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Study Design: Comparative cohort study. Objective: Factors that influence the lower instrumented vertebra (LIV) selection in adult cervical deformity (ACD) are less reported, and outcomes in the cervicothoracic junction (CTJ) and proximal thoracic (PT) spine are unclear. Methods: A prospective ACD database was analyzed using the following inclusion criteria: LIV between C7 and T5, upper instrumented vertebra at C2, and at least a 1-year follow-up. Patients were divided into CTJ (LIV C7-T2) and PT groups (LIV T3-T5) based on LIV levels. Demographics, operative details, radiographic parameters, and the health-related quality of life (HRQOL) scores were compared. Results: Forty-six patients were included (mean age, 62 years), with 22 and 24 patients in the CTJ and PT groups, respectively. Demographics and surgical parameters were comparable between the groups. The PT group had a significantly higher preoperative C2-C7 sagittal vertical axis (cSVA) (46.9 mm vs 32.6 mm, P = 0.002) and T1 slope minus cervical lordosis (45.9° vs 36.0°, P = 0.042) than the CTJ group and was more likely treated with pedicle-subtraction osteotomy (33.3% vs 0%, P = 0.004). The PT group had a larger correction of cSVA (−7.7 vs 0.7 mm, P = 0.037) and reciprocal change of increased T4-T12 kyphosis (8.6° vs 0.0°, P = 0.001). Complications and reoperations were comparable. The HRQOL scores were not different preoperatively and at 1-year follow-up. Conclusions: The selection of PT LIV in cervical deformities was more common in patients with larger baseline deformities, who were more likely to undergo pedicle-subtraction osteotomy. Despite this, the complications and HRQOL outcomes were comparable at 1-year follow-up.

Study Design: Retrospective cohort study. Objective: To investigate correlations between preoperative supine imaging and postoperative alignment. Methods: A retrospective review was conducted of a single-institution database of patients with adult spinal deformity (ASD). Patients were stratified by fusion location in the lumbar or thoracic spine. Outcomes of interest were postoperative lumbar lordosis (LL) and thoracic kyphosis (TK). Sagittal alignment parameters were compared and correlation analyses were performed. Multilinear stepwise regression was conducted to identify independent predictors of postoperative LL or TK. Regression analyses were repeated within the lumbar and thoracic fusion cohorts. Results: A total of 99 patients were included (mean age 63.2 years, 83.1% female, mean body mass index 27.3 kg/m2). Scoliosis Research Society classification demonstrated moderate to severe sagittal and/or coronal deformity (pelvic tile modifier, 18.2% ++; sagittal vertical axis, 27.3% ++, pelvic incidence minus lumbar lordosis mismatch, 29.3% ++, SRS type, 29.3% N type curve and 68.7% L or D type curve). A total of 73 patients (73.7%) underwent lumbar fusion and 50 (50.5%) underwent thoracic fusion. Correlation analyses demonstrated a significant association between pre- and postoperative LL and TK. Multilinear regression demonstrated that LL supine and pelvic incidence were significant predictors of postoperative LL ( r2 = 0.568, P < .001). LL supine, TK supine, and age were significant predictors of postoperative TK ( r2 = 0.490, P < .001). Conclusion: Preoperative supine films are superior to standing in predicting postoperative alignment at 1-year follow-up. Anticipation of undesired alignment changes through supine imaging may be useful in mitigating the risk of iatrogenic malalignment.

