Cubital Tunnel Syndrome

The Problem

The ulnar nerve passes in a subcutaneous position posterior to the medial epicondyle in the elbow. Cubital tunnel syndrome (CuTS) is defined as the compression of the ulnar nerve in this anatomic region. It is the second most common compressive neuropathy of the upper extremity after carpal tunnel syndrome with an incidence reported at 24.7 per 100,000. Symptoms are exacerbated with elbow flexion, as the ulnar nerve is stretched and the diameter of the cubital tunnel is decreased. There are many areas where the ulnar nerve may be entrapped, but the most common are the Arcade of Struthers, the medial intramuscular septum, the cubital tunnel retinaculum (flexor carpi ulnaris aponeurosis), and the deep flexor-pronator aponeurosis. Mass lesions (ganglions, schwanommas) may also compress the nerve anywhere along its course.

Clinical Presentation

Cubital tunnel syndrome most commonly presents with numbness in the small and ring finger and/or medial elbow pain. Patients typically complain of numbness and paresthesias of the little finger and ulnar aspect of the ring finger, with symptoms often activity-induced and nocturnal. Medial elbow pain may be the only or predominant symptom. Patients commonly complain of medial epicondylar pain that radiates into the ulnar forearm. Varying amount of ulnar hand and wrist pain may also be present. Complaints of hand grip weakness or clumsiness (difficulty buttoning buttons, opening bottles, typing) may figure prominently.

On exam, a patient with mild cubital tunnel syndrome will demonstrate no objective findings. A patient with more advanced CuTS may have diminished 2-point discrimination in the ulnar 2 digits and corresponding areas of the dorsal and palmar hand. Advanced cases may demonstrate several physical exam findings. Atrophy of the intrinsics, most obvious in the first dorsal web space, may be present. Ulnar claw hand- MCP hyperextension and PIP flexion of the ulnar two digits- develops due to atrophy of the interossei and 3rd and 4th lumbricals. Froment’s sign is the flexion of the thumb IP joint against the index finger PIP joint to pinch a piece of paper in between the index finger and thumb. This abnormal pinch occurs due to adductor pollicis atrophy. Wartenberg’s sign is a chronically abducted little finger that may be seen with interosseus and lumbrical atrophy; the extensor digiti minimi, inserting on the ulnar aspect of the small finger, works unopposed and makes small finger adduction difficult.

Provocative testing can be very sensitive for CuTS, with the highest sensitivity found in the combined elbow flexion- direct pressure test. Tinel’s, elbow flexion, direct pressure, and scratch-collapse are other provocative tests that are frequently positive in a patient with cubital tunnel syndrome.

Diagnostic Workup

Clinical findings are the most important factors in making a diagnosis of cubital tunnel syndrome, and some authors advocate a surgical procedure for symptomatic patients who fail conservative therapy without the use of other diagnostic modalities. However, most surgeons will have electrodiagnostic studies done in order to confirm the diagnosis of CuTS and to evaluate for other possible causes of ulnar nerve symptoms. These studies enable localization of the compression site and may help determine prognosis. Abnormal nerve conduction is considered to be less than 50m/s, or a 10 m/s or 20% reduction in amplitude compared to the contralateral side. False negative results occur in more than 10% of cases.

Elbow X-ray is a useful diagnostic modality in cases of past elbow fractures or trauma; it may demonstrate arthritis or posttraumatic deformities that can contribute to nerve compression. MRI may identify nerve compression before electrophysiologic abnormalities become apparent, though no studies have evaluated its utility. In younger patients it can help evaluate the possibility of aberrant anatomy (anconeus epitrochlearis, etc.) contributing to nerve compression. Ultrasound can also help find anatomical cubital tunnel abnormalities like accessory muscles, osteophytes, ganglions, or nerve subluxation.

Non–Operative Management

Non-operative management is often successful in diminishing symptoms in individuals with mild symptoms of ulnar nerve compression, namely intermittent paresthesias without motor complaints or atrophy. Studies suggest that nearly 90% of these patients have resolution or a significant decrease in symptoms after a trial of conservative treatment. The crux of this treatment is the protection of the ulnar nerve by maintaining the arm in relative extension and decreasing direct pressure on the nerve.

Night splinting is a helpful modality to prevent elbow hyperflexion during sleep. Activity modification that diminishes arm flexion is an effective tactic: patients who report prolonged talking on the phone, computer usage, or resting elbows on hard surfaces can be advised to modify the way they carry out these activities. For instance, a headset or speakerphone can be used instead of holding a phone up to one’s ear and elbow pads can lessen the pressure on the elbow when typing.

NSAIDS are a useful therapy to help diminish inflammation of the cubital tunnel, but do not typically work well in managing nerve pain.

Physical therapy is also a helpful modality with nerve mobilization and stretching techniques offering many patients symptom relief.

