Radial abduction is a flexion movement of the hand or fingers toward the radius, as performed in the proximal wrist by five hand muscles. The range for movement toward the thumb side is up to 20 degrees. Radial abduction may be impaired in muscle disease.
What is radial abduction?
Radial abduction is a flexion movement of the hand or fingers toward the radius, as performed in the proximal wrist by five hand muscles. The movable connection between several bony skeletal elements is also called a joint. Through the joints, human body parts and extremities have a wide range of motion with different forms and directions of movement. For example, the term anteversion refers to movements in the sagittal plane. Extension summarizes all active and passive extension movements in a particular joint that straighten the associated body part. Flexion, on the other hand, refers to the active and passive bending movements in a joint. Adduction, in turn, involves moving a body part toward the center of the body or the longitudinal axis of the limb and applying it in this manner. The opposite of this is abduction. This form of movement corresponds to a lateral continuation or splaying of body parts that originates from the center of the body or the longitudinal axis. Abduction characteristically occurs in the frontal plane. Radial abduction is therefore a leading away of the fingers or hand in the direction of the radius. The term radius refers to the radius bone of the forearm. This is a tubular bone at the end of the upper arm that extends into the carpus. When abduction occurs in the direction of the ulna, it is referred to as ulnar abduction.
Function and task
Radial abduction occurs in the carpal joint. As such, the distal and proximal wrist joints are grouped together. The proximal carpal joint is the articular connection between the distal end of the radius (facies articularis carpi radialis) and the three proximal carpal bones (ossa carpalia). The proximal carpal bones are known to be the scaphoid bone (Os scaphoideum), the lunate bone (Os lunatum) and the triangular bone (Os triquetrum). The interarticular disc of the radius- ulna joint is involved in the articular formation of this carpal joint. The joint capsule of this joint is stabilized by radiating ligaments. Functionally, the joint is an ellipsoid joint (articulatio ellipsoidea) with two different degrees of freedom. In addition to flexion toward the palm and extension toward the dorsum of the hand, it can perform abduction movements toward the ulna and radius. Flexion is up to 80 degrees and dorsal extension toward the dorsum of the hand is up to 70 degrees. The abduction movements in this joint have a radius of about 20 degrees toward the radius. Ulnar abduction toward the ulna is as much as 40 degrees. The distal carpal joint is much more restricted in its movements. Consequently, the proximal carpal joint is particularly instrumental in the movement of the hand and fingers. Radial abduction in the proximal wrist is performed by various muscles. The most important of these muscles involved are the extensor carpi radialis longus muscle, the abductor pollicis longus muscle and the extensor pollicis longus muscle. However, the flexor pollicis longus muscle and the flexor carpi radialis muscle also play an important role in radial abduction of the hand or fingers. The flexor pollicis longus muscle and the flexor carpi radialis muscle are so-called flexors. In contrast, the extensor carpi radialis longus muscle, the abductor pollicis longus muscle and the extensor pollicis longus muscle are known as extensors of the hand. Another term for extensor muscles is extensor. Flexors are also called flexors.
Diseases and disorders
Radial abduction of the hand or fingers may be limited, cause pain, or generally become impossible due to disease of the realizing muscles. Muscle diseases, for example, may have inflammatory causes. In this context, tendon sheath inflammation should be mentioned in particular, which can cause severe pain. Tendon sheath inflammation can occur, for example, in the context of overuse and may also impair radial abduction of the hand in the muscles mentioned. Osteoarthritis in the proximal carpal joint can also restrict radial abduction.In osteoarthritis, the cartilage of the joint is broken down piece by piece. Often, this phenomenon is the result of a malposition. However, overloads are also conceivable in this context. Initially, arthrosis pain is load-dependent. In the later course, a permanent pain sets in, which can also be felt during rest phases. When the cartilage is worn away, the joint surfaces rub against each other without protection and thus wear each other down. Pain and restricted movement in the proximal wrist can also be the result of carpal tunnel syndrome. In the course of the median nerve, compression of the carpal tunnel occurs in this condition. This is an anatomical structure made of bones and ligaments. The nerve irritation in this structure typically causes sensation and pain. It is only later in the course that restrictions in the ability to move in the affected supply area occur. Compression of the ulnar nerve near the carpus can also cause pain, sensory disturbances and loss of movement. This condition is also known as Loge de Guyon syndrome and can cause atrophy of the finger and hand muscles in later stages. Long-term, everyday compression of the nerve is one of the most significant causes of the condition. Ulcers can also compress the nerve under certain circumstances. Much less commonly, loss of hand motion is caused by polyneuropathies or central nervous diseases.
