Osteochondritis dissecans-like lesions of the occipital condyle and cervical articular process joints in a Saddlebred colt horse

Chee Kin Lim, Jan Fletcher Hawkins, Andrea Lynn Vanderpool, Hock Gan Heng, Caroline Cooper Gillespie Harmon, Stephen Dana Lenz

Osteochondritis dissecans (OCD) is a sequela to osteochondrosis, whereby the cartilage superficial to the site of osteochondrosis fractures and gives rise to osteochondral fragments in the affected joint. In this case, both the radiological and computed tomography findings were supportive of classical severe OCD but the histologic findings were not supportive of the diagnosis of OCD. A 1 year and 6 months old, Saddlebred, colt was presented for evaluation of chronic cervical pain. Standing laterolateral radiographs revealed an osteochondral fragment with corresponding irregular subchondral bone defect at one of the occipital condyle. Computed tomography confirmed the presence of osteochondral fragments at the left occipital condyle and several articular process joints of the cervical spine, with associated subchondral bone defects and sclerosis, suggestive of OCD. However, the lack of ischemic chondronecrosis microscopically was not supportive of a histologic diagnosis of OCD. Therefore, the term 'OCD-like lesions' was deemed most appropriate for these cervical lesions. In the event where imaging features were characteristics of OCD but lack of histologic evidence of ischemic chondronecrosis, the term 'OCD-like lesion' is deemed most appropriate.