Faculty Bibliography

STUDY DESIGN/METHODS:Retrospective cohort study of prospectively collected data. OBJECTIVE:To examine the incidence of iatrogenic spinal cord injury following elective cervical spine surgery. METHODS:A retrospective multicenter case series study involving 21 high-volume surgical centers from the AOSpine North America Clinical Research Network was conducted. Medical records for 17 625 patients who received cervical spine surgery (levels from C2 to C7) between January 1, 2005, and December 31, 2011, were reviewed to identify occurrence of iatrogenic spinal cord injury. RESULTS:In total, 3 cases of iatrogenic spinal cord injury following cervical spine surgery were identified. Institutional incidence rates ranged from 0.0% to 0.24%. Of the 3 patients with quadriplegia, one underwent anterior-only surgery with 2-level cervical corpectomy, one underwent anterior surgery with corpectomy in addition to posterior surgery, and one underwent posterior decompression and fusion surgery alone. One patient had complete neurologic recovery, one partially recovered, and one did not recover motor function. CONCLUSION/CONCLUSIONS:Iatrogenic spinal cord injury following cervical spine surgery is a rare and devastating adverse event. No standard protocol exists that can guarantee prevention of this complication, and there is a lack of consensus regarding evaluation and treatment when it does occur. Emergent imaging with magnetic resonance imaging or computed tomography myelography to evaluate for compressive etiology or malpositioned instrumentation and avoidance of hypotension should be performed in cases of intraoperative and postoperative spinal cord injury.

BACKGROUND CONTEXT:T1 slope is a novel thoracic parameter used to assess cervical spine sagittal balance. Thoracic index (TI) parameters including T1 slope and cervical sagittal alignment parameters may play an important role in degenerative cervical spondylolisthesis (DCS). Current literature regarding the relationship between TI and cervical sagittal alignment parameters in patients with DCS is limited. PURPOSE:(1) To evaluate the T1 slope, cervical sagittal alignment, and thoracic inlet parameter in patients with DCS using kinematic magnetic resonance imaging (kMRI), and (2) to find a correlation between the T1 slope, TI, and other cervical sagittal parameters in patients with DCS. DESIGN/SETTING:Retrospective kMRI study, Level III. PATIENT SAMPLE:Fifty-two patients with DCS from 1,128 patients from a cervical kMRI database. OUTCOME MEASURES:T1 slope, C2-C7 angle, sagittal vertical axis C2-C7 (SVA C2-C7), cranial tilt, cervical tilt, neck tilt, and thoracic inlet angle (TIA). METHODS:Cervical spine kMRIs of 52 patients with DCS (mean age 51.7±standard deviation) were analyzed in neutral, flexion, and extension positions. Patients with DCS were divided into two groups: anterolisthesis (N=33) and retrolisthesis (N=19). Each listhesis group was subclassified into grade 1 (slip 2-3 mm) and grade 2 (slip>3 mm). RESULTS:Grade 2 retrolisthesis had the largest T1 slope followed by grade 1 retrolisthesis, grade 2 anterolisthesis, and grade 1 anterolisthesis. Significant differences were found between the anterolisthesis and the retrolisthesis groups in the neutral position (p=.025). The flexion position had the largest T1 slope and showed a significant difference with anterolisthesis in the neutral position (p=.041). Sagittal vertical axis C2-C7 showed strong correlation with cranial tilt in all DCS groups and all positions. CONCLUSIONS:In our study, T1 slope was larger in grade 2 DCS, and the retrolisthesis group had larger T1 slope than the anterolisthesis group. Presence of larger T1 slope was significantly correlated with larger cervical lordosis curvature. Furthermore, cranial tilt was strongly correlated with SVA C2-C7.

STUDY DESIGN/METHODS:Retrospective cohort study. OBJECTIVE:To examine the risk of undergoing another cervical spine surgery after single-level posterior cervical foraminotomy (PCF) and analyze the costs of such reoperations. METHODS:Using the PearlDiver database, we created database algorithms to identify cohorts of patients who underwent single-level PCF and also had various reoperations of interest, within 1, 2, and 4 years of follow-up. We also identified the per-patient average charge (PPAC) for each reoperation cohort. RESULTS:In the Medicare cohort, the incidence of any reoperation was 8.3%, 9.8%, and 10.5% within 1, 2, and 4 years of follow-up, respectively. The PPAC was $8520 for the initial PCF procedure. When a second cervical surgery was performed, the PPAC was $70 349 for anterior fusion, $15 760 for posterior decompression alone, and $77 976 for posterior decompression and fusion. In the UnitedHealth cohort, the incidence of any reoperation was 13.6%, 16.7%, and 17.0% within 1, 2, and 4 years of follow-up, respectively. CONCLUSIONS:The overall incidence of another cervical spine operation was slightly higher in the Medicare population to that in previous literature, but much higher in the UnitedHealth population. The most common reoperation after PCF varied between the Medicare and UnitedHealth datasets, and costs varied widely based on the procedure performed. This study provides pertinent information that surgeons can use to discuss the risk of reoperation with their patients.

