BACKGROUND:Changing from standing to sitting positions requires rotation of the femur from an almost vertical plane to the horizontal plane. Osteoarthritis of the hip limits hip extension, resulting in less ability to recruit spinopelvic tilt (SPT) while standing and requiring increased SPT while sitting to compensate for the loss of hip range of motion. To date, the effect of total hip arthroplasty (THA) on spinopelvic sitting and standing mechanics has not been reported, particularly in the setting of patients with coexistent sagittal plane spinal deformity. METHODS:A retrospective review was performed of patients ≥18 years of age undergoing unilateral THA for hip osteoarthritis with sitting and standing radiographs made before and after THA. Alignment was analyzed at baseline and follow-up after THA in both standing and sitting positions in a relaxed posture with the fingers resting on top of the clavicles. Patients were grouped according to the presence or absence of sagittal plane deformity preoperatively into 3 groups: no sagittal plane deformity (normal), thoracolumbar (TL) deformity (pelvic incidence-lumbar lordosis [PI-LL] mismatch > 10° and/or T1-pelvic angle [TPA] > 20°), or apparent deformity (PI-LL ≤ 10° and TPA ≤ 20°, but sagittal vertical axis [SVA] > 50 mm). RESULTS:In this study, 192 patients were assessed: 64 had TL deformity, 39 had apparent deformity, and 89 had normal alignment. Overall, patients demonstrated a reduction in standing SVA (45 to 34.1 mm; p < 0.001) and an increase in SPT (14.6° to 15.7°; p = 0.03) after THA. There was a greater change in standing SVA (p < 0.001) among patients with apparent deformity (-29.0 mm) compared with patients with normal alignment (0.9 mm) and patients with TL deformity (-16.3 mm). Those with apparent deformity also experienced the greatest difference (p = 0.03) in postural SPT change (moving from standing to sitting) (-10.1°) from before to after THA when compared with those with normal alignment (-3.6°) and TL deformity (-1.2°). The difference in postural SVA change from before to after THA was also greatest (p < 0.001) in those with apparent deformity (32.1 mm) compared with those with normal alignment (6.5 mm) and TL deformity (17.3 mm). CONCLUSIONS:Postural changes in spinopelvic alignment vary after THA depending on the presence of TL deformity or apparent deformity due to hip flexion contracture. Patients with apparent deformity had larger changes in standing and sitting alignment than patients with TL deformity or patients with normal alignment. The assessment of global sagittal alignment findings can be used to predict the likelihood of improvement in sagittal alignment after THA. LEVEL OF EVIDENCE:Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Clinical trials have studied the effects of curve magnitude and flexibility, age, and skeletal immaturity on the outcomes of VBT. No studies have assessed the effect of Lenke curve type on the outcomes of VBT. This study compares outcomes in patients who underwent VBT with Lenke type 1, 3, 5, and 6 curves. Single center retrospective review of patients undergoing mini-open thoracoscopic-assisted two row vertebral body tethering (2RVBT) for the correction of AIS with a minimum 2-year follow-up were included. Patients were grouped by Lenke type, which yielded 4 groups; types 1, 3, 5, or 6. Analysis included preoperative demographic parameters, as well as radiographic and clinical outcome measures. 156 2RVBT (Lenke 1, N = 61; Lenke 3, N = 35; Lenke 5, N = 37; Lenke 6, N = 23) patients met inclusion criteria. The mean preoperative apex Cobb angle in the Lenke type 1, 3, 5, and 6 groups were 50.2 ± 9.1, 50.5 ± 10.1, 45.0 ± 8.6, and 49.0 ± 10.8, respectively. This corrected to 21.2 ± 10.2, 19.2 ± 8.5, 13.6 ± 7.2, 18.5 ± 8.3 in Lenke type 1, 3, 5, and 6 groups, respectively, demonstrating that Lenke type 5 saw greatest correction following 2RVBT. With regards to revision recommendation following tether breakage, Lenke type 3 curves were most frequently indicated for fusion, whereas Lenke type 1 curves were most frequently not indicated for revision surgery. Lenke type 5 curves are the most amenable to correction via 2RVBT, as evident by their lower post-operative apex Cobb angles and lowest rate of recommendation for revision to posterior spinal fusion.

Study Design:Single-center retrospective cohort study.Objective:To compare the correction of fractional curve and L5 tilt in 2RVBT versus PSF with LIV in the lumbar spine.Summary of Background Data:Vertebral body tethering, an AIS fusion-alternative, avoids rigid constructs, allowing for lower instrumented vertebra (LIV) selection. Single-tether constructs break, but mini-open thoracoscopic assistant double-row vertebral body tethering (2RVBT) reduces this. Limited comparative studies exist with posterior spinal fusion (PSF).Methods:Retrospective analysis of AIS correction surgeries with lumbar LIV using preoperative and minimum 2-year postoperative imaging. Patients were divided into 2RVBT or PSF groups. Data included age, Riser, UIV, LIV, instrumented levels, and revision rates. Radiographic analyses included preoperative and postoperative main curve Cobb (MCC), secondary curve Cobb (SCC), fractional curve Cobb (FCC), and L5 tilt.Results:Ninety-nine patients participated (49 in 2RVBT, 50 in PSF). Preoperatively, secondary CC differed significantly (2RVBT: 44.6 +/- 10.4 degrees vs. PSF: 39.5 +/- 11.8 degrees, P=0.026), but not L5 tilt, MCC, or FCC. Postoperatively, MCC (2RVBT: 25.7 +/- 12.3 degrees vs. PSF: 19.5 +/- 7.4 degrees, P=0.003) and SCC (2RVBT: 18.0 +/- 8.4 degrees vs. PSF: 14.5 +/- 6.6 degrees, P=0.012) varied. Preoperative to postoperative changes in MCC (2RVBT: -32.0 +/- 11.3 degrees vs. PSF: -37.2 +/- 13.3 degrees, P=0.044) and L5 tilt (-13.8 +/- 9.0 degrees vs. PSF: -8.1 +/- 6.8 degrees, P=0.001) differed. Revision rates were similar (2RVBT: 2.0%, PSF: 4.0%, P=0.57). In 2RVBT, 3 tethers broke, 1 revision occurred for a broken tether, and 1 pleural effusion needed thoracocentesis. In PSF, 1 superficial infection needed surgery, and 1 revision was for add-on phenomenon. After PSM for Lenke classification, 54 patients remained (27 in each group). At 2 years, 2RVBT showed less MCC correction (-30.8 +/- 11.8 degrees vs. -38.9 +/- 11.9 degrees, P=0.017), but greater L5 tilt correction (-14.6 +/- 10.0 degrees vs. -7.5 +/- 6.0 degrees, P=0.003).Conclusions:This study with a minimum 2-year radiographic follow-up demonstrates that 2RVBT results in greater L5 tilt correction when compared with posterior spinal fusion after PSM for Lenke classification and similar rates of revision surgery.Level of Evidence:Level III.

