Critical evaluation of anterior drawer measurement methods in the ankle

Anterior drawer testing has been used to assess the integrity of the lateral collateral ligaments, most notably the anterior talofibular ligament. Various radiographic measurement methods have been designed to assess sagittal plane talar displacement under stress. This investigation examined the anterior drawer test in 8 fresh frozen lower extremity cadaver specimens. Each specimen was mounted on a fabricated test frame and instrumented with a linear variable displacement transducer to directly measure talar displacement during stress application. Lateral radiographs were taken before and during stress application. Two radiographic measurement techniques (concentric circle and plafond to dome), each corrected for magnification effect, were compared with directly measured talar displacement values with the foot placed in 20 degrees plantar flexion. There were no significant differences between talar displacements measured directly and radiographically using the concentric circle method. Significant differences were found between directly and radiographically measured displacements using the uncorrected plafond to dome method. Subtracting the unstressed from the stressed tibiotalar distance for the plafond to dome method resulted in no significant difference from directly measured talar displacement values. It is not necessary to correct talar displacement values obtained when using the concentric circle method.