The necessity and risk factors of subsequent fusion after decompression alone for lumbar spinal stenosis with lumbar spondylolisthesis: 5 years follow-up in two different large populations.

BACKGROUND CONTEXT Decompression without fusion is one of common surgical treatments for patients with lumbar spinal stenosis (LSS) with spondylolisthesis, however, some patients will require a subsequent fusion at a later time. No studies have examined the rate and timing of decompression alone for spondylolisthesis in a large population with long term follow-up and it is unclear what the risk factors are for subsequent fusion. No studies have examined the rate, timing and risk factors of decompression alone for spondylolisthesis in large population with long term follow-up. PURPOSE The aim of this study is to examine the rate, timing and risk factors of subsequent fusion for patients after decompression alone for LSS with spondylolisthesis. STUDY DESIGN/SETTING Retrospective cohort study PATIENT SAMPLE Patients with spondylolisthesis followed more than 5 years after decompression alone at one or two levels for primary lumbar surgery were extracted from both public and private insurance resources in a nationwide insurer database. A total of 5,875 patients in the public insurance population (P1) and 1,456 patients in the private insurance population (P2) were included. OUTCOME MEASURES The rate of patients who needed subsequent fusion was examined at 1 year, 2 years and 5 years. The timing of the subsequent fusion was also investigated. Risk factors for subsequent fusion were evaluated by multivariate logistic regression controlling for age, gender, comorbidities and the presence or absence of claudication. METHODS Age, gender, type of spondylolisthesis (degenerative or isthmic) and comorbidities were collected in each population for demographics. Thirty comorbidities were identified using ICD-9 codes as previously described by Elixhauser et al. Risk factors for subsequent fusion were evaluated by multivariate logistic regression controlling for age, gender, comorbidities and the presence or absence of claudication. RESULTS The rates of patients who needed subsequent fusion were 1.9% at 1 year, 3.5% at 2 years and 6.7% at 5 years in Population 1, whereas they were 4.3% at 1 year, 8.9% at 2 years, 14.6% at 5 years in Population 2. The time to subsequent fusion was 730 (365-1234) days and 588 (300-998) days in P1 and P2, respectively. Age under 70 years, presence of claudication and rheumatoid arthritis (RA) / collagen vascular diseases (CVD) were common risk factors for subsequent fusion at 5 years in both populations. For patients with degenerative spondylolisthesis, RA/CVD was also a risk factor for subsequent fusion at 2 years. CONCLUSIONS Decompression alone, which is a less invasive procedure, demonstrated good outcomes with a low rate of subsequent fusion for LSS with spondylolisthesis. Age under 70 years, presence of claudication and RA/CVD were associated with a higher rate of subsequent fusion at 5 years, and for degenerative spondylolisthesis the presence of RA/CVD had an impact on the rate of subsequent fusion at 2 years. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.