Abstract
Introduction
Varus positioning of cemented ‘composite beam’ stems is associated with increased risks of aseptic loosening and stem fracture. We investigated whether the incidence of varus malalignment of the Exeter polished, double taper design in a multicentre prospective study adversely affected outcome after total hip replacement (THR).
Materials & Methods
A multicentre prospective study of 1189 THR was undertaken to investigate whether there is an association between surgical outcome and femoral stem malalignment. The primary outcome measure was the change in the Oxford hip score (OHS) at five years. Secondary outcomes included the rate of dislocation and revision, stem subsidence, quality of cementing. 938 (79.89%) were followed-up at five years.
Results
44 from a total of 1189 femoral stems (3.7%) were implanted in varus (=5° to the femoral axis). Pre-operative demographics and OHS were similar in both groups (p>0.05). Varus implantation was commoner after posterior than anterolateral approach (p< 0.001). Differences in the presence of femoral radiolucency, stem subsidence and quality of cement mantle were not significantly different (p>0.05). There was no difference in absolute OHS or OHS gain between the groups (neutral, mean = 40; varus, mean 40, p = 0.45, OHS gain neutral: 24, varus: 23, p=0.46). Differences in dislocation (p=0.54) or revision rates (p=0.35) were not significant.
Conclusion
This study provides evidence that the Exeter stem may be tolerant of varus malalignment, both in terms of patient reported outcome and complication rate up to five years following surgery. Establishing whether aseptic loosening will be more common in the varus group will require longer follow-up.
