The carpus has 3 joints - the antebrachiocarpal, middle carpal, and carpometacarpal joints. The middle carpal and carpometacarpal joints always communicate. There are 8 carpal bones arranged in 2 rows. Various ligaments and tendon sheaths stabilize the carpal bones and allow for flexion and extension. The carpal canal encloses tendons and nerves within the palmar annular ligament. Anatomy of the carpus is complex with multiple bones, joints, ligaments, and tendon sheaths that require careful study to understand carpal function and regional anesthesia.

1. Carpal Anatomy
Radiology Rounds
December 15th, 2014

2. Anatomy
• 3 joints
– Antebrachiocarpal joint
– Middle carpal joint
– Carpomatacarpal joint
• MCJ and CMCJ always communicate
• Palmar outpauching of CMCJ extends distal
– Inadvertent anesthesia of joint when blocking
prox metacarpal joint

3. Anatomy
• Diffusion of mepivacaine between:
– ABCJ and MCJ occurred in 84% of limbs
– MCJ and ABCJ occurred in 96% of limbs
(Gough MR et al. EVJ 2002)
• Consider evaluation of whole region
– Carpus
– Carpal canal
– Proximal metacarpus

4. Anatomy
• Bones
– Radius
– Proximal row
• RCB, ICB, UCB, ACB
– Distal row
• IICB, IIICB, IVCB, occasionally ICB and rarely VCB
– Metacarpal
• IIMCB, IIIMCB, IVMCB

5. Anatomy
• Soft-tissues:
– Intercarpal ligaments
– Collateral ligaments
– Fibrous joint capsule
– Palmar carpal ligament

6. Anatomy
• Dorsal:
– Extensor carpi radialis (sheath)
• Dorsolateral:
– Common digital extensor tendon (sheath)
• Extensor retinaculum – distal radius at physeal
scar
– stabilize ECR and CDET

7. Tendon sheaths
j Flex carpi radialis (resected)
k Ext carpi radialis
m CDE (humeral head)
n CDE (radial head)
o DDF
p Lat dig flexor
q Ulnaris lateralis
r Flexor carpi ulnaris (resected)
s Ext carpi obliquus
All tendons passing over carpus
have sheath, except:
• Short tendon of Ulnaris
lateralis
• Flexor carpi ulnaris

8. Dorsal aspect
1 Radius
2 ECRT
3 Long dig abductor T
4 CDET
5 Extensor retinaculum
7 Lat digital extensor T
L

9. Dorsal aspect
1 Radius
2 Groove for the Long dig adbuctor T.
3 Groove for the ECRT
4 Groove CDET
6 MCL
7 RCB
8 /10/17 Dorsal intercarpal ligament
9 ICB
11 UCB
12 LCL
14 IIICB
15 IVCB
16 Dorsal metacarpal ligament
L

10. Palmar aspect
(no ACB)
Plantar intercarpal ligaments
1-2 RCB and Radius
3 ICB and Radius
4 Stump of ligament connecting ICB and
ACB
5 RCB and IICB (med palmar intercarpal
lig)
6 IICB and IIIMB
7 IIICB and IIIMB
8 Ulnar and III and IVCB (lateral palmar
intercarapal lig)
9 Short MCL

11. Palmar aspect
(retinaculum has been removed)
1 Extensor carpi ulnaris T
2 Flex dig profundus T
3 Flex carpi ulnaris T
4 Flex carpi radialis T
5 Ext dig lateralis T
6 Ext carpi ulnaris to the ACB
7 Ext carpi ulnaris
10 Flex dig superficialis T
ACB
L
IV
II

12. Lateral aspect
1 Extensor carpi radialis T
3 CDET
4 Ext dig lateralis T
5 DDF muscle (humeral head)
6 Ext carpi ulnaris (M. ulnaris lateralis)
to the ACB
7 DDF (ulnar head)
8 Flex carpi ulnaris
9 Ext retinaculum
11 LCL
12 Accessory ulnar lig
13 Accessory IVCB lig
14 Accessory metacarpal lig
L
ACB

13. Lateral aspect
(joint capsule is removed)
L LCL
1/2/3/4 Dorsal intercarpal ligament
5 Prox lig ACB
6 Middle lig ACB
7/8 Distal lig ACB
9 Groove Lat ext T
10 Groove Ulnaris lat T
11 Interosseous lig

14. Lateral aspect
(deeper dissection)
1 Groove to the CDET
2 Ext dig lat T
3 Flex carpi ulnaris T
5 Accessory radial (cubital) lig
6 Groove to the ulnaris lateralis T
8 ICB
9 Dorsal intercarapal ligament (ICB and
UCB)
10 UCB
11 LCL
12 Accessory UCB lig
14 IIICB
15 Dorsal intercarpal lig (III and IVCB)
17 Accessory IVCB lig
18 Accessory metacarpal lig
19 Dorsal metacarpal lig
ACB
L
IV

15. Frontal section

16. 1 Medial Palmar Intercarp lig
2 Lat Palmar Intercarp lig
3 Radiocarpal lig
4 Lat collateral branch
5 Transverse intercarp lig
6 Palmar carpometacarpal lig

17. Medial aspect
(joint capsule is removed)
Ca ACB
M MCL
MC II IIMB
MC III IIIMB
C3 IIICB
Cr RCB
R Radius

18. Carpal Canal
• Palmar annular ligament /
Carpla flexor retinaculum
– Connective tissue
– Encloses:
• SDFT and DDFT
• FCRT
• Involved in the carpal sheath
• Nerves and blood vessels

19. Carpal Canal
• Palmar annular ligament / Carpla
flexor retinaculum
– Originates from the palmar border
of ACB and inserts medially at the
palmar aspect of the CB + MCL
• It it subdivided in several
compartments
– Proximal border: level of prox
margin of ACB
– Distal border: close to the head of
splint bones

20. Lateral View

21. Dorso-palmar View

22. DLPMO View

23. DMPLO View

24. Flexed Lateral View

25. DPDD View – Distal Radius

26. DPDD View – Prox Row

27. DPDD View – Distal Row

30. DMPLO

31. DMPLO

32. DLPMO

33. PMDLO

34. DLPMO

35. Lateral

36. Lateral

37. Cranio caudal