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Ulnar Nerve Compression PDF Print E-mail
Background
As the ulnar nerve emerges from the medial cord of the brachial plexus and travels down the upper extremity, 5 potential compression sites have been identified: the arcade of Struthers, medial intermuscular septum, medial epicondyle, cubital tunnel, and the flexor carpi ulnaris (FCU) aponeurosis. Entrapment of the ulnar nerve at the cubital tunnel is the second most common compression neuropathy in the upper extremity after carpal tunnel syndrome.1 Despite the widespread prevalence of cubital tunnel syndrome, however, there is no general consensus on the best treatment for this condition.

Anatomy
The roof of the cubital tunnel is a thickened transverse band between the 2 heads of the FCU (Osborne’s ligament), with the medial collateral ligament of the elbow, the elbow joint capsule, and the olecranon making up the floor. The medial antebrachial cutaneous nerve (MACN) lies approximately 1.8 cm proximally from the medial humeral epicondyle and emerges distally at 3.1 cm from the epicondyle.2 This places the nerve at risk of iatrogenic injury during surgical approaches for cubital tunnel release. Injury to the MACN can cause a painful scar, hyperalgesia in the forearm, and neuromas that may be severe enough to limit elbow range of motion.2

History and Physical Examination
Patients with cubital tunnel syndrome typically complain primarily of numbness and paresthesias in the small and ring fingers. Intrinsic muscle weakness and atrophy cause hand and grip problems, including difficulty typing, opening bottles, and buttoning buttons.1 A study looking at patients with cubital and carpal tunnel noted that 40% of patients with cubital tunnel had muscle atrophy upon initial presentation, compared with 10% in patients with carpal tunnel.3 A thorough history can rule out old trauma and determine other potential etiologies for the nerve compression. 

During physical examination, it is important to correctly identify the specific site of ulnar nerve compression within the upper extremity or the neck. The Tinel’s test is performed by the physician applying several taps to the patient’s ulnar nerve just proximal to the cubital tunnel and assessing for the reproduction of the patient’s symptoms. In the elbow flexion test, the patient’s elbow is placed in maximum flexion with the forearm in flexion and the wrist in neutral position. After waiting 60 seconds, the test is considered positive if the patient reports symptoms along the ulnar nerve distribution. Novak et al4 evaluated the screening values of specific provocation tests for cubital tunnel compression (Table 1).
Table 1
Physical examination findings consistent with severe ulnar nerve compression include Duchenne’s sign (hyperextension of the proximal phalanx with flexion of the middle and distal phalanges of the ring and small fingers secondary to paralysis of the lumbrical and interosseoi muscles); Masse’s sign (flattening of the dorsal transverse metacarpal arch secondary to hypothenar muscle paralysis); Wartenberg’s sign (ulnar deviation of the small finger secondary to interosseous and adductor weakness); and Froment’s sign (patients pinch through flexion of the distal phalanx of the thumb against the index finger to compensate for adductor weakness).1 It is also important to determine whether the ulnar nerve subluxates over the medial epicondyle with elbow range of motion. Although ulnar subluxation at the elbow has been reported to be normal in 16% of the population,5 some surgeons believe that elbow pain and paresthesias in the ulnar nerve distribution in patients who have ulnar subluxation should be treated differently than cubital tunnel without ulnar subluxation.6

Radiographs of the elbow can help rule out other suspected pathology. There may be evidence of prior trauma (supracondylar humerus fracture) or elbow arthritis with osteophyte impingement on the cubital tunnel.1 Electrodiagnostic studies can help confirm the specific site of compression, identify other potential compression sites, and rule out a double-crush phenomenon. Electromyographic and nerve conduction studies can have a false-negative rate >10%.7 Ulnar nerve compression is commonly classified using the McGowan classification,8 with modifications made by Dellon9 (Table 2).
Table 2 Nonsurgical Management
Nonsurgical treatment is the first line of management for most patients presenting with cubital tunnel syndrome, although patients with established muscle atrophy are typically offered operative intervention without a trial of nonsurgical management. Nonsurgical modalities include activity modification, splints to obstruct maximum and repetitive flexion, and physical therapy (nerve gliding exercises).1

