Anconeus and pronation: a palpatory and ultrasonographic study

TL;DR

This study investigates the role of the anconeus muscle during pronation using palpation and ultrasonography, finding that it contracts alongside the pronator teres in most subjects during resisted movements.

Contribution

The study introduces a novel comparison of palpation and ultrasonography to assess anconeus muscle activity during pronation.

Findings

Anconeus contracted in 8/10 subjects during resisted full pronation by palpation.

Ultrasonography showed a fair agreement (Cohen’s kappa = 0.21) with palpation in detecting anconeus and pronator teres contractions.

Anatomic dissection confirmed the involvement of these muscles in pronation.

Abstract

Depending on its axis, pronation varies from the radius rotation around the steady ulna to the reciprocal adduction of the radius and abduction of the ulna. While there is no question that pronator teres is a central pronation agonist, anconeus’s role is not settled. The current investigation comparing palpation and ultrasonography in these two muscles during pronation along the axis capitulum-second digit evolved from a serendipitous finding in a clinical anatomy seminar.

Single-hand palpation and two-transducer ultrasonography over anconeus and pronator teres were used on ten normal subjects to investigate their contraction during pronation around the capitulum-second digit axis. These studies were done independently and blind to the results of the other. The statistical analysis between palpation and ultrasonography was performed with Cohen’s kappa coefficient and the χ2 test.

On palpation, on resisted full pronation, anconeus contracted in 8/10 subjects and pronator teres in 10/10 subjects. Without resistance, the corresponding ratios were 5/10 and 9/10. On two-transducer ultrasonography, the comparable ratios were 7/10 and 10/10, and 3/10 and 10/10. A fair concordance (Cohen’s kappa = 0.21) between palpation and ultrasonography in detecting the simultaneous status of anconeus and pronator teres during resisted full pronation. Anatomic dissection illustrated the elements involved.

Plain palpation confirmed by ultrasonography showed the simultaneous contraction of anconeus and pronator teres during resisted pronation in most of the studied subjects. The study suggests that palpation can be helpful in directly studying muscle activity during movement.

The online version contains supplementary material available at 10.1007/s00276-024-03399-6.

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