The significance of polymorphisms of gene coagulation factors VII and XIII in the pathogenesis of non-traumatic avascular necrosis of the femoral head by Mikhail A. Panin, Nikolai V. Zagorodnii, Andrei V. Boiko, Larisa M. Samokhodskaya, Medetbek Dz. Abakirov, Evgeny E. Volkov