Faculty Bibliography

OBJECTIVE:The all-payer model is a healthcare payment system unique to the state of Maryland, while the Medicare Severity-Diagnosis-Related Group (MS-DRG) model is used by all other states. The purpose of this study was to investigate differences in reimbursement and inpatient length of stay (LOS) in adult spinal deformity (ASD) surgery between the all-payer and MS-DRG models. METHODS:MS-DRG reimbursements were calculated using the Centers for Medicare & Medicaid Services Web Pricer tool; reimbursements for the all-payer model were compiled from a single institution in the state of Maryland. Payments for the most frequently occurring ASD MS-DRGs (codes 453, 454, 455, 456, 457, 458, and 460) were analyzed for fiscal years 2018-2023. The mean inpatient LOS was calculated for each MS-DRG code and reimbursement model. RESULTS:When comparing 416 MS-DRG and 1783 all-payer model accounts, the overall mean reimbursements for ASD surgery were significantly lower under the MS-DRG model ($59,199 vs $77,246, p < 0.001). The mean reimbursement payments for MS-DRG codes 453, 454, 455, 456, 457, and 460 were significantly higher under the Maryland all-payer model (p < 0.001). The mean LOS was significantly shorter in the all-payer model for MS-DRG code 453 (p = 0.046) and longer for code 457 (p < 0.001). For all other codes, no significant differences in LOS were observed. CONCLUSIONS:ASD surgery reimbursements are higher overall under the Maryland all-payer model compared with the MS-DRG model. The mean inpatient LOS did not differ significantly across most MS-DRG codes, highlighting the financial viability of an all-payer model in a healthcare system.

STUDY DESIGN/METHODS:Retrospective review. OBJECTIVE:Determine if patients with different degrees of incidence (PI) have the capacity to compensate via pelvic retroversion before initiating lower extremity compensation. SUMMARY OF BACKGROUND DATA/BACKGROUND:Compensatory mechanisms in the spine are thought to help patients with deformities maintain sagittal alignment. Pelvic retroversion and thoracic hypokyphosis are key mechanisms that help maintain balance. When these mechanisms are exhausted, patients often flex their hips and bend their knees. METHODS:This was a retrospective radiographic analysis of the EOS images at a single institution. Various spinal sagittal parameters and lower extremity knee flexion measurements were performed. Patients were subcategorized according to PI. Knee flexion in these groups was correlated with various sagittal parameters to determine whether there were differences when knee flexion occurred based on the PI. RESULTS:Knee flexion was independently correlated with PI, pelvic tilt (PT), PI-lumbar lordosis mismatch (PI-LL), and T1 pelvic inclination angle (TPA) in multiple regression analyses (P < 0.05). In patients with lower PI, knee flexion occurred at a PT of 10-15 degrees, PI-LL mismatch of -5-0 degrees, and TPA of about 10-15 degrees. In those with high PI, knee flexion occurred at a PT of ∼25-30 degrees, PI-LL mismatch of ∼15-20 degrees, and TPA about 25 degrees. Those with a lower PI also more rapidly increased knee flexion with further increases in PI-LL mismatch and TPA compared with those with a higher PI. CONCLUSION/CONCLUSIONS:This study demonstrates that patients with different PI have different capacities to compensate for increasing sagittal plane deformity before initiating knee flexion lower extremity compensation. Those with a lower PI retroverted their pelvis less and begin knee compensation earlier than those with a higher PI. These findings are important for surgical planning in patients with differing PI who are compensating for knee flexion.

