History: Chronic significant lameness for several weeks of the left front leg, today grade 3/5. Painful with extension and manipulation of the elbow.
Imaging: Non-contrast enhanced elbow CT (1 mm in high frequency/bone algorithm)
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This is a classic example of bilateral incomplete ossification of the humeral condyle (IOHC). There are similar left and right humeral condylar lesions characterized by undulant sagittal plane hypoattenuating defects centered on midline surrounded by moderate subchondral sclerosis (hyperattenuating subchondral bone). On the left there is mild widening of this defect compared to the right (dorsal plane reconstruction). Bilaterally there is no evidence of a step defect associated with the medial and lateral components of the cortices to indicate a displaced fracture.
IOHC is thought to result from failure of the medial and lateral aspect of the humeral condyle to unite. However, it is important to realize that a fissure can develop in a humeral condyle that has undergone complete fusion; i.e. acquired IOHC (Farrell, 2011).
IOHC will predispose to an intercondylar “Y” fracture of the distal humerus
Spaniels are overrepresented for IOHC and, as such, IOHC should always be considered in Spaniels with chronic forelimb lameness. However, other breeds (such as Shepherds, Labradors and large breed dogs in particular) and also other species (Vietnamese pot-bellied pigs) can be affected.
Diagnosing IOHC with radiographs can be inaccurate due to superimposition of the cleavage plane in the humeral condyle on the olecranon in craniocaudal radiographs. Slight elbow obliquity for the craniocaudal view may enhance the conspicuity of the cleavage plane. CT is the test of choice for diagnosis of IOHC. The use of MRI for diagnosis of IOHC has yet to be thoroughly investigated. This disease can often be bilateral even if lameness is unilateral, so imaging both limbs is recommended if this disease is suspected.
Additionally, in this dog there is bilateral medial coronoid disease with moderate sclerosis of the medial coronoid process of the left and right ulna with osteophyte formation on the cranial aspect of each medial coronoid process. There is no evidence of fragmentation or a fracture of either coronoid process. Medial coronoid disease has been reported in 26% of patients with IOHC and degenerative joint disease was found in 79% of elbows in one study (Carrera et al., 2008).
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