Abstract
Introduction: Some reports have suggested an unacceptable failure rate of Elite Plus stem in the medium term. We have previously argued that other measurements must be made in addition to RSA in order to assess reasons for abnormal migrations. This 3-year RSA study of Elite Plus stems assessed the migration pattern and factors that influenced it.
Method: Twenty five patients (23 OA, 2 RA, mean age 60.4 years (37–81)) underwent Elite Plus THR (single surgeon). A-P radiographs were assessed for cementing technique, and measurements (canal widths, stem orientation, cement thickness etc) were taken using CAD software. Activity score and BMI were also recorded. Multiple factors were assessed for correlation with the main components of migration.
Results: One patient’s stem centroid migrated proximally (due to valgus rotation about the shoulder) and the mean subsidence of the others was 0.297 mm at 36 months. Mean internal rotation and posterior head migration (25 patients) at that time were: 1.42° (CI: 0.99° to 1.86°) and 0.801 mm (CI: 0.526 mm to 1.076 mm), neither being significantly different from migrations at 24 months. One patient’s stem migrated continuously. By 36 months, it had subsided 1.279 mm and internally rotated 4.2°. Some significant correlations (p < 0.05, rho > 0.6) were 3M and 36M subsidence with proximal-medial cement thickness; effective offset with 36M medial migration.
Discussion: The one patient with continuous high migration had the highest activity level. This was corroborated by a wear measurement of 3.5 mm in the contralateral (Charnley) hip which had been in place for 9 years (assuming the head was not scratched). If RSA, 3 years postoperatively, can predict future outcome, the 4% failure rate is similar to the ten year results of the Charnley hip.
Correspondence should be addressed to The Secretary, BHS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
