77. The incidence of subsequent lumbar spine surgery after lumbar disc arthroplasty: a minimum two-year follow-up

Abstract

BACKGROUND CONTEXT Low back pain is one of the most common causes of disability in the United States. When conservative management fails, lumbar fusion in properly indicated patients has been considered the gold standard. However, lumbar disc arthroplasty is an alternative surgical option to spinal arthrodesis that may avoid the undesirable consequences of fusion including immobility and increased risk of adjacent segment degeneration. PURPOSE Surgical intervention rates following lumbar disc arthroplasty have been reported via the FDA investigational device exemption studies. However, these single institution studies and their findings may not be generalizable to the orthopedic community. We used the New York Statewide Planning and Research Cooperative System (SPARCS) database to identify the risk factors and incidence of subsequent lumbar spine surgery in patients undergoing primary lumbar disc arthroplasty. STUDY DESIGN/SETTING We analyzed the New York Statewide Planning and Research Cooperative System (SPARCS) inpatient database from 2005 to 2013 to retrospectively identify patients who underwent isolated lumbar disc arthroplasty. We used SAS version 9.4 to analyze de-identified data. Each patient had a unique patient identifier allowing for longitudinal follow-up. We followed patients for a minimum of two years. PATIENT SAMPLE We used the New York Statewide Planning and Research Cooperative System database to extract all index cases of lumbar disc arthroplasty (ICD9: 84.65) in New York State. A total of 1,372 patients underwent an inpatient lumbar disc arthroplasty procedure between January 2005 and September 2013. OUTCOME MEASURES The outcome of interest was subsequent lumbar re-operation. We further characterized re-operation by revision lumbar disc arthroplasty, anterior lumbar fusion, posterior lumbar fusion, lateral lumbar fusion, and laminectomy without fusion. METHODS International Classification of Diseases, Ninth Revision (ICD-9) codes were used to extract the index lumbar disc arthroplasty procedure (84.65) and to identify patient demographics and re-operation procedures. Patients were longitudinally followed until September 2015, corresponding to a minimum two-year follow-up, to determine the incidence of subsequent lumbar spine re-operation, which included revision lumbar disc arthroplasty, anterior lumbar fusion, posterior lumbar fusion, lateral lumbar fusion and laminectomy without fusion. Univariate and multivariate analyses were used to identify demographic risk factors for subsequent re-operation. RESULTS A total of 1,372 patients underwent an inpatient lumbar disc arthroplasty procedure between January 2005 and September 2013. Over the study duration, a decreasing number of inpatient lumbar disc arthroplasty procedures were performed in New York State (m=30 cases/year, p 40), sex, race, insurance, comorbidity score, tobacco use or lumbar diagnosis for the index lumbar disc arthroplasty procedure. CONCLUSIONS We identified a 17.6% incidence of subsequent lumbar spine surgery after inpatient lumbar disc arthroplasty, and an 8.8% re-operation rate at two years. Over the study duration, 14.2% underwent a subsequent lumbar fusion procedure. Diabetes mellitus was the only patient demographic factor to significantly influence the odds of lumbar spine re-operation. Inpatient lumbar disc arthroplasty procedures declined over the study duration in New York State. Further investigation is needed to evaluate if these findings correlate with the newest generation of lumbar disc arthroplasty designs. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.