One versus two BAK fusion cages in posterior lumbar interbody fusion to L4-L5 degenerative spondylolisthesis: a randomized, controlled prospective study in 25 patients with minimum two-year follow-up.

STUDY DESIGN

We accomplish posterior lumbar interbody fusion using posterolateral insertion of a single BAK fusion cage (Sulzer Spine-Tech, Minneapolis, MN) with unilateral facetectomy and hemilaminectomy.

OBJECTIVE

To subject a single BAK fusion cage inserted posterolaterally in posterior lumbar interbody fusion to a randomized, controlled trial to assess its clinical safety and efficacy.

SUMMARY OF BACKGROUND DATA

Routinely, two threaded cages in posterior lumbar interbody fusion have been recommended, which need bilateral facetectomy, extensive exposure, and retraction of cauda equina. Our biomechanical study showed that it is feasible to accomplish posterior lumbar interbody fusion using posterolateral insertion of a single threaded cage with unilateral facetectomy and hemilaminectomy.

MATERIALS AND METHODS

Patients with a primary diagnosis of L4-L5 degenerative spondylolisthesis accompanied by low back pain and unilateral leg pain, having failed conservative treatment, were considered for the procedure. Twenty-five patients were randomized into two groups of 13 and 12, respectively, using a random number table. Group 1 had a single BAK fusion cage inserted posterolaterally and oriented counter anterolaterally on the symptomatic side with unilateral facetectomy and hemilaminectomy. Group 2 had two BAK fusion cages inserted posteriorly with bilateral facetectomy and laminectomy.

RESULTS

A total of 12 of 13 patients in Group 1 and 11 of 12 patients in Group 2 achieved successful radiographic arthrodesis. Clinical results at 2 years for 7 of 13 patients in Group 1 were excellent, 4 of 13 were good, 2 of 13 fair, and no poor clinical results; 4 of 12 patients in Group 2 were excellent, 5 of 12 good, 1 of 12 fair, and 2 of 12 poor. Regarding complications, 2 of 12 in Group 2 had a postoperative motor and sensory deficit of the opposite adjacent (upper) nerve root.

CONCLUSION

Posterior lumbar interbody fusion using diagonal insertion of a single threaded cage by a posterior approach with unilateral facetectomy enables sufficient decompression and solid interbody arthrodesis to be achieved while maintaining a majority of the posterior elements. It is a clinically safe, easy, and economic technique to treat lumbar degenerative spondylolisthesis.