title: Differences in subsidence rate between alternative designs of a commonly used uncemented femoral stem.
abstract: BACKGROUND
  Measurement of early subsidence of uncemented femoral stems can be used to evaluate the likelihood of long term stem component loosening and therefore clinical failure. Our aim was to evaluate the factors associated with subsidence in collared and uncollared versions of the Corail femoral stem.
  
  
  METHODS
  121 hips in 113 consecutive patients were studied, operated on by two surgeons in our hospital differing in their choice of Corail stem. This gave two groups of patients with 66 hips having collared stems and 55 hips having uncollared. We recorded patients' age, sex, ASA grade and BMI. Radiographs post-operatively at day 1, 6 weeks and 1 year were evaluated measuring subsidence, angulation, signs of stability and fixation, and canal fill ratio at the metaphysis and diaphysisafter correcting for magnification errors by calibration using femoral head size.
  
  
  RESULTS
  Clinically significant subsidence (>3 mm) occurred in 7.6% of collared and 10.9% of uncollared stems, all within 6-8 weeks, but did not reach statistical significance (p = 0.345). Revision for symptomatic loosening was required in 1 patient in each group (1.5% collared versus 1.8% uncollared).
  
  
  CONCLUSIONS
  Early subsidence of Corail femoral stem should alert surgeons to closer patient follow-up as the rate of early revision is 18% in stems with >3 mm of subsidence. However, the presence of a collar does not seem to be protective.
authors.affiliation: Scunthorpe General Hospital, United Kingdom.
authors.forename: Munnan
authors.initials: M
authors.lastname: Al-Najjim
authors.affiliation: Scunthorpe General Hospital, United Kingdom.
authors.forename: Usman
authors.initials: U
authors.lastname: Khattak
authors.affiliation: Keele University, United Kingdom.
authors.forename: Juluis
authors.initials: J
authors.lastname: Sim
authors.affiliation: Scunthorpe General Hospital, United Kingdom.
authors.forename: Iain
authors.initials: I
authors.lastname: Chambers
keywords: Corail stem; Femoral stems; Uncemented