal alignment parameters (C2-C7 cervical lordosis, C2-C7 sagittal vertical axis, T1 slope, Cervical lordosis correction), regional Hounsfield units (HU) of the screw trajectory and osteoporosis status, were collected and compared between the two groups.ResultsWe analysed the clinical data of 56 patients in total. The mean overall follow-up duration was 20.6 months (range, 12–30 months). Patients were divided into the hardware failure group (n = 14) and no hardware failure group (n = 42). There were no significant differences in the general information (age, sex, follow-up period) of patients between the two groups. The differences in fusion rate, fixation levels, and screw density between the two groups were not statistically significant (p > 0.05). The failure rate of fixation ending at T1 was lower than that at C7 (9% vs. 36.3%) (p = 0.019). The regional HU values of the pedicle screw (PS) and lateral mass screw (LMS) in the failure group were lower than those in the no failure group (PS: 267 ± 45 vs. 368 ± 43, p = 0.001; LMS: 308 ± 53 vs. 412 ± 41, p = 0.001). The sagittal alignment parameters did not show significant differences between the two groups before surgery or at the final follow-up (p > 0.05). The hardware failure rate in patients without osteoporosis was lower than that in patients with osteoporosis (14.3% vs. 57.1%) (p = 0.001).ConclusionsOsteoporosis, fixation ending at C7, and low regional HU value of the screw trajectory were the independent risk factors of hardware failure after laminectomy and PCF. Future studies should illuminate if preventive measures targeting these factors can help reduce hardware failure and identified more risk factors, and perform long-term follow-up.

Technical Factors Contributing to Nonunion in Supracondylar Distal Femur Fractures Treated with Lateral Locked Plating: A Risk-Stratified Analysis.

To identify technical factors associated with nonunion after operative treatment with lateral locked plating. Retrospective cohort study. Ten Level 1 trauma centers. Six hundred fifteen adult patients with supracondylar distal femur fractures (OTA/AO Type 33A or C). Lateral locked plating. Surgery for nonunion. We observed nonunion rates of 2% in a low-risk of nonunion group (n = 129), 4% in a medium-risk group (n = 333), and 14% in a high-risk group (n = 153). Varus malreduction with an anatomic lateral distal femoral angle (aLDFA) greater than 84 degrees, was associated with double the odds of nonunion (OR, 2.1; 95% CI, 1.1 to 4.2; P = 0.03). Malreduction by medial translation of the articular block increased the odds of nonunion, with 30% increased odds per 4 mm of medial translation (95% CI, 1.0 to 1.6; P = 0.03). Working length increased the odds of nonunion primarily in the medium risk group, with an 18% increase in nonunion per 10 mm increase in working length (95% CI, 1.0 to 1.4; P = 0.01). Proximal screw density was protective against nonunion (OR, 0.71; 95% CI, 0.53 to 0.92; P = 0.02). Lateral plate length and type of plate material were not associated with nonunion. Malreduction is a surgeon-controlled variable associated with nonunion after lateral locked plating of supracondylar distal femur fractures. Longer working lengths were associated with nonunion, suggesting that simple bridge plating may be less likely to succeed for longer fractures. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Sustainable additive manufacturing of interference screws made from eco-friendly filament for anterior cruciate ligament reconstruction

Additive manufacturing (AM) is a sustainable manufacturing approach because it can lower emissions and have a lower negative impact on the environment. 3D-printed interference screws from poly-lactic acid, eco-friendly filament, by fused deposition modelling (FDM), were fabricated with different process parameters. The most popular technique for reconstructing the anterior cruciate ligament is interference screw fixation. This study considered the role of the AM sustainability paradigm in terms of material input for FDM and product manufacturing. This study considered the role of the AM sustainability paradigm in terms of material input for FDM and process efficiency by investigating the effect of the AM process parameters, such as printing temperature (PT), printing speed (PS), and infill percentage (IP) on the density and stripping torque (ST). Later, the degradation profile of the screw was analyzed using the weight loss of screws. The experimental design of the fully factorial design was with two levels for each process parameter. The significant process parameters and their interactions were through statistical analysis of the resulting design. Results have shown that PT, PS, and IP significantly influenced the density and ST of 3D-printed interference screws. In five weeks, 3D-printed interference screws started to lose weight.

Y-shaped osteotomy in the apical vertebra for treating congenital complex rigid scoliosis:at least 2-year follow-up

