Preservation of periarticular cancellous morphology and mechanical stiffness in post-traumatic experimental osteoarthritis by antiresorptive therapy.

BACKGROUND Bone changes in experimental post-traumatic osteoarthritis occur early after transection of the anterior cruciate. The purpose of this study was to determine whether antiresorptive bisphosphonate therapy could slow or arrest the periarticular bone architecture and mechanical properties in a post-traumatic model of knee osteoarthritis. METHODS Skeletally mature, female New Zealand white rabbits were assigned to three groups (N=8/group). In two groups, anterior cruciate ligament transection was performed and half were left untreated, and the other half dosed with risedronate (0.01 mg/kg s.c. daily) for a six week period. A third group included age-matched normal controls. At the end of the six week period, all rabbits were euthanized and the femur was scanned by micro-computed tomography to assess morphology and density. Specimen-specific finite element analyses quantified the periarticular bone architecture and mechanical properties. FINDINGS The untreated transected group had reduced bone volume ratio and mechanical properties compared to the controls (P<0.05) and risedronate-treated transected animals (P<0.02), suggesting bone conservation. Changes in bone volume ratio and mechanical properties of the risedronate-treated transected animals compared to the controls were not detected, indicating that risedronate did not improve these properties relative to the normal controls. The untreated transected group had reduced apparent cancellous bone mineral density and cortical thickness compared to transected animals treated with risedronate (P<0.05). INTERPRETATION Bisphosphonate therapy altered the short-term progression of periarticular bone changes including micro-structure and mechanical integrity by slowing early-stage changes to the micro-architecture. These changes following joint trauma may impact the long-term outcome of post-traumatic osteoarthritis.