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Cross-sectional Area Just Proximal to the Carpal Tunnel According to the Ulnar Variances

Positive Ulnar Variance and Carpal Tunnel Syndrome

Cha, Soo Min, MD, PhD; Shin, Hyun Dae, MD, PhD; Song, Seok Hwan, MD

doi: 10.1097/SAP.0000000000001640
Peripheral Nerve Surgery and Research

Purpose We evaluated the relationship between the area around the distal radioulnar joint according to the ulnar variances and the cross-sectional area using magnetic resonance imaging (MRI) scans in this prospective study of patients with carpal tunnel syndrome (CTS).

Methods From among a total of 243 patients who had been diagnosed with CTS between March 2012 and February 2017 at our hospital, 41 patients with positive ulnar variance were enrolled in group 1. As control groups, 39 healthy volunteers who underwent MRI evaluations were included in group 2 (neutral ulnar variance) and group 3 (negative variance). Basic demographic data, including age, sex, and body mass index, were recorded for all 3 groups. An area encompassing the contents of carpal tunnel (nerves/tendons) was designated as area “A,” and the area just beneath the subcutaneous fat was designated as area “B” at the levels of the lunate (L) and pisiform (P) on axial MRI. Ratios of these areas (“A/B at L” and “A/B at P”) were evaluated in terms of their correlations with ulnar variance.

Results Mean age, sex, and body mass index were not statistically different among the groups, respectively. Within each group, there was no difference between “A/B at L” and “A/B at P,” respectively. When comparing the 3 groups, “A/B at L” and “A/B at P” were all significantly decreased in group 1 than in other groups. Regardless of the group, ulnar length negatively correlated with both “A/B at L” and “A/B at P” ratios.

Conclusions We found a positive relationship between decreased cross-sectional area around the distal radioulnar joint and positive ulnar variance on radiologic investigation. These findings show the importance of variance in the positive ulna variance to the development of CTS.

From the Department of Orthopedic Surgery, Regional Rheumatoid and Degenerative Arthritis Center, Chungnam National University Hospital, Chungnam National University School of Medicine, Daejeon, South Korea.

Received December 23, 2017, and accepted for publication, after revision August 6, 2018.

This research was supported by Chungnam National University Hospital Research Fund, 2016 (to Soo Min Cha, Hyun Dae Shin, and Seok Hwan Song).

Conflicts of interest and sources of funding: none declared.

Reprints: Hyun Dae Shin, MD, PhD, Department of Orthopedic Surgery, Chungnam National University School of Medicine, 266 Munwha-ro, Jung-Gu, Daejeon, South Korea. E-mail: hyunsd@cnu.ac.kr.

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