A preliminary study of the efficacy of beta tricalcium phosphate as a bone expander for instrumented posterolateral lumbar fusions

The associated morbidity of allograft(s) as bone graft expanders in spinal surgery has prompted the search for alternatives. The efficacy of Vitoss/Beta Tricalcium Phosphate (B-TCP: OrthoVita, Malvern PA, USA), an artificial bone substitute, combined with lamina autograft (50:50 mix) in 40 prospective posterolateral fusions utilizing pedicle/screw instrumentation was analyzed. Multilevel lumbar laminectomies (average 3.7 levels) were accompanied by 1 (27 patients) and 2 level (13 patients) fusions. Two neuroradiologists independently assessed fusion progression on dynamic x-rays and 2D-CT studies performed at 3, 6, and up to 12 months postoperatively. Outcomes were quantified utilizing Odom Criteria and Short-Form 36 (SF-36) questionnaires (preoperatively; and 3, 6, and 12 months postoperatively). By the sixth postoperative month, fusion was neuroradiologically confirmed on both dynamic x-rays and CT studies for 26 of 27 single level fusions (1 pseudarthrosis), and 11 of 13 two level fusions (L4-S1). Odom Criteria 3, 6, and 12 months postoperatively revealed continued improvement for all patients. SF-36 outcomes, however, revealed deterioration on 2 Health Scales (Role Physical, Role Emotional) 3 and 6 months post-operatively, and minimal to marked improvement on 6 Health Scales (PF, V, PF, V, SF, BP). Twelve months postoperatively improvement occurred on all 8 Health Scales, exceeding pre-operative baselines; minimal (RP, GH), mild (MH), moderate (PF, BP, V, SF), and marked improvement (RE). Although Vitoss/B-TCP and laminar autograft resulted in pseudarthrosis for 1 of 27 single level and 2 of 13 two level posterolateral instrumented lumbar fusions, only I of the latter patients required a secondary fusion.