Intraoperative imaging of the tibial plafond fracture: A potential pitfall

Study Design: Human tibial plafond cadaveric specimens were coronally secti oned and imaged to assess the accuracy of evaluation of ankle joint line co ngruity using anteroposterior radiography, Two interesting representative c linical cases are discussed. Objectives: To evaluate the validity of the routine use of anteroposterior radiographs to evaluate intra-operative ankle joint line congruity in circu mstances 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 seque ntially sliced into 0.5cm sections in the coronal plane. True anteroposteri or radiographs were taken with the specimen en bloc. Sequentially, the post erior slices were removed one by one, with an image taken after removing ea ch 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 l ine 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 poi gnant clinical cases demonstrating the clinical relevance of this informati on are discussed. Results: By sequentially imaging after removing coronal sections of the tib ial plafond we were able to accurately characterize the contribution of eac h portion of the plafond to the overall anteroposterior view. By primarily imaging the anterior portions of the plafond, with the posterior portions r emoved, the joint line image was virtually unchanged from the en bloc anter oposterior radiograph. However, removal of the anterior coronal sections ca used large variation in the joint line image. These observations demonstrat e that the anteroposterior radiograph of the tibial plafond characterizes t he anterior portion of the joint well, while it represents a poor assessmen t of the posterior portion of the joint. This was well illustrated in our c linical case presentations. Conclusion: In severe fractures of the tibial plafond multiple forms of int ernal and external devices are frequently used for fixation, In these circu mstances hardware may obscure the lateral view making it impossible to obta in 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 enti re joint line and, intra-operatively, may mislead the surgeon to accept a r eduction as anatomic when intra-articular incongruity still exists. Strict attention to pre-operative radiographs and the use of additional rotated vi ews may aid the surgeon in this setting to assess fracture reduction and jo int line congruence.