Faculty Bibliography

BACKGROUND CONTEXT: In transforminal lumbar interbody fusion (TLIF), bilateral pedicle screw/rod fixation has been shown to increase fusion construct stability and decrease posterior instrumentation stress when compared to unilateral instrumentation. However, unilateral instrumentation is beneficial over bilateral instrumentation due to shorter operative time, less blood loss and reduced implant costs. It is important to note though that comparative studies between unilateral and bilateral instrumentation in TLIF have shown similar patient satisfaction outcomes, they are limited in their evaluation of complications due to small sample size of studies. PURPOSE: The purpose of this meta-analysis was to evaluate complications, and fusion rates between unilateral and bilateral instrumentation in TLIF. STUDY DESIGN/SETTING: Meta-analysis of randomized controlled trials. PATIENT SAMPLE: 549 patients undergoing one- and multi-levels TLIF. OUTCOME MEASURES: Outcome data extracted included fusion rates, health related quality of life (HRQoL) scores and complications including cage migration, dural tear, deep vein thrombosis, surgical site infections and screw failures. METHODS: Randomized controlled trials (RCTs) that compared outcomes between unilateral and bilateral pedicle screw instrumentation in single- and multi-level TLIF were identified. Data extraction was performed by two independent reviewers. Meta-analysis was performed using RevMan 5. Weighted standardized mean difference (SMD) and odds ratio (OR) 95% confidence intervals (CI) were calculated. Jadad scoring was used to assess bias of included studies. RESULTS: Eight RCTs were included, having a total of 549 patients (267 unilateral/282 bilateral). Minimum follow-up ranged from 3 to 24 months. Bias-assessment scores varied between 0 and 3 indicating high-moderate bias-risk. Six involved open TLIF procedures and two involved minimally invasive TLIF. There was no difference between postoperative Health Related Quality of Life scores in the unilateral and bilateral instrumented groups (SMD = 0.29; [-0.77, 0.18]; p=0.69). There was no statistical difference in fusion rates (OR = 0.47; 95% CI [0.21, 1.04], p=0.68), with 88.9% and 95.0% achieving fusion in the unilateral and bilateral groups, respectively. The unilateral cohort had a higher incidence of cage migration (5.6%) when compared to the bilateral cohort (2.5%), approaching statically significant (p=0.07). Other complications which included dural tears, deep vein thrombosis, surgical site infections and screw failures were comparable between the groups. CONCLUSIONS: Fusion rates and complications appear comparable in unilateral and bilateral instrumentation in TLIF. Though not statistically significant, there was higher incidence of cage migration in the unilateral cohort

BACKGROUND CONTEXT: Preoperative planning with objective is an important component of adult spinal deformity (ASD) surgery. Recent studies have expanded the SRS-Schwab classification for defining sagittal deformity by including age-adjusted ideals for postoperative alignment, but it is unknown whether surgical plans properly integrate these ideals. PURPOSE: Evaluate the discrepancies between age-adjusted alignment ideals and actual surgical plans. STUDY DESIGN/SETTING: Consecutively enrolled prospective database. PATIENT SAMPLE: 71 ASD patients with severe sagittal deformity. OUTCOME MEASURES: Radiographic measurements, surgeon-created alignment plans on dedicated software. METHODS: ASD patients >18 years of age with severe sagittal alignment (SVA >50mm, PT >20degree, or PI-LL >10degree) undergoing corrective surgery were consecutively enrolled. For each patient, the baseline X-ray images were measured and the operative plan was simulated using dedicated, validated software for spine measurement and surgical planning. Sagittal radiographic parameters were compared between baseline, the plan and the age-adjusted ideal. Thresholds for significant clinical differences between planned and ideal alignments were: SVA620mm, PT610degree, PI-LL610degree. RESULTS: 71 patients (63+/-11 years; 80% revisions) were included. Planned alignments matched age-adjusted ideals in 76% of cases for PT, 65% of PI-LL, and 49% of SVA. Compared to ideal alignment, a total of 30% and 17% of the patients were planned for overcorrection in SVA and PI-LL respectively; 21% (SVA) and 18% (PI-LL) were planned for undercorrection. Discrepancies between