Faculty Bibliography

STUDY DESIGN/METHODS:Retrospective. OBJECTIVE:To assess impact of surgical costs on patient reported outcomes in ASD. SUMMARY OF BACKGROUND DATA/BACKGROUND:With increased focus on delivering cost effective healthcare, interventions with high resource utilization, such as adult spinal deformity (ASD) surgery, have received greater scrutiny. METHODS:ASD patients≥18 years with BL and 2Y data were included. Surgical costs were calculated using 2021 average Medicare reimbursement by CPT code. Costs of complications and reoperations were intentionally excluded. Patients were ranked into tertiles by surgical cost: highest surgical costs (HC) and lowest surgical costs (LC). They were propensity score matched (PSM) to account for differences in baseline age and deformity. Bivariate logistic regressions assessed odds of achieving outcomes. RESULTS:421 patients met inclusion (60.7 y, 81.8% female, CCI: 1.6, 27.1 kg/m2), 139 LC and 127 HC patients. After PSM, 102 patients remained in each cost group with an average reimbursement of LC: $12,494 versus HC: $29,248. Matched cohorts had similar demographics and baseline HRQLs. Matched groups had similar baseline SVA (HC: 59.0 vs. LC: 56.7 mm), PI-LL (HC: 13.1 vs. LC: 13.4°), and PT (HC: 25.3 vs. LC: 22.4°). Rates of complications were not significantly different between the cost groups. Compared to LC group, by 2Y HC patients had higher odds of reaching SCB in ODI (OR: 2.356, [1.220, 4.551], P=0.011), in SRS-Total (OR: 2.988, [1.515, 5.895], P=0.002), and in NRS Back (OR: 2.739, [1.105, 6.788], P=0.030). Similar findings were appreciated for HC patients in the setting of Schwab deformity outcome criteria. CONCLUSIONS:Although added cost did not guarantee an ideal outcome, HC patients experienced superior patient reported outcomes compared to LC patients. While cost efficiency remains an important priority for health policy, isolating cost reduction may compromise outcomes and add to future costs of re-intervention, particularly with more severe baseline deformity. LEVEL OF EVIDENCE/METHODS:III.

BACKGROUND AND OBJECTIVES/OBJECTIVE:Achieving spinopelvic realignment during adult spinal deformity (ASD) surgery does not always produce ideal outcomes. Little is known whether compensation in lower extremities (LEs) plays a role in this disassociation. The objective is to analyze lower extremity compensation after complex ASD surgery, its effect on outcomes, and whether correction can alleviate these mechanisms. METHODS:We included patients with complex ASD with 6-week data. LE parameters were as follows: sacrofemoral angle, knee flexion angle, and ankle flexion angle. Each parameter was ranked, and upper tertile was deemed compensation. Patients compensating and not compensating postoperatively were propensity score matched for body mass index, frailty, and T1 pelvic angle. Linear regression assessed correlation between LE parameters and baseline deformity, demographics, and surgical details. Multivariate analysis controlling for baseline deformity and history of total knee/hip arthroplasty evaluated outcomes. RESULTS:Two hundred and ten patients (age: 61.3 ± 14.1 years, body mass index: 27.4 ± 5.8 kg/m2, Charlson Comorbidity Index: 1.1 ± 1.6, 72% female, 22% previous total joint arthroplasty, 24% osteoporosis, levels fused: 13.1 ± 3.8) were included. At baseline, 59% were compensating in LE: 32% at hips, 39% knees, and 36% ankles. After correction, 61% were compensating at least one joint. Patients undercorrected postoperatively were less likely to relieve LE compensation (odds ratio: 0.2, P = .037). Patients compensating in LE were more often undercorrected in age-adjusted pelvic tilt, pelvic incidence, lumbar lordosis, and T1 pelvic angle and disproportioned in Global Alignment and Proportion (P < .05). Patients matched in sagittal age-adjusted score at 6 weeks but compensating in LE were more likely to develop proximal junctional kyphosis (odds ratio: 4.1, P = .009) and proximal junctional failure (8% vs 0%, P = .035) than those sagittal age-adjusted score-matched and not compensating in LE. CONCLUSION/CONCLUSIONS:Perioperative lower extremity compensation was a product of undercorrecting complex ASD. Even in age-adjusted realignment, compensation was associated with global undercorrection and junctional failure. Consideration of lower extremities during planning is vital to avoid adverse outcomes in perioperative course after complex ASD surgery.

