After producing bilateral osteonecrosis of the femoral head, rats were medicated alendronate according to one of 6 schedules. In group 1 injection was administered one week prior to the operation of devascularization and thereafter was continued for another 42 days. In group 2, medication started on the day of the operation. The control group 3 was similarly handled except that they were given injections of physiological saline. Group 4 animals were subjected to drilling of the right femoral head and treated with alendronate a week before the operation and 42 days thereafter, while in group 5 medication begun on the day of the operation. Control group 6 was similarly handled, but received physiological saline. The furthest advanced changes occurred in groups 3 and 6 (in which an advanced stage of an osteoarthritis–like disorder were observed) followed by groups 4 and 5 (in which alterations were mild to moderate), and finally by groups 1 and 2 (in which there were but mild changes). In addition, all changes were less pronounced in the animals which had been treated with alendronate for one week prior to the operation than in those given the first dose from the operative day. These findings demonstrate that bisphosphonate medication preserves the shape of rats’ femoral heads in the early post–necrotic phase to a greater degree than in the Authors’ earlier, diverse attempts to arrest the disastrous progression of the post–necrotic remodeling towards hip osteoarthritis. The presented findings warrant the preclinical trial of bisphosphonate therapy in patients admitted for the management of osteonecrosis of the femoral head.
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