Internal hemipelvectomy: A single institution's learning curve and longitudinal experience.

BACKGROUND AND OBJECTIVES: Wide margin resection for pelvic tumors via internal hemipelvectomy is among the most technically challenging procedures in orthopedic oncology. As such, surgeon experience and technique invariably affect patient outcomes. The aim of this clinical study was to assess how an individual surgeon's experiences and advancements in technology and techniques in the treatment of internal hemipelvectomy have impacted patient outcomes at our institution. METHODS: This study retrospectively examined a single tertiary academic institution's consecutive longitudinal experience with internal hemipelvectomy for primary sarcoma or pelvic metastases over a 26-year period between the years 1994 and 2020. Outcomes were assessed using two separate techniques. The first stratified patients into cohorts based on the date of surgery with three distinct "eras" ("early," "middle," and "modern"), which reflect the implementation of new techniques, including three-dimensional (3D) computer navigation and cutting guide technology into our clinical practice. The second method of cohort selection grouped patients based on each surgeon's case experience with internal hemipelvectomy ("inexperienced," "developing," and "experienced"). Primary endpoints included margin status, complication profiles, and long-term oncologic outcomes. Whole group multivariate analysis was used to evaluate variables predicting blood loss, operative time, tumor-free survival, and mortality. RESULTS: A total of 72 patients who underwent internal hemipelvectomy were identified. Of these patients, 24 had surgery between 1994 and 2007 (early), 28 between 2007 and 2015 (middle), and 20 between 2016 and 2020 (modern). Twenty-eight patients had surgery while the surgeon was still inexperienced, 24 while developing, and 20 when experienced. Evaluation by era demonstrated that a greater proportion of patients were indicated for surgery for oligometastatic disease in the modern era (0% vs. 14.3% vs. 35%, p = 0.022). Fewer modern cases utilized freehand resection (100% vs. 75% vs. 55%, p = 0.012), while instead opting for more frequent utilization of computer navigation (0% vs. 25% vs. 20%, p = 0.012), and customized 3D-printed cutting guides (0% vs. 0% vs. 25%, p = 0.002). Similarly, there was a decline in the rate of massive blood loss observed (72.2% vs. 30.8% vs. 35%, p = 0.016), and interdisciplinary collaboration with a general surgeon for pelvic dissection became more common (4.2% vs. 32.1% vs. 85%, p < 0.001). Local recurrence was less prevalent in patients treated in middle and modern eras (50% vs. 15.4% vs. 25%, p = 0.045). When stratifying by case experience, surgeries performed by experienced surgeons were less frequently complicated by massive blood loss (66.7% vs. 40% vs. 20%, p = 0.007) and more often involved a general surgeon for pelvic dissection (17.9% vs. 37.5% vs. 65%, p = 0.004). Whole group multivariate analysis demonstrated that the use of patient-specific instrumentation (PSI) predicted lower intraoperative blood loss (p = 0.040). However, surgeon experience had no significant effect on operative time (p = 0.125), tumor-free survival (p = 0.501), or overall patient survival (p = 0.735). CONCLUSION: While our institution continues to utilize neoadjuvant and adjuvant therapies following current guideline-based care, we have noticed changing trends from early to modern periods. With the advent of new technologies, we have seen a decline in freehand resections for hemipelvectomy procedures, and a transition to utilizing more 3D navigation and customized 3D cutting guides. Furthermore, we have employed the use of an interdisciplinary team approach more regularly for these complicated cases. Although our results do not demonstrate a significant change in perioperative outcomes over the years, our institution's willingness to treat more complex cases likely obscures the benefits of surgeon experience and recent technological advances for patient outcomes.

Challenges in the Management of Complex Soft-Tissue Sarcoma Clinical Scenarios.

With nearly 15,000 new cases of soft-tissue sarcoma (STS) in the United States each year, early diagnosis and therapeutic management is imperative for successful patient outcomes. Primary STS is conventionally treated with a combination of wide-margin resection, neoadjuvant or adjuvant radiation therapy, and, in specific cases, adjuvant chemotherapy. However, in situations of complex disease presentation, guidelines for treatment are less clearly outlined. Limited metastatic disease, local recurrence, fungating STSs, and unplanned or incomplete resections of STSs present unique challenges for the multidisciplinary care team. The management of complex STS clinical scenarios usually involves limb-salvage resection or amputation as well as some combination of radiation therapy and/or ablative interventional radiology techniques. As a result, a multidisciplinary team approach is essential for treating patients in these challenging scenarios, with a recent focus on the integration of plastic and reconstructive surgery into the treatment algorithm.

