Modular calcar replacement prosthesis with strengthened taper junction in total hip arthroplasty.

Whereas femoral component modularity allows the surgeon to address a variety of femoral defects in complex total hip arthroplasty (THA), breakage of modular stems is a known complication that typically occurs at the taper junction. In response, a proprietary process of taper roller-hardening that increases taper strength by a factor of 3.5 was introduced in 1999. The authors reviewed a consecutive series of patients by a single surgeon who underwent cementless revision or difficult primary THA with a taper roller-hardened modular calcar replacement prosthesis, and have the potential for a minimum of two-year follow up. In 116 patients, 123 hips were involved. Two surgeries were primary, 101 were revision/conversion, 18 were for reimplantation after treatment of infection, and two were intramedullary total femur constructs, one of which was a reimplantation after sepsis. The patients' ages at surgery averaged 71 years, and BMIs averaged 28.12 kg/m2. Nine of the patients, all with single hip involvement, were lost to contact. Twenty-one patients, three of whom had bilateral hip involvement, expired during the follow-up period with implant outcome known. Follow up in the patients who survived averaged 44 (range: 18-78) months. Six femoral components have been revised: two (1.6%) due to recurrent sepsis, three (2.4%) due to sepsis, one (0.8%) from periprosthetic fracture, and none from septic loosening or component breakage. Survivorship with aseptic loosening as the end-point was 100%. In this series, roller-hardening appears to improve the durability of the tapered junction. No roller-hardened modular calcar devices have failed due to component breakage. However, their use is not recommended in the totally deficient proximal femur, as fatigue breaks of distally fixed monoblock extensively coated stems have been reported. Caution is advised when potting or anchoring any stem in the femoral diaphysis without reconstituting proximal bone stock and support.