Ulnar Nerve Injury in the Throwing Athlete

Jeffrey R. Dugas MD

E. Lyle Cain Jr MD

The overhead throwing motion generates significant forces in the shoulder and elbow articulations. These extreme forces subject the tissues in and around the joints of the upper extremity to stresses that, in many cases, are greater than the normal capacity of those tissues. At the elbow, valgus stress during the acceleration phase of throwing exceeds the maximum tensile strength of the ulnar collateral ligament (UCL). The excess stress is taken up by the surrounding tissues, including the ulnar nerve. The ulnar nerve courses from the medial aspect of the upper arm, around the medial epicondyle via the cubital tunnel, to the medial side of the forearm where it divides into its various branches. Ulnar neuritis is a common reason for pain and neurologic symptoms in the throwing elbow, but often represents a secondary condition caused by an underlying abnormality, especially valgus instability. Although medial elbow instability is a common cause of ulnar nerve symptoms, other conditions can lead to similar symptoms such as flexor-pronator strains/tendonitis/tears, medial epicondyle apophysitis or avulsion, valgus extension overload, stress fractures, and articular injuries. Also, the presence of cervical spine pathology can mimic ulnar neuritis via compression of one or more nerve roots at the cervical level. Compression of some or all of the brachial plexus can also cause focal elbow symptoms that can mimic more peripheral ulnar nerve compression.

The physician caring for overhead athletes must have a thorough understanding of the anatomy and physiology of the various structures in and around the elbow joint. An understanding of the biomechanics of the throwing motion and the pathomechanics that can lead to injury is also mandatory. The purpose of this chapter is to review the diagnosis and treatment of ulnar nerve problems in the overhead athlete.

History of the Technique

When adequate conservative management fails to relieve symptoms, surgical treatment options in the throwing athlete include ulnar nerve neurolysis with or without transposition out of the cubital tunnel. There continues to be some differences of opinion in the printed literature regarding simple decompression versus submuscular or subcutaneous transposition.¹^,²^,³ Although medial epicondylectomy has been advocated for ulnar nerve decompression in the nonathlete, it is not recommended in the overhead-throwing athlete because of the threat of injury to the proximal attachment of the UCL and the possibility of nonunion.⁴

Anterior transposition of the ulnar nerve completely frees the nerve and places it in a healthy bed, as well as effectively lengthening the nerve and decreasing traction forces by rerouting it anterior to the medial epicondyle and anterior to the axis of motion of the elbow. This increased effective length is especially important to decrease ulnar nerve tension forces in the throwing athlete because of the valgus and flexion moments on the medial elbow during overhead throwing. Transposition anteriorly also removes the nerve from the position of greatest tension near the main valgus stabilizer of the elbow, the ulnar collateral ligament. For these reasons, anterior transposition is most often combined with neurolysis in the athlete.

In Situ Decompression (Neurolysis)

Proponents of simple decompression of the ulnar nerve suggest that this simple procedure preserves the native anatomy and vascular supply to the nerve and allows an easy rehabilitation. In this procedure, the cubital tunnel fascia (arcuate ligament) is released along a course beginning at the arcade
of Struthers and ending well into the fibrous band at the flexor carpi ulnaris (FCU) origin. The nerve remains in its native bed, but is allowed to move freely without any direct compression or adhesions. The nerve is not removed from the cubital tunnel.

Although several authors have noted better outcomes with simple decompression compared to submuscular or subcutaneous transposition in the nonathletic population, simple decompression is generally not sufficient to relieve the traction forces caused by the act of overhead throwing.¹^,³ Simple decompression has also been noted to result in a high recurrence rate and may worsen any ulnar nerve instability or subluxation.⁵^,⁶ We do not currently perform simple decompression or neurolysis except in the rare revision procedure in a patient with persistent symptoms after previous anterior transposition.

