Beta tricalcium phosphate: observation of use in 100 posterolateral lumbar instrumented fusions

Abstract

Background Beta tricalcium phosphate (B-TCP) is increasingly used to supplement lamina autograft to perform posterolateral lumbar-instrumented arthrodesis. Purpose To determine the radiographic arthrodesis and pseudarthrosis rates after multisegment lumbar laminectomies and one- or two-segment posterolateral instrumented fusion using lamina autograft and an artificial bone graft expander B-TCP (Vitoss; Orthovita, Malvern, PA, USA). Study design/setting To document radiographic arthrodesis/pseudarthrosis rates using lamina autograft and B-TCP. Patient sample One hundred patients with lumbar spinal stenosis underwent multisegment laminectomies (average 3.6 segments) and one- (78 patients) or two- (22 patients) segment posterolateral instrumented arthrodesis. Outcome measures Two-year postoperative outcomes were assessed using Short-Form 36 questionnaires. Methods The arthrodesis mass consisted of lamina autograft and B-TCP. Two independent neuroradiologists, using both dynamic X-rays and 2D-CT studies performed 3, 4.5, 6, and up to 12 months postoperatively, documented radiographic arthrodesis progression. Results One-segment arthrodesis was performed in 79 patients; 74 (93.7%) were radiographically fused “early” (6.5 postoperative months), 2 (2.5%) fused “late” (6.5–12 months), and 3 (3.8%) exhibited pseudarthrosis. Two-segment arthrodesis was performed in 21 patients; 14 (66.7%) radiographically fused “early,” 5 (23.8%) fused “late,” and 2 (9.5%) exhibited pseudarthrosis. Although chi-square analyses revealed a significant increase in the number of “late” radiographic fusions occurring for patients undergoing two-level arthrodesis, no significant difference in radiographic pseudarthrosis rates was noted between the two patient populations. In both groups, Short-Form 36 questionnaires revealed nearly comparable maximal improvement on seven of eight Health Scales by the second postoperative year. Conclusions At 6.5 months after multisegment lumbar laminectomies with posterolateral instrumented lumbar arthrodesis using lamina autograft/B-TCP, more one-segment (93.7%) versus two-segment (66.7%) radiographic arthrodesis occurred. By 1 year after operation, there was no significant difference in fusion rates between one- and two-segment radiographic arthrodeses.