Combined Flexor-Pronator Mass and Ulnar Collateral Ligament Injuries

The anterior bundle of the ulnar collateral ligament (UCL) is the primary stabilizer against valgus stress in the elbow. However, when the UCL is compromised, the flexor-pronator mass becomes the primary dynamic valgus stabilizer of the elbow. Combined UCL and flexor-pronator mass injuries are a subset of medial elbow injuries sustained by overhead throwing athletes. Compared to athletes who suffer isolated UCL injuries, the group with combined UCL and flexor-pronator mass injuries tend to be older and have worse outcomes after surgical reconstruction. There are few studies describing these injuries in the orthopedic literature, and it is unclear what causes them to fail surgical management at a higher rate than UCL injuries alone. Treatment of this group requires a thorough history and physical exam, as well as a magnetic resonance imaging (MRI) for surgical planning. Based on the amount of flexor-pronator mass injury, different operative approaches may be warranted. It is important to counsel these patients about their prognosis, especially elite baseball players regarding their chances of returning to their previous level of play.