Apatite‐Coated Collagen Sponge for the Delivery of Bone Morphogenetic Protein‐2 in Rabbit Posterolateral Lumbar Fusion

Abstract

Bone morphogenetic proteins (BMPs) need an effective delivery system for efficient bone regeneration. In this study, we evaluated the efficiency of an apatite-coated collagen sponge for the long-term delivery of BMP-2 in a rabbit model of lumbar posterolateral fusion. A total of 15 rabbits, divided into three groups, underwent posterolateral lumbar fusion. The first group (control group) received uncoated collagen sponges without BMP-2. The second group (uncoated group) received uncoated collagen sponges with BMP-2 (40 μg each side). The third group (apatite-coated group) received apatite-coated collagen sponges with the same level of BMPs (40 μg each side). All rabbits were euthanized 6 weeks after operation, and the fusion status was assessed by radiographic study, micro-CT, manual palpation, biomechanical study, and histological examination. Fusion rates as determined by radiographic study, micro-CT, and manual palpation showed that the apatite-coated group had a significantly higher rate of fusion than the control group (P = 0.024), while the uncoated group did not (P = 0.083). Biomechanical study showed significantly higher tensile strength in the apatite-coated group than the uncoated group (P = 0.032). Denser trabeculations were found in the apatite-coated group compared with the uncoated group. It is concluded that the use of apatite-coated collagen sponges for BMP-2 delivery enhanced bone regeneration.