Case Reports

Pronator Teres Myotendinous Tear

Am J Orthop. 2017 March;46(2):E105-E107

Pronator teres muscle strain is a rare sporting injury reported thus far only in cricket and golf players. The injury appears to occur when the sporting club or racket strikes the ground during a forceful swing and causes the elbow to experience an eccentric force during resisted elbow flexion and pronation. On initial presentation, this injury can be mistaken for injury to the medial ulnar collateral ligament, or exacerbation of medial epicondylitis. On examination, bruising and tenderness distal to the elbow over the course of the pronator teres are often present. Advanced imaging confirms the diagnosis and can help in grading injury severity. In this article, we report the case of a patient who was conservatively treated, and returned to function and sport by 6 weeks after a period of rest and restricted activities. The prognosis is excellent for even high-grade strains. Complete return to sporting function without residual weakness is expected.

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References

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4. Banks KP, Ly JQ, Beall DP, Grayson DE, Bancroft LW, Tall MA. Overuse injuries of the upper extremity in the competitive athlete: magnetic resonance imaging findings associated with repetitive trauma. Curr Probl Diagn Radiol. 2005;34(4):127-142.

5. Niebulski HZ, Richardson ML. High-grade pronator teres tear in a cricket batsman. Radiol Case Rep. 2015;6(3):540.

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8. Helton MS. Conservative treatment of a proximal full-thickness biceps brachii muscle tear in a special operations soldier. Phys Ther. 2014;94(4):571-577.

9. Mitchell K, Banks S, Morgan D, Sugaya H. Shoulder motions during the golf swing in male amateur golfers. J Orthop Sports Phys Ther. 2003;33(4):196-203.

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Take-Home Points

Pronator teres muscle injuries are rare.
Injury can be mistaken for MUCL injury in athletes.
Tenderness and weak/painful forearm pronation are common findings.
MRI confirms the diagnosis and helps grade the muscle strain injury.
Conservative treatment is recommended and prognosis is excellent even for high-grade strains.

Pronator teres muscle strain is a rare sporting injury reported only in cricket players, and now in a golfer whose forearm experienced an eccentric force during resisted elbow flexion and pronation.^1,2 The injury occurs when the sporting club or racket strikes the ground during a swing, impeding forward progress and subjecting the pronator teres muscle to eccentric forces in excess of what it can withstand. The pronator teres, one of several muscles that comprise the flexor wad of the forearm, consists of 2 heads, originating proximally from the medical epicondyle and attaching distally to the shaft of the radius on its lateral surface and just distal to the supinator. The oblique orientation of the muscle belly allows it to serve in its primary rotatory role as the main pronator of the forearm. Injuries to the soft tissue of the medial forearm are common in both elite and recreational athletes, especially in racket and club sports.³ Often, these injuries are related to overuse and chronic fatigue of the surrounding soft tissue—caused by repetitive flexing, gripping, or swinging. Even when identified early, these injuries can result in a significant loss of training time.⁴ In this article, we report a case of pronator teres muscle tear at the myotendinous junction. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A right-hand–dominant 36-year-old man presented to the clinic with pain on the medial side of his right elbow after sustaining an injury to the elbow while playing golf several days earlier. The patient, an advertising executive, was playing recreational golf several times a month and had no significant medical history or previous symptoms related to the elbow. Initial pain symptoms began during a second round of play, immediately after the patient miss-hit an iron shot, making contact mostly with the ground and causing the club to forcefully stop. The pain was on the medial side of the elbow and forearm. The patient noted progressive swelling and bruising at the pain site and development of forearm weakness. Physical examination during the clinic presentation revealed ecchymosis on the anterior medial forearm, medial elbow, and medial triceps (Figure 1).

Mild tenderness to palpation was elicited over the medial elbow, specifically over the course of the flexor pronator mass. When the elbow was assessed for tender areas, the medial epicondyle was not tender. Range of motion (ROM) testing revealed 120° of flexion and 10° short of full extension, attributed to swelling from acute injury. The patient had full supination and pronation, but the pain was reproduced with either movement. The pain produced weakness with flexion and pronation. Valgus stress test results were normal; there was no re-creation of symptoms. The median nerve was negative for the Tinel sign, and the rest of the neurovascular examination was unremarkable. The ipsilateral shoulder was normal on examination.

Noncontrast magnetic resonance imaging (MRI) showed a high-grade partial tear of the pronator teres myotendinous junction (Figures 2A-2C).

In the surrounding tissue there was an associated increased signal representing edema. Also found was a small intramuscular hematoma. The median nerve, medial collateral ligament, distal biceps, and triceps were uninjured.

The patient was instructed to rest the elbow from strenuous activity, golf in particular, for 4 weeks. Physical therapy for ROM and forearm strengthening of the surrounding flexor wad was initiated at 2 weeks and continued for 4 weeks. The patient was advised to take over-the-counter nonsteroidal anti-inflammatory drugs as needed for comfort. On repeat examination at 4 weeks, with tenderness or weakness with pronation absent and full ROM regained, the patient was released back to full activity. He was able to return to golf and reported being symptom-free and having no sense of weakness or loss of control.

Discussion

A tear of the pronator teres is an exceedingly rare injury. Our results with conservative treatment and a full return to previous activity level are consistent with the only other case reported in the literature.⁵ In contrast to our patient, the previous patient sustained a tear of the pronator teres after a prolonged period of batting during a recreational cricket match.

Pronator Teres Myotendinous Tear

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Take-Home Points

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