Exostoses of the Metatarsal Bones in Horses

Exostoses of the metatarsal bones (splints) are common and may or may not be associated with lameness. Splint exostoses may be caused by direct trauma or instability between metatarsal bones. Large exostoses on the proximal lateral aspect of the second or fourth metatarsal bones are common and usually asymptomatic. Axially located splint exostoses on the proximal end of the second or fourth exostoses may impinge on the proximal end of the suspensory ligament or on the lateral and medial plantar metatarsal nerves and be associated with lameness.

Lameness is usually mild and can be alleviated by infiltration of local anesthetic solution around the exostosis or by perineural analgesia of the lateral and medial plantar metatarsal and lateral and medial plantar nerves.

Management of horses with symptomatic splint exostoses includes local cold therapy (cold hosing, icing, etc), bandaging, and administration of NSAIDs. Infiltration of corticosteroids around the exostosis may be beneficial in some cases. Surgical excision of persistently painful exostoses by periostectomy, ostectomy of exostosis without removing the parent splint bone, adhesiolysis, and fasciotomy can be performed successfully if exostoses involve the axial aspect and encroach on or are adhered to the suspensory ligament.