Experience with the Mayo® Conservative Hip System

PURPOSE OF THE STUDYIn the development of cementless total hip arthroplasty wear, loosening as well as stress shielding are considered as major issues.New results in literature specify survivorship of THA over 97%.Consequently the implant loosening and wear especially can be considered as almost solved.Therefore, it is essential to use bone preserving primary implants that allow for a physiological load transfer and cause no or only slight stress shielding at the proximal femur.The MAYO conservative hip stem with a wedge design ensuring immediate primary fixation of the stem with metaphyseal load transfer. MATERIAL AND METHODSA retrospective study was performed to review the first consecutive 316 MAYO ® conservative hip stems implanted at the Martin-Luther-University of Halle-Wittenberg (Germany).85.4% (270 MAYO stems) were radiographic analysed and classified according to the HHS. RESULTSThe mean HHS improved from 44.79 preoperatively to 93.58 postoperatively.1.85% (5 MAYO stems) had to be replaced because of aseptic loosening.Furthermore the DEXA scans revealed the metaphyseal load transfer with increased bone density in the calcar region. CONCLUSIONAs especially younger patients will require one or more hip revision procedures during the course of their life due to their life due to their age and activity level.These patients should receive a primary implant with proximal load transfer.Only these implants can avoid stress shielding of the proximal femur.The minimally invasive implantation of these implants can also ensure an enhanced periprosthetic bone density an optimized postoperative rehabilitation phase. MATERIAL AND METHODSThe authors have gained substantial experience in more than 1,000 implantations of the MAYO ® Conservative Hip System (Zimmer Inc., Warsaw, USA).This shaft system was developed in 1985 at the Mayo-Clinic (Rochester, USA) for the treatment of younger patients.Morrey et al. [6] demonstrated that the intra and postoperative blood loss is reduced significantly with these implants and that the shaft shows excellent long-term results (fig.1).The MAYO ® Conservative Hip System is a cementless short stem hip prosthesis with a wedge design in A/P and M/L plane (fig.2) ensuring immediate primary fixation of the prosthesis in the bone.It is available in 8 sizes (fig.3) and made of Tivaniumr, a Titanium-Aluminum-Vanadium alloy (Ti-6Al-4V).In addition, it provides a partial fibre-mesh-structure (fig.4) and is partially coated with hydroxylapatite.