Study Design: Retrospective cohort study. Objective: To develop parameter thresholds obtainable from cervical radiographs that correlate with concomitant thoracolumbar malalignment. Summary of Background Data: T1 slope (T1S) is typically discussed in the context of cervical deformity and correlated with health-related quality of life outcomes. Prior research suggests that T1S is related to global alignment; however, a definition for “high” T1S has not been established. Most patients undergoing cervical surgery do not undergo full-spine imaging; therefore, obtaining a parameter associated with thoracolumbar malalignment from cervical radiographs would be beneficial. Methods: A database of preoperative adult spinal deformity (ASD) patients was analyzed. Measures obtained from standing lateral radiographs included T1S, thoracic kyphosis (TK), sagittal vertical axis (SVA), T1-pelvic angle (TPA), pelvic tilt (PT), and pelvic incidence minus lumbar lordosis (PI-LL). Decision tree analysis was then used to determine the T1S corresponding to published thresholds for high TK (40 degrees), SVA (40 mm), TPA (25 degrees), and PT (25 degrees). Alignment between high and normal T1S patients was compared. Results: Two hundred twenty-six preoperative patients were included (mean: 58±16 y 62%F). Larger T1S was correlated with greater SVA (r=0.365), TPA (r=0.302), TK (r=0.606), and PT (r=0.230) (all P<0.001). Decision tree analysis yielded a threshold of 30 degrees for high T1S, which 50% of patients had. Compared with patients with T1S <30 degrees, those with T1S >30 degrees had higher TK (41.5 vs. 25.8 degrees), SVA (78.7 vs. 33.7 mm), TPA (27.6 vs. 18.3 degrees), and PT (26.3 vs. 20.8 degrees), and PI-LL (18.2 vs. 11.7 degrees) (all P<0.05). Seventy-nine percent of patients with high T1S had high TK (T1S <30=13%), 69% had high SVA (T1S <30=38%), 66% had high TPA (T1S <30=37%), 60% had PT >25 degrees (T1S <30=42%), and 47% had PI-LL >20 degrees (T1S <30=34%) (all P<0.05). Conclusion: Higher T1S was associated with worse global alignment. T1S was most strongly associated with TK. A T1S=30 degrees corresponded to high TK, SVA, TPA, and PT thresholds. Therefore, surgeons should consider obtaining full-spine radiographs if a T1S >30 degrees is present on cervical imaging.

Study Design Retrospective analysis. Objectives To evaluate resolution of radiculopathy in one-level lumbar fusion with indirect or direct decompression techniques. Methods Patients ≥18 years of age with preoperative radiculopathy undergoing single-level lumbar fusion with up to 2-year follow-up were grouped by indirect and direct decompression. Direct decompression (DD) group included ALIF and LLIF with posterior DD procedure as well as all TLIF. Indirect decompression (ID) group included ALIF and LLIF without posterior DD procedure. Propensity score matching was used to control for intergroup differences in age. Intergroup outcomes were compared using means comparison tests. Logistic regressions were used to correlate decompression type with symptom resolution over time. Significance set at P < .05. Results 116 patients were included: 58 direct decompression (DD) (mean 53.9y, 67.2% female) and 58 indirect decompression (ID) (mean 54.6y, 61.4% female). DD patients experienced greater blood loss than ID. Additionally, DD patients were 4.7 times more likely than ID patients to experience full resolution of radiculopathy at 3 months post-op. By 6 months, DD patients demonstrated larger reductions in VAS score. With regard to motor function, DD patients had improved motor score associated with the L5 dermatome at 6 months relative to ID patients. Conclusions Direct decompression was associated with greater resolution of radiculopathy in the near post-operative term, with no differences at long term follow-up when compared with indirect decompression. In particularly debilitated patients, these findings may influence surgeons to perform a direct decompression to achieve more rapid resolution of radiculopathy symptoms.

OBJECTIVE The present study utilized recently developed in -construct measurements in simulations of cervical deformity surgery in order to assess undercorrection and predict distal junctional kyphosis (DJK). METHODS A retrospective review of a database of operative cervical deformity patients was analyzed for severe DJK and mild DJK. C2-lower instrumented vertebra (LIV) sagittal angle (SA) was measured postoperatively, and the correction was simulated in the preoperative radiograph in order to match the C2-LIV by using the planning software. Linear regression analysis that used C2 pelvic angle (CPA) and pelvic tilt (PT) determined the simulated PT that matched the virtual CPA. Linear regression analysis was used to determine the C2-T1 SA, C2-T4 SA, and C2-T10 SA that corresponded to DJK of 20 degrees and cervical sagittal vertical axis (cSVA) of 40 mm. RESULTS Sixty-nine cervical deformity patients were included. Severe and mild DJK occurred in 11 (16%) and 22 (32%) patients, respectively; 3 (4%) required DJK revision. Simulated corrections demonstrated that severe and mild DJK patients had worse alignment compared to non-DJK patients in terms of cSVA (42.5 mm vs 33.0 mm vs 23.4 mm, p < 0.001) and C2-LIV SVA (68.9 mm vs 57.3 mm vs 36.8 mm, p < 0.001). Linear regression revealed the relationships between in -construct measures (C2-T1 SA, C2-T4 SA, and C2-T10 SA), cSVA, and change in DJK (all R > 0.57, p < 0.001). A cSVA of 40 mm corresponded to C2-T4 SA of 10.4 degrees and C2-T10 SA of 28.0 degrees. A DJK angle change of 10 degrees corresponded to C2-T4 SA of 5.8 degrees and C2-T10 SA of 20.1 degrees. CONCLUSIONS Simulated cervical deformity corrections demonstrated that severe DJK patients have insufficient corrections compared to patients without DJK. In -construct measures assess sagittal alignment within the fusion separate from DJK and subjacent compensation. They can be useful as intraoperative tools to gauge the adequacy of cervical deformity correction.

