Faculty Bibliography

BACKGROUND:Recent studies have suggested achieving global alignment and proportionality (GAP) alignment may influence mechanical complications after adult spinal deformity (ASD) surgery. OBJECTIVE:To investigate the association between the GAP score and mechanical complications after ASD surgery. METHODS:Patients with ASD with at least 5-level fusion to pelvis and minimum 2-year data were included. Multivariate analysis was used to find an association between proportioned (P), GAP-moderately disproportioned, and severely disproportioned (GAP-SD) states and mechanical complications (inclusive of proximal junctional kyphosis [PJK], proximal junctional failure [PJF], and implant-related complications [IC]). Severe sagittal deformity was defined by a "++" in the Scoliosis Research Society (SRS)-Schwab criteria for sagittal vertebral axis or pelvic incidence and lumbar lordosis. RESULTS:Two hundred ninety patients with ASD were included. Controlling for age, Charlson comorbidity index, invasiveness and baseline deformity, and multivariate analysis showed no association of GAP-moderately disproportioned patients with proximal junctional kyphosis, PJF, or IC, while GAP-SD patients showed association with IC (odds ratio [OR]: 1.7, [1.1-3.3]; P = .043). Aligning in GAP-relative pelvic version led to lower likelihood of all 3 mechanical complications (all P < .04). In patients with severe sagittal deformity, GAP-SD was predictive of IC (OR: 2.1, [1.1-4.7]; P = .047), and in patients 70 years and older, GAP-SD was also predictive of PJF development (OR: 2.5, [1.1-14.9]; P = .045), while improving in GAP led to lower likelihood of PJF (OR: 0.2, [0.02-0.8]; P = .023). CONCLUSION/CONCLUSIONS:Severely disproportioned in GAP is associated with development of any IC and junctional failure specifically in older patients and those with severe baseline deformity. Therefore, incorporation of patient-specific factors into realignment goals may better strengthen the utility of this novel tool.

Study Design: Retrospective review of prospective database. Objectives: Vertebral pelvic angles (VPAs) account for complexity in spine shape by assessing the relative position of each vertebra with regard to the pelvis. This study uses VPAs to investigate the shape of the fused spine after T10-pelvis fusion, in patients with adult spinal deformity (ASD), and then explores its association with proximal junctional kyphosis (PJK). Methods: Included patients had radiographic evidence of ASD and underwent T10-pelvis realignment. VPAs were used to construct a virtual shape of the post-operative spine. VPA-predicted and actual shapes were then compared between patients with and without PJK. Logistic regression was used to identify components of the VPA-based model that were independent predictors of PJK occurrence and post-operative shape. Results: 287 patients were included. VPA-predicted shape was representative of the true post-operative contour, with a mean point-to-point error of 1.6-2.9% of the T10-S1 spine length. At 6-weeks follow-up, 102 patients (35.5%) developed PJK. Comparison of the true post-operative shapes demonstrated that PJK patients had more posteriorly translated vertebrae from L3 to T7 (P <.001). Logistic regression demonstrated that L3PA (P =.047) and T11PA (P <.001) were the best independent predictors of PJK and were, in conjunction with pelvic incidence, sufficient to reproduce the actual spinal contour (error <3%). Conclusions: VPAs are reliable in reproducing the true, post-operative spine shape in patients undergoing T10-pelvis fusion for ASD. Because VPAs are independent of patient position, L3PA, T11PA, and PI measurements can be used for both pre- and intra-operative planning to ensure optimal alignment.

