A canine model of osteonecrosis of the femoral head induced by MRI guided argon helium cryotherapy system.

OBJECTIVE This study is to identify the reliability of osteonecrosis of the femoral head (ONFH) modeling established by MRI guided argon helium cryotherapy system in beagles. METHODS A total of 15 beagles were used to establish the ONFH model. The left femoral heads of the beagles received two cycles of argon helium freezing-thawing under MRI guidance and were considered as experimental group while the right femoral heads received only one cycle of argon helium freezing-thawing and were considered as the control group. X-ray, MRI, general shape and histological examinations were performed so as to identify the effect of modeling. RESULTS At 4 week after modeling, MRI showed obvious bilateral hip joint effusion and marked femoral head bone marrow high signal. At 8 week after surgery, abnormal signal appeared in bilateral femoral heads. T1WI showed irregular patchy low signal, T2WI showed irregular mixed signals and the joint capsule effusion showed long T1 and T2 changes. Twelve weeks after operation, T1WI showed a low signal strip with clear boundary and T2WI showed intermediate signal. The changes of the left femoral heads were significant while compared with those of the right sides. The lacunae rates of femoral heads in the experimental group at 4, 8, and 12 week after surgery (40.75 ± 3.77, 57.46 ± 4.01, 50.27 ± 2.98) were higher than those in control group (30.08 ± 3.61, 49.43 ± 2.82, 40.56 ± 2.73). CONCLUSION Canine model of ONFH was successfully established using an argon helium cryotherapy system.