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The palmar plate moves in three phases during joint flexion. First, it slides back toward the hand. Next, it is lifted away from the proximal phalanx by the A3 pulley. Last, a lip on the middle phalanx rolls into a recess on the plate. If the A3 pulley is not intact, the normal three phases of motion do not occur and instead the plate crumples. [7]
In human anatomy, the annular ligaments of the fingers, often referred to as A pulleys, are the annular part of the fibrous sheathes of the fingers. Four or five such annular pulleys, together with three cruciate pulleys , form a fibro-osseous tunnel on the palmar aspect of the hand through which passes the deep and superficial flexor tendons .
This is often remembered by the mnemonic PAD-DAB, as the Palmar interosseous muscles ADduct, and the Dorsal interosseous muscles ABduct. The axial line goes down the middle of the 3rd digit, towards the palm of the hand (it's an imaginary line). Both sets of muscles are innervated by the deep branch of the ulnar nerve. [1]
The lumbrical innervation always follows the innervation pattern of the associated muscle unit of flexor digitorum profundus (i.e. if the muscle units supplying the tendon to the middle finger are innervated by the median nerve, the second lumbrical will also be innervated by the median nerve). [6]
The metacarpal bones are connected together by dorsal, palmar, and interosseous ligaments. The dorsal metacarpal ligaments (ligamenta metacarpalia dorsalia) and palmar metacarpal ligaments (ligamenta metacarpalia palmaria) pass transversely from one bone to another on the dorsal and palmar surfaces.
The lateral and medial portions of the palmar aponeurosis are thin, fibrous layers, which cover, on the radial side, the muscles of the ball of the thumb, and, on the ulnar side, the muscles of the little finger; they are continuous with the central portion and with the fascia on the dorsum of the hand.
The lack of palmaris longus muscle does result in decreased pinch strength in fourth and fifth fingers. The absence of palmaris longus muscle is more prevalent in females than males. [5] The palmaris longus muscle can be observed by touching the pads of the fourth finger and thumb and flexing the wrist. The tendon, if present, will be visible ...
The flexor retinaculum (transverse carpal ligament or anterior annular ligament) is a fibrous band on the palmar side of the hand near the wrist. It arches over the carpal bones of the hands, covering them and forming the carpal tunnel .