Effect of segmental lordosis on early-onset adjacent-segment disease after posterior lumbar interbody fusion

Abstract

OBJECTIVE Although several reports have described adjacent-segment disease (ASD) after posterior lumbar interbody fusion (PLIF), there have been only a few reports focusing on early-onset ASD occurring within 3 years after primary PLIF. The purpose of this study was to investigate the prevalence and postoperative pathologies of early-onset ASD and its relation with radiological parameters such as segmental lordosis (SL). METHODS The authors reviewed a total of 256 patients who underwent single-segment PLIF at L4–5 for degenerative lumbar spondylolisthesis (DLS) and were followed up for at least 5 years. The definition of ASD was a symptomatic condition requiring an additional operation at the adjacent fusion segment in patients who had undergone PLIF. ASD occurring within 3 years after primary PLIF was categorized as early-onset ASD. As a control group, 54 age- and sex-matched patients who had not suffered from ASD for more than 10 years were selected from this series. RESULTS There were 42 patients with ASD at the final follow-up. ASD prevalence rates at 3, 5, and 10 years postoperatively and at the final follow-up were 5.0%, 8.2%, 14.1%, and 16.4%, respectively. With respect to ASD pathologies, lumbar disc herniation (LDH) was significantly more common in early-onset ASD, while lumbar spinal stenosis and DLS occurred more frequently in late-onset ASD. Significant differences were detected in the overall postoperative range of motion (ROM) and in the changes in ROM (ΔROM) at L3–4 (the cranial adjacent fusion segment) and changes in SL (ΔSL) at L4–5 (the fused segment), while there were no significant differences in other pre- and postoperative parameters. In stepwise logistic regression analysis, ΔSL was identified as an independent variable (p = 0.008) that demonstrated significant differences, especially in early-onset ASD (control 1.1° vs overall ASD −2.4°, p = 0.002; control 1.1° vs early-onset ASD −6.6°, p = 0.00004). CONCLUSIONS The study results indicated that LDH was significantly more common as a pathology in early-onset ASD and that ΔSL was a major risk factor for ASD, especially early-onset ASD.