Osteoarthritis of the distal interphalangeal joint Flashcards
Signalment
▪ Progressive degenerative joint disease
– usually middle aged / older horses
Signalment of DIP (coffin) joint OA
- Common
- All types of horse
- Front feet»_space; hind
Another name for coffin joint OA
- ‘low ringbone’
Signalment of PIP (pastern) joint OA
- Uncommon
- Heavier breeds – cobs & hunters
- Hind feet»_space; front
Another name for pastern joint OA
- ‘high ringbone’
Predisposing Factors
▪ Genetic predisposition
▪ Concussion:
–Work load
-> repetitive impacts
–Work type
-> faster gait
-> landing after jumps
–Work surface
-> hard v cushioned
-> hard is worse as more trauma to the feet
▪ Hoof imbalance / conformation
– Usually LTLH (long toe low heel) with broken back HPA
– Allows abnormal forces to be transmitted through the horses foot and into the joint surface
▪ Nutrition in early life
– May play an important part in terms of overall cartilage health and therefore development of OA
▪Previous injury
History
▪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
Clinical exam findings
▪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
Dynamic exam findings
▪ Usually sound at walk
▪ Mild lameness at straight trot
– may be bilateral
-> short shuffly gait, 1 leg can be worse than the other
▪ Lameness more obvious on lunge with lame limb to inside of circle
– lame on LF on left rein and RF on right rein
– because the inside leg bears more weight, so has more pressure going down through it
– greater forces going through the foot = more pain
▪ Worse on hard ground due to increased concussion
▪ Usually moderate positive response to distal limb flexion
Regional Anaesthesia
Palmar digital nerve block
- 10-15mins
Distal Interphalangeal (coffin) joint block
- 5 minutes
– Don’t wait longer than 5 minutes as otherwise the rest of the foot will have been anaesthetised (i.e. not diagnostic for DIP OA)
Diagnosis by Radiography – latero-medial view potential findings
Periosteal new bone growth
- where the joint capsule attaches to
- so get new bone formation at the capsular insertion onto P2
Can see osteophytes on the back of the leg
- on the palmar aspect of the condyles
Condyles have lost their roundness.
Extensor process of P3 - the dorsoproximal aspect of P3 should be smooth and rounded, but may see a large prominent spike of bone (osteophyte) sat within the coffin joint protruding proximally
Can also assess foot balance on lateral radiograph
- Broken back HPA?
Can also look at the angle of the ground
- should have slight downward 5 degree downward angle
Can see osteochondral fragmentation which happens at the extensor process of P3.
Advanced Imaging – MRI and CT
▪ Not always required to achieve diagnosis
▪ Will show degree of joint effusion & cartilage degeneration
▪ Allows diagnosis of additional pathology e.g. oedema in distal phalanx
Analgesic tx options
- Oral NSAIDs
- Intra-articular corticosteroids
Oral NSAIDs
▪Phenylbutazone, Suxibuzone
▪ Effective
▪ Cheap and easy to give
▪ Given each day / when required
▪ Treats entire horse
– Good if multiple joints affected
▪ 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
– But depends on severity of dz and horse workload
▪ Rare but important side effects:
- Laminitis
- Joint sepsis