BACKGROUND CONTEXT Correction of cervical deformity (CD) has the potential to improve patient function significantly. However, previously described radiographic parameters cannot be measured intraoperatively. The present study investigates in-construct measurements which can be used as targets for CD correction to optimize radiographic realignment and improve outcomes. PURPOSE Provide targets for CD correction through in-construct measurements (SA) to optimize radiographic realignment and improve outcomes. STUDY DESIGN/SETTING Retrospective analysis of a prospective, multicenter CD database. PATIENT SAMPLE Patients with adult cervical deformity with either cervical kyphosis more than 10°, cSVA of more than 4 cm, CBVA more than 25°, and 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 postoperatively. OUTCOME MEASURES Demographic factors; surgical factors; radiographic measures including novel in-construct measures describing sagittal alignment within the fusion with a line from the C2 centroid to the the centroid of a thoracic vertebra and a line along the posterior cortex of that vertebra (C2-T1 SA, C2-T4 SA, C2-T10 SA, C2-LIV SA) and established parameters (cSVA, T1S, C2S, TS-CL, T4-T12 Cobb, TPA, SVA, PI-LL, PT, DJK angle. 1-year HRQLs: NDI, mJOA, NRS neck, EQ5D. METHODS The in-construct measurements were used depending on the 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 sagittal correction within the fusion for each patient. Analyses between failed and success realigned groups were performed using t-test, chi square analysis, and multivariate regression. Linear regression analysis was used to determine the C2-T1, C2-T4, C2-10 SA measures that correspond to a cSVA=4 cm and DJK =10°. HRQL analysis was done in subset of patients with 1-year follow-up. RESULTS A total of 143 patients with CD (mean age 63 yr, 60% female) were included with 73 having failed radiographic outcomes by high cSVA (51% Failed). There were no differences in demographics. Failed was associated with greater levels fused (10.44 vs 8.46; p=0.005) and EBL (1108.41 vs 651.69; p=0.002). Failure to correct cSVA was associated with worse baseline deformity including cSVA (64.37 mm vs 40.36), T1S (42.97° vs 32.25°) C2S (51.38° vs 34.40°) TS-CL (51.16° vs 35.78°) (all p<0.001), greater kyphotic change in DJKA (10.45° vs 6.33°; p= 0.026), and greater postoperative C2-T1 SA (-5.23° vs -12.84°; p<0.001). Multivariate regression for variables with p<0.05 revealed that the postoperative C2-T1 in-construct angle independently predicted failed realignment outcome (OR= 1.25, CI 1.11-1.41; p<0.001). Using linear regression, a cSVA measurement of 4.0cm corresponded to a C2-T1-SA of -9.55°, C2-T4 of -0.37°, C2-T10-SA of 14.67°(all r>0.38, p<0.05). Linear regression revealed that postoperative C2-T10 SA was able to predict change in DJKA, where a change of 10° yielded a C2-T10 SA of 20.67°(r>0.57, p=0.02). While there was no difference in postop HRQL between the groups, improvement in C2-LIV SA was associated with improvement in neck pain (NRS neck) at 1 year (r>0.42, p=0.036). CONCLUSIONS Failure to restore cSVA patients was independently associated with undercorrection, as evidenced by significantly larger postoperative in-construct angles. In-construct measures can be used as alignment targets to optimize radiographic outcomes and prevent DJK thereby improving patient reported outcomes. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs.

OBJECTIVE:The aim of this study was to determine if spinal deformity patients with L5 sacralization should have pelvic incidence (PI) and other spinopelvic parameters measured from the L5 or S1 endplate. METHODS:This study was a multicenter retrospective comparative cohort study comprising a large database of adult spinal deformity (ASD) patients and a database of asymptomatic individuals. Linear regression modeling was used to determine normative T1 pelvic angle (TPA) and PI - lumbar lordosis (LL) mismatch (PI-LL) based on PI and age in a database of asymptomatic subjects. In an ASD database, patients with radiographic evidence of L5 sacralization had the PI, LL, and TPA measured from the superior endplate of S1 and then also from L5. The differences in TPA and PI-LL from normative were calculated in the sacralization cohort relative to L5 and S1 and correlated to the Oswestry Disability Index (ODI). Patients were grouped based on the Scoliosis Research Society (SRS)-Schwab PI-LL modifier (0, +, or ++) using the L5 PI-LL and S1 PI-LL. Baseline ODI and SF-36 Physical Component Summary (PCS) scores were compared across and within groups. RESULTS:Among 1179 ASD patients, 276 (23.4%) had transitional anatomy, 176 with sacralized L5 (14.9%) and 100 (8.48%) with lumbarization of S1. The 176 patients with sacralized L5 were analyzed. When measured using the L5 superior endplate, pelvic parameters were significantly smaller than those measured relative to S1 (PI: 24.5° ± 11.0° vs 55.7° ± 12.0°, p = 0.001;TPA: 11.2° ± 12.0° vs 20.3° ± 12.5°, p = 0.001; and PI-LL: 0.67° ± 21.1° vs 11.4° ± 20.8°, p = 0.001). When measured from S1, 76 (43%), 45 (25.6%), and 55 (31.3%) patients had SRS-Schwab PI-LL modifiers of 0, +, and ++, respectively, compared with 124 (70.5%), 22 (12.5%), and 30 (17.0%), respectively, when measured from L5. There were significant differences in ODI and PCS scores as the SRS-Schwab grade increased regardless of L5 or S1 measurement. The L5 group had lower PCS functional scores for SRS-Schwab modifiers 0 and ++ relative to same grades in the S1 group. Offset from normative TPA (0.5° ± 11.1° vs 9.6° ± 10.8°, p = 0.001) and PI-LL (4.5° ± 20.4° vs 15.2° ± 19.3°, p = 0.001) were smaller when measuring from L5. Moreover, S1 measurements were more correlated with health status by ODI (TPA offset from normative: S1, R = 0.326 vs L5, R = 0.285; PI-LL offset from normative: S1, R = 0.318 vs L5, R = 0.274). CONCLUSIONS:Measuring the PI and spinopelvic parameters at L5 in sacralized anatomy results in underestimating spinal deformity and is less correlated with health-related quality of life. Surgeons may consider measuring PI and spinopelvic parameters relative to S1 rather than at L5 in patients with a sacralized L5.

Study Design. Retrospective review of an adult deformity database. Objective. To identify pelvic incidence (PI) and age-appropriate physical function alignment targets using a component angle of T1-pelvic angle within the fusion to define correction and their relationship to proximal junctional kyphosis (PJK) and clinical outcomes. Summary of Background Data. In preoperative planning, a patient’s PI is often utilized to determine the alignment target. In a trend toward more patient-specific planning, age-specific alignment has been shown to reduce the risk of mechanical failures. PI and age have not been analyzed with respect to defining a functional alignment. Methods. A database of patients with operative adult spinal deformity was analyzed. Patients fused to the pelvis and upper-instrumented vertebrae above T11 were included. Alignment within the fusion correlated with clinical outcomes and PI. Short form 36-Physical Component Score (SF36-PCS) normative data and PI were used to compute functional alignment for each patient. Overcorrected, under-corrected, and functionally corrected groups were determined using T10-pelvic angle (T10PA). Results. In all, 1052 patients met the inclusion criteria. T10PA correlated with SF36-PCS and PI (R=0.601). At six weeks, 40.7% were functionally corrected, 39.4% were overcorrected, and 20.9% were under-corrected. The PJK incidence rate was 13.6%. Overcorrected patients had the highest PJK rate (18.1%) compared with functionally (11.3%) and under-corrected (9.5%) patients ( P <0.05). Overcorrected patients had a trend toward more PJK revisions. All groups improved in HRQL; however, under-corrected patients had the worst 1-year SF36-PCS offset relative to normative patients of equivalent age (−8.1) versus functional (−6.1) and overcorrected (−4.5), P <0.05. Conclusions. T10PA was used to determine functional alignment, an alignment based on PI and age-appropriate physical function. Correcting patients to functional alignment produced improvements in clinical outcomes, with the lowest rates of PJK. This patient-specific approach to spinal alignment provides adult spinal deformity correction targets that can be used intraoperatively.

