Radiographic Determination of the Distal Ulnar Diaphyseal Angle

Purpose Characterizing the distal ulnar diaphyseal angle (DUDA) may be important for anatomic recreation of the distal ulna during ulnar shortening osteotomy procedures using conventional straight plates. This study characterized the DUDA and determined side-to-side, age, and sex effects on DUDA magnitudes and locations. Methods Retrospective analyses of bilateral wrist radiographs were performed on 60 patients. The DUDA was defined as the angle of intersection between a line passing through the center of the distal ulnar metadiaphyseal region, in line with the landmarked long axis of the ulna, on a lateral radiograph. This inflection point was measured from the most distal aspect of the ulnar head and recorded as the DUDA tip-to-apex distance (TAD). Rater reliability was determined using the intraclass correlation coefficient. Results WefoundDUDAs in 94% of radiographs. The meanDUDAanglewas 5.6 degrees +/- 2.6 degrees and the mean TAD was 45.3 +/- 9.5 mm. The Pearson correlation coefficients for side-to-side comparisons were 0.47 for the DUDA angle and 0.69 for the TAD. For male and female patients, the mean DUDAs were 5.4 degrees +/- 2.3 degrees and 5.9 degrees +/- 2.9 degrees, respectively, and the mean TADs were 47.8 +/- 9.7mm and 41.7 +/- 7.9mm, respectively. The DUDAangle and TAD had negligible associations with age (r = -0.15 and -0.08, respectively). At 0.74 (95% CI, 0.58e0.85), interrater reliability was good. At 0.93 (95% CI, 0.88e0.96), intrarater reliability was excellent. Conclusions We demonstrated DUDAs, representing valgus deviations from the center axis and anteroposterior views of the ulna. Contralateral lateral wrist radiographs are moderate to strongly reliable in determining a DUDA. Rater reliability was good to excellent. Clinical relevance Re-creation of the DUDA may benefit procedures such as ulnar shortening osteotomy, fractures, or malunion by contributing to knowledge of distal radioulnar joint biomechanics. (J Hand Surg Am. 2022;47(10):1015.e1-e9. Copyright (c) 2022 by the American Society for Surgery of the Hand. All rights reserved.)