ICD-9 CODE 354.2
ICD-10 CODE G56.20
The Clinical Syndrome
The ulnar nerve is susceptible to compression when a driver or passenger rests his or her elbow on the lower sill of the vehicle window while the shoulder is abducted and the elbow flexed. When the elbow is flexed, the proximal edge of the arcuate ligament becomes taut and the total volume of the cubital tunnel is decreased, resulting in increased intratunnel pressure further compromising the ulnar nerve. Vibration transmitted from the car body to the elbow also may further contribute to compromise of the ulnar nerve. This entrapment neuropathy presents as pain and associated paresthesias in the lateral forearm that radiate to the wrist and ring and little finger. Untreated, progressive motor deficit and, ultimately, flexion contracture of the affected fingers can result.
Signs and Symptoms
Physical findings associated with driver’s elbow include tenderness over the ulnar nerve at the elbow. A positive Tinel’s sign over the ulnar nerve as it passes beneath the aponeuroses is usually present ( Figure 44-1 ). Weakness of the intrinsic muscles of the forearm and hand that are innervated by the ulnar nerve may be identified with careful manual muscle testing ( Table 44-1 ). It should be noted that the possibility always exists that a patient with driver’s elbow also may have an coexistent ulnar, median, or radial nerve lesion distal to the elbow that may confuse the clinical picture. Furthermore, it should be remembered that cervical radiculopathy and ulnar nerve entrapment may coexist as the “double crush” syndrome. The double crush syndrome is seen most commonly with median nerve entrapment at the wrist or with carpal tunnel syndrome. The clinician should be aware that early in the course of the evolution of driver’s elbow the only physical finding other than tenderness over the nerve may be the loss of sensation on the ulnar side of the little finger.
Tinel’s sign at elbow.
(From Waldman SD: Atlas of pain management injection techniques, 3rd ed, Philadelphia, 2013, Saunders, p 129.)
TABLE 44-1
Summary of Ulnar Nerve Motor Signs and Tests Grouped by Affected Musculature
| Test Name | Description | Positive Result |
|---|---|---|
| Motor signs involving the adductor pollicis muscle | ||
| Froment’s sign | The patient holds a piece of paper using a lateral pinch. The examiner then pulls the paper distally along the thumb’s longitudinal axis and assesses the patient’s method of stabilization. | Thumb IP flexion compensates for a weak adductor pollicis muscle. |
| Jeanne’s sign | The patient holds a piece of paper using a lateral pinch. The examiner then pulls the paper distally along the thumb’s longitudinal axis and assesses the patient’s method of stabilization. | Thumb MP hyperextension compensates for a weak adductor pollicis muscle. |
| Motor signs and tests involving the interosseous muscles | ||
| Finger flexion sign | Performed bilaterally at the same time. Both forearms and wrists are in neutral. Examiner first places a piece of paper between the middle and ring fingers in both hands and then pulls the paper distally. | The involved side will use MP flexion to compensate for interossei weakness. |
| Crossed finger test | Examiner asks the patient to cross the middle finger over the index finger. | Inability to cross the fingers. Compare with uninvolved side. |
| Egawa’s sign | Examiner then asks the patient to flex the middle finger MP joint and then to abduct it to both sides. This can be difficult to perform; therefore bilateral assessment is recommended. | Inability to perform this action in contrast to uninvolved side. |
| Motor signs involving the ulnar nerve–innervated lumbrical muscles | ||
| Duchenne’s sign | Sign is identified by observing the posture of the small and ring fingers on the involved side. | Clawing posture (MP hyperextension and IP flexion) present in the ring and small fingers. |
| André-Thomas sign | Sign is identified by observing the compensatory pattern used in the ring and small fingers during actions involving EDC use. | Wrist tends to flex with ring and small finger EDC activation. |
| Motor signs involving the hypothenar musculature | ||
| Wartenberg’s sign | Patient actively abducts the fingers with the forearm in pronation and the wrist in neutral. Observe the small finger’s ability to fully adduct. | Inability of the small finger to fully adduct and touch the ring finger. Compare with the uninvolved side. |
| Masse’s sign | Observe the metacarpal arch as compared with the uninvolved side. The convex nature of the ulnar aspect of the hand is altered by hypothenar atrophy. | Flattened metacarpal arch. |
| Pitres-Testut sign | Noted after the examiner asks the patient to shape the hand in the form of a cone. Although present in the literature, this sign is not commonly used in clinical practice settings. | Inability to shape the hand in the form of a cone. |
| Palmaris brevis sign | A rarely observed sign in lower ulnar nerve palsy in which the lesion selectively affects the deep branch. Determine the presence of this sign by observing and evaluating the palmaris brevis muscle in contrast to the uninvolved side. | The sparing of the palmaris brevis muscle in contrast to the uninvolved side. |
| Motor signs involving the extrinsic ulnar nerve–innervated muscles | ||
| Nail file sign | Patient attempts to make a hook fist. Examiner places an index finger along the volar surface of the patient’s small and ring fingers, leaving the DIPs free to contract. | Decreased small and ring finger FDP strength in contrast to the uninvolved side. |
DIP, Distal interphalangeal; EDC, extensor digitorum communis; FDP, flexor digitorum profundus; IP, interphalangeal; MP,metacarpophalangeal.
