Clinical and Biomechanical Study to Develop a Joint-Preserving Therapy for Femoral Head Osteonecrosis

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Aseptic osteonecrosis of the femoral head is a serious disease which results in destruction of the hip if left untreated. A new surgical procedure which preserves the femoral head has been developed for patients with a still intact femoral head at the time of diagnosis. The aim of this procedure is to completely remove all necrotic tissue through an exactly targeted drill channel using a special instrument. The femoral head is then stabilised with a bone substitute based on calcium phosphate and calcium sulphate. Postoperatively, the bone substitute material is resorbed and replaced by newly formed cancellous bone. So far, clinical follow-up of this therapy has revealed better results than the conventional core decompression therapy without removal of the necrotic tissue and other femoral head preserving procedures. The results also showed that the success of the therapy depends significantly on the size of the necrotic area and the amount of necrotic tissue remaining in the void. Histological investigations of collapsed femoral heads after advanced core decompression also confirm the necessity of complete removal of all necrotic tissue, as bone regeneration was seen only at the interface between healthy cancellous bone and the bone substitute material. However, MRI follow-up examinations show that it is often not possible to completely remove all necrotic tissue because even the smallest deviation from the optimal drill channel position leads to markedly inferior resection and current instruments do not enable complete removal in all cases. The aim of this study is to optimise the drilling procedure and removal of necrotic tissue. To achieve this, a better understanding of the biomechanical properties of the femoral head, especially with regard to its postoperative stability, is necessary. Therefore, various entry points and angles of the drilling channel and subsequent filling with two different types of bone substitute material will be investigated, both experimentally and numerically. Based on the results, a special planning programme will be developed and combined with a navigation system which will enable optimal removal of the necrotic tissue taking biomechanical conditions into consideration. A further aim of the study is to optimise the drilling instruments. All modifications will be re-evaluated in the light of findings obtained from follow-up examinations of the patients treated.