Electromagnetic sensor system may help assess distal radioulnar joint movement

The study is published in the Journal of Orthopaedic Surgery and Research.

Shintaro Mukohara and associates from the Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan carried out the present study to develop a noninvasive measurement method using a three-dimensional electromagnetic sensor system (EMS) to quantitatively assess and characterize the normal DRUJ movement in healthy volunteers.

The DRUJ movement was mimicked using both a block model and saw bone. Movement of the models was measured by EMS, and the accuracy and reproducibility of the measurements were assessed. In vivo measurement was performed in a sitting position with the elbow flexed and the forearm pronated.

One sensor each was attached to the distal radial shaft and the ulnar head. The examiners fixed the distal radius and the carpal bones, moved the ulnar head from the dorsal to the volar side and measured the dorsovolar translation.

The volar translation was measured by EMS and ultrasonography, and the correlation coefficient was calculated. The dorsovolar translation was evaluated in 14 healthy volunteers (7 men and 7 women) by three hand surgeons. The intraclass and inter-rater correlation coefficients (ICCs), the differences between the dominant and non-dominant sides and between men and women were assessed.

The results showed that the accuracy and reproducibility assessment results of the EMS showed high accuracy and reproducibility. In the comparison between EMS and ultrasonography, the correlation coefficient was 0.920.

The ICC (1,5) for the intra-rater reliability was 0.856, and the ICC (2,5) for inter-rater reliability was 0.868. The mean ulnar head translation and difference between dominant and non-dominant sides were 6.00 ± 1.16 mm (mean ± SD) and − 0.12 ± 0.40 mm, respectively.

Hence, there were no significant differences between any of the parameters.

Therefore, the authors concluded that "a new measurement method using EMS could evaluate DRUJ movement with high accuracy, reproducibility, and intra- and inter-rater reliability. In healthy volunteers, the dorsovolar ulnar head translation was 6.00 mm. The difference between the dominant and non-dominant sides was < 1.0 mm with no significant difference. EMS provided an objective, non-invasive, real-time assessment of dynamic changes in the DRUJ. These findings could be useful in the treatment of patients with DRUJ instability."