STUDY DESIGN/METHODS:Retrospective review of multicenter data. OBJECTIVE:To compare long-term neurologic recovery in patients with and without incidental durotomy (hereafter, "durotomy") after adult spinal deformity surgery. SUMMARY OF BACKGROUND DATA/BACKGROUND:Durotomy is a common complication of adult spinal deformity surgery and is typically associated with technical challenges during the procedure. METHODS:Using a prospectively collected database, we included 1452 patients (73% female; mean age, 60±14 y) who underwent adult spinal deformity surgery from 2008-2020 at 22 US centers. We compared patients with and without durotomy with respect to demographic characteristics, surgical variables, and neurologic outcomes at baseline and at 1 and 2 years postoperatively. Multivariate analysis compared neurologic complications and length of stay (LOS) between the groups. P<.05 was considered significant. RESULTS:Durotomy occurred in 121 patients (8.3%). Patients with durotomy were more likely to have undergone revision surgery (P<.001) and had higher Charlson Comorbidity Index values (P=.029) than those who did not. Patients with durotomy had higher estimated blood loss, longer operative time, more frequent 3-column osteotomies, and longer LOS (all, P<.001). Lower-extremity motor scores did not differ between patients with durotomy and those without at 1 and 2 years postoperatively. The incidence of neurologic, medical, and surgical complications did not differ significantly between the 2 groups. Patients with durotomy had a higher rate of inpatient return to the operating room (5.0%) than those without (2.0%) (P=.04). On multivariate analysis, there were no differences between groups in lower-extremity motor scores, neurologic complications, or LOS. CONCLUSIONS:Incidental durotomy during adult spinal deformity surgery was associated with greater intraoperative complexity and transient sensory symptoms but did not adversely affect long-term motor recovery, neurologic complications, or patient-reported outcomes. These findings suggest durotomy is a manageable complication without lasting functional consequences.

STUDY DESIGN/METHODS:Retrospective review of prospectively collected, multicenter data. OBJECTIVE:To assess associations between patient height and weight independently and interactively with the incidence of proximal junctional kyphosis (PJK) after surgical treatment of adult spine deformity. SUMMARY OF BACKGROUND DATA/BACKGROUND:Body mass index has traditionally been used to assess the influence of body composition on surgical outcomes, but the individual effects of height and weight have not been studied in relation to PJK. METHODS:We compared baseline demographic characteristics, radiographic measurements, and perioperative variables between patients who developed PJK after adult spinal deformity surgery between 2008 and 2020 and those who did not. Using a generalized additive model with a logistic link function, we modeled height and weight and their interaction as smooth terms to capture potential nonlinear effects on PJK risk. Multivariate analysis was adjusted for age, history of osteoporosis, upper instrumented vertebra, number of levels fused, and postoperative pelvic incidence minus lumbar lordosis and T1 pelvic angle. RESULTS:Of 904 included patients, the median age was 65 years (interquartile range: 58-71), and 76% were female. PJK developed in 131 patients (14%). Baseline characteristics, including frailty, comorbidities, and radiographic measures, did not differ significantly between the PJK and non-PJK groups. Taller height was a predictor of PJK (P=.03). In contrast, weight was not an independent predictor, and there was no significant interaction between height and weight. The incidence of PJK peaked at a height of approximately 179 cm before plateauing. CONCLUSIONS:Taller height, but not weight, was associated with developing PJK after adult spinal deformity surgery. These findings underscore the importance of considering patient height during surgical planning.

