Hand and Wrist Flashcards
Describe the three caragories of bones in the hand
Carpal bones (Most proximal) – A set of eight irregularly shaped bones. These are located in the wrist area.
Metacarpals – There are five metacarpals, each one related to a digit
Phalanges (Most distal) – The bones of the fingers. Each finger has three phalanges, except for the thumb, which has two.
What are the 6 types basic of hand movement?
Describe the bones of the carpel tunnel
The carpal bones are a group of eight, irregularly shaped bones. They are organised into two rows – proximal and distal.
In the proximal row, the bones are (lateral to medial):
Scaphoid
Lunate
Triquetrum
Pisiform – A sesamoid bone, formed within the tendon of the flexor carpi ulnaris
In the distal row, the bones are (lateral to medial):
Trapezium
Trapezoid
Capitate
Hamate – has a projection on its palmar surface called the hook of hamate
Proximally, the scaphoid and lunate articulate with the radius to form the wrist joint. In the distal row, all of the carpal bones articulate with the metacarpals
Describe the metacarpal bones of the hand
Metacarpal I – Thumb.
Metacarpal II – Index finger.
Metacarpal III – Middle finger.
Metacarpal IV – Ring finger.
Metacarpal V – Little finger.
Each metacarpal consists of a base, shaft and a head. The medial and lateral surfaces of the metacarpals are concave, allowing attachment of the interoessei muscles.
What are the phalanges?
The phalanges are the bones of the fingers. The thumb has a proximal and distal phalanx, while the rest of the digits have proximal, middle and distal phalanges.
How are muscles within the hand divided?
Muscles acting on the hand can be divided into two groups: extrinsic and intrinsic muscles.
The extrinsic muscles are located in the anterior and posterior compartments of the forearm. They control crude movements and produce a forceful grip.
The intrinsic muscles of the hand are located within the hand itself. They are responsible for the fine motor functions of the hand.
What are the thenar muscles?
The thenar muscles are three short muscles located at the base of the thumb. The muscle bellies produce a bulge, known as the thenar eminence. They are responsible for the fine movements of the thumb.
The median nerve innervates all the thenar muscles.
- Flexor Pollicis Brevis
- Abductor Pollicis Brevis
- Opponens Pollicis
Opponens Pollicis
The opponens pollicis is the largest of the thenar muscles, and lies underneath the other two.
Origin: Tubercle of the trapezium, and the associated flexor retinaculum.
Insertion: Lateral margin of the metacarpal of the thumb (i.e. the first metacarpal).
Actions: Opposes the thumb, by medially rotating and flexing the metacarpal on the trapezium.
Innervation: Median nerve.
Abductor Pollicis Brevis
This muscle is found anteriorly to the opponens pollicis and proximal to the flexor pollicis brevis.
Origin: Tubercles of the scaphoid and trapezium, and from the associated flexor retinaculum.
Attaches: Lateral side of proximal phalanx of the thumb.
Actions: Abducts the thumb.
Innervation: Median nerve.
Flexor Pollicis Brevis
The most distal of the thenar muscles.
Originates: from the tubercle of the trapezium and from the associated flexor retinaculum.
Attaches: to the base of the proximal phalanx of the thumb.
Actions: Flexes the metacarpophalangeal (MCP) joint of the thumb.
Innervation: Median nerve.
What are the hypothenar muscles?
The hypothenar muscles produce the hypothenar eminence – a muscular protrusion on the medial side of the palm, at the base of the little finger. These muscles are similar to the thenar muscles in both name and organisation.
The ulnar nerve innervates the muscles of the hypothenar eminence.
- Opponens Digiti Minimi
- Flexor Digiti Minimi Brevis
- Abductor Digiti Minimi
Opponens Digiti Minimi
The opponens digit minimi lies deep to the other hypothenar muscles.
Attachments: Originates from the hook of hamate and associated flexor retinaculum, inserts into the medial margin of metacarpal V.
Actions: It rotates the metacarpal of the little finger towards the palm, producing opposition.
