THE USE OF CUSTOMIZATION TO DEVELOP A MIS TOTAL HIP PROSTHESIS

Customization makes it possible to fulfill design requirements during MIS-THA procedures, and has helped define the parameters of fit and fill. This study describes the results of using customization techniques to develop a femoral implant for utilization. CT-based design criteria for femoral implants has-been developed and used for primary, cement-less, non-minimally invasive THA surgery. Over 1000 procedures performed with these devices have been associated with displaced femoral fractures, and have been revised for septic loosening. This study has 2 parts: 1. 20 implants were designed and implanted with CT-based criteria that utilized the identical fit and fill standards of the custom implants previously established, but had short (< 115 mm), tapered stems; 2. 20 patients underwent primary, cement-less THR wherein an off-the-shelf femoral implant system was determined to fulfill fit and fill requirements of custom implants. The stem of these implants was shortened (95–115 mm) and tapered. Implants in both groups were inserted using a single incision, posterior-lateral MIS approach. Patients were followed clinically and radiographically for six months. Immediate full weightbearing and use of a single cane were encouraged. The use of CT-based customization techniques is helpful for defining design criteria of femoral implants, but the instrumentation for inserting these implants must be adapted to the specific surgery. Customization also facilitates the design and evaluation of CAOS applications for inserting these MIS implants.