Cementless modular hip revision arthroplasty with the MRP titanium stem

As the number of primary THRs of younger patients with high physical demands increases, the amount of revision operations also grows. Bone loss with severe osteolysis, joint instability, function of pelvitrochanteric muscles, leg length discrepancy, a proper antetorsion angle, cement mantles, periprosthetic fractures, or infections are problems to be considered in revision arthroplasties of the hip. A femoral prosthesis stem should guarantee the proximal transmission of force. The aim of this prospective study was to scrutinise the outcome of hip joint revisions using the modular revision prosthesis (MRP) titanium stem. The mean follow-up time for all 72 patients including 34 men and 38 women was 3.6 years (range, 2-7 years). The mean age of the patients at the time of the operation was 67.3 years (range, 45.588.6 years). The indication for the hip revision arthroplasty was in 56 cases an aseptic loosening of cup and stem, in 14 cases an aseptic loosening of the stem, and a Girdlestone hip in 2 cases. The Harris hip score improved from 54.9 to 92.2. In all cases the spontaneous refill of bony defects was detected with remodeling of bone without any bone transplantation. The most common intraoperative complication was a femoral fissure or fracture during the stem removal (4 cases), the most common early postoperative complication a deep venous thrombosis (2 cases), and the most common late postoperative complications a recurrent dislocation (2 cases), a subsidence of the stem (2 cases), or a persisting infection necessitating the removal of the prosthesis (2 cases). The revision rate was 4.17 %. With the MRP titanium prosthesis a stable primary fixation with a reduced risk of dislocation could be achieved. Modularity of the prosthesis allows an optimal lever arm to improve the function of pelvitrochanteric muscles, to equalise leg legth discrepancy, and to choose a proper antetorsion angle. A total hip replacement (THR) is one of the most successful principles in orthopaedic surgery. As the number of primary THRs of younger patients with high physical demands increases, the amount of revision operations also grows. Bone loss with severe osteolysis, joint instability, function of pelvitrochanteric muscles, leg length discrepancy, a proper antetorsion angle, cement mantles, periprosthetic fractures, or infections are problems to be considered in revision arthroplasties of the hip. The osseous anchoring is essential for the function of THR (1). Bone defects need long revision stems. According to recently published good results in hip revision surgery (1-9), there is a tendency for cementless revision arthroplasty. A femoral prosthesis stem should guarantee the proximal transmission of force to avoid the atrophy of the proximal femur caused by stress shielding. Still sometimes only a distal fixation can be achieved because of the considerable bone resorption (1). A modular revision prosthesis can resolve these problems (2, 3, 5-7, 10). In order to improve the durability of a revision prosthesis, wear has to be reduced by diminishing e.g. the friction between the femoral head and the acetabular cup, and the morse taper junctions. Although some negative effects of the modularity regarding morse taper junctions have been published (6), most authors have found no disadvantages (8, 11-15).