STUDY DESIGN/METHODS:Retrospective study. OBJECTIVE:Evaluate surgical characteristics and postoperative 2-year results of the PL approach to spinal fusion. SUMMARY OF BACKGROUND DATA/BACKGROUND:Prone-lateral(PL) single positioning has recently gained popularity in spine surgery due to lower blood loss and operative time but has yet to be examined for other notable outcomes, including realignment and patient-reported measures. MATERIALS AND METHODS/METHODS:We included circumferential spine fusion patients with a minimum one-year follow-up. Patients were stratified into groups based on undergoing PL approach versus same-day staged (Staged). Mean comparison tests identified differences in baseline parameters. Multivariable logistic regression, controlling for age, levels fused, and Charlson Comorbidity Index were used to determine the influence of the approach on complication rates, radiographic and patient-reported outcomes up to two years. RESULTS:One hundred twenty-two patients were included of which 72(59%) were same-day staged and 50(41%) were PL. PL patients were older with lower body mass index (both P <0.05). Patients undergoing PL procedures had lower estimated blood loss and operative time (both P <0.001), along with fewer osteotomies (63% vs. 91%, P <0.001). This translated to a shorter length of stay (3.8 d vs. 4.9, P =0.041). PL procedures demonstrated better correction in both PT (4.0 vs. -0.2, P =0.033 and pelvic incidence and lumbar lordosis (-3.7 vs. 3.1, P =0.012). PL procedures were more likely to improve in GAP relative pelvic version (OR: 2.3, [1.5-8.8]; P =0.003]. PL patients suffered lesser complications during the perioperative period and greater improvement in NRS-Back (-6.0 vs. -3.3, P =0.031), with less reoperations (0.0% vs. 4.8%, P =0.040) by two years. CONCLUSIONS:Patients undergoing PL single-position procedures received less invasive procedures with better correction of pelvic compensation, as well as earlier discharge. The prone lateral cohort also demonstrated greater clinical improvement and a lower rate of reoperations by two years following spinal corrective surgery. LEVEL OF EVIDENCE/METHODS:Level-III.

STUDY DESIGN/METHODS:Multicenter retrospective cohort study. OBJECTIVE:To investigate risk factors for loss of correction within the instrumented lumbar spine after adult spinal deformity surgery. SUMMARY OF BACKGROUND DATA/BACKGROUND:The sustainability of adult spinal deformity surgery remains a health care challenge. Malalignment is a major reason for revision surgery. PATIENTS AND METHODS/METHODS:A total of 321 patients who underwent fusion of the lumbar spine (≥5 levels, LIV pelvis) with a revision-free follow-up of ≥3 years were identified. Patients were stratified by a change in pelvic incidence-lumbar lordosis from 6 weeks to 3 years postoperative as "maintained" versus "loss" >5°. Those with instrumentation failure (broken rod, screw pullout, etc .) were excluded before comparisons. Demographics, surgical data, and radiographic alignment were compared. Repeated measure analysis of variance was performed to evaluate the maintenance of the correction for L1-L4 and L4-S1. Multivariate logistic regression was conducted to identify independent surgical predictors of correction loss. RESULTS:The cohort had a mean age of 64 years, a mean Body Mass Index of 28 kg/m 2 , and 80% females. Eighty-two patients (25.5%) lost >5° of pelvic incidence-lumbar lordosis correction (mean loss 10±5°). After the exclusion of patients with instrumentation failure, 52 losses were compared with 222 maintained. Demographics, osteotomies, 3CO, interbody fusion, use of bone morphogenetic protein, rod material, rod diameter, and fusion length were not significantly different. L1-S1 screw orientation angle was 1.3 ± 4.1 from early postoperative to 3 years ( P = 0.031), but not appreciably different at L4-S1 (-0.1 ± 2.9 P = 0.97). Lack of a supplemental rod (odds ratio: 4.0, P = 0.005) and fusion length (odds ratio 2.2, P = 0.004) were associated with loss of correction. CONCLUSIONS:Approximately, a quarter of revision-free patients lose an average of 10° of their 6-week correction by 3 years. Lordosis is lost proximally through the instrumentation ( i.e. tulip/shank angle shifts and/or rod bending). The use of supplemental rods and avoiding sagittal overcorrection may help mitigate this loss.

