Description
Objectives:
Metal parts of total knee arthroplasty (TKA) make it difficult to precisely analyze the information in bone and soft tissue around a knee with the three-dimensional modalities such as CT and MRI due to the beam-hardening artifacts. On the other hand, the alumina ceramic prosthesis causes little beam scatter and CT image artifact. This specific feature of ceramic allows us to examine a TKA concerning the lesion location, size, and identification of communication pathways with the joint space. The purpose of this study was to locate and measure any osteolytic lesions after TKA in patients with rheumatoid arthritis using CT.
Methods:
Twenty-five primary cemented alumina-ceramic TKAs with a minimum 10-year follow-up were evaluated using CT and analyzed to determine the location and volume of osteolytic lesions. This TKA system has an alumina ceramic femoral component, a titanium-alloy tibial component with a polyethylene insert, and polyethylene patella component. The mean age of the patients at the time of surgery was 54.1 years. The average time interval between surgery and the CT scan was 12.6 years. The osteolytic lesions on plain radiographs were also analyzed to determine if the detection rate was differed depending upon locations.
Results:
In the plain radiograph examination, 7 osteolytic lesions (2 femoral and 5 tibial lesions) were found in 6 of the 25 knees. A total of 31 osteolytic lesions (23 femoral and 8 tibial lesions) were identified in 12 of the 25 knees on CT. All lesions were present around the prosthetic rim and had a communication to the joint space. The mean size of osteolysis per knee was 2.1 ± 1.5 cc (range, 0.4-4.7 cc). Among the lesions detected on CT, only seven lesions were identified on plain radiographs. When comparing differences in detection rate on plain radiographs, lesions at posterior femoral condyle were significantly less detectable than other locations (p=0.00047).
Conclusions:
In alumina-ceramic TKA, CT can accurately detect osteolysis and its communication with the joint space, locate and measure lesion volumes. The present study demonstrated that plain radiographs are less sensitive than CT scans for detecting osteolysis. More than a half of lesions around the anterior flange or the tibial component were detected on plain radiographs, but none of the lesions was detected around the posterior femoral condyles. On the basis of the results of this study, most of the lesions were small, however, the incidence of osteolysis after TKA was higher than that reported in previous literatures.
