Split Brachioradialis Tendon Causing Wartenberg Syndrome in a Professional Baseball Pitcher

A 22-year-old minor league baseball player presented to our clinic complaining of a burning sensation in the middistal forearm that radiated toward his dorsoradial hand while pitching. The issue had started approximately 9 months earlier. However, he recently started implementing a new slider technique that led to exacerbation of the pain. This was initially treated as tendonitis and then de Quervain disease, but after an unsuccessful corticosteroid injection, the case was referred to an outside hand surgeon for evaluation. Written informed consent was obtained from the patient for publication of this case report and accompanying images.

The patient described intermittent burning and pain, approximately 9-cm proximal from the lister tubercle. Pronation, ulnar deviation, and flexion maneuver failed to elicit paresthesia. Paresthesia was reproducible with active loading of the wrist when in pronation, ulnar deviation, and flexion. These findings were concerning for a Wartenberg syndrome diagnosis. A combination of anesthetic and corticosteroid was injected into the area of discomfort and the patient was instructed to return to the clinic in 2 weeks for reevaluation. Two weeks later, the patient reported mildly improved symptoms. Because of his initial improvement, conservative management was to be continued with nerve glide exercises and the eventual return to progressive pitching program. However, despite the patient’s initial improvement, he returned 3 months later with continued symptoms. Therefore, surgical management was recommended.

During the procedure, a 6-cm incision was centered over a location 9-cm proximal to the radial styloid. During initial dissection to the interval of the brachioradialis and extensor carpi radialis longus, it was noticed that the superficial radial nerve was emerging in between a split tendon of the brachioradialis and was being compressed (Figure 1, Figure 2). The most dorsal aspect of the tendon was excised, and the path of the nerve was followed distally to its first split to ensure it remained subcutaneous, and then proximally to identify other areas of compression (Fig. 3). An intraoperative pronation, ulnar deviation, and flexion maneuver revealed compression of the nerve by the main muscle belly of the brachioradialis (Fig. 4). A 1 × 3–cm section was excised to prevent scarring of the nerve. On a repeat pronation, ulnar deviation, and flexion examination, no compression was noted. Figure 5 depicts a diagram of forearm anatomy.

The patient was then placed in a plaster orthosis for 2 weeks, followed by a removable orthosis for 2 weeks, working on periodic active partial range of motion. Four weeks after surgery, he started passive full range of motion along with progressive strengthening.

At his 6-week follow-up visit, the patient presented with full range of motion, a negative Tinel sign, and no dysesthesias, with passive flexion, ulnar deviation, and pronation. Two weeks later, the patient graduated passive range of motion rehabilitation and started his observed throwing program. He completed all therapeutic warm-up and rehabilitation activities as directed without issue. The patient is now 6 months after surgery and back to full participation with no restrictions in minor league games as a pitcher.

Peripheral neuropathies are a group of conditions that alter quality of life and the ability to work. Symptoms of peripheral compression neuropathy include paresthesia, dysesthesia, and weakness depending on the nerve that is being compressed. Etiologies are often divided into 2 categories as follows: acute traumatic crushing injuries and chronic compression of a nerve at sites of anatomic narrowing along the nerves course. The SRN runs superficial to the supinator and deep to the brachioradialis at the level of the forearm.^,,,  The SRN has been described as piercing the deep fascia between the middle and distal thirds of the forearm at 6.03, 9.0, and 9.2–cm proximal to the radial styloid and from there supplies the hand with its terminal branches.^, These terminal branches supply innervation to the dorsoradial and dorsoulnar portion of the thumb and the dorsoradial portion of the hand and index and middle fingers proximal to the distal interphalangeal joint. Superficial branch of the radial nerve compression is initially managed conservatively when appropriate with rest, activity modification, nonsteroidal anti-inflammatory drugs, injections, and orthoses. When conservative treatment has failed for greater than 6 months, operative management is considered in the form of decompression of the nerve. The anatomic variant discussed here was diagnosed intraoperatively after failure of conservative treatment. Although not used here, it should be noted that ultrasonography during physical examination maneuvers has been effective at demonstrating compressive neuropathies prior to surgical management. The use of high resolution sonographic probes during the pronation, ulnar deviation, and flexion maneuver could have proven useful to obtain a better understanding of the variant pathology prior to surgical intervention. Spontaneous resolution of symptoms is common with conservative management.

In conclusion, the purpose of this case report is to describe the history and physical examination of a minor league baseball player who failed conservative treatment for SRN compression and was found to have split brachioradialis tendons causing entrapment. This is a rare anatomic variation that has been mentioned but rarely described in the literature and, to our knowledge, never in a high-level professional athlete. Turkoff et al demonstrated that the dorsal, more ulnar, slip of brachioradialis was smaller and likely to be more formidable to resection without complications of adhesions, recurrent compression, and/or loss of postoperative strength. The uncomplicated postoperative course further supports these claims.