Study Design. Retrospective cohort study. Objective. To assess for independent risk factors of postoperative ileus (POI) after lateral lumbar interbody fusion (LLIF). Summary of Background Data. POI is frequently observed in anterior lumbar interbody fusion due to significant bowel manipulation during the approach. LLIF is a minimally invasive approach to the anterior column with reduced bowel manipulation and surgical time. However, there is a paucity of literature on POI after LLIF. Methods. A retrospective review was performed of records of patients who underwent LLIF from January 2006 to December 2011 at a single institution. Patients with prolonged and recurrent POI were identified by review of hospital stay documentation by a fellowship-trained spine surgeon and a research fellow. POI patients were matched 1:1 to a control cohort without POI. Uni- and multivariate analyses were performed on demographic, comorbidity, surgical indication, medication, and perioperative details to identify independent risk factors for POI. Results. Incidence of prolonged or recurrent POI after LLIF was 7.0% (42/596). Postoperative length of stay was significantly higher for patients with POI (9.9 ± 4.3 d) than control patients (5.6 ± 4.1 d) (P < 0.001). The incidence of ileus in the first 100 LLIF cases (11%) was not significantly higher than in the last 100 LLIF cases (6%) (P = 0.21). Independent risk factors were history of gastroesophageal reflux disease (P < 0.01, adjusted odds ratio [aOR]: 24.31), posterior instrumentation (P = 0.002, aOR: 19.48), and LLIF at L1–L2 (P = 0.04, aOR: 7.82). A history of prior abdominal surgery approached significance as an independent protective factor (P = 0.07, aOR: 0.29). Conclusion. There was a relatively high incidence of POI after LLIF. Independent risk factors for POI were a history of gastroesophageal reflux disease, posterior instrumentation, and LLIF at L1–L2. A history of prior abdominal surgery approached significance as an independent protective factor. Level of Evidence: 3

Background: With bundled payments and alternative reimbursement models expanding in scope and scale, reimbursements to hospitals are declining in value. As a result, cost reduction at the hospital level is paramount for the sustainability of profitable inpatient arthroplasty practices. Although multiple prior studies have investigated cost variation in arthroplasty surgery, it is unknown whether contemporary inpatient arthroplasty practices benefit from economies of scale after accounting for hospital characteristics and patient selection factors. Quantifying the independent effects of volume-based cost variation may be important for guiding future value-based health reform. Questions/purposes: We performed this study to (1) determine whether the cost incurred by hospitals for performing primary inpatient THA and TKA is independently associated with hospital volume and (2) establish whether length of stay and discharge to home are associated with hospital volume. Methods: The primary data source for this study was the Medicare Provider Analysis and Review Limited Data Set, which includes claims data for 100% of inpatient Medicare hospitalizations. We included patients undergoing primary elective inpatient THA and TKA in 2019. Exclusion criteria included non–Inpatient Prospective Payment System hospitalizations, nonelective admissions, bilateral procedures, and patients with cancer of the pelvis or lower extremities. A total of 500,658 arthroplasties were performed across 2762 hospitals for 492,262 Medicare beneficiaries during the study period; 59% (288,909 of 492,262) of procedures were analyzed after the exclusion criteria were applied. Most exclusions (37% [182,733 of 492,262]) were because of non–Inpatient Prospective Payment System hospitalizations. Among the study group, 87% (251,996 of 288,909) of procedures were in patients who were 65 to 84 years old, 88% (255,415 of 288,909) were performed in patients who were White, and 63% (180,688 of 288,909) were in patients who were women. Elixhauser comorbidities and van Walraven indices were calculated as measures of patient health status. Hospital costs were estimated by multiplying cost-to-charge ratios obtained from the 2019 Impact File by total hospital charges. This methodology enabled us to use the large Medicare Provider Analysis and Review database, which helped decrease