What is the influence on adjacent segment lordosis after single-level PELD? – an observational study of radiological alignment changes

Study Design: Retrospective cohort study. Purpose To investigate the change in lumbar lordosis angle after single-level percutaneous endoscopic lumbar discectomy (PELD) and the difference in lordosis angle between L4/5 and L5/S1. Methods All patients were divided into L4/5 and L5/S1 groups according to surgical level. Lateral radiographs before and one year after surgery were collected to assess changes in lordotic angulation at all lumbar segments who underwent PELD at L4/5 and L5/S1. Results In total, 92 lumbar disc herniation patients (44 males and 48 females) treated with single-level PELD (52 at L4/5 and 40 at L5/S1) were enrolled. Fifty-two patients received the transforaminal approach (L4/5 21.7%, L5/S1 34.8%), and 40 patients received the interlaminar approach (L4/5 34.8%, L5/S1 8.7%). The L4/5 group had a mean 2° increase in operated segment lordosis (SL) (P < 0.001), the L5/L1 group had a mean − 1° change in the operated SL (P < 0.001), and the segmental lordosis gain was associated with lordosis changes at adjacent segments of -1° at L5/S1 (< 0.001) in the L4/5 group and 1° at L4/5 (< 0.001) in the L4/5 group. Modest gains in global lordosis (LL) angle were 2° (< 0.001) in the L4/5 group and 1° (< 0.001) in the L5/S1 group. The preoperative mean value of PI-LL was 15° in the L4/5 group and 18° in the L5/S1 group, and the postoperative mean value of PI-LL was 14° (P = 0.257) in the L4/5 group and 12° (P = 0.728) in the L5/S1 group. Conclusion There are subtle changes in lordosis at the operated segment and adjacent segments after single-level PELD surgery. The impact of surgery on LL is greater at the L4/5 segment than at the L5/S1 segment; additionally, the impact of surgery on lordosis is greater when the interlaminar approach is used than when the transforaminal approach is used.