Study Of CT Manifestation And Relationship With Knee Function After Patellar Dislocation Surgeries

Purpose: To observe the radiological manifestation and changes at follow-up after patellar dislocation triple-surgeris, as well as their relationship with knee function scores.Methods: Between 2007 and 2015, a total of 58 consecutive patients(63 knees) with recurrent patellar dislocation undergoing patellar dislocation triple-surgeries were enrolled in the study. All patients were followed up by CT and knee function scores at a minimum of 12 months. Radiological measurements on CT included patellar and femoral tunnel width, the position of femoral tunnel, patellar tilt angle, lateral patellar displacement, congruence angle, lateral patellofemoral angle, tibial tubercle-trochlear groove distance, patellar alta and degree of trochlear dysplasia. Compare the measurements within 3 days postoperative with that of the last follow-up. Additionally, we carried on a correlation analysis of CT manifestation with knee function of the last follow-up.Results: Compared with CT within 3 days postoperative, all CT measurements(mean±SD) of the last follow-up were found to be statistically different. Patellar and femoral tunnel width, patellar tilt angle, lateral patellar displacement, congruence angle and lateral patellofemoral angle proved to be larger and patellar height proved to be lower. For the outcome of the last follow-up, Kujala score did not differ from Lysholm score significantly. The degree of trochlear dysplasia had moderate minus correlation with Kujala score. Lateral patellar displacement and lateral patellofemoral angle had moderate minus correlation with Lysholm score. Furthermore, the positon of femoral tunnel in AP orientation had significant correlation with knee function scores. Other measurements showed no remarkable correlation with knee function scores.Conclusion: The changes of knees after patellar dislocation triple-surgeries in short-medium term could be observed by CT at follow-up, inc luding the enlargement of femoral and patellar tunnel, increasement of patellar tilt angle, lateral patellar displacement, congruence angle, lateral patellofemoral angle, and the decline of patellar height. The increasement in lateral patellar displacement and lateral patellofemoral angle, the high degree of trochlear dysplasia and the abnormal position of femoral tunnel could result in poor knee function postoperatively. Therefore, CT is useful to detect the patients who have underwent patellar dislocation triple-surgeries with patellar instability and poor function postoperatively, showing to be of great value for the assessment at follow-up.