the plan and the ideal were not affected by BMI, comorbidities, gender, revision status or HRQOL. However, as age increased, the plan was more likely to overcorrect versus the ideal (P<0.003 for PT, PI-LL; P<0.001 for SVA). When compared to the ideal alignment formula, planned SVA was overcorrected in 58% of patients >70 years versus 20% in patients<70 (P=0.003), and planned SVA of these >70 years patients matched the age-adjusted alignment ideals of a 62-year-old. Plans for patients with severe deformity and/or higher PI were more likely to be undercorrected compared to ideals (P< 0.001). The discrepancy between planned and ideal alignment correlated significantly with the difference between the postoperative alignment and ideal alignment (P<0.001). PI-LL plans had a significant impact on postop alignment. When PI-LL plans called for ideal correction, the mean postop PI-LL was within 2degree of ideal alignment and matched the plan in 59% of cases. However, when PI-LL plans called for undercorrection, postop PI-LL was 13degree greater than ideal (P<0.001). When the planned alignment was within the ideal threshold, the postop PI-LL matched the ideal in 66% of cases, versus only 18% when the plan was over- or under-corrected. CONCLUSIONS: Preoperative plans for sagittal alignment correction overcorrected in comparison to age-adjusted ideals, especially in elderly patients. More severe deformity led to greater likelihood of having undercorrected plans. Favorable postoperative outcomes occurred when the planned alignment incorporated age-adjusted ideals. This emphasizes the importance of considering patient age and similar characteristics into the surgical strategy, as patient-specific plans, rather than generic approaches, are likely to produce the best outcome

BACKGROUND CONTEXT: Degenerative lumbar stenosis (DLS) patients adopt forward-bending posture as a compensatory mechanism, increasing spinal canal and foraminal volume. Previous data show laminectomy 6 short segment fusion results in improvement of sagittal vertical axis (SVA), pelvic tilt (PT) and PI-LL (pelvic incidence-lumbar lordosis) mismatch by SRS-Schwab classification in <25% of patients. The magnitude of deformity for which a DLS patient should have realignment remains unknown. PURPOSE: To identify differences in compensatory mechanisms between DLS and adult spinal deformity (ASD) patients with increasing, and to identify at what point DLS patients recruit ASD-type compensatory mechanisms. STUDY DESIGN/SETTING: Retrospective clinical and radiological review. PATIENT SAMPLE: Baseline X-ray images of 239 patients without spinal instrumentation, with the clinical radiological and diagnosis of DLS or ASD were assessed for patterns of spino-pelvic compensatory mechanisms. Patients were stratified by sagittal vertical axis (SVA) by the Schwab-SRS classification. OUTCOME MEASURES: Radiographic spino-pelvic parameters were measured in the DLS and ASD groups, including SVA, PI-LL, T1SPi, TPA and PT. METHODS: Patients were identified using a single-institution database with sole diagnosis of DLS, >40 years and if they had any of the following: PT >25degree, SVA >5cm, thoracic kyphosis (TK) >60degree or PI-LL mismatch >10degree. The patient's diagnosis was taken from the patient history chart based on correlation between history, examination and available imaging. Matched cohort with sole diagnosis of ASD was identified. Groups were stratified by SVA using Schwab-SRS classification: 0(<4cm), +(4-9.5cm), ++( >9.5cm). Sagittal spino-pelvic parameters were compared between the 2 groups with unpaired t-test. RESULTS: 239 patients were identified (122 DLS, 117 ASD). There was no difference in age or pelvic incidence between DLS and ASD with SVA stratifications. DLS patients with SVA 0 had less PT (19.8degree vs 29.2degree p<0.0001), less PI-LL mismatch (3.3degree vs 15.8degree, p<0.001), lower TPA (14.6degree vs 21.8degree, p<0.001) but higher T1SPi (-5.17degree vs -7.44degree, p< 0.001) than those with ASD. DLS patients with SVA+ had less PT (22.6degree vs 26.1degree, p=0.019) and higher T1SPi (0.64degree vs -0.70degree, p=0.008) than ASD patients. DLS patients resembled a decompensated deformity with a higher T1SPi relative to TPA when compared to the ASD cohort in groups 0 and +. No significant differences between ASD and DLS for any parameters in the SVA++ group were identified. No difference was found between DLS or ASD in TK for SVA groups 0, + or ++. CONCLUSIONS: