Metacarpal or metatarsal exostosis
Metacarpal or metatarsal exostosis (Splints) is a condition of young horses, most commonly affects the proximal medial aspect of the limb between the second and third metacarpal bones.
The Metacarpal or metatarsal exostosis condition is associated with training and subsequent injury between the small metacarpals/ metatarsal (MC/MT) bones and cannon bone, resulting in inflammation or tearing of the interosseus ligament.
Conformation abnormalities such as offset carpi, improper hoof care, and mineral imbalances may exacerbate the condition. The second and fourth MC/MT bones are commonly called splint bones.
Each is attached intimately to the respective third MC/MT bone by an interosseous ligament, thus splinting the large bone.
The splint bones articulate with the carpometacarpal joint or tarsometatarsal joint and are exposed to loads on weight-bearing.
The interosseus ligament consists of dense fibrous tissue that can tear with the strains applied during independent motion of the splint bones and the cannon bone.
Initially, inflammatory desmitis and periostitis develop. Subsequently, new bone is produced to fuse the splints to the cannon bone and stabilize the source of irritation.
Etiology
- Proliferation of fibrous tissue and osteoperostitis.
- External trauma
- Healing of transverse or longitudinal fracture
- Chronic inflammation of the periosteum – proliferative exostosis
- Excessive loading lead to tearing of interosseous ligament
- Conformation abnormality like offset carpi
- Improper shoeing and trimming
- External blows especially fourth metatarsal bone
- Imbalanced nutrition or over nutrition
- Deficiency in calcium and phosphorous
Clinical signs
- Most common in 2 year old horse but also seen in horses of 3 or 4 year old
- Lameness is most obvious in trot
- Heat, pain and swelling noticed in the affected limb
- Usually occur 3 inches below the carpus
- One large swelling or number of small enlargements may occur along the length of the splint bone
- Extensive new bone formation on a splint bone may also encroach on the suspensory ligament and cause chronic lameness unless it is removed.
- After the original inflammation subsides, the enlargements usually become smaller but firmer as a result of the ossification. The reduction in swelling is usually the result of resolution of fibrous tissue, rather than a decrease in size of the actual bone formation.
Diagnosis
- Clinical sign
- Radiography
- Ultrasonographic examination can demonstrate concomitant injury to the suspensory and possible ligament impingement.
- Nuclear scintigraphy
Treatment
- Anti-inflammatory agents and rest for acute phase
- Chronic splints warranted surgery
- Shock wave therapy
- Icing
- Surpass, DMSO/steroid sweats
- Acupuncture
- Massage
- Anti-inflammatory therapy along with application of hypothermia and pressure bandage reduce heat, pain and swelling associated with acute phase
- Confined to stall for 30 to 45 days
- Hand walking for 15 to 20 minutes twice a day once acute signs subsides
- Intralesional corticosteroids can reduce inflammation and may help prevent excessive bone growth
- Corticoid therapy accompanied by counter pressure bandage
- If the proliferative bone growth is excessive, surgery may be indicated
Prognosis
- Prognosis is good to excellent, except splints with large exostosis and encroaches the suspensory ligament and carpal joint
- Chronic recurring lameness resulted in those horses that are not rested enough
- Surgery may speed up the return to athletic performance and soundness and also improve the cosmetic blemish.