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

无菌性股骨头坏死是一种严重的疾病，如果不及时治疗，会导致髋关节的破坏。一种新的保留股骨头的外科手术已经被开发出来，用于诊断时股骨头仍然完整的患者。该手术的目的是使用特殊工具通过精确定位的钻孔通道完全清除所有坏死组织。然后用基于磷酸钙和硫酸钙的骨替代物稳定股骨头。术后，骨替代材料被吸收并被新形成的松质骨替代。迄今为止，该疗法的临床随访显示其效果优于传统的不去除坏死组织的髓芯减压疗法和其他保留股骨头的手术。结果还表明，治疗的成功在很大程度上取决于坏死区域的大小和空隙中剩余的坏死组织的量。在高级髓芯减压后塌陷股骨头的组织学研究也证实了完全清除所有坏死组织的必要性，因为仅在健康松质骨和骨替代材料之间的界面处观察到骨再生。然而，MRI随访检查表明，通常不可能完全清除所有坏死组织，因为即使是最佳钻道位置的最小偏差也会导致明显的下切除，并且目前的器械无法在所有情况下完全清除。本研究的目的是优化钻孔程序和坏死组织的清除。为了实现这一点，更好地了解股骨头的生物力学特性，特别是关于其术后稳定性，是必要的。因此，将通过实验和数值模拟研究钻孔通道的各种进入点和角度以及随后填充两种不同类型的骨替代材料。根据结果，将开发一个特殊的计划程序，并与导航系统相结合，这将使坏死组织的最佳切除考虑到生物力学条件。本研究的另一个目的是优化钻孔仪器。将根据接受治疗的患者的随访检查结果重新评价所有修改。

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.