A Review of Factors Playing a Role in the Assessment of Ulnar Variance

[Context]Ulnar variance (UV) is attributed to the natural history of several wrist disorders. Thus, its reliable measurement is of considerable clinical importance. Several factors are proposed to affect the UV measures; the current study aimed at discussing these factors to further clarify their role in the evaluation of UV.[Evidence Acquisition]The evidence of the current review was derived from literature published in English in PubMed to identify papers discussing the factors affecting UV measurement. The title and abstract of the articles published prior to October 2017 were checked. After the exclusion of non-relevant studies, 16 articles were found eligible for investigation.[Results]Based on the available evidence, the perpendicular technique is the most reliable method of UV assessment. Magnetic resonance imaging (MRI) is also reported as the best imaging method for UV measurement. Moreover, the most increase in UV is expected when the position changes from relaxed supination to pronation and grip status. It seems that aging affects UV, at least until maturity, with a shift toward less ulnar minus position. In addition, ulnar plus wrist position seems to be more frequent in females. Repetitive minor wrist trauma can also change wrist radiologic parameters, especially ulnar variance.[Conclusions]Among several potential factors affecting the UV, the role of some factors such as positioning, imaging, and measurement technique are well defined, while the role of some others such as age and gender needs further clarifications in future investigations.