Radiolucent implants in orthopedic oncology.

Radiolucent implants in have demonstrated promising results for both extremity and spine oncologic procedures. However, questions persist about whether the superiority in surveillance imaging justify the increased cost and technical challenges. In this review, we present the current body of literature for the use of radiolucent implants in musculoskeletal oncology, with a focus on implant complications, including screw loosening, breakage, malposition, and loss of reduction. We also discuss clinical outcomes, technical considerations, and postoperative radiotherapy.

Association between neutrophil-lymphocyte ratio, platelet-lymphocyte ratio, and survival in undifferentiated pleomorphic sarcoma (NLR, PLR, and overall survival in UPS).

BACKGROUND AND OBJECTIVES: Cancer-related inflammation has been shown to be a driver of tumor growth and progression, and there has been a recent focus on identifying markers of the inflammatory tumor microenvironment. Neutrophil-lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR) are inflammatory indices that have been identified as prognostic biomarkers in various malignancies. However, there is limited and conflicting data regarding their prognostic value in soft tissue sarcoma (STS) and specifically in undifferentiated pleomorphic sarcoma (UPS). METHODS: This was a retrospective review of patients who underwent surgical treatment for primary UPS from 1993 to 2021. Cutoff values for NLR and PLR were determined by receiver operating curve analysis. Cox proportional hazards regression was used to determine prognostic factors on univariate and multivariate analysis. RESULTS: Eighty-six patients were included. The optimal cutoff value was 3.3 for NLR and 190 for PLR. Both high NLR (HR 2.44; 95% CI 1.29-4.63; p = 0.005) and high PLR (HR 1.99; 95% CI 1.08-3.67, p = 0.02) were associated with worse OS on univariate analysis. On multivariate analysis, metastasis at presentation and radiotherapy were independently predictive of OS, but high NLR (HR 1.30; 95% CI 0.64-2.98; p = 0.41) and high PLR (HR 1.63; 95% CI 0.82-3.25; p = 0.17) were not predictive of survival. CONCLUSIONS: High pre-treatment NLR and PLR were associated with decreased overall survival but were not independent predictors of survival in patients undergoing resection for UPS. Until additional prospective studies can be done, survival outcomes are best predicted using previously established patient- and tumor-specific factors.

Comparison of Reconstruction Techniques Following Sacroiliac Tumor Resection: A Systematic Review.

BACKGROUND: Although internal hemipelvectomies with sacroiliac resections are not traditionally reconstructed, surgeons are increasingly pursuing pelvic ring reconstruction to theoretically improve stability, function, and early ambulation. This study aims to systematically compare complications and functional and oncologic outcomes of sacroiliac resection with and without reconstruction. METHODS: PubMed and MEDLINE were queried for studies published between January 1990 and October 2020 pertaining to sacroiliac neoplasm resection with subsequent reconstruction. Patient demographics, histopathologic diagnoses, reconstruction techniques, Musculoskeletal Tumor Society (MSTS) functional scores, and oncologic outcomes were pooled. RESULTS: Twenty-three studies (201 patients) were included for analysis. Reconstruction was performed in 79.1% of patients, most commonly with nonvascularized autografts (45.8%). The overall complication rate was 54.8%; however, resection followed by reconstruction demonstrated significantly higher complication (62.3% versus 25.7%, p < 0.001) and infection rates (13.7% versus 0%, p = 0.020). Mean MSTS functional score trended higher in nonreconstructed patients (82% versus 71.6%). CONCLUSIONS: Reconstruction after sacroiliac resection produced higher complication rates and poorer physical recovery when compared with nonreconstructed resection. This systematic review suggests that patients without spinopelvic junction instability may experience superior outcomes without reconstruction. Ultimately, the need to reconstruct the pelvic girdle depends on tumor size, prognosis, and functional goals.

Minimally Invasive Surgical Approach for Open Common Peroneal Nerve Neurolysis in the Setting of Previous Posterior Schwannoma Removal.

