ABSTRACT
OBJECTIVE: A novel motion-preserving technique to directly repair pars defects. Moreover, the indications for repair are expanded to include those with disc disease and associated spondylolisthesis. SUMMARY OF BACKGROUND DATA: The challenge in treating pars defects has been that there are few techniques available to stabilize them adequately. Treatment has focused on fusion across the inter-space versus grafting and instrumentation of the defect itself. We hypothesize that direct repair of the defect favors maintenance of normal motion characteristics by preserving the functional unit of the disc. This paper describes a motion-preserving technique to repair bilateral pars defects and its early clinical outcomes. MATERIALS AND METHODS: A retrospective review of 20 patients with symptomatic bilateral pars defects treated with either intra-segmental or intra-intersegmental motion-preserving repair with two years of follow-up. Fifteen patients met the criteria for single level fixation. Five patients required additional fixation of flexible posterolateral fusion involving the inferior segment. Rh-BMP and autologous bone graft were placed within the defect. Plain film X-rays were used to determine stability, and thin-section CT was used to assess healing of the defect. RESULTS: The procedure arrested any further slippage in 100% of cases, with bony healing in 95% of cases as demonstrated by CT scan. Clinical outcomes for the entire series were: excellent n=14, good n=3, no significant help n=3. For all cases there was a 5% rate of non-union. CONCLUSION: Further study and development of the technique via biomechanical testing is ongoing; however, the initial results are encouraging. Bone formation appears to be linked to decreasing symptoms in patients with bilateral pars fractures who have failed conservative treatment.
