Yasuhiro Take1, Tatsuo Mae2, Minoru Yoneda3, Shin-Ichi Yamada4, Yuta Tachibana5, Shigeto Nakagawa6, Ken Nakata7, Hideki Yoshikawa2. 1. Department of Orthopaedics, Daini Osaka Police Hospital, Japan. Electronic address: yasuhiro-take@umin.ac.jp. 2. Department of Orthopaedics, Osaka University Graduate School of Medicine, Japan. 3. Department of Orthopaedics, Nippon Medical School, Japan. 4. Department of Orthopaedics, JCHO Hoshigaoka Medical Center, Japan. 5. Department of Orthopaedic Surgery, Osaka Rosai Hospital, Japan. 6. Sports Orthopaedic Center, Yukioka Hospital, Japan. 7. Medicine for Sports and Performing Arts, Department of Health and Sport Sciences, Osaka University Graduate School of Medicine, Japan.
Abstract
BACKGROUND: Bone substitutes are widely accepted for various clinical applications. However, the usage is predominantly intraosseous implantation, whereas extraosseous on-lay grafting is rare and lacks scientific evidence. The purpose of this study is to elucidate whether osteoconduction occurs in on-lay grafted bone substitute. METHODS: Custom-made interconnected porous calcium hydroxyapatite ceramic (IPCHA) was on-lay grafted with screw or anchor fixation (S- and A-groups, respectively) at the anterior aspect of the femur of skeletally mature Japanese white rabbits. At 3, 6 and 12 weeks postoperatively, 4 samples for each time point and each group were evaluated by microfocus computed tomography (micro-CT) and histology. RESULTS: Volume-rendered three-dimensional micro-CT images showed a high-density calcified area infiltrating IPCHA from the femoral cortex as of 6 weeks. When quantified, the calcified volume per unit volume first showed no difference between the two groups at 3 weeks but increased over time, and became significantly greater in the S-group than in the A-group (p = 0.012 and 0.004 at 6 and 12 weeks, respectively). Histologically, IPCHA pores were first occupied by fibrous tissue at 3 weeks; then, the pores adjacent to the femoral cortex were gradually replaced by bony tissue as of 6 weeks for both fixations. CONCLUSIONS: IPCHA allowed new bone formation inside the material even though it was implanted in an on-lay fashion on the cortical bone. Our results suggested that on-lay grafted IPCHA exerted its osteoconductivity well, with more new bone forming in screw-fixated samples than in anchor-fixated samples.
BACKGROUND: Bone substitutes are widely accepted for various clinical applications. However, the usage is predominantly intraosseous implantation, whereas extraosseous on-lay grafting is rare and lacks scientific evidence. The purpose of this study is to elucidate whether osteoconduction occurs in on-lay grafted bone substitute. METHODS: Custom-made interconnected porous calcium hydroxyapatite ceramic (IPCHA) was on-lay grafted with screw or anchor fixation (S- and A-groups, respectively) at the anterior aspect of the femur of skeletally mature Japanese white rabbits. At 3, 6 and 12 weeks postoperatively, 4 samples for each time point and each group were evaluated by microfocus computed tomography (micro-CT) and histology. RESULTS: Volume-rendered three-dimensional micro-CT images showed a high-density calcified area infiltrating IPCHA from the femoral cortex as of 6 weeks. When quantified, the calcified volume per unit volume first showed no difference between the two groups at 3 weeks but increased over time, and became significantly greater in the S-group than in the A-group (p = 0.012 and 0.004 at 6 and 12 weeks, respectively). Histologically, IPCHA pores were first occupied by fibrous tissue at 3 weeks; then, the pores adjacent to the femoral cortex were gradually replaced by bony tissue as of 6 weeks for both fixations. CONCLUSIONS: IPCHA allowed new bone formation inside the material even though it was implanted in an on-lay fashion on the cortical bone. Our results suggested that on-lay grafted IPCHA exerted its osteoconductivity well, with more new bone forming in screw-fixated samples than in anchor-fixated samples.