We determined the distance from the radiocarpal joint to the distal flexor retinaculum margin.

This distance is a reliable carpal tunnel syndrome landmark from easily acquired regional measurements.

It predicts the distal flexor retinaculum margin in carpal tunnel release surgery.

The most frequent peripheral entrapment neuropathy is compression of the median nerve in the carpal tunnel, known as carpal tunnel syndrome. The most effective treatment is surgery, where the flexor retinaculum (FR) is divided. Nevertheless, after this operation, a significant number of patients suffer from persistent symptoms due to incomplete FR distal release. It may be difficult to identify the distal boundary of the FR due to the minimal skin incision. We aimed to identify an anatomical landmark to avoid incomplete distal FR release. The radiocarpal (RC) joint can be palpated, and lies in close proximity to the boundaries of the FR. Thus, the distance between the RC joint space and the distal FR margin – the RC-FR distance – could be a reliable and individual morphologic measurement from easily acquired regional anthropological measurements.

During this study, 39 radiocarpal regions of 23 embalmed cadavers were dissected, and measurements were taken. Linear regression corresponding to the ulnar length and the RC-FR distance was established.

The mean RC-FR distance from the RC joint space to the distal FR margin was 3.8 cm (95 % CI 3.5–4.0), and the range was 2.3–5.1 cm. This distance was 1.1 cm (95 % CI 0.8–1.4) longer in males than in females (p < 0.00001), and there were no side-specific differences. The individual projection of the distal FR margin in centimeters can be calculated by measurement of the ipsilateral ulnar length divided by 4 and reduced by 2.9, p < 0.005.

The side-equal and sex-specific position of the distal flexor retinaculum margin could be calculated from the palpable radiocarpal joint space based on the ipsilateral ulnar length.

Carpal tunnel syndrome

Flexor retinaculum

Radiocarpal joint

Median nerve

© 2022 The Author(s). Published by Elsevier GmbH.