Froment's sign

Froment's sign is a clinical test used to evaluate for the presence of ulnar nerve dysfunction, specifically affecting the functionality of the adductor pollicis muscle in the hand. The ulnar nerve is one of the three main nerves traversing the arm, responsible for innervating various muscles in the forearm and hand, thus playing a crucial role in hand movements and sensations.

Etiology

Froment's sign is indicative of ulnar nerve palsy, which can result from various causes including, but not limited to, trauma, compression, or neuropathy. The ulnar nerve may be compressed at several points along its course, most commonly at the elbow (cubital tunnel syndrome) or the wrist (Guyon's canal syndrome).

Clinical Presentation

Patients with ulnar nerve dysfunction may present with weakness in the hand, difficulty in pinching objects between the thumb and index finger, and a loss of sensation in the ulnar aspect of the hand. Froment's sign specifically tests for the function of the adductor pollicis muscle, which is innervated by the ulnar nerve.

Procedure

To perform the test, the patient is asked to hold a piece of paper between the thumb and index finger. The examiner then attempts to pull the paper away. A positive Froment's sign is indicated by the patient's inability to hold the paper securely, leading to compensation by flexing the thumb's distal phalanx, a movement primarily facilitated by the flexor pollicis longus muscle, which is innervated by the median nerve. This compensatory action is often referred to as "Jeanne's sign" when accompanied by hyperextension of the thumb's metacarpophalangeal joint.

Interpretation

A positive Froment's sign suggests weakness or paralysis of the adductor pollicis muscle due to ulnar nerve dysfunction. However, it is important to note that the presence of Froment's sign alone does not determine the exact location or cause of the ulnar nerve pathology, necessitating further diagnostic investigations.

Differential Diagnosis

When assessing a patient with a positive Froment's sign, it is crucial to differentiate between ulnar nerve pathology and other conditions that may mimic similar symptoms, such as median nerve compression or cervical radiculopathy. Comprehensive clinical evaluation and diagnostic studies, including electromyography (EMG) and nerve conduction studies, can help in accurately diagnosing the underlying condition.

Management

Management of ulnar nerve dysfunction involves addressing the underlying cause. Conservative treatment options include splinting, non-steroidal anti-inflammatory drugs (NSAIDs), and physical therapy. In cases where conservative management fails or in the presence of significant nerve compression, surgical intervention may be necessary.

Conclusion

Froment's sign is a valuable clinical tool in the assessment of ulnar nerve dysfunction. Early recognition and appropriate management of the underlying cause are essential to prevent permanent disability and improve patient outcomes.