OBJECTIVETo compare the clinical and radiologic effect in treating degenerative lumbar instability with single or double carbon fiber cages.

METHODSFrom November 2005 to October 2006, 97 patients of degenerative lumbar instability were followed up more than two years. All cases underwent pedicle screw fixation. Meanwhile, 41 of them, named group A, were applied with single carbon fiber cage, with 23 males and 18 females, aged for 35-70 years, including 38 cases with single vertebral instability and 3 cases with existing L4.5 and L5S1 intervertebral instability. The other 56 cases, named group B, were treated with two carbon fiber cages, with 32 males and 24 females, aged for 33-72 years, including 53 cases with single vertebral instability and 3 cases existing L4.5 and L5S1 intervertebral instability. The clinical effect, intervertebral fusion ratio and lost intervertebral height were compared between two groups.

RESULTSAll patients were followed up for 24-35 months, with an average of 28 months. Clinical effects (including symptom, sign, daily action and bladder function) were evaluated according to JOA 29 score. In group A: the JOA score improve from 10.11 +/- 2.40 preoperative to 24.88 +/- 2.30 at final follow-up, 25 cases obtained excellent results, 12 good, 4 fair; 39 cases obtained fusion with the fusion ratio of 95.1% (39/41). In group B: the JOA score from 9.62 +/- 2.60 preoperative to 25.19 +/- 2.40 at final follow-up, 37 cases obtained excellent results, 13 good, 6 fair; 53 cases obtained fusion with the fusion ratio of 94.6% (53/56). In the 7th day after operation, the average intervertebral height in group A was (11.2 +/- 1.2) mm,and that of group B was (11.3 +/- 1.4) mm. Two years later, the average intervertebral height in group A was (11.0 +/- 1.4) mm, while that of group B was (11.1 +/- 1.4) mm. There was no significant difference between two groups in clinical effect, intervertebral fusion ratio and lost intervertebral height (P > 0.05).

CONCLUSIONPedicle screw fixation and single or double carbon fiber cages in treating degenerative lumbar instability both can obtain satisfactory curative effect. Single carbon fiber cage has advantages such as minimally trauma, simply operation, retentively posterior column structure, cheaply price than double carbon fiber cages.