P3 and navicular fractures

Question 1

What are the 3 main causes of navicular and P3 fractures

Answer 1

acute onset trauma
developmental / osteochondral fragments
repetitive wear and tear/ chronic disease

Question 2

describe the clinical signs of navicular/ P3 fractures

Answer 2

because enclosed within hoof capsule- often minimal displacement - so hard to identify on exam but important
Careful palpation of the hoof and pastern region for heat, pain and swelling (including synovial effusions)
Use of hoof testers to identify site of pain

Question 3

what signs are seen with small extra articular fragments of navicular/ P3 fractures

Answer 3

low grade lameness with minimal localising signs

Question 4

if complete/ significant navicular/ P3 fractures what do we see

Answer 4

acute onset, severe lameness with localising signs (bounding digital pulses, heat in hoof, positive response to hoof testers)

Question 5

If articular fracture of navicular/ P3 what do we see

Answer 5

Distal interphalangeal joint effusion (pedal bone and navicular bone)

Question 6

If there is tendon involvement with navicular/ P3 fracture what do we see

Answer 6

digital flexor tendon sheath effusion (navicular bone)

Question 7

Describe how to diagnose Navicular/ P3 fracture

Answer 7

radiography
MRI
CT
gamma scintigraphy

Question 8

if see acute severe lameness with marked inflammation or effusion what should you do

Answer 8

This is a flag for an acute fracture and would be imaged first and not blocked.

Question 9

List 2 potential problems with radiography to diagnose navicular/ P3 fractures

Answer 9

The hoof structure holds the bones together so fractures may not be visible initially, until some bone resorption has occurred (7-10 days)

Some fractures only heal with a fibrous union (fracture line remains on radiographs, but are stable)

Question 10

List 4 possible causes of fragment at the site of the extensor process on P3

Answer 10

Recent fracture
Previous fracture, now healed and stabilised
Separate centre of ossification
Dystrophic mineralisation in the extensor tendon

Question 11

List the 5 views that make up s foot radiographic series

Answer 11

1. Lateromedial
2. Dorsopalmar
3. Dorsoproximal Palmarodistal 60o oblique centered on pedal bone (upright pedal)
4. Dorsoproximal Palmarodistal 60o oblique centered on navicular bone (upright navicular)
5. Palmaroproximal Palmarodistal 45o oblique (flexor navicular)

Of both feet!

Question 12

what do you need to do before taking a Upright Pedal/D60Pr-PaDi oblique radiograph

Answer 12

pack foot with play doh to avoid air aretfact

Question 13

Why do P3 or navicular fractures often don’t displace

Answer 13

due to them being enclosed in the hoof capsule

Question 14

if we don’t see a fracture on radiography, does this mean there isn’t one

Answer 14

No- sometimes fractures occur but are held together well by the hoof

Question 15

if we do see a fracture on radiography does this mean it is significant

Answer 15

no- sometimes when fractures heal, they heal with a fibrous union

Question 16

how can we test if a bone fragment or fracture is clinically significant

Answer 16

flexion tests or synoviocentesis