A Classification for Extensor Carpi Ulnaris Groove Morphology as an Aid for Ulnar Sided Wrist Pain

Distal ulna groove morphology is likely to have a significant role in extensor carpi ulnaris (ECU) tendon stability. The development of a robust anatomical classification system, would be beneficial to further research into ulnar sided wrist pain and would be of use in rationalising treatment regimes.

Cadaveric specimens as well as MRI scans of patients with non-specific wrist pain were analysed independently by 3 orthopaedic surgeons twice to test the integrity of the classification system. The following classification system was developed for the distal ulna groove; Flat = L-shaped slope, S slope = S shaped, Reverse C = C-shaped slope. Findings were then subjected to Fleiss Kappa statistical analysis to evaluate how robust the classification system was.

From the cadaveric arm of the study, 61 patients had their distal ulna groove morphology categorised according to types C, L, and S. For the MRI arm of the study 103 MRI scans were classified. ECU grove subtype C showed 8% dislocation compared to 33% and 47% for the L subtype and S sub type respectively.

Our classification system of ECU groove morphology will help identify different components to ulnar sided wrist problems and may help establish guidelines for treatment. This classification system has been validated for both cadaveric specimens and the MRI scans. It showed substantial agreement to almost perfect agreement in the data tested, thus proving good interand intra-observer reliability. It is a useful tool to help in further research into ulnar sided wrist pain and ECU instability, and may help develop further treatment strategies in the future.