Introduction to cases that block to the foot but with no localising signs

Question 1

Where in the horse is the most common site of lameness?

Answer 1

• the feet

Question 2

Is hind or front feet lameness more common?

Answer 2

• front

Question 3

History

Answer 3

Lameness may be:
- mild and intermittent or more severe
- Acute or chronic

1 or more feet
- often bilateral in front limbs

Affects all types and uses of horse

Commonly mild-moderate lameness in both front feet

Question 4

Static Examination - observation

Answer 4

Often there are few localising signs

Foot conformation:
- Size, shape and symmetry of feet
– e.g. is the size of the foot appropriate for the size of the horse?
- Contraction of heel bulbs
- Hoof balance

Unshod or shod
- Type and fit of shoes
- Abnormal wear to shoe

Question 5

Static Exam - palpation

Answer 5

The hoof removes our ability to detect signs of inflammation
- Often no heat, pain or swelling
- Can palpate effusion in the distal interphalangeal joint

Response to hoof testers
- Usually none

Question 6

Dynamic Examination

Answer 6

Walk
- obvious lameness
- how the foot land → should be flat not heel / toe / side first

Straight Trot
- most useful gait for assessing lameness

Trot on lunge
- both reins, hard and soft surfaces
- lameness usually worse with on inside and on hard

Canter

Can do a ridden assessment

Can do a flexion test - will be worse when the distal limb is flexed

Question 7

What does the palmar digital nerve block always numb?

Answer 7

• Sole
• Heel bulbs
• Palmar & distal P3
• Navicular bone
• Navicular bursa
• Distal DDFT
• Impar ligament
• Palmar DIP joint

Question 8

What does the palmar digital nerve block variably numb?

Answer 8

• Dorsal P3
• Dorsal laminae
• Dorsal DIP joint
• Collateral ligaments of coffin joint
• Distal P2
• Collateral cartilages

Question 9

How to test that a palmar digital nerve block has worked

Answer 9

• poke the heel bulbs with a pen

Question 10

Differential diagnosis – Horse where lameness blocks to the foot with no localising signs

Answer 10

• DIP joint OA
• Navicular bone degeneration
• Navicular bursitis
• Fracture of P3 or navicular bone
• DDF Tendonitis
• Impar ligament desmitis
• DIP collateral ligament desmitis
• Hoof imbalance
• Subchondral cystic lesion
• Pedal osteitis
• Mineralisation of lateral cartilage
  – ‘sidebone’

Question 11

What does navicular bursitis usually go hand in hand with?

Answer 11

• navicular bone degeneration
• DDFT tendonitis

Question 12

Diagnostic Imaging - Radiography uses

Answer 12

• Usual first line imaging
• Bones & joints
• Hoof balance

Question 13

Diagnostic Imaging - Radiography views

Answer 13

• Latero-medial
• Standing dorsopalmar
• Dorsal 60°proximal-palmar distal oblique of pedal bone (upright pedal)
• Dorsal 60°proximal-palmar distal oblique of navicular bone (upright navicular)
• Palmar 45° proximal-palmar distal oblique of navicular bone (flexor navicular)

Question 14

Diagnostic Imaging - Ultrasonography uses

Answer 14

• Limited access to soft tissue structure
• Only moderately useful
• Proximal end of coffin joint collateral ligaments
• DDFT between heel bulbs
• Insertion of DDFT through frog

Question 15

Diagnostic Imaging - MRI uses

Answer 15

• Excellent definition of bone, soft tissues, cartilage and fluid
• Gold standard
• Usually done standing under sedation
• Expensive and time consuming

Question 16

Diagnostic imaging - CT uses

Answer 16

• Excellent bone definition
• Soft tissues & cartilage when IV contrast added
• Usually only when MRI not available
• 3D images → fracture conformation

Question 17

Hoof balance – Hoof Pastern Axis

Answer 17

Normal
= straight line from P1-P3

Broken forward
- ‘club foot’
- toe of P3 below straight line from P1-P2
- angle at top of coronary band has gone forwards

Broken back
= ‘long toe, low heel’
- toe of P3 above straight line from P1-P2
- angle at top of coronary band has gone backwards
- j shaped

Question 18

Hoof balance – Load bearing

Answer 18

Normal:
- 60:40% weight bearing front:back of hoof

Broken back:
- ~70:30% weight bearing front:back of hoof
- more crushing forces put through the navicular bone

Question 19

Hoof balance – Angle of distal phalanx sole

Answer 19

Normal:
- down angled at 5°

Broken back:
- parallel or reverse rotated (pedal bone pointing upwards)

Question 20

Hoof balance - lateromedial

Answer 20

Line down long axis of limb : line of coronary band to floor should be 90%

Question 21

Hoof balance - Management

Answer 21

Work closely with farrier

Foals
- lots of alteration possible

Adults
- limited alteration possible
- can create additional lameness
- takes several shoeings
- foot must land flat on hard surface
– stretching the DDFT
– painful so need analgesia

Take follow up radiographs

Question 22

Subchondral cystic lesion

Answer 22

• Can happen as part of OA complex or due to trauma (part of OA)
• Rare
• Can happen in the foot

Question 23

Pedal osteitis

Answer 23

• Irregular lysis of solar margin of distal phalanx
• Occurs following chronic pressure or inflammation within hoof
  – e.g. repeated concussion / chronic laminitis
• Differentiate from ‘crena’
  – normal symmetrical indentation at toe
  – radiograph other hoof to determine whether normal
• Infectious = septic pedal osteitis
• Inflamed bone crumbles away
• Horses with thin soles are over-represented for this injury
  – Less common in those with big strong feet

Question 24

Why is it called pedal osteitis not osteomyelitis?

Answer 24

• there is no medulla in the pedal bone

Question 25

Mineralisation of Lateral Cartilage - Sidebone

Answer 25

• Common incidental finding
• Front feet of older, heavier horses
• Can cause lameness:
  – During formation
  – If traumatised / fractured