The pathogenesis of osteolysis in two different cementless hip replacements

Surveillance of Arc2f polyethylene after 15 years of implantation

BACKGROUND

To investigate the behavior of Arc2f polyethylene (PE) component after a minimum of 15 years post implantation and its possible reasons for failure.

METHODS

Between January 1988 and March 1995, 557 cementless total hip arthroplasties were performed in 578 patients. A total of 435 patients (450 hips) were followed up for 18.6 years (range 15-22).

RESULTS

At 10 years follow-up no cup needed revision surgery. After 15 years of implantation, we observed massive PE wear in 140 cups (31%) with large osteolytic lesions. A revision procedure was performed in all cases. Exchange only of the PE liner was sufficient in 78 cases, whilst in 59 the cup was also revised. PE insert thickness and the type of prosthetic head were found to be related to PE wear.

CONCLUSIONS

We postulate that the massive failure seen is attributed to the manufacturing of the PE insert. We advocate following all patients that have an implant lasting a decade after implantation for routine monitoring to identify those at risk for accelerated PE wear.

Measurement of bone defects adjacent to acetabular components of hip replacement

Computed tomography can assist in the detection of periprosthetic osteolysis, but it has not been used to measure the actual volume of bone defects adjacent to hip replacement components because of the scanning artifact caused by metal. The aim of the current study was to develop a spiral computed tomography technique that provides precise and reliable volumetric measurement of bone defects adjacent to uncemented metal-backed acetabular components. Computed tomography scans were taken of small and large defects of known volume created in the ilium in a bovine hemipelvis and a pelvis from a cadaver. Scans were analyzed by two independent observers. The computed tomography operating conditions were determined that enabled volumetric measurements and that were accurate to within 96% for small and large defects and precise to greater than 98% for small and large defects. This computed tomography technique has the capability to measure accurately and precisely the volume of bone defects in the ilium adjacent to metal-backed acetabular components. This technique has clear advantages over plain radiographs. It will allow investigation of the natural history of osteolytic lesions, enhance preoperative planning, and improve monitoring of the outcomes of treatments of osteolysis.