Splints primarily involve the interosseous ligament between the large (third) and small (second) metacarpal (less frequently the metatarsal) bones. The reaction is a periostitis with production of new bone (exostoses) along the involved splint bone. Trauma from concussion or injury, strain from excess training (especially in the immature horse), faulty conformation, imbalanced or overnutrition, or improper shoeing may be contributory factors.

Splints most commonly involve the medial rudimentary metacarpal bones. Lameness is seen only when splints are forming and is seen most frequently in young horses. Lameness is more pronounced after the horse has been worked. In the early stages, there is no visible enlargement, but deep palpation may reveal local painful subperiosteal swelling. In the later stages, a calcified growth appears. After ossification, lameness disappears, except in rare cases in which the growth encroaches on the suspensory ligament or carpometacarpal articulation. Radiography is necessary to differentiate splints from fractured splint bones.

Splints (interosseous desmitis)

Complete rest and anti-inflammatory therapy is indicated. Intralesional corticosteroids may reduce inflammation and prevent excessive bone growth. Their use should be accompanied by counterpressure bandaging. In Thoroughbreds, it has been traditional to point-fire a splint, the aim being to accelerate the ossification of the interosseous ligament; however, in most cases, irritant treatments are contraindicated. If the exostoses impinge against the suspensory ligament, surgical removal may be necessary.

Last full review/revision March 2012 by Stephen B. Adams, DVM, MS, DACVS; Andrew L. Crawford, BVetMed, CertES (Orth), MRCVS; James K. Belknap, DVM, PhD, DACVS; Jane C. Boswell, MA, VetMB, CertVA, CertES (Orth), DECVS, MRCVS; Peter Clegg, MA, Vet MB, PhD, CertEO, DECVS, MRCVS; Marcus J. Head, BVetMed, MRCVS; C. Wayne McIlwraith, BVSc, PhD, DSc, FRCVS, DACVS; James Schumacher, DVM, MS, DACVS, MRCVS; John Schumacher, DVM, MS, DACVS, MRCVS; Roger K. W. Smith, MA, VetMB, PhD, DEO, DECVS, MRCVS; Chris Whitton, BVSc, FACVSc, PhD; Jean-Marie Denoix, DVM, PhD, Agregé; Joerg A. Auer, DrMedVet, Dr h c, MS, DACVS, DECVS