Evaluation and Treatment of Ulnar Neuropathy at the Elbow



Evaluation and Treatment of Ulnar Neuropathy at the Elbow


Michael Darowish, MD

Kathleen Beaulieu, OTR/L, CHT


Dr. Darowish or an immediate family member serves as a board member, owner, officer, or committee member of the American Academy of Orthopaedic Surgeons. Neither Mrs. Beaulieu nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article.



Introduction

Cubital tunnel syndrome is the second most common compressive neuropathy of the upper extremity. Symptoms of cubital tunnel syndrome include numbness or tingling in the ring and small fingers, medial elbow pain, hand or grip weakness, dropping objects, or a generalized feeling of clumsiness of the hand. Numbness often occurs at night, waking patients from sleep, or is present upon awakening. Prolonged elbow flexion, as can occur when performing activities around one’s face or head, talking on the telephone, or keyboard use, as well as repetitive elbow flexion and extension, can increase symptoms. External compression to the nerve, such as leaning one’s elbow on a hard surface while driving, working on a table, or sitting on a chair with arms, can also increase numbness and pain in the hand.

Ulnar nerve compression from pressure and/or tension decreases blood flow to the ulnar nerve, resulting in demyelination. More severe nerve dysfunction eventually causes myopathic changes of the ulnar innervated muscles. The clinical manifestations of cubital tunnel syndrome are the result of nerve conduction abnormality as the ulnar nerve passes behind the medial epicondyle of the elbow. Nerve conduction can be affected by compression or traction across the ulnar nerve. Various anatomic structures, including the Arcade of Struthers (a fascial band from the medial triceps to the medial intramuscular septum), anconeus epitrochlearis muscle, Osborne’s ligament, and the deep or superficial flexor carpi ulnaris fascia can cause compression. Space occupying lesions within the cubital tunnel, including ganglia, osteophytes, or loose bodies, are less common causes of increased pressure on the ulnar nerve. Last, external compression of the nerve, such as that which is caused by leaning on one’s elbow, or positional factors, including prolonged elbow flexion, and ulnar nerve subluxation can cause symptoms.

In many cases, surgical treatment with ulnar nerve decompression with or without ulnar nerve transposition is required to relieve symptoms, as well as to prevent further neurologic deterioration. The postoperative treatment includes rehabilitation to ensure optimal recovery.


Relevant Anatomy

The ulnar nerve is the terminal branch of the medial cord of the brachial plexus, with contributions from the C8 and T1 cervical nerve roots. It traverses the thoracic inlet and outlet, entering the axilla. Proximally, the medial cord or ulnar nerve can be compressed by masses of the superior lung (Pancoast tumor), or at the thoracic outlet; these should be considered in the differential diagnosis. The nerve then pierces through the medial intermuscular septum, entering the posterior compartment at the level of the Arcade of Struthers, a band of fascia running from the medial intermuscular septum to the medial head of the triceps. The ulnar nerve then continues distally along the intermuscular septum, under the medial head of the triceps. At the elbow, the nerve lies in the condylar groove, then passes through the cubital tunnel, under the Osborne ligament. The nerve then enters the flexor carpi ulnaris (FCU), where it is covered both by the superficial fascia of the FCU as well as a deeper layer of fascia under the muscle fibers of the FCU. The ulnar nerve then begins branching, providing muscular branches to the FCU and the ulnar portion of the flexor digitorum profundus (FDP). The nerve continues distally, travelling deep and radial to the FCU tendon, entering the wrist. It then enters the hand at the Guyon canal, dividing into the superficial sensory branches (which provide sensation to the small finger and the ulnar ring finger) and the deep motor branch, which wraps around the hook of the hamate and traverses the palm, providing motor innervation to the hypothenar musculature, the interosseous muscles, the deep head of the flexor pollicis brevis, and the ulnar two lumbrical muscles.

At the level of the elbow, the ulnar nerve can be compressed by the Arcade of Struthers, the overlying triceps, the Osborne ligament, and the FCU. When the nerve is transposed, the medial intermuscular septum can become a compressive structure as the nerve travels from the posterior compartment
into the anterior compartment. Further, iatrogenic compression or kinking can occur as the nerve reenters the FCU distally (Figure 18.1).






Figure 18.1 Illustration of the course of the ulnar nerve at the elbow, with potential compressive structures. (Reproduced from Elhassan B, Steinmann SP: Entrapment neuropathy of the ulnar nerve. J Am Acad Orthop Surg, 2007;15:674. Reproduced with permission from the Mayo Foundation for Medical Education and Research, Rochester, MN.)