PURPOSE/OBJECTIVE:To explore the changes in health-related quality of life parameters observed in patients experiencing varying degrees of proximal junctional kyphosis following corrective adult spinal deformity fusions. METHODS:and ≤ 28°. ANOVA, followed by ANCOVA, compared the change in HRQoLs between time points (BL, 1Y, 2Y) among PJK groups. Correlation-related change in PJK and change in HRQoL for mild and severe groups. RESULTS:969 patients (age: 64.5 y/o,75% F, posterior levels fused:12.3) were studied. 59% no PJK, 32% mild PJK, 9% severe PJK. No differences in HRQoLs were seen between no PJK and PJK groups at baseline, one year, and 2 years. Adjusted analysis revealed Severe PJK patients improved less in SRS-22 Satisfaction (NoPJK: 1.6, MildPJK: 1.6, SeverePJK: 1.0; p = 0.022) scores at 2 years. Linear regression analysis only found clinical improvement in SRS-22 Satisfaction to correlate with the change of the PJK angle by 2 years (R = 0.176, P = 0.008). No other HRQoL metric correlated with either the incidence of PJK or the change in the PJK angle by one or 2 years. CONCLUSIONS:These results maintain that patients presenting with and without proximal junctional kyphosis report similar health-related qualities of life following corrective adult spinal deformity surgery, and SRS-22 Satisfaction may be a clinical correlate to the degree of PJK. Rather than proving proximal junctional kyphosis to have a minimal clinical impact overall on HRQoL metrics, these data suggest that future analysis of this phenomenon requires different assessments. LEVEL OF EVIDENCE/METHODS:Level of evidence: III.

PURPOSE/OBJECTIVE:To determine the proportions of patients returning to work at various points after adult spinal deformity (ASD) surgery and the associations between surgical invasiveness and time to return to work. METHODS:Using a multicenter database of patients treated surgically for ASD from 2008 to 2015, we identified 188 patients (mean age 51 ± 15 years) who self-reported as employed preoperatively and had 2-year follow-up. Per the ASD-Surgical and Radiographical Invasiveness Index (ASD-SR), 118 patients (63%) underwent high-invasiveness (HI) surgery (ASD-SR ≥ 100) and 70 (37%) had low-invasiveness (LI) surgery (ASD-SR < 100). Patients who self-reported ≥ 75% normal level of work/school activity were considered to be working full time. Chi-squared and Fisher exact tests were used to compare categorical variables (α = .05). RESULTS:Preoperatively, 69% of employed patients worked full time. Postoperatively, 15% of employed patients were full time at 6 weeks, 70% at 6 months, 83% at 1 year, and 84% at 2 years. Percentage of employed patients working full time at 2 years was greater than preoperatively (p < .001); percentage of patients returning to full time at 6 weeks was lower in the HI (5%) than in the LI group (19%) (p = .03), a difference not significant at later points. CONCLUSIONS:Most adults returned to full-time work after ASD surgery. A smaller percentage of patients in the HI group than in the LI group returned to full-time work at 6 weeks. Patients employed full time preoperatively will likely return to full-time employment after ASD surgery. LEVEL OF EVIDENCE/METHODS:III.

STUDY DESIGN/METHODS:Retrospective Cohort Study. OBJECTIVE:Assess whether modifying spinal alignment goals to accommodate frailty considerations will decrease mechanical complications and maximize clinical outcomes. SUMMARY OF BACKGROUND DATA/BACKGROUND:The Global Alignment and Proportion(GAP) score was developed to assist in reducing mechanical complications, but has had less success predicting such events in external validation. Higher frailty and many of its components have been linked to development of implant failure. Therefore, modifying the GAP score with frailty may strengthen its ability to predict mechanical complications. METHODS:We included 412 surgical ASD patients with two-year(2Y) follow-up. Frailty was quantified using the ASD modified Frailty Index(mASD-FI). Outcomes: proximal junctional kyphosis(PJK) and failure(PJF), major mechanical complications, and 'Best Clinical Outcome'(BCO), defined as ODI<15 and SRS-22 Total>4.5. Logistic regression analysis established a six-week score based on GAP score,frailty and ODI US-Norms. Logistic regression followed by conditional inference tree(CIT) analysis generated categorical thresholds. Multivariable logistic regression analysis controlling for confounders was used to assess the performance of the frailty modified GAP score. RESULTS:Baseline frailty categories: 57% Not Frail,30% frail,14% severely frail. Overall, 39% of patients developed PJK, 8% PJF, 21% mechanical complications, 22% underwent reoperation, and 15% met BCO. The modified ASD-FI demonstrated correlation with developing PJF, mechanical complications, undergoing reoperation, and meeting BCO at 2Y(all P<0.05). Regression analysis generated the following equation: Frailty-Adjusted Realignment Score(FAR Score) =0.49*mASD-FI + 0.38*GAP Score. Thresholds for the FAR score(0-13): Proportioned:<3.5,Moderately Disproportioned:3.5-7.5,Severely Disproportioned:>7.5. Multivariable logistic regression assessing FAR Score demonstrated associations with mechanical complications, reoperation, and meeting Best Clinical Outcome by two years(all P<0.05), whereas the original GAP score was only significant for reoperation. CONCLUSION/CONCLUSIONS:This study demonstrated adjusting alignment goals in adult spinal deformity surgery for a patient's baseline frailty status and disability may be useful in minimizing the risk of complications and adverse events, outperforming the original GAP score in terms of prognostic capacity. LEVEL OF EVIDENCE/METHODS:III.

