Faculty Bibliography

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. 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.

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.

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.

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 review of a multicenter comprehensive cervical deformity (CD) database. OBJECTIVE:To develop a novel risk index specific to each patient to aid in patient counseling and surgical planning to minimize postop DJK occurrence. BACKGROUND:Distal junctional kyphosis(DJK) is a radiographic finding identified after patients undergo instrumented spinal fusions which can result in sagittal spinal deformity, pain and disability, and potentially neurological compromise. DJK is considered multifactorial in nature and there is a lack of consensus on the true etiology of DJK. METHODS:CD pts with baseline(BL) and at least 1-year postoperative(1Y) radiographic follow-up were included. A patient-specific DJK score was created through use of unstandardized Beta weights of a multivariate regression model predicting DJK(end of fusion construct to the 2nd distal vertebra change in this angle by<-10° from BL to postop). RESULTS:110 CD pts included(61yrs, 66.4%F, 28.8kg/m2). 31.8% of these pts developed DJK (16.1% 3M, 11.4% 6M, 62.9% 1Y). At BL, DJK pts were more frail and underwent combined approach more (both P<0.05). Multivariate model regression analysis identified individualized scores through creation of a DJK equation: -0.55+0.009(BL Inclination) -0.078(Pre Inflection)+5.9×10-5(BL LIV angle) + 0.43(combine approach) - 0.002(BL TS-CL)- 0.002(BL PT)- 0.031(BL C2-C7)+ 0.02(∆T4-T12)+ 0.63(Osteoporosis)- 0.03(anterior approach) - 0.036( Frail) - 0.032(3 column osteotomy). This equation has a 77.8% accuracy of predicting DJK. A score ≥81 predicted DJK with an accuracy of 89.3%. The BL reference equation correlated with 2Y outcomes of NSR-Back percentage(P=0.003), reoperation(P=0.04), and MCID for EQ. 5D(P=0.04). CONCLUSIONS:This study proposes a novel risk index of DJK development that focuses on potentially modifiable surgical factors as well as established patient-related and radiographic determinants. The reference model created demonstrated strong correlations with relevant two year outcome measures, including axial pain-related symptoms, occurrence of related reoperations, and the achievement of minimal clinically importance differences for EQ. 5D.

STUDY DESIGN/SETTING/METHODS:Retrospective review of a prospectively collected database. OBJECTIVE:The objective of this study was to determine the relationship between paracervical muscle area, density, and fat infiltration and cervical alignment among patients presenting with cervical spine pathology. BACKGROUND CONTEXT/BACKGROUND:The impact of cervical spine alignment on clinical outcomes has been extensively studied, but little is known about the association between spinal alignment and cervical paraspinal musculature. METHODS:We examined computed tomography scans and radiographs for patients presenting with cervical spine pathology. The posterior paracervical muscle area, density, and fat infiltration was calculated on axial slices at C2, C4, C6, and T1. We measured radiographic parameters including cervical sagittal vertical axis, cervical lordosis, T1 slope (T1S), range of motion of the cervical spine. We performed Pearson correlation tests to determine if there were significant relationships between muscle measurements and alignment parameters. RESULTS:The study included 51 patients. The paracervical muscle area was higher for males at C2 (P=0.005), C4 (P=0.001), and T1 (P=0.002). There was a positive correlation between age and fat infiltration at C2, C4, C6, and T1 (all P<0.05). The cervical sagittal vertical axis positively correlated with muscle cross-sectional area at C2 (P=0.013) and C4 (P=0.013). Overall cervical range of motion directly correlated with muscle density at C2 (r=0.48, P=0.003), C4 (r=0.41, P=0.01), and C6 (r=0.53. P<0.001) and indirectly correlated with fat infiltration at C2 (r=-0.40, P=0.02), C4 (r=-0.32, P=0.04), and C6 (r=-0.35, P=0.02). Muscle density correlated directly with reserve of extension at C2 (r=0.57, P=0.009), C4 (r=0.48, P=0.037), and C6 (r=0.47, P=0.033). Reserve of extension indirectly correlated with fat infiltration at C2 (r=0.65, P=0.006), C4 (r=0.47, P=0.037), and C6 (r=0.48, P=0.029). CONCLUSIONS:We have identified specific changes in paracervical muscle that are associated with a patient's ability to extend their cervical spine.

