Coffin OA Flashcards
What signalment is most common in OA in the DIP and PIP joints?
Progressive degenerative joint disease
- middle aged / older horses
Distal Interphalangeal (coffin) joint OA – ‘low ringbone’
* Common
* All types of horse
* Front feet»_space; hind
Proximal Interphalangeal (pastern) joint OA – ‘high ringbone’
* Uncommon
* Heavier breeds – cobs & hunters
* Hind feet»_space; front
What are predisposing factors for coffin OA?
- Genetic predisposition
- Work load - repetitive impacts
- Work type
- faster gait
- landing after jumps
- Work surface - hard v cushioned
- Hoof imbalance / conformation
- Usually LTLH with broken back HPA
- Nutrition in early life
- Previous injury
What history is associated with coffin OA?
- Low grade lameness – often bilateral forelimb lameness
- Often insidious onset, but can be sudden
- Reduced performance without obvious lameness
- Disease progresses sub clinically prior to development of clinical signs
- Lameness develops when ‘threshold’ of disease is reached
- Need to know horse’s work load / type recently and longer term
What are common findings during a clinical exam for coffin OA?
- Effusion in coffin joint
- palpate fluid 1cm proximal to coronary band on midline
- Careful attention to hoof balance and shoeing
- Broken back hoof pastern axis
- Long Toe Low Heel conformation
What findings are commonly associated with coffin OA during a dynamic exam?
- Usually sound at walk
- Mild lameness at straight trot - may be bilateral
- Lameness more obvious on lunge with lame limb to inside of circle (more weight)
- lame on LF on left rein and RF on right rein
- Worse on hard ground
- Usually moderate positive response to distal limb flexion
What regional anaesthesia is used to diagnose coffin OA?
- Palmar digital nerve block (wait 10-15 min)
- Distal Interphalangeal (coffin) joint block (wait 5 minutes - after 5 minutes the local will travel out of the joint and anaesthetise the whole foot)
What are you looking for when radiographing feet in coffin OA? What view is most helpful?
Latero-medial view
- extensor process of P3 should be smooth and rounded - would see prominent spike of bone protruding proximally
- evidence of peri-articular new bone formation at the capsular insertion onto P2
- osteophates on palmar aspect of condyles
- condyles are flatter rather than circular
- assess foot balance - broken back hoof pattern axis (pastern angle and pedal bone angle)
- angle at the bottom of the pedal bone compared to angle of the ground (should have 5 degree downward angle)
- oesteochondral fragmentation on dorsal aspect of P3
What would MRI and CT show in coffin OA?
- Will show degree of joint effusion & cartilage degeneration
- Allows diagnosis of additional pathology e.g. oedema in distal phalanx
What analgesia would you give in coffin OA? What side effects are associated?
Oral NSAIDs
* Phenylbutazone, Suxibuzone
* Effective
* Cheap and easy to give
* Given each day / when required
* Treats entire horse
* Systemic side effects:
* Gastric ulceration
* Right dorsal colitis
- Liver and kidney inflammation
Intra-articular corticosteroids
* Triamcinalone, Methylprednisolone
* Very potent
* Requires skills to administer
* Focussed to joint(s)
* Approximately 6m duration
* Rare but important side effects:
* Laminitis
* Joint sepsis
What medications can be injected into the OA articulartion?
Hyaluronic acid
Lubricant
Given in combination with corticosteroid in high motion joints
Polyacrylamide gel (Arthromid)
Hydrogel filler with lubricating and cushioning effect
Anti-inflammatories and promote cartilage growth (chrondrocytes)
* Chondrogenically primed stem cell allograft (Articell)
* Platelet Rich Plasma (PRP)
* Interleukin 1 receptor antagonist protein (IRAP)
* Bone Marrow Aspirate Concentrate (BMAC)
What are slow acting disease modifying OA agents? How do they work?
- Many exist
- Evidence lacking
- Oral joints supplements – glucosamine, chondroitin, hyaluronic acid…..
- Pentosan Polysulphate (Cartrophen) - one that has evidence
- Accelerates chondrocyte and synoviocyte metabolism
- Stimulates proteoglycan synthesis
- Reduces MMP production
- → anti-inflammatory and cartilage repair effects
How is farriery used to help with coffin OA?
Shorten toe
Rasp back
Use rolled to shoe
Support heels
Bar shoe (straight)
Sometimes heel elevation
Add cushioning
- Rubber pad or sole packing under shoe
What surgical treatment is available for coffin OA?
Arthroscopy
If osteochondral fragment present
To debride necrotic cartilage
Dorsal aspect of joint only
Palmar digital neurectomy
Section of nerves removed
Long term desensitisation of the foot
Only if other therapies are unsuccessful
What future management is to be promoted to owners in coffin OA?
- OA is managed rather than cured
- Horses can continue to have happy active lives, but expectations should be reduced
- Workload must be managed
- Be careful what surface the horse works on
- Veterinary treatment and corrective farriery likely to be ongoing.
