LONG-TERM RESULTS OF GENDER THA USING MODULAR NECKS WITH DUAL STEM TECHNOLOGY

Abstract

Introduction: Improved biomechanics and stem fit facilitated by gender adepted dual stems and modularity has the potential to make THA easier and thereby decrease the complication rate. Increased fretting wear at the connecting interfaces may be a drawback. 10 year survival exceeding 90% is required to endorse modular necks and dual stem gender technology.

Materials and Methods: We followed the first 190 consecutive implantations of an uncemented, straight femoral stem with dual stem technology and modular necks (European Hip System (EHS)/Profemur E, Wright Medical Technology Inc., Arlington, TN, USA) and a grit blasted titanium acetabular cup with a ceramic on polyethylene bearing in 178 patients from 1992 to 1997. Mean time of follow-up evaluation was 10 (8–13) years. Titanium serum ion levels were measured to detect fretting in the metal connection.

Results: At follow-up, 21 patients (22 hips, 11.6%) had died, and 13 (14 hips, 7.4%) were lost to follow-up. One hip underwent femoral revision for a periprosthetic fracture. Overall stem survival was 99 (98–100) % at 10 years, survival with femoral revision for aseptic loosening as an end point was 100 (99–100) % at 10 years. Three acetabular components were revised, one for infection and two for aseptic loosening of the titanium shell. There was one fracture of a high offset modular neck at the laser labeling without trauma; the design was changed subsequently. The mean Harris-Hip-Score at follow-up was 88 points. 153 hips were available for radiolographic evaluation. No case of femoral or acetabular osteolysis or loosening was found. Accelerated wear was not detected on radiographs. No dislocation was found during the study period. The results showed no increased titanium serum ion levels compared to an age matched control group.

Conclusions: The complication rate with this uncemented modular gender hip system was extremely low with a high patient (and surgeon) satisfaction. The modular neck system as well as the dual stem technology proved to be reliable. The metal ion analysis revealed no elevated serum ion levels. Modular necks and dual gender stems are a reliable and durable option in primary total hip arthroplasty.