OBJECTIVETo compare the therapeutic effect of posterior lumbar interbody fusion by single and double B-Twin expandable spinal spacer with micro endoscopic discectomy (MED) for lumbar intervertebral disc protrusion accompanying degenerative instability.

METHODSFrom March 2006 to May 2008, 45 patients with lumbar intervertebral disc protrusion accompanying degenerative instability were admitted and managed with posterior lumbar interbody fusion by B-Twin expandable spinal spacer with MED. The patients were randomly assigned to treatment with single B-Twin (Single group, n = 24) or double B-Twin (Double group, n = 21). There were 16 males and 8 females, with an average age of 45.5 years (43 - 60 years) in Single group; 13 males and 8 females, with an average age of 43.7 years (44-61 years) in Double group. All the cases suffered from only one level disc protrusion, L(3-4) 2 cases, L(4-5) 29 cases and L₅-S₁ 14 cases. Clinical outcomes were evaluated with surgical time, blood loss, visual analogue scale (VAS) scores preoperatively, 1, 3, 6 month postoperatively. Oswestry disability questionnaire (ODI) of the preoperative, 1 month postoperative, and latest follow-up and the disk space heights.

RESULTSForty three patients were followed-up for 1 to 3 years after surgery. The mean surgical time of Double group was longer than Single group [(152 ± 32) min vs. (91 ± 15) min, P < 0.01]. The average blood loss in Double group was more than that in Single group [(146 ± 73) ml vs. (95 ± 58) ml, P < 0.01]. The mean time of hospital stay in Single group was similar to that in Double group [(11.0 ± 3.2) d vs. (10.9 ± 3.3) d, P > 0.05]. Both groups could keep the disk space heights till the last follow-up [(7.7 ± 1.8) mm vs. (8.5 ± 1.7) mm]. In the 6 months follow-up post operation, the VAS score decreased from (8.1 ± 1.8) to (2.0 ± 1.0) in Single group, and (8.1 ± 1.9) to (2.1 ± 1.0) in Double group. At the last follow-up, the ODI decreased from (36 ± 7)% to (10 ± 4)% in Single group and (37 ± 6)% to (9 ± 4)% in Double group, but there was no significant difference between the two groups (P > 0.05). All the cases achieved fusion at the last follow-up, 3 patients in Single group and 2 patients in Double group suffered from intractable low back pain. One of the fins broke in one patient without any uncomfortable feeling.

CONCLUSIONSCompared with the management of lumbar intervertebral disc protrusion accompanying degenerative instability by double B-Twin expandable spinal spacer with micro endoscopic discectomy, the single B-twin can get similar clinical outcomes, but shorter surgical time, less blood loss and less medical costs.