The common peroneal nerve (CPN) runs laterally around the fibular neck and enters the peroneal tunnel, where it divides into the deep, superficial, and recurrent peroneal nerves. CPN entrapment is the most common neuropathy of the lower extremity and is vulnerable at the fibular neck because of its superficial location. Schwannomas are benign, encapsulated tumors of the nerve sheath that can occur sporadically or in cases of neurocutaneous conditions, such neurofibromatosis type 2. In cases with compressive neuropathy resulting in significant or progressive motor loss, decompression and neurolysis should be attempted. We present a technical note for the treatment of CPN compressive neuropathy in the setting of a previous ipsilateral schwannoma removal with a minimally invasive surgical approach and neurolysis of the CPN at the fibular neck.

Extraskeletal myxoid chondrosarcoma: A case series and review of the literature.

BACKGROUND: Extraskeletal myxoid chondrosarcoma (EMC) is a rare malignant soft tissue sarcoma (STS) that accounts for less than 3% of all soft tissue tumors. The conventional treatment for primary EMC is wide local excision with or without radiation therapy. MATERIALS AND METHODS: This study was a retrospective review of all EMC cases treated within a single institution between 1992 and 2019. EMC was diagnosed using a combination of histologic morphology and immunostaining, with confirmatory fluorescent in situ hybridization. Overall survival (OS) and disease-specific survival (DSS) were defined using Kaplan-Meier analysis. RESULTS: Fifteen patients were evaluated, including 11 males and four females. The average age at presentation was 51.7 ± 20.4 years and the mean follow-up time was 61.5 months (range, 5-286 months). The average resected tumor size at largest dimension was 7.14 cm (range, 2.4-18.7). Twelve of fifteen (80%) patients underwent wide local excision, and nine of the twelve (75%) underwent local radiation therapy. The 1-, 5-, and 10-year OS was 80% (95% CI, 59.8-100), 72% (95% CI, 48.5-95.5), and 72% (95% CI, 48.5-95.5), respectively. The 1-, 5-, and 10-year DSS was 92.3% (95% CI, 77.8-100), 83.1% (95% CI, 61.5-100), and 83.1% (95% CI, 61.5-100), respectively. At last follow-up, 11 patients were alive and ten (90.9%) were disease free. CONCLUSIONS: Extraskeletal myxoid chondrosarcoma is a very rare STS most often seen in males and in the extremities. Our cohort was too small to provide meaningful statistical analysis; however, we observed lower rates of local recurrence in patients treated with radiation.

Indication for Proximal Femoral Replacement Is Associated With Risk of Failure.

BACKGROUND: Proximal femoral replacement (PFR) is reserved as a salvage procedure after failed total hip arthroplasty (THA) or after wide margin resection of tumors involving the proximal femur. Although failure of the PFR construct remains a significant problem, indication has not previously been investigated as a risk factor for failure. METHODS: This study retrospectively evaluated patients who underwent PFR over a consecutive 15-year period for primary sarcoma or metastatic disease of the proximal femur, compared with conversion to PFR after failed THA. PFR failure was defined as recurrent prosthetic dislocations, periprosthetic fracture, aseptic loosening, or infection that ultimately resulted in revision surgery. RESULTS: Overall, 99 patients were evaluated, including 58 in the neoplasm and 41 in the failed THA cohorts. Failed THA patients were older (P < .001), with a greater proportion having comorbid hypertension (P = .008), cardiac disease (P = .014), and history of prior ipsilateral and intracapsular surgeries (P < .001). The failure rate was significantly higher in failed THA patients (39.0% vs 10.3%; P < .001) with significantly shorter implant survivorship on Kaplan-Meier analysis (P = .003). A multivariate Cox proportional hazards model showed that THA failure was the only independent predictor for PFR failure (hazard ratio: 4.26, 95% confidence interval: 1.66-10.94; P = .003). CONCLUSION: This study revealed significantly worse PFR implant survivorship in patients undergoing PFR for the indication of failed THA compared with neoplasm. Although the underlying etiology of this relationship remains to be explicitly outlined, poor bone quality and soft tissue integrity, multiple prior surgeries, and comorbid conditions are likely contributing factors.

A Population-based Analysis of Lymph Node Metastasis in Extremity Soft Tissue Sarcoma: An Update.

