DOES THE MIS FULLFILL THE DEMANDS FOR PRECISE IMPLANT POSITION IN THR (ANTEROLATERAL APPROACH, STANDARDIMPLANTS – ZWEYMÜLLER SL PLUS AND SL-MIA STEM, BICON THREADED CUP)

Abstract

Introduction: We perform MIS since 2004 and have done 1257 THR (SL-Plus stem and since 2005 SL MIA stem with a modification in the proximal part). The operation is performed with the anterolateral approach in supine position under direct view with visible landmarks.

Material and Methods: Till know we implanted 357 THR with the new designed stem and the BICON threaded cup. A precise preoperative planning for implant size, neck length and offset is obligatory and is performed with manuel templanting or digital planning on AP X-ray in standing position.

We evaluated used sizes of standard and offset stems and cups, neck length, material of bearing surfaces and on the AP X-ray postoperative in standing position the inclination and anteversion angle of the cup as well as the stem position, postoperative leg length and Trendelenburg sign.

Results: According to the preoperative templating we used offset stems in 30%. of our patients. The neck length small in 14%, medium in 46%, large in 40%.

The range of cup inclination angle was in safe zone with an average of 45,8°, neutral stem position in 92,2%.

Leg length equal in 73% and lengthening or shortening +/−in average 8,4mm and 6,5 mm.

The Trendelenburg sign was negativ in 93% at the time of removal of skin sutures.

Conculsion: The requirement for precise positioning of implant, leg length and muscular function are full-filled with our minimal invasive technique. Also more demanding bearing couples as CC are not at risk.