Study Design: Human tibial plafond cadaveric specimens were coronally sectioned and imaged to assess the accuracy of evaluation of ankle joint line congruity using anteroposterior radiography, Two interesting representative clinical cases are discussed. Objectives: To evaluate the validity of the routine use of anteroposterior radiographs to evaluate intra-operative ankle joint line congruity in circumstances where lateral radiographs are infeasible due to obscuring internal or external hardware. Methods: Eleven frozen human cadaveric lower extremity specimens were used in this study. At the level of the tibial plafond, the specimens were sequentially sliced into 0.5cm sections in the coronal plane. True anteroposterior radiographs were taken with the specimen en bloc. Sequentially, the posterior slices were removed one by one, with an image taken after removing each section. The process was then repeated by removing the anterior sections sequentially with intervening radiographs, Each series of anteroposterior radiographs was then evaluated to characterize which portion of the joint line on the whole specimen view had been contributed by each of the sections. This then allowed us to make inferences about the evaluation of the joint line if it had been derived solely by anteroposterior radiography. Two poignant clinical cases demonstrating the clinical relevance of this information are discussed. Results: By sequentially imaging after removing coronal sections of the tibial plafond we were able to accurately characterize the contribution of each portion of the plafond to the overall anteroposterior view. By primarily imaging the anterior portions of the plafond, with the posterior portions removed, the joint line image was virtually unchanged from the en bloc anteroposterior radiograph. However, removal of the anterior coronal sections caused large variation in the joint line image. These observations demonstrate that the anteroposterior radiograph of the tibial plafond characterizes the anterior portion of the joint well, while it represents a poor assessment of the posterior portion of the joint. This was well illustrated in our clinical case presentations. Conclusion: In severe fractures of the tibial plafond multiple forms of internal and external devices are frequently used for fixation, In these circumstances hardware may obscure the lateral view making it impossible to obtain adequate lateral radiographs to assess fracture reduction and joint line congruity, In this scenario, the anteroposterior radiograph is frequently relied upon to confirm the anatomic relationship of the displaced fragments. However, this view fails to accurately characterize reduction in the entire joint line and, intra-operatively, may mislead the surgeon to accept a reduction as anatomic when intra-articular incongruity still exists. Strict attention to pre-operative radiographs and the use of additional rotated views may aid the surgeon in this setting to assess fracture reduction and joint line congruence.
