The abductor pollicis brevis tendon inserts on the radial base of the thumb proximal phalanx and sends a significant slip into the radial wing of the extensor mechanism at the thumb MCP joint. This extensor slip allows APB to contribute to thumb MCP extension despite its primary role in palmar abduction. The tendon lies superficial to the flexor pollicis brevis in the thenar eminence.
The APB tendon insertion is the site of its contribution to the radial extensor expansion, which explains why median nerve palsy (APB denervation) selectively impairs thumb opposition and palmar abduction while the extrinsic extensors remain intact. The tendon is a key landmark in carpal tunnel release: the incision distal to the wrist crease should stay just ulnar to APB to avoid entering the thenar musculature. APB atrophy is the hallmark of chronic carpal tunnel syndrome visible as flattening of the thenar eminence.
Chronic median nerve compression at the wrist produces progressive denervation of the abductor pollicis brevis with visible and palpable thenar eminence flattening, reduced thumb palmar abduction strength, and difficulty with precision grip, an indication for carpal tunnel surgical release.
This website uses cookies to enhance your experience. Some are essential for site functionality, while others help us analyze and improve your usage experience. Please review your options and make your choice.
If you are under 16 years old, please ensure that you have received consent from your parent or guardian for any non-essential cookies.
Your privacy is important to us. You can adjust your cookie settings at any time. For more information about how we use data, please read our privacy policy. You may change your preferences at any time by clicking on the settings button below.
Note that if you choose to disable some types of cookies, it may impact your experience of the site and the services we are able to offer.
Some required resources have been blocked, which can affect third-party services and may cause the site to not function properly.
This website uses cookies to enhance your browsing experience and ensure the site functions properly. By continuing to use this site, you acknowledge and accept our use of cookies.
