First Dorsal Interosseous Muscle Exam
To examine the first dorsal interosseous muscle, place the patient's forearm on a table in neutral rotation with the wrist in slight dorsiflexion. Have patient point the index finger straight towards the examiner. The examiner then applies an abduction/flexion force to the index finger distal to the MP joint while the patient resists. Normal resistance requires a functioning first dorsal interosseous. While applying the pressure to the index finger, the examiner uses their opposite index finger to palpate the first dorsal interosseous and assess its muscular contraction. See the photo below.
Diagrams & Photos
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First Dorsal Interosseous exam. -
Positive Froment's sign. Note the atrophy of the first dorsal interosseous (arrow).
Key Points
- First Dorsal Interosseous is the last muscle innervated by the ulnar nerve.
- The first dorsal interosseous provides significant force to key pinch.
- First dorsal interosseous and adductor pollicis muscle paralysis causes a positive Froment's sign.