Study Design: Retrospective single-center study. Objective: Investigate the effect of posterior instrumentation on the relationship between lordosis and kyphosis. Methods: Surgically treated patients with a minimum of 6 months of follow-up were analyzed. Asymptomatic volunteers served to show the normal anatomical relationship between thoracic and lumbar curves. Patients were stratified based on postoperative instrumentation: “Thoracic Fusion” = complete fusion of thoracic spine; “Lumbar Fusion” = complete fusion of lumbar spine; and “Complete Fusion” = fusion from sacrum to at least T5. Bivariate correlations and regression analysis were used to evaluate the relationship between change in thoracic kyphosis (ΔTK) and change in spinopelvic mismatch (ΔPI-LL; pelvic incidence-lumbar lordosis) before and after fusion. Analyses were repeated in “Lumbar Fusion” patients with flexible preoperative thoracic spines. Results: For asymptomatic volunteers, the natural anatomical relationship between TK and LL was found to be TK = 41% of LL ( r = 0.425, P < .001). A total of 153 of 167 adult spinal deformity patients were included (62 years old, 26.7 kg/m2, 78% female). Mean follow-up was 11.5 ± 6.8 months. “Thoracic Fusion” group showed no alteration in the natural relationship between TK and LL (ΔTK = 39% ΔPI-LL), whereas “Lumbar Fusion” group had a reduction in reciprocal change (ΔTK = 34% ΔPI-LL) although a subanalysis of patients in the “Lumbar Fusion” group with flexible thoracic spines showed a marked compensation in reciprocal change with (ΔTK = 58% ΔPI-LL). Conclusion: The relationship between ΔTK and ΔPI-LL is dependent on level instrumented. “Thoracic Fusion” drives change in LL while this relationship is affected by TK’s natural stiffness in “Lumbar Fusion” patients.

Study Design: Retrospective cohort study. Objective: To compare the outcomes of patients with adult spinal deformity (ASD) following spinal fusion with the lowest instrumented vertebra (LIV) at L4/L5 versus S1/ilium. Methods: A multicenter ASD database was evaluated. Patients were categorized into 2 groups based on LIV levels—groups L (fusion to L4/L5) and S (fusion to S1/ilium). Both groups were propensity matched by age and preoperative radiographic alignments. Patient demographics, operative details, radiographic parameters, revision rates, and health-related quality of life (HRQOL) scores were compared. Results: Overall, 349 patients had complete data, with a mean follow-up of 46 months. Patients in group S (n = 311) were older and had larger sagittal and coronal plane deformities than those in group L (n = 38). After matching, 28 patients were allocated to each group with similar demographic, radiographic, and clinical parameters. Sagittal alignment restoration at postoperative week 6 was significantly better in group S than in group L, but it was similar in both groups at the 2-year follow-up. Fusion to S1/ilium involved a longer operating time, higher PJK rates, and greater PJK angles than that to L4/L5. There were no significant differences in the complication and revision rates between the groups. Both groups showed significant improvements in HRQOL scores. Conclusions: Fusion to S1/ilium had better sagittal alignment restoration at postoperative week 6 and involved higher PJK rates and greater PJK angles than that to L4/L5. The clinical outcomes and rates of revision surgery and complications were similar between the groups.

OBJECTIVE Preoperative planning for adult spinal deformity (ASD) surgery is essential to prepare the surgical team and consistently obtain postoperative alignment goals. Positional imaging may allow the surgeon to evaluate spinal flexibility and anticipate the need for more invasive techniques. The purpose of this study was to determine whether spine flexibility, defined by the change in alignment between supine and standing imaging, is associated with the need for an osteotomy in ASD surgery. METHODS A single-center, dual-surgeon retrospective analysis was performed of adult patients with ASD who underwent correction of a thoracolumbar deformity between 2014 and 2018 (pelvis to upper instrumented vertebra between L1 and T9). Patients were stratified into osteotomy (Ost) and no-osteotomy (NOst) cohorts according to whether an osteotomy was performed (Schwab grade 2 or higher). Demographic, surgical, and radiographic parameters were compared. The sagittal correction from intraoperative prone positioning alone (sagittal flexibility percentage [Sflex%]) was assessed by comparing the change in lumbar lordosis (LL) between preoperative supine to standing radiographs and preoperative to postoperative alignment. RESULTS Demographics and preoperative and postoperative sagittal alignment were similar between the Ost (n = 60, 65.9%) and NOst (n = 31, 34.1%) cohorts (p > 0.05). Of all Ost patients, 71.7% had a grade 2 osteotomy (mean 3 per patient), 21.7% had a grade 3 osteotomy, and 12.5% underwent both grade 3 and grade 2 osteotomies. Postoperatively, the NOst and Ost cohorts had similar pelvic incidence minus lumbar lordosis (PI-LL) mismatch (mean PI-LL 5.2° vs 1.2°; p = 0.205). Correction obtained through positioning (Sflex%) was significantly lower for in the osteotomy cohort (38.0% vs 76.3%, p = 0.004). A threshold of Sflex% < 70% predicted the need for osteotomy at a sensitivity of 78%, specificity of 56%, and positive predictive value of 77%. CONCLUSIONS The flexibility of the spine is quantitatively related to the use of an osteotomy. Prospective studies are needed to determine thresholds that may be used to standardize surgical decision-making in ASD surgery.

