Abstract
Background Recent advances in the understanding of ulnar-sided wrist pathologies such as ulnar
abutment syndrome (UAS) have brought increased attention to the anatomy of the distal
radioulnar joint (DRUJ). Previous work established three anatomical variants of the
sigmoid notch (parallel, oblique, and reverse oblique). The reverse oblique DRUJ poses
theoretical risk of increased contact forces following ulnar shortening osteotomy,
a common method of treating UAS.
Purpose As prevalence of reverse oblique morphology has been under-reported, this study aims
to better define the prevalence of reverse oblique morphology in the adult population.
Methods Institutional Review Board-approved review of 1,000 radiographs over a 2-year period
was performed. Demographic data and radiographic measurements were recorded (ulnar
variance, notch inclination, and presence of arthritis). Correlation tests, a test
of proportions, a t-test, and linear and logic regression tests were used to examine associations between
ulnar variance, sigmoid inclination, sex, age, and presence of arthritis.
Results One thousand radiographs were analyzed revealing prevalence rates of: parallel—68%,
oblique—26%, and reverse oblique—6%. Females were significantly more likely to have
reverse inclination. No significant correlation was noted for morphology by age. Ulna
positive variance was negatively correlated with reverse inclination. DRUJ arthritis
was noted in 14% of patients. Higher sigmoid inclination was associated with higher
odds of presence of arthritis, adjusting for sex and age. Higher incidence of arthritis
was noted among patients with the oblique (20.8%) or reverse oblique (24.6%) compared
with parallel (10.5%) morphology.
Conclusion This series of 1,000 radiographs demonstrates a 6% overall prevalence of reverse
obliquity. This large dataset allows for better quantification of the prevalence of
DRUJ morphologies and determination of correlations that have clinical implications
for patients with ulnar-sided wrist pathology.
Level of Evidence This is a Level IV study.
Keywords
distal ulna - morphology - sigmoid inclination - ulnar variance - ulnar abutment syndrome
- ulnar shortening osteotomy