In a randomized, prospective study, Svernlöv et al10 found no significant difference in visual analog pain scales, strength measurements, or neurophysiological examinations at 6 months between patients treated with night bracing, nerve gliding, and a control group that only received education about the pathoanatomy of cubital tunnel syndrome. A recent case series in patients with mild to moderate cubital tunnel syndrome showed the added benefit of nerve sliding and tensioning techniques to a rehabilitation program, with improvements in grip and pinch scores and subjective pain and sensation at 12 months.11

Surgical Management
Following failure of nonoperative management, patients are offered surgical decompression of the ulnar nerve within the cubital tunnel. There is no gold standard surgical treatment that has been identified in the current literature on cubital tunnel syndrome. The most common operations for ulnar entrapment at the elbow include simple in situ decompression, anterior subcutaneous transposition, submuscular transposition, and medial epicondylectomy. In performing in situ decompression, Osborne’s ligament and the superficial and deep fascia surrounding the FCU are released while maintaining the ulnar nerve within its bed (Figure 1).
Figure 1 
The theory behind the transposition surgeries is to circumferentially dissect the ulnar nerve from all of its soft tissue surroundings and relocate it to avoid the recurrence of compression around the nerve. Anterior transposition seeks to move the ulnar nerve anterior to the medial epicondyle (the elbow axis of flexion), which is believed to decrease the tension on the nerve. Typically, a new sling is made around the ulnar nerve with subcutaneous tissue sutured to the fascia over the medial epicondyle, or the ulnar nerve is placed beneath the flexor pronator mass.1 Some authors believe that to completely eliminate the strain seen by the ulnar nerve with elbow flexion, a partial medial epicondylectomy must be performed in which the medial epicondyle is typically removed from the metaphyseal-diaphyseal junction to the distal portion of the supracondylar ridge.12

Finally, as the popularity of endoscopic procedures has increased within the past 20 years, various techniques for the decompression of cubital tunnel have been developed. All of the systems use an incision over the ulnar nerve at the condylar groove, which is significantly shorter than the one needed in the traditional open surgeries. Each system has its own particular instrumentation to visualize and protect the ulnar nerve while releasing the surrounding compression sites.

Multiple authors have found no significant difference in McGowan grade improvement or subjective outcome between ulnar decompression in situ and anterior transposition.13-15 Because simple decompression is a less expensive procedure than subcutaneous transposition, it has been found to have a higher utility.16 A recent Cochrane systematic review found no significant difference in clinical or neurophysiological improvement between simple decompression and transposition (subcutaneous and submuscular) of the ulnar nerve (RR 0.93, 95% CI, 0.80–1.08).17 In a retrospective chart review with a minimum 2 year follow-up, Charles et al18 observed no significant difference between submuscular ulnar nerve transposition with musculofascial lengthening or subcutaneous ulnar nerve transposition with a dermofascial sling in subjective results, recovery of sensory function, or intrinsic or flexor digitorum profundus muscle strength. The authors did observe a trend toward better recovery for patients younger than 45 years old and patients who received surgery within 6 months of symptom onset. 

A recent study showed no significant difference in McGowan grade improvement or grip or pinch strength between in situ decompression, partial epicondylectomy, or anterior subcutaneous transposition.19 In a retrospective review of patients with a mean follow-up of 3 years following partial medial epicondylectomy, 60% of the patients improved from their preoperative McGowan score and a significant postoperative reduction in pain as measured with a VAS scale.20 A subcutaneous hematoma was the most common complication reported by the authors.

Recent case studies have shown promising results with endoscopic cubital tunnel decompression. In several studies, there was an improvement in McGowan classification and patient satisfaction without an increase in iatrogenic nerve injuries or conversion to open procedures.21-23

Complications
Transposition (subcutaneous or submuscular) has been shown to have a 3 times higher relative risk of wound infections compared with simple decompression.17 In a prospective, randomized trial comparing simple decompression with anterior subcutaneous transposition, Bartels et al13 found a significantly higher level of complications (including infection, elbow pain and seroma) in the transposition group. An increased incidence of wound complications after transposition, compared with in situ decompression, has also been observed by other authors.

