Original Research
Influence of Orthopedic Implant Structure on Adjacent Bone Density and on Stability
Am J Orthop. 2008 April;37(4):E78-E83
Author and Disclosure Information
Fidèle Likibi, PhD, Gilles Chabot, MD, Michel Assad, PhD, and Charles-Hilaire Rivard, MD
Dr. Likibi is Senior Scientist, Research Center and Orthopaedic Surgery Department, Ste-Justine Hospital, Montreal, Canada, Institute of Biomedical Engineering, University of Montreal, Montreal, Canada.
Dr. Chabot is Clinical Assistant Professor, Research Center and Department of Pediatrics, Ste-Justine Hospital, Montreal, Canada.
Dr. Assad is the Platform Leader, Centre for Bone and Periodontal Research, McGill University, Montreal, Canada.
Dr. Rivard is Orthopedic Surgeon and Professor, Research Center and Orthopaedic Surgery Department, Ste-Justine Hospital, Montreal, Canada, Institute of Biomedical Engineering, University of Montreal, Montreal, Canada.
We evaluated the ability of a porous metallic interbody fusion implant made with porous nitinol (PNT) to achieve intervertebral fusion and the capacity of stabilization at the implantation site 3, 6, and 12 months after implantation. Sixteen sheep each received 1 PNT implant and 1 titanium (TiAIV) cage at intervertebral lumbar levels L2–L3 and L4–L5; 3 other sheep were used as untreated controls. The TiAIV cage was used as a control implant. After animal sacrifice, computed tomography was used to study peri-implant bone mineral density (BMD), and histologic slices were used to evaluate implant osseointegration. BMD around PNT implants was close to physiological (control value) BMD, whereas BMD around TiAIV cages was usually higher (sclerosis) than physiological BMD. Histologic analysis showed better osseointegration with PNT implants than with TiAIV cages. Sclerosis might result from bone acting to stabilize implants in their implantation sites. Compared with PNT implants, TiAIV cages seemed to be unstable in their implantation sites. For PNT implants, osseointegration was successful, and surrounding BMD was close to physiologic BMD.