Adjacent Segment Pathology following Posterior Lumbar Interbody Fusion for Lumbar Degenerative Spondylolisthesis: A Comparison between Minimally Invasive and Conventional Open Approach.

ABSTRACT BACKGROUND CONTEXT The minimally invasive (MI) approach in posterior lumbar interbody fusion (PLIF) minimizes the muscle-stripping posterior exposure of the lumbar spine; therefore, it is hypothesized that such benefits would reduce adjacent segment pathology (ASP) development. OBJECTIVE This study aimed to estimate the incidence of ASP following MI-PLIF. STUDY DESIGN Retrospective study. PATIENT SAMPLE A total of 100 patients who had undergone single-level PLIF at the L4/5 level for lumbar degenerative spondylolisthesis were retrospectively studied (MI-PLIF group: 68 patients; conventional open PLIF [O-PLIF] group; 32 patients; average follow-up period: 100.5 months). OUTCOME MEASURES Incidence of ASP. METHODS Patients were considered to have operative ASP (OASP) if adjacent segments manifested degenerative lesions that caused clinically significant symptoms requiring surgery. Survival curves were estimated for each group using the Kaplan–Meier method. The study was not externally funded. The authors have no conflicts of interest to declare. RESULTS Four (5.9%) of the 68 patients in the MI-PLIF group and 6 (18.8%) of the 32 patients in the O-PLIF group experienced OASP during the follow-up period. Kaplan–Meier analysis predicted a disease-free OASP survival rate of 98.5% (95% confidence interval [CI], 95.5%–100%) in the MI-PLIF group and 90.6% (95% CI, 81.1%–100%) in the O-PLIF group at 5 years, and 93.7% (95% CI, 86.8%–100%) in the MI-PLIF group and 71.8% (95% CI, 52.9%–97.5%) in the O-PLIF group at 10 years. MI-PLIF achieved a significantly higher survival rate in OASP than did O-PLIF (P = 0.04). O-PLIF was associated with a 3.97 times higher risk (odds ratio 3.97, 95% CI, 1.02–15.48; P = 0.04) of developing OASP in our cohort. CONCLUSIONS Following MI-PLIF, the rate of OASP was predicted to be 1.5% at 5 years and 6.3% at 10 years. MI-PLIF had a lower incidence of OASP and more favorable clinical outcomes than did O-PLIF.