Background: The magnitude and pattern of acceptable long-term migration of cementless femoral stems are not well understood. The Corail hydroxyapatite-coated cementless stem is a clinically successful and commonly used femoral stem with a long-term migration pattern not previously described in the literature. The aim of this study was to assess the long-term migration of the Corail hydroxyapatite-coated cementless stem using radiostereometric analysis (RSA) at 14-year follow-up, thereby establishing a benchmark acceptable long-term migration pattern for hydroxyapatite-coated cementless prostheses.
Materials and methods: A prospective cohort of 29 patients (30 hips) undergoing primary total hip arthroplasty for primary hip osteoarthritis were enrolled into a study to characterise the migration of the Corail cementless stem. A total of 13 patients (4 males, 9 females) with mean age 82 (range 68-92) underwent repeat RSA radiographs at minimum 10 years post-operation (mean 13.9 years, range 13.3-14.4). Subsidence of the stem was measured and compared to prior measurements taken at 6 months and 1, 2, and 6 years.
Results: None of the 13 patients have been revised. The migration at 6 months, 1 year, 2 years, and 6 years has been previously recorded. At mean 14-year follow-up, the cohort mean subsidence of the cementless stem was 0.70 mm (range - 0.06 to 3.61 mm). For each stem followed up at 6 months and 14 years, the mean subsidence over this period was 0.05 mm (range - 0.14 to 0.57 mm). There is no significant difference in mean subsidence at 6 months and 14 years (p = 0.43).
Conclusions: The long-term pattern of the subsidence of the Corail femoral stem has not previously been described. Subsidence occurs within the first 6 months, after which there is persistent stabilisation of the implant to 14 years. This study provides a description of a long-term acceptable migration pattern to which new hydroxyapatite-coated cementless prostheses may be compared.
Level of evidence: II.
Keywords: Radiostereometric analysis; Stabilisation; Subsidence; Total hip arthroplasty.