The femoral component in total hip arthroplasty : results of uncemented and cemented fixation

Abstract

There is no general agreement on whether hip prostheses should be implanted with or without cement. In Sweden over 90% of primary hip replacements are performed with the use of cement while in other countries uncemented prostheses are more common. In this thesis the clinical and radiographic outcome of three types of femoral components were evaluated in five studies. The Merle d'Aubigne- Postel-Charnley score was used for the clinical evaluation. This score has six grades for each of the parameters evaluated, where grade six refers to the normal situation.

In the first study a cemented femoral component was used, the Harris Design 2 prosthesis (HD2). From a cohort of 126 hip replacements performed between 1983 and 1985, 89 hips with the original prostheses in place could be followed for an average of nine years. The mean age of the patients at the time of the surgery was 68 years. Two of the initially 126 implanted femoral components were revised because of aseptic loosening. According to Kaplan-Meier analysis, the ten year survival rate for the stem was 98%. For the 89 hips with a follow-up of seven years or more the average Merle d'Aubigne-Postel- Charnley score for pain at the last follow-up was 5.3, and 78% could ambulate indoors and 36% outdoors without support.

The second study focused on an early type of uncemented femoral prosthesis relying on bone ingrowth for fixation, the Lord prosthesis. It was used in 114 hip replacements between 1979 and 1984. The mean age of the patients at the time of the surgery was 57 years. There were a total of nine femoral revisions in this series, two were caused by infection. Excluding infections, there was a 94% survival of the femoral component at 13 years after surgery. Sixty-nine hips had a radiographic follow-up of ten years or more with the initially implanted stem in place and were not planned for revision at last follow-up. The average Merle d'Aubigne-Postel-Charnley score for pain at last follow-up for these 69 hips was 5.2, and the score for function was 4.5.

In the remaining three studies a more modem uncemented femoral stem was used, the Taperloc prosthesis. In the first of these three studies the diagnoses were mixed and the mean age of the patients at the time of the surgery was 61 years. In the second study all patients had been diagnosed with degenerative osteoarthritis and were 80 years or older at the time of the surgery. In the third study all patients had the diagnosis rheumatoid arthritis and the mean age was 55 years. The average follow-up period in these three studies was 11, 5 and 8 years respectively; the Merle d'Aubigne-Postel-Charnley score for pain at the last follow-up was 5.5, 5.7 and 5.7, and for function 5.1, 5.2 and 5.3. There was no femoral revision for loosening in any of these three studies.

In summary all three prostheses showed good to excellent clinical results. The radiographic evaluation for the HD2 and the Taperloc prostheses did not give any cause for concern however, the Lord prosthesis sometimes demonstrated pronounced porosity of the femoral bone surrounding the prosthesis. The findings indicate that uncemented fixation can be satisfactory even in populations that are suspected to be at risk for prosthesis loosening or failure of bone ingrowth because of a presumed inferior bone quality.