STUDY DESIGN/METHODS:Retrospective cohort. OBJECTIVE:To assess whether patient outcomes and cost effectiveness of adult spinal deformity (ASD) surgery have improved over the past decade. BACKGROUND:Surgery for ASD is an effective intervention, but one that is also associated with large initial healthcare expenditures. Changes in the cost profile for ASD surgery over the last decade has not been evaluated previously. METHODS:ASD patients who received surgery between 2008-19 were included. ANCOVA was used to marginal means for outcome measures (complication rates, reoperations, HRQLs, total cost, utility gained, QALYs, cost efficiency [cost per QALY]) by year of initial surgery. Cost was calculated using the PearlDiver database and represented national averages of Medicare reimbursement for services within a 30-day window including length of stay and death differentiated by complication/comorbidity, revision, and surgical approach. Internal cost data was based on individual patient DRG codes, limiting revisions to those within 2Y of the initial surgery. Cost per QALY over the course of 2008-2019 were then calculated. RESULTS:There were 1236 patients included. There was an overall decrease in rates of any complication (0.78 vs. 0.61), any reoperation (0.25 vs. 0.10), and minor complication (0.54 vs. 0.37) between 2009 and 2018 (all P<0.05). National average 2Y cost decreased at an annual rate of $3,194 (R2=0.6602), 2Y Utility Gained increased at an annual rate of 0.0041 (R2=0.57), 2Y QALYs Gained increased annually by 0.008 (R2=0.57), and 2Y Cost per QALY decreased per year by $39,953 (R2=0.6778). CONCLUSION/CONCLUSIONS:Between 2008 and 2019, rates of complications have decreased concurrently with improvements in patient reported outcomes, resulting in improved cost effectiveness according to national Medicare average and individual patient cost data. The value of ASD surgery has improved substantially over the course of the last decade.

PURPOSE/OBJECTIVE:Despite adequate correction, the pelvis may fail to readjust, deemed pelvic non-response. To assess alignment outcomes(pelvic non-response[PNR], PJK, postoperative cervical deformity[CD]) following ASD surgery utilizing different realignment strategies. METHODS:ASD patients with 2-year(2Y) data were included. PNR defined as undercorrected in age-adjusted pelvic tilt(PT) at 6W and maintained at 2Y. Patients classified by alignment utilities: [a] Improvement in SRS-Schwab SVA,[b] Matching in age-adjusted PI-LL,[c] Matching in Roussouly,[d] aligning Global Alignment and Proportionality(GAP) score. Multivariable regression analyses, controlling for age, baseline deformity, and surgical factors, assessed rates of PNR, PJK, and CD development following realignment. RESULTS:686 patients met inclusion criteria. Rates of postop PJK and CD were not significant in the PNR group(both P>0.15). PNR patients less often met substantial clinical benefit in ODI by 2Y(OR: 0.6,[0.4-0.98]). Patients overcorrected in age-adjusted PI-LL, matching Roussouly, or proportioned in GAP at 6W had lower rates of PNR(all P<0.001). Incremental addition of classifications led to 0% occurrence of PNR, PJK and CD. Stratifying by baseline PT severity, Low and Moderate deformity demonstrated the least incidence of PNR(7.7%) when proportioning in GAP at 6W, while severe PT benefited most from matching in Roussouly(all P<0.05). CONCLUSIONS:Following ASD corrective surgery, 24.9% of patients showed residual pelvic malalignment. This occurrence was often accompanied by undercorrection of lumbopelvic mismatch and less improvement of pain. However, overcorrection in any strategy incurred higher rates of PJK. We recommend surgeons identify a middle ground using one, or more, of the available classifications to inform correction goals in this regard. LEVEL OF EVIDENCE/METHODS:III.

