Abductor pollicis brevis muscle

1121 Intrinsic Muscles of the Hand Superficial sin

Abductor Pollicis Brevis is a muscle of the hand that plays a crucial role in the movement of the thumb. It is one of the thenar muscles, located on the radial side of the hand, and is primarily involved in the abduction of the thumb away from the palm. This action is essential for the thumb's gripping and manipulative functions, making the Abductor Pollicis Brevis vital for many daily activities.

Anatomy

The Abductor Pollicis Brevis originates from the flexor retinaculum and the tubercles of the scaphoid and trapezium bones in the wrist. It inserts into the lateral base of the proximal phalanx of the thumb and the extensor pollicis brevis's aponeurosis. The muscle is innervated by the median nerve, specifically through its recurrent branch, which is crucial for the muscle's motor function. Its blood supply comes from the radial artery.

Function

The primary function of the Abductor Pollicis Brevis is the abduction of the thumb at the carpometacarpal joint. This movement is essential for creating a gap between the thumb and the rest of the hand, allowing for a wide range of thumb movements and positions. This muscle also assists in the opposition and extension of the thumb, contributing to the thumb's versatility and its ability to perform precise and powerful grips.

Clinical Significance

The Abductor Pollicis Brevis muscle can be involved in several medical conditions. One common condition is De Quervain's Tenosynovitis, which affects the tendons on the thumb side of the wrist and can cause pain and swelling in the area of this muscle. Additionally, the muscle's function can be compromised in cases of median nerve injury or compression, as seen in Carpal Tunnel Syndrome, leading to weakness or difficulty in thumb abduction.

Assessment

The function of the Abductor Pollicis Brevis can be assessed through various clinical tests, often focusing on the strength and range of motion of the thumb. One common test is asking the patient to lift their thumb away from the palm against resistance, evaluating the muscle's strength and the integrity of its nerve supply.

Rehabilitation

Rehabilitation exercises targeting the Abductor Pollicis Brevis are often prescribed following injury or surgery affecting the hand or thumb. These exercises may include thumb abduction movements against resistance to strengthen the muscle and improve thumb function.