26.5.4: Osteoarthritis of the coffin joint Flashcards
Signalment for coffin joint osteoarthritis
- Progressive degenerative joint disease so seen in middle to older horses
- Common!
- Coffin joint OA seen in all types of horses
- More commonly affects front feet than hind
What is another name for the distal interphalangeal joint?
Coffin joint
What is another name for the coffin joint?
Distal interphalangeal joint
What is another name for the proximal interphalangeal joint?
Pastern joint
What is another name for the pastern joint?
Proximal interphalangeal joint
What is meant by ‘high ringbone’ vs ‘low ringbone’?
High ringbone = proximal interphalangeal joint osteoarthritis.
Low ringbone = distal interphalangeal joint osteoarthritis.
Signalment for proximal interphalangeal joint osteoarthritis?
- Uncommon
- Seen in heavier breeds: cobs, hunters
- Hind feet more commonly affected than front
Predisposing factors to coffin joint OA
History associated with coffin joint OA
- Low grade lameness - often bilateral forelimb lameness
- Often insidious onset but can be sudden
- Reduced performance without obvious lameness
- Disease progresses subclinically prior to the development of clinical signs (lameness develops when “threshold” of the disease is reached
- Need to know the horse’s workload, both recently and longer term
Clinical exam findings in the horse with coffin joint OA
- Effusion in the coffin joint -> palpate fluid 1cm proximal to the coronary band on the midline
- Careful attention to hoof balance and shoeing: broken back hoof pastern axis; long toe low heel conformation
Dynamic exam findings in the horse with coffin joint OA
- Usually sound at walk
- Mild lameness at straight trot -> may be bilateral
- Lameness more obvious on lunge with lame limb to inside of circle (i.e. LF lameness on left rein)
- Worse on hard ground
- Usually moderate positive response to distal limb flexion
Which nerve block is shown here and how long will it take to work?
Which block is shown here and how long will it take to work?
Which nerve blocks might you use to determine if a horse has coffin joint OA and what response would you expect to each of them?
- Partial improvement with palmar digital nerve block. May completely block if there is no pathology on the dorsal surface of the joint.
- Block completely to abaxial sesamoid nerve block
- Block completely to coffin joint block
Next step: radiograph.
Which radiographic view is shown here and what features of coffin joint OA can you see?
- Lateromedial view
- Green arrows - sharp spur development of the short pastern and pedal bone
- Blue arrow - irregular, lucent modelling of the dorsal aspect of the short pastern bone at the attachment site of the joint capsule
- There is also foot imbalance to correct here
What pathology can be seen here?
Coffin joint OA
* Irregular new bone formation on the dorsal surface of P3
* Possible increased radiopacity palmar and distal to navicular bone - may indicate joint effusion
Why might MRI / CT be of benefit in a case of coffin OA?
- MRI / CT not always required to achieve diagnosis
- Will show degree of joint effusion and cartilage degeneration
- Allows diagnosis of additional pathology e.g. oedema in the distal phalanx
What options are there for analgesia of coffin joint OA? What are the pros and cons of each?
What options for intra-articular medications are there, aside from corticosteroids?
- Hyaluronic acid - lubricant, given with corticosteroids in high motion
- Polyacrylamide gel (Arthromid) - hydrogel filler with cushioning and lubricating effect
- Stem cell allograft
- Platelet rich plasma
- Interleukin 1 receptor antagonist (IRAP)
- Bone marrow aspirate concentrate (BMAC)
What are SADMOD?
Slow Acting Disease Modifying Osteoarthritic Agents
* Many exist; evidence lacking
* e.g. oral joint supplements
* e.g. Pentosan polysulphate (Cartrophen)
What are the benefits of Cartrophen for coffin joint OA?
Cartrophen = pentosan polysulphate
* Accelerate chondrocyte and synoviocyte metabolism
* Stimulates proteoglycan synthesis
* Reduces MMP production
* Overall: anti-inflammatory and cartilage repair effects
What corrective farriery would be suitable for horses with coffin joint OA?
Surgical treatment options for coffin joint OA
What should you advise the owner about long-term management of coffin joint OA?
- OA is managed rather than cured
- Horses can continue to have happy active lives, but expectation should be reduced
- Workload must be managed
- Be careful what surface the horse works on
- Veterinary treatment and corrective farriery are likely to be ongoing