BACKGROUND CONTEXT: Bone Morphogenetic Protein-2 (BMP-2) has not shown superior benefit in terms of overall cost-effectiveness after implementation during adult spinal deformity (ASD) surgery. However, it remains to be shown whether certain discrete populations do obtain cost-utility from use of BMP-2. PURPOSE: Generate a score to determine usage of BMP-2 and correlate with rates of pseudarthrosis. STUDY DESIGN/SETTING: Retrospective cohort study of a single-center ASD database. PATIENT SAMPLE: A total of 689 ASD patients. OUTCOME MEASURES: Cost utility, pseudarthrosis.
METHOD(S): ASD patients with BL and 2-year(2Y) data included. BMP-2 kit size and cost: small - 4.2 mg ($21,800), medium - 8.4 mg ($23,667), large - 12 mg ($25,617). Published methods converted ODI to SF-6D. QALYs utilized a 3% discount rate for residual decline. Cost was calculated using the PearlDiver database and assessed for Complications and Comorbidities and Major Complications and Comorbidities according to CMS.gov definitions. Binary logistic regression analyses determined significant predictors for development of pseudarthrosis. Established weights were generated for predictive variables via back-step logistic regression for a risk score to predict development of pseudarthrosis. Risk score was then validated via Receiver Operating Characteristic (ROC) curve method analysis. Categories via conditional inference tree (CIT) analysis-derived thresholds were tested for cost-utility of BMP-2 usage. Marginalized means for utility gained and Cost per QALY were calculated within each risk score category, controlling for age, history of prior fusion, and baseline deformity and disability.
RESULT(S): Included: 387 ASD patients. Of 387, 64% received BMP-2 (1% small, 4% medium, 59% large). There were 17 (4.4%) of patients that developed pseudarthrosis by two years, 9 (2.3%) of which underwent reoperation. BMP-2 use, regardless of kit size, did not significantly lower pseudarthrosis rates overall (OR: 0.4, [0.2-1.04]). A predictive risk score for development of pseudarthrosis was formed by the following preoperative variables: age, frailty, history of diabetes, osteoporosis, depression, ASA grade, and baseline L4-S1 and T1PA. Via ROC method, this predictive risk score generated an AUC of 0.87. Following CIT machine learning, thresholds for the BMP Risk Score were derived: >5 No Risk (NoR), 3-5 Low Risk (LowR), 2-3 Moderate Risk (ModR), and <2 High Risk (HighR). The rates of pseudarthrosis for each category were: NoR - 0%; LowR - 1.6%; ModR - 9.3%; HighR - 24.3%. When assessing BMP-2 use and its cost-utility within each group, patients receiving BMP-2 had similar QALYs to those that did not receive BMP-2 (0.163 vs 0.171, p=.65). BMP-2 usage had significantly worse cost-utility in both NoR and LowR cohorts (both p<.05). In ModR patients, BMP-2 usage had equivocal cost-utility ($680,532.35 vs $580,380.21, p=.14). In the HighR cohort, the cost-utility difference narrowed even further (BMP-2 use: $743,155.21 vs $719,628.79, p=.82).
CONCLUSION(S): Our study shows BMP-2 has equivocal cost-utility within those at moderate and high risk for developing pseudarthrosis within two years following spinal deformity correction. The generated predictive score can better aid spine surgeons assess risk and enhance justification for the use of BMP-2 during surgical intervention for adult spinal deformity. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: As surgical techniques for deformity correction evolve towards minimizing tissue trauma, further clarity is warranted to define differences in complication profiles between cMIS and open surgeries. PURPOSE: To compare cMIS and open surgery reoperation rates and identify contributing etiologies to reoperation in each cohort. STUDY DESIGN/SETTING: Prospective multicenter observational series. PATIENT SAMPLE: Database enrollment required age =18 years, adult spinal deformity and circumferential minimally invasive spine surgery. OUTCOME MEASURES: Reoperation rate, patient reported outcomes (PROMS), spinopelvic parameters, mechanical failures (defined as rod breakage/dislocation, screw breakage/loosening, set screw loosening, proximal/distal junctional kyphosis, pseudoarthrosis) and other factors contributing to re-operation such as wound infection, medial breach, nerve impingement by screw, vertebral body fracture, sagittal/coronal imbalance, and wound infection.
