Failure of total condylar knee replacement. Correlation of radiographic, clinical, and surgical findings.

The authors reviewed 55 failed total condylar knee replacements, correlating the radiographic and surgical findings at removal or revision. Failure was due to infection in 20 cases, mechanical loosening in 18, instability without loosening in 10, malalignment without loosening in 4, a supracondylar fracture in 2, and unknown causes in 1. In infection with loosening or chronic infection, radiographs usually showed a wide, extensive radiolucent region at the cement-bone interface around one or more components without shifting, while in acute infection without loosening the radiographs were normal. In mechanical loosening, in addition to a similar lucent region, the prosthesis became tilted in 16 out of 18 cases. Most loosening involved tilting of the tibial component into the varus position with subsidence into the medial tibial plateau, collapse of the cancellous bone, and plastic deformation. Radiographs can be helpful in determining the reason for failure of a total knee replacement, which is important in planning surgery.