PRE-OPERATIVE PLANNING FOR TOTAL HIP ARTHROPLASTY STEMS USING THREE DIMENSIONAL COMPUTED TOMOGRAPHY TEMPLATES

Abstract

We usually plan surgery for total hip arthroplasty (THA)using pre-operative X-ray templates. However, the technique provides only two dimensional (2D) images and therefore has limitations for planning three-dimensional (3D) objects. Recently it has become possible to describe 3D images using computer programs that use free down loaded computer software (Hip-op) that enable comparison between 3D templates obtained by computed tomography (CT) and 2D conventional X-ray templates.

Six hip joints in 6 patients (1 male, 5 females; age range at the time of operation, 49–77 years) were evaluated. Five of the patients suffered from secondary osteoarthritis of the hip (secondary OA), while the remaining patient suffered from osteonecrosis of the femoral head (ONFH). All the patients underwent THA using a cement less femoral stem (ANCA-FIT Wright Medical Technology, Arlington, Tennessee, USA). Pre-operative planning was performed using Hip-op software (Rizzoli Institute, Bologna, Italy). After the THA surgery, we carried out a repeat CT scan that was used to analyze stem fitting in the femur.

In all the patients it proved easy to obtain the pre-operative template. In 4 patients, the correct stem size was selected pre-operatively, while in the other 2 patients, the planned stem size was one size smaller than that actually implanted. In the 4 patients in whom the correct stem was selected, 2 had their template correctly assessed by conventional 2D images, 1 patient’s template was one size smaller than the implant, while the remaining patient’s template was two sizes smaller than the implant. In the 2 patients who received implants one size smaller than the CT template, 1 patient had the stem inserted in the virus position while in the other patient a fracture occurred during implantation

Preoperative planning for THA using a CT-based computer templating system proved to be a useful technique for the orthopedic surgeons.