Correlation between Patellar Tilt Angle, Femoral Anteversion and Tibial Tubercle Trochlear Groove Distance Measured by Computer Tomography in Patients with non-Traumatic Recurrent Patellar Dislocation.

Abstract

Introduction: Recurrent patellofemoral dislocation (RPD) is a disabling condition with a variety of anatomical risk factors. Its management remains difficult and controversial. Patients with RPD are known to have increased femoral anteversion (FA) and tibial tubercle trochlear groove (TT-TG) distance, but their effect on the patellar tilt angle (PTA) is less studied. Aims: The aims of this study are to compare PTA, TT-TG distance and FA between RPD patients and healthy controls and to establish a relation between these parameters and the type of surgery indicated for this pathology. Materials and methods: A total of 63 knees (57.1% females, 28.1±6.2 years), of which 33 from subjects with RPD and 30 from healthy controls, were assessed by computed tomography (CT) scan under supine position, with the measurement of TT-TG distance, FA and PTA. Results: The values of PTA, FA and TT-TG distance were significantly higher in the RPD group compared to the control group (CI 95% 9.52-11.64, CI 95% 5.87-11.8, CI 95% 6.44-9.72, respectively, with p value <0.0001 in all cases). In the RPD group, PTA significantly correlated to the FA (r=.53, p=0.001) and TT-TG (r=.39, p=0.02), while TT-TG correlated to FA (r=.53, p=0.001) too. Further analysis in the RPD group showed a significant correlation of PTA, FA and TT-TG (r=.96, r=.89, respectively, p=0.0001) when FA >25 degrees, but no significant correlation between TT-TG and FA or PTA when FA<25 degrees. Moreover, higher values of PTA and FA positively correlated with TT-TG distance (r=.44, r=.74, r=.20, p=0.03) when TT-TG was >20 mm, but no correlations were found between TT-TG and FA on less than 20 mm. Conclusion: In patients with RPD, FA, TT-TG and PTA have significantly higher values than controls. Higher PTA, TT-TG and FA are associated with an anteversion angle greater than 25 degrees and a TT-TG distance more than 20 mm, which might indicate a derotational femoral osteotomy to these patients in order to correct this pathology.