STUDY DESIGN/SETTING/METHODS:This was a retrospective cohort study. BACKGROUND:Little is known of the intersection between surgical invasiveness, cervical deformity (CD) severity, and frailty. OBJECTIVE:The aim of this study was to investigate the outcomes of CD surgery by invasiveness, frailty status, and baseline magnitude of deformity. METHODS:This study included CD patients with 1-year follow-up. Patients stratified in high deformity if severe in the following criteria: T1 slope minus cervical lordosis, McGregor's slope, C2-C7, C2-T3, and C2 slope. Frailty scores categorized patients into not frail and frail. Patients are categorized by frailty and deformity (not frail/low deformity; not frail/high deformity; frail/low deformity; frail/high deformity). Logistic regression assessed increasing invasiveness and outcomes [distal junctional failure (DJF), reoperation]. Within frailty/deformity groups, decision tree analysis assessed thresholds for an invasiveness cutoff above which experiencing a reoperation, DJF or not achieving Good Clinical Outcome was more likely. RESULTS:A total of 115 patients were included. Frailty/deformity groups: 27% not frail/low deformity, 27% not frail/high deformity, 23.5% frail/low deformity, and 22.5% frail/high deformity. Logistic regression analysis found increasing invasiveness and occurrence of DJF [odds ratio (OR): 1.03, 95% CI: 1.01-1.05, P =0.002], and invasiveness increased with deformity severity ( P <0.05). Not frail/low deformity patients more often met Optimal Outcome with an invasiveness index <63 (OR: 27.2, 95% CI: 2.7-272.8, P =0.005). An invasiveness index <54 for the frail/low deformity group led to a higher likelihood of meeting the Optimal Outcome (OR: 9.6, 95% CI: 1.5-62.2, P =0.018). For the frail/high deformity group, patients with a score <63 had a higher likelihood of achieving Optimal Outcome (OR: 4.8, 95% CI: 1.1-25.8, P =0.033). There was no significant cutoff of invasiveness for the not frail/high deformity group. CONCLUSIONS:Our study correlated increased invasiveness in CD surgery to the risk of DJF, reoperation, and poor clinical success. The thresholds derived for deformity severity and frailty may enable surgeons to individualize the invasiveness of their procedures during surgical planning to account for the heightened risk of adverse events and minimize unfavorable outcomes.

STUDY DESIGN/METHODS:Systematic review. OBJECTIVE:To assess the available evidence related to dose-dependent effectiveness (i.e., bone fusion) and morbidity of osteobiologics used in anterior cervical discectomy and fusion (ACDF). METHODS:Studies with more than 9 adult patients with degenerated/herniated cervical discs operated for one-to four-levels ACDF reporting used osteobiologics doses, fusion rates at six months or later, and related comorbidities were included. PubMed, EMBASE, ClinicalTrials, and Cochrane were searched through September 2021. Data extracted in spread sheet and risk of bias assessed using MINORS and Rob-2. RESULTS:Sixteen studies were selected and sub-grouped into BMP and non-BMP osteobiologics. For the 10 BMP studies, doses varied from 0.26 to 2.1 mg in 649 patients with fusion rates of 95.3 to 100% at 12 months. For other osteobiologics, each of six studies reported one type of osteobiologic in certain dose/concentration/volume in a total of 580 patients with fusion rates of 6.8 to 96.9% at 12 months. Risk of bias was low in three of the 13 non-randomized (18.75%) and in all the three randomized studies (100%). CONCLUSIONS:Taking into account the inconsistent reporting within available literature, for BMP usage in ACDF, doses lower than 0.7 mg per level can achieve equal successful fusion rates as higher doses, and there is no complication-free dose proved yet. It seems that the lower the dose the lower the incidence of serious complications. As for non-BMP osteobiologics the studies are very limited for each osteobiologic and thus conclusions must be drawn individually and with caution.

STUDY DESIGN/METHODS:Retrospective review. OBJECTIVE:To assess the factors contributing to durability of surgical results following adult spinal deformity surgery. SUMMARY OF BACKGROUND/BACKGROUND:Factors contributing to the long-term sustainability of ASD correction are currently undefined. METHODS:Operative ASD patients with preop(BL) and 3-year(3Y) postop radiographic/HRQL data were included. At 1Y and 3Y postop, a favorable outcome was defined as meeting at least 3 of 4 criteria: 1) no PJF or mechanical failure with reoperation, 2) best clinical outcome for SRS[≥4.5] or ODI[<15], 3) improving in at least one SRS-Schwab modifier, and 4) not worsening in any SRS-Schwab modifier. A robust surgical result was defined as having a favorable outcome at both 1Y and 3Y. Predictors of robust outcomes were identified using multivariable regression analysis, with conditional inference tree (CIT) for continuous variables. RESULTS:We included 157 ASD patients in this analysis. At 1Y postop, 62 patients (39.5%) met the best clinical outcome [BCO] definition for ODI and 33 (21.0%) met the BCO for SRS. At 3Y, 58 patients (36.9%) had BCO for ODI and 29 (18.5%) for SRS. 95 patients (60.5%) were identified as having a favorable outcome at 1Y postop. At 3Y, 85 patients (54.1%) had a favorable outcome. Seventy-eight (49.7%) patients met criteria for a durable surgical result. Multivariable adjusted analysis identified the following independent predictors of surgical durability: surgical invasiveness >65, being fused to S1/pelvis, baseline to 6 week PI-LL difference >13.9°, and having a proportional Global Alignment and Proportion (GAP) score at 6 weeks. CONCLUSIONS:Nearly 50% of the ASD cohort demonstrated good surgical durability, with favorable radiographic alignment and functional status maintained up to 3 years. Surgical durability was more likely in patients whose reconstruction was fused to the pelvis and addressed lumbopelvic mismatch with adequate surgical invasiveness to achieve full alignment correction.