The difference in PI-LL observed in ASD/DLS group '0' underlies the pathogenesis of ASD vs DLS. DLS patients increase SVA for neuronal decompression but without a PI-LL mismatch, they need not increase PT. As PI-LL increases in SVA >9.5cm, recruitment of PT ensues as the need for alignment overtakes desire for decompression. Their compensatory mechanism then resembles ASD. Laminectomy 6 fusion may be more appropriate for DLS patients with SVA< 9.5cm. Given <25% of patients improve in classification after fusion, surgeons should consider realignment surgery in DLS with SVA >9.5cm. Further understanding of HRQOL scores in mal-aligned DLS patients is required to best understand the importance of alignment in DLS

BACKGROUND CONTEXT: TPA (T1 pelvic angle) is a valuable perioperative planning tool that accounts for both pelvic tilt (PT) and trunk inclination. While this parameter correlates with patient reported outcomes, it is limited as a standalone parameter because it does not distinguish patients' ability to compensate with pelvic retroversion. PURPOSE: Investigate the TPA and its close relation with pelvic tilt in order to assess patients HRQOL (health-related quality of life) with a given TPA and a varying PT. STUDY DESIGN/SETTING: Retrospective cohort. PATIENT SAMPLE: Single-center study of 230 patients (58.7+/-15.5 years old, 60% females) with full body radiographs, HRQOL forms and TPA>10degree. OUTCOME MEASURES: Sagittal spino-pelvic parameters including SVA, PT, PI-LL, and TPA, and the following health related quality of life questionnaires: ODI and EQ-5D. METHODS: Proportions of PT to TPA (PTp5PT/TPA) and T1SPi to TPA (T1SPip5T1SPi/TPA) were calculated and investigated against increased values of TPA. Then, two sub-groups of similar TPA were created (HighPT and LowPT) based on mean (PTp)60.5 standard deviation. HighPT and LowPT were compared across the entire cohort using an unpaired T-test. RESULTS: Mean sagittal parameters included: PI-LL 12.3+/-16.3degree, SVA 41+/-49mm, TPA 21.9+/-10.1degree and PT 24.4+/-8.6degree. The analysis of PTp distribution revealed a decrease in PT recruitment as TPA increases (137+/-39% for patients with TPA<15degree, 87+/-15% for patients with TPA >40degree). Comparing LowPT (n=57) with HighPT (n=69) revealed that for a similar TPA (24.1 vs 22.1degree, p=0.308), patients with LowPT (and therefore little compensatory PT) had significantly worse HRQOL scores in terms of ODI (45 vs 32 in HighPT; p=0.002) and EQ-5D (9.7 vs 8.5 in HighPT, p=0.003). CONCLUSIONS: While TPA captures the severity of deformity, disability is a product of deformity severity and the inability to recruit compensatory mechanisms. TPA measures the severity of the thoracolumbar deformity separate from pelvic compensation. Therefore, to develop a complete picture of standing sagittal alignment, TPA should be considered in conjunction with PT to convey the full radiological and clinical picture. Failing to do so potentially results in inadequate assessment of a patient's disability

BACKGROUND CONTEXT: Complications in ASD are frequent and surgeons are constantly attempting to decrease these and improve their outcomes. Centers have developed systems using 2 attending surgeons in attempts to improve efficiency in the operating room (OR). PURPOSE: The purpose of our study is to assess operative, clinical and radiographic outcomes of ASD surgery based on performance by 1 vs 2 attending surgeons from a multicenter (ISSG) database. STUDY DESIGN/SETTING: Retrospective review of prospectively collected multicenter data. PATIENT SAMPLE: 188 patients had ASD surgery performed by 1 surgeon (1S) and 77 were performed by 2 attendings (2S). OUTCOME MEASURES: Perioperative variables included EBL, length of stay (LOS) and operative time. Complications were recorded and X-ray parameters include: sagittal vertical axis (SVA), pelvic tilt and pelvic incidence - lumbar lordosis (PI-LL). Patients were classified by SRS-Schwab modifier grades. HRQOL questionnaires (Oswestry Disability Index [ODI], SRS-22r and Short Form SF-12) were analyzed. METHODS: Patients with surgical ASD with >5 levels posterior fusion with >2-year follow up were included. Number of attending surgeons performing each procedure was obtained from each individual institution. Outcomes were compared between 1-surgeon and 2-surgeon centers. After initial analysis, a separate cohort matched for demographic and severity of deformity was also analyzed. RESULTS: Patients