Radial Tunnel Syndrome is a common entrapment neuropathy of the posterior interosseous nerve. This reviews anatomy, diagnosis and treatment.
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Definition of Radial Tunnel Syndrome
Radial tunnel Syndrome is the intermittent compression of the radial nerve in the radial tunnel without associated extensor muscle weakness. It was first described by Michele Krueger in 1956 as “radial pronator syndrome”1.
Anatomy of Radial Tunnel Syndrome
The Radial Tunnel is a 5 cm tunnel from the radiocapitellar joint to the distal edge of the supinator with well-defined anatomical boundaries:
- Lateral: Brachioradialis, ERCL, ECRB
- Medial: Biceps tendon, brachial
- Floor: Capsule of the radiocapitellar joint
Causes of Radial Tunnel Syndrome
Radial Tunnel Syndrome is caused by compression of the radial nerve. A mnemonic for sites of compression at radial tunnel is "REAL"
- Radiohumeral joint: fibrous bands tethering the nerve
- ECRB tendinous margin
- Arcade of Frohse (common): fibrous bands at free margin of supinator
- Leash of Henry: nerve is compressed by a vascular network of radial recurrent vessels.
Less commonly this compression is due to a space occurring lesion, such as a lipoma or haematoma, accessory muscle or fracture at distal head of radius.
Diagnosis of Radial Tunnel Syndrome
Patients with Radial Tunnel Syndrome often have intermittent pain and tenderness distal to the elbow. The symptoms relieved by tunnel injection (steroids + local anaesthetic) is diagnostic.There are no motor issues, unlike Posterior Interosseous Nerve Syndrome.
Pain is the predominant symptom in radial tunnel syndrome. In comparing the non-affected arm, classic features of this pain include:
- Localised to the extensor compartment just distal to the elbow
- Exacerbated by movement
- Can distinguish from ‘tennis elbow’ by palpating the lateral epicondylitis
- A sensory disturbance can radiate to the dorsum of the wrist
In radial tunnel syndrome, entrapment does not result in motor deficits. A sign may be slight decrease in grip strength but this is because of pain.
Radial Tunnel symptoms are usually exacerbated by3:
- Wrist flexion & pronated with the elbow extended (minimises the biceps and maximises supinator contraction)
- Wrist extended or supinated against resistance
The Middle Finger Test
- Resisted extension of the middle finger with an extended elbow
- Pushes the tendinous edge of the ECRB onto the radial nerve.
Nerve Conduction Nerve conduction studies are unreliable because4:
- PIN carries unmyelinated Group IV fibers (C-fibers, nociception) and small myelinated Group IIA afferent fibers (temperature)
- Large myelinated fibers of PIN remain normal, producing normal EMG/NCV
- Compression is intermittent
Local anaesthetic injection into the radial tunnel:
- If symptoms are received by this injection, this is diagnostic of radial tunnel syndrome5.
- Can be injected with steroid
Imaging has a limited role in radial tunnel syndrome:
- MRI may show muscle denervation, edema or atrophy along the distribution of the posterior interosseous nerve6,7
- Can visualise sites or causes of entrapment
- Posterior Interosseous Syndrome – these patients will have motor symptoms.
- Lateral epicondylitis (Tennis Elbow) – these patients will have tenderness is directly over the lateral epicondyle
- Cervical radiculopathy at C6-7 – these patients will have denervation on electrodiagnostic studies.
Treatment of Radial Tunnel Syndrome
Radial Tunnel Syndrome can be treated both non-surgically (modify movement, medication, steroid injection) and surgical decompression (various techniques and mixed results).
Commonly used non-surgical options include:
- Physiotherapy to modify movements and ensure minimal muscle atrophy
- Splinting to minimise wrist flexion to reduce radial tunnel pain
- Steroid injection, in conjunction with local anaesthetic administration, into the radial tunnel.
- Anti-inflammatory medication
A number of different surgical techniques and modifications have been described.
The key principles of decompression involves the release of:
- Medial border of ERCB
- Arcade of Froshe
- Leash of Henry
- Release Superficial head of supinator
This can be performed through different approaches:
- Volar approach between brachioradialis and FCR in the antecubital fossa. This allows good access to proximal sites of compression
- Dorsal approach between ECRL and ECRB or brachioradialis and ECRL. This provides good access to distal sites of compression8.
- Combined approach along the margins of the brachioradialis muscle through a single incision.
Outcomes of Radial Tunnel Syndrome
Current literature varies in relation to success of surgical decompression9,10. Success rates of up to 75%6 with persistant symptoms in up to 2/3rds6. In addition, the range of movement often does not change pre-operatively to post-operatively11
The worst results of decompression are seen in patients who have work-related injuries, chronic pain, and poor localization of symptoms on physical examination2.
It is important for the patient to be aware that complete pain relief and return to activities following radial tunnel surgery is not entirely predictable10.
- MICHELE A, KRUEGER F. Lateral epicondylitis of the elbow treated by fasciotomy. Surgery. 1956;39(2):277-284. https://www.ncbi.nlm.nih.gov/pubmed/13298976
- Eaton C, Lister G. Radial nerve compression. Hand Clin. 1992;8(2):345-357. https://www.ncbi.nlm.nih.gov/pubmed/1613042
- Lister G, Belsole R, Kleinert H. The radial tunnel syndrome. J Hand Surg Am. 1979;4(1):52-59. doi:10.1016/s0363-5023(79)80105-7
- Verhaar J, Spaans F. Radial tunnel syndrome. An investigation of compression neuropathy as a possible cause. J Bone Joint Surg Am. 1991;73(4):539-544. https://www.ncbi.nlm.nih.gov/pubmed/1849515
- SARHADI NS, KORDAY SN, BAINBRIDGE LC. Radial Tunnel Syndrome: Diagnosis and Management. Journal of Hand Surgery. Published online October 1998:617-619. doi:10.1016/s0266-7681(98)80015-6
- Ritts G, Wood M, Linscheid R. Radial tunnel syndrome. A ten-year surgical experience. Clin Orthop Relat Res. 1987;(219):201-205. https://www.ncbi.nlm.nih.gov/pubmed/3581572
- Ferdinand BD, Rosenberg ZS, Schweitzer ME, et al. MR Imaging Features of Radial Tunnel Syndrome: Initial Experience. Radiology. Published online July 2006:161-168. doi:10.1148/radiol.2401050028
- Barnum M, Mastey R, Weiss A, Akelman E. Radial tunnel syndrome. Hand Clin. 1996;12(4):679-689. https://www.ncbi.nlm.nih.gov/pubmed/8953288
- Atroshi I, Johnsson R, Ornstein E. Radial tunnel release. Unpredictable outcome in 37 consecutive cases with a 1-5 year follow-up. Acta Orthop Scand. 1995;66(3):255-257. doi:10.3109/17453679508995536
- Jebson P, Engber W. Radial tunnel syndrome: long-term results of surgical decompression. J Hand Surg Am. 1997;22(5):889-896. doi:10.1016/S0363-5023(97)80086-X
- Sotereanos DG, Varitimidis SE, Giannakopoulos PN, Westkaemper JG. Results of surgical treatment for radial tunnel syndrome. The Journal of Hand Surgery. Published online May 1999:566-570. doi:10.1053/jhsu.1999.0566