Pollock Sign

Pollock Sign is a specialized clinical test used to evaluate the integrity of the flexor digitorum profundus (FDP) muscle of the little finger following suspected ulnar nerve injury. This test is particularly valuable in differentiating between complete and incomplete ulnar nerve lesions, as it assesses the function of the deep branch of the ulnar nerve.

The flexor digitorum profundus muscle has dual innervation:

• The medial portion (serving the ring and little fingers) is innervated by the ulnar nerve
• The lateral portion (serving the index and middle fingers) is innervated by the median nerve

In ulnar nerve injuries, the FDP function to the little finger is compromised while the index and middle finger FDP function remains intact due to median nerve innervation.

See Also: Flexor Digitorum Profundus Muscle Anatomy

How to Perform the Pollock Sign?

The patient sits comfortably with both hands accessible to the examiner. The examiner instructs the patient to flex the little fingers of both hands at the distal interphalangeal (DIP) joints, creating a “hook” configuration. The patient interlocks these hooked little fingers.

The patient is asked to pull the fingers apart while maintaining flexion at the DIP joints, the examiner then observes the ability to maintain DIP flexion during the pulling motion.

See Also: Ulnar Nerve Anatomy

What is the Positive Pollock Sign?

Normally, the patient can maintain DIP flexion of the little finger while pulling against resistance, indicating intact FDP function.

The Pollock Sign is positive when:

• The distal phalanx of the affected little finger extends during the pulling motion
• May be accompanied by extension of the middle phalanx
• Indicates weakness or paralysis of the FDP muscle due to ulnar nerve dysfunction

A positive Pollock Sign suggests:

• Deep branch ulnar nerve involvement
• More proximal ulnar nerve lesion (as opposed to superficial branch only)
• Potential for significant functional impairment in grip strength and fine motor control

The test helps distinguish between:

• High ulnar nerve lesions (affecting both motor and sensory functions)
• Low ulnar nerve lesions (primarily affecting intrinsic hand muscles)
• Isolated deep branch injuries

Limitations and Considerations

• The test requires patient cooperation and understanding of instructions
• Pain or joint stiffness may affect test reliability
• Should be interpreted alongside other clinical findings and nerve conduction studies
• False negatives may occur in partial nerve injuries

Pollock Sign should be performed as part of a comprehensive ulnar nerve assessment, including:

• Wartenberg sign (small finger abduction)
• Froment sign (thumb adduction weakness)
• Sensory testing in ulnar nerve distribution
• Assessment of intrinsic hand muscle function

References & More

1. Goloborod’ko SA. New clinical motor test for cubital tunnel syndrome. J Hand Ther. 2012;25(4):422–424. PubMed
2. Orthopedic Physical Assessment by David J. Magee, 7th Edition.