What is Froment's Test?
Froment's test, also known as Froment's sign, is a physical examination technique used to assess the function of the adductor pollicis muscle and identify ulnar nerve palsy. It specifically checks for weakness or paralysis in this muscle, which is responsible for adducting (pulling towards the center) the thumb.
The test is simple:
- The patient is asked to pinch a piece of paper (or a similar thin object) between their thumb and index finger.
- The examiner applies resistance to the pinch.
- A positive Froment's sign is indicated if the patient flexes the interphalangeal (IP) joint of their thumb (the joint closest to the fingernail) to compensate for the weakness of the adductor pollicis. A healthy adductor pollicis allows the patient to maintain a strong pinch without flexing this joint.
What Froment's Test Indicates
A positive Froment's sign suggests weakness or paralysis of the adductor pollicis muscle, often due to ulnar nerve damage or injury. The ulnar nerve innervates this muscle, so its dysfunction points to a problem with the nerve.
- Ulnar Nerve Palsy: This is the most common reason for a positive Froment's sign. Ulnar nerve palsy can result from trauma, compression, or other neurological conditions.
- Other Conditions: While less common, other conditions affecting the hand muscles can also lead to a positive test.
It's important to note that Froment's test is only one part of a comprehensive neurological examination. Other tests and clinical findings are necessary for a proper diagnosis.
Examples of Froment's Test Application
- A patient presents with weakness in their hand and difficulty with fine motor tasks. A positive Froment's test helps the clinician suspect ulnar nerve involvement.
- Following a forearm injury, a positive Froment's test aids in assessing the extent of nerve damage.
While variations in technique and interpretation may exist, the core principle of assessing adductor pollicis function through resisted thumb adduction remains central to Froment's test.
