Ulnar Nerve Release

Ulnar nerve release is performed for cubital tunnel syndrome with positive clinical and instrumental signs (on nerve conduction studies and electromyography [EMG]) of compression at the elbow.

In 1957, Osborne described simple decompression of the ulnar nerve achieved by cutting the ligament subsequently named after him (the Osborne fascia or band). This ligament is part of the fibrous arcade, a fascia running between the two heads of the flexor carpi ulnaris (FCU). Osborne divided this fibrous band connecting the medial epicondyle and the olecranon and reported results favorable to those of the anterior transposition procedures, which at that time represented the standard of surgical care for compressive ulnar neuropathies at the elbow.

In his report, Osborne observed that the ulnar neuritis was a result of direct compression of the nerve within the tunnel and that the flexion of the elbow exacerbated this condition.

The compression causes progressive disruption of the vascular supply to the nerve. ^[1] In a normal elbow, the nerve undergoes tensile forces that increase the nerve strain; when the elbow is flexed, the nerve is pushed against its bed, and upon extension, the nerve diverges away from the elbow.

The ulnar nerve at the elbow could be compressed at different sites, as follows:

• Proximal to the cubital tunnel at the level of the medial epicondyle - The arcade of Struthers is a canal made up by the intermuscular septum, the internal brachial ligament, and the triceps; at this site, between the middle and distal thirds of the humerus, the ulnar nerve travels from the anterior to the posterior compartment of the arm
• Distal to the cubital tunnel - The compression might be caused by the arcuate ligament of Osborne that runs between the two heads of origin of the FCU and therefore between the medial epicondyle of the humerus and the medial aspect of the olecranon

Ulnar nerve compression at the elbow is the second most common compression neuropathy in the upper limbs (after median nerve compression in the carpal tunnel), with an incidence of 25 per 100,000 population per year. The condition is more common in men than in women, possibly as a consequence of the smaller coronoid process of the ulna and the more abundant subcutaneous fat tissue in women.

Nontraumatic ulnar nerve compressive neuropathy is usually associated with arthritis, and there are no other known causes.

Ulnar nerve release is indicated for cubital tunnel syndrome ^[2] with positive clinical and instrumental signs (on nerve conduction studies and EMG) of compression at the elbow.

Contraindications for ulnar nerve release include the following:

• Valgus deformity of the elbow
• Tumors
• Ganglion cyst
• Osteophytes
• Elbow instability or deformity

Relative contraindications include recurrent neuropathies.

A delayed diagnosis increases the risk of chronic neuritis and pain due to repeated injuries to the nerve, leading to intraneural scar formation. Surgical treatment in this case is less effective in the long term. Negative prognostic factors include severe, long-lasting neuropathy accompanied by diminished nerve conduction velocity (NCV).

A randomized controlled trial of 70 patients with mild or moderate but not necessarily electrophysiologically proven cubital tunnel syndrome sought to assess the efficacy of conservative therapy at 6 months. ^[3] The study subjects were divided into the following three groups:

• Nocturnal elbow splinting for 3 months plus written information
• Nerve gliding exercises plus written information
• Written information only

The attrition rates among the three groups were high and equal, with 13 patients unavailable for follow-up and six others requesting surgical decompression. The authors found that written information improved occupational activities and pain, but the addition of splinting or exercises did not confer any further benefit. ^[3]

Medial epicondylectomy versus anterior ulnar nerve transposition for ulnar neuropathy at the elbow was examined in a randomized controlled trial of 47 operations. ^[4] Neurologic assessment of the hand and elbow at a minimum of 1 year showed no clinical difference between the two groups, though mild hand pain was more common after transposition. Patient satisfaction seemed better after medial epicondylectomy. ^[4]

Several randomized controlled trials have compared clinical and nerve conduction outcomes of simple decompression versus anterior ulnar nerve transposition in patients with electrophysiologically proven ulnar neuropathy at the elbow. ^{[5, 6, 7, 8]}

Bartels et al compared simple decompression with anterior subcutaneous transposition in 152 patients. ^[5] At 1-year follow-up, equivalent good or excellent clinical improvement was noted in both groups (65% decompression, 70% subcutaneous), though the transposition group had significantly higher rates of complications (10% decompression, 31% subcutaneous). An economic analysis of this trial revealed that simple decompression cost significantly less than transposition, mainly owing to significantly shorter operative time and sick leave. ^[9]

Nabhan et al also examined simple decompression versus anterior subcutaneous transposition in a randomized controlled trial of 66 patients with 9-month follow-up. ^[8] The two procedures achieved similar improvements in clinical findings and NCVs across the elbow.

