Combination of anorganic bovine-derived hydroxyapatite with binding peptide does not enhance bone healing in a critical-size defect in a rabbit model.

Anorganic bovine-derived hydroxyapatite (ABM) in combination with binding peptid (P-15) has demonstrated the capacity to improve the healing of periodontal defects. This study evaluated the benefit of ABM/P-15 to promote healing of cortical long bone defects in a rabbit model. A 5-mm segmental bone defect was created in the femur and fixed with a plate. There were two treatment groups: no implant (n = 12) and ABM/P-15 (n = 12). At 4, 8, and 12 weeks, healing of the defect was evaluated with radiographs and histomorphometric examination of the treated femora. After 4 weeks, radiographs showed bone formation without signs of complete consolidation in three of four animals in the control group and two of four ABM/P-15 treated animals. At the later course of the treatment, no radiologic difference was evident between the treatment groups. Histomorphometric evaluation revealed an area of 1.29 +/- 0.11 mm(2) and 0.97 +/- 0.21 mm(2) of newly produced bone in animals of the control group and ABM/P-15 group after 4 weeks. After 8 and 12 weeks, animals in the control group had an area of 2.44 +/- 0.62 mm(2) and 2.5 +/- 0.2 mm(2) of newly produced bone within the osteotomy gap compared to 1.6 +/- 0.65 mm(2) and 1.56 +/- 0.27 mm(2) in the ABM/P-15 group (p = 0.0004). An enhanced or accelerated ingrowth of bone, as reported in previous studies, was not observed. Our results imply that the ABM/P-15 is not a suitable graft for the treatment of critical-sized segmental defects in long bones.