Product Notes and Case Studies

Risk factors for adjacent segment disease after lumbar fusion

Choon Sung Lee · Chang Ju Hwang
Sung-Woo Lee · Young-Joon Ahn · Yung-Tae Kim
Dong-Ho Lee · Mi Young Lee
Received: 24 July 2008 / Revised: 19 April 2009 / Accepted: 1 June 2009
© Springer-Verlag 2009

Abstract

The incidence of adjacent segment problems after lumbar fusion has been found to vary, and risk factors for these problems have not been precisely verified, especially based on structural changes determined by magnetic resonance imaging. The purpose of this retrospective clinical study was to describe the incidence and clinical features of adjacent segment disease (ASD) after lumbar fusion and to determine its risk factors. We assessed the incidence of ASD in patients who underwent lumbar or lumbosacral fusions for degenerative conditions between August 1995 and March 2006 with at least a 1-year followup. Patients less than 35 years of age at the index spinal fusion, patients with uninstrumented fusion, and patients who had not achieved successful union were excluded. Of the 1069 patients who underwent fusions, 28 (2.62%) needed secondary operations because of ASD and were included in this study. In order to identify the risk factors, we matched a disease group and a control group. The disease group consisted of 26 of the 28 patients with ASD, excluding the 2 patients for whom we did not have initial MRI data. Each patient in the disease group was matched by age, sex, fusion level and follow-up period with a control patient. The assumed risk factors included disc and facet degeneration, instability, listhesis, rotational deformity, and disc wedging. The mean age of the 28 patients with ASD requiring surgical treatment was 58.4 years, which did not differ significantly from that of the population in which ASD did not develop (58.2 years, p = 0.894). Of the 21 patients who underwent floating fusion, only 1 developed distal ASD. Facet degeneration was a significant risk factor (p\0.01) on logistic regression analysis. The incidence of distal ASD was much lower than that of proximal ASD. Pre-existing facet degeneration may be associated with a high risk of adjacent segment problems following lumbar fusion procedures.

Keywords

Adjacent segment · Degeneration · Lumbar fusion · Risk factor

Introduction

Although efforts to preserve segmental motion during spinal surgery are now increasing, spinal fusion remains a standard method of surgical treatment for deformity, trauma, and degenerative disorders. Fusion and clinical success rates have increased due to improvements in instrumentation and bone graft material. In contrast, numerous complications and problems of fusion surgery have been reported, with adjacent segment disease (ASD) being one of the most important. Abnormal loading and increased mobility in adjacent segments may explain the development of ASD, but it is still unclear whether it is caused by fusion sequelae or is the result of natural degeneration [3, 6, 11, 15, 18, 24]. There have also been controversies about the exact incidence of ASD and its risk...