Complications after a partial medial epicondylectomy include persistent tenderness at the osteotomy site, valgus instability, heterotopic ossification, and loss of the protective role of the medial epicondyle to the ulnar nerve.19 Schnable et al24 suggested that the persistent discomfort at the site of operation was secondary to injury to the skin nerves and scar irritation, in addition to sequelae from the procedure itself. In contrast, the extensive dissection of the vascular mesoneurium from the nerve that is performed during anterior subcutaneous transposition leads to an increased rate of ulnar nerve devascularization that is not seen with medial epicondylectomy. 

Although Oertel et al22 found no difference in success rate after endoscopic cubital tunnel decompression in patients with a body mass index <30 kg/m2 or >30 kg/m2, they did find the surgery was longer and more difficult in obese patients, most likely secondary to an abundance of subcutaneous fat tissue. There is also an increased learning curve for the performance of endoscopic surgery that may increase the rate of initial complications.21 

Recurrent Symptoms After Surgery
Continued symptoms following operative intervention are usually secondary to incomplete decompression or perineural fibrosis. It is, therefore, recommended that all 5 sites of potential ulnar nerve entrapment are identified and released during the initial surgery. The operating physician should directly slide a finger both proximally and distally along the length of the ulnar nerve to ensure there are no residual sites of entrapment prior to closure of the wound.26 Early postoperative mobilization is also recommended to prevent the potential for scar traction on the nerve and to decrease the rate of perineural scarring. Rogers et al27 found that revision surgery was successful in relieving pain and paresthesias, although the motor and sensory recovery was variable depending upon the severity of the compression.  

Many surgeons reserve submuscular transposition as an option for revision cubital tunnel surgery. In this situation, an external neurolysis of the ulnar nerve is started proximal to the previous surgical excision, and the ulnar nerve is transposed deep to the flexor-pronator muscle mass. The nerve may be reattached via a musculofascial lengthening flap, in which the fascia of the flexor-pronator mass is lengthened to create a greater space for the ulnar nerve in its new location, permit reconstruction of the flexor-pronator muscle mass without tension, and allow the patient to begin postoperative range of motion immediately following surgery.28  

Kokkalis et al29 advocated for the application of a scar-tissue barrier in revision cubital tunnel decompression to improve the chances for a successful outcome. Using an autogenous saphenous vein graft wrap in patients who had previously undergone at least 1 previous revision operation, a significant reduction in visual analog scale pain score was seen, as well as an increase in average grip strength at a mean follow-up of 44 months. 

References

 