Biggs and Curtis ^[6] and Gervasio et al ^[7] compared simple decompression with anterior submuscular transposition. At 1-year follow-up, Biggs and Curtis reported a nonsignificant difference in neurologic improvement between groups in their cohort of 44 patients (61% decompression, 67% submuscular), with a trend for deep wound infection in the transposition group (0% decompression, 14% submuscular). ^[6]  At 6-month follow-up, Gervasio et al reported a nonsignificant difference in good or excellent clinical and electrophysiologic outcomes between groups in their cohort of 70 patients (80% decompression, 83% submuscular), with no major complications observed. ^[7]

The data from these studies were cumulatively evaluated in a 2011 Cochrane review. The meta-analysis found that both simple decompression and anterior transposition procedures improved symptoms and nerve function and that no significant difference in postoperative clinical or electrophysiologic outcomes existed; however, transposition resulted in higher rates of deep and superficial wound infection. ^[10]

These findings suggested that conservative therapy would be appropriate for patients with mild or moderate symptoms of ulnar neuropathy at the elbow. In more severe cases requiring surgical intervention, clinical improvement might be expected in approximately 70% of cases. ^[10] No one surgical technique was shown to be superior to another.

The evidence from these randomized controlled trials led to increasing advocacy for simple decompression as the operation of choice, in view of its shorter operating time, potential economic benefits, and association with fewer complications. 

In a 2014 study by Martin et al, 145 patients underwent retractor-endoscopic carpal tunnel release (n = 47), endoscopic in-situ decompression of the ulnar nerve (n = 55), or endoscopic anterior transposition of the ulnar nerve (n = 52) between 2000 and 2010; nine patients underwent bilateral procedures. ^[11] Both objective results (via independent examination at 24 months) and subjective results (via questionnaire) were recorded, as follows:

• Endoscopic carpal tunnel release - 59.6% had excellent objective results, 21.2% good results, 12.8% fair results, and 6.4% poor results; 85% had subjective improvement
• Endoscopic in-situ decompression - 56.4% had excellent objective results, 32.7% good results, 9.1% fair results, and 1.8% poor results; 72.7% had subjective improvement
• Endoscopic anterior transposition of the ulnar nerve - 48.1% had excellent objective results, 26.9% good results, 23.1% fair results, and 1.9% poor results; 65.4% had subjective improvement

The investigators found that the retractor-endoscopic approach yielded good long-term results after carpal tunnel release, in-situ decompression, and anterior subcutaneous transposition of the ulnar nerve, with outcomes showing some correlation with the duration of preoperative symptoms. ^[11]

A 2016 update of the aforementioned 2011 Cochrane review found that the available comparative treatment evidence was insufficient to support a multiple-treatment meta-analysis to identify the best treatment for idiopathic ulnar neuropathy at the elbow on the basis of clinical, neurophysiologic, and imaging characteristics. ^[12]  The study was unable to define when to treat this condition conservatively or surgically. Simple decompression and decompression with transposition appeared equally effective, even with severe nerve impairment, though the latter procedure was associated with more deep and superficial wound infections. Patients undergoing endoscopic surgery were more likely to have a hematoma.

A 2018 prospective study of 45 patients randomly assigned to undergo either endoscopic (n = 22) or open surgery (n = 23) for decompression of the ulnar nerve found the two methods to be equally effective in the treatment of cubital tunnel syndrome. ^[13]  Patients who underwent open decompression experienced notably higher levels of postoperative chronic scar pain; satisfaction with scarring was greater in the endoscopy group. Operating time was significantly longer in the endoscopy group.

In a 2018 review comparing outcomes of open decompression, endoscopic decompression, minimal incision, subcutaneous transposition, intramuscular transposition, and submuscular transposition for cubital tunnel syndrome, Carlton et al found that all of these approaches appeared to be effective, but none demonstrated universal superiority to the others. ^[14] The only consensus reached was that transposition seemed preferable where the ulnar nerve tends to subluxate on either preoperative or intraoperative examination.