This short article is for undergraduate medical students and paramedics. Orthopaedic surgeons can revise and refresh anatomy and its relevance to clinical conditions.
The video describes mainly skeletal anatomy of hand and few other structures related to some clinical conditions which are discussed. Details of muscles, joints, nerves, blood vessels and tissue compartments are not discussed in this video.
Discussion of this video is summarised below for the viewers to comprehend knowledge and understand the subject thoroughly.
Medical Terminologies Used:
Proximal means towards the centre of body. For example shoulder is proximal to elbow joint.
Distal is opposite to proximal and it means away from the centre of the body.
Lateral means away from the midline of the body.
Medial means towards the midline of the body.
Bones of the hand consist of carpal bones, metacarpals and phalanges.
Carpal Bones: There are eight carpal bones, arranged in two rows of four each. These lie in the proximal part of hand, just distal to the wrist joint. The proximal row (lateral to medial) consists of Scaphoid, Lunate, Triquetrum and Pisiform. The distal row (lateral to medial) consists of Trapezium, Trapezoid, Capitate and Hamate. In the video the list of carpal bones is in clockwise direction starting from scaphoid, if looking from palmar aspect. But the direction will be different in both hands, clockwise for right and anticlockwise for left hand. This may be confusing therefore I have used this direction which is also standard.
Mnemonics to remember these carpal bones are many, one is mentioned in the video but there are others on internet and can be used as per choice.
Metacarpals: There are five metacarpal bones, one for each digit. These are named first to fifth metacarpal bones, starting from thumb. Metacarpals lie distal to carpals and proximal to phalanges (the bones of thumb and fingers).
Phalanges (singular is phalanx): These are bones of thumb and fingers. In the thumb there are only two phalanges, proximal phalanx and distal phalanx. In each finger there are three phalanges, proximal, middle and distal.
Joints of Hand:
Wrist joint, is between distal ends radius and ulna (forearm bones) and proximal row of carpal bones.
Inter-carpal joints are between different carpal bones.
Carpo metacarpal (CMC) joints are between distal row of carpal bones and bases (proximal ends) of metacarpal bones.
Metacarpo Phalyngeal (MCP) joints are between heads (distal ends) of metacarpals and proximal ends of phalanges.
Inter Phalangeal (IP) joints, are between phalanges of fingers and thumb. These are proximal and distal inter phalangeal joints (PIP & DIP). As the thumb has only two phalanges therefore there is only inter phalangeal joint. All fingers have PIP and DIP joints.
Carpal Tunnel: It is narrow tunnel on the palmar side of hand, just distal to the wrist joint. The floor and sides of the tunnel are formed by the carpal bones. The roof (anteriorly) is formed by a strong tissue band known as flexor retinaculum which is also known as transverse carpal ligament. The structures which pass through this tunnel are long flexor tendons of fingers and thumb i.e. flexor digitorum superficialis and flexor digitorum profundus for four fingers and flexor pollicis longus for thumb. The most important structure passing through this tunnel is median nerve. It gives sensory supply to the skin of thumb, index finger, mid finger and radial half of ring finger. The nerve also supplies few muscles of the hand.
Carpal Tunnel Syndrome (CTS): Any undue pressure in this tunnel compresses median nerve. There are many causes which result in swelling of synovial membranes covering the tendons inside this tunnel. The symptoms are pain and numbness of the supplied skin area (3 ½ fingers) and weakness of supplied muscles. This condition is more in females.
Dupuytren’s Contracture: Palmaris longus is a muscle of forearm. Its tendon passes anterior to the flexor retinaculum of hand. The tendon divides into four parts for fingers and becomes part of palmar aponeurosis. In Dupuytren’s contracture, there is thickening and nodule formation in palmar aponeurosis in early stage. Later on if it progresses, then results in flexion contractures of fingers.
Trigger Finger: Each flexor digitorum profundus tendon in fingers passes through fibrous tunnels on the anterior aspect of phalanges and IP joints. In trigger finger there is some nodular swelling of the tendon at MCP joint level which passes with difficulty in the fibrous tunnel. The symptom is difficulty in extending (straightening) of the flexed finger. It can be extended with difficulty and pain and often needs help of other hand or other person. The extension is like a trigger of a gun, hence its name. The condition also affects thumb, known as trigger thumb. In this case flexor pollicis longus tend is involved.