Ulnar abduction is an abduction of the fingers or hand toward the ulna and thus the opposite of radial abduction toward the ulna. Radial and ulnar abduction occur in the proximal wrist and are realized by different muscles of the hand. Ulnar abduction pain is present, for example, in ulnar disc lesions.
What is ulnar abduction?
Ulnar abduction is a splaying of the fingers or hand toward the ulna, and thus the opposite of radial abduction toward the ulna. Joints are movable joints of bones. They give human limbs their wide range of motion. Joints are capable of different types of motion to varying degrees, depending on their location. Four of the most important types of motion are flexion, extension, abduction, and adduction. Extension corresponds to an active or passive extension movement. Flexion is the opposite of this type of movement. It refers to the active or passive flexion of limbs in a particular joint. Adduction occurs when a body part is moved laterally towards the body or the respective limbs. It takes place on the frontal plane and usually leads toward the longitudinal axis of extremities. In contrast, an extremity moves away from the longitudinal axis during abduction. Thus, abduction corresponds to the lateral spreading or leading away of a limb from the center of the body. Abduction and adduction primarily involve the joints of the fingers and hand. In this context, medicine understands ulnar abduction as an abduction of the hand or fingers in the direction of the ulna, which is also called ulna in medical parlance. In contrast, abduction in the direction of the radius is referred to as radial abduction.
Function and purpose
Ulnar abduction is performed in the wrist. In the narrower sense, medicine understands this to mean the proximal and distal joints of the carpus. The proximal carpal joint corresponds to an articulated connection between the distal radius and proximal carpal bone. The triangular bone, scaphoid bone, and lunate bone make up these carpal bones. Together with an intermediate articular disc from the distal radius- ulna joint, these bones form the proximal carpal joint. The joint capsule of the area is stabilized by ligaments. Functionally, the proximal carpal joint is an egg joint with two degrees of motion. In addition to flexion, it is capable of extension. In connection with flexion, the palmar flexion of the hand or fingers in the direction of the palm should be mentioned in particular, which can occur in up to 80 degrees. In the context of extension, on the other hand, the dorsal extension of the hand and fingers in the direction of the dorsum of the hand should be emphasized, which is up to 70 degrees. As abduction movements, the proximal wrist performs radial abduction toward the radius and ulnar abduction toward the ulna. Abduction toward the radius occurs at up to 20 degrees. Ulnar abduction is around 40 degrees. The distal carpal joint is composed of the individual joints of two adjacent bones. Because of its curved shape and strong ligaments, the distal carpal joint is significantly more static and inflexible than the proximal one. It is therefore restricted in its ability to move, but forms a functional unit together with the proximal carpal joint. The abduction movements of the hand and fingers come to the proximal joint in the distribution of work in this unit. Ulnar abduction in the joint is performed by the three muscles extensor carpi ulnaris, flexor carpi ulnaris, and extensor digiti minimi. These muscles correspond to the ulnar hand flexor, ulnar hand extensor, and little finger extensor.
Diseases and complaints
When pain occurs during ulnar abduction, this phenomenon can have several causes. One of the most common causes is a lesion of the ulnar disc. This anatomic structure is located between the proximal carpal row and the ulna. In young people, lesions of this structure are usually due to overuse that has caused a tear in the structure. In older people, on the other hand, degenerative phenomena may be present in the ulnar disc, causing a fraying of the structure. Sufferers of such a lesion usually experience more or less severe pain. The pain reaches a climax during ulnar abduction of the hand or fingers. Occasionally, the pain symptoms are accompanied by a cracking sensation or swelling.The diagnosis of a lesion in the ulnar disc is made by MRI. Treatment is with anti-inflammatory drugs if the cause is degenerative. The wrist is immobilized and cooled. In younger individuals, suturing of the tear may be done. Arthroscopic removal of the ulnar disc is also an option. Pain during ulnar abduction of the fingers or hand may also be due to muscular disorders of the three muscles involved. Such diseases can be, for example, inflammation of the tendon sheath. Osteoarthritis in the proximal wrist may also be a possible cause. Arthritis pain is load-dependent at the beginning of the disease, but later expands to include periods of rest. As the disease progresses, the wrist may no longer be fully usable, so that ulnar abduction, for example, can only be performed to a limited extent or not at all. However, the inability to perform ulnar abduction can just as easily be due to paralysis of the muscles involved. Such paralysis is conceivable in the context of peripheral and central nervous diseases and is usually accompanied by more or less severe sensory disturbances of the affected area. In the case of central nervous or peripheral nerve diseases, clarification by imaging is required, for example, by MRI of the head and spine and by imaging of the affected hand.
