RESUMEN
<p><b>OBJECTIVE</b>To investigate the advantages of using the preoperative computer-aided design system (CAD) in total hip replacement (THR).</p><p><b>METHODS</b>From March 2002 to September 2005, 182 patients who underwent primary THR were screened and divided into 2 groups randomly. CAD and traditional preoperative templating were used in preoperative planning respectively.</p><p><b>RESULTS</b>In group using CAD, the migration of the center of acetabulum was smaller, and the discrepancy of the limb length and the abductor force lever arm were fewer. All the differences above were significantly different.</p><p><b>CONCLUSIONS</b>CAD helps remove much of the guesswork during surgery, and the implant can be more precise fitting to the patient. And equal limb lengths and balanced abductor force can be restored more accurately.</p>