Abstract
Introduction
Varus alignment of the femoral component in total hip arthroplasty (THA) is thought to be a risk factor for implant loosening and early revision surgery. The purpose of this study was to evaluate whether the Exeter stem tolerates varus alignment and assess if this theoretical malalignment has an influence on clinical outcomes.
Methods
A total of 4126 consecutive THAs were reviewed for patients between 2006 and 2012 to allow for a minimum five-year follow-up. To determine the effects of the stem alignment on results, the hips were classified into 3 groups on the basis of stem alignment in initial postoperative anteroposterior radiographs. The alignment of the stem was defined as neutral, valgus (≥ 3° of lateral deviation), or varus (≥ 3° of medial deviation). The primary outcome was all cause revision with patient related outcomes assessed with Oxford hip score pre and post-operatively.
Results
The mean follow-up period was 8.6 years. 3803 (92.2%), 48 (1.2%), and 275 (6.7%) hips were assessed as neutral, valgus, and varus alignment, respectively. Assessment of outcomes showed that 75 revision surgeries (1.8%) were performed during follow-up for a variety of causes but there was no significant difference in the revision rate among the 3 alignment groups. No stems were revised for aseptic loosening in any of the three groups. Oxford Hip scores were obtained at a mean of 4.6 years post-operatively and no significant difference in patient reported outcome was identified between the different alignment groups.
Conclusion
This study suggests that the Exeter stem tolerates varus alignment well with no demonstrable effect on revision rate or patient reported outcome. This tolerance of malposition compared to the negative results reported in the literature with other stem designs can be of reassurance to surgeons using the Exeter system.