BACKGROUND:As concerns regarding health-care expenditure in the U.S. remain at the national forefront, outpatient arthroplasty is an appealing option for carefully selected patient populations. The purpose of this study was to determine the nationwide trends and complication rates associated with outpatient total knee arthroplasty (TKA) in comparison with standard inpatient TKA. METHODS:We performed a retrospective review of the Humana subset of the PearlDiver Patient Record Database to identify patients who had undergone TKA (Current Procedural Terminology [CPT] code 27447) as either outpatients or inpatients from 2007 to 2015. The incidence of perioperative medical and surgical complications was determined by querying for relevant International Classification of Diseases, Ninth Revision (ICD-9) and CPT codes. Multivariate logistic regression analysis adjusted for age, sex, and Charlson Comorbidity Index (CCI) was used to calculate odds ratios (ORs) of complications among outpatients relative to inpatients treated with TKA. RESULTS:Cohorts of 4,391 patients who underwent outpatient TKA and 128,951 patients who underwent inpatient TKA were identified. The median age was in the 70 to 74-year age group in both cohorts. The incidence of outpatient TKA increased across the study period (R = 0.60, p = 0.015). After adjustment for age, sex, and CCI, outpatient TKAs were found to more likely be followed by tibial and/or femoral component revision due to a noninfectious cause (OR = 1.22, 95% confidence interval [CI] = 1.01 to 1.47; p = 0.039), explantation of the prosthesis (OR = 1.35, CI = 1.07 to 1.72; p = 0.013), irrigation and debridement (OR = 1.50, CI = 1.28 to 1.77; p < 0.001), and stiffness requiring manipulation under anesthesia (OR = 1.28, CI = 1.17 to 1.40; p < 0.001) within 1 year. Outpatient TKA was also more frequently associated with postoperative deep vein thrombosis (OR = 1.42, CI = 1.25 to 1.63; p < 0.001) and acute renal failure (OR = 1.13, CI = 1.01 to 1.25; p = 0.026). CONCLUSIONS:With the potential to minimize arthroplasty costs among healthy patients, outpatient TKA is an increasingly popular option. Nationwide data from a private insurance database demonstrated a higher risk of perioperative surgical and medical complications including component failure, surgical site infection, knee stiffness, and deep vein thrombosis. LEVEL OF EVIDENCE/METHODS:Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

PURPOSE/OBJECTIVE:The aim of this study was to determine whether having an existing psychiatric disorder is a risk factor for developing post-operative infection following anterior cervical discectomy with fusion (ACDF) and posterior cervical fusion (PCF). RESULTS:A total of 34,007 patients within Humana database was included in this study. Patients with mental disorders had post-operative infection rates of 3.2% and 4.4% within 1 and 3months, compared to 2.5% and 3.5% in patients without a psychiatric disorder (p < 0.05). CONCLUSIONS:Patients with mental disorders had significantly higher rates of post-operative infection compared to patients who were never diagnosed with a psychiatric disorder.

PURPOSE/OBJECTIVE:To investigate the relationship between the facet fluid sign (FFS) and kinematics of affected lumbar segment in patients with low-grade, single-level lumbar degenerative spondylolisthesis using kinematic magnetic resonance imaging (kMRI).Materials and methods Ninety-two patients diagnosed with low-grade (Grade 1 or 2), single level lumbar degenerative spondylolisthesis L3 to S1. Angular and translational motion, whole lumbar motion, slip percentage, and facet angle were measured. Disc degeneration and degrees of osteoarthritis were graded, facet effusion was evaluated and classified as Positive or Negative FFS (PosFFS or NegFFS).Results There were significant differences in the facet degeneration, translational motion, percentage of total angular motion, and flexion-extension slip difference between the PosFFS and NegFFS group. 28.3% of the patients in PosFFS group had anterolisthesis in flexion, but not extension.There was a significant difference in the incidence of FFS between the dynamic and static spondylolisthesis (75% vs 35%, p < 0.001). If FFS was present on kMRI, a positive predictive value for dynamic spondylolisthesis was 75.6%. with the sensitivity and specificity of 0.75 and 0.65 for posFFS to diagnose dynamic DS. The likelihood ratio for dynamic slips in the presence of FFS was 2.1, and the likelihood ratio for static slips in the presence of FFS was 1.1.Conclusion Facet fluid sign was present in weight-bearing neutral position, and the presence of FFS in kMRI increased the probability of having dynamic spondylolisthesis.

