Musculoskeletal: flexural deformity

p equis

Contributor(s):

Steve Adair

Helen Herinckx

Chris Whitton

Laura Quiney

Synonym(s): Contracted tendon

Introduction

Abnormal angular deviation of the limb in the sagittal plane, usually abnormal flexion of one or more joints, and less commonly hyperextension.
Cause: congenital (multifactorial) or acquired (relative shortening of the musculotendinous unit).
Signs: hyperflexion of joint(s), also includes flexor tendon flaccidity → hyperextension.
Most commonly affects:
- Distal interphalangeal joint (flexural deformity) DIP joint: flexural deformity.
- Metacarpophalangeal/metatarsophalangeal joint (flexural deformity) MCP / MTP joint: flexural deformity.
- Carpal (flexural deformity) .
- Digital hyperextension Foot: flexural deformity - hyperextension.
Diagnosis: physical examination +/- radiography, ultrasonography, serology.
Treatment: conservative, medical, surgery, farriery.
Prognosis: good to poor depending on degree of abnormality, anatomic location of flexural deformity and response to treatment.

Print off the Owner factsheet on Flexural limb deformities and Leg splinting to give to your clients.

Often unknown/not understood, probably multifactorial.
Genetic factors.
Ingestion of locoweed, Sudan grass, sweet pea by the mare during gestation.
Equine Influenza (exposure to mare) Equine influenza.
Equine goiter.
Prematurity/dysmaturity.
Arthrogryposis (deformity of multiple limbs and the head and neck).
Uterine malposition has been proposed but is unproven.
Possibly defects in elastic or collagen formation (sweet pea ingestion by the mare).

Developmental orthopedic disease.
Mismatch of the relative lengths of the musculotendinous and osseous units:
- Rapid growth +/- over-nutrition of rapidly growing animals – bone grown more quickly than the soft tissues elongate.
Lameness, ie pain – contraction of the muscular portion of the musculotendinous unit.
Treatment of flexural deformity, eg limb casting, oxytetracycline administration may → hyperextension.

‘Contracted tendon’ is a misnomer as true contracture is unlikely to be the cause of most flexural limb deformities.
Rapid growth: during periods of rapid long bone lengthening, passive elongation of the tendons may be limited, thereby a discrepancy develops between the musculotendinous and osseous units.
Pain causing altered weight-bearing may also reduce passive elongation of the tendons.