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.

A and B, Photographs of a cadaver elbow demonstrating the ulnar nerve (UN); medial epicondyle (MEC); and the anatomy of the flexor-pronator muscles, including the pronator teres (PT), flexor carpi radialis (FCR), palmaris longus (PL), flexor digitorum superficialis (FDS), and flexor carpi ulnaris (FCU).

Reproduced with permission from Otoshi K, Kikuchi SI, Shishido H, Konno SI. The proximal origins of the flexor-pronator muscles and their role in the dynamic stabilization of the elbow joint: an anatomic study. Surg Radiol Anat. 2014;36(3):289-294.

Mechanism of Injury

Most authors commonly accept that the principal mechanism of injury is repetitive eccentric loading of the muscles performing wrist flexion and forearm pronation, combined with valgus overload at the elbow ( ). Strain of the medial elbow with a valgus overload moment, which occurs with overhead throwing, stimulates dynamic stabilization of the joint via eccentric contraction of the CFT. Simultaneous wrist flexion or forearm pronation during ball release may produce even greater eccentric stress on the tendon ( ). Historically, the PT has been identified as the primary dynamic stabilizer and the most likely musculotendinous unit to be injured in medial epicondylitis. Recent cadaver studies, however, have implicated every musculotendinous unit except the palmaris longus ( ).

Repetitive supraphysiologic stress on the tendon eventually results in microtrauma and degeneration. Histopathologic examination has revealed a staged process of pathologic tendon change ( ). Initially, repetitive trauma results in peritendinous inflammation. Continued injury results in angiofibroblastic hyperplasia, an invasion of vascular and fibroblastic elements into the tendon. This results in structural breakdown and irreparable fibrosis or calcification. Activity causing such pathology to the CFT can eventually transfer forces deeper to the UCL, which mirrors CFT fiber orientation and histologic anatomy ( ).

History

Patients typically present with persistent medial-sided elbow pain that is often localized to the medial epicondyle, with radiation into the proximal forearm. Elbow pain is exacerbated by activity and is particularly bothersome during the late cocking phase in overhead throwing or during early acceleration for the thrower, tennis player, or golfer ( ). Although less common, the patient history may include an acute trauma to the elbow resulting in an avulsion of the CFT. More commonly, the pain is characterized by an insidious onset, with persistence despite rest ( ).

Physical Examination

Physical examination may detect tenderness 5 to 10 mm distal and anterior to the medial epicondyle that is accompanied by soft tissue swelling ( ). Resisted wrist flexion, forearm pronation, or forceful grip may be weakened compared with that of the contralateral side and may exacerbate elbow pain ( ). Patients may present with an elbow flexion contracture secondary to pain and guarding; however, most patients present with normal passive and active range of motion (ROM) at the elbow and wrist. The neurovascular examination is typically unremarkable.

Patients suspected of having medial epicondylitis should be examined for other pathologies of the ipsilateral arm. Up to 84% of occupational patients may have concomitant work-related disorders, such as carpal tunnel syndrome, lateral epicondylitis, or rotator cuff tendinitis ( ). Overhead athletes must be examined for valgus instability secondary to an injury to the UCL. Evaluation of the UCL is performed by applying valgus stress to the elbow in 30 degrees of flexion, with the forearm pronated and the wrist flexed.

Ulnar neuritis is another common concomitant pathology. In patients with suspected ulnar neuropathy, the examination should include two-point discrimination in the ulnar sensory distribution and a comparison of the hypothenar bulk of the symptomatic and asymptomatic extremities. A positive Tinel sign can indicate compression of the ulnar nerve. Proximally, overdevelopment of the medial head of the triceps may compress the nerve against the medial intermuscular septum ( ). Distal to the medial epicondyle, the ulnar nerve travels under the arcade of Struthers and through the bifid FCU arcade distally, which may be inflamed and irritate the passing nerve ( ). However, a positive Tinel sign may be found anywhere along the length of the nerve. Sensory changes in the ulnar hand may be reproduced by applying stress to an irritated ulnar nerve via the elbow flexion test, which is performed with maximal elbow flexion, forearm pronation, and wrist extension for 30 to 60 seconds ( ). The presence of ulnar nerve subluxation should also be noted during examination, especially in patients who report a popping sensation during daily activities or overhead throwing. Ulnar neuritis with or without subluxation may exacerbate medial-sided elbow pain; therefore, treatment modalities specifically for medial epicondylitis provide inadequate relief. Patients with neurologic complaints or findings should also be examined for signs of cervical radiculopathy, particularly of the C6 and C7 roots, because these patients may be at increased risk of developing medial epicondylitis secondary to forearm muscle imbalance ( ).

Imaging

In addition to a thorough patient history and physical examination, radiologic studies can support a diagnosis of medial epicondylitis. Although most radiographs demonstrate normal findings, up to 25% may show evidence of calcification of the CFT or UCL ( ). Ultrasonography may be a cost-effective modality for visualizing CFT tendinosis and pathologic change. In a small series, showed that a sonogram performed by a radiologist had sensitivity, specificity, and positive and negative predictive values of 90% for diagnosis of medial epicondylitis. The authors most commonly discovered hypoechoic or anechoic areas of focal tendon degeneration on ultrasonography. This modality also allows for dynamic examination, which may improve specificity and sensitivity ( ). However, the diagnostic accuracy of ultrasonography is highly dependent on the operator and may be less effective without well-trained sonographers.

