Faculty Bibliography

BACKGROUND: Anterior cervical discectomy and fusion (ACDF) performed as an outpatient has become increasingly common for treating cervical spine pathology. Few reports have attempted to assess readmissions following outpatient ACDF. This study was performed to address this issue using population-based databases. METHODS: The State Ambulatory Services Database (SASD) for New Jersey (NJ) from 2003-2012 was used for analysis. Patients receiving ACDF (defined as anterior cervical fusion (ICD-0 code=81.02) + excision of intervertebral disc (80.51)) were extracted; those with three or more levels fused (ICD-9 codes 81.63-81.64), cancer (ICD-9 codes 140-239), or trauma (ICD-9 codes=805.0-806.9) were excluded. A series of perioperative complications including durotomy, red blood cell transfusion, acute posthemorrhagic anemia, paraplegia (weakness), and mortality were examined. Propensity score matching (PSM) was used to adjust the analysis for patient age, race, sex, primary payer for care, and number of diagnoses. The NJ SASD defined readmission as admission to the same facility within seven days of initial discharge. RESULTS: Two thousand sixteen (2,016) patients were found, 1,528 of whom had readmission data. Of these 1,528 patients, 83 (5.4%) required readmission. PSM was performed prior to comparing readmission versus non-readmission. While there was no difference in perioperative complications between the two groups, the small sample size of the readmission cohort prevented this analysis from having sufficient power. No patient requiring readmission had an initial length of stay greater than one day. CONCLUSION: Based on a 10-year outpatient analysis, fewer than 6% of outpatient 1-2 level ACDFs require readmission. Future studies involving outpatients from several states will be necessary to determine whether these results of outpatient ACDF are applicable nationwide.

BACKGROUND: Anterior cervical discectomy and fusion (ACDF) is one of the most common operations utilized to address pathology of the cervical spine. Few reports have attempted to compare complications associated with inpatient versus outpatient ACDF. METHODS: The Nationwide Inpatient Sample (NIS) from 2001-2012 and the State Ambulatory Services Database (SASD) for New Jersey (NJ) from 2003-2012 were used for analysis. Patients receiving ACDF (defined as anterior cervical fusion (ICD-0 code=81.02) + excision of intervertebral disc (80.51)) were segmented into an inpatient group derived from the NIS, and an outpatient group derived from the NJ SASD. Patients receiving > 2 levels fused (ICD-9 codes 81.63-81.64), or surgery for cancer (ICD-9 codes 140-239), or trauma (ICD-9 codes=805.0-806.9) were excluded. Propensity score matching (PSM) was used to adjust the analysis for patient age, race, sex, primary payer for care, and number of medical diagnoses. RESULTS: Of the 94,492,438 inpatients comprising the NIS from 2001-2012, 257,398 received ACDF. Of the 4,194,207 outpatients comprising the NJ SASD, 2,016 received ACDF. PSM of 10,080 patients (all 2,016 SASD and 8,064 from NIS) was performed, and subsequent analysis revealed that durotomy (P=0.001;OR=0.81), paraplegia, postoperative infection, hematoma/seroma (OR=0.14), respiratory complications, acute posthemorrhagic anemia and red blood cell transfusion (all P<0.001) were less frequent in outpatient versus inpatient ACDF (p<0.05). These results were similar to an unmatched analysis involving all of the NIS patients. CONCLUSION: Accepting the limitations of the NIS and SASD (inability to distinguish between one and two-level fusions, no long-term follow-up, potential selection bias, disparities between inpatient and outpatient ACDF populations), these findings indicate that for 1-2 level ACDF, perioperative complications, including durotomy, paraplegia, hematoma, and acute posthemorrhagic anemia were more commonly reported following inpatient ACDF. Future studies involving outpatient analysis of several states will be necessary to determine whether these results of outpatient ACDF are applicable nationwide.

