Dislocation of the polyethylene inlay due to anterior tibial slope in revision total knee arthroplasty

We report a case of dislocation of the polyethylene inlay in revision total knee arthroplasty. Eight days after revision arthroplasty due to a previous infection, the polyethylene inlay of a PCL- retaining cemented total knee arthroplasty dislocated at about 80° of flexion on the CPM machine. Lateral X-ray examination revealed an anterior slope of the tibial cut of 5°. Correction of the tibial slope to a posterior tibial slope of 7° reduced the forces on the posterior aspect of the inlay and no redislocation occurred. The mechanisms causing tibial inlays to dislocate in TKA are analyzed and discussed.