Radiographical definition of the proximal tibiofibular joint – A cross-sectional study of 2984 knees and literature review

BackgroundProximal tibiofibular joint (PTFJ) injuries are not uncommon but relatively understudied. This study evaluates the effectiveness of 2 radiographic methods in assessing the integrity of the PTFJ.Study designThis is a cross-sectional study of 2984 consecutive patients with knee X-rays done in a single institution over a 4-month period. A total of 5968 knee X-rays were assessed using 2 methods–[1] The direction in which the fibula points to in relation to the lateral femoral epicondyle on anteroposterior view and Blumensaat line on lateral view. [2] The degree of tibiofibular overlap as percentage of widest portion of the fibula head. Sensitivity and specificity of these methods in diagnosing a disrupted PTFJ are calculated. Variables including quality of X-rays, weight-bearing status of AP views and degree of knee flexion on lateral views are also recorded. Univariate analysis was carried out to investigate the association between variables using chi-square test for nominal data and student t-test for continuous data.ResultsThe fibular points towards the lateral femoral epicondyle on AP view in 94.4% of the patients and points towards the posterior half of the Blumensaat line on lateral view in 98.1% of the patients. Using this method, weight-bearing X-rays are significantly associated with the direction the fibula is pointing (p < 0.01) on the AP view and the degree of knee flexion is associated with the direction the fibula is pointing (p < 0.01) on the lateral view.The AP tibiofibular overlap ranges from >0% to <75% in 94.1% of the patients and the lateral tibiofibular overlap ranges from >0% to <75% in 84.5% of the patients.This method is associated with whether true orthogonal X-rays of the knees are taken (p = 0.048).ConclusionThe direction in which the fibula is pointing and the percentage of tibiofibular overlap are highly specific radiographic methods useful in defining the PTFJ. The first method requires a weight-bearing view on AP assessment and >20 degrees of flexion on lateral assessment. True orthogonal AP and lateral views are required for the second method to be used.