Horse, Friberger Female 8 years of age Very long history of lameness front right, localised from the private vet in the PIP joint. At clinical examination, the lameness was graded 2/5. Radiographs of the right front PIP joint were taken. Radiographic examination Radiographs of the distal phalanges front right: Dorsopalmar, mediolateral, dorsolateral-palmaromedial oblique and dorsomedial-palmarolateral oblique view. Radiographic findings
- There is severe periarticular new bone proliferation on the PIP joint, solid and quite irregular defined, with an active appearance.
- There is an additional very large (approximately 6mm in diameter) smooth defined mineral opacity dorso medial in the area of the PIP joint, most likely separated (arrow).
- The bone proliferation is extending up to the middiaphysis of P1, mainly dorsally and with a very pronounced extension medially.
- The joint space is mild asymmetrical and minimally narrowed medially.
Close up of the DP view showing the intrarticular chip. Radiographic diagnosis
- Severe osteoarthritis PIP front right, with suspicious of intraarticular chip.
- Severe exostosis on P1 compatible with trauma, entesiophyte formation.
- Considering the severe findings, the horse underwent to an arthrodesis.
- Radiographs 4 weeks post OP were taken.
Radiographic examination
- 9 days after the removal of the cast (5 weeks post OP), the horse was presented for increased lamness and reduced weight bearing on the limb.
- Radiographs were repeated.
DP and LM view post arthrodesis PIP joint Radiographic examination and findings DP and LM view 5 weeks post arthrodesis PIP joint
- The most distal screw of the plate is broken in its dorsal third. There is a minimal dislocation and gap formation (close up to the right with arrow).
- There is a progressive periarticual new bone formation on the PIP joint, with partial loss of definition of the joint space.
Comment
- A new cast was applied for the following 6 weeks and the horse was rested.
- The radiographic diagnosis includes early but progressive anchylosis of the PIP joint front right with partial implant failure.
- The PIP joint is a low motion/highload joint. The term ‚high ringbone‘ is often used synonymously with OA of the PIP joint. Ringbone has also been classified as articular (involving the joint surface) or periariticular (involving the structures at the perimeter of the joint and the adjacent phalanges).
- The most common cause of PIP joint OA is chronic overuse or repetitive trauma.
- Secondary OA from P2 fractures (particularly palmar/plantar eminence) or OC lesion can occur.
- The most common radiographic findings in horses with chronic OA of the PIP joint are:
- Joint space narrowing or collapse
- Ostephyte formation
- Subchondral bone sclerosis
- Periosteal/periarticular bony proliferation
- Deformity/collapse of the joint space.
- Subchondral bone lysis, subchondral cystic lesions and chronic eminence fractures of P2 have also been reported.
