Abstract
The optimum design for the femoral component for cementless Total Hip Replacement is not known. We conducted an ethically approved, randomised and prospective trial to compare two radically different designs of fully hydroxyapatite (HA) coated femoral stems. We compared the original JRI Furlong stem with the Wright Anca fit stem which is more anatomical in design. The paper discusses the merits and disadvantages of these two stems. The same acetabular component was used in both samples. The only variable was the stem shape.
All patients placed on the senior author's waiting list for primary THR were asked if they would enter the trial. There were no restrictions for selection to the sample. Patients were then randomised for one of the two stems. All surgery was performed by or under the direct supervision of the senior author. The periprosthetic and perioperative fracture rates for the two stems were found to be significantly different at three years into the study and the trial was stopped. 337 patients had been entered into the trial, 211 females and 126 males.
191 patients had the JRI furlong hip implanted (57%) and 146 are in the Anca sample (43%).
The number of perioperative fractures in the Furlong group was 13 (6.8%)and in the Anca sample 22 (15.1%). This is statistically significant. The possible reasons for this difference are discussed.
Anatomical fit cementless stems require a more careful technique to avoid fracture during implantation and the shorter stemmed Anca hip proved less stable in the presence of a fracture necessitating further surgical intervention. It is still not certain whether the anatomical shape has long term advantages that may outweigh this initial disadvantage and the cohort of patients continues to be followed up.
