Abstract
Aims: To study prospectively the characteristic migration of four different cemented femoral stems using Radiostereometry. Methods: 96 patients undergoing cemented femoral hip replacement for osteoarthritis were randomised to receive an Exeter (Howmedica Stryker), Ultima Tapered Polished Stem [TPS], Ultima straight stem [USS] (Johnson and Johnson) or Charnley Elite (Depuy/Johnson and Johnson) stem. RSA migration measurements were performed postoperatively and at 6,12,18 and 24 months post surgery using the UMRSA system. Results: Two signiþcantly distinct patterns of distal migration in the y direction (subsidence) were seen, compatible with previous studies. Tapered stems subsided rapidly by six months, Exeter 0.85mm (±0.15) UTPS 0.85mm (±0.15), stabilising by 2 years, Exeter 1.3mm (±0.35), UTPS 1.2mm (±0.25). The USS and Elite designs showed lower migrations of 0.1mm (±0.1) and 0.15 (±0.15) mm at six and 0.25mm (±0.15) and 0.35mm (±0.15) at 24 months. For migrations and rotations in other directions, differences were seen between prostheses with the same design concept. Whilst both the UTPS and Exeter exhibited posterior migration of the head, by 24 months this was expressed as a rotation about the transverse axis for the TPS and the axial axis for the Exeter. The Elite and USS differed in rates of posterior migration and varus tilt. Conclusions: Patterns of migration for stems with the same design concept may vary due to subtle differences in prosthesis shape. These variations produce a distinct migration Ç signature È for each stem.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