STUDY DESIGN/METHODS:Retrospective cohort study. OBJECTIVE:Understand the benefit of addressing malalignment in revision surgery for PJK. SUMMARY OF BACKGROUND DATA/BACKGROUND:Proximal junctional kyphosis(PJK) is a common cause of revision surgery for ASD patients. During a revision, surgeons may elect to perform a proximal extension of the fusion, or also correct the source of the lumbo-pelvic mismatch. METHODS:Recurrent PJK following revision surgery was the primary outcome. Revision surgical strategy was the primary predictor(proximal extension of fusion alone compared to combined sagittal correction and proximal extension). Multivariable logistic regression determined rates of recurrent PJK between the two surgical groups with lumbo-pelvic surgical correction assessed through improving ideal alignment in one or more alignment criteria(Global Alignment and Proportionality[GAP],Roussouly-type, and Sagittal Age-Adjusted Score[SAAS]). RESULTS:151 patients underwent revision surgery for PJK. PJK occurred at a rate of 43.0%, and PJF at 12.6%. Patients proportioned in GAP post-revision had lower rates of recurrent PJK(23% vs. 42%;OR: 0.3,95% CI:[0.1-0.8];P=0.024). Following adjusted analysis, patients who were ideally aligned in 1 of 3 criteria (Matching in SAAS and/or Roussouly matched and/or achieved GAP proportionality) had lower rates of recurrent PJK (36% vs. 53%;OR: 0.4,95% CI:[0.1-0.9];P=0.035) and recurrent PJF(OR: 0.1,95% CI:[0.02-0.7];P=0.015). Patients ideally aligned in 2 of 3 criteria avoid any development of PJF(0% vs. 16%, P<0.001). CONCLUSION/CONCLUSIONS:Following revision surgery for proximal junctional kyphosis, patients with persistent poor sagittal alignment showed increased rates of recurrent proximal junctional kyphosis compared with patients who had abnormal lumbo-pelvic alignment corrected during the revision. These findings suggest addressing the root cause of surgical failure in addition to proximal extension of the fusion may be beneficial.

BACKGROUND:Patients with less severe adult spinal deformity undergo surgical correction and often achieve good clinical outcomes. However, it is not well understood how much clinical improvement is due to sagittal correction rather than treatment of the spondylotic process. PURPOSE/OBJECTIVE:Determine baseline thresholds in radiographic parameters that, when exceeded, may result in substantive clinical improvement from surgical correction. STUDY DESIGN/METHODS:Retrospective. METHODS:ASD patients with BL and 2-year(2Y) data were included. Parameters assessed: SVA, PI-LL, PT, T1PA, L1PA, L4-S1 Lordosis, C2-C7 SVA(cSVA), C2-T3, C2 Slope(C2S). Outcomes: Good Outcome(GO) at 2Y: [Meeting either: 1) SCB for ODI(change greater than 18.8), or 2) ODI<15 and SRS-Total>4.5. Binary logistic regression assessed each parameter to determine if correction was more likely needed to achieve GO. Conditional inference tree(CIT) run machine learning analysis generated baseline thresholds for each parameter, above which, correction was necessary to achieve GO. RESULTS:We included 431 ASD patients. There were 223(50%) that achieved a GO by two years. Binary logistic regression analysis demonstrated, with increasing baseline severity in deformity, sagittal correction was more often seen in those achieving GO for each parameter(all P<0.001). Of patients with baseline T1PA above the threshold, 95% required correction to meet Good Outcome(95% vs. 54%,P<0.001). A baseline PI-LL above 10° (74% of patients meeting GO) needed correction to achieve GO (OR: 2.6,[95% CI 1.4-4.8]). A baseline C2 slope above 15° also necessitated correction to obtain clinical success (OR: 7.7,[95% CI 3.7-15.7]). CONCLUSION/CONCLUSIONS:Our study highlighted point may be present at which sagittal correction has an outsized influence on clinical improvement, reflecting the line where deformity becomes a significant contributor to disability. These new thresholds give us insight into which patients may be more suitable for sagittal correction, as opposed to intervention for the spondylotic process only, leading to a more efficient utility of surgical intervention for adult spinal deformity. LEVEL OF EVIDENCE/METHODS:III.