STUDY DESIGN/METHODS:Retrospective database review. OBJECTIVES/OBJECTIVE:After the Food and Drug Administration approved bone morphogenetic protein-2 (BMP) in 2002, BMP was used off-label in the cervical spine to increase bone growth and bony fusion. Since then, concerns have been raised regarding complication rates and safety. This study was conducted to examine the use of BMP in anterior cervical discectomy and fusion (ACDF) in the Medicare population and to determine risk of complications and associated costs within 90 days of surgery. METHODS:Patients who underwent ACDF were identified using Current Procedural Terminology (CPT) and International Classification of Diseases, Ninth Revision Procedure codes (ICD9-P). Complications were identified using ICD9 diagnostic codes. Charges were calculated as amount billed, and reimbursements were calculated as amounts paid by Medicare. Data for these analyses came from a nationwide claims database. RESULTS:A total of 215 047 patients were identified who had ACDF from 2005 to 2011. For the majority of the procedures (89.0%), BMP was not used. BMP use rose from 11.84% in 2005 to a peak of 16.73% in 2007 before decreasing to 12.01% in 2011. BMP was used 16% more in women than men. BMP use was the highest in the West (13.6%) followed by Midwest (11.8%), South (10.6%), and Northeast (7.5%). There was a higher overall complication rate in the BMP group (2.1%) compared with the non-BMP group (1.9%) (odds ratio [OR] = 1.11, 95% CI = 1.01-1.22). The BMP group also had a higher rate of wound complications (0.98% vs 0.76%, OR = 1.29, 95% CI = 1.12-1.48). In this study population, there was no difference in dysphagia/hoarseness, neurologic, medical, or other complications. During the 90-day perioperative period, BMP surgeries were charged at 17.6% higher than non-BMP surgeries. CONCLUSIONS:The use of BMP in ACDF in the Medicare population has decreased since a peak in 2007. The rate of wound and overall complications for BMP use with ACDF was higher than without. Our results regarding dysphagia/hoarseness did not show a statistically meaningful difference, which is in contrast with many other studies. Charges associated with BMP use were higher during the 90-day perioperative period.

STUDY DESIGN/METHODS:Retrospective study. OBJECTIVES/OBJECTIVE:Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been widely used in spinal fusion surgery, but there is little information on rhBMP-2 utilization in single-level posterior lumbar interbody fusion (PLIF). The purpose of our study was to evaluate the trends and demographics of rhBMP-2 utilization in single-level PLIF. METHODS:Patients who underwent single-level PLIF from 2005 to 2011 were identified by searching ICD-9 diagnosis and procedure codes in the PearlDiver Patient Records Database, a national database of orthopedic insurance records. The year of procedure, age, gender, and region of the United States were recorded for each patient. Results were reported for each variable as the incidence of procedures identified per 100 000 patients searched in the database. RESULTS:< .01) compared to single-level PLIF with rhBMP-2 (0.21 cases per 100 000 patients). The average rate of single-level PLIF with rhBMP-2 utilization was the highest in West (30.1%), followed by Midwest (26.9%), South (20.5%), and Northeast (17.8%). The highest incidence of single-level PLIF with rhBMP-2 was observed in the age group <65 years (0.3 per 100 000 patients). CONCLUSIONS:To our knowledge, this is the first study to report on the demographics associated with rhBMP-2 use in single-level PLIF. There was a 3-fold increase in the rate of PLIF without rhBMP-2 compared to PLIF with rhBMP-2, with both procedures being mainly done in patients less than 65 years of age.

STUDY DESIGN/METHODS:A retrospective database study. OBJECTIVE:The goal of this study was to (1) evaluate the trends in the use of electromyography (EMG) for instrumented posterolateral lumbar fusions (PLFs) in the United States and (2) assess the risk of neurological injury following PLFs with and without EMG. SUMMARY OF BACKGROUND DATA/BACKGROUND:Neurologic injuries from iatrogenic pedicle wall breaches during screw placement are known complications of PLFs. The routine use of intraoperative neuromonitoring (ION) such as EMG during PLF to improve the accuracy and safety of pedicle screw implantation remains controversial. METHODS:A retrospective review was performed using the PearlDiver Database to identify patients who had PLF surgery with and without EMG for lumbar disorders from years 2007 to 2015. Patients undergoing concomitant interbody fusions or spinal deformity surgery were excluded. Demographic trends and risk of neurological injuries were assessed. RESULTS:During the study period, 2007 to 2015, 9957 patients underwent PLFs. Overall, EMG was used in 2495 (25.1%) of these patients. There was a steady increase in the use of EMG from 14.9% in 2007 to 28.7% in 2009, followed by a steady decrease to 21.9% in 2015 (P < 0.0001). The risk of postoperative neurological injuries following PLFs was 1.35% (134/9957) with a risk of 1.36% (34/2495) with EMG and 1.34% (100/7462) without EMG (P = 0.932). EMG is used most commonly for PLFs in the Southern part of the United States. CONCLUSION/CONCLUSIONS:In this retrospective national database review, we found that there was a steady increase in the routine use of EMG for PLFs followed by a steady decline. Regional differences were observed in the utility of EMG for PLFs. The risk of neurological complications following PLF in the absence of spinal deformity is low and the routine use of EMG for PLF may not decrease the risk. LEVEL OF EVIDENCE/METHODS:4.