OBJECTIVE Supine radiographs have successfully been used for preoperative planning of lumbar deformity corrections. However, they have not been used to assess thoracic flexibility, which has recently garnered attention as a potential contributor to proximal junctional kyphosis (PJK). The purpose of this study was to compare supine to standing radiographs to assess thoracic flexibility and to determine whether thoracic flexibility is associated with PJK. METHODS A retrospective study was conducted of a single-institution database of patients with adult spinal deformity (ASD). Sagittal alignment parameters were compared between standing and supine and between pre- and postoperative radiographs. Thoracic flexibility was determined as the change between preoperative standing thoracic kyphosis (TK) and preoperative supine TK, and these changes were measured over the overall thoracic spine and the fused portion of the thoracic spine (i.e., TK fused). A case-control analysis was performed to compare thoracic flexibility between patients with PJK and those without (no PJK). The cohort was also stratified into three groups based on thoracic flexibility: kyphotic change (increased TK), lordotic change (decreased TK), and no change. The PJK rate was compared between the cohorts. RESULTS A total of 101 patients (mean 63 years old, 82.2% female, mean BMI 27.4 kg/m2) were included. Preoperative Scoliosis Research Society–Schwab ASD classification showed moderate preoperative deformity (pelvic tilt 27.7% [score ++]; pelvic incidence–lumbar lordosis mismatch 44.6% [score ++]; sagittal vertical axis 42.6% [score ++]). Postoperatively, the average offset from age-adjusted alignment goals demonstrated slight overcorrection in the study sample (−8.5° ± 15.6° pelvic incidence–lumbar lordosis mismatch, −29.2 ± 53.1 mm sagittal vertical axis, −5.4 ± 10.8 pelvic tilt, and −7.6 ± 11.7 T1 pelvic angle). TK decreased between standing and supine radiographs and increased postoperatively (TK fused: −25.3° vs −19.6° vs −29.9°; all p < 0.001). The overall rate of radiographic PJK was 23.8%. Comparisons between PJK and no PJK demonstrated that offsets from age-adjusted alignment goals were similar (p > 0.05 for all). There was a significant difference in the PJK rate when stratified by thoracic flexibility cohorts (kyphotic: 0.0% vs no change: 18.4% vs lordotic: 35.0%; p = 0.049). Logistic regression revealed thoracic flexibility (p = 0.045) as the only independent correlate of PJK. CONCLUSIONS Half of patients with ASD experienced significant changes in TK during supine positioning, a quality that may influence surgical strategy. Increased thoracic flexibility is associated with PJK, possibly secondary to fusing the patient’s spine in a flattened position intraoperatively.

