Adjacent facet joint degeneration after posterior single-level lumbar fusion: a mid-term follow-up

English Keywords:Lumbar  Spinal fusion  Adjacent segment degeneration  Facet joint  Follow-up study

English Abstract:

  【Abstract】 Objectives: To analyze the degenerative imaging features of adjacent facet joints after posterior single-level lumbar interbody fusion(PLIF), and to discuss the effect of PLIF on the degeneration of adjacent facet joints. Methods: From January 2005 to January 2014, 84 patients who underwent single-level PLIF (group A) or mere discectomy(group B) were collected． There were 44 patients with 140 adjacent facet joints in group A and 40 patients with 122 adjacent facet joints in group B． The degenerative imaging features and the incidence of adjacent facet joint were investigated on CT and MRI before and after surgery. The degenerative degree of facet joint was evaluated by Weishaupt grading system, analyzed by Cochran-Mantel-Haenszel statistics and compared within and between groups. Results: There was no statistical difference in sex ratio, age, follow-up time or surgical segment between the two groups(P>0.05)． The common radiographic appearances of facet joint degeneration were osteophyte formation, joint-space narrowing, subchondral erosion, subchondral cyst, joint malalignment, joint-space vacuum phenomenon, joint effusion, joint remodeling and joint fusion. The preoperative incidence of joint-space narrowing and subchondral erosion in group A was 52.9% and 31.4%, and increased to 75.7% and 62.1% postoperatively; that was 51.6% and 30.3% in group B preoperatively, and increased to 63.9% and 50% postoperatively. The incidence of joint-space narrowing and subchondral erosion between the two groups had no significant difference preoperatively(P>0.05), but it increased and had a significant difference between the two groups(P<0.05). According to Weishaupt grading system, among 140 joint facet joints in group A, 3 were of grade 0, 95 were of grade 1, 34 were of grade 2, 8 were of grade 3, with a degenerative incidence of 97.9% before surgery. While after surgery, 1 was of grade 0, 49 were of grade 1, 59 were of grade 2, 31 were of grade 3, with a degenerative incidence of 99.3%. Among 122 joint facet joints in group B, 4 were of grade 0, 82 were of grade 1, 30 were of grade 2, 6 were of grade 3, with a degenerative incidence of 96.7% before surgery. While after surgery, 2 were of grade 0, 60 were of grade 1, 39 were of grade 2, 21 were of grade 3, with a degenerative incidence of 98.4%. There was no significant difference of degenerative incidence before and after surgery in the two groups(P>0.05). Analyzed by Cochran-Mantel-Haenszel statistics, the degenerative degree of facet joint in the two groups aggravated after surgery, with a significant difference compared with that before surgery. The preoperative degenerative degree of facet joint had no significant difference between the two groups(P>0.05), while the postoperative degenerative degree had a significant difference(P<0.05), with more severe degenerative degree in patients of group A. Conclusions: The adjacent facet joint degeneration may accelerate after posterior single-level lumbar fusion, which most commonly shows as joint-space narrowing and subchondral erosion.