A Study Of A New Classification For Osteonecrosis Of Femoral Head Secondary To Femur Neck Fracture In Adolescent

ObjectiveFemur neck fracture in adolescent was very rare and mostly induced by high energy trauma. Femur neck fracture in adolescent were associated with high rate of complications such as osteonecrosis of femoral head, ununion, premature physeal closure and coxa vara. Osteonecrosis of femoral head secondary to femur neck fracture was considered as the most dangerous comlication and impaired the development of proximal femur. Otherwise severe collaspe of femoral head would induce instability of hip joint. Our study was to summarize the natural history of osteonecrosis of the femoral head secondary to Femoral Neck Fracture in adolescent preliminarily, and to analyze the risk factors of instability of hip joint by logistic stepwise regression analysis, and to establish a new staging and classification system to predict the stability of hip join.MethodsFrom January2006to January2013,45adolescent cases of osteonecrosis of the femoral head after Femoral Neck Fracture were treated with different head therapies and their natural histories before therapy were retrospectivelyanalyzed.43cases were treated with head preserved therapy, including23cases treated with Chinese traditional medicine,5cases treated with femoral head reconstructive surgeries and15cases treated with femoral head reconstructive surgeries combined pelvic osteotomy, we analyzed the general dates, lesion size, lesion area, collapse degree before surgery and analyze the risk factors of instability of hip joint by logistic stepwise regression analysis in SPSS19.0.Results1. General date:45cases(45hips) in total;22cases in left size,23in right size.39male cases,6female cases. Age was ranged from12to18, average age was15.42±1.28.2. Characteristics of Osteonecrosis of femoral head secondary to femur neck fracture in adolescent:(1)most cases were suffered from a large area of necrosis.(2)most cases’lesion sizes were located in anterolateral pillar. Depending the integrity of subchondral bone in weight bearing area in femur head,22cases were fully involved,19cases were partly involved,4cases were uninvolved.(3)In38cases premature physeal closure was observed, and in28cases deformities in Proximal femur were observed, mainly included small and flat head, shortening neck, and coxa vara.(4)hip joint instability which include a group of symptoms of hip subluxation, pelviclistm, and limb shortening was observed in17cases.3. The factor of " fully involved subchondral bone in weight bearing area in femur head" was the only risk factor to predict hip joint instability (p=0.003<0.05)4. The classification system to predict hip joint stability:our new classification was established by evaluating the integrity of subchondral bone in weight bearing area in femur head.Type A:subchondral bone in weight bearing area in femur head was uninvolved. Type A had a low rate of collapse and hip joint instability.Type B:subchondral bone in weight bearing area in femur head was partly invovled. Type B had a rate of30%to collapse, and would not induce hip joint instability.Type C:subchondral bone in weight bearing area in femur head was fully involved. This type had a high rate (almost80%) of collapse and hip joint instability.ConclusionONFH after Femoral Neck Fracture in adolescent was known as rapidly progressive with a high rate of collapse. Severe collapsed would lead to the instability of hip joint which include a group of symptoms of hip subluxation, pelviclistm, and limb shortening. The adolescent with instability of hip joint should be treated with surgery to reconstruct their stability. The new classification of hip joint stablility can predict the natural history and outcome of ONFH after Femoral Neck Fracture in adolescent, and finally instruct the establishment of head preserved protocol.