Computer-Assisted Minimally Invasive Curettage and Reinforcement of Femoral Head Osteonecrosis with a Novel, Expandable Blade Tool

+*Koyama, T; *Sugano, N; *Miki, H; **Murakami, A; *Nishii, T; *Sato, Y; *Yoshikawa, H; *Tamura, S; *Ochi, T +*Osaka University Graduate School of Medicine, Osaka, Japan. [email protected] Introduction It has been reported that almost 100% of hips with extensive type of osteonecrosis of the femoral head (ONFH) show progression of collapse if they do not receive any surgical treatment. Core decompression with or without bone grafting is one of the popular joint-preserving procedures in early stages. This procedure is performed through the lateral subtrochanteric route, which is comparatively less invasive, but has a limitation in curetting a large lesion through a long narrow hole. It has been reported that 20–40% of hips treated with this procedure resulted in collapse. On the other hand, the trapdoor procedure enables to curette a large lesion effectively through a trapdoor made in the femoral head, however, this procedure is quite invasive because the hip needs to be exposed in order to make a trapdoor. We think that the collapse may be prevented if the necrotic lesions are curetted thoroughly and the deficit is filled with reinforcement materials such as hydroxyapatite (HA) with sufficient mechanical strength. For less invasive curettage of necrotic lesions, we have developed a novel, expandable blade tool (Fig. 1) which can be introduced into the femoral head through the lateral subtrochanteric route under navigation guidance. In this study, we evaluated the effectiveness and feasibility of this tool in comparison with a conventional bone cutter, with respect to curettage of target necrotic lesions supposed in a Sawbones femoral head. Moreover, we evaluated the compressive strength of the Sawbone femoral head after the inside part was curetted with this tool and filled with HA blocks.