Bones of hand and anatomical spaceas

Lecture Notes of bones of hand and the anatomical spaces of the upper limb

1. BONES OF HAND AND ANATOMICAL SPACES DR. EIMAN SUMAYYAH

2. Bones of the Hand The bones of the hand provide support and flexibility to the soft tissues. They can be divided into  three  categories: Carpal bones  (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  (Distal) – The bones of the fingers. Each finger has three phalanges, except for the thumb, which has two.

3. Carpal Bones Proximal Row (lateral to medial) Distal Row (lateral to medial) Scaphoid Lunate Triquetrum Pisiform (a sesamoid bone, formed within the tendon of the flexor carpi ulnaris ) Trapezium Trapezoid Capitate Hamate (has a projection on its palmar surface, known as the ‘hook of hamate’

4. Collectively, the carpal bones form an  arch  in the coronal plane. A membranous band, the flexor retinaculum, spans between the medial and lateral edges of the arch, forming the  carpal tunnel . Proximally, the scaphoid and lunate articulate with the radius to form the  wrist joint  (also known as the ‘radio-carpal joint’). In the distal row, all of the carpal bones articulate with the metacarpals.  By  TeachMeSeries Ltd  (2020)

5. Metacarpal Bones The metacarpal bones articulate proximally with the carpals, and distally with the proximal phalanges. They are numbered, and each associated with a digit: 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  interossei  muscles.

6. There are two common fractures of the metacarpals: Boxer’s fracture  –  A fracture of the 5th metacarpal neck. It is usually caused by a clenched fist striking a hard object.  The distal part of the fracture is displaced anteriorly, producing shortening of the affected finger. Bennett’s fracture  – A fracture of the 1st metacarpal base, caused by forced hyperabduction of the thumb. This fracture extends into the first carpometacarpal joint leading to instability and subluxation of the joint. As a result, it often needs surgical repair.

7. 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.

8. CUBIT FOSSA

9. CONTENTS OF CUBITAL NERVE Mnemonic for contents of the cubital fossa –  R eally  N eed  B eer  T o  B e  A t  M y  N icest.

10. Carpal tunnel

11. CONTENTS OF CARPAL TUNNEL The tendon of  flexor pollicis longus Four tendons of  flexor digitorum profundus Four tendons of  flexor digitorum superficialis Median Nerve

12. The Extensor Tendon Compartments of the Wrist The  extensor tendon compartments  of the wrist are six tunnels which transmit the long extensor tendons from the forearm into the hand They are located on the posterior aspect of the wrist. Each tunnel is lined internally by a  synovial sheath  and separated from one another by fibrous septa.

13. Compartment 1 The first extensor compartment is located on the  lateral  (radial) aspect of the wrist. It transmits two tendons: Extensor pollicis brevis Abductor pollicis longus De Quervains Tendosynovitis

14. Compartment 2 The second extensor compartment contains the tendons of the  extensor carpi radialis  longus and extensor carpi radialis brevis. This compartment is separated from compartment 3 by  Lister’s tubercle  – a bony prominence of the distal aspect of the radius.

15. Compartment 3 Compartment three conducts the  extensor pollicis longus  tendon – this forms the medial border of the anatomical snuffbox.

16. Compartment 4 The 4th extensor compartment of the wrist transmits the tendons of the  extensor digitorum  and extensor indicis. Compartment 5 Compartment five contains the  extensor digiti minimi  tendon, which travels into the little finger. Compartment 6 The sixth compartment is the located on the medial (ulnar) aspect of the wrist. It conducts the tendon of the  extensor carpi ulnaris .

17. The Anatomical Snuffbox The  anatomical snuffbox  (also known as the radial fossa), is a triangular depression found on the lateral aspect of the dorsum of the hand. It is located at the level of the  carpal bones , and best seen when the thumb is extended.

18. Borders As the snuffbox is triangularly shaped, it has three borders, a floor, and a roof: Ulnar (medial) border : Tendon of the extensor pollicis longus. Radial (lateral) border : Tendons of the extensor pollicis brevis and abductor pollicis longus. Proximal border : Styloid process of the  radius . Floor : Carpal bones; scaphoid and trapezium. Roof : Skin.

19. Contents The main contents of the  anatomical snuffbox  are the radial artery, a branch of the  radial nerve , and the cephalic vein

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