Magnetic resonance imaging (MRI) remains the standard of care for radiologic detection of medial epicondylitis. Noncontrast MRI is effective for detecting pathologic change in the tendon, such as frank tendinous disruption as well as other medial elbow pathology (e.g., UCL or osteochondral injuries) ( ) ( Fig. 28.2 ). On T2-weighted sequences, intermediate to high signal intensity at the CFT, especially in the setting of peritendinous edema, is indicative of medial epicondylitis ( ). Advanced imaging is typically used when concern for concomitant pathology is high (e.g., evaluation of the UCL in an overhead thrower) or if the clinical picture is unclear regarding the source of medial elbow pain.

Coronal slice of a magnetic resonance image of a minor league reliever demonstrating a tear of the flexor-pronator mass near the proximal origin (oval).

From Patel RM, Lynch TS, Amin NH, Calabrese G, Gryzlo SM, Schickendantz MS. The thrower’s elbow. Orthop Clin North Am . 2014;45(3):355-376.

Nonoperative Management

As with many chronic tendinopathies, nonsurgical therapy is the mainstay of treatment. Surgical procedures are typically reserved for patients with recalcitrant or recurrent symptoms despite nonsurgical management.

The initial focus of nonsurgical supportive care is the relief of medial-sided elbow pain. Patients should refrain from activities that exacerbate symptoms, especially those that require repetitive wrist flexion, forearm pronation, and valgus stress about the elbow. Athletes with concomitant UCL injury should refrain from throwing for 6 to 12 weeks, with particular care taken to avoid valgus stress during the first 6 weeks of treatment. Periods of acute pain and swelling may be alleviated with icing, which provides both analgesic and vasoconstrictive effects ( ). Nonsteroidal antiinflammatory drugs (NSAIDs) may also provide effective pain relief and may be used routinely for 1 to 2 weeks as tolerated by the patient. These medications are particularly effective in reducing the synovitis associated with flexor-pronator tendon degeneration ( ). Night splinting and supportive orthoses may be used simultaneously, especially extension splinting in patients with ulnar neuritis. Counterforce bracing limits the maximal contractile force generated by the flexor-pronator musculotendinous unit ( ). demonstrated pain relief in baseball pitchers with medial epicondylitis by using forearm kinesiology taping techniques as a method of counterforce bracing. However, splinting and bracing should not involve prolonged elbow immobilization secondary to joint stiffness. In the setting of injury to the UCL, a hinged elbow brace can be used to provide varus–valgus stability and prevent full elbow extension.

Extracorporeal shockwave therapy (ESWT) may provide pain relief for a subset of patients. Electrical stimulation of the diseased tendon may promote angiogenesis, tendon healing, and short-term analgesia ( ). In a study of patients with newly diagnosed epicondylitis treated with ESWT or steroid injection, reported worse clinical pain scores at 1 and 2 weeks with ESWT but better patient satisfaction at 8 weeks. However, reported excellent or good clinical results with ESWT in only 7 of 30 patients at 1-year follow-up, which was notably worse than the results achieved in patients with lateral epicondylitis who underwent similar treatment. Definitive recommendations for the use of shockwave therapy for medial epicondylitis, including treatment duration and stimulation protocol, cannot be made at this point.

When noninvasive techniques prove inadequate, a corticosteroid injection is often effective in reducing medial elbow discomfort. The corticosteroid is injected into the peritendinous and synovial tissues rather than into the tendon itself ( ). Similar to oral antiinflammatory medications, the corticosteroid may reduce the surrounding synovitis and resultant pain. Historically, direct injection deep to the flexor-pronator tendon has been the delivery technique of choice, although transcutaneous methods may be effective as well ( ). Care should be taken to prevent iatrogenic complications such as subcutaneous atrophy, tendon weakening, or nerve injury. Local depigmentation may occur as well, especially in patients with darker skin ( ; ). Needle injection also provides the benefit of tendon trephination, which may stimulate bleeding and tendon healing ( ). In a prospective study of 60 elbows treated with steroid injection for medial epicondylitis, noted an acute improvement in pain during the 6 weeks after injection but no difference by 3 months. demonstrated even shorter term gains after steroid injection, with acute improvement in pain scores over the first 2 weeks followed by a plateau for up to 8 weeks. combined needle stimulation and injection of autologous blood into the disrupted tendon, which resulted in decreased visual analog scale and Nirschl scores at 10 months.

Much attention has been devoted to platelet- rich plasma (PRP) injections in the treatment of epicondylitis, although the majority of Level I and II studies have focused on lateral epicondylitis as opposed to medial ( ). PRP is thought to induce an acute inflammatory response with an abundance of various growth factors that may lead to healing of the damaged tissue ( ). In a level I randomized control trial, 100 patients with chronic lateral epicondylitis were randomly assigned to PRP treatment ( n = 51) or corticosteroid injection ( n = 49) ( ). Both treatment groups experienced significant pain reduction, but relief for the PRP group lasted greater than 6 months, unlike the corticosteroid group. In addition, patients who underwent PRP injections had a significant improvement in their DASH (Disabilities of the Arm, Shoulder, and Hand) and visual analog scores (VAS) at 1 year compared to patients who underwent a corticosteroid injection. A follow-up study showed that the improvement in pain and function persisted at 2 years of follow-up ( ).

Data from studies evaluating medial epicondylitis show more mixed results. A cohort study that followed a total of 31 elbows with recalcitrant epicondylitis (medial, n = 8; lateral, n = 23) showed that patients who underwent PRP injection experienced a greater than 25% reduction in worst pain, using a VAS, at 1-year follow-up ( ). However, a different cohort study that followed 14 patients with medial epicondylitis who underwent PRP injection failed to show a statistically significant improvement in patient rated elbow evaluation (PREE) and quick-DASH scores when measured at 6-month follow-up ( ). Ultimately, more high-quality studies are required to determine the efficacy of PRP injections for medial epicondylitis.