the influence of random cost variation through the law of large numbers. Hospital volumes were calculated by stratifying claims by national provider identification number and counting the number of claims per national provider identification number. The data were then grouped into bins of increasing hospital volume to more easily compare larger-volume and smaller-volume centers. The relationship between hospital costs and volume was analyzed using univariable and multivariable generalized linear models. Results are reported as exponential coefficients, which can be interpreted as relative differences in cost. The impact of surgical volume on length of stay and discharge to home was assessed using binary logistic regression, considering the nested structure of the data, and results are reported as odds ratios (OR). Results: Hospital cost and mean length of stay decreased, while rates of discharge to home increased with increasing hospital volume. After controlling for potential confounding variables such as patient demographics, health status, and geographic location, we found that inpatient arthroplasty costs at hospitals with 10 or fewer, 11 to 100, and 101 to 200 procedures annually were 1.32 (95% confidence interval [CI] 1.30 to 1.34; p < 0.001), 1.17 (95% CI 1.17 to 1.17; p < 0.001), and 1.10 (95% CI 1.10 to 1.10; p < 0.001) times greater than those of hospitals with 201 or more inpatient procedures annually. In addition, patients treated at smaller-volume hospitals had increased odds of experiencing a length of stay longer than 2 days (OR 1.25 to 3.44 [95% CI 1.10 to 4.03]; p < 0.001) and decreased odds of being discharged to home (OR 0.34 to 0.78 [95% CI 0.29 to 0.86]; p < 0.001). Conclusion: Higher-volume hospitals incur lower costs, shorter lengths of stay, and higher rates of discharge to home than lower-volume hospitals when performing inpatient THA and TKA. These findings suggest that small and medium-sized regional hospitals are disproportionately impacted by declining reimbursement and may necessitate special treatment to remain viable as bundled payment models continue to erode hospital payments. Further research is also warranted to identify the key drivers of this volume-based cost variation, which may facilitate quality improvement initiatives at the hospital and policy levels.

Background: To assess the clinical outcomes of 20 patients who underwent single level unilateral pedicle screw fixation following lateral lumbar interbody fusion (LLIF) for treatment of lumbar adjacent segment disease (ASD). Methods: Demographic, comorbidity, clinical assessment, peri-operative, and complication data were assessed. Visual analog scale (VAS), Oswestry disability index (ODI), and short form-12 (SF-12) were used to assess clinical outcomes. Post-operative radiographs were assessed for subsidence, cage migration, and fusion. Results: Average age of patients was 63.2±13.7 years (range, 41–86 years), with 8 males and 12 females. Recombinant human bone morphogenic protein-2 (rhBMP-2) was utilized in 18 LLIF cages (90%) and 12 posterolateral fusions (60%). Mean operation time was 214.1±47.2 minutes (range, 146–342 minutes), mean estimated blood loss of 187.5±90.1 cc (range, 50–400 cc). No patients received a blood transfusion. There were no intra-operative complications. Mean hospital length of stay was 4.4±1.7 days (range, 2–9 days). At final follow-up (mean: 13.0±12.7 months after surgery), there was significant improvement in post-op VAS (P=0.006) score compared to pre-op, but not ODI (P=0.181), SF-12 PC (P=0.480), and SF-12 MC (P=0.937). Patients with >6 months of post-operative imaging (14/20, 70%) demonstrated successful fusion in 13 out of 14 cases (93%). There was grade 0 subsidence of adjacent cranial vertebra in all cases (100%). There was grade 0 subsidence of the adjacent caudal vertebra in 13 cases (93%) and grade 1 subsidence in 1 case (7%). There was evidence of cage migration in 3 cases (21%). There were 4 patients (20%) who experienced transient neurological deficits that eventually resolved. Two patients required surgery for further ASD. Conclusions: In conclusion, this pilot study suggests that patients who undergo LLIF with unilateral pedicle screw fixation for treatment of ASD may have significantly reduced pain and favorable radiographic results. Further investigation in techniques for treatment of ASD is warranted.