Evidence of early subchondral bone changes in the meniscectomized guinea pig. A densitometric study using dual-energy X-ray absorptiometry subregional analysis

Objective: Subchondral bone changes are thought to be an important aetiolog ical element in the pathogenesis of osteoarthritis (OA). To confirm this hy pothesis in the meniscectomized (MNX) guinea pig model, bone densitometry w as performed in the subchondral bone of the distal femur. Methods: MNX and sham-operated (SH) guinea pigs were studied 1 and 3 months after partial meniscectomy at the medial side of the left knee. Bone miner al density was measured at the lateral (BMD-L) and medial (BMD-M) sides of the distal femur using dual-energy X-ray absorptiometry (DXA). BMD-M was th en compared to the bone volume evaluated by histomorphometry at the medial epiphyseal part of the proximal tibia (BV-M). Results: One month after operation, in MNX animals left femur BMD-M was sig nificantly lower than in the contralateral femur (-9%, P<0.01) and than in the left femur of SH (-11%, P<0.01). By contrast, 3 months after meniscecto my BMD-M was higher in the femur than in the contralateral femur (+4%, P<0. 05); BV-M tended to be higher on the left than on the right side (+4%, P<0. 06), and was significantly correlated with BMD-M at the 2 grouped time poin ts: r=0.74 (P<0.001). Conclusions: These data emphasize the usefulness of DXA as a simple tool to assess subchondral bone changes at the OA-affected side of the femur and r eveal typical variations of bone metabolism in the initiation of OA patholo gy in the MNX guinea pig: early bone loss at the subchondral level followed by increased bone density. (C) 1999 OsteoArthritis Research Society Intern ational.