Closed loop instrumentation of the lumbar spine.

A review of 40 consecutive nonreported multilevel lumbar fusions revealed an unacceptable pseudarthrosis rate of 32.5%. In an attempt to reduce this complication, a modification of segmental spinal instrumentation with use of a closed loop was performed on 50 consecutive patients treated by multilevel lumbar stabilizations. The primary diagnoses were degenerative disc and/or facet disease in 32, spondylolisthesis in 14, and pseudarthrosis in four. Thirty-eight percent had three or more levels to be fused. Thirty-two percent had had previous spinal surgery. Follow-up study was a minimum of one year. Seventy-three percent had posterior facet fusions. Twenty-seven percent had bilateral transverse process fusions. A pseudarthrosis occurred early in six patients, an incidence of 12%; three of the six occurred in patients with spondylolisthesis. Four of the six pseudarthroses occurred following posterior fusions. Subjective symptoms were improved in 80%. Working capacity was the same or better in 56%. Closed loop instrumentation (CLI) decreased the overall incidence of pseudarthrosis. When combined with transverse process fusion, CLI produced a slightly higher rate of success (90%) than did posterior fusion alone (87%) but did not reduce the incidence of pseudarthrosis in patients with spondylolisthesis.