Abstract
INTRODUCTION
Short femoral stem use in total hip arthroplasty (THA) has increased due to positive short-term clinical and biomechanical success. A neck preserving femoral stem not only preserves proximal bone volume, but preserves the high quality bone of the medial neck. The short stem design allows for less invasive surgical exposure and less invasive violation of the femoral canal (Figure 1). Additionally, it facilitates future revision THA, if needed, with a conventional primary stem. The objective of this study was to evaluate the early clinical outcomes of the Alteon® Neck Preserving Femoral Stem (Exactech, Inc.).
METHODS
Forty-nine subjects (25 males, 24 females; mean age: 58.3±7.6 years; mean BMI: 29.8±5.6) from 2 sites underwent primary THA with the Alteon Neck Preserving Femoral Stem. All participants signed the informed consent, and both sites received IRB approval prior to conducting the study. Clinical data outcomes for this study included the Harris Hip Score (HHS), the Oxford Hip Score (OHS), revisions, and subsidence at 3-month, 1-year, and 2-year post-operative time points. Subsidence was measured by an independent third party. Student t-tests were used to identify significant mean differences between genders (p<0.05).
RESULTS
The means and standard deviations for the HHS and OHS are shown in Figures 2 and 3 respectively. For patients reaching the 2-year post-operative time point (n=28), the HHS improved by 51.3 points to 96.1 from 44.8 and the OHS improved by 23.0 points to 43.8 from 20.8. There was no significant difference between genders with regard to BMI or post-operative HHS or OHS scores. However, the females were significantly older (61.4 vs. 55.3) and had a significantly lower pre-operative HHS (44.3 vs. 53.5). There were 2 revisions reported, and there was one report of subsidence at 1 year (n=33); zero reports of subsidence at 2 years (n=24).
DISCUSSION
The neck preserving femoral stem exhibited positive early clinical results as demonstrated by the marked 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 kept improving at the 3-month, 1-year, and 2-year post-operative visits. Additional 2-year outcomes data will be incorporated into this dataset as they become available.
For the two revisions, one was due to a calcar fracture and one was due to a patient fall. The patient who fell reported weight-bearing pain after the fall at the 1-year post-operative visit and was subsequently revised. Stem movement was documented as a result of the fall; this was the only report of subsidence.
SIGNIFICANCE
The neck preserving femoral stem evaluated in this study demonstrated positive early clinical performance with no reports of subsidence (except for one case that was revised due to a fall). This neck preserving stem design is a promising alternative to conventional femoral stems.
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