BACKGROUND CONTEXT Foraminal stenosis with accompanying radicular symptoms is a common cause of leg pain in older adults. Operative treatment of radiculopathy can involve either direct decompression via laminectomy or foraminotomy or indirect decompression with lumbar interbody fusion. We sought to evaluate the anatomic effects of each of these techniques on foraminal dimensions using computer tomography imaging. PURPOSE To determine if use of an interbody device in conjunction with fusion will confer greater improvement in foraminal dimensions compared to those who undergo laminectomy alone. STUDY DESIGN/SETTING Retrospective comparative cohort review at a large academic institution. PATIENT SAMPLE We evaluated patients over 18 years of age that underwent primary 1-3 level uninstrumented laminectomy and 1-2 level ALIF or TLIF with both preoperative and postoperative CT scans within 1-year of the surgery. There were a total of 64 patients, with a total of 76 operative levels and 152 vertebral foramina. Fourteen patients had undergone laminectomy alone, and 50 patients underwent lumbar interbody fusion (ALIF:26;TLIF:24). OUTCOME MEASURES Computer tomography radiographic dimensions of foramina stenosis. METHODS Measurements of foramen were conducted bilaterally at the operative level in the sagittal plane. Foraminal height, width and total area were measured at the cut with the most foraminal stenosis present. Hemilaminectomies were excluded. Independent-samples T-test and Pearson Chi-square analysis were performed for the cohort; significant set at p<0.05. RESULTS There were a total of 64 patients, with a total of 76 operative levels and 152 vertebral foramina. Fourteen patients had undergone laminectomy alone, and 50 patients underwent lumbar interbody fusion (ALIF:26;TLIF:24). Age was observed to be higher in patients that underwent laminectomy versus TLIF and ALIF (66.0±8.0 years vs 60.4±12.8 years and 55.8±12.2 years, respectively, p=0.02). Other demographic differences were similar between cohorts (p>0.05). Preoperative foraminal width, height, and area were similar between cohorts (p>0.05); however, postoperative foraminal heights were different among groups. Both TLIF and ALIF had greater percent increases in foraminal height (48% and 41%) and area (65% and 55%) compared to laminectomy (height: 8.7%, area: 6.1%, p=0.001). CONCLUSIONS Patients that underwent laminectomy had similar improvement in foraminal width, but significantly lower increases in foraminal height and area compared to those that underwent anterior or transforaminal interbody fusions. This supports the idea that laminectomies alone are insufficient for the treatment of isolated foraminal stenosis. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs. Foraminal stenosis with accompanying radicular symptoms is a common cause of leg pain in older adults. Operative treatment of radiculopathy can involve either direct decompression via laminectomy or foraminotomy or indirect decompression with lumbar interbody fusion. We sought to evaluate the anatomic effects of each of these techniques on foraminal dimensions using computer tomography imaging. To determine if use of an interbody device in conjunction with fusion will confer greater improvement in foraminal dimensions compared to those who undergo laminectomy alone. Retrospective comparative cohort review at a large academic institution. We evaluated patients over 18 years of age that underwent primary 1-3 level uninstrumented laminectomy and 1-2 level ALIF or TLIF with both preoperative and postoperative CT scans within 1-year of the surgery. There were a total of 64 patients, with a total of 76 operative levels and 152 vertebral foramina. Fourteen patients had undergone laminectomy alone, and 50 patients underwent lumbar interbody fusion (ALIF:26;TLIF:24). Computer tomography radiographic dimensions of foramina stenosis. Measurements of foramen were conducted bilaterally at the operative level in the sagittal plane. Foraminal height, width and total area were measured at the cut with the most foraminal stenosis present. Hemilaminectomies were excluded. Independent-samples T-test and Pearson Chi-square analysis were performed for the cohort; significant set at p<0.05. There were a total of 64 patients, with a total of 76 operative levels and 152 vertebral foramina. Fourteen patients had undergone laminectomy alone, and 50 patients underwent lumbar interbody fusion (ALIF:26;TLIF:24). Age was observed to be higher in patients that underwent laminectomy versus TLIF and ALIF (66.0±8.0 years vs 60.4±12.8 years and 55.8±12.2 years, respectively, p=0.02). Other demographic differences were similar between cohorts (p>0.05). Preoperative foraminal width, height, and area were similar between cohorts (p>0.05); however, postoperative foraminal heights were different among groups. Both TLIF and ALIF had greater percent increases in foraminal height (48% and 41%) and area (65% and 55%) compared to laminectomy (height: 8.7%, area: 6.1%, p=0.001). Patients that underwent laminectomy had similar improvement in foraminal width, but significantly lower increases in foraminal height and area compared to those that underwent anterior or transforaminal interbody fusions. This supports the idea that laminectomies alone are insufficient for the treatment of isolated foraminal stenosis.

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: 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.

OBJECTIVE:The objective of this study was to explore the rate of proximal junctional failure (PJF) and functional outcomes of normative alignment goals compared with alignment targets based on age-appropriate physical function.METHODS:Baseline relationships between age, pelvic incidence (PI), and a component of the T1 pelvic angle (TPA) within the fusion were analyzed in adult spinal deformity (ASD) patients and compared with those of asymptomatic patients. Linear regression modeling was used to determine alignment based on PI and age in asymptomatic patients (normative alignment), and in ASD patients, alignment corresponding to age-appropriate functional status (functional alignment). A cohort of 288 ASD patients was split into two groups based on whether the patient was closer to their normative or functional alignment goal at their 6-week postoperative radiographic follow-up. The rates of proximal junctional kyphosis (PJK) and PJF were determined for each cohort.RESULTS:In the 288 ASD patients included in this pre- to postoperative analysis, there was no difference in baseline alignment or health-related quality of life (HRQOL) between the normative alignment and functional alignment groups. At 6 weeks, patients with normative alignment had a smaller TPA (4.45° vs 14.1°) and PI minus lumbar lordosis (-7.24° vs 7.4°) (both p < 0.0001) and higher PJK (40% vs 27.2%, p = 0.03) and PJF (17% vs 6.8%, p = 0.008) rates than patients with functional alignment.CONCLUSIONS:Correction in ASD patients to normative alignment resulted in higher rates of PJK and PJF without improvements in HRQOL. Correction in ASD patients to functional alignment that mirrors the physical function of their age-matched asymptomatic peers is recommended.

