Steven T. Lanier and Jason H. Ko

The patient is a 35-year-old right-handed woman who presented with a 3-year history of pain along the dorsoradial aspect of the proximal forearms bilaterally, with the left arm being more symptomatic than the right. She also reported some weakness of finger extension on the left compared to the right, along with intermittent numbness and tingling in the dorsoradial aspect of her left hand and wrist. She worked as a nurse and had trouble performing some of her job duties due to the pain.

On examination, the patient endorsed focal tenderness over the area of the posterior interosseous nerve (PIN) on the left dorsoradial forearm approximately 5 cm distal to the lateral epicondyle, along with a positive Tinel’s sign over the radial tunnel. Scratch-collapse test was positive for radial neuropathy in the left dorsal forearm. Symptoms were exacerbated with resisted forearm supination. She had 5/5 muscle strength of the wrist extensors, but 4–/5 strength of the extensor digitorum communis (EDC) compared to the contralateral side, with slightly diminished sensation to light touch in the radial sensory nerve distribution. Palpation of the lateral epicondyle elicited minimal to no tenderness, and there was no appreciable increase in pain with resisted wrist extension, making lateral epicondylitis a less likely diagnosis. Based on these findings, a diagnosis of radial tunnel syndrome was made. Nerve conduction studies and electromyogram (EMG) were not obtained as these are often normal in the cases presenting with radial tunnel syndrome, and the diagnosis is considered a clinical one.

Prior to presentation, the patient had been unsuccessfully treated by an outside surgeon for presumed lateral epicondylitis with nonsteroidal anti-inflammatory drugs (NSAIDs) and therapy exercises. She had attempted to avoid activities that exacerbated the pain, but she was still working without restrictions and dealing with persistent pain. Conservative measures had failed to provide any relief, and upon learning of the diagnosis of radial tunnel syndrome, the patient desired surgical intervention on the left upper extremity with the hope of returning to work pain free.

The patient has no external stigmata of injury of the proximal dorsoradial forearm or lateral epicondylar region. Based on her history and physical examination findings, however, we can deduce that the radial nerve is being compressed within the radial tunnel. The radial nerve courses anterior to the lateral intermuscular septum in the distal arm. After giving branches to the brachialis and brachioradialis muscles, it enters the dorsoradial aspect of the forearm anterior to the lateral epicondyle. After branching to the extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), and supinator muscles, the radial nerve bifurcates into the radial sensory nerve and the PIN, which immediately courses deep to the proximal edge of the superficial head of the supinator muscle into the radial tunnel. The radial tunnel is bordered radially by the ECRB muscle, medially by the biceps tendon and brachialis, with a floor formed by the radiocapitellar joint proximally, and deep head of the supinator muscle distally. The roof of this tunnel consists of the superficial head of the supinator muscle, the most proximal extent of which forms the arcade of Frohse. Potential compression points of the radial nerve include the fibrous bands of the radiocapitellar joint, recurrent leash of Henry (radial recurrent vessels), the proximomedial edge of the ECRB, the arcade of Frohse, and the distal edge of the supinator.

For patients presenting with early signs of nerve compression and no motor weakness, conservative measures are attempted first for a period of at least 3 months, including activity modification, NSAIDs, and corticosteroid injection (CSI). In a series by Sarhadi et al, 16 of 23 patients experienced 2 years of pain relief with a single injection of 40 mg of triamcinolone. We offer surgical decompression of the radial nerve if conservative measures fail, if the patient’s symptoms have a significant negative impact on work and leisure activities, or if there is evidence of PIN-innervated extensor muscle weakness when compared to the contralateral side. The three commonly used surgical exposures are the volar approach (referred to as the Henry approach), the brachioradialis-splitting approach, and the dorsal approach. Our preferred surgical technique is the dorsal approach, which develops the interval between the brachioradialis and the ECRL. Reported success rates of surgical decompression of the radial nerve vary from 67 to 92%. A recent series of patients by Simon Perez et al treated with the dorsal approach reported that approximately 50% of patients achieved symptom-free “excellent” results and an additional 37% achieved “good results,” with only occasional symptoms with prolonged activity.

• Surgical decompression of the radial nerve in the radial tunnel via a dorsal approach between the brachioradialis and the ECRL interval.

• Full release of the arcade of Frohse and the superficial head of the supinator muscle.

• Ligation of the leash of Henry if there are visible signs of anatomic compression.

The patient is taken to the operating room and placed supine on the operating table. The arm is abducted 90 degrees and placed on a hand table, and a tourniquet is placed on the upper arm. The arm is then prepped and draped in the standard fashion.