The aims of the this study were establishment of rabbit's ONFH models by liquid nitrogen freezing method that can simulate human's pathological changes.

Ten healthy New Zealand female rabbits were used in this study, month-age (3.0±0.2), weight (3.2±0.4)Kg. We selected the left side to be the operated side and considered the right side as the control. The rabbits were anesthetized by ear marginal intravenous injection, then be fixed on the fixation shelf. The skin incision was made on the lateral of left hip joint.And then we chose the appropriate bone landmark as the point for starting drill. Then the hole was drilled toward the femoral head with a appropriate femoral neck anteversion and abduction angle with a 2.0 mm kirschner wire. The femoral head were frozen by liquid nitrogen freezing equipment, followed by rewarming with warm saline two cycle. Ten rabbits were sacrificed post-operation for the fourth week to observe the shape and color of femoral head. Then X-ray, micro-CT, MRI and histopathological sections were performed to test the results.

All the rabbits survived post-operation. The color of left femoral head gets dark, and we also found sheet necrosis area under the articular cartilage in the weight-bearing area. X-ray showed there is no apparent change in bone mineral density. Micro-CT showed thin disorganized trabecular bone. MRI showed mixed-signal of hyperintense signal and hypointense signal in operated femoral head. Histopathological examination showed obvious evidences of ONFH, including empty lacunae, integrated fat cells, disorganized trabecular bone and so on. All the left femoral heads appeared early stage osteonecrosis.

We have prepared rabbit ONFH model successfully by the new method with smaller trauma and more simply operation that don’t need capsulotomy and dislocating the femoral head, which could be a new standard method of preparing the rabbit femoral head necrosis model.