Porosity of β-Tricalcium Phosphate Affects the Results of Lumbar Posterolateral Fusion

Study Design: Clinical case-control and cross-sectional study. Objectives: To determine the influence of different porosities of beta-tricalcium phosphate (beta-TCP) as a bone substitute combined with local autograft bone obtained from decompression for lumbar posterolateral fusion (PLF). Summary of Background Data: Several reports have documented a high bone fusion rate using beta-TCP as a bone substitute. beta-TCP is increasingly used to supplement autograft in lumbar PLF, but the influence of different porosities of beta-TCP for the lumbar PLF has not been reported. Methods: Sixty patients who were diagnosed with lumbar degenerative diseases and treated with 2-level noninstrumented lumbar PLF were divided into 2 groups. Thirty patients were treated with 75% porous beta-TCP (beta-TCP-75 group), and the others were treated with 60% porous beta-TCP (beta-TCP-60 group). The clinical and radiographic results of each patient were assessed at 2 years postoperatively. Results: Both the groups showed a good improvement rate of the Japanese Orthopaedic Association score (JOA score) at 2 years postoperatively, but there were no significant differences between them. The beta-TCP-75 group represented a bone fusion rate of 70.0% (64.7% in men, 76.9% in women) and the beta-TCP-60 group was 93.3% (87.5% in men, 100.0% in women). The latter exhibited a significantly better bone fusion rate than the beta-TCP-75 group (P < 0.05). Conclusions: In lumbar PLF, 60% porous beta-TCP granules achieved a higher bone fusion rate than 75% porous beta-TCP granules.