BACKGROUND: Soft tissue sarcomas (STSs) are mesenchymal tumors that may rarely metastasize to lymph nodes. This investigation sought to evaluate regional lymph node metastasis (RLNM) in extremity STS using a national cohort. MATERIALS AND METHODS: This study was a retrospective review of the Surveillance, Epidemiology, and End Results database from 1975 to 2016. A Cox proportional hazards model was used to identify prognostic factors associated with disease-specific survival (DSS). RESULTS: RLNM was present in 3.7% (n = 547) of extremity STS. The rate of RLNM was highest in rhabdomyosarcoma (26.7%), clear cell sarcoma (18.8%), epithelioid sarcoma (14.5%), angiosarcoma (8.1%), spindle cell sarcoma (5.0%), and synovial sarcoma (3.2%). The 5-year DSS probability without RLNM was 69% (standard error: 1.3%) compared to 26% (standard error: 3.6%) with RLNM (P < 0.001). For the historically high-risk extremity STS, advanced age (hazard ratio (HR), 1.036; 95% confidence interval (CI), 1.0-1.04; P < 0.001), higher grade tumors (HR, 1.979; 95% CI, 1.3-3.0; P < 0.001), tumor size greater than 10 cm (HR, 1.892; 95% CI, 1.3-2.7; P < 0.001), primary site surgery (HR, 0.529; 95% CI, 0.3-0.8; P = 0.006), distant metastasis (HR, 4.585; 95% CI, 3.0-6.8; P < 0.001), and RLNM (HR, 2.153; 95% CI, 1.3-3.5; P = 0.003) were each independent disease-specific prognostic factors. CONCLUSIONS: The prognosis of RLNM in historically high-risk extremity STS is poor with a 5-year DSS of 26%. These data support a staging system of STS inclusive of nodal involvement and contribute to the growing body of evidence that characterizes the rates of RLNM in STS.

The Role of Platelet-Rich Plasma in Cartilage Pathology: An Updated Systematic Review of the Basic Science Evidence.

PURPOSE: To review the basic science studies on platelet-rich plasma (PRP) for cartilage and determine whether there has been an improvement in methodology and outcome reporting that would allow for a more meaningful analysis regarding the mechanism of action and efficacy of PRP for cartilage pathology. METHODS: The PubMed/MEDLINE and EMBASE databases were screened in May 2017 with publication dates of January 2011 through May 2017 using the following key words: "platelet-rich plasma OR PRP OR autologous conditioned plasma (ACP) OR ACP AND cartilage OR chondrocytes OR chondrogenesis OR osteoarthritis OR arthritis." Two authors independently performed the search, determined study inclusion, and extracted data. Data extracted included cytology/description of PRP, study design, and results. RESULTS: Twenty-seven studies (11 in vitro, 13 in vivo, 3 in vitro and in vivo) met the inclusion criteria and were included in the study. All of the studies (100%) reported the method by which PRP was prepared. Two studies reported basic cytologic analysis of PRP, including platelet, white blood cell, and red blood cell counts (6.7%). Nine studies reported both platelet count and white blood cell count (30.0%). Twelve studies reported platelet count alone (40.0%). Nine studies (30.0%) made no mention at all as to the composition of the PRP used. PRP was shown to increase cell viability, cell proliferation, cell migration, and differentiation. Several studies demonstrated increased proteoglycan and type II collagen content. PRP decreased inflammation in 75.0% of the in vitro studies reporting data and resulted in improved histologic quality of the cartilage tissue in 75.0% of the in vivo studies reporting data. CONCLUSIONS: Although the number of investigations on PRP for cartilage pathology has more than doubled since 2012, the quality of the literature remains limited by poor methodology and outcome reporting. A majority of basic science studies suggest that PRP has beneficial effects on cartilage pathology; however, the inability to compare across studies owing to a lack of standardization of study methodology, including characterizing the contents of PRP, remains a significant limitation. Future basic science and clinical studies must at a minimum report the contents of PRP to better understand the clinical role of PRP for cartilage pathology. CLINICAL RELEVANCE: Establishing proof of concept for PRP to treat cartilage pathology is important so that high-quality clinical studies with appropriate indications can be performed.

Inpatient Versus Outpatient Arthroplasty: A Single-Surgeon, Matched Cohort Analysis of 90-Day Complications.