OBJECTIVE Recombinant human bone morphogenetic protein–2 (rhBMP-2) has been shown to increase fusion rates; however, cost, limited FDA approval, and possible complications impact its use. Decisions regarding rhBMP-2 use and changes over time have not been well defined. In this study, the authors aimed to assess changes in rhBMP-2 use for adult spinal deformity (ASD) surgery over the past decade. METHODS A retrospective review of the International Spine Study Group prospective multicenter database was performed to identify ASD patients treated surgically from 2008 to 2018. For assessment of rhBMP-2 use over time, 3 periods were created: 2008–2011, 2012–2015, and 2016–2018. RESULTS Of the patients identified, 1180 met inclusion criteria, with a mean age 60 years and 30% of patients requiring revision surgery; rhBMP-2 was used in 73.9% of patients overall. The mean rhBMP-2 dose per patient was 23.6 mg. Patients receiving rhBMP-2 were older (61 vs 58 years, p < 0.001) and had more comorbidities (Charlson Comorbidity Index 1.9 vs 1.4, p < 0.001), a higher rate of the Scoliosis Research Society–Schwab pelvic tilt modifier (> 0; 68% vs 62%, p = 0.026), a greater deformity correction (change in pelvic incidence minus lumbar lordosis 15° vs 12°, p = 0.01), and more levels fused (8.9 vs 7.9, p = 0.003). Over the 3 time periods, the overall rate of rhBMP-2 use increased and then stabilized (62.5% vs 79% vs 77%). Stratified analysis showed that after an overall increase in rhBMP-2 use, only patients who were younger than 50 years, those who were smokers, those who received a three-column osteotomy (3CO), and patients who underwent revision sustained an increased rate of rhBMP-2 use between the later two periods. No similar increases were noted for older patients, nonsmokers, primary surgery patients, and patients without a 3CO. The total rhBMP-2 dose decreased over time (26.6 mg vs 24.8 mg vs 20.7 mg, p < 0.001). After matching patients by preoperative alignment, 215 patients were included, and a significantly lower rate of complications leading to revision surgery was observed within the 2012–2015 period compared with the 2008–2011 (21.4% vs 13.0%, p = 0.029) period, while rhBMP-2 was increasingly used (80.5% vs 66.0%, p = 0.001). There was a trend toward a lower rate of pseudarthrosis for patients in the 2012–2015 period, but this difference did not reach statistical significance (7% vs 4.2%, p = 0.283). CONCLUSIONS The authors found that rhBMP-2 was used in the majority of ASD patients and was more commonly used in those with greater deformity correction. Additionally, over the last 10 years, rhBMP-2 was increasingly used for ASD patients, but the dose has decreased.

BACKGROUND CONTEXT Flattening of the thoracic spine is a common biomechanical compensatory mechanism for adult spinal deformity (ASD). The literature shows that younger ASD patients recruit more thoracic flattening than older patients. It is hypothesized that differences in muscle quality between younger and older ASD patients explains this difference in the recruitment of thoracic compensation. PURPOSE Investigate the relationship between paraspinal muscle degeneration and recruitment of thoracic compensation. STUDY DESIGN/SETTING Retrospective review of a prospective database. PATIENT SAMPLE ASD patients from a prospective database. OUTCOME MEASURES Posterior paraspinal muscle fat infiltration, thoracic kyphosis between T4 and T12 (TK) and pelvic retroversion (PT). METHODS ASD patients with spino-pelvic deformity (defined as SRS-Schwab PI-LL modifier of + or ++) and available pre-op CT imaging were identified from a retrospective database. Patients with previous fusion of the thoracic spine were excluded. Erector spinae and multifidus measurements were manually contoured on CT imagesat three vertebral levels (T2, T10, and L3), at three locations per level: immediately inferior to the superior end plate, in the middle of the vertebral body, and superior to the inferior end plate. Fat infiltration (Fat) within each muscle was defined as the number of voxels with a Hounsfield unit (HU) corresponding to fat (-190 to 0) divided by the total number of voxels. The maximum fat infiltration (MaxFat) was determined by taking the muscle with the highest percentage