This document discusses the extensor retinaculum of the hand and the dorsal digital expansion. It describes the extensor retinaculum's attachments, its division into 6 compartments through which various tendons pass. It also explains how the dorsal digital expansion forms a hood over each metacarpal head and trifurcates into bands at the proximal phalanx, with contributions from surrounding tendons.

1. EXTENSOR RETINACULUM &
DORSAL DIGITAL EXPANSION
Lecture by
Dr.N.Mugunthan.MBBS,MS,DNB,MNAMS,PhD.
Professor of Anatomy
SMIMS

2. Learning objectives
Extensor retinaculum
• Attachments
• 6 compartments
• Structures passing deep to it
Dorsal digital expansion
• Formation
© Dr.N.Mugunthan

3. Extensor retinaculum of hand
© Dr.N.Mugunthan

4. Back of forearm
Superficial group:
• *Brachioradialis
• *Anconeus
• *Extensor carpi radialis longus
• Extensor carpi radialis brevis
• Extensor digitorum
• Extensor digiti minimi
• Extensor carpi ulnaris
Deep group:
• Supinator
• Abductor pollicis longus
• Extensor pollicis longus
• Extensor pollicis brevis
• Extensor indicis
© Dr.N.Mugunthan

5. Back of forearm cont…
Superficial group:
• *Brachioradialis
• *Anconeus
• *Extensor carpi radialis longus
• Extensor carpi radialis brevis
• Extensor digitorum
• Extensor digiti minimi
• Extensor carpi ulnaris
Deep group:
• Supinator
• Abductor pollicis longus
• Extensor pollicis longus
• Extensor pollicis brevis
• Extensor indicis
© Dr.N.Mugunthan

6. Extensor retinaculum
Attachment:
• Medial end: styloid process of
ulna, triquetral and pisiform
• Lateral end: lower part of anterior
border of radius
© Dr.N.Mugunthan

7. Extensor retinaculum cont…
From lateral to medial: following tendons are
passing:
• 1st compartment: abductor pollicis longus &
extensor pollicis brevis tendons
• 2nd compartment: extensor carpi radialis
longus & brevis tendons
• 3rd compartment: extensor pollicis longus
tendon
• 4th compartment: extensor indicis tendon,
extensor digitorum tendon, anterior
interosseous artery & posterior
interosseous nerve
• 5th compartment: extensor digiti minimi
tendon
• 6th compartment: extensor carpi ulnaris
tendon
© Dr.N.Mugunthan

8. Anatomical snuff box
Boundaries:
• Medial: tendon of extensor
pollicis longus
• Lateral: tendon of abductor
pollicis longus & extensor
pollicis brevis
• Floor : styloid process of
radius, scaphoid & base of
1st metacarpal
• Roof : skin , superficial
fascia which contains
cephalic vein & deep fascia
Contents :
• Terminal part of radial
artery © Dr.N.Mugunthan

9. Dorsal digital expansion of hand
© Dr.N.Mugunthan

10. Hand
• 4 lumbricals
Thenar muscles
• 1.Abductor pollicis brevis
• 2.Flexor pollicis brevis
• 3.Opponens pollicis
• *Adductor pollicis (Deep
muscle)
Hypothenar muscles
• 1.Flexor digiti minimi
• 2.Opponens digiti minimi
• 3.Abductor digiti minimi
• *Palmaris brevis (superficial
muscle)
• 4 Palmar interosseous
• 4 Dorsal interosseous
© Dr.N.Mugunthan

11. Hand cont…
• 4 lumbricals
Thenar muscles
• 1.Abductor pollicis brevis
• 2.Flexor pollicis brevis
• 3.Opponens pollicis
• *Adductor pollicis (Deep
muscle)
Hypothenar muscles
• 1.Flexor digiti minimi
• 2.Opponens digiti minimi
• 3.Abductor digiti minimi
• *Palmaris brevis (superficial
muscle)
• 4 Palmar interosseous
• 4 Dorsal interosseous
© Dr.N.Mugunthan

12. Hand cont…
• 4 lumbricals
Thenar muscles
• 1.Abductor pollicis brevis
• 2.Flexor pollicis brevis
• 3.Opponens pollicis
• *Adductor pollicis (Deep
muscle)
Hypothenar muscles
• 1.Flexor digiti minimi
• 2.Opponens digiti minimi
• 3.Abductor digiti minimi
• *Palmaris brevis (superficial
muscle)
• 4 Palmar interosseous
• 4 Dorsal interosseous
© Dr.N.Mugunthan

13. Hand cont…
• 4 lumbricals
Thenar muscles
• 1.Abductor pollicis brevis
• 2.Flexor pollicis brevis
• 3.Opponens pollicis
• *Adductor pollicis (Deep
muscle)
Hypothenar muscles
• 1.Flexor digiti minimi
• 2.Opponens digiti minimi
• 3.Abductor digiti minimi
• *Palmaris brevis (superficial
muscle)
• 4 Palmar interosseous
• 4 Dorsal interosseous
© Dr.N.Mugunthan

14. Hand cont…
• 4 lumbricals
Thenar muscles
• 1.Abductor pollicis brevis
• 2.Flexor pollicis brevis
• 3.Opponens pollicis
• *Adductor pollicis (Deep
muscle)
Hypothenar muscles
• 1.Flexor digiti minimi
• 2.Opponens digiti minimi
• 3.Abductor digiti minimi
• *Palmaris brevis (superficial
muscle)
• 4 Palmar interosseous
• 4 Dorsal interosseous
© Dr.N.Mugunthan

15. Dorsal digital expansion
• *Each extensor tendon
covers the dorsal surface of
head of metacarpal and
proximal phalanx and forms
triangular shaped dorsal
digital expansion
• Base: expansions forms a
hood over metacarpal head
• Apex: expansion at the distal
end of proximal phalanx
trifurcates into a median and
two lateral bands. © Dr.N.Mugunthan

16. • Lateral margin: expansions of
lateral margin receives the
tendon of both lumbrical &
interosseous
• Medial margin: expansions of
medial margin receives the
tendon of interosseous only
• Proximal wing tendons:
contributed by palmar & dorsal
interosseous tendons (join close
to MCP joint)
• Distal wing tendons:
contributed by tendon of
lumbricals (join close to
proximal IP joint)
Dorsal digital expansion cont….
© Dr.N.Mugunthan

17. Summary
Extensor retinaculum
• Attachments
• 6 compartments
• Structures passing deep to it
Dorsal digital expansion
• Formation
© Dr.N.Mugunthan