BACKGROUND: Although some prior work supports the safety of same-day arthroplasty performed in a hospital, concerns remain when these procedures are performed in a free-standing ambulatory surgery center. The purpose of this study is to compare 90-day complication rates between matched cohorts that underwent inpatient vs outpatient arthroplasty at an ambulatory surgery center. METHODS: A single-surgeon cohort of 243 consecutive patients who underwent outpatient arthroplasty was matched with 243 inpatients who had the same procedure. One-to-one nearest-neighbor matching with respect to gender, age, American Society of Anesthesiologists Score, and body mass index was utilized. The 486 primary arthroplasties included 178 unicondylar knees (36.6%), 146 total hips (30.0%), 92 total knees (18.9%), and 70 hip resurfacings (14.5%). Ninety-day outcomes including reoperation, readmission, unplanned clinic or emergency department visits, and major and minor complications were compared using a 2-sample proportions test. RESULTS: The 2 cohorts were similar in distribution of demographic variables, demonstrating successful matching. The inpatient and outpatient cohorts both had readmission rates of 2.1% (P = 1.0). With the number of subjects studied, there were no statistically significant differences in rates of major complications (2.1% vs 2.5%, P = 1.0), minor complications (7.0% vs 7.8%, P = .86), reoperations (0.4% vs 2.1%, P = .22), emergency department visits (1.6% vs 2.5%, P = .52), or unplanned clinic visits (3.3% vs 5.8%, P = .19). CONCLUSION: This study suggests that arthroplasty procedures can be performed safely in an ambulatory surgery center among appropriately selected patients without an increased risk of complications.

Effect of Surgeon Volume on Complications, Length of Stay, and Costs Following Anterior Cervical Fusion.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: To identify the association between surgeon volume and inpatient complications, length of stay, and costs associated with ACF. SUMMARY OF BACKGROUND DATA: Increased surgeon volume may be associated with improved outcomes after surgical procedures. However, there is a lack of information on the effect of surgeon volume on short-term outcomes after anterior cervical fusion (ACF). METHODS: A retrospective cohort study of ACF patients was performed using the Nationwide Inpatient Sample (NIS) from 2003 to 2009. Surgeon volume was divided into three categories, volume <25th percentile, 25th to 74th percentile, and ≥75th percentile of surgeon volume. Multivariate regression was used to compare the rates of adverse events, hospital length of stay, and total hospital costs between surgeon volume categories. RESULTS: A total of 419,212 ACF patients were identified. The 25th percentile for volume was 5 cases per year, and the 75th percentile for volume was 67 cases per year. Volume <25th percentile was associated with increased rates of any adverse event (odd ratio, OR 3.8, P < 0.001), and multiple individual complications including death (OR 2.5, P=0.014), myocardial infarction (OR4.4, P < 0.001), sepsis (OR 4.1, P < 0.001), and surgical site infection (OR 4.0, P < 0.001). Notably, volume ≥75th percentile was associated with decreased rates of any adverse event (OR 0.7, P < 0.001) and death (OR 0.6, P = 0.028). On multivariate analysis, length of stay was significantly increased by 2.3 days (P < 0.001) for surgeons <25th percentile of volume and was decreased by 0.3 days for surgeons with volume ≥75th percentile. Hospital costs were $4569 more for surgeons with <25th percentile of volume and $1213 less for surgeons with ≥75th percentile volume. CONCLUSION: In this nationally representative sample, surgeons with volume <25th percentile had significantly increased complications, length of stay, and costs. Conversely, surgeons with ≥75th percentile volume experienced decreased complications, length of stay, and costs. LEVEL OF EVIDENCE: 4.

The Kinematics and Spondylosis of the Lumbar Spine Vary Depending on the Levels of Motion Segments in Individuals With Low Back Pain.

