26.5.4: Cases that block to PDBN with no localising signs Flashcards
What signs may help you localise the cause of lameness to the feet?
- Digital pulses
- Swelling
- Response to hoof testers
What is being palpated here?
This is the site of a DIP effusion (if present, will feel squishy)
What structures does the palmar digital nerve block always numb?
- Sole
- Heel bulbs
- Palmar and distal P3
- Navicular bone
- Navicular bursa
- Distal DDFT
- Impar ligament
- Palmar DIP joint
What structures does the palmar digital nerve block variably numb?
- Dorsal P3
- Dorsal laminae
- Dorsal DIP joint
- Collateral ligaments of the coffin joint
- Distal P2
- Collateral cartilages
Roughly how much of which local anaesthetic would you inject in order to achieve a palmar digital nerve block?
2ml mepivacaine
Differentials for when the lame horse which resolves when foot blocked with no localising signs
- DIP joint osteoarthritis (common)
- Navicular bone degeneration (lytic changes are painful)
- Navicular bursitis
- Fracture of P3 or navicular bone (uncommon)
- DDF tendonitis
- Impar ligament desmitis (strain)
- Hoof imbalance
- Subchondral cystic lesion
- Pedal osteitis (non-septic; if septic there would be localising signs)
- Mineralisation of the lateral cartilage (“sidebone)
Aetiology of deep digital flexor tendonitis
- Longitudinal splits in the DDFT behind the navicular bone
- Insertional desmopathies where the DDFT attaches to the bottom of P3
Which radiographs will you take when a lame horse becomes sound when the foot is blocked?
Need to take a foot series:
1. Lateromedial
2. Standing dorsopalmar/ dorsoplantar
3. Dorso 60 degree proximal palmarodistal oblique centres on the pedal bone (upright pedal)
4. Dorso 60 degree proximal palmarodistal oblique centred on the navicular bone (upright navicular)
5. Palmaro 45 degree proximal palmaro distal oblique of the navicular bone (flexor navicular)
How useful is ultrasonography for assessing structures in the foot? What can you see?
- Only moderately useful; limited access to soft tissue structure
Can see
✅ Proximal end of coffin joint collateral ligaments
✅ DDFT between heel bulbs
✅ Insertion of DDFT through frog
- Large hypoechoic area in the proximal end of collateral ligaments of coffin joint
- Diagnostic for desmitis
What is the preferred imaging modality for structures inside the hoof and what are the pros and cons?
MRI
✅ Excellent definition of bone, soft tissues, cartilage and fluid
✅ Gold standard
✅ Can be done under standing sedation
❌ Expensive (~£1500) and time consuming
When would you use CT?
- Used when MRI not available
- Useful for fracture conformation assessments
✅ Excellent bone definition
😔 Can only see soft tissues and cartilage when IV contrast added
1
2
1
Normal
2
Broken forward (a.k.a. club foot)
3
Broken back (long toe, low heel)
1
2
3
What are these images showing?
Load bearing
What are these images showing and what can be a problem?
- Wrong angle with make the DDFT longer
- -> more pressure
- -> more pressure on navicular bone
What pathology is shown here and how has it been corrected?
- Contracture of DIP (foal)
- Heels have been shortened and toe extension has been added
What lesion is shown here and what clinical signs would you expect?
Bone cyst in the navicular bone
* Would cause significant lameness
Here is one on MRI
What is this and what could have caused it?
Subchondral cystic lesion a.k.a. bone cyst
* Can be seen as part of osteochondrosis (perhaps rare to see this in the foot though)
* Can happen due to trauma
What is shown here and what could have caused it?
Pedal osteitis (not the same as septic pedal osteitis)
* Irregular lysis of solar margin of distal phalanx
* Often seen in thoroughbreds
* Thin sole + concussive trauma
* Can also be seen with laminitis (chronic pressure / inflammation)
What is this and what could have caused it?
Normal finding seen in some horses
* Compare to the other foot if not sure
What finding is shown here and what clinical signs would you expect?
Mineralisation of lateral cartilage (sidebone)
* May be incidental finding
* Common in front feet of older, heavier horses
* May cause lameness during formation or if traumatised / fractured
