Radial Tunnel Syndrome

By admin On Oct 18, 2023

Ovid: 5-Minute Sports Medicine Consult, The

Pankaj Kaw

Rajwinder Deu

Basics

Description

Radial tunnel syndrome (RTS) is a compressive neuropathy (without any motor deficits) involving one of the terminal branches of the radial nerve, the posterior interosseous nerve (PIN), as it passes through the radial tunnel:
- Controversy exists as to the exact definition and existence of this condition (1,2).
- Sometimes separated into radial tunnel syndrome and PIN syndrome (3):
  - RTS: Painful condition without motor deficits
  - PIN syndrome: PIN motor neuropathy
  - Significant overlap in many cases, making some question the differentiation
The symptoms are diffuse, not well defined, overlap those of the much more prevalent lateral epicondylitis, and therefore have caused confusion as to what actually constitutes radial tunnel syndrome. A careful history and examination are required to differentiate the 2.

Epidemiology

Incidence

Incidence ranges between 1% and 2% of all peripheral nerve entrapments (1)

Risk Factors

Patients often perform repeated pronation and supination or forceful extension of the forearm.
Most common presentation is that of a heavy manual laborer. Others at risk include tennis players, swimmers, rowers, housewives, welders, conductors, and violinists (3).
Patients between 40 and 60 yrs old; no gender predilection (1,3)

Etiology

Over a distance of ∼5 cm in the radial tunnel, the PIN can be compressed at the following sites:
- Dynamically by the conjoint tendon of origin of the wrist and finger extensors
- By fibrous bands that arise between the brachioradialis and joint capsule
- By recurrent radial vessels (the leash of Henry)
- By the fibrous edge of the extensor carpi radialis brevis
- By the fibrous proximal border of the superficial portion of the supinator (arcade of Frohse)
- By the distal edge of the supinator
At any level, the PIN also may be compressed by a ganglion or lipoma, or by marked swelling of the elbow capsule resulting from rheumatoid synovitis.

Diagnosis

History

Pain in the lateral elbow and/or proximal dorsal forearm that typically radiates distally
Heaviness in upper forearm
Occasional vague dorsal wrist pain
Increase in symptoms with repetitive activities such as forearm rotation, elbow extension, and maximum wrist flexion-extension
Acute: Pain usually absent at rest, provoked by powerful grasping and lifting activities, worse at end of the day
Chronic: Baseline pain is present but is augmented by activation of the extensor-supinator group.

Physical Exam

Much overlap between lateral epicondylitis and radial tunnel syndrome exam findings
Tenderness to palpation over the radial tunnel—4 fingerbreadths distal to the lateral epicondyle—rather than at the common extensor origin on the lateral epicondyle
Symptoms are exacerbated with active supination with the elbow extended against resistance, passive pronation, passive elbow extension, resisted wrist extension, and resisted middle finger extension (“middle finger test”).

Diagnostic Tests & Interpretation

Imaging

Radiographs are helpful to exclude cervical spondylosis and degenerative changes in the elbow joint.
MRI manifestations include muscle denervation edema or atrophy along the PIN. Increased T2 signal in the muscles supplied by the PIN for acute denervation and increased T1 signal for chronic denervation (3).

Diagnostic Procedures/Surgery

Electrodiagnostic studies are generally not useful (1,4)[C].
Relief of symptoms after localized injection of an anesthetic into the radial tunnel and PIN confirms the diagnosis and is indicative of the pain relief that can be expected after surgical decompression (1,4,5)[C].

P.503

Differential Diagnosis

Lateral epicondylitis
Cervical radiculopathy
Radial neuropathy (other than in the radial tunnel)
Thoracic outlet syndrome
Posterolateral instability of the elbow
Compression of the lateral antebrachial cutaneous nerve
Osteoarthritis of the elbow
Intra-articular loose bodies
Extensor tenosynovitis

Treatment

Nonoperative treatment (4,5)[C]:
- Anti-inflammatory medications, rest, and avoidance of provocative activities
- A splint can be used to maintain forearm supination and wrist extension.
- Physical therapy focused on ergonomic retraining, stretching, and eventual strengthening of the extensor-supinator group
- Injections of local anesthetic can be helpful diagnostically and may relieve pain in the short term:
  - Addition of a corticosteroid is sometimes considered, but no data are available to support effectiveness
- Conservative treatment is highly recommended because delay of surgery has never been reported to compromise the final recovery.
Operative treatment:
- Patient selection is very important. Clear differentiation must be made between radial tunnel syndrome and lateral epicondylitis. Best surgical candidates are those who complain of pain in association with resisted supination, positive middle finger test, positive electrodiagnostic findings, and pain relief after anesthetic injection into the radial tunnel.
- Surgical decompression should be considered for patients who fail 12 wks of conservative treatment (4,5)[C].
- Multiple surgical approaches; dependent on the site of offending anatomical structures
- Rates of improvement range from 50–90% (1,4,5)[C].
- Successful surgery should result in full recovery over a period of 9 mos (1)[C].

Ongoing Care

Return to activity should be undertaken slowly as symptoms improve.
Rehabilitation program should be continued for both nonoperative and postoperative patients.

References

1. Stanley J. Radial tunnel syndrome: a surgeon's perspective. J Hand Ther. 2006;19:180–184.

2. Huisstede B, Miedema HS, van Opstal T, et al. Interventions for treating the radial tunnel syndrome: a systematic review of observational studies. J Hand Surg [Am]. 2008;33:72–78.e3.

3. Bencardino JT, Rosenberg ZS. Entrapment neuropathies of the shoulder and elbow in the athlete. Clin Sports Med. 2006;25:465–487, vi–vii.

4. Henry M, Stutz C. A unified approach to radial tunnel syndrome and lateral tendinosis. Tech Hand Up Extrem Surg. 2006;10:200–205.

5. Tsai P, Steinberg DR. Median and radial nerve compression about the elbow. J Bone Joint Surg Am. 2008;90:420–428.

Codes

ICD9

354.3 Lesion of radial nerve