In Vivo Evaluation of Porous Hydroxyapatite/Collagen Composite as a Carrier of OP-1 in a Rabbit PLF Model

Transplantation surgeries of autologous bone require a second surgery with inherent risks. To avoid these risks, we developed a multi porous implant of hydroxyapatite/collagen composite with desirable biophysical properties (flexibility, elasticity and compression resistance) for use with OP-1 as a graft implant. In this study, we tested the efficacy of this multi porous implant as OP-1 carrier using rabbit posterolateral lumbar fusion model (PLF). PLFs were performed in the following 4 groups of 8 New Zealand white rabbits each: autograft, HAp/Col alone, HAp/Col plus 0.3 mg OP-1, and HAp/Col plus 1.2 mg OP-1. At 5 weeks, fusion masses were analyzed by radiographic and biomechanical tests. Implants consisting of HAp/Col plus OP-1 were more effective than autologous bone in promoting spinal fusion. Low dose and high dose OP-1 were equally effective.