Robotic-assisted internal fixation of hip fractures: a fluoroscopy-based intraoperative registration technique

The internal fixation of proximal femoral (hip) fractures is the most frequ ently performed orthopaedic surgery procedure. When using a sliding compres sion hip screw, a commonly used fixation device, accurate positioning of th e device within the femoral neck-head is achieved by initially drilling a p ilot hole. A cannulated component of the hip screw is then inserted over th e guide wire (surgical drill bit), which is used to drill the pilot hole. H owever, in practice, this fluoroscopically controlled drilling process is s everely complicated by a depth perception problem and, as such, a surgeon c an require several attempts to achieve a satisfactory guide wire placement. A prototype robotic-assisted orthopaedic surgery system has therefore been developed, with a view to achieving accurate right-first-time guide wire i nsertions. This paper describes the non-invasive digital X-ray photogrammet ry-based registration technique which supports the proposed robotic-assiste d drilling scenario. Results from preliminary laboratory (in vitro) trials employing this registration technique indicate that the cumulative error as sociated with the entire X-ray guided robotic system is within acceptable l imits for the guide wire insertion process.