Evaluation

Evaluation of the patient begins with a thorough history. Patients describe numbness and pain in their hand. Encouraging the patient to localize the numbness to specific digits can be challenging, but immensely helpful. Similarly, isolating activities or arm positions that exacerbate symptoms can help to differentiate the various causes of numbness. Classically, activities in which the elbow is flexed, such as driving, talking on a telephone, texting, reading a newspaper, tasks around the face and head, or sleeping exacerbate symptoms. Similarly, repetitive elbow flexion and extension, or leaning on the elbow, will worsen the patient’s pain or numbness. The presence or absence of associated medical conditions such as diabetes, peripheral neuropathy, rheumatoid arthritis, renal disease, or a history of fracture or trauma to the elbow can also help in narrowing the diagnosis.

Physical examination begins with evaluation of the elbow range of motion (ROM), looking for limitations in flexion and extension that may indicate underlying arthritis. The carrying angle of the elbow is observed to identify cubitus valgus, which can increase tension on the ulnar nerve. Any swelling or edema, particularly at the medial elbow, should also be noted. The hand should be evaluated for the presence of atrophy of the ulnar nerve innervated musculature, including the hypothenar mass and the first dorsal interosseous muscle. In severe cases, the ulnar two digits may be in a clawed position—metacarpophalangeal (MCP) hyperextension, proximal interphalangeal (PIP) and distal interphalangeal (DIP) flexion (Figure 18.2, A and B).

Ulnar motor function is assessed with finger abduction and adduction, as well as checking if the patient can cross the index and long fingers. This is a more reliable test, and the examiner is less easily “faked out” by finger extension. Additionally, we have found that finger crossing can be significantly “clumsier” than the unaffected side, even before frank atrophy is noted. The FDP to the ring and small fingers may be affected, resulting in an incomplete fist or weakened grip. Key pinch is often affected in ulnar neuropathy, resulting in the Froment sign. When asked to pinch a piece of paper, the patient with ulnar neuropathy replaces key pinch with tip pinch, flexing the interphalangeal (IP) joint of the thumb. In doing so, the patient utilizes the median nerve innervated flexor pollicis longus (FPL) in lieu of the ulnar innervated adductor pollicis (Figure 18.3, A and B). Strength can be objectively evaluated for grip, using a Jamar dynamometer, and for pinch, including tip, key, and 3-jaw chuck.

Sensation in the ulnar nerve distribution should be evaluated. The pulp of the small finger is predictably innervated by the ulnar nerve, thus should be used for testing. Additionally, the dorsal ulnar hand is innervated by the dorsal cutaneous branch of the ulnar nerve, which branches several centimeters proximal to the wrist. Diminished sensation in the dorsal hand suggests a more proximal lesion, and can help to differentiate ulnar nerve compression at the cubital tunnel from compression at the Guyon canal. Various methods—including light touch, Semmes-Weinstein monofilament, and two-point discrimination—can be utilized. Two-point discrimination is not affected until much later in the disease, while Semmes-Weinstein monofilament testing can be helpful earlier in the course.

In many cases of cubital tunnel syndrome, symptoms are not present unless provoked. Because it is a dynamic process, and can be position and pressure dependent, many patients demonstrate intact motor and sensation on initial testing. To bring about ulnar nerve symptoms, various provocative maneuvers can be performed. A Tinel sign is reproduction of electric shocks or numbness and tingling in the ulnar nerve distribution with percussion over the nerve, either at the cubital tunnel (Figure 18.4) or at the Guyon canal. Note that the Tinel sign can be positive in at least 10% of unaffected individuals. In the elbow compression–flexion test, the examiner places pressure over the ulnar nerve at the cubital tunnel while holding the elbow flexed and the wrist in neutral position to prevent creating secondary pressure at the carpal tunnel or Guyon
canal, which can also cause hand numbness (Figure 18.5). The examiner should also assess for more proximal nerve lesions, including cervical spine and lower brachial plexus lesions that can mimic ulnar neuropathy.






Figure 18.2 A, Photograph of the typical ulnar clawing posture of the ring and small fingers, with hyperextension of the metacarpophalangeal joints and flexion of the proximal interphalangeal and distal interphalangeal joints. B, Photograph of atrophy of the first dorsal interosseous muscle can be seen along with this clawing (patient’s right hand).






Figure 18.3 Photographs of Froment’s sign. The patient is asked to pinch the paper while the examiner tries to pull the paper away. A, The patient’s left hand shows the normal posture of key pinch. B, The patient’s right hand shows replacement of key pinch with tip pinch, using the flexor pollicis longus (median innervated) rather than the adductor pollicis and first dorsal interosseous (ulnar innervated).

