Froment sign

Clinical sign of ulnar nerve dysfunction

Froment's sign is a clinical test used to assess the function of the ulnar nerve, particularly its innervation to the adductor pollicis muscle. This sign is often used in the diagnosis of ulnar nerve palsy and can indicate weakness or dysfunction in the muscles innervated by the ulnar nerve.

Clinical Presentation

Froment's sign is elicited by asking the patient to hold a piece of paper between the thumb and index finger, using a lateral pinch grip. The examiner then attempts to pull the paper away. In a positive Froment's sign, the patient compensates for weakness of the adductor pollicis by flexing the interphalangeal joint of the thumb, using the flexor pollicis longus muscle, which is innervated by the median nerve. This compensatory action indicates weakness in the ulnar nerve-innervated muscles.

Froment's sign being demonstrated

Pathophysiology

The ulnar nerve is responsible for innervating several muscles in the hand, including the adductor pollicis, which is crucial for the adduction of the thumb. When the ulnar nerve is compromised, as in cases of cubital tunnel syndrome or ulnar nerve entrapment, the adductor pollicis may become weak or paralyzed. As a result, the patient may rely on the flexor pollicis longus, a muscle innervated by the median nerve, to maintain grip strength, leading to the characteristic thumb flexion seen in Froment's sign.

Clinical Significance

Froment's sign is a valuable diagnostic tool for clinicians assessing patients with suspected ulnar nerve dysfunction. It helps differentiate between ulnar nerve palsy and other conditions affecting hand function. A positive Froment's sign suggests ulnar nerve involvement, which may require further investigation and management, such as nerve conduction studies or imaging.

Related Tests

In addition to Froment's sign, other tests can be used to evaluate ulnar nerve function, including:

• Tinel's sign
• Phalen's test
• Wartenberg's sign

Management

Management of a positive Froment's sign involves addressing the underlying cause of ulnar nerve dysfunction. Treatment options may include:

• Conservative measures such as splinting and physical therapy
• Surgical intervention in cases of severe nerve compression or entrapment

Related Pages

• Ulnar nerve
• Cubital tunnel syndrome
• Ulnar nerve entrapment
• Adductor pollicis