Association between lumbosacral transitional vertebrae and adjacent segment disease after L4-5 lumbar interbody...

Adjacent segment disease (ASD) occurs after lumbar fusion surgery performed for degenerative lumbar spine disorders, requiring reoperation and impacting clinical outcomes. This study investigated the association between ASD after lumbar interbody fusion and lumbosacral transitional vertebrae (LSTV).

We retrospectively reviewed the perioperative data for 132 patients undergoing first-time L4-5 spinal interbody fusion without decompression outside the index level for degenerative spinal disease between April 2005 and December 2022. ASD was defined as a degenerative disease at adjacent levels requiring reoperation; LSTV was classified using the Castellvi classification (types II, III, and IV).

A total of 33 patients (26 %) had an LSTV (type IIa: n = 24, type IIb: n = 9). Postoperatively, 18 (13.6 %) patients developed ASD, of which six had LSTV (4 of type IIa, 2 of type IIb). Among the 114 non-ASD patients, 27 had an LSTV (20 of type IIa, 7 of type IIb). The difference regarding ASD occurrence between patients with and without LSTV was statistically insignificant (p = 0.27); however, the duration to reoperation for ASD was significantly shorter for Castellvi type IIb patients (mean = 21.5 months) than non-LSTV patients (mean = 90.9 months) (p = 0.036). The risk of new L3-4 slippage > 3 mm was significantly higher in the type IIb group (5 % of type IIa, 44 % of type IIb, and 7 % of non-LSTV; p = 0.001).

Although LSTV did not increase the overall risk of ASD, type IIb LSTV required reoperation earlier, necessitating diligent postoperative monitoring.