Indications for Surgery

Any patient with progressive neurologic symptoms involving their ulnar nerve should be indicated for surgery. Most commonly this will present as intermittent tingling that progresses to persistent numbness in the small and ring finger. Patients that present with objective motor weakness and/or atrophy should also be indicated for surgery. Intolerable pain stemming from ulnar nerve compression is also an indication for an operative intervention. The earlier in the disease course surgical intervention is introduced, the better and more predictable the outcome will be. We obtain EMG/NCS on all our preoperative patients but do not require a positive electrical diagnostic finding in order to indicate for surgery.

Surgical Technique

Submuscular Ulnar Nerve Transposition and Z-Lengthening of the Flexor-Pronator Mass

A cubital tunnel release is an out-patient surgical procedure that is typically performed under a regional block. Preoperative IV antibiotics are given and the patient is positioned supine utilizing a hand table. A sterile tourniquet is applied to ensure appropriate access to the proximal regions of the cubital tunnel. A bump is placed under the elbow and the shoulder is maximally externally rotated to best position the elbow for a medial approach. A 5-6 cm incision is made based over the medial epicondyle. Optimally we like to start the proximal part of the incision over the intramuscular septum and angle towards the inferior portion of the medial epicondyle and down towards the ulna. There is a wide variety of the depth of the adipose layer that one will encounter dependent on the body habitus of the patient. There may be a number of venous structures that need to be cauterized during this part of the approach. The medial antebrachial cutaneous (MABC) nerve needs to be identified and protected as you approach the medial epicondyle (Figure 1). It typically will lie close to the fascia of the flexor-pronator mass in a fat layer just superficial to it. It runs obliquely over the flexor-pronator mass and typically has no branches proximal to it. By keeping our incision slightly more posterior we can sometimes keep the MABC and its branches in the anterior skin flap.

Figure 1.

The medial epicondyle is identified and the intramuscular septum as it extends proximally is exposed. The ulnar nerve can easily be identified posterior to the intramuscular septum. The nerve is exposed at this point and a vessel loop is applied around the nerve. We next release the nerve 6 cm proximal to the medial epicondyle and isolate and excise the intramuscular septum (Figure 2, Figure 3). Care must be taken at this point not to injure the deep penetrating vessels which lie adjacent to the septum. We attempt to leave as much of the vasovasorum with the nerve as possible as we mobilize it. Next, the fascia over the cubital tunnel is released and the flexor carpi ulnaris (FCU) fascia is exposed. The FCU fascia is released and deep component to the fascia must also be identified and released. This deep fascia can be found once the FCU muscle fibers are spread off the ulnar nerve approximately 0.5 cm distal to the medial epicondyle. The nerve is released distally until the first motor branch of the FCU is identified (Figure 4).

Figure 2.

Figure 3.

Figure 4.

The flexor-pronator mass (FPM) is identified and a Z-shaped cut is made through the fascia and muscle fibers. A vertical septum within the FPM is always encountered and must be excised. Care must be taken not to cut into the fibers of the ulnar collateral ligament (UCL) at the most posterior aspect of the FPM. The nerve is then transposed to its new more anterior position (Figure 5). The FPM fascia is then approximated in a Z-lengthened fashion with 3-0 PDS suture and clamped, not tied. The elbow is taken through its full ROM while observing the path of the nerve.

Figure 5.

One must ensure that there is no kinking of the nerve at any points along its new path. At this point the tourniquet is deflated and hemostasis is obtained. We next place the flat handle of a forceps over the nerve and then tie our 3-0 PDS figure of eight sutures, repairing the FPM. The elbow is once again taken through its full ROM while observing the nerve’s path. The skin is then closed with 4-0 nylon sutures and the elbow is placed in a well-padded posterior splint at 90 degrees of flexion.

Pearls and Pitfalls of Technique

• First identify the nerve proximal to the medial epicondyle and excise the intramuscular septum

• Preserve the vasovasorum around the nerve when mobilizing it to maintain its blood supply

• Identify and protect the medial antebrachial cutaneous nerve

• Excise the vertical septum of the flexor-pronator mass when performing the Z-plasty

• Decompress the deep fascia of the FCU muscle

• Scrutinize the path of the nerve in its new submuscular position by ranging the elbow and ensuring no new constriction points or kinks are created.

Potential Complications

Damage to the posterior branch of the medial antebrachial cutaneous nerve is a relatively common complication after ulnar nerve surgery. This nerve branch is encountered in most surgical approaches to the ulnar nerve, and consequently neuroma, hyperalgesia of the region, or a painful scar are possible. Recurrent symptoms after surgical treatment can occur if there has been incomplete decompression of the nerve anywhere along its course. Operative site infection and hematoma may also occur.

Post–operative Rehabilitation

Postoperatively, the elbow is immobilized for 7-10 days at 90 degrees of flexion in a well-padded posterior splint. At the first post-op visit the splint is removed and patients are sent to OT for a compression sleeve and hand, forearm, and elbow ROM. At 6 weeks post-op a supervised strengthening program is initiated. At 3 months post-op patients can resume full activity.