STUDY DESIGN/METHODS:Retrospective review of a prospective cervical deformity (CD) database. OBJECTIVE:Determining when shorter fusions can be successful in CD surgery to reduce the extent of the surgical procedure while mitigating complications. SUMMARY OF BACKGROUND DATA/BACKGROUND:Multicenter outcomes database of CD patients. METHODS:CD patients were stratified as short fusions (SF: ≤4 levels fused, cervical LIV) or long fusions (LF: >4 levels fused, LIV caudal to C7). Groups were compared in terms of demographics, baseline and 1-year alignment, patient-reported outcome measures (PROMs), and surgical parameters. The data were then reanalyzed after controlling for baseline cervical Sagittal Vertical Axis (cSVA) using propensity score matching. Decision trees were used to identify baseline factors associated with postop alignment failure (1-year cSVA>4 mm or C2S>20°) among SF patients. RESULTS:127 patients were analyzed with 100 LF and 27 SF patients. SF had significantly less EBL (131 vs. 1001 mL) and shorter operative time (223min vs. 435 min). At baseline, LF had worse cervical alignment (cSVA=42.6 vs. 23.0 mm) and were more disabled by Neck Disability Index (NDI, 50 vs. 38). After matching by cSVA, the mean baseline cSVA decreased from 42.6 mm to 27.6 mm in the LF group and increased from 23.0 mm to 27.2 mm in the SF group. 71% (n=15) of SF achieved the MCID for NDI vs. 52% (n=11) of LF pts. SF patients with a BL C2S>26° (n=13) were 12.4 times as likely as SF patients with C2S≤26° (n=13) to have post-operative alignment failure (85% vs. 31%, P<.01) and 5.1 times as likely to have a post-operative complication (69% vs. 31%, P<.05). CONCLUSIONS:Although short fusions can result in excellent outcomes with less extensive surgeries, those with more severe deformities may require longer fusions. SF should be avoided in patients with a BL C2S>26° due to the increased risk of complications and realignment failure.

STUDY DESIGN/METHODS:Retrospective cohort analysis. OBJECTIVE:Assess the distribution of Medicare's spinal-deformity-specific diagnosis-related group (DRGs) relative to surgical invasiveness, hospital length of stay (LOS), discharge disposition, 90-day postoperative quality metrics, and reimbursement costs for adult spinal deformity (ASD) operations. SUMMARY OF BACKGROUND DATA/BACKGROUND:Heterogeneity of ASD call into question Medicare's DRGs to accurately capture nuances of ASD surgical episodes of care. METHODS:Adults who underwent thoracic to pelvis instrumentation with associated DRGs were identified from a multicenter database. Demographics, operative details, inpatient course, discharge disposition, 90-day adverse events, and reimbursement costs were compared between spinal deformity-specific DRG codes. Distribution of DRGs for a subset of these patients who fit into one of 6 commonly performed surgical strategies to address ASD was also assessed. RESULTS:Of the 314 patients included for analysis, the majority fell into +CC DRGs, while the minority had +MCC DRGs or no MCC/CC DRG. Within each DRG, there was considerable heterogeneity in regard to patients' ages, ASA, CCI, frailty, surgical invasiveness, postoperative ICU/hospital LOS, discharge disposition, and complication profiles.+MCC DRGs had significantly greater ASA and Edmonton Frailty Scores. While +MCC and +CC had relatively similar surgical invasiveness, +MCC had greater ICU admissions, in-hospital adverse events, and nonhome discharges as well as longer ICU, hospital, and rehab LOS. While reimbursements were significantly higher for +MCC DRG compared with +CC DRGs and DRGs without MCC/CC, there were large ranges in reimbursement within all DRG subgroups.The 7 DRGs varied significantly within and between the subset of 6 commonly performed surgical strategies, although there were no differences in regard to ICU admissions and LOS, hospital LOS, discharge disposition, and number of adverse events (in-hospital, 90-day). CONCLUSIONS:While Medicare's spinal-deformity DRG codes capture average trends in surgical/postoperative episodes of care for ASD patients, each encompasses highly heterogeneous patients and associated surgical operations rendering them unreliable gauges of patient/surgical complexity, early postoperative trajectories, and reimbursement costs. A more granular system is needed to more accurately capture the nuances of ASD operations and their associated quality metrics and reimbursement costs.