Background The number of elderly patients undergoing adult spinal deformity (ASD) surgery has increased with the advent of new techniques and more nuanced understanding of global malalignment as patients age. The relationship between inpatient physical activity after ASD surgery and postoperative complications in elderly patients has not been reported; thus, we sought to investigate this relationship. Methods We performed a medical record review of 185 ASD patients older than 65 years (age: 71.5 ± 4.7; body mass index: 30.0 ± 6.1, American Society of Anesthesiologists: 2.7 ± 0.5, and levels fused: 10.5 ± 3.4). We derived the number of feet walked over the first 3 days after surgery from physical therapy documentation and evaluated for association with 90-day perioperative complications. Patients who sustained an incidental durotomy were excluded from the study. Results The 185 patients were divided into groups based on whether they were among the 50th percentile for number of feet walked (62 ft). Walking less than 62 ft after ASD surgery was associated with higher incidence of postoperative complications (54.3%, P = 0.05), cardiac complications (34.8%, P = 0.03), pulmonary complications (21.7%, P = 0.01), and ileus (15.2%, P = 0.03). Patients who developed any postoperative complication (106 ± 172 vs 211 ± 279 ft, P = 0.001), ileus (26 ± 49 vs 174 ± 248 ft, P = 0.001), deep venous thrombosis (23 ± 30 vs 171 ± 247 ft, P = 0.001), and cardiac complications (58 ± 94 vs 192 ± 261 ft) walked less than patients who did not. Conclusion Elderly patients who walked less than 62 ft in the first 3 days after ASD surgery have a higher rate of postoperative complications, specifically pulmonary and ileus compared with those patients who walked more. Steps walked after ASD surgery may be a helpful and practical addition to the surgeon’s armamentarium for monitoring the recovery of their patients. Clinical Relevence Monitoring the steps walked by patients after ASD surgery can be a practical and useful tool for surgeons to track and improve their patients’ recovery. Level of Evidence 3.

BACKGROUND CONTEXT There is mounting evidence to suggest that osteoporosis and poor bone quality increase the risk not only of fragility fractures, but also of postoperative complications in patients undergoing spinal fusion. The current standard of care to assess bone quality, dual-energy X-ray absorptiometry (DXA) estimation of bone mineral density (BMD), has limitations. It is not valid in the thoracic spine, in the setting of scoliosis, in patients with osteophytes, or in patients with very high or low body mass index. CT measurement of Hounsfield units (HU) has also been used to assess bone quality in the spine and in some studies has been associated with mechanical failures. However, both BMD and HU assess only bone density, which contributes only partially to bone strength. PURPOSE Finite element analysis (FEA), a mechanical engineering method that can be used to estimate bone strength, has not been widely investigated as a tool to investigate bone quality in spinal fusion patients. The goal of this study was to assess the value of bone modulus, computed from finite element analysis (FEA) applied to patients' computed tomography (CT) scans, for prediction of postoperative complications in lumbar spine fusion patients. We also assessed the ability of BMD and HU, both computed from CT, for prediction of postoperative complications. STUDY DESIGN/SETTING This was an institutional review board-approved, retrospective study of consecutive lumbar spine fusion patients with 2- year follow-up from a single academic medical center in 2017. PATIENT SAMPLE There were a total of 85 subjects. We classified patients into two cohorts, those who did not (n = 54, 37 females, 17 males, mean age = 66.4±6.9 years, mean body mass index [BMI] = 29.4±5.4 kg/m2) and did (n = 31, 17 females, 14 males, mean age = 69.5±8.2 years, mean BMI = 28.4±5.7 kg/m2) suffer a bone-quality related complication within two years following the surgery, which was defined as: proximal junctional kyphosis (PJK) or failure (PJF) (n = 5), pedicle screw loosening (n = 14), adjacent segment disease (n = 20), or pseudarthrosis (n = 6). There was no significant difference between groups in terms of age or body mass index. OUTCOME MEASURES The outcome measures were bone modulus, BMD, and HU. METHODS Using patients' preoperative CT scans, we applied in-house developed software to compute HU, BMD, and bone modulus, the latter via FEA. We used the student's t-test to assess differences between groups in terms of theses outcome measures. We also performed univariate and multivariate ROC analyses to assess the ability of these preoperative measures to predict postoperative complications. RESULTS Compared to controls who did not suffer a postoperative complication, patients with complications demonstrated significantly lower bone modulus (-15.7% to -23.2%) at every vertebral level from L1 to L5 (p ≤ 0.02 for all). Patients with bone quality related complications demonstrated lower HU and BMD (-1.1% to -8.5%) from L1 to L5, but the differences were not statistically significant (p values ranging from 0.18 to 0.92). Bone modulus measured at any level from L1 to L5 level was able to predict postoperative bone quality related complication better than chance (AUC = 0.666 to 0.695, p 0.1). The combination of bone modulus, BMD, age, gender, and BMI resulted in higher AUC values compared to bone modulus alone (AUC = 0.737 to 0.809, p < 0.001 for all). CONCLUSIONS Preoperative bone modulus has utility, beyond that of BMD or HU, for prediction of postoperative complications in spinal fusion patients. Inclusion of patient-specific clinical/demographic factors also appears to further improve the ability to predict postoperative complications. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs. There is mounting evidence to suggest that osteoporosis and poor bone quality increase the risk not only of fragility fractures, but also of postoperative complications in patients undergoing spinal fusion. The current standard of care to assess bone quality, dual-energy X-ray absorptiometry (DXA) estimation of bone mineral density (BMD), has limitations. It is not valid in the thoracic spine, in the setting of scoliosis, in patients with osteophytes, or in patients with very high or low body mass index. CT measurement of Hounsfield units (HU) has also been used to assess bone quality in the spine and in some studies has been associated with mechanical failures. However, both BMD and HU assess only bone density, which contributes only partially to bone strength. Finite element analysis (FEA), a mechanical engineering method that can be used to estimate bone strength, has not been widely investigated as a tool to investigate bone quality in spinal fusion patients. The goal of this study was to assess the value of bone modulus, computed from finite element analysis (FEA) applied to patients' computed tomography (CT) scans, for prediction of postoperative complications in lumbar spine fusion patients. We also assessed the ability of BMD and HU, both computed from CT, for prediction of postoperative complications. This was an institutional review board-approved, retrospective study of consecutive lumbar spine fusion patients with 2- year follow-up from a single academic medical center in 2017. There were a total of 85 subjects. We classified patients into two cohorts, those who did not (n = 54, 37 females, 17 males, mean age = 66.4±6.9 years, mean body mass index [BMI] = 29.4±5.4 kg/m2) and did (n = 31, 17 females, 14 males, mean age = 69.5±8.2 years, mean BMI = 28.4±5.7 kg/m2) suffer a bone-quality related complication within two years following the surgery, which was defined as: proximal junctional kyphosis (PJK) or failure (PJF) (n = 5), pedicle screw loosening (n = 14), adjacent segment disease (n = 20), or pseudarthrosis (n = 6). There was no significant difference between groups in terms of age or body mass index. The outcome measures were bone modulus, BMD, and HU. Using patients' preoperative CT scans, we applied in-house developed software to compute HU, BMD, and bone modulus, the latter via FEA. We used the student's t-test to assess differences between groups in terms of theses outcome measures. We also performed univariate and multivariate ROC analyses to assess the ability of these preoperative measures to predict postoperative complications. Compared to controls who did not suffer a postoperative complication, patients with complications demonstrated significantly lower bone modulus (-15.7% to -23.2%) at every vertebral level from L1 to L5 (p ≤ 0.02 for all). Patients with bone quality related complications demonstrated lower HU and BMD (-1.1% to -8.5%) from L1 to L5, but the differences were not statistically significant (p values ranging from 0.18 to 0.92). Bone modulus measured at any level from L1 to L5 level was able to predict postoperative bone quality related complication better than chance (AUC = 0.666 to 0.695, p 0.1). The combination of bone modulus, BMD, age, gender, and BMI resulted in higher AUC values compared to bone modulus alone (AUC = 0.737 to 0.809, p < 0.001 for all). Preoperative bone modulus has utility, beyond that of BMD or HU, for prediction of postoperative complications in spinal fusion patients. Inclusion of patient-specific clinical/demographic factors also appears to further improve the ability to predict postoperative complications.

