Anatomical Wrist Patterns on Plain Radiographs

Background: Interpreting the structure in the wrist is complicated by the existence of multiple joints as well as variability in bone shapes and anatomical patterns. Previous studies have evaluated lunate and capitate shape in an attempt to understand functional anatomical patterns. Objective: The purpose of this study was to describe anatomical shapes and wrist patterns in normal wrist radiographs. We hypothesized that there is a significant relationship in the midcarpal joint with at least one consistent pattern of wrist anatomy. Methods: Seventy plain posteroanterior (PA) and lateral wrist radiographs were evaluated. These radiographs were part of a previously established normal database, had all been read by a radiologist as normal, and had undergone further examination by 2 hand surgeons for quality. Evaluation included: lunate and capitate shape (type 1 and 2 lunate shape according to the classification system by Viegas et al.), ulnar variance, radial inclination and height, and volar tilt. Results: A significant association was found between lunate and capitate shape using a dichotomal classification system for both lunate and capitate shapes (p=0.003). Type 1 wrists were defined as lunate type1and a spherical distal capitate. Type 2 wrists had a lunate type 2 and a flat distal capitate. No statistically significant associations were detected between these wrist types and measurements of the radiocarpal joint. Conclusion: There was a significant relationship between the bone shapes within the midcarpal joint. These were not related to radiocarpal anatomical shape. Further study is necessary to better describe the two types of wrist patterns that were defined and to understand their influence on wrist biomechanics and pathology.