of Fat. After a Pearson correlation analysis, the cohort was separated into 2 groups: high Fat (HFat) and Low Fat (LFat) based on MaxFat threshold of 35%. Demographics and radiographic parameters including TK and PT were compared between groups. RESULTS Of the 57 patients (mean age 61 yrs, 75% F, BMI 28) that met inclusion, 26% had a fused lumbar spine. Assessed by +/++ SRS-Schwab modifiers, 90% of patients had severe PT malalignment and 75% a severe SVA malalignment. Breakdown of Fat and area by vertebral level was: T2 (35% and 1332mm²), T10 (30% and 1910mm²), L3 (38% and 3915mm²). TK correlated significantly with Fat at all levels from T2 to L3 (r=-0.498, r=-0.519, r=-0.472), FatMax (r=-0.470) and area at T10 (r=-0.341). PT correlated significantly with FatMax (r=0.333) and T10 Fat(r=0.548). After grouping, 31 pts were HFat, and 25 pts were LFat. HFat pts were older (64.2 vs 56.3, p=0.047) and had a greater BMI (30.1 vs 25, p=0.002). The groups did not differ in sex or rates of lumbar fusion. In terms of spinal alignment, HFat pts had a higher T1 pelvic angle (30.7° vs 23.7°), a higher TK (-34.6° vs -22.9°), and a higher PT (30.1° vs 25.2°), without difference in lumbar deformity or other sagittal parameters. CONCLUSIONS Patients with higher fat infiltration in paraspinal muscles show less compensation with the thoracic spine than patients with leaner musculature, despite having similar lumbar deformities. Consequently, patients with degenerative paraspinal musculature have more pelvic retroversion, causing greater gait disruption due to limitation in hip extension. The assessment of fatty infiltration in posterior paraspinal muscles could help identify patient compensatory profile and aid in surgical planning. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT Several guidelines for target-selection in the literature utilize pelvic incidence (PI) as a marker for lumbar correction. In practice, postoperative alignment is highly affected by preoperative data, including demographics and spinal flexibility. Preoperative supine radiographs allow for early visualization of patient alignment in the intraoperative position. Our objective was to determine the strongest predictor of postoperative alignment among PI, age and preoperative supine alignment using a retrospective, single center database of adult spinal deformity (ASD) patients. PURPOSE Identify independent predictors of postoperative curvatures (LL and TK) using preoperative data only. STUDY DESIGN/SETTING Retrospective review of a single-center database of ASD patients. PATIENT SAMPLE A total of 99 surgically treated ASD patients with minimum 1 year follow-up. OUTCOME MEASURES L1-S1 lordosis, T4-T12 kyphosis. METHODS Pre- to postoperative analysis was conducted using paired t-test sampling. Patients were stratified by region of fusion postoperative: complete lumbar fusion (from L1 to S1) and/or complete thoracic fusion (from T4 to T12). Pearson's r correlation analysis was performed on postoperative curvatures (LL and TK) with preoperative alignment in both standing and supine positions. Correlation analysis was repeated for LL in patients with complete lumbar fusion and for TK in patients with complete thoracic fusion. Lastly, a multilinear stepwise regression was conducted to identify independent predictors of LL or TK post-op. RESULTS A total of 99 patients were included in the analysis (63.2yo, 83.1%F, 27.3kg/m2, mean f/u 21 months±.9.8). Preoperative SRS classification demonstrated a moderate to severe sagittal and/or coronal deformity (PT modifier: 18.2% ++, SVA: 27.3% ++, PI-LL: 29.3% ++, SRS type: 29.3% N and 68.7% L or D). Sagittal alignment significantly improved between pre- and postoperative (all p CONCLUSIONS Preoperative supine alignment is one of the best predictors of postoperative alignment at 1 year. When controlling for fusion location, results show an even greater importance of supine alignment, especially regarding thoracic alignment. Specific attention is required when performing thoracic fusion to avoid thoracic flattening FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT Bone morphogenetic protein (BMP) has been shown to increase fusion rates but cost, limited FDA approval, and possible complications impact its use. Decisions