Semirigid instrumentation in the management of lumbar spinal conditions combined with circumferential fusion. A multicenter study.

STUDY
DESIGN: Patients with the diagnosis of degenerative disc conditions or spondylolisthesis undergoing circumferential fusion with posterior pedicle screw fixation using a semirigid rod were reviewed.
OBJECTIVES: To determine the effectiveness of this approach in achieving a spinal fusion and satisfactory clinical outcome, and to determine the complications associated with the procedure. SUMMARY OF BACKGROUND DATA: The use of instrumentation to stabilize the lumbar motion segments and thereby enhance the fusion rate has been proposed in a number of studies. Semirigid fixation was believed to be effective in achieving these objectives without concern for stress-shielding, which was suggested by some authors using rigid fixation systems.
METHODS: Patients who required spinal fusion with anterior and posterior approaches because of specific lumbar pathology or previous surgeries were selected. The surgery consisted of an anterior interbody fusion using allograft, followed by a posterolateral fusion and pedicle screw fixation. Fusion was determined by continuity of trabecular bridging, and outcomes were determined by pain reduction and return to previous levels of activity. Fusion was considered solid if the two posterolateral areas were fused (Zones one and two), if the anterior interbody area was fused (Zone three), or if all three zones were fused. Complications were documented during and after surgery.
RESULTS: Sixty-two percent of patients had previous surgery with 25% of these patients having a diagnosis of pseudarthrosis. Fifty-five percent of patients had two or more levels fused, and 43% were heavy smokers. Ninety-seven percent of patients had successful fusions. Pain was significantly reduced on a pain analogue scale from 7.1 to 2.1 in the back and from 5.8 to 1.5 in the leg (p < 0.006 and 0.0001, respectively). Fifty-nine percent of patients returned to their previous level of activity, and 18% returned to lighter work or job retraining, for a total of 77% returning to the same or lighter levels of activity. Complications included metal failure, 4.9%; neurologic deficit, 1.2%; deep infection, 1.2%; deep venous thrombosis, 4.9%; and vascular injury, 2.4%. Fatal pulmonary embolus occurred in one patient.
CONCLUSION: This technique produces a satisfactory fusion rate (97%) and a good clinical outcome based on pain reduction and return to a satisfactory level of activity (77%). It is associated with few, but significant, complications that compare well with other reported series in a difficult group of patients. This procedure should be reserved for patients who are considered to be at high risk for not achieving spinal fusion.