Abstract
Background : A composite femoral stem was introduced with a structural stiffness similar to that of the native femur to promote proximal load transfer. This consisted of a cobalt-chromium alloy core surrounded by an injection-moulded layer of polyaryletherketone covered with a porous titanium mesh.
Material and Methods: 31 consecutive primary total hip replacement stems were implanted in 26 patients with an average age of 37 years (range 17–57) using the Epoch stem (Zimmer, Warsaw, IN) as part of a prospective multi-centre trial. A cementless Harris-Galante I acetabular component with a 28mm polyethylene insert (Zimmer) was used in 29 cases, a Plasmacup with 28mm polyethylene insert (Aesculap, Tuttlingen, Germany) in 1 case and a bipolar head in 1 case. Annual follow-up with Harris Hip Scores and radiographic evaluation was performed for a mean of 10.1 years.
Results : Harris Hip Scores improved from a mean of 52 points preoperatively to 90 at the time of last follow-up. Radiographs showed no stem migration or loosening. 4 cases with polyethylene wear showed trochanteric osteolysis. Specific radiographic features noted were a sclerotic halo in Gruen zones 1 in 8 cases, calcar rounding in 10 cases and improvement in calcar appearance with squaring of the calcar in 4 cases. Calcar resorption was seen in 1 case associated with polyethylene wear. There have been 8 instances of revision of the head or acetabular component- 3 liner exchanges for polyethylene wear, 3 acetabular component revisions for liner dissociation with associated cup damage, 1 acetabular component revision for infection and 1 bipolar head revised to unipolar head with cementless acetabular component for pain. No stem has required or requires revision.
Conclusion : The Epoch stem resulted in an excellent clinical outcome with evidence of radiographic stability and proximal bone preservation, and no cases of stem revision in a cohort of young patients with long-term follow-up.
Correspondence should be addressed to Ms Larissa Welti, Scientific Secretary, EFORT Central Office, Technoparkstrasse 1, CH-8005 Zürich, Switzerland
