79. ANATOMIC VARIATIONS OF THE ANTERIOR TIBIAL TUBEROSITY: CLINICAL IMPLICATIONS

Abstract

Purpose of the study: The form of the anterior tibial tuberosity (ATT) has not been described in anatomy studies. Insertion of the patellar tendon can, by its form, modify the lever arm of the extensor system and induce pathological conditions having an impact on the form of the apex or tip of the patella. The purpose of this work was to analyse the types of tibial tuberosities observed on the radiographs of 50 patients.

Material and method: Fifty patients were included in this prospective study. The form of the ATT was defined by two angles. These angles were measured on the strictly lateral x-ray. The ATT-shaft angle (ATT-d) was defined by the intersection between the anatomic axis of the tibial diaphysis and the anterior cortical of the ATT which corresponds to the insertion of the patellar tendon. The ATT-metaphysis angle (ATT-M) was defined by the angle between the tangents of the anterior metaphyseal cortical and the anterior cortical of the ATT. The height of the patella was also measured as described by Caton and Deschamps. The form of the patella on the lateral was described according to the Grelsamer criteria, and its form on the 30° axial view according to the Wiberg classification. The presence of trochelar dyplasia was determined using the Dejour method. The statistical analysis accepted p < 0.05 as significant. The coefficients of correlation R were calculated with a ½ log covariance matrix [1+R]/[1−R].

Results: The form of the ATT was given by the minimal value between the ATT-D and the ATT-M. This angle measurement revealed major variation. Three types of ATT were defined: type I 0≤ATT-M≤15 and ATT-D≤5, type II 15 < ATT-M < 20 and 5 < ATT-D < 10 and type III 20≤ATT-M 10≤ATT-D. There was an obvious correlation with the form of the patellar apex. The type III form of the patella was always associated with a type I ATT; there was a significantly association between patella type I and ATT type II and patella type III and ATT type I. There was no correlation with the height of the patella or with the form of the trochlea or the patella.

Conclusion: The form of the ATT is quantifiable and becomes a parameter to consider in the analysis of patellofemoral osteoarthritis.