The ESOP-HA modular cementless femoral stem: a study of the results of 165 hip arthroplasties with a minimum of 10-year follow-up

Abstract

The authors report on more than 10 years’ experience of using a cementless femoral stem, with a two-piece modular design, for indications of primary prosthetic replacement. One hundred and sixty-five prostheses, inserted between 06/11/1991 and 31/12/1994, were reviewed. No patient was lost to follow-up. The probability of 10-year survival of these hip prostheses was assessed using the actuarial Kaplan–Meier method (the endpoint was revision of the arthroplasty regardless of the reason: failure of the femoral or acetabular component, fracture of one piece of the implant etc.). The mean age of the 165 patients (84 women, 81 men) was 64 years. The clinical results were excellent or good in 87.2% of hips. There was no instance of post-operative thigh pain (apart from one case), because of the primary stability of the hydroxyapatite-coated metaphyseal part where stress transmission occurs, while the diaphyseal part, selected in accordance with requirements and smaller in diameter than the femoral canal, remained free in the diaphysis. No significant difference in the results was noted in accordance with the pattern of femoral anatomy encountered; however, the cylindrical femur yielded slightly inferior results (PMA score). Radiological follow-up showed that femoral fixation had been obtained, generally accompanied by obvious signs of bone fixation (endosteal ossification, radiolucencies indicating condensed bone in the smooth zone). A high number of cortical changes was not noted. Two stems were the cause of revision surgery, one because of thigh pain without sealing, the other because the stem fractured. Six acetabular implants were removed without interfering with the femoral stem, because of localised osteolysis around an expandable peg. Two other acetabular implants were replaced: one because poor positioning resulted in recurrent luxation and the other for premature wear of the polyethylene after 7 years. The grounds for revision were failure of the acetabular implant in 8 cases out of 10. Thus, there is sufficient justification for the use of this modular two-piece stem, which has fulfilled its purpose in the majority of patients, enabling us to extend with confidence indications for the cementless stem to all the anatomical types of femur encountered. Our series of patients included almost 78.7% of what are known as “normal” femurs, but in the remaining cases (21.3%) or in more than one in five instances, the modular stem made it possible to extend the indications for a cementless prosthesis to all the patterns of femur encountered, in particular to young adults, who often have femoral dysplasia or a cylindrical femur. The survival curve reflects the life of the implant: implant survival is 96.3%. If acetabular revisions are not included it is 98.8%. Conclusions: A modular system then, consisting of a metaphyseal and diaphyseal part, appears to be a first-rate component which optimises the indication for implantation of a cementless femoral prosthesis in order to obtain the correct performance of a medical service as the survival curve demonstrates.