Using Predictive Modeling and Supervised Machine Learning to Identify Patients at Risk for Venous Thromboembolism Following Posterior Lumbar Fusion.

STUDY DESIGN: Retrospective review. OBJECTIVE: To use predictive modeling and machine learning to identify patients at risk for venous thromboembolism (VTE) following posterior lumbar fusion (PLF) for degenerative spinal pathology. METHODS: Patients undergoing single-level PLF in the inpatient setting were identified in the National Surgical Quality Improvement Program database. Our outcome measure of VTE included all patients who experienced a pulmonary embolism and/or deep venous thrombosis within 30-days of surgery. Two different methodologies were used to identify VTE risk: 1) a novel predictive model derived from multivariable logistic regression of significant risk factors, and 2) a tree-based extreme gradient boosting (XGBoost) algorithm using preoperative variables. The methods were compared against legacy risk-stratification measures: ASA and Charlson Comorbidity Index (CCI) using area-under-the-curve (AUC) statistic. RESULTS: 13, 500 patients who underwent single-level PLF met the study criteria. Of these, 0.95% had a VTE within 30-days of surgery. The 5 clinical variables found to be significant in the multivariable predictive model were: age > 65, obesity grade II or above, coronary artery disease, functional status, and prolonged operative time. The predictive model exhibited an AUC of 0.716, which was significantly higher than the AUCs of ASA and CCI (all, P < 0.001), and comparable to that of the XGBoost algorithm (P > 0.05). CONCLUSION: Predictive analytics and machine learning can be leveraged to aid in identification of patients at risk of VTE following PLF. Surgeons and perioperative teams may find these tools useful to augment clinical decision making risk stratification tool.

Racial Disparities in Spine Surgery: A Systematic Review.

STUDY DESIGN: Systematic Review. OBJECTIVES: To synthesize previous studies evaluating racial disparities in spine surgery. METHODS: We queried PubMed, Embase, Cochrane Library, and Web of Science for literature on racial disparities in spine surgery. Our review was constructed in accordance with Preferred Reporting Items and Meta-analyses guidelines and protocol. The main outcome measures were the occurrence of racial disparities in postoperative outcomes, mortality, surgical management, readmissions, and length of stay. RESULTS: A total of 1753 publications were assessed. Twenty-two articles met inclusion criteria. Seventeen studies compared Whites (Ws) and African Americans (AAs) groups; 14 studies reported adverse outcomes for AAs. When compared with Ws, AA patients had higher odds of postoperative complications including mortality, cerebrospinal fluid leak, nervous system complications, bleeding, infection, in-hospital complications, adverse discharge disposition, and delay in diagnosis. Further, AAs were found to have increased odds of readmission and longer length of stay. Finally, AAs were found to have higher odds of nonoperative treatment for spinal cord injury, were more likely to undergo posterior approach in the treatment of cervical spondylotic myelopathy, and were less likely to receive cervical disk arthroplasty compared with Ws for similar indications. CONCLUSIONS: This systematic review of spine literature found that when compared with W patients, AA patients had worse health outcomes. Further investigation of root causes of these racial disparities in spine surgery is warranted.

Height Gain After Spinal Fusion for Idiopathic Scoliosis: Which Model Fits Best?

BACKGROUND: Patients will often inquire about the magnitude of height gain after scoliosis surgery. Several published models have attempted to predict height gain using preoperative variables. Many of these models reported good internal validity but have not been validated against an external cohort. We attempted to test the validity of 5 published models against an external cohort from our institution. Models included were Hwang, Van Popta, Spencer, Watanabe, and Sarlak models. METHODS: We retrospectively queried our institution's records from 2006 to 2019 for patients with adolescent idiopathic scoliosis treated with posterior spinal fusion. We recorded preoperative and postoperative variables including clinical height measurements. We also performed radiographic measurements on preoperative and postoperative radiographic studies. We then tested the ability of the models to predict height gain by evaluating Pearson correlation coefficient, root mean square error, Akaike Information Criterion for each model. RESULTS: A total of 387 patients were included. Mean clinical height gain was 3.1 (±1.7) cm.All models demonstrated a moderate positive Pearson correlation coefficient, except the Hwang model, which demonstrated a weak correlation. The Spencer model was the only model with acceptable root mean square error (≤0.5) and was also the best fitting with the lowest Akaike Information Criterion (-308). The mean differences in height gain predictions between all models except the Hwang model was ≤1 cm. CONCLUSIONS: Four of the 5 models demonstrated moderate correlation and had good external validity compared with their development cohorts. Although the Spencer model was the best fitting, the clinical significance of the difference in height predictions compared with other models was low. The Watanabe model was the second best fitting and had the simplest formula, making it the most convenient to use in a clinical setting. We offer a simplified equation to use in a preoperative clinical setting based on this data-ΔHeight (mm)=0.77*(preoperative coronal angle-postoperative coronal angle). LEVEL OF EVIDENCE: Not Applicable.

