Ten-year migration analysis of a cementless metaphyseal-anchored short femoral stem in total hip arthroplasty.

PURPOSE: Short-stem total hip arthroplasty aims to improve metaphyseal load transfer while enabling minimally invasive implantation via the direct anterior approach. Long-term migration and clinical data for these implants remain limited. This study evaluated 10-year femoral stem migration, periprosthetic radiolucency, and clinical outcomes for a cementless, metaphyseal-anchored short stem.

METHODS

In this single-center retrospective study, 66 hips in 57 patients underwent primary THA with the AMIStem-H (Medacta International) between 2010 and 2012. Stem subsidence was measured serially using EBRA-FCA, radiolucency was graded by Gruen zone, and clinical function was assessed with the Harris Hip Score (HHS).

RESULTS

Median stem subsidence increased from 0.51 mm at 3 months to 1.45 mm (IQR 0.72-2.12 mm) at 10 years, with most migration occurring in the first five years; 33.3% of stems subsided > 2 mm. Radiolucency > 2 mm was present in 33.3% of hips, without progression between 5 and 10 years or correlation with clinical outcome. Median HHS at final follow-up was 97, with 89.2% of hips rated good or excellent. Two implants (one stem, one acetabular component) required revision for aseptic loosening.

CONCLUSION

The AMIStem-H demonstrated durable fixation and excellent clinical outcomes at 10 years, with limited, predominantly early axial migration; neither subsidence nor periprosthetic radiolucency was associated with functional outcome. As many patients who received an AMIStem-H are now entering long-term follow-up, surveillance should prioritize new symptoms or progressive radiographic change over isolated, low-magnitude subsidence.