Innervation: Ulnar nerve.
Abductor Digiti Minimi
The most superficial of the hypothenar muscles.
Attachments: Originates from the pisiform and the tendon of the flexor carpi ulnaris. It attaches to the base of the proximal phalanx of the little finger.
Actions: Abducts the little finger.
Innervation: Ulnar nerve.
Flexor Digiti Minimi Brevis
This muscles lies laterally to the abductor digiti minimi.
Attachments: Originates from the hook of hamate and adjacent flexor retinaculum, and inserts into the base of the proximal phalanx of the little finger.
Actions: Flexes the MCP joint of the little finger.
Innervation: Ulnar Nerve.
Describe the lumbricals of the hand
There are four lumbricals in the hand, each associated with a finger. They are very crucial to finger movement, linking the extensor tendons to the flexor tendons.
Denerveration of these muscles is the basis for the ulnar claw and hand of benediction.
Attachments: Each lumbrical originates from a tendon of the flexor digitorum profundus. They pass dorsally and laterally around each finger, and inserts into the extensor hood.
Actions: The flex at the MCP joint, and extend at the interphalangeal (IP) joints of each finger.
Innervation: The medial two lumbricals (of the little and ring fingers) are innervated by the ulnar nerve. The lateral two lumbricals (of the index and middle fingers) are innervated by the median nerve.
What are the interossei muscles?
The interossei muscles are located between the metacarpals. They can be divided into two groups: the dorsal and palmar interossei.
In addition to their actions of abduction (dorsal interossei) and adduction (palmar interossei) of the fingers, the interossei also assist the lumbricals in flexion and MCP joints and extension at the IP joints.
Dorsal Interossei
The most superficial of all dorsal muscles, these can be palpated on the dorsum of the hand. There are four dorsal interossei muscles.
Attachments: Each interossei originates from the lateral and medial surfaces of the metacarpals. They attach into the extensor hood and proximal phalanx of each finger.
Actions: Abduct the fingers at the MCP joint.
Innervation: Ulnar nerve.
Palmar Interossei
These are located anteriorly on the hand. There are three palmar interossei muscles.
Attachments: Each interossei originates from a medial or lateral surface of a metacarpal, and attaches into the extensor hood and proximal phalanx of same finger.
Actions: Adducts the fingers at the MCP joint.
Innervation: Ulnar nerve.
Palmaris Brevis
This is a small, thin muscle, found very superficially in the subcutaneous tissue of the hypothenar eminence.
Attachments: Originates from the palmar aponeurosis and flexor retinaculum, attaches to the dermis of the skin on the medial margin of the hand.
Actions: Wrinkles the skin of the hypothenar eminence and deepens the curvature of the hand, improving grip.
Innervation: Ulnar nerve.
Adductor Pollicis
This is large triangular muscle with two heads. The radial artery passes anteriorly through the space between the two heads, forming the deep palmar arch.
Attachments: One head originates from metacarpal III. The other head originates from the capitate and adjacent areas of metacarpals II and III. Both attach into the base of the proximal phalanx of the thumb.
Actions: Adductor of the thumb.
Innervation: Ulnar nerve.
What are the borders of the carpal tunnel?
The carpal tunnel is formed by two layers: a deep carpal arch and a superficial flexor retinaculum. The deep carpal arch forms a concave surface, which is converted into a tunnel by the overlying flexor retinaculum.
What is the carpal arch?
Concave on the palmar side, forming the base and sides of the carpal tunnel.
Formed laterally by the scaphoid and trapezium tubercles
Formed medially by the hook of the hamate and the pisiform
What is the flexor retinaculum?
Thick connective tissue which forms the roof of the carpal tunnel.
Turns the carpal arch into the carpal tunnel by bridging the space between the medial and lateral parts of the arch.
Originates on the lateral side and inserts on the medial side of the carpal arch.
To find where the carpal tunnel begins on yourself, locate your distal wrist crease, which aligns with the entrance of the carpal tunnel.
