STRESS RADIOGRAPHY AND STRESS EXAMINATION OF THE TALOCRURAL AND SUBTALAR JOINT ON HELICAL COMPUTED-TOMOGRAPHY

The main objective of this study was to compare subtalar inversion str ess views using the Broden view with inversion stress views on helical computed tomography (CT). One of the drawbacks of routine radiography is the imaging of three-dimensional structures In a two-dimensional p lane. We investigated whether the use of helical CT would lead to a mo re objective and clearer measurable method to determine the amount of tilt in the subtalar joint. A group of 15 patients with unilateral chr onic instability complaints and clinically suspected subtalar instabil ity was examined. The contralateral asymptomatic foot was used as cont rol. A variable amount of subtalar tilt (range, 4 degrees to 18 degree s) was demonstrated in all cases on stress radiographs, without findin g significant difference between the symptomatic and asymptomatic feet , However, contrary to the findings at the talocrural level, subtalar tilt was found in none of the patients using helical CT. Thus, we now doubt that the tilt seen during stress examination using the Broden vi ew is the true amount of tilt, It may be that the lateral opening, see n on these radiographs, largely results from imaging two planes that h ave made a translatory and rotatory movement relative to each other in an oblique direction. It is concluded that the Broden stress examinat ion might not be useful for screening patients with subtalar instabili ty. Associated anomalies not visible on the radiographs were detected by helical CT. In four cases, narrowing of the articular cartilage and irregular and hypertrophic bone formation at the middle facet joint o f the subtalar joints were found. It. is likely that these changes cau se disturbance of function of this joint and it is suggested that the subjective complaint of instability with ''giving way'' is not only ca used by hypermobility, but can be caused by other disturbances of norm al motion.