Equine Carpus Anatomy

Carpal Anatomy

Radiology Rounds

December 15th, 2014

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

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

Anatomy

• Bones

– Radius

– Proximal row

• RCB, ICB, UCB, ACB

– Distal row

• IICB, IIICB, IVCB, occasionally ICB and rarely VCB

– Metacarpal

• IIMCB, IIIMCB, IVMCB

Anatomy

• Soft-tissues:

– Intercarpal ligaments

– Collateral ligaments

– Fibrous joint capsule

– Palmar carpal ligament

Anatomy

• Dorsal:

– Extensor carpi radialis (sheath)

• Dorsolateral:

– Common digital extensor tendon (sheath)

• Extensor retinaculum – distal radius at physealscar

– stabilize ECR and CDET

Tendon sheaths

j Flex carpi radialis (resected)k Ext carpi radialism CDE (humeral head)n CDE (radial head)o DDFp Lat dig flexorq Ulnaris lateralisr Flexor carpi ulnaris (resected)s Ext carpi obliquus

All tendons passing over carpus have sheath, except:• Short tendon of Ulnaris

lateralis• Flexor carpi ulnaris

Dorsal aspect

1 Radius

2 ECRT

3 Long dig abductor T

4 CDET

5 Extensor retinaculum

7 Lat digital extensor T

L

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 ligamentL

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 intercarpallig)

6 IICB and IIIMB

7 IIICB and IIIMB

8 Ulnar and III and IVCB (lateral palmar intercarapal lig)

9 Short MCL

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

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 ligL

ACB

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

Lateral aspect (deeper dissection)

1 Groove to the CDET2 Ext dig lat T3 Flex carpi ulnaris T5 Accessory radial (cubital) lig6 Groove to the ulnaris lateralis T8 ICB9 Dorsal intercarapal ligament (ICB and UCB)10 UCB11 LCL12 Accessory UCB lig14 IIICB15 Dorsal intercarpal lig (III and IVCB)17 Accessory IVCB lig18 Accessory metacarpal lig19 Dorsal metacarpal lig

ACB

L

IV

Frontal section

1 Medial Palmar Intercarp lig2 Lat Palmar Intercarp lig3 Radiocarpal lig4 Lat collateral branch5 Transverse intercarp lig6 Palmar carpometacarpal lig

Medial aspect (joint capsule is removed)

Ca ACB

M MCL

MC II IIMB

MC III IIIMB

C3 IIICB

Cr RCBR Radius

Carpal Canal

• Palmar annular ligament / Carpla flexor retinaculum

– Connective tissue

– Encloses:

• SDFT and DDFT

• FCRT

• Involved in the carpal sheath

• Nerves and blood vessels

Carpal Canal

• Palmar annular ligament / Carplaflexor 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 proxmargin of ACB

– Distal border: close to the head of splint bones

Lateral View

Dorso-palmar View

DLPMO View

DMPLO View

Flexed Lateral View

DPDD View – Distal Radius

DPDD View – Prox Row

DPDD View – Distal Row

DMPLO

DMPLO

DLPMO

PMDLO

DLPMO

Lateral

Lateral

Cranio caudal