Abstract
Background: The osteolysis in revision total knee arthroplasty was observed. The purpose of this study was to compare the prevalence and characteristics of osteolysis recognized in revision total knee arthroplasties between the failed mobile bearing and fixed bearing knees.
Methods: Eighty revision total knee arthroplasties were done between 1995 and 1998. The primary prosthesis that failed included thirty-four mobile bearing (Low Contact Stress) knees and forty-six fixed bearing knees of vary prostheses. At the time of revision surgery, all the interfaces between bone and prosthesis or cement were routinely checked and recorded for evidence of osteolytic resorption of bone. Preoperative radiographs were assessed independently by two authors for evidence of focal or severe periprosthetic osteolysis. The presence of the lesion was recorded. The demographic data included age and body weight was reviewed. The interval between the primary and revision surgery was recorded. The revision technique was reviewed. A statistical technique of chi-square test was applied in this study.
Results: Osteolysis was recognized in sixteen of thirty-four mobile bearing knees (47 per cent) with thirteen knees involved distal femur and in six of forty- six fixed bearing knees (13 per cent) with four knees involved distal femur. The incidence of osteolysis was statistically significant difference between the mobile bearing and fixed bearing knees (p< 0.05). An overall 28 per cent (twenty-two knees) incidence of osteolysis was identified intraoperatively. The overall incidence of osteolysis in distal femur was 21 per cent (seventeen knees). The average time interval from the primary surgery to revision was 108 months. All the knees were affected by osteoarthritis. The most common site of osteolytic bone resorption was the posterior femoral condyle.
Conclusions: Comparing to the fixed bearing knees, the mobile bearing (Low Contact Stress) knees were at increased risk for osteolysis in our series. Osteolysis occurred predominantly on the femoral side, especially adjacent to the prostheses in posterior condyle. Radiographic evaluation of osteolysis in distal femur is unreliable.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
