[The effect of Topping-off surgery on preventing adjacent segment degeneration, a retrospective study]

To investigate the early-middle stage clinical results of Topping-off surgery in preventing adjacent segment degeneration when mild or moderate adjacent segment degeneration exists before surgery.

All the cases that received L(5)-S(1) posterior lumbar interbody fusion (PLIF)+L(4)-L(5) interspinous process (ISP) surgeries between April 2008 and March 2010 (Topping-off group) were analyzed retrospectively. The cases received L(5)-S(1) PLIF surgery and whose intervertebral disc degeneration using modified Pfirrmann's grading system were grade 4 - 6 were analyzed retrospectively at the same time (PLIF group). Both groups matched in gender, age, body mass index and Pfirrmann's grading of disc. All the patients were evaluated with visual analogue scale (VAS) and Japanese orthopaedic association (JOA) scores before the surgery and in the last follow-up. The X-ray films before and after surgery were measured.

There were 25 patients in Topping-off group and 42 patients in PLIF group were included in the final analysis. The follow-up averaged 24.8 and 23.7 months. No symptomatic or radiological adjacent segment degeneration was observed. The average surgery time was (120 ± 24) min and (106 ± 21) min. There was no significant difference in the blood loss during surgery or post-operation drainage (P > 0.05). VAS and lumbar JOA score improved in both groups (P < 0.01). In the lateral view of lumbar spine, neither of anterior or posterior disk height was significantly changed (P > 0.05), segmental lordosis of L(4)-L(5), total lordosis were all increased (Topping-off group: t = -2.30 and -2.24, P < 0.05; PLIF group: t = -2.76 and -1.83, P < 0.05). In the hyperextension and hyperflexion view, Topping-off group's range of motion (ROM) and olisthesis in the L(4-5) segment did not significantly change in flexion (P > 0.05), but decreased in extension (t = 5.83 and 4.92, P < 0.01). In PLIF group, the ROM (t = -7.82 and -4.90, P < 0.01) and olisthesis (t = -15.67 and -18.58, P < 0.01) both significantly increased in extension and flection.

Compared with single segmental PLIF surgery, Topping-off surgery can achieve similar symptomatic improvement in cases with pre-existing mild or moderate adjacent segment degeneration, restrict the adjacent segment's range of motion in extension and prevent excessive olisthesis of adjacent segment in both extension and flexion. Topping-off surgery has a potential effect of preventing adjacent segmental degeneration.