  1. Palmar BA, Hughes TB. Cubital tunnel syndrome. J Hand Surg Am. 2010;35(1):153-163.
  2. Lowe JB III,, Maggi SP, Mackinnon, SE. The position of crossing branches of the medial antebrachial cutaneous nerve during cubital tunnel surgery in humans.  Plast Reconstr Surg. 2004;114(3):692-696.
  3. Mallette P, Zhao M, Zurakowski D, Ring D. Muscle atrophy at diagnosis of carpal and cubital tunnel syndrome. J Hand Surg Am. 2007;32(6):855-858.
  4. Novak CB, Lee GW, Mackinnon SE, Lay L. Provocative testing for cubital tunnel syndrome. J Hand Surg Am. 1994;19(5):817-820.
  5. Childress HM. Recurrent ulnar-nerve dislocation at the elbow. J Bone Joint Surg Am. 1956;38-A(5):978-984.
  6. Richard MJ, Messmer C, Wray WH, Garrigues GE, Goldner RD, Ruch DS. Management of subluxating ulnar nerve at the elbow. Orthopedics. 2010;33(9):672.
  7. Greenwald D, Blum LC III, Adams D, Mercantonio C, Moffit M, Cooper B. Effective surgical treatment of cubital tunnel syndrome based on provocative clinical testing without electrodiagnostics. Plast Reconstr Surg. 2006;117(5):87e-91e. 8
  8. McGowan AJ. The results of transposition of the ulnar nerve for traumatic ulnar neuritis. J Bone Joint Surg Br. 1950;32-B(3):293-301.
  9. Dellon AL. Review of treatment results for ulnar nerve entrapment at the elbow. J Hand Surg Am. 1989;14(4):688-700.
  10. Svernlöv B, Larsson M, Rehn K, Adolfsson L. Conservative treatment of the cubital tunnel syndrome. J Hand Surg Eur Vol.  2009;34(2):201-207.
  11. Oskay D, Meric A, Kirdi N, Firat T, Ayhan C, Leblebicioğlu G. Neurodynamic mobilization in the conservative treatment of cubital tunnel syndrome: Long-term follow-up of 7 cases. J Manipulative Physiol Ther. 2010;33(2):156-163.
  12. Hicks D, Toby EB. Ulnar nerve strains at the elbow: the effect of in situ decompression and medial epicondylectomy. J Hand Surg Am. 2002;27(6):1026-1031.
  13. Bartels RH, Verhagen WI, van der Wilt GJ, Meulstee J, van Rossum LG, Grotenhuis JA. Prospective randomized controlled study comparing simple decompression versus anterior subcutaneous transposition for idiopathic neuropathy of the ulnar nerve at the elbow: Part 1. Neurosurgery. 2005;56(3):522-530.
  14. Biggs M, Curtis JA. Randomized, prospective study comparing ulnar neurolysis in situ with submuscular transposition. Neurosurgery. 2006;58(2):296-304.
  15. Macadam SA, Gandhi R, Bezuhly M, Lefaivere KA. Simple decompression versus anterior subcutaneous and submuscular transposition of the ulnar nerve for cubital tunnel syndrome: a meta-analysis. J Hand Surg Am. 2008;33(8):1314.e1-12.
  16. Macadam SA, Bezuhly M, Lefaivre KA. Outcomes measures used to assess results after surgery for cubital tunnel syndrome: a systematic review of the literature. J Hand SurgAm. 2009;34(8):1482-1491.e5.
  17. Caliandro P, La Torre G, Padua R, Giannini F, Padua L. Treatment for ulnar neuropathy at the elbow. Cochrane Database Syst Rev. 2011;16(2):CD006839.
  18. Charles YP, Coulet B, Rouzaud JC, Daures JP, Chammas M. Comparative clinical outcomes of submuscular and subcutaneous transposition of the ulnar nerve for cubital tunnel syndrome. J Hand Surg Am. 2009;34(5):866-874.
  19. Mitsionis GI, Manoudis GN, Paschos NK, Korompilias AV, Beris AE. Comparative study of surgical treatment of ulnar nerve compression at the elbow. J Shoulder Elbow Surg. 2010;19(4):513-519.
  20. Schnabl SM, Killslinger F, Schramm A, et al. Subjective outcome, neurophysiological investigations, postoperative complications and recurrence rate of partial medial epicondylectomy in cubital tunnel syndrome. Arch Orthop Trauma Surg. 2011;131(8):1027-1033.
  21. Mirza A, Reinhart MK, Bove J, Litwa J. Scope-assisted release of the cubital tunnel. J Hand Surg Am. 2001;36(1):147-151.
  22. Oertel J, Keiner D, Gaab MR. Endoscopic decompression of the ulnar nerve at the elbow. Neurosurgery. 2010;66(4):817-824.
  23. Stadie AT, Keiner D, Fischer G, Conrad J, Welschehold S, Oertel J. Simple endoscopic decompression of cubital tunnel syndrome with the Agee system: anatomic study and first clinical results. Neurosurgery. 2010;66(suppl 6):325-331.
  24. Schnabl SM, Kisslinger F, Schramm A, et al. Objective outcome of partial medial epicondylectomy in cubital tunnel syndrome. Arch Orthop Trauma Surg. 2010;130(12):1549-1556.
  25. Ogata K, Manske PR, Lesker PA. The effect of surgical dissection on regional blood flow to the ulnar in the cubital tunnel. Clin Orthop Relat Res. 1985;193:195-198.
  26. MacKinnon SE. Comparative clinical outcomes of submuscular and subcutaneous transposition of the ulnar nerve for cubital tunnel syndrome. J Hand Surg Am. 2009;34(8):1574-1575.
  27. Rogers MR, Bergfield TG, Aulicino, PL. The failed ulnar nerve transposition. Etiology and treatment. Clin Orthop Relat Res. 1991;269:193-200.
  28. Williams EH, Dellon AL. Anterior submuscular transposition. Hand Clin. 2007;23(3):345-358.
  29. Kokkalis ZT, Jain S, Sotereanos DG.  Vein wrapping at cubital tunnel for ulnar nerve problems.  J Shoulder Elbow Surg.  2010;19:91-97.
 

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