What Are the Carpometacarpal Joints?

Carpal metacarpophalangeal joint is composed of distal column carpal bone and 5 metacarpal bases.

Carpal metacarpophalangeal joint is composed of distal column carpal bone and 5 metacarpal bases.

Chinese name

Carpal joint

Foreign name

articulationes carpometacarpales

Device officer

Wrist

Belongs to

joint

Classification

Medical

Physiological Significance of Carpal and Palm Joints

Except for the thumb, carpal and palm joints, the remaining 4 carpal and palm joints are enclosed in a joint capsule, which is a flat joint with a small range of motion. The thumb carpal metacarpophalangeal joint is composed of most of the horn bones and the base of the first metacarpal bone. The articular surface is a typical saddle shape, with two axes of movement, which can be flexed and stretched around the frontal axis, adducted and abducted around the sagittal axis, and also circulated. In a living body, the movement of the thumb on the frontal axis is not a typical flexion and extension movement, but a palm movement, so it is called an opposition. This movement is an indispensable condition for humans to grasp labor tools and sports equipment. It consists of the far side of the carpal bone in the distal column and the bottom of the five metacarpal bones. The second to fifth wrist and palm joints are enclosed in a joint capsule and belong to the plane joint. Can make small sliding movements. The thumb carpal metacarpophalangeal joint, consisting of most of the horn bones and the base of the first metacarpal bone, is a saddle joint. Because the position of the first metacarpal is rotated inward by nearly 90 °, the thumb is adducted and abducted in the sagittal plane at the wrist and palm joints. Flexion and extension exercises can be performed in the frontal plane, as well as palm movements (that is, the first metacarpal is a continuous movement of abduction, flexion, adduction and internal rotation at the wrist and palm joints), and can be done around the middle axis Circular motion.

Anatomical structure of carpal and palm joints

Hand joints include radial wrist joints, intercarpal joints, wrist metacarpal joints, metacarpal joints, metacarpophalangeal joints and knuckle joints.

Radial wrist joint: The radial wrist joint consists of the wrist joint surface of the radial bone and the distal ulnar joint disc to form an articular fossa, and the scaphoid, lunar and triangular bones form the joint head. (The pea bone is located in front of the triangular bone to form a joint). The head and fossa are oval in shape, and the joint capsule itself is weak, but strengthened by the following ligaments: The radial wrist palmar ligament is stretched from the front of the lower end of the radial bone and the styloid process to the palmar surface of the boat, moon, triangle and skull. The dorsal ligament of the radial wrist extends from the radial styloid process to the lateral side of the scaphoid and the skull and most of the horns. Carpal ulnar collateral ligament, from the ulnar stem to the medial and back of the triangular bone, and the pea bone and the upper edge of the transverse carpal ligament. Arteries of the joint come from the carpal-palate and dorsal carpal branches of the interosseous palmar artery, radial artery, and ulnar artery. The deep branches of the ulnar nerve and the dorsal branch of the hand, the interosseous palm branch of the median nerve, and the interosseous dorsal branch of the radial nerve all enter the joint. The radial wrist joint can be flexed, stretched and retracted; the total range of flexion and extension is about 150 °, and flexion is slightly greater than extension; The movement of the radial wrist joint is often accompanied by the movement of the intercarpal joints. When the abduction is visible under the X-ray, the distance between the lunar bone and the ulna increases; when adducted, the boat, moon, and triangular bones move to the outside and the triangular bone contacts the joint disk.

Intercarpal joints: Intercarpal joints are basically flat joints, including joints between the bones of each row of the carpal bone and joints between the two rows of the carpal bone. The scaphoid, moon, and triangle bone form the joint between the proximal carpal bones, and the carpal ligament of the carpal ligament is completely separated from the radial wrist joint on the proximal edge of the opposite side. But on the far side, it communicates with the cavity of the transverse wrist joint. The opposite sides of most angles, small polygons, heads, and hooks also form joints; the midpoint of each joint is also connected by interosseous ligaments, so the proximal part of the joint cavity is connected with the transverse carpal joint; the distal part is connected with the palm of the wrist Joints communicate. The opposite sides of the carpal bones on both sides form the transverse carpal joint (middle wrist joint). The joints are slightly shallow. They are 2/3 concave upward on the ulnar side and 1/3 concave downward on the radial side. Inter-articular. The joint capsule of the transverse wrist joint is attached to the palm and back of each bone; there are ligament reinforcement outside the capsule: palmar ligament between the carpal bones; dorsal ligament between the carpal bones, which includes the carpal radiation radiating from the front of the skull to the surrounding wrist The ligamentous ligament; The flexor support band between the radial and ulnar bulges of the wrist, which is the transverse carpal ligament, changes the carpal groove into the carpal tunnel. Pea bones and triangular bones form independent cartilage joints. The pea hook ligaments and phalangeal ligaments outside the capsule are attached to the hook and V metacarpal floor; in fact, the pea bone can be regarded as the sesamoid of the ulnar carpi flexor muscle. The aforementioned ligaments are a continuation of the tendon.

Carpal metacarpal joint The carpal metacarpal joint is composed of a distal column of carpal bones and the base of each metacarpal bone. The thumb and carpal joints are independent saddle-like joints composed of most of the horn bones and the base of the first metacarpal bone, which can be used for flexion, extension, retraction, extension and ring movement. Small, but the fifth finger is slightly more active. Carpal palmar ligament and dorsal palmar ligament outside the joint capsule are strengthened. Carpal volar and dorsal ligaments are located between the hook bone, cephalic bone and the third and fourth metacarpal bones, and most of the horn bones and the second metacarpal bone.

Metacarpal joint: The metacarpal joint is a flat joint between the adjoining surfaces of the to metacarpal floor, and their respective capsules and cavities are connected to the carpal and palm joints. Outside the capsule, the dorsal metacarpal ligament, the metacarpal ligament of the metacarpal, and the interosseous ligament of the metacarpal are strengthened. This group has very little joint mobility.

Metacarpophalangeal joint The metacarpophalangeal joint is composed of the metacarpal head and the base of the proximal phalanx. It belongs to the ball and socket joint, but the front of the articular surface of the metacarpal head is flattened. Although it can be flexed, stretched, retracted, extended and slightly rotated, but In flexion, you cannot do the last three exercises. The joint capsule is relatively loose, with metacarpophalangeal joint ligaments strengthened on both sides; deep metacarpal ligaments of the metacarpals between the second and fourth metacarpal heads are strengthened. In addition, a tough volar ligament of fibrous cartilage is located in front of the metacarpal head. The thumb metacarpophalangeal joint is characterized by a small and wide curvature of the articular surface, with a condyle and groove in front of the metacarpal head, and the sesamoid bone. Knuckle Knuckle refers to the joint between the block at the lower end of the knuckle and the base of the lower knuckle; the joint capsule is loose, but it is strengthened by the collateral ligament and the palmar ligament; it can only be used for flexion and extension.

Hand movement characteristics: Because the thumb, carpal, and palm joints are saddle-like joints, the thumb and metacarpal rotate away from the other four metacarpals and rotate 90 ° inward. Therefore, the movement direction of the first metacarpal (carrying its phalanges) is different from those of the other four fingers . That is, flexion and extension on the coronal plane.

Carpometacarpea joint: internal, spread, and closed in the sagittal plane. The movement of the palm is the sum of the flexion of the thumb metacarpal at the wrist and the palm joint and the slight internal rotation. The thumb can be opposed to the other four fingers, making the palm of the hand a deep socket. This is one of the characteristics of upper limb mobility. The middle finger refers to the exhibition of the second to fourth fingers.