KINEMATIC CT OF THE PATELLOFEMORAL JOINT

OBJECTIVE. The purpose of this study was to determine if kinematic CT can be applied to the patellofemoral joint using current slip-ring CT scanner design in patients with anterior knee pain and thus a suspecte d patellar tracking disorder. SUBJECTS AND METHODS. Twenty knees in 18 patients with anterior knee pain were evaluated with kinematic CT. A single 10-sec exposure of the patellofemoral joint was obtained during active flexion and extension. Static nonkinematic and loaded kinemati c examinations were compared with unloaded kinematic studies in a subs et of patients. The changes in lateral patellofemoral angle and latera l shift were measured. Video cine viewing of patellofemoral motion was used to subjectively grade image quality and patellofemoral abnormali ties by consensus. RESULTS. Kinematic CT was successfully used in ail 20 knees. In nine knees studied with static nonkinematic and unloaded kinematic images, the lateral patellofemoral angle improved an average of 4 degrees on the kinematic images. In addition, lateral shift impr oved by an average of 3%, an improvement that was statistically signif icant (p = .01). In 10 knees studied with and without loading, the lat eral patellofemoral angle decreased an average of 3% with loading. No significant change was seen in lateral shift. In all patients, cine vi ewing wets thought to be more useful than single images. Cine viewing was of good or diagnostic quality in all 20 knees studied. Lateral pat ellar translation during extension was detected in eight of 20 kinemat ic studies. Lateral patellar tilting also was detected in eight of 20 kinematic studies. Narrowing of the articular space was detected in 12 of 20 knees. Six knees were determined to be normal. CONCLUSION, Kine matic CT with slip-ring technology is a new technique that can be easi ly performed on the patellofemoral joint. This technique shows promise as a tool for determining the cause of anterior knee pain.