Objective: To investigate the clinical outcome of the coronal Y-shaped osteotomy in the apical vertebra for treating congenital complex rigid scoliosis. Methods: A retrospective analysis was conducted on 66 cases who underwent Y-shaped osteotomy treatment for congenital complex rigid scoliosis in the uppermost vertebra at the Department of Orthopedics,the Second Hospital of Shanxi Medical University from June 2007 to August 2020. There were 19 males and 47 females,with an age of (13.1±5.3) years(range:2 to 30 years).Classification of congenital scoliosis:25 cases (37.9%) were incomplete,13 cases (19.7%) were dysarthritic,and 28 cases (42.4%) were mixed. There were 25 cases (37.9%) with thoracic or rib malformations. 45 cases (68.2%) were complicated with spinal cord malformation.The main radiological indicators included Cobb angle of the curvature,Cobb angle of the local bend,apical vertebral translation (AVT),trunk shift (TS),thoracic trunk shift (TTS),radiographic shoulder height (RSH),coronal balance and sagittal vertebral axis. The preoperative,postoperative immediate,and last follow-up radiological indicators were collected and the operation time,blood loss,hospitalization time,and operation-related complications were recorded. Data were compared by repeated measure ANOVA and paired-t test. Results: All patients underwent surgery successfully. The duration of the first surgery was (221.4±52.8) minutes,and the blood loss during the first surgery was (273.2±41.8) ml. The length of the first hospital stay was (8.8±1.7) days.Unilateral fixation was performed in 19 cases (28.8%),while bilateral fixation was performed in 47 cases (71.2%). The fused segments were 7.5±2.9,and the vertebral pedicle screw density was (68.5±20.6)%. The follow-up time for the 66 patients was (36.7±17.0) months(range:24 to 102 months).The main curve Cobb Angle was improved from (58.5±18.9)°before surgery to (21.1±11.8)°after surgery,and was (23.6±15.3) ° at the last follow-up(F=273.957,P<0.01),with a correction rate of 66.2%. Segmental curve Cobb Angle was improved from (47.9±18.0)° to (16.0±11.3)° after surgery,and was (16.8±12.8) °at the last follow-up (F=270.483,P<0.01)with a correction rate of 69.2%. The AVT,TS,TTS and RSH values improved significantly at the final follow-up (all P<0.05),while coronal balance and sagittal vertical axis were maintained without significant differences between pre-operation and post-operation(both P>0.05). A total of 5 patients underwent staged operation,all of which were residual scoliosis aggravated after the first stage of orthosis operation and had good prognosis after the second stage of operation. Conclusions: Y-shaped osteotomy for the treatment of congenital rigid scoliosis results in good clinical and radiological outcomes without serious complications. This procedure can be considered as an option for the treatment of congenital complex rigid scoliosis.

The surgical management of scheurmann’s kyphosis: Efficacy and safety of a low density posterior pedicle screw construct

Background: To see if employing a low pedicle screw density in the posterior therapy of Scheuermann kyphosis is safe, radiologically effective, and clinically effective. Methods: Patients with Scheuermann kyphosis underwent posterior surgical correction between 2016 and 2019. Low Screw Density, peri apical Ponte osteotomies and cantilever correction maneuver were our surgical technique for deformity correction. Two observers performed a radiological evaluation of the before and postoperative Spinopelvic parameters. Validated Arabic version of Scoliosis Research Society 22 questionnaire were used to assess the preoperative and postoperative clinical results. Cost saving analysis was performed. Results: This study enlisted the participation of thirty patients. The patients mean age 21.8 ±3.4 years and mean follow up 34.8±7.9 months. The mean surgical time was 165.33 ±17.9 minutes , the mean number of osteotomies was 4.2± 0.8 , and the mean blood loss was 770± 139.3cc.The mean preoperative dorsal kyphosis 87.5°±4.6 °and the mean postoperative dorsal kyphosis 43.1°± 3.7° at final follow up (P&lt;0.001).The mean preoperative scoliosis research society 22 questionnaire 2.8±0.4 and the mean postoperative scoliosis research society 22 questionnaire 4.3±0.8 at final follow up (P&lt;0.001). Conclusions: Posterior Surgical Intervention with low Screw Density construct and periapical Ponte osteotomies is safe , radiologically , clinically and cost effective way in surgical management of Scheuermann kyphosis. Study Design: Prospective Cohort Study. Level of Evidence: Level IV.

Do working length and proximal screw density influence the velocity of callus formation in distal tibia fractures treated with a medial bridge plate?

Aim of our study was to evaluate the influence of working length and screw density on callus formation in distal tibial fractures fixed with a medial bridge plate. 42 distal tibia fractures treated with a bridge plate were analyzed. Minimum follow-up was 12months. mRUST score (modified Radiographic Union Scale for Tibial fractures) was used to assess callus formation. Working length and screw density were measured from post-operative radiographs. 39 (92.9%) fractures healed uneventfully. 32 (76.19%) patients showed signs of early callus formation 3 months post-surgery. In these patients a lower screw density was used compared to patients who didn't show early callus (33.4 vs. 26.6; p = 0.04). No differences was noticed in working length. Bridge plate osteosynthesis is a good treatment option in distal tibia fractures. In our series increasing the working length was not associated with a faster callus formation in distal tibia fractures. Conversely, a lower screw density proximally to the fracture site was associated to a faster callus growth.

Posterior instrumented correction and fusion of adolescent idiopathic scoliosis

Balanced frontal curve correction with horizontal shoulder levels, restoration of sagittal plane and vertebral derotation with afusion length as short as possible. Curves larger than 40-50° Cobb angle; furthermore age, location, degree of rotation, and sagittal plane deviation have to be considered. Posteriorly, segmental pedicle screw instrumentation with ahigh screw density (80%) and both titanium alloy and cobalt chrome rods. Freehand screw placement under consideration of both natural and deformity-induced pedicle morphology. Correction via reduction screws or instruments. Combined correction technique with rod rotation, segmental screw approximation to the generally concave rod and segmental correction of vertebral translation. Moderate concave distraction and convex compression. If needed, final in situ bending of the rods. Schwab typeI osteotomies; in rigid curves typeII osteotomies. Fusion with local bone, allogenic bone and/or bone substitutes (i.e.,tricalcium phosphate). Intraoperative placement of athoracic epidural catheter for postoperative pain control. Neurological monitoring throughout the procedure. Mobilization on postoperative day1 with focus on pain management and nutrition. Return to school after 4weeks. Physiotherapy after 3months, cycling after 3-6months, and full sport activities after 1year. Frontal curve correction of 60-80%, sufficient sagittal plane correction. Correction of rib hump 40%. Patient satisfaction is high at 95% and long-term revision rates of < 10%.