STUDY DESIGN: A prospective cohort study. OBJECTIVE: The aim of this study was to identify associations of spondylotic and kinematic changes with low back pain (LBP). SUMMARY OF BACKGROUND DATA: The ability to characterize and differentiate the biomechanics of both the symptomatic and asymptomatic lumbar spine is crucial to alleviate the sparse literature on the association of lumbar spine biomechanics and LBP. METHODS: Lumbar dynamic plain radiographs (flexion-extension), dynamic computed tomography (CT) scanning (axial rotation, disc height), and magnetic resonance imaging (MRI, disc and facet degeneration grades) were obtained for each subject. These parameters were compared between symptomatic and control groups using Student t test and multivariate logistic regression, which controlled for patient age and sex and identified spinal parameters that were independently associated with symptomatic LBP. Disc grade and mean segmental motion by level were tested by one-way analysis of variance (ANOVA). RESULTS: Ninety-nine volunteers (64 asymptomatic/35 LBP) were prospectively recruited. Mean age was 37.3 ±â€Š10.1 years and 55% were male. LBP showed association with increased L5/S1 translation [odds ratio (OR) 1.63 per mm, P = 0.005], decreased flexion-extension motion at L1/L2 (OR 0.87 per degree, P = 0.036), L2/L3 (OR 0.88 per degree, P = 0.036), and L4/L5 (OR 0.87 per degree, P = 0.020), increased axial rotation at L4/L5 (OR 2.11 per degree, P = 0.032), decreased disc height at L3/L4 (OR 0.52 per mm, P = 0.008) and L4/L5 (OR 0.37 per mm, p < 0.001), increased disc grade at all levels (ORs 2.01-12.33 per grade, P = 0.001-0.026), and increased facet grade at L4/L5 (OR 4.99 per grade, P = 0.001) and L5/S1 (OR 3.52 per grade, P = 0.004). Significant associations were found between disc grade and kinematic parameters (flexion-extension motion, axial rotation, and translation) at L4/L5 (P = 0.001) and L5/S1 (P < 0.001), but not at other levels (P > 0.05). CONCLUSION: In symptomatic individuals, L4/L5 and L5/S1 levels were affected by spondylosis and kinematic changes. This study clarifies the relationships between kinematic alterations and LBP, mostly observed at the above-mentioned segments. LEVEL OF EVIDENCE: N/A.

Results of Database Studies in Spine Surgery Can Be Influenced by Missing Data.

BACKGROUND: National databases are increasingly being used for research in spine surgery; however, one limitation of such databases that has received sparse mention is the frequency of missing data. Studies using these databases often do not emphasize the percentage of missing data for each variable used and do not specify how patients with missing data are incorporated into analyses. This study uses the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database to examine whether different treatments of missing data can influence the results of spine studies. QUESTIONS/PURPOSES: (1) What is the frequency of missing data fields for demographics, medical comorbidities, preoperative laboratory values, operating room times, and length of stay recorded in ACS-NSQIP? (2) Using three common approaches to handling missing data, how frequently do those approaches agree in terms of finding particular variables to be associated with adverse events? (3) Do different approaches to handling missing data influence the outcomes and effect sizes of an analysis testing for an association with these variables with occurrence of adverse events? METHODS: Patients who underwent spine surgery between 2005 and 2013 were identified from the ACS-NSQIP database. A total of 88,471 patients undergoing spine surgery were identified. The most common procedures were anterior cervical discectomy and fusion, lumbar decompression, and lumbar fusion. Demographics, comorbidities, and perioperative laboratory values were tabulated for each patient, and the percent of missing data was noted for each variable. These variables were tested for an association with "any adverse event" using three separate multivariate regressions that used the most common treatments for missing data. In the first regression, patients with any missing data were excluded. In the second regression, missing data were treated as a negative or "reference" value; for continuous variables, the mean of each variable's reference range was computed and imputed. In the third regression, any variables with > 10% rate of missing data were removed from the regression; among variables with ≤ 10% missing data, individual cases with missing values were excluded. The results of these regressions were compared to determine how the different treatments of missing data could affect the results of spine studies using the ACS-NSQIP database. RESULTS: Of the 88,471 patients, as many as 4441 (5%) had missing elements among demographic data, 69,184 (72%) among comorbidities, 70,892 (80%) among preoperative laboratory values, and 56,551 (64%) among operating room times. Considering the three different treatments of missing data, we found different risk factors for adverse events. Of 44 risk factors found to be associated with adverse events in any analysis, only 15 (34%) of these risk factors were common among the three regressions. The second treatment of missing data (assuming "normal" value) found the most risk factors (40) to be associated with any adverse event, whereas the first treatment (deleting patients with missing data) found the fewest associations at 20. Among the risk factors associated with any adverse event, the 10 with the greatest effect size (odds ratio) by each regression were ranked. Of the 15 variables in the top 10 for any regression, six of these were common among all three lists. CONCLUSIONS: Differing treatments of missing data can influence the results of spine studies using the ACS-NSQIP. The current study highlights the importance of considering how such missing data are handled. CLINICAL RELEVANCE: Until there are better guidelines on the best approaches to handle missing data, investigators should report how missing data were handled to increase the quality and transparency of orthopaedic database research. Readers of large database studies should note whether handling of missing data was addressed and consider potential bias with high rates or unspecified or weak methods for handling missing data.