STUDY DESIGN/SETTING/METHODS:Retrospective single-center study. BACKGROUND:The global alignment and proportion score is widely used in adult spinal deformity surgery. However, it is not specific to the parameters used in adult cervical deformity (ACD). PURPOSE/OBJECTIVE:Create a cervicothoracic alignment and proportion (CAP) score in patients with operative ACD. METHODS:Patients with ACD with 2-year data were included. Parameters consisted of relative McGregor's Slope [RMGS = (MGS × 1.5)/0.9], relative cervical lordosis [RCL = CL - thoracic kyphosis (TK)], Cervical Lordosis Distribution Index (CLDI = C2 - Apex × 100/C2 - T2), relative pelvic version (RPV = sacral slope - pelvic incidence × 0.59 + 9), and a frailty factor (greater than 0.33). Cutoff points were chosen where the cross-tabulation of parameter subgroups reached a maximal rate of meeting the Optimal Outcome. The optimal outcome was defined as meeting Good Clinical Outcome criteria without the occurrence of distal junctional failure (DJF) or reoperation. CAP was scored between 0 and 13 and categorized accordingly: ≤3 (proportioned), 4-6 (moderately disproportioned), >6 (severely disproportioned). Multivariable logistic regression analysis determined the relationship between CAP categories, overall score, and development of distal junctional kyphosis (DJK), DJF, reoperation, and Optimal Outcome by 2 years. RESULTS:One hundred five patients with operative ACD were included. Assessment of the 3-month CAP score found a mean of 5.2/13 possible points. 22.7% of patients were proportioned, 49.5% moderately disproportioned, and 27.8% severely disproportioned. DJK occurred in 34.5% and DJF in 8.7%, 20.0% underwent reoperation, and 55.7% achieved Optimal Outcome. Patients severely disproportioned in CAP had higher odds of DJK [OR: 6.0 (2.1-17.7); P =0.001], DJF [OR: 9.7 (1.8-51.8); P =0.008], reoperation [OR: 3.3 (1.9-10.6); P =0.011], and lower odds of meeting the optimal outcome [OR: 0.3 (0.1-0.7); P =0.007] by 2 years, while proportioned patients suffered zero occurrences of DJK or DJF. CONCLUSION/CONCLUSIONS:The regional alignment and proportion score is a method of analyzing the cervical spine relative to global alignment and demonstrates the importance of maintaining horizontal gaze, while also matching overall cervical and thoracolumbar alignment to limit complications and maximize clinical improvement.

