Introduction

• Abnormal development of humeral condyle that does not fully ossify and has a cartilaginous plane separating medial and lateral aspects.
• Cartilaginous plane predisposes dogs to humeral condylar fracture occurring during normal activity.
• Disease appears to have a genetic component with a recessive mode of inheritance.
• Pathogenic mechanism of disease unknown but presence of disease may be associated with presence of fragmentation of medial coronoid process, a form of elbow dysplasia.
• Humeral intracondylar fissure develops in older dogs who had no signs of IOHC, ie a de novo fissure. Thought to be a non healing stress fracture.

Pathogenesis

Etiology

• Etiology unknown.
• Appears to have a genetic component with a recessive mode of inheritance. May be associated with elbow dysplasia Elbow: dysplasia - significant proportion of dogs with IOHC also have fragmentation or chondromalacia of medial coronoid process Elbow: medial coronoid process disease (MCPD).
• Humeral fractures that occur in dogs with IOHC generally result from normal activity (running, climbing or going down stairs).
• HIF - thought to be stress or fatigue fracture due to abnormal loads or compromised bone health. 

Predisposing factors

• One study found that being overweight Body condition scores predisposed Cocker Spaniels American Cocker Spaniel to humeral condylar fracture secondary to IOHC but another study did not confirm it.

Specific

• None.

Pathophysiology

• Unknown pathogenic mechanism.
• In normal dogs, medial and lateral aspect of humeral condyle are separated by a cartilaginous zone that disappears by 4 months of age. In dogs with IOHC cartilaginous zone appears to persist.
• Most affected dogs have IOHC on both elbow joints (1 in 5 dogs with IOHC will have bilateral humeral condylar fractures).

Timecourse

• Dogs with IOHC have an abnormal humeral condyle and slowly develop degenerative joint disease in affected elbow joints; may not fracture elbow joints until adult.

Diagnosis

Treatment

Prevention

Outcomes