Outcomes/Evidence in the Literature

Adelaar, Robert S., Foster, William C., Charles, McDowell. “The treatment of the cubital tunnel syndrome”. The Journal of hand surgery. vol. 9.1. 1984. pp. 90-95. (An overview of cubital tunnel syndrome and its treatments.)

Ehsan, Amirhesam, Hanel, Douglas P. “Recurrent or Persistent Cubital Tunnel Syndrome”. The Journal of hand surgery. vol. 37.9. 2012. pp. 1910-1912. (An exploration of the causes of recurrent and persistent ulnar nerve symptoms.)

Goldfarb, Charles A.. “Incidence of re-operation and subjective outcome following in situ decompression of the ulnar nerve at the cubital tunnel”. Journal of Hand Surgery (European Volume). vol. 34.3. 2009. pp. 379-383. (A study finding a low failure rate of in situ decompression of the cubital tunnel.)

Hutchison, Richard L., Ghazi, Rayan. “Diagnosis of cubital tunnel syndrome”. The Journal of hand surgery. vol. 36.9. 2011. pp. 1519-1521. (This study recommends surgical treatment of cubital tunnel syndrome without obtaining electrodiagnostic studies.)

James, Jaison. “Morphology of the cubital tunnel: an anatomical and biomechanical study with implications for treatment of ulnar nerve compression”. The Journal of hand surgery. vol. 36.12. 2011. pp. 1988-1995. (An exploration of the changes occurring in the cubital tunnel and ulnar nerve with varying degrees of flexion.)

Mirza, Ather. “Scope-assisted release of the cubital tunnel”. The Journal of hand surgery. vol. 36.1. 2011. pp. 147-151. (An overview of endoscopic release of the cubital tunnel, finding it a useful treatment to cure symptoms while diminishing the risk of iatrogenic trauma to the nerve and its vasculature.)

Novak, Christine B.. “Provocative testing for cubital tunnel syndrome”. The Journal of hand surgery. vol. 19.5. 1994. pp. 817-820. (An exploration of provocative testing which found that the combined elbow flexion-direct pressure test was the most sensitive for detecting cubital tunnel syndrome.)

Palmer, Bradley A., Hughes, Thomas B. “Cubital tunnel syndrome”. The Journal of hand surgery. vol. 35.1. 2010. pp. 153-163. (An overview of cubital tunnel syndrome and its treatment.)

Soltani, Ali M.. “Trends in the Surgical Treatment of Cubital Tunnel Syndrome: An Analysis of the NSAS Database”. Plastic and Reconstructive Surgery. vol. 132.4S-1. 2013. pp. 83(A paper helpful for understanding trends in treatment of cubital tunnel syndrome, namely the increasing number of in situ decompressions performed relative to transpositions.)

Spinner, Robert J., Goldner, Richard D. “Snapping of the Medial Head of the Triceps and Recurrent Dislocation of the Ulnar Nerve. Anatomical and Dynamic Factors*†”. The Journal of Bone & Joint Surgery. vol. 80.2. 1998. pp. 239-47. (An exploration of a common elbow disorder that factors highly in the differential diagnosis of cubital tunnel syndrome.)

Stutz, Christopher M.. “Surgical and Nonsurgical Treatment of Cubital Tunnel Syndrome in Pediatric and Adolescent Patients”. The Journal of hand surgery. vol. 37.4. 2012. pp. 657-662. (This study recommends a trial of conservative treatment for pediatric and adolescent patients with cubital tunnel syndrome despite its low efficacy and the frequency of the patient proceeding to surgery.)

Tomaino, Matthew M., Brach, Paul J., Vansickle, David P. “The rationale for and efficacy of surgical intervention for electrodiagnostic-negative cubital tunnel syndrome”. The Journal of hand surgery. vol. 26.6. 2001. pp. 1077-1081. (A study encouraging surgical treatment for patients with mild cubital tunnel symptoms despite negative electrodiagnostic studies in order to maximally improve treatment efficacy by addressing the pathology as early as possible.)

vanRijn, Rogier M.. “Associations between work-related factors and specific disorders at the elbow: a systematic literature review”. Rheumatology. vol. 48.5. 2009. pp. 528-536. (An overview of elbow disorders which yielded the estimated incidence of cubital tunnel syndrome.)

Zimmerman, Ryan M., Jupiter, Jesse B., Juan, González del Pino. “Minimum 6-Year Follow-Up After Ulnar Nerve Decompression and Submuscular Transposition for Primary Entrapment”. The Journal of hand surgery. vol. 38.12. 2013. pp. 2398-2404. (A study demonstrating the long term efficacy of submuscular transposition for cubital tunnel syndrome.)

Summary

Cubital tunnel syndrome is a common compressive neuropathy that occurs due to entrapment of the ulnar nerve near the elbow. Patients typically present with paresthesias/numbness of the small and ring digits with or without hand weakness; more advanced cases demonstrate muscular atrophy and hand contractures. Diagnosis of cubital tunnel syndrome is predominantly clinical, but there are various diagnostic modalities that may provide the clinician a better understanding of the patient’s pathology. This neuropathy may be successfully treated by both conservative and operative means.

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