Doxycycline effects on mechanical and morphometrical properties of early- and late-stage osteoarthritic bone following anterior cruciate ligament injury

As posttraumatic osteoarthritis (OA) progresses, the mechanical and morphometrical properties of the subchondral bone change and may be linked to damage of the articular cartilage. Potentially to slow that progression, doxycycline was administered orally twice daily (4 mg·kg−1·day−1) in skeletally mature canines after anterior cruciate ligament transection (ACLX). To test if doxycycline significantly altered the structure and function of OA bone, we tested cancellous bone mechanical properties, measured bone mineral content, and analyzed bone structure by microcomputed tomography. Our investigation focused on subchondral trabecular bone changes in the medial femoral condyle at 36 and 72 wk after ACLX. Significant mechanical changes discovered at 36 wk post-ACLX were less obvious at 72 wk in both treated and ACLX groups. Doxycycline treatment conserved bone strain energy density at 72 wk. Doxycycline had little effect on the degradation of superficial osseous tissue at 36 wk post-ACLX; by 72 wk, doxycycline in an ACLX model limited subchondral bone loss within the first 3 mm of periarticular bone with established OA. Significant bone loss occurred in the deeper trabecular bone for all groups. Substantial architectural adaptation within deeper trabecular bone accompanied changes in mechanics in early and established OA.