STUDY DESIGN: Retrospective review OBJECTIVE.: To evaluate preoperative variability in radiographic sagittal parameters in adult spinal deformity (ASD). SUMMARY OF BACKGROUND DATA: In ASD surgical planning, deformity magnitude is determined from pre-op radiographs. The are no studies evaluating the clinical relevance and timing to repeat radiographs during interval clinic visits and timing to repeat radiograph for preoperative planning. METHODS: 139 ASD patients with minimum two pre-operative full body spine x-rays were included. Cervical, thoracic, lumbar, pelvic, and hip/knee sagittal alignment parameters were analyzed using dedicated spine measurement software. Patients were grouped by time intervals between x-rays: A: /=21 weeks. Changes in sagittal parameters were correlated to age and deformity magnitude (T1 pelvic angle [TPA] or pelvic tilt [PT] >20 degrees ). RESULTS: The cohort had mean age 59 years, mean BMI 27, 30% males, 95 patients with no prior spine surgery and 44 patients at minimum nine months since prior spine surgery. There were 25 patients in Group A, 38 in B, and 71 in C. All radiographic measures showed good time-based consistency at intervals <21 weeks (Groups A and B). Group C had significant increases in PT (1.5 degrees ) and hip extension (2.1 degrees ) (p < 0.05). These changes were greater in Group C patients with previous surgery (PT 3.7 degrees ; p < .006, hip extension 3.2 degrees ; p < .025). Greater interval changes in parameters were also associated with higher magnitude of deformity and younger patient age. CONCLUSIONS: All sagittal radiographic parameters were statistically consistent at intervals < 21 weeks. In patients with >21 weeks between interval x-rays, change in PT was greater than the standard error of measurement for patients with prior surgery or severe deformity. Consideration should be made to obtain new x-rays for adult spinal deformity patients when the interval between clinical visits exceeds 5 months. LEVEL OF EVIDENCE: 4.

STUDY DESIGN: Retrospective cohortObjective. To investigate the cervical alignment necessary for the maintenance of horizontal gaze depends on underlying thoracolumbar alignment SUMMARY OF BACKGROUND DATA.: Cervical curvature (CC) is affected by thoracic and global alignment. Recent studies suggest large variability in normative CC ranging from lordotic to kyphotic alignment. No previous studies have assessed the effect of global spinal alignment on CC in maintenance of horizontal gaze. METHODS: Patients without previous history of spinal surgery and were able to maintain their horizontal gaze while undergoing full body imaging were included. Patients were stratified based on thoracic kyphosis (TK) into (<30, 30-40, 40-50 and >50) then by SRS-Schwab sagittal vertical axis (SVA) modifier into (posterior alignment SVA<0, aligned 0-50 and malaligned >50 mm). Cervical alignment was assessed among SVA grade in TK groups. Stepwise linear regression analysis was applied on random selection of 60% of the population. A simplified formula was developed and validated on the remaining 40%. RESULTS: In each TK group (n = 118, 137, 125, 197), lower cervical curvature (C2-C7) was significantly more lordotic by increased Schwab SVA grade. T1 slope and cervical SVA significantly increased with increased thoracolumbar (C7-S1) SVA. Upper cervical curvature (C0-C2) and mismatch between T1 slope and cervical curvature (T1-CL) were similar. Regression analysis revealed LL minus TK (LL-TK) as an independent predictor (r = 0.640, r2 = 0.410) with formula: CC = 10 - (LL-TK)/2. Validation revealed that the absolute difference between the predicted CC and the actual CC was 8.5 degrees . Moreover, 64.2% of patients had their predicted C2-C7 values were within 10 degrees of the actual CC. CONCLUSIONS: Cervical kyphosis may represent normal alignment in a significant number of patients. However, in patients with SVA >50 and greater thoracic curvatures, cervical lordosis is needed to maintain the gaze. Cervical alignment can be predicted from underlying TK and lumbar lordosis, which may be clinically relevant when considering correction for thoracolumbar or cervical deformityLevel of Evidence: 3.

Anterior cervical discectomy and fusion (ACDF) performed as an outpatient has become increasingly common for treating cervical spine pathology, largely due to its cost savings compared with inpatient ACDF. Nearly all outpatient ACDF patient reports have originated from single-center studies, with the procedure yet to be addressed via a meta-analysis of the peer-reviewed literature. The Entrez gateway of the PubMed database was used to conduct a comprehensive literature search for articles published in English up to 3/9/16. Data from studies meeting inclusion criteria (minimum of 25 patients, control group of inpatient ACDF patients, non-duplicative data source) was then categorized and assimilated for analysis. Seven studies met inclusion criteria, encompassing a 21-year timespan. Each provided Oxford Center for Evidence-Based Medicine Level 3 evidence. The studies yielded a total of 2448 outpatient ACDF patients; only 125 (5.1%) originated from studies published prior to 2011. Single-level surgery occurred in 63.8% of patients, with 0.5% extending beyond two-level fusions. The overall complication rate was 1.8% (mean follow-up of 141.2days); only 2% of patients required readmission. In conclusion, outpatient ACDF has become increasingly popular, with more than 95% of patients represented by studies published since 2011. Nearly two-thirds of outpatient ACDFs underwent single-level fusion, with virtually none undergoing 3+ level ACDF. Outpatient ACDF is safe, with a low readmission rate and complication rates comparable to those (2-5%) associated with inpatient ACDF. These findings support an argument for increasing ACDFs performed on an outpatient basis in appropriately selected patients.