STUDY DESIGN/METHODS:Retrospective review of a prospective, multicenter adult cervical deformity (CD) database. OBJECTIVE:Investigate the prevalence and clinical significance of combined cervical scoliosis (CS) and cervical kyphosis (CK) among patients undergoing surgical management of CD. SUMMARY OF BACKGROUND DATA/BACKGROUND:Although adult CD patients may have both CS and CK, few studies have confirmed prevalence of CK and CS and associated radiographic and clinical findings. MATERIALS AND METHODS/METHODS:Patients undergoing surgery for CD [defined as C2-C7 ≥10° kyphosis, cervical sagittal vertical axis (SVA) >4 cm, or C2-C7 coronal Cobb angle ≥10°] were included. CS was defined as C2-C7 coronal Cobb angle ≥10°. RESULTS:Totally, 114 patients were included (mean age 62.5 yr, 51.8% female). Fourteen patients (12.3%) had combined CS and CK, and 100 patients (87.7%) had CK alone. Preoperative maximum cervical coronal Cobb angle was 3.9° in the CK alone group and 14.6° in the combined CS and CK group. In the combined CS and CK group, this value improved to 8.1° postoperatively ( P =0.0007 vs. preoperative), but CS ≥10° was still present in three patients, with a mean correction percentage of only 48.0% of initial CS.No significant differences were observed between the CK only and combined CS and CK groups with regard to baseline sagittal parameters, change between immediate postoperative and baseline sagittal parameters, surgical approach, age, or baseline HRQOL. Patients with combined CS and CK were more frequently female than patients with CK alone (85.7% vs. 41.2%, P =0.0066). CONCLUSIONS:The vast majority of patients presented with CK alone (88%), and only 12% of adult CD patients had combined CS and CK. Because of the significant residual coronal plane deformity-∼50%-surgical correction should be focused on both coronal and sagittal plane deformity in the combined CS and CK group.

STUDY DESIGN/METHODS:Multicenter prospective study. OBJECTIVE:The present study investigates in-construct measurements of sagittal angles (SA) within the fusion from C2 to various thoracic vertebrae, which can be used as targets for CD correction. SUMMARY OF BACKGROUND DATA/BACKGROUND:Correcting cervical deformity (CD) has the potential to significantly improve patient function. However, previously described radiographic parameters cannot be measured intraoperatively. METHODS:Patients with CD that had a LIV at T1 or caudal were included. Patients were categorized into the failed outcome group if they had a cSVA of more than 4 cm within 3 months postoperatively. The in-construct measurements were based on patients' LIV. All patients had a C2-T1 SA. C2-T4 SA were compared between groups with LIV below T4, and C2-T10 SA between groups with LIV below T10. Change in C2-LIV SA described the correction within the fusion for each patient. Linear regression analysis was used to determine the C2-T1, C2-T4, C2-T10 SA measures corresponding to a cSVA = 4 cm.HRQL analysis was done in patients with 1-year follow-up. RESULTS:Among 143 patients (mean age 63, 60% female), 51% had radiographic failure. Multivariate regression showed that postoperative C2-T1 SA independently predicted failed alignment (OR = 1.22, CI 1.10-1.35; P < 0.001). A cSVA of 4 cm correlated with a C2-T1 SA of -9.6° and C2-T10 SA of 14.7° (r > 0.38, P < 0.05). ΔDJKA was found to significantly correlated with the C2-T10 SA (r > 0.57, P = 0.02). Though HRQL outcomes did not differ significantly between groups, greater C2-LIV SA correction was associated with improved neck pain (r > 0.42, P = 0.036). CONCLUSION/CONCLUSIONS:Failure to restore cSVA and development of DJK was independently associated with under correction as evidenced by significantly larger postoperative in-construct angles.

