The most commonly used imaging parameters for evaluating distal radius fractures typically include volar tilt angle（VTA), ulnar variance, and radial height. As our understanding of the anatomy of the distal radius has deepened, additional imaging parameters such as anteroposterior distance (APD), teardrop angle (TDA), and capitate-to-axis-of-radius distance (CARD) have been proposed and applied in clinical practice.
Commonly used imaging parameters for evaluating distal radius fractures include: a：VTA；b：APD；c：TDA；d：CARD。
Most imaging parameters are suitable for extra-articular distal radius fractures, such as radial height and ulnar variance. However, for some intra-articular fractures, like Barton’s fractures, traditional imaging parameters may be lacking in their ability to accurately determine surgical indications and provide guidance. It is generally believed that the surgical indication for some intra-articular fractures is closely related to the step-off of the joint surface. In order to assess the degree of displacement of intra-articular fractures, foreign scholars have proposed a new measurement parameter: TAD (Tilt After Displacement), and it was first reported for the assessment of posterior malleolus fractures accompanied by distal tibial displacement.
At the distal end of the tibia, in cases of posterior malleolus fracture with posterior dislocation of the talus, the joint surface forms three arcs: Arc 1 is the anterior joint surface of the distal tibia, Arc 2 is the joint surface of the posterior malleolus fragment, and Arc 3 is the top of the talus. When there is a posterior malleolus fracture fragment accompanied by posterior dislocation of the talus, the center of the circle formed by Arc 1 on the anterior joint surface is denoted as point T, and the center of the circle formed by Arc 3 on the top of the talus is denoted as point A. The distance between these two centers is TAD (Tilt After Displacement), and the larger the displacement, the greater the TAD value.
The surgical objective is to achieve an ATD (Tilt After Displacement) value of 0, indicating anatomical reduction of the joint surface.
Likewise, in the case of volar Barton’s fracture:
The partially displaced articular surface fragments form Arc 1.
The lunate facet serves as Arc 2.
The dorsal aspect of the radius (normal bone without fracture) represents Arc 3.
Each of these three arcs can be considered as circles. Since the lunate facet and the volar bone fragment are displaced together, Circle 1 (in yellow) shares its center with Circle 2 (in white). ACD represents the distance from this shared center to the center of Circle 3. The surgical objective is to restore ACD to 0, indicating anatomical reduction.
In previous clinical practice, it has been widely accepted that a joint surface step-off of <2mm is the standard for reduction. However, in this study, the Receiver Operating Characteristic (ROC) curve analysis of different imaging parameters showed that ACD had the highest area under the curve (AUC). Using a cutoff value of 1.02mm for ACD, it demonstrated 100% sensitivity and 80.95% specificity. This suggests that in the process of fracture reduction, reducing ACD to within 1.02mm may be a more reasonable criterion
than the traditional standard of <2mm joint surface step-off.
ACD appears to have valuable reference significance for assessing the degree of displacement in intra-articular fractures involving concentric joints. In addition to its application in assessing tibial plafond fractures and distal radius fractures as mentioned earlier, ACD can also be employed for evaluating elbow fractures. This provides clinical practitioners with a useful tool for selecting treatment approaches and assessing fracture reduction outcomes.
Post time: Sep-18-2023
