MRI Study Of Rabbit Model Of Early Femoral Head Necrosis Induced By Hormones

Background:Steroid-associated osteonecrosis (ON) is an intractable and disabling disease in orthopedics, accounting for more than50%in nontraumatic ON and showing poor prognosis, especially in its advanced stage. Early diagnosis or detection of ON is very important as its prognosis is stage-dependent.Up to date, the most sensitive and commonly used modality for early ON detection relies on the abnormal signal of conventional magnetic resonance imaging (MRI)(T1-weighted and T2-weighted MR imaging), which matches the necrotic and repairing reaction in bone and marrow. Yet more than80%of ON cases found in this stage would progress into symptomatic ON requiring surgical interventions. More sensitive modality is desirable for earlier diagnosis or prediction of ON development. Gd-DTPA enhanced dynamic MRI can detect early perfusion lesion. It’s more sensitive for ANFH prediction.Object:To build steroid-associated rabbit ANFH models.To evaluate steroid-associated rabbit ANFH models in static and dynamic MR imagings and histopathologic findings. To study the relationship between MR imaging and histopathology.To discuss the mechanisms of steroid-associated ANFH, and make suggestions for early radiologic detection of steroid-associated ANFH.Material and methods:Object:24adult New Zealand rabbits, divide into3groups randomly,8in each group.Model building:Group A:large dose steroid associated with endotoxin. Group B: large dose steroid independently. C:control.Method:MR imagings:T1WI, fat suppression T2WI, Gd-DTPA enhanced dynamic MRI.Histopathologic research. Results:Osteonecrosis occurred in85.71%(6/7) rabbits in group A, and42.86%(3/7) in group B, none in group C.Abnormal signals were found in57.14%(4/7) rabbits in group A, and28.57%(2/7) in group B, none in group C.Blood perfusion decreased in85.71%(6/7) rabbits in group A, and42.86%(3/7) in group B, none in group C.Osteonecrosis occurred in all th rabbits whose ME value decreased over50%than baseline. ME value of osteonecrosis-negative rabbits also decreased obviously in statistics.Conclusion:Large dose steroid injection with or without endotoxin injection can lead to osteonecrosis. Endotoxin enhances the osteonecrotic effect of steroid.MRI is sensitive and specific for early detection of ANFH. And it’s relative to histopathologic development.Gd-DTPA enhanced dynamic MRI is more sensitive than traditional static MRI. It can be used for early diagnose of ANFH in high-risk population.The animal model built in this study has good similarity to human steroid-associated osteonecrosis. It can be used for further studies of clinical intervention of ANFH.