regarding BMP use and changes over time have not been well defined. PURPOSE To assess applications and dosing of BMP for adult spinal deformity (ASD) surgery and how these have changed over the past 10 years. STUDY DESIGN/SETTING Retrospective review of prospective multicenter database. PATIENT SAMPLE ASD patients from a prospective multicenter database. OUTCOME MEASURES BMP applications and dosing and changes over the past decade. METHODS ASD patients treated surgically from 2008-2018 with data available on BMP use were identified from a prospective multicenter database. Demographics, comorbidities, radiographic parameters, and surgical data were collected, including use of BMP, location of BMP use (anterior, posterior, or combined) and BMP dose. For assessment of BMP use over time, 3 intervals were created: 2008-2011 (n=312), 2012-2015 (n=433), and 2016-2018 (n=435). RESULTS A total of 1,180 patients met inclusion (mean age 60 yrs, 30% revision surgery). At baseline, patients had high disability (mean SRS-22 2.8, ODI 44, PCS 31.5), high frailty (mean ASD FI 1.8), and high comorbidities (mean Charlson 3.4). Sagittal malalignment was severe in more than 65% of patients based on SRS-Schwab modifiers. BMP was used in 73.9% of cases overall and in 72.7% of posterior-only and 72.1% of combined approach surgeries. For IBF, mean dose was 9.1 mg and use and dose increased from T10-11 to L5-S1 (1% vs 29.4% and 2 vs 4.7mg, respectively). Mean dose of BMP was 23.5 mg for posterior fusion. Patients receiving BMP had greater age (61.1 vs 57.9 yrs, p 0: 55.9% vs 70.8% vs 67.9%, respectively, p=0.003) and a higher incidence of previous surgery (21.5% vs 32.7% vs 34.0%, respectively, p=0.006). Similar increases were not noted for patients who did not receive BMP. For patients with posterior fusion without IBF, BMP use has increased over time (50.8% vs 75.2% vs 90.6%, respectively, p CONCLUSIONS In this large multicenter ASD series, BMP was used in the majority of cases, more commonly in older patients with greater frailty, greater comorbidities, and worse sagittal alignment. Over the last 10 years, BMP has been increasingly used for patients with greater severity of deformity and history of previous surgery. Although BMP use has continued to increase significantly for posterior-only surgery, the dose used has decreased. FDA DEVICE/DRUG STATUS Unavailable from authors at time of publication.

BACKGROUND CONTEXT Often patients with cervical deformity (CD) require extensive fusions that extend into the thoracic spine. However, factors that influence the treatment approach and level selection are poorly understood. PURPOSE To examine if there are significant differences between patients with CD who have a lowest instrumented vertebrae (LIV) to the upper thoracic (UT) vs the midthoracic (MT) spine. STUDY DESIGN/SETTING Comparative cohort study. PATIENT SAMPLE Prospective adult cervical deformity database. OUTCOME MEASURES NDI, mJOA, SWAL-QOL. METHODS A prospective CD database was analyzed for the following inclusion criteria: LIV between C7-T5 and a UIV of C2, and 1 yr min follow-up (f/u). Patient demographics, operative details, radiographic parameters and clinical outcomes were compared between those with a LIV from C7-T2 (UT) vs T3-T5 (MT). X2 and independent samples T-Tests were performed for statistical analysis RESULTS A total of 64 patients met inclusion criteria for the study and 46 were included in the analysis (avg. age 62, 58% female, avg 1yr f/u) with 22 in UT vs 24 in the MT groups. No differences were seen in age or revision case prevalence, EBL, operative time or surgical approach (anterior, posterior, combined) types between groups. MT patients had a higher pre-op cSVA, TS-CL, Max Kyphosis and T9PA and were treated with a larger number of PSOs (p CONCLUSIONS Similar radiographic and clinical outcomes can be expected for UT vs MT LIVs when treating CD. Those undergoing MT had larger cervical deformities and were more likely to undergo a PSO for correction. Despite this, there were no significant differences in the rates of major and minor complications or DJK. The MT group had a higher rate revision (5% vs 21%, p=0.19) that did not reach statistical significance. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.