Evaluation of the patellofemoral joint with kinematic MR fluoroscopy.
OBJECTIVE: The aim of this study was to evaluate the diagnostic effectiveness of kinematic magnetic resonance fluoroscopy (KMRF) on patients with patellofemoral incongruency. MATERIALA AND METHODS: 17 patients (20 knees) and 10 healthy volunteers (20 knees), all men (mean age 29.4 years, S.D. 9, range 16-50), were included to our study. Only male subjects were studied because of potential biomechanical differences between sexes. KMRF was used to perform kinematic MR imaging of patellar alignment and tracking in 10 healthy subjects and 17 patients with a provisional clinical diagnosis of abnormal patellofemoral joints. The patellofemoral joints were examined with the knee in different angles of active flexion. At each knee position, real time kinematic and axial MRF image was used to focus on the sagittal plane, followed by an axial image focused through the middle of the patella. Three angles were measured: patellar tilt angle (PTA), sulcus angle (SA) and congruence angle (CA). RESULTS: Five patterns of malalignment were identified and studied. Two patellofemoral joints were normal, 10 had lateralization of the patella, 2 had patellar tilt, 2 had lateralization and patellar tilt (i.e. excessive lateral pressure syndrome) and 4 had medialization of the patella. CONCLUSION: KMRF is an effective method in evaluating patellofemoral incongruency. Short time duration of investigation, ability to get nearly real time images, suitable temporal contrast resolution and investigation from very different angles of knee are important advantages of the method.