FRACTURE OF THE METAL TIBIAL TRAY AFTER KINEMATIC TOTAL KNEE REPLACEMENT - A COMMON-CAUSE OF EARLY ASEPTIC FAILURE

We reviewed 1567 elective knee replacements performed between 1980 and 1990, using either the Total Condylar prosthesis with an all-plastic tibial component, or the Kinematic prosthesis which has a metal tibial tray, The ten-year probability of survival was 92.1% for the Total Co ndylar design and 87.9% for the Kinematic, The difference tvas mainly due to 16 revisions required in the Kinematic series for fracture of t he metal base-plate. This was the most common cause of aseptic failure in this group. These fractures were strongly associated with a preope rative varus deformity (hazard ratio (HR) 8.8) and there was a slightl y increased risk in males (HR 1.9) and in osteoarthritic knees (HR 1.8 ). In the nine fractures which occurred within four years of primary i mplantation (group 1), failure to correct adequately a preoperative va rus deformity and the use of a bone graft to correct such a deformity were both strongly associated with fracture (HR 13.9 and 15.8, respect ively), In eight fractures which occurred more than five years after p rimary replacement (group 2) we could detect no significant risk facto rs. Early complications occurred in two patients after the 16 revision procedures for tray fracture. One had a deep infection and the other refracture of the tray.