in the 2S group were older (61.5 vs 54.2; p<0.01). Preoperative radiographs demonstrated that the 2S group had worsened deformity. X-ray parameters PI-LL (12.1 vs 21.7), SVA C7-S1 (54.2 vs 61.5), T1-PA (20.2 vs 25.1) and SRS-Schwab classification system were significantly different (p<0.05). There was no difference in the number of levels fused (11.2 vs 11.5 p=0.57). There was no significant difference in LOS (8.7 vs 8.9 days), OR time (445.9 vs 453.2 min) or EBL (2008 vs 1898 cc); (p>0.05). Patients in 2S group were more likely to obtain a 3 column osteotomy (3CO) 21.7% vs 59.6% (p=<0.001) and used less BMP 79.9% vs 15.6% (p<0.001). The 2S group had fewer intraoperative complications (1.3% vs 11.1%; p=0.006). But postoperative (6 weeks - 2 year) complications (4.8 vs 15.6%), implant related (4.2 vs 15.6%) and those requiring reoperation (5.3 vs 18.2%) were more frequent (p<0.002).After matching for PI-LL, SVA and 3CO, there was no difference in preoperative demographics. There was no difference in LOS (9.1 vs 10.1 days), OR time (467.8 vs 508.4 min) or EBL (3,045 vs 2,247 cc) p>0.05. 2SM group used less BMP (20.6% vs 84.8%; p=<0.001) and less intra operative complications (p=0.015). Postoperative (>6wks to 2 year) complications due to instrumentation failures/pseudoarthrosis were more frequent in 2SM group (p <0.01). CONCLUSIONS: Patients with ASD surgery performed by 2 surgeons were older with worse deformity. Both groups improved X-ray parameters and HRQOL but no difference was found in LOS, OR time or EBL even when matching cohorts for amount of deformity. 2S group had more 3COs, less BMP and had fewer intraoperative complications but more postoperative (>6 weeks to 2 years) complications that could be tied to low BMP use and/or fusion techniques. Overall it appears that for high complexity surgery, teams of multiple surgeons can reduce operative risk significantly

BACKGROUND CONTEXT: According to Dubousset's "conus of economy" theory, deterioration of sagittal alignment requires higher energy expenditure to maintain erect posture. Since the clinical impact of sagittal alignment is affected both by the severity of the deformity and a patient's inability to recruit compensatory mechanisms, it is important to investigate new parameters that reflect both disability level and compensatory mechanisms for all patients. This study investigates the clinical relevance of the global sagittal angle (GSA). PURPOSE: Provide a substantive measure of sagittal deformity which offers clinically significant information about disability for all patients in one easy to calculate metric. STUDY DESIGN/SETTING: Single center retrospective review. PATIENT SAMPLE: 143 Spinal deformity patients with full body sagittal X-ray imaging. OUTCOME MEASURES: Full body sagittal radiographic measures and health related quality of life measure (Oswestry Disability Index [ODI], Scoliosis Research Society 22r [SRS]). METHODS: Retrospective review of patients who underwent full body radiography and completed ODI and SRS-22r. GSA was defined as the angle subtended by a line from the midpoint of the femoral condyles to the center of C7, and a line from the midpoint between the femoral condyles to the posterior superior corner of the S1 sacral endplate (knee-C7 vs knee- S1). After evaluating the correlation of GSA/ODI with classic sagittal parameters, linear regression models were generated to investigate how ODI related to radiographic parameters (TPA, PT). TPA and PT's relation to GSA was then investigated. RESULTS: 143 patients (mean 44 years) were identified. GSA correlated significantly (ie, all with p<0.05) with ODI (r=0.517), SRS-22r (r= -0.543), PT(r=0.622), SVA(r=0.962), TPA (r=0.844) and lower limb alignment, knee flexion (r=0.793), ankle dorsiflexion (r=0.561) and pelvic posterior shift (0.870). Regression between ODI and classic parameters only retained GSA as independent predictor (r=0.517, r2=0.267, p<0.001). Analysis of standardized coefficients revealed that GSA increases when TPA increases (beta: 1.991) with concurrent decrease in PT (-1.323). These findings echoed those of ODI, which increased with increased TPA (beta: 1.038) and decreased PT (-0.696). CONCLUSIONS: GSA goes further than classic parameters and quantifies the clinical impact of all patients' compensation mechanisms in addition to their malalignment. Analyzing the relationship between GSA and PT revealed that compensation is the body's defense against malalignment, and patients who lack compensation have both higher GSA and higher ODI scores. However, this subset of patients possibly recruit knee flexion which further increases their global sagittal angle and disability. GSA is a significant and clinically relevant metric that quantifies both spinal deformity and disability even among those with alternative compensatory mechanisms

