Radial Tunnel Syndrome

Home , Ganglion cyst, Radial nerve, Radial tunnel syndrome

ICD-10 CODE G56.90 extrinsic masses, or a sharp tendinous margin of the extensor carpi radialis brevis. These entrapments may exist alone or in combination. THE CLINICAL SYNDROME SIGNS AND SYMPTOMS Radial tunnel syndrome is an uncommon cause of lateral elbow pain that has the unique distinction among entrapment neurop- Regardless of the mechanism of entrapment of the radial nerve, athies of almost always being initially misdiagnosed. The inci- the common clinical feature of radial tunnel syndrome is pain dence of misdiagnosis of radial tunnel syndrome is so common just below the lateral epicondyle of the humerus. The pain of that it is often incorrectly referred to as resistant tennis elbow radial tunnel syndrome may develop after an acute twisting (Table 46.1). As seen from the following discussion, the only injury or direct trauma to the soft tissues overlying the poste- major similarity that radial tunnel syndrome and tennis elbow rior interosseous branch of the radial nerve, or the onset may share is the fact that both clinical syndromes produce lateral be more insidious, without an obvious inciting factor. The pain elbow pain. is constant and worsens with active supination of the wrist. The lateral elbow pain of radial tunnel syndrome is aching Patients often note the inability to hold a coffee cup or hammer. and localized to the deep extensor muscle mass. The pain may Sleep disturbance is common. On physical examination, elbow radiate proximally and distally into the upper arm and forearm range of motion is normal. Grip strength on the affected side (Fig. 46.1). The intensity of the pain of radial tunnel syndrome may be diminished. is mild to moderate, but it may produce significant functional In the classic text on entrapment neuropathies, Dawson and disability. colleagues note three important signs that allow the clinician In radial tunnel syndrome, the posterior interosseous branch to distinguish radial tunnel syndrome from tennis elbow: (1) of the radial nerve is entrapped by a variety of mechanisms tenderness to palpation distal to the radial head in the muscle that have in common a similar clinical presentation (Fig. 46.2). mass of the extensors, rather than over the more proximal lat- These mechanisms include aberrant fibrous bands in front of the eral epicondyle, as in tennis elbow; (2) increasing pain on active radial head, anomalous blood vessels that compress the nerve, resisted supination of the forearm owing to compression of the

TABLE 46.1 Characteristics of Radial Tunnel Syndrome and Lateral Epicondylitis Characteristic Radial Tunnel Syndrome Lateral Epicondylitis (Tennis Elbow) Frequency Rare (2% of all peripheral nerve compressions of the upper limb) Common cause of lateral elbow pain Cause Compression of the radial nerve Caused by overuse of the extensor and supinator muscles Characteristic patient Anybody with repetitive, stressful pronation and supination (e.g., tennis Tennis players players, Frisbee players, swimmers, powerlifters) Pain location Pain over the neck of the radius and lateral aspect of the proximal forearm Pain and tenderness over the lateral epicondyle over the extensor muscles themselves (distal to where the pain is located and immediately distal to it (at the origin of in lateral epicondyle) the extensor muscles) Pain radiation Pain can radiate proximally and (more commonly) distally Usually localized without radiation Provocative tests (much overlap Pain with resisted extension of the middle finger with the forearm pronated Pain with resisted wrist extension or elbow between the two entities) and the elbow extended. Pain with resisted forearm supination with the supination with the elbow extended. Pain with elbow fully extended forceful wrist flexion or forearm pronation

Modified from Mileti J, Largacha M, O’Driscoll SW. Radial tunnel syndrome caused by ganglion cyst: treatment by arthroscopic cyst decompres- sion. Arthroscopy. 2004;20:e39–e44.

151 152 SECTION 4 Elbow Pain Syndromes radial nerve by the arcade of Frohse as a result of contraction of action against resistance. Patients with radial tunnel syndrome the muscle mass; and (3) a positive result on the middle finger exhibit increased lateral elbow pain secondary to fixation and test. The middle finger test is performed by having the patient compression of the radial nerve by the extensor carpi radialis extend the forearm, wrist, and middle finger and sustain this brevis muscle (Fig. 46.3).

TESTING Because of the ambiguity and confusion surrounding this clinical syndrome, testing is important to help confirm the diagnosis of radial tunnel syndrome. Electromyography helps distinguish cervical radiculopathy and radial tunnel syndrome from tennis elbow. Plain radiographs are indicated in all patients who

Deep radial nerve Arcade of Frohse

Superficial extensor bundle

Radial nerve Brachioradialis muscle

Extensor carpi radialis brevis Supinator muscle muscle Radius Deep interosseous artery

Biceps tendon

Proximal Distal Longitudinal biceps tendon insertion view

Fig. 46.1 The pain of radial tunnel syndrome is localized to the deep extensor muscle mass and may radiate proximally and distally into the Fig. 46.3 Ultrasound image demonstrating the relationship of the radial upper arm and forearm. nerve to the arcade of Frohse.

