Purpose: To determine the lunate facet inclination (LFI), scaphoid facet inclination (SFI), and interfacet angle (IFA) of the distal radius on posteroanterior (PA) radiographs; evaluate the reliability of the IFA measurements; and define normative reference values for all 3 parameters.
Methods: The IFA was defined as the angle between the lines tangential to the scaphoid and the lunate facets. The reliability of the IFA measurements was investigated using 2 serial measurements made by 3 observers. Three parameters (the IFA, LFI, and SFI) were measured on PA wrist radiographs of 400 normal Caucasians. Between-side and -sex differences among the 3 parameters were analyzed statistically.
Results: The inter- and intraobserver reliability of the IFA measurements was excellent. The mean values were as follows: IFA, 20°; LFI, 14°; and SFI, 34°. Although no statistically significant difference was found between the right and the left wrists, sex-based analyses revealed significant differences between the wrists of women and men. Based on the standard distribution of IFAs, 3 groups of distal radii were defined as follows: slightly, moderately, and steeply angled.
Conclusions: The LFI, SFI, and IFA are easily measured radiographic parameters of the distal radius. Although a moderate correlation was evident between the IFA and the LFI, the IFA is a novel parameter to evaluate the carpal articular shape of the distal radius. The IFA measurement on PA radiographs is reliable.
Clinical relevance: The LFI has been accepted as a parameter for Madelung deformity and radiocarpal force transmission. The IFA may be considered as a parameter to evaluate radiocarpal coronal stability that could potentially be affected by changes in bifacet curvature.
Keywords: Distal radius; inclination; interfacet angle; lunate facet; scaphoid facet.
Copyright © 2020 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.
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