CEMENTLESS TOTAL HIP ARTHROPLASTY WITH A CONTEMPORARY SECOND-GENERATION METAL-ON-METAL BEARING

Abstract

Metal-on-metal bearing was re-introduced with the aim of eliminating polyethylene wear and resulting complications of osteolysis and aseptic loosening in total hip arthroplasty (THA). However, authors of recent studies have reported periprosthetic osteolysis and aseptic failure following second-generation metal-on-metal THA. The purpose of this study is to report the results at a minimum of five years following cementless total hip arthroplasty with a contemporary metal-on-metal articulation. Our study included findings of histologic examination on periprosthetic tissues from revised hips and wear and roughness analysis of retrieved implants.

A consecutive series of 158 cementless THAs that were performed in 154 patients using a contemporary metal-on-metal bearing were assessed at a mean of 6.5 years (5 to 8). Their mean age at surgery was 53 years (21 to 80). The patients were assessed clinically with use of the Harris hip score, and the hips were assessed radiographically. Histological analysis was performed on specimens retrieved from the revised hips, and wear and roughness measurements were made for the explanted prostheses.

The average Harris hip score improved from 45 points preoperatively to 92 points at the final follow-up examination. There was no aseptic loosening of the femoral or acetabular components. One hip was revised because of recurrent dislocation and one was managed with two-stage re-implantation for deep infection. Thirteen hips (8%) had osteolysis; 11 had osteolysis localized within the greater trochanter and two had both femoral and ace-tabular osteolysis. Of these, five patients who had a persistent pain and osteolysis underwent revision operation for the consideration of bearing exchange to a ceramic-on-ceramic or ceramic-on-polyethylene combination. All these revised hips showed extensive synovial-like tissue hypertrophy and perivascular infiltration of lymphocytes on histological examinations. Annual volumetric wear rate measured on one retrieved femoral head was 1.04mm3/yr, and roughness measured on three retrieved femoral heads was consistently very low between 8nm and 117nm. After the revision surgery, all the patients noticed disappearance of pain as well as radiographic evidence of healing of the osteolytic lesion.

Our mid-term follow-up of cementless THA using a contemporary metal-on-metal bearing revealed an unexpectedly high rate of periprosthetic osteolysis possibly in association with metal hypersensitivity. In patients with persistent hip pain and osteolysis after contemporary metal-on-metal THA, surgeons should consider an exchange of the articulation surface to a ceramic-on-ceramic or ceramic-on-polyethylene combination because they can be cured only after an elimination of the source of hypersensitivity reaction.