Medial: Flexor-Pronator Tendon Injury

Introduction

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  The flexor-pronator muscle mass at the medial side of the elbow provides dynamic stability against valgus forces. Flexor-pronator tendon degeneration occurs with repetitive forced wrist extension and forearm supination during activities involving wrist flexion and forearm pronation.

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  Athletes may be particularly symptomatic during the late cocking or early acceleration phases of the throwing motion.

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  Nonsurgical management is the mainstay of treatment, and typically includes activity modification, nonsteroidal antiinflammatory drugs, and corticosteroid injections.

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  Recent studies have investigated the impact of emerging modalities such as extracorporeal shock wave therapy and platelet-rich plasma.

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  Surgical treatment via open techniques is uncommon and is typically reserved for patients with persistent symptoms.

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  Progressive return to sport can be enhanced with the use of activity-specific rehabilitation and equipment modifications.

Epidemiology

Despite an overall prevalence of 1%, medial epicondylitis may affect as many as 3.8% to 8.2% of patients in occupational settings ( ). Medial epicondylitis typically occurs in the fourth through sixth decades of life and is a result of common flexor tendon (CFT) microtrauma and degeneration. Men and women are equally affected ( ).

The differential diagnoses for medial-sided elbow pain can include ulnar neuritis, tendinopathy, ligamentous instability, intraarticular pathology, and trauma. A thorough history and physical examination are critical to determine the likelihood of medial epicondylitis. In athletes, this condition is typically associated with overhead throwing, golf, or tennis; however, in the literature, it has been associated with other sports, including football, weightlifting, and bowling ( ). Medial epicondylitis is also commonly found in occupational settings, especially those involving repetitive forceful grip, manual handling of loads of 44 lb (20 kg), or exposure to constant vibratory forces at the elbow ( ).

Anatomy

The flexor-pronator tendon is the confluence of five muscles of the forearm: the pronator teres (PT), flexor carpi radialis, palmaris longus, flexor carpi ulnaris (FCU), and flexor digitorum superficialis ( Fig. 28.1 ). It is approximately 3 cm long and, in most elbows, crosses the ulnohumeral joint medially. The tendon attaches to the medial humeral epicondyle anteriorly and attaches proximally to the anterior bundle of the ulnar collateral ligament (UCL), with the fibers parallel to the UCL ( ). The CFT, particularly the ulnar head of the PT, also becomes confluent with a hyperplastic section of the anteromedial joint capsule.