STUDY DESIGN/METHODS:Retrospective cohort study of patients undergoing single-level L5-S1 anterior or transforaminal lumbar interbody fusion between 2012 and 2024 at a single academic institution, with preoperative and one-year postoperative radiographic assessment of sagittal alignment parameters. OBJECTIVE:To quantify changes in lumbar pelvic angle (LPA), pelvic tilt (PT), global lumbar lordosis (L1-S1), regional lumbar lordosis (L4-S1), and segmental lumbar lordosis (L5-S1) among single-level L5-S1 ALIF and TLIF patients. SUMMARY OF BACKGROUND DATA/BACKGROUND:Restoration of sagittal alignment is a primary goal of lumbar fusion. While ALIF is regarded as superior to TLIF in restoring segmental lordosis, its effect on global and regional alignment remains uncertain, and few studies directly compare their impact on spinopelvic parameters. METHODS:The electronic medical record was queried for patients who underwent single-level L5-S1 ALIF or TLIF with preoperative and one-year postoperative imaging. Sagittal parameters were measured using Surgimap software. Group comparisons were assessed with unpaired t-tests or Wilcoxon signed-rank tests. RESULTS:Radiographic measurements were available for 174 patients (ALIF n=73, TLIF n=101). ALIF patients had significantly greater improvement in L4-S1 (+4.2° vs. -1.1°, P=0.002) and L5-S1 lordosis (+4.6° vs. -4.8°, P<0.001). No significant differences were observed in postoperative changes for L1-S1 lordosis (+2.2° vs. -1.4°, P=0.250), LPA (-1.9° vs. -1.4°, P=0.743), or PT (-0.9° vs. +0.4°, P=0.093). Permutation testing confirmed that the observed difference in LPA improvement between cohorts (-0.51°) was not statistically significant (P=0.673), and post hoc analysis confirmed adequate power to detect a difference of 3.37°. Sensitivity analyses using ANCOVA, adjusting for baseline radiographic values and covariates, were concordant. CONCLUSION/CONCLUSIONS:ALIF provided superior regional and segmental lordosis but did not improve global alignment compared with TLIF. This study is the first to quantify the effect of ALIF versus TLIF on LPA, highlighting the limited impact of single-level fusion on global spinopelvic alignment.

INTRODUCTION/BACKGROUND:The sacroiliac joint (SIJ) is a potential source of pain in the ASD population. Incidence and predictors of preoperative SIJ pain and rates of resolution with surgery in the ASD population are not well understood. METHODS:A prospective, multicenter database of surgically treated ASD patients was queried for baseline SIJ pain at the preoperative assessment. SIJ pain was defined as self-reported back pain in the posterior superior iliac spine region scored ≥4 out of 10 and ≥3 of 5 positive provocative SIJ maneuvers. Demographic data, spinal alignment parameters, and health assessments were assessed using Wilcoxon and χ 2 analysis. Predictors of preoperative SIJ pain were assessed with univariate and multivariate logistic regression. RESULTS:A total of 735 patients were included with a mean (SD) age of 61.3 (15.3) years, BMI of 27.6 (5.4), Edmonton Frailty Score (EFS) of 3.4 (2.5), and Charlson Comorbidity Index (CCI) of 1.1 (1.8). A total of 65% were female and 6% were tobacco users. A total of 411 patients had self-reported PSIS pain and 53 patients (7.2%) had preoperative SIJ pain as assessed by SIJ maneuver testing. SIJ pain was not associated with history of prior lumbosacral fusion ( P =0.23). Patients with SIJ pain had higher BMI (30.0 vs . 27.4, P =0.004), preoperative pain medication usage (92.5% vs . 77.7%, P =0.02), EFS (4.6 vs . 3.3, P <0.001), and CCI (1.6 vs . 1.0, P =0.006) as well as lower L4-S1 lordosis (28.7 vs . 34.5, P =0.02) and greater L1 pelvic angle (14.5 vs . 10.8, P =0.03). After variable selection with univariate regression, multivariate logistic regression identified higher BMI (OR 1.06, P =0.033) as a significant predictor of SIJ pain at preoperative. In the patient cohort with SIJ pain at preoperative, 91.7% reported no SIJ pain at 1-year follow-up. 11/53 (20.8%) patients with baseline pain and SIJ fusion performed concurrently with ASD surgery had 100% resolution of SIJ pain in this cohort; however, there was no significant difference in pain resolution between patients with SIJ fusion and those without ( P =1). CONCLUSION/CONCLUSIONS:We found a lower prevalence of preoperative SIJ pain in ASD patients than what has been historically reported, present in 7.2% of patients. Higher BMI was a predictor of preoperative SIJ pain in this population. ASD surgery led to resolution of SIJ pain in >90% of patients at 1-year follow-up.