Navicular degeneration

Question 1

What is the navicular bone

Answer 1

distal sesamoidean bone

Question 2

What is the typical conformation of a horse with navicular degeneration

Answer 2

long toe low heel
broken back Hoof pastern axis

Question 3

how does a broken back HPA + collapsed heel lead to navicular degeneration?

Answer 3

increases pressure applied on navicular bone

Question 4

which ligament supports the navicular bone

Answer 4

distal sesamoidean ligaments (impar ligament)

Question 5

where does the impar ligament insert

Answer 5

proxiamally to the DDFT on P3

Question 6

True/false the impar ligament and suspensory ligament are involved in navicular degeneration

Answer 6

True

Question 7

List 4 changes that are seen in navicular degeneration

Answer 7

Focal loss of the medullary architecture
Fibrocartilagenous change of the flexor surface of the bone
Traumatic fibrillation of the deep digital flexor tendon
Enthesiophyte formation on the proximal and distal borders of the bone

Question 8

Outline the 2 possible causes of navicular degeneration?

Answer 8

Unknown but most likely biomechanical
Possibly some vascular component

Question 9

List 3 risk factors for navicular degeneration

Answer 9

genetic component
typically older horses >10 yr
foot conformation very important

Question 10

How to horses with navicular degernation typically presented

Answer 10

Insidious onset bilateral forelimb lameness- Initially intermittent and possible Change in performance
Sound in straight line but Lame on lunge
Rarely positive to hoof testers

Question 11

Describe how to diagnose navicular degeneration

Answer 11

PDNB- complete resolution- if bilateral lameness will switch to other leg
navicular bursae block- more specific

Question 12

why is navicular bursa block less commonly used than PDNB for navicular degeneration diagnostics even though it is more specific?

Answer 12

harder to do
needle goes through DDFT In one of the approaches
required radiographic guidance and contrast to confirm placement

Question 13

What is the main diagnostic imaging tool for navicular degeneration

Answer 13

radiographs

Question 14

List the radiographic views we need to take to diagnose navicular degeneration

Answer 14

LM
DoPr, PaDi 60 oblique
PaPr PaDi 45 oblique

Question 15

what changes would we see in a LM view of a horse with navicular degeneration

Answer 15

enthesiophyte –> spur like projection

Question 16

what changes would we see in a upright navicular of a horse with navicular degeneration

Answer 16

synovial invaginations = round areas of reduced density on the border
± cysts in the bone

Question 17

what do we need to do before radiographing the foot

Answer 17

fill up the frog (play dough)- if we don’t do this then will get air artefact which could be mistaken for fracture

Question 18

List 3 advantages of using MRI for navicular degeneration diagnosis

Answer 18

Diagnosis of multiple pathologies
Early diagnosis of bone pathology
shows soft tissue change

Question 19

What is a possible disadvantage for using MRI to diagnose navicular degeneration

Answer 19

cost
expernsive

Question 20

what is a STIR image

Answer 20

think it is like an MRI but only shows water -> will show bone oedema

Question 21

Describe how we manage navicular degeneration cases

Answer 21

via conservative management - no cure for it

Question 22

Describe conservative management of navicular degeneration

Answer 22

• analgesia: bute ± paracetamol
• corrective farriery (esp in horses with poor conformation)
• steroids into bursa or coffin joint
• biphosphonates (prevents bone resorption by osteoclasts)

Question 23

what may we do in terms of corrective farriery for navicular degeneration

Answer 23

wedges- reduce extension of DIP (if broken back)
rolled toe- eases break over
bar shoes

Question 24

what surgical treatment might we give for navic degeneration?

Answer 24

palmar digital neurectomy

Question 25

What is the main aim of doing palmar digital neurectomy

Answer 25

provide pain relief

Question 26

List 2 problems with doing palmar digital neurectomy

Answer 26

Nerve sensation will eventually restore
Complications include neuroma and catastrophic DDFT breakdown, pedal osteitis/foot penetrations