A new clinical test for radial tunnel syndrome--the Rule-of-Nine test: a cadaveric study.

PURPOSE: Radial tunnel syndrome refers to pain on the lateral aspect of the forearm as a result of compression of the posterior interosseous nerve within a tunnel with specific anatomical boundaries. Diagnosis of the condition is difficult because of its close association with lateral epicondylitis, which warrants different methods of treatment. Based on a cadaveric study, a new clinical test, the Rule-of-Nine test, is proposed to improve the diagnostic accuracy in radial tunnel syndrome. The test involves constructing 9 equal squares on the anterior aspect of the forearm and noting those squares where tenderness can be elicited.

METHODS: 19 upper limbs were dissected to delineate the path of the posterior interosseous nerve through the radial tunnel, and the relationship of the path of the nerve with the 9 squares.

RESULTS: A consistent mapping of the posterior interosseous nerve to the lateral column of 3 squares was observed.

CONCLUSION: The Rule-of-Nine test is proposed as a reliable method of diagnosing radial tunnel syndrome.