The Abductor Pollicis Brevis (APB) is a thenar muscle located within the hand. It forms the anterolateral aspect of the thenar eminence, overlaying the opponens pollicis muscle.
The APB originates from the tubercles of the scaphoid and trapezium bones, as well as from the associated flexor retinaculum.
Attaching to the lateral aspect of the proximal phalanx of the thumb, the primary action of the APB is abduction of the thumb.
The APB is primarily innervated by the Median Nerve (recurrent branch). Its main blood supply comes from the Superficial Palmar Arch.
The Abductor Pollicis Brevis is a thenar muscle located within the hand. It forms the anterolateral aspect of the thenar eminence, overlaying the opponens pollicis muscle and originating from three sources:
The APB attaches to the lateral aspect of the proximal phalanx of the thumb.
The primary action of the APB is to abduct the thumb - that is to move it away from the palm of the hand.
The Abductor Pollicis Brevis is primarily innervated by the Median Nerve (recurrent branch).
The primary source of blood supply for the APB is the Superficial Palmar Arch.
The Abductor Pollicis Brevis is the most medial thenar muscle; any damage to it can affect the hand and wrist’s motor function and proprioception. Because of its location and intimate relationship with the other thenar muscles, it can affect the proper performance of the hand’s grasping and pinch movements.
In addition, the APB, along with the other thenar muscles, can be affected by a variety of medical conditions, such as spasticity (hyperactivity of the muscle post-stroke), synovitis (inflammation of the muscles’ synovial sheath), and nerve compression (e.g. Carpal Tunnel Syndrome).
The APB can also be affected by traumas, such as fractures, sprains, and strains.
Genetic conditions, such as Hemimelia, can also result in malformation or absence of the APB.
In diagnosing APB-related conditions, the medical professional usually starts with a thorough physical exam of the hand and wrist. If necessary, imaging tests may be used to assess the extent of the damage. The doctor may also request a nerve conduction velocity test, electromyography, and/or an X-ray.
Treatment for APB-related conditions may incorporate the use of physical and occupational therapy, medications, and in some cases, surgery. In severe cases, a nerve transfer procedure may be necessary to restore finger motion.
APB-related conditions can be painful and disruptive to a person’s life, so it is important to get regular check-ups and see a doctor if any of the symptoms associated with APB-related conditions arise.
