Mid-term migration pattern of a calcar-guided short stem: A five-year EBRA-FCA-study

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Implant migration analysis

Background:

• Short-stem hip implants often lack mid- and long-term migration data.
• Early axial migration has been observed in some short-stem designs.

Purpose of the Study:

• To evaluate the mid-term (5-year) migration pattern of a specific calcar-guided short stem.
• To identify factors influencing stem migration and stability.

Main Methods:

• 191 calcar-guided short stems were assessed using Ein-Bild-Roentgen-Analysis Femoral-Component-Analysis (EBRA-FCA) at 5 years.
• Migration patterns were analyzed and compared between groups based on early subsidence, Dorr types, age, gender, weight, BMI, and surgical laterality.
• Varus and valgus stem alignment outcomes were also assessed.

Main Results:

• Mean axial subsidence was 1.5 mm at 5 years.
• 73 stems were "at hazard" (subsidence >1.5 mm at 2 years), with 69 achieving secondary stabilization.
• Male gender, heavy weight, and valgus alignment were associated with higher axial migration risk; undersizing was noted in 4 unstable cases.

Conclusions:

• Calcar-guided short stems generally achieve stable fixation by 5 years, even in stems initially showing migration.
• Male and heavy-weight patients are at increased risk for continued subsidence.
• While clinical consequences remain uncertain, stem undersizing may contribute to instability.