Electrodiagnostic evaluation with electromyography (EMG) and nerve conduction study (NCS) can be used in the evaluation of cubital tunnel syndrome. EMG/NCS testing is often normal because of the dynamic nature of cubital tunnel syndrome, and positive EMG/NCS findings are often only present later in the course of the disease, or in more severe cases. EMG/NCS can be helpful in challenging cases, to help differentiate cervical pathology from peripheral nerve compression, or to help differentiate proximal and distal lesions. We often obtain nerve testing preoperatively to have a baseline study in case
postoperative symptoms persist, as well as to temper patient expectations in more severe cases. Radiographs or MRI are not a routine part of evaluation of cubital tunnel syndrome; they are reserved only for cases in which there is concern for concomitant arthritis, space-occupying lesions, or a history of previous trauma to the elbow that may be contributing to compression of the nerve.






Figure 18.4 Photograph of a Tinel sign, produced by tapping over the ulnar nerve at the cubital tunnel. A positive Tinel sign produces pain or paresthesia into the ring and small fingers.




Treatment

The primary goals of conservative treatment are to reduce pain, diminish paresthesias or hypersensitivity, improve or compensate for ROM limitations, diminish neural tension, maximize strength, and improve or restore function. In most cases, activity modification can play a major role in resolving the symptoms. Nonoperative treatment is often effective in cases with mild, intermittent symptoms and no weakness or atrophy, with up to 50% of patients with mild cubital tunnel syndrome achieving successful outcomes. However, it is important to note that nonoperative treatment has not been shown to improve strength.






Figure 18.5 Photograph of the elbow compression-flexion test, which is performed by keeping the patient’s elbow flexed while keeping the wrist in neutral position. Pressure is placed over the ulnar nerve at the cubital tunnel. A positive test produces numbness, pain, or paresthesia in the ulnar nerve distribution.

Patient education is a large part of treatment. Explaining the relevant anatomy and showing the patient the course of the ulnar nerve allows for an improved understanding of how certain movements or activities may affect the nerve. It reinforces how activity modifications or ergonomic changes may assist in diminishing symptoms and can have a positive impact on outcome. This tends to improve patient compliance with the treatment program.

Modalities may be used in conjunction with treatment techniques. Moist heat can be used for pain relief, as well as soft-tissue preparation prior to exercise or functional activity. Ice can be applied to the symptomatic area to assist in edema and pain reduction. Ultrasound may be utilized to increase blood flow to the area. Specific care should be taken to avoid thermal injury. Close monitoring is advised if applying thermal modalities to an area with altered sensation.

Myofascial mobility may be increased through the use of myofascial release techniques, slow steady stretch, or the use of Kinesio tape, decreasing the tension of the ulnar nerve during functional activities. Neural mobilization techniques can be useful in symptom reduction; care should be taken to not place tension on the nerve. Nerve gliding or flossing techniques are a preferred method to provide neural mobility with limited tension. The use of myofascial release, Kinesio taping, and neural mobilization require an extensive understanding of the evaluation and treatment process beyond the scope of this chapter.

Strengthening proximal muscle groups may be beneficial in those patients who must perform tasks requiring resisted or sustained elbow flexion. Increasing shoulder strength, scapular stabilization, and improving posture allow the stress of lifting to be transferred to more proximal muscle groups, decreasing stresses across more distal affected muscle groups.

Rest from aggravating positions and activities may be quite beneficial. The therapist should evaluate the patient’s daily activities—including self-care, work, and leisure pursuits—to identify and target potential areas for modification. Specific areas to focus on include avoidance of compression, avoidance of traction, decreasing overuse of the wrist flexor and pronator muscles, and altering approaches to specific tasks that cause symptoms. On-site assessment of the patient’s workplace can be of great benefit. The physical set-up and job requirements are reviewed, and suggestions may be made regarding ergonomic adjustments, environmental alterations, and workflow.

A soft pad worn over the elbow assists in cushioning the cubital tunnel so that increased external pressure or unintentional trauma to the ulnar nerve is avoided during functional use of the involved extremity (Figure 18.6, A and B).







Figure 18.6 A, Photograph of a Heelbo, a low-profile elbow pad, which can provide significant relief from external compression of the ulnar nerve (B).

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Oct 13, 2018 | Posted by in ORTHOPEDIC | Comments Off on Evaluation and Treatment of Ulnar Neuropathy at the Elbow

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