Abstract
INTRODUCTION
Wedge femoral stems used in total hip arthroplasty (THA) have evolved with modifications including shorter lengths, reduced distal geometries, and modular necks. Unlike fit and fill stems which contact most of the metaphysis, tapered wedge femoral stems are designed to achieve proximal medial/lateral fixation. These single taper, wedge stems have demonstrated positive clinical outcomes. The tapered wedge stem evaluated in this study has further reduced distal geometry to provide a wedge-fit within the metaphysis of the proximal femoral canal for all femur types (Dorr A, B, C). The objective of this study was to evaluate the early clinical outcomes, including femoral stem subsidence, of a tapered wedge femoral stem.
METHODS
Fifty subjects (28 males, 22 females; mean age: 64.7±9.7 years; mean BMI: 29.6±4.6) underwent primary THA with a tapered wedge femoral stem. IRB approval was received prior to conducting the study and all participants signed the informed consent. Clinical data outcomes for this study included the Harris Hip Score (HHS), the Oxford Hip Score (OHS), revisions, and subsidence at the 6-week, 3-month, 1-year, and 2-year post-operative time points. Femoral stem subsidence was measured by an independent third party. Student t-tests were used to identify significant mean differences between genders (p<0.05).
RESULTS
For patients returning for their 2-year post- operative visit (n=42), the HHS improved by 40.7 points to 91.9 from 51.2 and the OHS improved by 23.5 points to 44.6 from 21.1. There was no significant difference between genders with regard to age, BMI, or HHS scores. However, the males had significantly higher pre-operative OHS scores (23.4 vs. 18.2) and 3-month post-operative OHS scores (43.7 vs. 40.3). There were no revisions. There were no observations of femoral stem subsidence at 1 year (n=45) or 2 years (n=40).
DISCUSSION
The tapered wedge femoral stem exhibited positive early clinical results as demonstrated by the significant improvement in functional outcome scores from the pre-operative visit to 2-years post-operative. These 2-year improvements are better than moderate clinically important improvements reported in the literature (40.1 points for HHS). Functional outcomes scores continued to improve at the 6-week, 3-month, and 1-year post-operative visits. The 1-year and 2-year outcomes were not significantly different. Additionally, the implant was well fixated as there were no reports of femoral stem subsidence 2 years post-operative.
SIGNIFICANCE
The tapered wedge femoral stem evaluated in this study demonstrated positive early clinical performance with no reports of femoral stem subsidence or revisions. This tapered wedge stem design is a promising alternative to conventional femoral stems.
