Temporal Patterns of Risk Factors for Adjacent Segment Disease After Lumbar Fusion: 5 Years or More and up to 15 Years

초록

Background/Objectives: There are many concerns regarding adjacent segment disease after lumbar spinal fusion. However, there are few studies that analyze risk factors by classifying adjacent segment disease (ASD) by onset. This study aimed to investigate related factors according to the period of occurrence of ASD in mid- to long-term follow-up patients after lumbar spinal fusion. Methods: We analyzed 139 patients who underwent <= 3-segment lumbar fusion for degenerative disease with a minimum 5-year follow-up from a consecutive series of 457 patients. Risk factors for adjacent segment disease (ASD) and early ASD (E-ASD, occurring <= 5 years) were evaluated, including patient factors (age, sex, BMI), preoperative factors (diagnosis, Pfirrmann grade), surgical factors (fusion method, number of segments), and radiological parameters (lumbar lordosis, fused segment angle, PI-LL mismatch). Multivariable Cox proportional hazards modelling and Kaplan-Meier survival analysis were performed to identify independent risk factors. Results: A total of 28 patients underwent revision surgery for ASD. Among them, 14 patients developed E-ASD. In the analysis of risk factors for ASD, the fusion method, and the postoperative PI-LL were statistically significant (p = 0.003, HR = 4.670, and p = 0.008, HR = 3.102, respectively). Regarding E-ASD, the fusion method was statistically significant (p = 0.038, HR = 5.444). The cumulative survival rate of ASD was 93.7% at 5 years and 76.4% at 10 years. Conclusions: ASD risk factors vary temporally after fusion surgery. Early ASD is primarily associated with the PLIF technique, while long-term risk relates to both the fusion method and sagittal alignment. Surgical planning should consider both the fusion technique and sagittal balance optimization to minimize ASD risk.

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