Predisposing Characteristics of Adjacent Segment Disease After Lumbar Fusion

Vincent J. Alentado, BS; Daniel Lubelski, MD; Andrew T. Healy, MD; Robert D. Orr, MD; Michael P. Steinmetz, MD; Edward C. Benzel, MD; Thomas E. Mroz, MD

Disclosures

Spine. 2016;41(14):1167-1172. 

In This Article

Abstract and Introduction

Abstract

Study Design. Retrospective Review.

Objective. The aim of this study was to determine medical, radiographic, and surgical risk factors for the development of adjacent segment disease (ASD) after lumbar fusion.

Summary of Background Data. ASD is a recognized outcome of spinal fusion that leads to increased costs and debilitating symptoms for patients. However, a comprehensive understanding of risk factors for the development of this surgical outcome does not exist.

Methods. The medical records of patients who received their first lumbar fusion for any indication were retrospectively examined for preoperative medical comorbidities and medications, as well as surgical approach and perioperative complications. A blinded reviewer assessed radiographs for each patient to examine sagittal alignment after fusion. Multivariable logistic regression was used to model the risk of developing ASD on the basis of one or more predictors.

Results. A total of 137 patients fit the inclusion criteria; 9% required a follow-up operation for degeneration at segments adjacent to the fusion. The ASD group had a mean follow-up of 21.1 months prior to revision surgery and an overall follow-up of 41.0 months. The average follow-up in the control group was 14.0 months. Statistically significant independent predictors of developing ASD included antidepressant use [odds ratio (OR) = 5.4], diagnosis of degenerative scoliosis (OR = 34.2), fusion of L4-S1 (OR = 56.5), having no decompressions adjacent to the fusion, and low sacral slope (OR = 0.9). No patient who developed ASD received a decompression adjacent to the fusion such that an OR could not be generated for this independent predictor.

Conclusion. This study is the first to use a combination of medical, surgical, and postoperative sagittal balance as risk factors for the development of adjacent segment disease after lumbar fusion. The awareness of these risk factors may allow for better patient selection and surgical technique to decrease the probability of acquiring this adverse outcome.

Introduction

Adjacent segment disease (ASD) is a clinically relevant deterioration of adjacent vertebral segments after a fusion, and it is a well-recognized outcome after spinal fusion with a mean annual incidence of 2.9% after cervical fusion and 3.9% after lumbar fusion.[1,2] ASD occurs as a result of symptomatic degeneration of spinal levels immediately neighboring fused segments.[1] This deterioration theoretically arises from increased biomechanical stress adjacent to the fusion with physiologic loading.[3]

In a recent review, Radcliff et al[4] concluded that laminectomy adjacent to a fusion and sagittal imbalance in spinal deformity patients were the most reliable predictors of ASD. However, the authors also believed that substantial questions remained with regards to the nature and risk factors of ASD. Further confounding the evidence, there is no validated outcome measurement to diagnose or quantify ASD and previous studies have shown the presence of arthritic degeneration at levels adjacent to future fusion sites in preoperative patients.[4,5] This has caused substantial heterogeneity in the literature with regards to the quantity and quality of ASD. However, a recent study by Lee et al[6] recommends the use of reoperation rate as the criterion to define adjacent segment pathology because it is of more substantial value to the patient and surgeon.

Despite the relatively high incidence of ASD among patients who have undergone lumbar fusion, a comprehensive study that includes potential medical and surgical risk factors for the development of ASD does not exist. We hypothesized that the cause of ASD is multifactorial. In the present study, we examined demographic, medical, and perioperative surgical information, as well as pelvic sagittal balance and other radiographic measurements among patients who underwent lumbar fusion for all indications to identify risk factors for the development of postoperative ASD.

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