Knodt rod distraction instrumentation in lumbosacral arthrodesis

Review of 40 patients undergoing lumbosacral fusions over a 4-year period was done to determine the value, efficiency, and safety of Knodt rod distraction instrumentation. The age range was 30-80 years. Mean age was 51 years. Follow-up was 1-4 years. Twenty patients underwent decompression and fusion for spinal stenosis, nine underwent spinal arthrodesis for instability, six underwent the same for spondylolisthesis, and five underwent fusions for other diagnoses. A posterior midline approach was used. Laminal hook sites were prepared, and care was taken to prevent dural compression or tenting. Balanced distraction was done to restore soft tissue tension and stability. No attempt was made to reduce deformity. A posterior and lateral mass fusion augmented with allograft bone was performed on all but three patients, in whom autogenous bone was used. The majority of patients were placed in a custom-molded lumbosacral orthosis for 3-6 months after operation. There were no neurologic complications, dural tears, or pseudomeningoceles. The first sacral laminas were instrumented in 22 patients. Nine of the 40 patients underwent rod removal. Reasons for removal were pain due to loosening in five patients and failure of fusion in two. On rod removal in two patients, no abnormality was found. Insertion within the sacral laminas did not lead to neurologic complications. The major problem appeared to be loosening, which necessitated rod removal in 12% of the patients. Knodt rod distraction instrumentation is a safe and effective method of internal fixation for lumbosacral fusions.