BACKGROUNDTopping-off surgery is a newly-developed surgical technique which combines rigid fusion with an interspinous process device in the adjacent segment to prevent adjacent segment degeneration. There are few reports on Topping-off surgery and its rationality and indications remains highly controversial. Our study aims to investigate the short-term and mid-term clinical results of Topping-off surgery in preventing adjacent segment degeneration when mild or moderate adjacent segment degeneration existed before surgery.

METHODSThe 25 cases that underwent L5-S1 posterior lumbar interbody fusion (PLIF) + L4-L5 interspinous process surgeries between April 2008 and March 2010 formed Topping-off group. The 42 cases undergoing L5-S1 PLIF surgery formed PLIF group. Both groups matched in gender, age, body mass index and Pfirrmann grading (4 to 6). The patients were evaluated with visual analogue scale (VAS) and Japanese orthopaedic association (JOA) scores before surgery and in the last follow-up. Modic changes of endplates were recorded.

RESULTSThe follow-up averaged 24.8 and 23.7 months. No symptomatic or radiological adjacent segment degeneration was observed. There was no significant difference in intraoperative blood loss or postoperative drainage. VAS and lumbar JOA scores improved significantly in both groups (t = 12.1 and 13.5, P < 0.05). Neither anterior nor posterior disc height was significantly changed. Segmental lordosis of L4-L5 and total lordosis were all increased significantly (Topping-off group: t = -2.30 and -2.24,P < 0.05; PLIF group: t = -2.76 and -1.83, P < 0.01). In the hyperextension and hyperflexion view, Topping-off group's range of motion (ROM) and olisthesis in the L4-L5 segment did not significantly change in flexion, but decreased in extension. In PLIF group, 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 flexion.

CONCLUSIONSCompared with single segment 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 ROM in extension and prevent excessive olisthesis of adjacent segment in both extension and flexion.