BACKGROUND CONTEXT: Osteoarthritis of the hip often co-exists with sagittal spinal deformity (SSD). Clinical manifestations overlap, and debate exists whether spinal deformity correction or total hip arthroplasty (THA) should be performed first. Hip extension and pelvic tilt are important compensatory mechanisms in SSD. In theory, spinal deformity correction may cause reciprocal changes in acetabular position. PURPOSE: To assess the changes in acetabular anteversion (AV) as a result of SSD correction, and to quantify the relationship between changes in AV and spino-pelvic parameters. STUDY DESIGN/SETTING: Retrospective analysis of a multicenter prospective database of adult spinal deformity patients. PATIENT SAMPLE: SSD patients who underwent surgical realignment were reviewed and included if they had a THA on baseline radiographs. Patients were excluded if they had large metal-on-metal bearings or revision THA in the study period. OUTCOME MEASURES: Radiographic anteversion of the acetabular component was measured pre- and postoperatively, and compared to the changes in spino-pelvic parameters as result of SSD correction. METHODS: Acetabular anteversion (AV) was calculated via the ellipse method (Lewinneck) on a standing PA 36" X-ray image with a wellcentered pelvis to avoid projectional measurement error. AV was measured preoperatively, and on the 6-week or 3-month postoperative X-ray study. Spino-pelvic parameters were measured including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), T1-pelvic angle (TPA), sagittal vertical axis (SVA), truncal tilt (T1SPi) and thoracic kyphosis (TK). Correlation coefficient and linear regression was performed to assess their relationships. RESULTS: Forty-one hips (33 patients) were identified. AV reduces after SSD correction by a mean 4.9degree (range +2 to -23). The change in AV was significantly correlated with the changes in PT (R=0.80), SS (R=-0.693), LL (R=-0.682), PI-LL (R=0.7237), SVA (R=0.561) and TPA (R=0.696). There was a weak correlation with TK and T1SPi. AV was decreased by 1degree for each of the following iatrogenic changes in spino-pelvic parameters (p<0001): 1.1degree PT, -1degree SS, 3.2degree LL, 1.67degree TPA and -11mm SVA. Thirty (73%) of acetabular components had a preoperative AVoutside the Lewinneck "safe zones." Twenty-eight of these 30 were excessively anteverted as a result of increased preoperative pelvic tilt. Postoperatively, 49% of patients still had an AV outside the safe zone, with 65% of these having residual pelvic tilt>20degree. Correction of SSD moved one acetabulum (2.4%) from a safe to unsafe AV. CONCLUSIONS: Correction of SSD results in reduction in AV, with potential implications for THA stability. SSD correction, when indicated, should be performed prior to THA to enable accurate acetabular positioning and minimize potential for dislocation. This study provides an algorithm for the sequence of THA and SSD correction in the patient with concominant pathologies

STUDY DESIGN: A multicenter, prospective review of surgical patients with adult spine deformity. OBJECTIVE: Assessment of the incidence, risk factor, and impact of radiographical and implant-related complications (RIC) on health-related quality of life measures. SUMMARY OF BACKGROUND DATA: This study provides assessment of the incidence of RIC in adult spinal deformity surgery and impact of these complications on need for reoperation. Risk factors for development of RIC are also assessed, as well as the impact of these complications on health-related quality of life (HRQOL) outcomes measures. METHODS: A multicenter, prospective database of surgical patients with adult spinal deformity was reviewed. All patients with complete 2-year follow-up were included. HRQOL was measured using the Oswestry Disability Index, General Health Survey (36-Item Short Form Health Survey [SF-36]), and Scoliosis Research Society-22 (SRS-22r) at baseline, 6 weeks, 1 year, and 2 years postoperatively. Univariate testing was performed as appropriate. Multivariate logistic regression modeling was used to determine independent predictors of