BACKGROUND CONTEXT There are two ways to approach the spine using vertebral body tethering in adolescent idiopathic scoliosis correction surgery, mini open thoracoscopic assisted and thoracoscopic vertebral body tethering (VBT). This study focuses on preoperative and 2-year followup pulmonary function tests for mini open thoracoscopic assisted vertebral body tethering surgical cases. Currently there is evidence that pulmonary function does not decrease in a thoracoscopic approach, but it is unclear how pulmonary function is affected by a mini open thoracoscopic assisted approach to VBT surgery. PURPOSE To provide evidence that mini-open thoracoscopic assisted vertebral body tethering maintains pulmonary function at 2-year followup. STUDY DESIGN/SETTING Retrospective review at a single institution. PATIENT SAMPLE A total of 114 patients who underwent mini open thoracoscopic assisted vertebral body tethering surgery with 2-year followup were included in this study. OUTCOME MEASURES Primary outcomes included forced vital capacity (FVC), forced expiratory volume during the first second (FEV1), forced expiratory flow during the middle half of the FVC (FEF25-75%), peak expiratory flow (PEF), forced expiratory time (FET200%), forced inspiratory vital capacity (FIVC), total lung capacity (TLC), vital capacity (VC), and respiratory volume (RV). METHODS A retrospective review of patients who underwent mini open thoracoscopic assisted VBT surgery. Preoperative and 2-year follow up pulmonary function tests were performed in order to assess the pulmonary risks of VBT. T tests were used to determine significant differences in pulmonary function preoperatively and two years post surgery. RESULTS Pulmonary outcomes analysis revealed there were no significant decrease from preoperative to postoperative pulmonary function: FVC predicted (3.51 vs 3.53, p=0.92), FVC Pre (3.01 vs 3.02, p=0.933), FEV1 Predicted (3.11 vs 3.27, p=0.349), FEV1 Pre (2.55 vs 2.48, p=0.667), FEV1/FVC Predicted (88.34 vs 88.88, p=0.604), FEV1/FVC Pre (77.32 vs 84.89, p=0.148), FEF25-75 Predicted (3.64 vs 3.81, p=0.494), FEF25-75 Pre (2.57 vs 2.59, p=0.919), ISOFEF25-75% Pre (2.65 vs 2.79, p=0.822), FEF75-85% Pre (1.41 vs 1.36, p=0.93), PEF Predicted (6.21 vs 6.79, p-0.145), PEF Pre (5.42 vs 5.24, p-0.737), FET100% Pre (6.13 vs 6.23, p=0.915), FIVC Predicted (3.3 vs 3.32, p=0.963), FIVC Pre (2.72 vs 2.2, p=0.073), TLC (4.29 vs 5.56, p-0.233), VC (3.93 vs 3.19, p-0.781), RV (0.76 vs 1.31, p-0.258). CONCLUSIONS Mini open thoracoscopic assisted VBT maintains pulmonary function outcomes from baseline to 2-year followup. This can be another approach option for vertebral body tethering surgery. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs. There are two ways to approach the spine using vertebral body tethering in adolescent idiopathic scoliosis correction surgery, mini open thoracoscopic assisted and thoracoscopic vertebral body tethering (VBT). This study focuses on preoperative and 2-year followup pulmonary function tests for mini open thoracoscopic assisted vertebral body tethering surgical cases. Currently there is evidence that pulmonary function does not decrease in a thoracoscopic approach, but it is unclear how pulmonary function is affected by a mini open thoracoscopic assisted approach to VBT surgery. To provide evidence that mini-open thoracoscopic assisted vertebral body tethering maintains pulmonary function at 2-year followup. Retrospective review at a single institution. A total of 114 patients who underwent mini open thoracoscopic assisted vertebral body tethering surgery with 2-year followup were included in this study. Primary outcomes included forced vital capacity (FVC), forced expiratory volume during the first second (FEV1), forced expiratory flow during the middle half of the FVC (FEF25-75%), peak expiratory flow (PEF), forced expiratory time (FET200%), forced inspiratory vital capacity (FIVC), total lung capacity (TLC), vital capacity (VC), and respiratory volume (RV). A retrospective review of patients who underwent mini open thoracoscopic assisted VBT surgery. Preoperative and 2-year follow up pulmonary function tests were performed in order to assess the pulmonary risks of VBT. T tests were used to determine significant differences in pulmonary function preoperatively and two years post surgery. Pulmonary outcomes analysis revealed there were no significant decrease from preoperative to postoperative pulmonary function: FVC predicted (3.51 vs 3.53, p=0.92), FVC Pre (3.01 vs 3.02, p=0.933), FEV1 Predicted (3.11 vs 3.27, p=0.349), FEV1 Pre (2.55 vs 2.48, p=0.667), FEV1/FVC Predicted (88.34 vs 88.88, p=0.604), FEV1/FVC Pre (77.32 vs 84.89, p=0.148), FEF25-75 Predicted (3.64 vs 3.81, p=0.494), FEF25-75 Pre (2.57 vs 2.59, p=0.919), ISOFEF25-75% Pre (2.65 vs 2.79, p=0.822), FEF75-85% Pre (1.41 vs 1.36, p=0.93), PEF Predicted (6.21 vs 6.79, p-0.145), PEF Pre (5.42 vs 5.24, p-0.737), FET100% Pre (6.13 vs 6.23, p=0.915), FIVC Predicted (3.3 vs 3.32, p=0.963), FIVC Pre (2.72 vs 2.2, p=0.073), TLC (4.29 vs 5.56, p-0.233), VC (3.93 vs 3.19, p-0.781), RV (0.76 vs 1.31, p-0.258). Mini open thoracoscopic assisted VBT maintains pulmonary function outcomes from baseline to 2-year followup. This can be another approach option for vertebral body tethering surgery.

