Evaluation of patello-femoral joint congruency using three-dimensional computed tomography

Thirteen patients with recurrent dislocation of the patella and 11 normal volunteers were examined in this study. The patello-femoral congruency and patellar tracking were evaluated with three-dimensional computed tomography (3-DCT). Multiple transaxial knee CT images were obtained with the subjects in the supine position, with the quadriceps relaxed. Measurements were obtained at 0, 30 and 60°of knee flexion. The scans were transferred to the SurgiPlan (Teijin System Research and Development Institute) computer system, and the patello-femoral contact area was visualised at 0, 30 and 60°of flexion. Contact areas of the patello-femoral joints in the patients group was clearly located laterally at each angle of flexion, and was much smaller than that in normals. Lateral shift of the contact area and its reduced size was a distinguishing difference between normal and pathological cases. The analysis of the patellar tracking using the method described above has the advantage of visualising the contact area in vivo.