METHOD(S): A total of 85 patients (pts) with cMIS for ASD with 2-year follow-up (2YFU) were identified and propensity matched to 85 patients in open cohort. Propensity matching was performed based on pre-operative PT, PI-LL, BMI, and SVA. Patient demographic variables, reoperation rate, and complications contributing to reoperation were compared with uni- and multi-variate analysis at any time in each cohort (33 open, 17 cMIS). PROMS at 2YFU were compared in the reoperated cohorts.
RESULT(S): Total of 33 reoperation in the open cohort vs 17 in cMIS were identified. The reoperation rate was significantly higher in the open cohort at 39% (33/85) compared to 20% (17/85) in the cMIS cohort (P= 0.012). The reoperation rate in open cohort related to mechanical failure was 52% (17/33) compared to 35% (6/17) in cMIS cohort (P= 0.43). No significant difference was found in rates of specific etiologies contributing to complications in the cMIS vs open reoperation cohorts under uni- and multivariate analysis. The change in spinopelvic parameters among the two reoperation cohorts at 2YFU were statistically not significant (deltaCVA, deltaSVA, deltaPI-LL, deltaPT, deltaLL CA, deltaTL CA). Under univariate analysis, the following PROMS were similar: ODI, NRS Leg and Back Pain, EQ5D, EQ5D-VAS, SF-36 PCS,SF-36 MCS. However, SRS-22 in open cohort was significantly higher at 2YFU (3.55 +/- 0.73 open vs. 3,10 +/- 0.56 MIS, p = 0.029).
CONCLUSION(S): Findings in our ongoing study show that cMIS procedures were associated with a significantly lower reoperation rate compared to open surgical approaches. PROMS and the change in spinopelvic parameters were similar at 2YFU in both reoperated cohorts (except for SRS-22 favored open cohort). FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: Adult spinal deformity (ASD) patients maintain upright posture by compensating through their spine, pelvis and lower extremities. Little data exist quantifying the contribution of lower extremity compensation through the hips, knees, and ankles to maintain upright posture. PURPOSE: Evaluate the effect of the lower limb compensation by numerically unfolding patients. STUDY DESIGN/SETTING: Multicenter, prospective cohort. PATIENT SAMPLE: A total of 288 patients surgically treated for complex ASD with preoperative full body images. OUTCOME MEASURES: Horizontal distance between vertebra centroid and ankle.
METHOD(S): Surgical ASD patients were enrolled into a prospective study based on three criteria deformity severity (PI-LL>25degree, TPA>30degree, SVA>15cm, TCobb>70degree or TLCobb>50degree), procedure complexity (>12 levels fused, 3CO or ACR) and/or age (>65 and >7 levels fused). Preop full-body images were evaluated and age and PI-adjusted normative values were used to model spine alignment based upon three configurations: COMP (all lower extremity compensatory mechanisms maintained), PARTIAL (removal of ankle dorsiflexion and knee flexion, maintained hip extension), UNCOMP (ankle, knee, and hip compensation eliminated by reset PT to the age and PI norms). The three configurations were compared, and COMP alignment was stratified by TPA percentiles to investigate the offsets from each vertebra to the ankle joint acting as a surrogate of the gravity line in free-standing position.
RESULT(S): A total of 288 patients met inclusion criteria (60+/-15yo, 70.5% female, 27.4+/-5.9 BMI). COMP spine deformity magnitude included PI-LL 15+/-24, TPA 24+/-14, and SVA 65+/-69mm. As the model transitioned from COMP to UNCOMP alignment, the initial posterior translation of the pelvis decreased significantly to an anterior translation vs the ankle (P.Shift 30 to -7.6 mm). This was associated with a decrease in pelvic retroversion (PT 24.1 to 16.1), hip extension (SFA 203 to 200), knee flexion (KA 5.5 to -0.4), and ankle dorsiflexion (AA 5.3 to 3.7). As a result, the anterior malalignment of the trunk significantly increased SVA (65 to 120mm) and G-SVA (C7-Ankle from 36 to 127 mm), leading to a three-fold increase in bending moments sustained by the ankle joint. The stratification of the COMP position by TPA percentiles revealed that as the deformity increases, the vertebrae above T8 translate anteriorly, those below T10 move posteriorly, with the T8-T10 segment remaining ~3cm posterior to the ankle joint independently of the deformity severity.
CONCLUSION(S): Removal of lower limbs' compensation revealed an unsustainable truncal malalignment with a three-fold increase of bending moments at the ankle joints. Combined, lower limb compensations permit "reducing" the SVA by two-fold and the C7-ankle SVA by three-fold. From a mechanical point of view, this compensation permits maintaining the trunk center of mass (T9) at a fixed offset of ~3 cm from the ankle joint. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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