BACKGROUND CONTEXT The ACS-NSQIP and SpineSage are both easy to use and readily available online perioperative risk calculators The ACS-NSQIP calculator predicts perioperative complications after surgery, but lacks more spine-specific predictors. The SpineSage platform was developed as a tool built for predicting complications in spine surgery. While a limited number of studies have shown it be predictive of both overall and major medical complications in spine surgery, large external validation studies are limited and none have directly compared NSQIP against SpineSage in the same cohort of spine surgery patients. PURPOSE Assess the ACS-NSQIP Risk Calculator and SpineSage informatics platform for prediction of perioperative complications in spine surgery STUDY DESIGN/SETTING Retrospective. PATIENT SAMPLE A total of 440 patients undergoing thoracolumbar spine with or without fusion. OUTCOME MEASURES Any complication, serious complication, pneumonia, cardiac, dural tear, SSI, UTI, VTE, reoperation, death and LOS METHODS Each patient was entered into the ACS-NSQIP and SpineSage calculators and predicted risk for specific complications were directly compared to actual risks. Paired t-tests compared the differences between calculators and their predictability of complications. Patients were ranked based on risk predicted for each complication and the highest tertile for each was isolated. Multivariate regression controlling for age and gender was used to determine if the highest tertile for each risk calculator had predictability in complications following spine surgery. RESULTS Mean LOS 4.2+3 days, EBL 444+300 mL, operative time 256+240 min, and levels instrumented 2.1+2.3. When assessing the four complications predicted by SpineSage there were significant differences in three of the four variables, as SpineSage underpredicted the risk of all and serious-complications (p.5). Both calculator tertiles were trending towards significance for major medical complications (SpineSage: OR: 2.0, [0.94-4.23], p=.073; ACS-NSQIP: OR: 1.8,[0.96-3.48],p=.067). When examining any medical risk, only ACS NSQIP had significant predictability for any medical complication (OR: 2.1, [1.3-3.3]; p=.003). CONCLUSIONS Similar to previous studies, the ACS-NSQIP score underpredicted most complications, with the exception of LOS and death. In contrast to previous studies, our data suggest SpineSage was not predictive of actual rates of complications. As both calculators are highly accessible and provide at least some objective perioperative risk data points, we recommend them as a guiding tool but not as an absolute endpoint for clinical decision making as they may be inaccurate and insensitive. Further, higher powered studies elucidating the findings in this study should be conducted. Additionally, the assessment of these calculators for a specific subset of patients, such as deformity, degenerative or pediatrics, can further help guide clinicians regarding the utility of these calculators for their particular patient populations. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT L5 nerve root palsy is a complication that can occur after ALIF indirect decompression. It is thought to occur due to the dimensional change in the L5 foramen that can either compress or cause a stretch neuropraxia of the nerve root. While this complication has been observed, reports and studies highlighting its incidence and risk are lacking. PURPOSE To determine whether ALIF leads to an increased risk in L5 palsy, we sought to compare the relative risk compared to TLIF. We hypothesize that since foraminotomy is part of the TLIF procedure, it should demonstrate a difference in nerve root palsy compared to ALIF indirect decompression. STUDY DESIGN/SETTING A single institution retrospective cohort study. PATIENT SAMPLE A total of 626 patients (262 ALIF, 179 open TLIF, 185 MIS TLIF). The study period was 2017 to 2021. OUTCOME MEASURES Primary outcomes were postoperative leg pain, sensory deficits, and motor weakness in tibialis anterior (TA), extensor hallucis longus (EHL) and gastrocnemius (GC). Secondary outcomes were infection, return to operating room (OR), and return to emergency center (EC) within 90 days. METHODS Retrospective comparative cohort study comparing ALIF vs TLIF. Inclusion criteria were all patients who underwent L5-S1 ALIF or L5-S1 TLIF (both open and MIS). Multilevel surgeries were excluded. The rate of postop nerve palsy was compared for the two treatment approaches. Chi-square was performed for all categorical comparisons and ANOVA was performed for continuous statistical comparisons. RESULTS There were subtle differences in baseline characteristics between groups. ALIF patients were younger (p = 0.016), had less BMI (p = 0.026) and less likely to smoke (p = 0.008). There were no differences in gender or diabetes status. Patients undergoing TLIF (open and MIS) were more likely to be operated for lumbar spinal stenosis and radiculopathy (p < 0.001). There was an overall 3% rate of neuro deficits in the study population with a higher rate in those undergoing ALIF (5.3%) compared with open TLIF (0.6%) and MIS TLIF (2.2%) (p = 0.011). There was a rate of 3.1% EHL palsy in the ALIF group which was higher than TLIF (both open and MIS) (p = 0.048). There was a trend towards higher TA and GC nerve deficits in the ALIF group, but the difference was not significant. Additionally, there was a trend towards higher rates of return to OR for nerve deficit in the ALIF group, but this was not significant. However, ALIF patients had higher return to OR in 90 days for any reason (p = 0.01). There were no further differences between the groups. Among the 14 ALIF patients with any nerve deficit, 7 followed up at 3 mos and 5 in 1 year. At 3 mos, 5 of 7 patients had improvement in their nerve deficit and at 1 year, 5 of 5 patients had improved their deficiency. CONCLUSIONS This study demonstrates a higher rate of L5 nerve root palsy with ALIF compared to TLIF as evidenced by higher rates of EHL palsy with a rate of 3.1% in our study population. The study, however, is limited by its retrospective nature and subtle differences noted in demographics. Despite these differences, ALIF patient characteristics tended to be more favorable, which are unlikely to confound results of higher postoperative nerve deficits. Further study will be required to understand the mechanisms and radiological risk factors for postoperative L5 palsy after ALIF. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. L5 nerve root palsy is a complication that can occur after ALIF indirect decompression. It is thought to occur due to the dimensional change in the L5 foramen that can either compress or cause a stretch neuropraxia of the nerve root. While this complication has been observed, reports and studies highlighting its incidence and risk are lacking. To determine whether ALIF leads to an increased risk in L5 palsy, we sought to compare the relative risk compared to TLIF. We hypothesize that since foraminotomy is part of the TLIF procedure, it should demonstrate a difference in nerve root palsy compared to ALIF indirect decompression. A single institution retrospective cohort study. A total of 626 patients (262 ALIF, 179 open TLIF, 185 MIS TLIF). The study period was 2017 to 2021. Primary outcomes were postoperative leg pain, sensory deficits, and motor weakness in tibialis anterior (TA), extensor hallucis longus (EHL) and gastrocnemius (GC). Secondary outcomes were infection, return to operating room (OR), and return to emergency center (EC) within 90 days. Retrospective comparative cohort study comparing ALIF vs TLIF. Inclusion criteria were all patients who underwent L5-S1 ALIF or L5-S1 TLIF (both open and MIS). Multilevel surgeries were excluded. The rate of postop nerve palsy was compared for the two treatment approaches. Chi-square was performed for all categorical comparisons and ANOVA was performed for continuous statistical comparisons. There were subtle differences in baseline characteristics between groups. ALIF patients were younger (p = 0.016), had less BMI (p = 0.026) and less likely to smoke (p = 0.008). There were no differences in gender or diabetes status. Patients undergoing TLIF (open and MIS) were more likely to be operated for lumbar spinal stenosis and radiculopathy (p < 0.001). There was an overall 3% rate of neuro deficits in the study population with a higher rate in those undergoing ALIF (5.3%) compared with open TLIF (0.6%) and MIS TLIF (2.2%) (p = 0.011). There was a rate of 3.1% EHL palsy in the ALIF group which was higher than TLIF (both open and MIS) (p = 0.048). There was a trend towards higher TA and GC nerve deficits in the ALIF group, but the difference was not significant. Additionally, there was a trend towards higher rates of return to OR for nerve deficit in the ALIF group, but this was not significant. However, ALIF patients had higher return to OR in 90 days for any reason (p = 0.01). There were no further differences between the groups. Among the 14 ALIF patients with any nerve deficit, 7 followed up at 3 mos and 5 in 1 year. At 3 mos, 5 of 7 patients had improvement in their nerve deficit and at 1 year, 5 of 5 patients had improved their deficiency. This study demonstrates a higher rate of L5 nerve root palsy with ALIF compared to TLIF as evidenced by higher rates of EHL palsy with a rate of 3.1% in our study population. The study, however, is limited by its retrospective nature and subtle differences noted in demographics. Despite these differences, ALIF patient characteristics tended to be more favorable, which are unlikely to confound results of higher postoperative nerve deficits. Further study will be required to understand the mechanisms and radiological risk factors for postoperative L5 palsy after ALIF.