Late spinal infections are more common after pediatric than after adult spinal deformity surgery.

PURPOSE: To compare the incidence, timing, and microbiologic factors associated with late spinal infection (onset ≥ 6 months after index operation) in pediatric versus adult spinal deformity patients who underwent instrumented posterior spinal fusion (PSF). METHODS: We retrospectively queried our institutional database for pediatric (aged ≤ 21 years) and adult patients who underwent instrumented PSF from 2000 to 2015. Inclusion criteria were > 12-month follow-up, spinal arthrodesis spanning 4 or more levels, and idiopathic or degenerative spinal deformity. We included 1260 patients (755 pediatric, 505 adult). Incidence, timing, and microbiologic and operative parameters of late spinal infections were compared using chi-squared and Fisher exact tests. Alpha = 0.05. RESULTS: Late spinal infection occurred in 28 (3.7%) pediatric and 2 (0.39%) adult patients (p = 0.009). Mean onset of infection was 4.2 years (range 0.7-12) in pediatric patients and 4.0 years (range 0.7-7.3) in adults (p = 0.93). Pediatric patients underwent arthrodesis spanning more levels (mean ± standard deviation, 10 ± 2.0) compared with adults (8.4 ± 3.3) (p < 0.001). Adults experienced greater intraoperative blood loss (2085 ± 1491 mL) compared with pediatric patients (796 ± 452 mL) (p < 0.001). Culture samples yielded positive growth in 11 pediatric and 2 adult cases. Propionibacterium and coagulase-negative staphylococci were the most commonly detected microorganisms in both cohorts. CONCLUSION: Late spinal infections were significantly more common in pediatric patients than in adults after instrumented PSF for spinal deformity. Skin and indolent microorganisms were the primary identifiable causative bacteria in both cohorts. LEVEL OF EVIDENCE: III.

Development and Validation of SCFE Percutaneous Pinning Surgical Simulation.

BACKGROUND: In situ screw fixation with a single percutaneously placed femoral screw remains widely accepted for femoral head fixation in adolescent patients with slipped capital femoral epiphysis (SCFE). Given the potential risks involved with this procedure, a simulation whereby surgical skills could be refined before entering the operating room may be of benefit to orthopaedic trainees. METHODS: We developed a synthetic model for the simulated treatment of SCFE. Five orthopaedic attendings and twenty trainees were recorded performing an in situ percutaneous fixation on the SCFE model. Time, radiation exposure, and final anteroposterior and lateral radiographs of the SCFE model were recorded. After completion, the attendings and trainees answered a Likert-based questionnaire regarding the realism and utility of the simulation, respectively. Two blinded orthopaedic surgeons rated each participant's skill level based on previously described assessment tools, including a Global Rating Scale (GRS) of technical proficiency and radiographic grading index for screw placement. Performance metrics and survey responses were evaluated for construct validity, face validity, and interrater reliability. RESULTS: The attendings demonstrated superior technical proficiency compared with trainees in terms of higher GRS scores (27.9±1.9 vs. 14.7±5.0, P<0.001) and better radiographic grading of screw placement on lateral views (P=0.019). Similarly, compared with the trainees, the orthopaedic attendings demonstrated shorter operative times (11.0±4.1 vs. 14.7±6.2 min, P=0.035) and less radiation exposure (3.7±1.7 vs. 9.5±5.7 mGy, P=0.037). The interrater reliability was excellent for both the GRS scoring (intraclass correlation coefficient=0.973) and radiographic grading (weighted κ=1.000). The attendings and trainees rated the realism and teaching utility of the simulation as "very good," respectively. CONCLUSION: Our surgical simulation for in situ percutaneous fixation of SCFE represents a valid and reliable measure of technical competency and demonstrates much promise for potential use as a formative educational tool for orthopaedic residency programs. LEVEL OF EVIDENCE: Level II.

Tranexamic acid use is associated with reduced intraoperative blood loss during spine surgery for Marfan syndrome.

