This is a cadaveric study designed to evaluate the inherent stability provided by the flexor pronator muscle mass to elbow valgus stability in overhead throwing athletes. The goal of the study was to evaluate the relative contribution of each muscle in the flexor pronator group to elbow stability at both 45 degrees and 90 degrees of elbow flexion. The authors used fresh frozen cadaveric specimens with both intact and completely sectioned medial collateral ligaments.
Results demonstrate that all of the flexor pronator muscles caused a significant elbow varus moment at both 45 degrees and 90 degrees when loaded individually. Of the flexor pronator muscles, the flexor carpi ulnaris, flexor digitorum superficialis, and flexor carpi radialis function as dynamic stabilizers of the medial side of the elbow. The muscle that appears to have the greatest stabilizing effect is the flexor carpi ulnaris.
The authors also found that on the extensor side of the forearm, the extensor carpi ulnaris and extensor digitorum communis increased medial collateral ligament strain and elbow valgus moment.
These findings indicate that the athlete with medial collateral ligament dysfunction may incorporate the flexor carpi ulnaris amongst the flexor pronator muscle groups. Action of the FCU, FDS and FCR decrease medial ligament strain. In addition, these findings suggest that ECU and EDC strengthening may increase medial collateral ligament strain.