BACKGROUND CONTEXT VBT takes advantage of the Hueter-Volkmann principle, and modulates growth across intervertebral disc spaces with a tensioned tether secured at the lateral aspects of vertebral bodies. Cervical deformity in AIS patients is associated with lower health related quality of life. PSF constructs have been shown to improve cervical deformity, however, to date, these relationships have not been described in patients treated with VBT. PURPOSE Determine if cervical sagittal alignment parameters following VBT for correction of AIS are similar to what is observed following PSF. STUDY DESIGN/SETTING Multi-center retrospective cohort study. PATIENT SAMPLE Patients with AIS that undergo correction surgeries with LIV in the lumbar spine from 2013 to 2021 with pre- and 2-year postop standing full body plain films available. OUTCOME MEASURES Outcome measures: Age, height, weight, BMI, Risser score, LIV and levels instrumented. Radiographic analysis included pre- and postop C2 to C7 sagittal vertical axis (cSVA), cervical lordosis angle (CL), T1 slope and thoracic kyphosis (TK). METHODS Measures were compared using independent samples t-tests, significance set at p<0.05. RESULTS A total of 99 patients: 49 VBT and 50 fusions. The VBT cohort Lenke class breakdown is 23% 1A, 13% 1C, 31% 3C; 18% 5C, and 15% 6C, while the PSF cohort consisted of 42% 1A, 6% 1B, 2% 2C, 2% 3B, 12% 3C, 2% 5B, 24% 5C, and 10% 6C. There were no significant differences with regard to patient age or number of levels instrumented. Patients included in the VBT cohort had a lower level of bone maturity as defined by Risser class (1.6±0.9 vs 2.6±1.8, p=0.001). The VBT cohort had higher baseline cSVA (3.4mm±1.6 vs -1.0mm±3.1, 0.001) and less CL (-0.6°±18.2 vs 11.6°±12.8, p=0.001) than the fusion cohort. No differences in baseline T1 slope or Thoracic Kyphosis was observed. VBT patients also had higher 2-year cSVA (3.4mm±1.4 vs -3.7mm±2.1, p=0.001) and less CL (-4.0±18.5 vs 7.0±12.2, p=0.001) compared to fusion patients. The PSF group had a significantly greater correction in cSVA than the VBT group (2.8mm±4.0 vs 0mm±1.6, p=0.001). Both groups displayed improvement in radiographic parameters of cervical and thoracic alignment including CL (VBT 3.3°vs 4.3°, p=0.74), T1 slope (VBT -4.3°vs -4.9°, p=0.81) and TK (VBT -6.1°vs -3.9°, p=0.47). After PSM for Lenke classification, 66 patients remained: 33 VBT, 33 PSF. The PSF group continued to demonstrate greater improvement in cSVA than the VBT group (3.2mm±3.0 vs -0.3±1.8, p=0.001. CONCLUSIONS VBT and PSF both improve radiographic parameters of cervical alignment in AIS patients; however, PSF showed greater correction of cSVA at 2-year followup. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. VBT takes advantage of the Hueter-Volkmann principle, and modulates growth across intervertebral disc spaces with a tensioned tether secured at the lateral aspects of vertebral bodies. Cervical deformity in AIS patients is associated with lower health related quality of life. PSF constructs have been shown to improve cervical deformity, however, to date, these relationships have not been described in patients treated with VBT. Determine if cervical sagittal alignment parameters following VBT for correction of AIS are similar to what is observed following PSF. Multi-center retrospective cohort study. Patients with AIS that undergo correction surgeries with LIV in the lumbar spine from 2013 to 2021 with pre- and 2-year postop standing full body plain films available. Outcome measures: Age, height, weight, BMI, Risser score, LIV and levels instrumented. Radiographic analysis included pre- and postop C2 to C7 sagittal vertical axis (cSVA), cervical lordosis angle (CL), T1 slope and thoracic kyphosis (TK). Measures were compared using independent samples t-tests, significance set at p<0.05. A total of 99 patients: 49 VBT and 50 fusions. The VBT cohort Lenke class breakdown is 23% 1A, 13% 1C, 31% 3C; 18% 5C, and 15% 6C, while the PSF cohort consisted of 42% 1A, 6% 1B, 2% 2C, 2% 3B, 12% 3C, 2% 5B, 24% 5C, and 10% 6C. There were no significant differences with regard to patient age or number of levels instrumented. Patients included in the VBT cohort had a lower level of bone maturity as defined by Risser class (1.6±0.9 vs 2.6±1.8, p=0.001). The VBT cohort had higher baseline cSVA (3.4mm±1.6 vs -1.0mm±3.1, 0.001) and less CL (-0.6°±18.2 vs 11.6°±12.8, p=0.001) than the fusion cohort. No differences in baseline T1 slope or Thoracic Kyphosis was observed. VBT patients also had higher 2-year cSVA (3.4mm±1.4 vs -3.7mm±2.1, p=0.001) and less CL (-4.0±18.5 vs 7.0±12.2, p=0.001) compared to fusion patients. The PSF group had a significantly greater correction in cSVA than the VBT group (2.8mm±4.0 vs 0mm±1.6, p=0.001). Both groups displayed improvement in radiographic parameters of cervical and thoracic alignment including CL (VBT 3.3°vs 4.3°, p=0.74), T1 slope (VBT -4.3°vs -4.9°, p=0.81) and TK (VBT -6.1°vs -3.9°, p=0.47). After PSM for Lenke classification, 66 patients remained: 33 VBT, 33 PSF. The PSF group continued to demonstrate greater improvement in cSVA than the VBT group (3.2mm±3.0 vs -0.3±1.8, p=0.001. VBT and PSF both improve radiographic parameters of cervical alignment in AIS patients; however, PSF showed greater correction of cSVA at 2-year followup.