What are the contents of the carpal tunnel?
The carpal tunnel contains a total of 9 tendons, surrounded by synovial sheaths, and the median nerve. The palmar cutaneous branch of the median nerve is given off prior to the carpal tunnel, travelling superficially to the flexor retinaculum.
Name the tendons of the carpel tunnel
The tendon of flexor pollicis longus
Four tendons of flexor digitorum profundus
Four tendons of flexor digitorum superficialis
The 8 tendons of the flexor digitorum profundus and flexor digitorum superficialis are surrounded by a single synovial sheath. The tendon of flexor pollicis longus is surrounded by its own synovial sheath. These sheaths allow free movement of the tendons.
Sometimes you may hear that the carpal tunnel contains another tendon, the flexor carpi radialis tendon, but this is located within the flexor retinaculum and not within the carpal tunnel itself!
Describe the blood supply of the hand
The hand has a very good blood supply, with many anastomosing arteries, allowing the hand to be perfused when grasping or applying pressure. A good majority of these arteries are superficial, allowing for heat loss when needed. In the hand, the ulnar and radial arteries interconnect to form two arches, from which branches to the digits emerge.
How does the ulnar artery supply blood to the hand?
Ulnar artery – contributes mainly to the supply of the rest of the digits, and the medial side of the index finger
The ulnar artery moves into the hand anteriorly to the flexor retinaculum, and laterally to the ulnar nerve. In the hand, it divides into two branches, the superficial palmar arch, and the deep palmar branch.
From the superficial palmar arch, common palmar digital arteries arise, supplying the digits. The superficial palmar arch then anastamoses with a branch of the radial artery. The superficial palmar arch is found anteriorly to the flexor tendons in the hand, deep to the palmar aponeurosis.
Describe how the radial artery delivers blood to the hand
Radial artery – contributes mainly to supply of the thumb and the lateral side of the index finger
The radial artery enters the hand dorsally, crossing the floor of the anatomical snuffbox. It turns medially and moves between the heads of the adductor pollicis. The radial artery then anastamoses with the deep palmar branch of the ulnar artery, forming the deep palmar arch, which gives rise to five arteries supplying the digits.
What is the Allen test?
The Allen test is a test to determine whether the patency of the radial or ulnar artery is normal. It is performed prior to radial cannulation or catheterisation, because placement of such a catheter often results in thrombosis. Therefore the test is used to reduce the risk of ischemia to the hand.
A positive Allen’s test means that the patient does not have dual blood supply to the hand, which is a negative indication for catheterisation or removal of the radial arteries.
Describe the cutaneous distribution of the median nerve in the hand
The median nerve is responsible for the cutaneous innervation of part of the hand. This is achieved via two branches:
Palmar cutaneous branch – Arises in the forearm and travels into the hand. It innervates the lateral aspect of the palm. This nerve does not pass through the carpal tunnel, and is spared in carpal tunnel syndrome.
Palmar digital cutaneous branch – Arises in the hand. Innervates the palmar surface and fingertips of the lateral three and half digits.
Describe the cutaneous distribution of the radial nerve in the hand
The superficial branch – is a terminal division of the radial nerve. It innervates the dorsal surface of the lateral three and half digits, and their associated palm area.
Describe the cutaneous distribution of the ulnar nerve in the hand
here are three branches of the ulnar nerve that are responsible for its cutaneous innervation.
Two of these branches arise in the forearm, and travel into the hand:
Palmar cutaneous branch: Innervates the skin of the medial half of the palm.
Dorsal cutaneous branch: Innervates the skin of the medial one and a half fingers, and the associated dorsal hand area.
The last branch arises in the hand itself:
Superficial branch – Innervates the palmar surface of the medial one and a half fingers.
What are the borders of the Anatomical Snuffbox?
Lateral = tendons of abductor pollicus longus and extensor pollicus brevis
Medial = tendon of extensor pollicis longus
Floor = scaphoid bone
Roof = skin
Contents = radial artery