A B C

Fig. 46.2 Recurrent radial tunnel syndrome with posterior interosseous nerve (PIN) entrapment in a 44-year- old man with painful forearm and elbow following prior radial tunnel release. Axial T2 spectral attenuated inversion recovery (SPAIR) (A) image shows normal radial nerve (large arrow) and abnormal ulnar nerve (small arrow) at the level of elbow, consistent with cubital tunnel syndrome. Axial T2 SPAIR (B) and T1-weighted (C) images at proximal forearm show the postoperative scarring (large arrows), mildly hyperintense superficial radial nerve (small arrows), and markedly abnormal PIN (double small arrows). (From Chalian M, Behzadi AH, Williams EH, et al. High-resolution magnetic resonance neurography in upper extremity neuropathy. Neuro- imaging Clin N Am. 2014;24[1]:109–125, fig 13.) CHAPTER 46 Radial Tunnel Syndrome 153 present with radial tunnel syndrome to rule out occult bony of “resistant tennis elbow” and (2) the potential for permanent pathology. Based on the patient’s clinical presentation, addi- neurological deficits as a result of prolonged untreated entrap- tional testing, including complete blood cell count, uric acid, ment of the radial nerve. Failure of the clinician to recognize erythrocyte sedimentation rate, and antinuclear antibody test- an acute inflammatory or infectious arthritis of the elbow may ing, may be indicated. result in permanent damage to the joint and chronic pain and Magnetic resonance imaging (MRI) of the elbow is indicated functional disability. if internal derangement of the joint is suspected and may help identify the factors responsible for the nerve entrapment, such CLINICAL PEARLS Radial tunnel syndrome is a distinct clinical entity as ganglion cysts or lipomas (see Fig. 46.2–C). The injection that is often misdiagnosed as tennis elbow, and this fact accounts for the technique of the radial nerve at the elbow with a local anes- many patients with “tennis elbow” who fail to respond to conservative measures. Radial tunnel syndrome can be distinguished from tennis elbow thetic and steroid may help confirm the diagnosis and treat the because with radial tunnel syndrome, the maximal tenderness to palpation is syndrome. over the radial nerve, whereas with tennis elbow, the maximal tenderness to palpation is over the lateral epicondyle. DIFFERENTIAL DIAGNOSIS If radial tunnel syndrome is suspected, injection of the radial nerve at the humerus with a local anesthetic and steroid gives almost instantaneous relief. Cervical radiculopathy and tennis elbow can mimic radial tun- Careful neurological examination to identify preexisting neurological deficits nel syndrome. Radial tunnel syndrome can be distinguished that may later be attributed to the nerve block should be performed on all from tennis elbow because with radial tunnel syndrome, the patients before beginning radial nerve block at the humerus. maximal tenderness to palpation is distal to the lateral epicondyle over the posterior interosseous branch of the radial nerve, whereas with tennis elbow, the maximal tenderness to palpation SUGGESTED READINGS is over the lateral epicondyle. Increased pain with active supination and a positive middle finger test (see earlier discussion) Clavert P, Lutz JC, Adam P. Frohse’s arcade is not the exclusive com- helps strengthen the diagnosis of radial tunnel syndrome. Acute pression site of the radial nerve in its tunnel. Orthop Traumatol gout affecting the elbow manifests as a diffuse acute inflamma- Surg Res. 2009;95:114–118. tory condition that may be difficult to distinguish from infec- Deniel A, Causeret A, Moser T, Rolland Y, Dréano T, Guillin R. tion of the joint, rather than a localized nerve entrapment. Entrapment and traumatic neuropathies of the elbow and hand: an imaging approach. Diagn Interv Imaging. 2015;96(12):1261–1278. Huisstede B, Miedema HS, van Opstal T. Interventions for treating TREATMENT the radial tunnel syndrome: a systematic review of observational studies. J Hand Surg. 2008;33:e1–72.e10.72. Initial treatment of the pain and functional disability associated Kumar SD, Bourke G. Nerve compression syndromes at the elbow. with radial tunnel syndrome should include a combination of Orthop Trauma. 2016;30(4):355–362. nonsteroidal antiinflammatory drugs (NSAIDs) or cycloox- Lee JT, Azari K, Ford Jones N. Long term results of radial tunnel re- ygenase-2 (COX-2) inhibitors and physical therapy. The local lease: the effect of co-existing tennis elbow, multiple compression application of heat and cold also may be beneficial. Patients syndromes and workers’ compensationa. J Plast Reconstr Aesthet should avoid the repetitive movements that incite the syndrome. Surg. 2008;61:1095–1099. For patients who do not respond to these treatment modalities, Marchese J, Wolf JM, Coyle K, Cote M. Prospective evaluation of injection of the radial nerve at the elbow with a local anesthetic single corticosteroid injection in radial tunnel syndrome: level 4 evidence. J Hand Surg. 2017;42(9)(suppl):S51. and steroid may be a reasonable next step. If the symptoms of Tennent TD, Woodgate A. Posterior interosseous nerve dysfunction radial tunnel syndrome persist, surgical exploration and decom- in the radial tunnel. Curr Orthop. 2008;22:226–232. pression of the radial nerve are indicated. Thurston A. Radial tunnel syndrome. Orthop Trauma. 2013;27(6):403–408. COMPLICATIONS AND PITFALLS Waldman SD. Radial tunnel syndrome. In: Waldman SD, Campbell RSD, eds. Imaging of Pain. Philadelphia: Saunders; 2011:287–288. The major complications associated with radial tunnel syndrome Waldman SD. Radial tunnel syndrome. In: Waldman SD, ed. Pain fall into two categories: (1) iatrogenically induced complica- Review. 2nd ed. Philadelphia: Elsevier; 2016:2252–2254. tions resulting from persistent and overaggressive treatment