The radial nerve carries both motor and sensory nerve fibers from the brachial plexus into the distal forearm and hand. During its winding path there are multiple areas of compression that may impinge upon the radial nerve causing distinct symptoms depending on the point of compression. Interestingly, compression of the posterior interossesous nerve (PIN) within the radial tunnel can cause two contrasting syndromes known as PIN syndrome and radial tunnel syndrome (RTS). Within the radial tunnel there are multiple potential areas of compression including the leash of Henry, the extensor carpi radialis brevis (ECRB) muscle, fibrous bands between the brachialis and brachioradialis muscles, the distal edge of the supinator muscle, mass occupying lesions (lipomas, ganglions, etc.), and most commonly the Arcade of Frohse.
Radial nerve entrapment commonly occurs in patients who participate in occupational and recreational activities. Patients that present with symptoms of radial tunnel syndrome (RTS) can be difficult to evaluate. Typically, patients will have intense pain over the lateral epicondyle that radiates distally and radially towards the radial styloid and thumb. Additionally, patients will often complain of pain over the mobile wad that is exacerbated with physical activity, especially lifting activities and activities involving forearm rotation, especially with elbow extension, wrist flexion, and forearm pronation, i.e. opening door knobs.
Separating these symptoms from those of lateral epicondylitis can be difficult and challenging and even 5-10% of patients can present with concomitant RTS and lateral epicondylitis. The initial evaluation including history and physical exam is crucial in properly treating these patients as most imaging modalities will not reveal any abnormalities. Interestingly, the history of patients with RTS will not involve any weakness, inability to grip or hold on to objects, or difficulty extending the wrist or fingers as this is the typical presentation of PIN syndrome, which involves that same nerve and area of entrapment but with purely motor symptoms.
Physical symptoms of RTS are on a spectrum from incredibly subtle with simply pain just distal to the lateral epicondyle to severe debilitating pain with forearm pronation, wrist flexion, or elbow extension. Typically, patients will have some tenderness over the dorsal forearm distal to the lateral epicondyle, right where the PIN traverses the deep and superficial heads of the supinator muscle. Typically, this has been described as pain about 3-4 cm distal to the lateral epicondyle; however, this is not always the case and is variable depending on patient body habitus and girth. (Figure 1)
Interestingly, it has been the experience of this author that the epicenter of painful stimulus can be located by taking 80% of the transepicondylar distance (the distance between the medial and lateral humeral epicondyles) and applying pressure at this distance from the lateral epicondyle pointing towards the radial styloid. Additionally, pain can often be reproduced with resisted supination, passive pronation with wrist flexion, or resisted long finger extension, which is in direct contrast to resisted wrist extension, which is typically a symptom of lateral epicondylitis.
Once the practitioner suspects RTS, the most specific test used to identify its presence is the administration of a local corticosteroid into the radial tunnel with relief of symptoms. When this is performed, it has been suggested that the use of a short-acting local anesthetic can be used to help determine correct placement by producing a confirmatory transient PIN palsy. Imaging and electromyogram/nerve conduction (EMG/NC) studies have minimal roles in the evaluation of RTS.
Magnetic resonance imaging (MRI) is not typically indicated for RTS however may show a space occupying lesion (tumor, lipoma, ganglion, bursitis, etc.) or evidence of lateral epicondylitis. In the event of PIN syndrome a lipoma should be of high suspicion and a MRI obtained to rule this out. EMG and NC studies are typically inconclusive as sensory nerve fibers are not evaluated on these studies. However, they may show in rare instances either undetected PIN syndrome or evidence of cervical radiculopathy.
Treatment of RTS syndrome is a difficult task. No good studies have been undertaken to determine the best treatment algorithm for RTS syndrome. Typically, treatment begins conservatively with activity modification, non-steroidal anti-inflammatory drugs (NSAIDs), stretching, and static splinting. Patients should avoid positions that place the elbow into extension, the wrist into flexion, and the arm into pronation, much like typing on a keyboard.
Indications for Surgery
Should conservative treatment fail to abate the patient’s symptoms, operative decompression can be attempted. It has been suggested rather arbitrarily that conservative treatment be undertaken for a year prior to surgical intervention.
Numerous surgical techniques have been described for surgical exploration and surgical determination of the site of radial nerve compression. Of those described, the brachioradialis splitting approach is typically the most utilized.
In this author’s practice:
The patient is positioned supine, with the operative arm/forearm on a narrow arm board.
A tourniquet is placed on the most proximal part of the arm, dependent upon the patient habitus. The arm is elevated for 60 seconds without using an exsanguination sleeve/wrap, and the tourniquet is inflated to 250 mmHg (minimum 100 mmHg above patient’s systolic blood pressure).
The arm is placed in a neutral rotation position, with the thumb pointing in the same plane as the humerus.