PURPOSE: The utility of tranexamic acid (TXA) in patients with Marfan syndrome (MFS) is uncertain given associated aberrations within the vasculature and clotting cascade. Therefore, this study aimed to assess the association of TXA use with intraoperative blood loss and allogeneic blood transfusions in patients with MFS who underwent spinal arthrodesis. METHODS: We queried our institutional database for MFS patients who underwent spinal arthrodesis for scoliosis between 2000 and 2020 by one surgeon. We excluded procedures spanning < 4 vertebral levels, those using anterior or combined anterior/posterior approaches, and those involving growing rods, postoperative infection, or spondylolisthesis. Fifty-two patients met our criteria, of whom 22 were treated with TXA and 30 were not. Mean differences in blood loss, transfusion volume, and proportions receiving transfusion were compared between TXA and the control groups using Student t, chi-squared, or Fisher exact tests. Alpha = 0.05. RESULTS: MFS patients treated with TXA experienced less mean (± standard deviation) intraoperative blood loss (1023 ± 534 mL) compared to the control group (1436 ± 1022 mL) (p = 0.01). The TXA group had estimated blood volume loss of 27% ± 16% compared to 36% ± 21% for controls (p = 0.05). No differences were found in allogeneic transfusion rate (p = 0.66) or transfusion volume (p = 0.15). CONCLUSIONS: We found an association between TXA use and reduced blood loss during surgical treatment of MFS-associated scoliosis, suggesting that the connective tissue deficiency in MFS does not interfere with TXA's mechanism of action. LEVEL OF EVIDENCE: III.

Surgical Evaluation and Management of Spinal Pathology in Patients with Connective Tissue Disorders.

Connective tissue disorders represent a varied spectrum of syndromes that have important implications for the spine deformity surgeon. Spine surgeons must be aware of these diverse and global manifestations of disease because they have significant impact on perioperative and postoperative outcomes.

Cost-utility Analysis Comparing Bracing Versus Observation for Skeletally Immature Patients with Thoracic Scoliosis.

STUDY DESIGN: Cost-utility analysis. OBJECTIVE: This study aimed to investigate the cost-utility of bracing versus observation in patients with thoracic scoliosis who would be indicated for bracing. SUMMARY OF BACKGROUND DATA: There is high-quality evidence that bracing can prevent radiographic progression of spinal curvature in adolescent idiopathic scoliosis (AIS) patients with curves between 25° and 40° and Risser 0 to 2 skeletal maturity index. However, to our knowledge, the cost-utility of bracing in AIS has not been established. METHODS: A decision-analysis model comparing bracing versus observation was developed for a hypothetical 10-year old girl (Risser 0, Sanders 3) with a 35° main thoracic curve. We estimated the probability, cost, and quality-adjusted life years (QALY) for each node based on comprehensive review of the literature. Costs were adjusted for inflation based on Consumer Price Index and reported in terms of 2020 real dollars. Incremental net monetary benefit (INMB) was calculated based on a probabilistic sensitivity analysis using Monte Carlo simulations of 1000 hypothetical patients. One-way sensitivity analyses were performed by varying cost, probability, and QALY estimates. RESULTS: Our decision-analysis model revealed that bracing was the dominant treatment choice over observation at $50,000/QALY willingness to pay threshold. In simulation analysis of a hypothetical patient cohort, bracing was associated with lower net lifetime costs ($60,377 ±â€Š$5,340 with bracing vs. $85,279 ±â€Š$4543 with observation) and higher net lifetime QALYs (24.1 ±â€Š2.0 with bracing vs. 23.9 ±â€Š1.8 with observation). Bracing was associated with an INMB of $36,093 (95% confidence interval $18,894-$55,963) over observation over the patient's lifetime. The model was most sensitive to the impact of bracing versus observation on altering the probability of requiring surgery, either as an adolescent or an adult. CONCLUSION: Cost-utility analysis supports scoliosis bracing as the preferred choice in management of appropriately indicated AIS patients with thoracic scoliosis.Level of Evidence: 5.

Arthroscopic Posterior Capsulotomy for Knee Flexion Contracture Using a Spinal Needle.

Knee flexion contractures can arise from posterior capsule arthrofibrosis secondary to trauma, surgery, or chronic degenerative disease. This leads to limited knee extension and increased mechanical stress on the contralateral joint. Depending on the severity of the contracture, a treatment option may include surgical release of the posterior capsule. Arthroscopic posterior capsular release has been reported previously to have excellent resolution of extension deficits with minimal risk of postoperative complications. These techniques typically use an array of instruments, including shavers, biters, or scissors to perform arthrolysis of the posteromedial and posterolateral capsules. Our primary objective is to present a modified arthroscopic surgical technique for percutaneous treatment of knee flexion contracture using a spinal needle to perform a posterior capsule release.

Case of the Missing Vertebra: A Report of a Radiographic Stitching Error in a Scoliosis Patient.

CASE: A 14-year-old girl with adolescent idiopathic scoliosis underwent imaging in preparation for scoliosis surgery. Posteroanterior traction radiographs showed 4 lumbar vertebrae, while the standing film showed 5. Reconciliation with the component radiographs used for the traction showed the discrepancy was caused by a software error. She underwent surgical correction, and her recovery has been uncomplicated. CONCLUSION: Image stitching errors can lead to false depiction of structural abnormalities. Radiology technicians and clinicians should be cautious when reviewing digitally stitched images. We recommend that technicians label stitched images and indicate the overlapping region to assist with radiographic assessment.