Submuscular Transposition

First described by Learmonth⁷ in 1942, submuscular transposition has been widely utilized for the treatment of ulnar nerve symptoms in the throwing athlete, especially with associated UCL reconstruction using the technique pioneered by Jobe et al.⁸ The nerve is released along the entire cubital tunnel region, from the arcade of Struthers well into the FCU, and is transposed under the detached flexor-pronator muscle mass. Submuscular transposition provides the nerve a straight path with a layer of muscular protection from the direct and indirect trauma that may occur during sports participation. Improved visualization of the underlying UCL is also an advantage of the submuscular technique. Although several authors have reported significant complication rates using the submuscular transposition, others have reported reasonable success.⁴^,⁹^,¹⁰^,¹¹ Delpizzo et al.¹² reported the results of submuscular anterior transposition of the ulnar nerve in 19 high-level baseball players with symptoms of ulnar neuritis that failed adequate conservative treatment. Only nine of 15 (60%) patients evaluated at 3 to 58 months postoperatively were able to return to play. The authors reported that the technique allowed easy inspection of the UCL and easy arthrotomy to remove loose bodies or osteophytes, if present. They also believed that submuscular transposition provided stable fixation with protection from direct trauma.

Often ulnar nerve symptoms are present in the setting of medial elbow laxity due to an incompetent ulnar collateral ligament. Surgical management of the ulnar nerve symptoms with transposition is unlikely to succeed unless the underlying UCL pathology is addressed simultaneously.⁴ Despite initial enthusiasm, several later reports by Jobe and Nuber⁸ and Conway et al.¹³ have shown that the ulnar nerve may be at risk with a submuscular transposition. These authors reported 31% and 21% incidence of postoperative ulnar nerve dysfunction, respectively, after UCL reconstruction with submuscular transposition of the ulnar nerve. Based on this experience, Jobe and Attrache¹⁴ have recommended performing submuscular ulnar nerve transfer with UCL reconstruction only in the setting of preoperative ulnar neuritis or the need for posterior compartment exploration.

Despite these authors’ success, we currently do not performed submuscular ulnar nerve transposition in the throwing athlete because of concerns about the ultimate strength and healing of the flexor-pronator muscle mass and difficulty with nerve dissection in the case of revision elbow surgery.

Subcutaneous Transposition

Subcutaneous ulnar nerve transposition is our procedure of choice. This procedure is performed by executing a thorough neurolysis from the arcade of Struthers down to and within the FCU muscle mass. The nerve is then anteriorly transposed and loosely secured beneath a small leash of the flexor-pronator fascia. The cubital tunnel is then closed to obliterate the space and prevent relocation of the nerve if the leash fails. In our hands, subcutaneous nerve transposition stabilized with a fascial sling has provided good results with few surgical complications and low rates of recurrence.¹⁵^,¹⁶ Other benefits of the subcutaneous technique include the less invasive nature of the procedure, preservation of the flexor pronator muscle mass, and the ability to perform accelerated rehabilitation. Since Curtis¹⁷ initially described subcutaneous ulnar nerve transfer in 1898, several authors have reported the surgical technique and results of various ways to perform subcutaneous transposition.¹⁶^,¹⁸^,¹⁹ In series of 16 baseball players including 7 pitchers by Eaton et al.,¹⁹ the subcutaneous technique was utilized, and all were able to return to competition without symptoms. No complications were reported in their series.

Rettig and Ebben¹⁸ reported excellent results with anterior subcutaneous transfer of the ulnar nerve stabilized with a fascial sling in 20 athletes who had failed nonoperative management. At an average follow-up of 19 months (6 to 50 months), 95% (19 of 20) were able to compete, ten at the same level without limitations, and nine at a lower level with mild limitations. Average return to play was 12.6 weeks, and the authors recommended subcutaneous over submuscular transposition due to faster rehabilitation and decreased surgical morbidity.

From our institution, Andrews and Timmerman¹⁵ reported on eight professional baseball players after anterior subcutaneous ulnar nerve transfer, including six patients who also had posteromedial olecranon osteophyte excision. Seven of eight (88%) returned to play for at least one season at the professional level. Azar et al.¹⁶ reported that preoperative ulnar nerve symptoms resolved in nine of ten patients when subcutaneous ulnar nerve transfer was performed in conjunction with UCL reconstruction. Subcutaneous transposition may offer less morbidity compared to submuscular transfer in the setting of UCL reconstruction.

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