Texas Equine Veterinary Association

www.teva-online.org • Page 9 ROBERT J. HUNT, dVM, MS, daCVS Haygard Equine Medical Institute m a n a g e m e n t O F c l u b f o o t I N h o r S e S Development of clubfoot, or distal interphalangeal (corono-pedal) flexural deformity, may occur at any stage of life and may be congenital or acquired. In many instances there appears to be a genetic basis. The etiology, clinical manifestations, management, and expectations differ somewhat between age groups. Treatment and long-term management vary depending on the age of onset, underlying etiology, severity, secondary complications and client expectations. The prognosis for long-term soundness is generally favorable with appropriate management, but may be adversely affected by the severity of the deformity and/or the presence of secondary complications. The clinical presentation in the horse can range from a mildly upright and small foot, to one which is buckled forward with an angle greater than 90° at the distal interphalangeal joint, or may have advanced pedal osteitis and hoof wall deterioration. A classification scheme has been developed to systematically designate four grades of clubfeet in horses. A Grade 1 clubfoot has a hoof axis 3 to 5° greater than the contralateral foot and displays fullness at the coronary band, but is mild enough that the hoof-pastern axis is aligned. A Grade 2 clubfoot is slightly more severe, with a hoof axis measuring 5 to 8° greater than the contralateral foot. In a Grade 2 foot, the hoof-pastern axis is steep and slightly broken-forward. Growth rings of the hoof are wider at the heel than at the toe, and after trimming excess hoof wall from the heel, the heel may not touch the ground. A Grade 3 clubfoot is a more severe deformity, which has a broken-forward hoof-pastern axis and mild concavity present in the dorsal hoof wall. The growth rings are twice as wide at the heels as those at the toe, and radiographically there is demineralization and lipping along the apex of the distal phalanx. A Grade 4 clubfoot is the most severe classification and has a hoof angle of greater than or equal to 80°, with a severely broken-forward hoof-astern axis. A Grade 4 clubfoot has a markedly concave dorsal hoof wall, and the coronary band height at the heel is equal to that at the toe. Radiographic changes include rounding of the distal phalanx due to extensive demineralization, and rotation may be present. Despite the degree of deformity or age category at presentation, the most widely accepted explanation of the underlying mechanical cause is shortening of the musculotendinous unit of the deep digital flexor tendon relative to the bony column and secondary contraction of the joint capsule and surrounding soft tissues. The result is hyperflexion of the distal interphalangeal joint and an inability to fully extend the distal interphalangeal joint because of the rigid tension band formed by the accessory ligament of the deep digital flexor tendon. The initiating event behind this musculotendinous shortening is often undetermined, and may be related to lameness, nutrition, or genetic predisposition. Although the clinical presentation, causal factors, complications, treatment and long-term management of the clubfoot horse varies with the age of the horse at presentation, some basic principles may be applied to management of all cases. Client communication and determination of client expectations is critical to achieving a satisfactory outcome; the more severe the deformity, the worse the prognosis. Deformities, which have greater than a 90° hoof angle and advanced pedal osteitis, rarely become sound athletes. Additionally, the potential genetic association of clubfoot in some breeds should be discussed with owners prior to initiating treatment. Congenital distal interphalangeal flexural deformity is recognized shortly after birth and ranges in severity from mild to severely contracted and unable to ambulate. Two distinct variations of clubfeet or DIP flexural deformity occur in neonates. The deformity may occur as an isolated unilateral deformity; however,

• Cover