RIC. Multivariate repeated-measures mixed models were used to examine HRQOL, accounting for confounders. RESULTS: A total of 245 patients met inclusion criteria. The incidence of RIC was 31.7% and 52.6% of those patients required reoperation. Rod breakage accounted for 47% of the implant-related complications, and proximal junctional kyphosis accounted for 54.5% of radiographical complications. Univariate analysis identified the following potential risk factors for RIC: weight, American Society of Anesthesiologists score, revision, stopping the fusion in the lower thoracic spine, worse SRS-Schwab classification modifiers (pelvic tilt++, pelvic incidence minus lumbar lordosis++, sagittal vertical axis++), higher T1 spinopelvic inclination, and higher T1 slope. Independent predictors of RIC as identified on multivariate logistic regression included American Society of Anesthesiologists (odds ratio: 1.75, P = 0.029) and sagittal vertical axis modifier ++ (odds ratio 3.43, P = 0.0001). The RIC and no RIC groups each experienced significant improvement over time, as measured on the Oswestry Disability Index (P = 0.0001), SF-36 (P = 0.0001), and SRS-22r (P = 0.0001). However, the rate of improvement over time was less for patients with RIC (SRS-22r P = 0.043, SF-36 P = 0.0001). CONCLUSION: This study identified that nearly one-third of patients undergoing adult spinal deformity surgery experienced a radiographical or implant-related complication, and that just more than one-half of these patients experiencing complication required a reoperation within 2 years of surgery. These complications significantly affected HRQOL measures. Baseline patient characteristics and parameters of the SRS-Schwab classification can be used to help identify those patients at greater risk. LEVEL OF EVIDENCE: 3.

BACKGROUND CONTEXT: Revision adult spinal deformity surgery (RASDS) is a particularly high-risk intervention. PURPOSE: To assess complication rates in RASDS by surgeon and hospital operative volume. STUDY DESIGN/ SETTING: Retrospective analysis of prospectively collected data. PATIENT SAMPLE: Nationwide Inpatient Sample (NIS) database (2001-2010), patients age >21 (International Classification of Diseases, Ninth Revision, ICD-9-CM) with spine arthrodesis for scoliosis. For longitudinal analysis, the 2008-2011 New York State Inpatient Database (NY SID) was queried. OUTCOME MEASURES: Complication rate after RASDS METHODS: Cases were identified as primary or revision surgery with or without osteotomy performed. Annual surgeon and hospital volumes were stratified into quartiles via identifier codes. Case complexity was determined using a novel operative complexity index, based on available NIS operative parameters: levels fused, approach, osteotomy and revision status.. The primary endpoint for was morbidity during the hospital stay. NY SID analysis allowed for identification of rate of reoperation for infection or pseudarthrosis/implant failure. One-way ANOVA was used to assess continuous measures, chi-square for categorical measures. RESULTS: Of 139,150 ASDS cases, 4,888 revision with hospital identifiers and 1,978 with surgeon identifiers were identified. Higher volume surgeons performed more revision cases and cases requiring osteotomy. With increasing hospital volume, complication rate for RASDS decreased (9.7% vs. 12.9% at highest- vs. lowest-volume centers, P< 0.001). The highest-volume surgeons showed significant decreases in the rate of major complications for RASDS (8.8% vs. 10.7% for lowest volume surgeons, P< 0.001). A similar trend was observed for ASDS cases requiring osteotomy. Multiple logistic regression analysis showed that the highest volume hospitals and surgeons showed a reduced odds ratio for all complications compared to lowest volume. For the NY SID, 528 RASDS cases indicated reoperation rates for infection and pseudoarthrosis/implant failure after RASDS were increased for the lowest volume hospitals and surgeons. CONCLUSION: Perioperative complication rate associated with RASDS is lower when patients are treated by high-volume surgeons at high-volume centers. As complex cases requiring osteotomy and combined approaches are more frequent at high-volume centers, an operative complexity index helps predict the likelihood of volume-dependent complication rates. Future inter-hospital and inter-surgeon comparisons should account for these case characteristics so that similar case complexity is compared in these analyses.