[Evaluation of patello-femoral joint congruity following total knee arthroplasties].

OBJECTIVES: Complications associated with the patellar component have an important place for revision procedures following total knee arthroplasty (TKA). We evaluated the patello-femoral congruity both clinically and radiologically after TKAs performed with polyethylene patellar components. METHODS: The study included 60 knees of 55 patients (45 females, 10 males; mean age 66 years; range 33-82 years). Clinically, all patients were evaluated with respect to pain, knee functions, and range of motion of the knee joint. Antero-posterior, lateral, and patellar tangential radiographs were obtained. According to the tangential radiographs, the patients were divided into three groups; normal (group A), abnormal angular values without subluxation (group B), and the existence of subluxation, dislocation, or a fracture (group C). Patellar height, variations in the joint line, and patellar coverage by the component were measured on lateral radiographs. Patients with normal patellar congruity and patellar subluxation were compared. The mean follow-up period was 40 months (range 12 to 88 months). RESULTS: No significant differences were found between the three groups with respect to pain and range of motion of the knee joint; however, functional scores differed significantly (p=0.019). Radiologically, the mean valgus angles were not significantly different. According to the location of the patellar component on tangential radiographs, group A, group B, and group C included 39 knees (65.0%), 11 knees (18.3%), and 10 knees (16.7%), respectively. Measurements on lateral radiographs did not yield significant differences between patients with normal patellar congruity and patellar subluxation. CONCLUSION: Patellar subluxation should be investigated on tangential radiographs following TKA because lateral radiographs of the knee fail to show patello-femoral problems.