STUDY DESIGN: A retrospective review of large, multicenter adult spinal deformity (ASD) database. OBJECTIVE: The aim of this study was to build a model based on baseline demographic, radiographic, and surgical factors that can predict clinically significant proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). SUMMARY OF BACKGROUND DATA: PJF and PJK are significant complications and it remains unclear what are the specific drivers behind the development of either. There exists no predictive model that could potentially aid in the clinical decision making for adult patients undergoing deformity correction. METHODS: Inclusion criteria: age >/=18 years, ASD, at least four levels fused. Variables included in the model were demographics, primary/revision, use of three-column osteotomy, upper-most instrumented vertebra (UIV)/lower-most instrumented vertebra (LIV) levels and UIV implant type (screw, hooks), number of levels fused, and baseline sagittal radiographs [pelvic tilt (PT), pelvic incidence and lumbar lordosis (PI-LL), thoracic kyphosis (TK), and sagittal vertical axis (SVA)]. PJK was defined as an increase from baseline of proximal junctional angle >/=20 degrees with concomitant deterioration of at least one SRS-Schwab sagittal modifier grade from 6 weeks postop. PJF was defined as requiring revision for PJK. An ensemble of decision trees were constructed using the C5.0 algorithm with five different bootstrapped models, and internally validated via a 70 : 30 data split for training and testing. Accuracy and the area under a receiver operator characteristic curve (AUC) were calculated. RESULTS: Five hundred ten patients were included, with 357 for model training and 153 as testing targets (PJF: 37, PJK: 102). The overall model accuracy was 86.3% with an AUC of 0.89 indicating a good model fit. The seven strongest (importance >/=0.95) predictors were age, LIV, pre-operative SVA, UIV implant type, UIV, pre-operative PT, and pre-operative PI-LL. CONCLUSION: A successful model (86% accuracy, 0.89 AUC) was built predicting either PJF or clinically significant PJK. This model can set the groundwork for preop point of care decision making, risk stratification, and need for prophylactic strategies for patients undergoing ASD surgery. LEVEL OF EVIDENCE: 3.

PURPOSE: In adult spinal deformity (ASD), patients increase pelvic tilt (PT) to maintain standing alignment. Previously, ASD patients with low PT and high disability were described. This study investigates this unusual population in terms of demographic, radiographic, and clinical features after three-column osteotomy (3CO). METHODS: In this multicenter retrospective study, ASD patients underwent single lumbar 3CO. Since PT is proportional to pelvic incidence (PI), the low PT group (LowPT) was defined as having a baseline (BL) PT/PI <25th percentile. HRQOL and full spine x-rays were analyzed at BL and 1 year. LowPT patients were compared to those with high PT/PI (HighPT) in a matched range of T1 pelvic angle. RESULTS: LowPT group had PT/PI <0.4 (n = 31). High disability was reported at baseline for both groups with significant improvement postoperatively, but without difference between groups. LowPT had significantly smaller lack lumbar lordosis but larger SVA, T1 spinopelvic inclination. Postoperatively, there were improvements in all sagittal modifiers except PT in LowPT. 33 % of LowPT had an increase in PT (>5 degrees ) postoperatively. This subset had more deformity at baseline, achieving good T1SPi postoperative correction but without achieving the SRS-Schwab target SVA at 1 year. CONCLUSION: LowPT group had high levels of disability. After 3CO surgery, low PT patients experience only partial improvements in sagittal vertical axis (SVA) and 33 % of the group increased their PT. Further work is necessary to determine optimal realignment approaches for this unusual set of patients. It is unclear if neuromuscular pathology plays a role in the setting of high SVA without pelvic retroversion.