BACKGROUND:The Roussouly, SRS-Schwab, and Global Alignment and Proportion (GAP) classifications define alignment by spinal shape and deformity severity. The efficacy of different surgical approaches and techniques to successfully achieve these goals is not well understood. PURPOSE/OBJECTIVE:Identify the impact of surgical approach and/or technique on meeting complex realignment goals in adult spinal deformity (ASD) corrective surgery. STUDY DESIGN/SETTING/METHODS:Retrospective study. MATERIALS AND METHODS/METHODS:Included patients with ASD fused to pelvis with 2-year data. Patients were categorized by: (1) Roussouly: matching current and theoretical spinal shapes, (2) improving in SRS-Schwab modifiers (0, +, ++), and (3) improving GAP proportionality by 2 years. Analysis of covariance and multivariable logistic regression analyses controlling for age, levels fused, baseline deformity, and 3-column osteotomy usage compared the effect of different surgical approaches, interbody, and osteotomy use on meeting realignment goals. RESULTS:A total of 693 patients with ASD were included. By surgical approach, 65.7% were posterior-only and 34.3% underwent anterior-posterior approach with 76% receiving an osteotomy (21.8% 3-column osteotomy). By 2 years, 34% matched Roussouly, 58% improved in GAP, 45% in SRS-Schwab pelvic tilt (PT), 62% sagittal vertical axis, and 70% pelvic incidence-lumbar lordosis. Combined approaches were most effective for improvement in PT [odds ratio (OR): 1.7 (1.1-2.5)] and GAP [OR: 2.2 (1.5-3.2)]. Specifically, anterior lumbar interbody fusion (ALIF) below L3 demonstrated higher rates of improvement versus TLIFs in Roussouly [OR: 1.7 (1.1-2.5)] and GAP [OR: 1.9 (1.3-2.7)]. Patients undergoing pedicle subtraction osteotomy at L3 or L4 were more likely to improve in PT [OR: 2.0 (1.0-5.2)] and pelvic incidence-lumbar lordosis [OR: 3.8 (1.4-9.8)]. Clinically, patients undergoing the combined approach demonstrated higher rates of meeting SCB in Oswestry Disability Index by 2 years while minimizing rates of proximal junctional failure, most often with an ALIF at L5-S1 [Oswestry Disability Index-SCB: OR: 1.4 (1.1-2.0); proximal junctional failure: OR: 0.4 (0.2-0.8)]. CONCLUSIONS:Among patients undergoing ASD realignment, optimal lumbar shape and proportion can be achieved more often with a combined approach. Although TLIFs, incorporating a 3-column osteotomy, at L3 and L4 can restore lordosis and normalize pelvic compensation, ALIFs at L5-S1 were most likely to achieve complex realignment goals with an added clinical benefit and mitigation of junctional failure.

BACKGROUND:Postoperative reciprocal changes (RC) in the cervical spine associated with varying factors of proximal junctional kyphosis (PJK) following fusions of the thoracopelvic spine are poorly understood. PURPOSE/OBJECTIVE:Explore reciprocal changes in the cervical spine associated with varying factors (severity, progression, patient age) of PJK in patients undergoing adult spinal deformity (ASD) correction. PATIENTS AND METHODS/METHODS:Retrospective review of a multicenter ASD database. INCLUSION/METHODS:ASD patients > 18 y/o, undergoing fusions from the thoracic spine (UIV: T6-T12) to the pelvis with two-year radiographic data. ASD was defined as: Coronal Cobb angle ≥ 20°, Sagittal Vertical Axis ≥ 5 cm, Pelvic Tilt ≥ 25°, and/or Thoracic Kyphosis ≥ 60°. PJK was defined as a ≥ 10° measure of the sagittal Cobb angle between the inferior endplate of the UIV and the superior endplate of the UIV + 2. Patients were grouped by mild (M; 10°-20°) and severe (S; > 20°) PJK at one year. Propensity Score Matching (PSM) controlled for CCI, age, PI and UIV. Unpaired and paired t test analyses determined difference between RC parameters and change between time points. Pearson bi-variate correlations analyzed associations between RC parameters (T4-T12, TS-CL, cSVA, C2-Slope, and T1-Slope) and PJK descriptors. RESULTS:284 ASD patients (UIV: T6: 1.1%; T7: 0.7%; T8: 4.6%; T9: 9.9%; T10: 58.8%; T11: 19.4%; T12: 5.6%) were studied. PJK analysis consisted of 182 patients (Mild = 91 and Severe = 91). Significant difference between M and S groups were observed in T4-T12 Δ1Y(- 16.8 v - 22.8, P = 0.001), TS-CLΔ1Y(- 0.6 v 2.8, P = 0.037), cSVAΔ1Y(- 1.8 v 1.9, P = 0.032), and C2 slopeΔ1Y(- 1.6 v 2.3, P = 0.022). By two years post-op, all changes in cervical alignment parameters were similar between mild and severe groups. Correlation between age and cSVAΔ1Y(R = 0.153, P = 0.034) was found. Incidence of severe PJK was found to correlate with TS-CLΔ1Y(R = 0.142, P = 0.049), cSVAΔ1Y(R = 0.171, P = 0.018), C2SΔ1Y(R = 0.148, P = 0.040), and T1SΔ2Y(R = 0.256, P = 0.003). CONCLUSIONS:Compensation within the cervical spine differed between individuals with mild and severe PJK at one year postoperatively. However, similar levels of pathologic change in cervical alignment parameters were seen by two years, highlighting the progression of cervical compensation due to mild PJK over time. These findings provide greater evidence for the development of cervical deformity in individuals presenting with proximal junctional kyphosis.