A line is marked on the forearm, with a surgical marking pen, connecting the apex of the lateral epicondyle to the radial styloid process. An incision is then made with a center point equivalent to 80% of the transepicondylar distance, and extended 2 cm proximally and distally along the line drawn (Figure 2).
Following the full thickness skin incision, the antebrachial fascia is incised and the muscle fibers of the brachioradialis muscle are split using blunt dissection.
Once the brachioradialis split dissection is completed, the superficial fibers of the supinator will become visible, as noted by their different fiber direction. The surgeon will now be able to palpate the PIN moving, with a digit placed gently on the supinator, while pronating-supinating the forearm. The nerve will be felt to be moving beneath the palpating digit.
Once the precise location of the PIN has been identified, the superficial leaf of the supinator can be carefully incised, in line with the nerve course, and elevated away from the nerve beneath. The nerve can then be traced proximally and distally, with a combination of sharp and blunt dissection methods to release any compressive sites. (Figure 3)
Fibrous bands such as the aponeurotic proximal edge of the supinator can simply incised, but arterial and venous sites of compression may need to be tied off or cauterized with a bipolar radiofrequency probe.
Once all sites of compression have been removed, the tourniquet should be deflated, in order to identify any potential bleeding vessels, and prevent any potential post-operative bleeding. Local anaesthetic is infiltrated into the incision, and the patient is pre-warned that a wrist drop will be experienced until the local anaesthetic effect subsides, between 2-6 hours.
Post-operative instructions include full active and passive range of motion, analgesia as required, and cryotherapy to help reduce swelling and improve pain control. (Figure 4)
Pearls and Pitfalls of Technique
When trying to identify sites of compression of the PIN deep to the superficial supinator leaf, gentle percussion of the nerve tract will result in wrist reflex dorsiflexion at a zone of irritation.
When trying to locate the PIN in the radial tunnel, occasionally small arborizing branches sometimes perforate the superficial leaf of the supinator. These small branches, if carefully traced proximally, will help to lead the dissection back to the main nerve trunk.
When a patient does not expect a wrist drop after surgery with local anaesthetic infiltration for post-operative pain control, it leads to much dissatisfaction. So after a full decompression, and local anaesthetic infiltration, inform the patient of a temporary wrist drop.
If the wound is closed without checking for small vessel bleeding, the closed compartment with an increasing volume of bleeding may lead to secondary PIN compression or compartment syndrome. Hence, deflate the tourniquet after PIN decompression and cauterize all bleeding vessels before wound closure.
Radial nerve neuropraxia
Secondary PIN compression
There are no currently accepted/published post-operative protocols for radial tunnel rehabilitation. The use of post-operative splinting in supination may help to decrease symptoms in the immediate post-operative period when swelling is expected to be a major contributor to continued symptoms. Otherwise, after healing has occurred, the patient may be released to gradually increase their activity. Some patients may require rehabilitation with gradual stretching and strengthening exercises due to either prolonged immobilization causing continued weakness or disuse from the clinical entity itself.
Outcomes/Evidence in the Literature
Radial tunnel release has been shown in numerous studies to be effective in relieving symptoms in 67-92% of patients, however subsequent studies have revealed only 40% patient satisfaction with their surgery and even worse satisfaction if corresponding litigation or worker’s compensation claims are active. Of recent note, the treatment of RTS syndrome can be troublesome with the possibility of concomitant disease processes such as lateral epicondylitis, cervical radiculopathy, and double crush phenomena all having equally poor outcomes.
Huisstede, B.. “Interventions for Treating the Radial Tunnel Syndrome: A Systematic Review of Observational Studies”. The Journal of Hand Surgery. vol. 33. 2008. pp. 72.e71-72.e10.
Jebson, P. J. L., Engber, W. D.. “Radial tunnel syndrome: Long-term results of surgical decompression”. The Journal of Hand Surgery. vol. 22. 1997. pp. 889-896.
Sarhadi, N. S.. “Radial tunnel syndrome: Diagnosis and management”. The Journal of Hand Surgery: British & European. vol. Volume 23. 1998. pp. 617-619.
Sotereanos, D. G.. “Results of surgical treatment for radial tunnel syndrome”. The Journal of Hand Surgery. vol. 24. 1999. pp. 566-570.
Patients presenting with signs of symptoms of RTS should have a thorough history and physical performed, focusing on site of pain, movements exacerbating symptoms, and possible alternative diagnoses or concomitant disease processes. Patients with radial tunnel syndrome should initially be treated conservatively with activity modification and possibly splinting. Should these fail treatment, steroid injections may be entertained to both treat and diagnose the problem. Prior to surgical intervention, alternative diagnoses and concomitant disease processes should be investigated prior to surgical intervention. Ultimately, surgical treatment can be performed if adequate symptom relief fails to be achieved with non-operative methods. Radial tunnel release surgery has been shown to be effective in relieving symptoms however many patients may continue to be dissatisfied, especially if corresponding litigation or worker’s compensation claims are present.
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