Introduction to cases that block to the foot but with no localising signs Flashcards
Where in the horse is the most common site of lameness?
- the feet
Is hind or front feet lameness more common?
- front
History
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
Static Examination - observation
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
Static Exam - palpation
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
Dynamic Examination
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
What does the palmar digital nerve block always numb?
- Sole
- Heel bulbs
- Palmar & distal P3
- Navicular bone
- Navicular bursa
- Distal DDFT
- Impar ligament
- Palmar DIP joint
What does the palmar digital nerve block variably numb?
- Dorsal P3
- Dorsal laminae
- Dorsal DIP joint
- Collateral ligaments of coffin joint
- Distal P2
- Collateral cartilages
How to test that a palmar digital nerve block has worked
- poke the heel bulbs with a pen
Differential diagnosis – Horse where lameness blocks to the foot with no localising signs
- 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’
What does navicular bursitis usually go hand in hand with?
- navicular bone degeneration
- DDFT tendonitis
Diagnostic Imaging - Radiography uses
- Usual first line imaging
- Bones & joints
- Hoof balance
Diagnostic Imaging - Radiography views
- 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)
Diagnostic Imaging - Ultrasonography uses
- 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
Diagnostic Imaging - MRI uses
- Excellent definition of bone, soft tissues, cartilage and fluid
- Gold standard
- Usually done standing under sedation
- Expensive and time consuming
Diagnostic imaging - CT uses
- Excellent bone definition
- Soft tissues & cartilage when IV contrast added
- Usually only when MRI not available
- 3D images → fracture conformation
Hoof balance – Hoof Pastern Axis
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
Hoof balance – Load bearing
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
Hoof balance – Angle of distal phalanx sole
Normal:
- down angled at 5°
Broken back:
- parallel or reverse rotated (pedal bone pointing upwards)
Hoof balance - lateromedial
Line down long axis of limb : line of coronary band to floor should be 90%
Hoof balance - Management
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
Subchondral cystic lesion
- Can happen as part of OA complex or due to trauma (part of OA)
- Rare
- Can happen in the foot
Pedal osteitis
- 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
Why is it called pedal osteitis not osteomyelitis?
- there is no medulla in the pedal bone
