Distance mapping for quantifying contact surface area and inter-bone distance in wrist CT imaging: a comparative study of four methods

When assessing osteoarthritis, the congruency of articular surfaces and cartilage integrity are crucial. Static or dynamic CT scanning and subsequent bone-to-bone distance mapping enables a non-invasive evaluation of these factors. Distance maps visualize local inter-bone distances and its extent can serve as a representation of the contact surface area within a joint. A contact surface area can be defined by applying distance and angle thresholds between adjacent bones. These thresholds may affect the selected contact area and therefore influence distance measures. Several methods for distance map generation use different distance measurement approaches, with or without an angle threshold. The impact of the chosen method and thresholds remains unclear. This study evaluates the sensitivity to threshold settings of different methods in radioscaphoid, radiolunate, and scapholunate joints. Static 3D-CT scans of twenty healthy and eleven pathological wrists were analyzed. A mixed effect model was conducted to compare the sensitivity of different methods using particular angle and distance thresholds. The method combining perpendicular distance and angle thresholds was shown to be the least sensitive to changing threshold values, resulting in the smallest variations in observed contact surface area and bone-to-bone distances.