THE R MATHYS ISOELASTIC HIP REPLACEMENT, A FAILING PROSTHESIS

Abstract

The aim of this study was to review the results of the R. Mathys Isoelastic total hip replacement as for five years in this institution.

For the purposes of this study the patients were invited by letter to attend a review clinic. An examination of the hip was made and hip scores calculated. An up to date radiograph was performed and radiolucent lines assessed in comparison to the initial postoperative radiograph.

78 hips in 64 patients were identified from the records. 5 patients had died before review and 18 hips had been revised. Of the patients who died, none had died in the immediate postoperative period and all the deaths were of unrelated causes.

The revised hips were revised for aseptic loosening in 17 cases and infection in one. The mean time to revision was 53 months. All the loosening was femoral.

In the reviewed patients the mean length of follow up was 101 months.

The mean Harris score was 80.3. The mean Merle d’Aubigne score was 13.6. Significant lucent lines were noted in 2 acetabular components and 22 of 43 femoral components.

Life tables were constructed with both best and worst case scenarios. The end point for failure was taken as revision or the date revision was planned. A further set of life tables were constructed adding radiological signs of failure to the criteria.

Survivorship was, at best, 53% at ten years. If radiological failure is taken into account and lost to follow-up patients are counted as failures, “the worst case scenario”, the rate falls to 18% at ten years. A second important finding was that a large number of the patients were subjectively happy with their hip and had been discharged from clinical follow-up in spite of deteriorating radiographs

We feel that this is a poor implant, which needs ongoing clinical and radiological review, and cannot recommend its further use.