Modified from Goldman SB, Brininger TL, Schrader JW, Koceja DM: A review of clinical tests and signs for the assessment of ulnar neuropathy, J Hand Ther 22:209–220, 2009.
Testing
Driver’s elbow should be differentiated from cervical radiculopathy involving the C7 or C8 roots and golfer’s elbow. Electromyography helps distinguish cervical radiculopathy and driver’s elbow from golfer’s elbow. Ultrasound imaging of the elbow may be useful in assessing the status of the ulnar nerve and can provide important anatomic information when combined with the neurophysiological data obtained from electromyography. Plain radiographs and magnetic resonance imaging (MRI) are indicated in all patients with drivers elbow to rule out intrinsic pathological conditions of the elbow joint ( Figure 44-2 ). Based on the patient’s clinical presentation, additional testing, including complete blood count, uric acid level, sedimentation rate, and antinuclear antibody testing, may be indicated. The injection technique described in this chapter serves as both a diagnostic and therapeutic maneuver.
A, Axial T1-weighted magnetic resonance imaging (MRI) of a patient with symptoms of ulnar nerve compression. Soft tissue is seen within the region of the cubital tunnel (white arrow); it is isointense, with normal muscle and represents an accessory anconeus muscle. The ulnar nerve is not clearly visible. B, Compare this axial T1-weighted image of a normal elbow with high signal intensity fat suppression (FS) within the cubital tunnel around the ulnar nerve (broken black arrow) and no accessory muscle tissue. The axial (C) and sagittal FS T2-weighted MRI demonstrate high signal intensity within the nerve (white arrows)resulting from compression neuritis. LE, Lateral epicondyle; ME, medial epicondyle; O, olecranon.
(From Waldman SD, Campbell RSD, editors: Imaging of pain, Philadelphia, 2011, Saunders, p 290.)
Differential Diagnosis
Driver’s elbow is an entrapment neuropathy resulting from external compression of the ulnar nerve that clinically mimics cubital tunnel syndrome. It is often is misdiagnosed as golfer’s elbow, which accounts for the many patients with “golfer’s elbow” who fail to respond to conservative measures. Driver’s elbow can be distinguished from golfer’s elbow in that in driver’s elbow, the maximal tenderness to palpation is over the ulnar nerve 1 inch below the medial epicondyle, whereas with golfer’s elbow, the maximal tenderness to palpation is directly over the medial epicondyle.
Treatment
Initial treatment of the pain and functional disability associated with driver’s elbow should include a combination of nonsteroidal anti-inflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and physical therapy. Local application of heat and cold also may be beneficial. The repetitive movements that incite the syndrome should be avoided. For patients who do not respond to these treatment modalities, injection of the ulnar nerve at the elbow with a local anesthetic and steroid may be a reasonable next step. If the symptoms of cubital tunnel syndrome persist, surgical exploration and decompression of the ulnar nerve are indicated.
Complications and Pitfalls
The major complications associated with the diagnosis and treatment of patients with driver’s elbow fall into two categories: (1) iatrogenically induced complications resulting from persistent and overaggressive treatment of “resistant golfer’s elbow” and (2) the potential for permanent neurological deficits as a result of prolonged untreated entrapment of the ulnar nerve. Failure of the clinician to recognize acute inflammatory or infectious arthritis of the elbow may result in permanent damage to the joint, chronic pain, or functional disability.
CLINICAL PEARLS
Driver’s elbow is a distinct clinical entity often misdiagnosed as golfer’s elbow, which accounts for the many patients with “golfer’s elbow” who fail to respond to conservative measures. Driver’s elbow can be distinguished from golfer’s elbow because, with cubital tunnel syndrome, the maximal tenderness to palpation is over the ulnar nerve and a positive Tinel’s sign is present, whereas with golfer’s elbow, the maximal tenderness to palpation is over the medial epicondyle. Driver’s elbow also should be differentiated from cervical radiculopathy involving the C8 spinal root, which may at times mimic ulnar nerve compression. Furthermore, it should be remembered that cervical radiculopathy and ulnar nerve entrapment may coexist in double crush syndrome. The double crush syndrome is seen most commonly with median nerve entrapment at the wrist or with carpal tunnel syndrome. Pancoast’s tumor invading the medial cord of the brachial plexus may also mimic an isolated ulnar nerve entrapment and should be ruled out by apical lordotic chest radiograph.
Careful neurological examination to identify preexisting neurological deficits that may later be attributed to the nerve block should be performed on all patients before beginning ulnar nerve block at the elbow.
Ulnar nerve entrapment at the elbow is often misdiagnosed as golfer’s elbow, and this fact accounts for the many patients whose “golfer’s elbow” fails to respond to conservative measures. Driver’s elbow can be distinguished from golfer’s elbow in that in driver’s elbow, the maximal tenderness to palpation is over the ulnar nerve 1 inch below the medial epicondyle, whereas with golfer’s elbow, the maximal tenderness to palpation is directly over the medial epicondyle. If cubital tunnel syndrome is suspected, injection of the ulnar nerve at the elbow with local anesthetic and steroid gives almost instantaneous relief.
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