Microcomputed tomography and histology of a fragmented medial coronoid process in a 20‐week‐old golden retriever

Abstract

A 20-week-old male golden retriever, which was not lame and showed no clinical signs of a fragmented medial coronoid process (FCP), was euthanased for another study and perfused intravenously with formaldehyde. Gross dissection revealed no abnormalities within the right elbow joint. The medial coronoid process was excised, embedded in methylmethacrylate, scanned in a microcomputed tomography (microCT) scanner and sectioned for histology. The microCT scans revealed a dense trabecular bone structure, much denser than in other dogs of similar age, which was considered to be responsible for the sclerosis visible at the base of the coronoid process in radiographs. Three-dimensional reconstructions indicated that there was a small step within the subchondral bone, extending from the apex towards the radial notch. Histology revealed a necrotic lesion between locally thickened articular cartilage and the subchondral bone, characteristic of osteochondrosis.

Histomorphometry of Fragmented Medial Coronoid Process in Dogs: A Comparison of Affected and Normal Coronoid Processes

“…Olsson concluded that FMCP was caused by retention of abnormally thick cartilage and that ossification of fragments occurred only after fragmentation 1 . Recently published work based on a single case study of FMCP also concluded that histologic lesions, including locally thickened cartilage and necrosis between the AC and subchondral bone seen in this case, were characteristic of osteochondrosis 16 . Our study, while not focused on the evaluation of cartilage, found no evidence to support this belief.…”

“…He hypothesized that the thickened cartilage would not receive adequate nutrition and therefore would undergo necrosis and fissuring, resulting in the observed lesions 1 . Other investigators have accepted this pathogenesis, and the interrelationship between OCD and FMCP, 3,5,7 including a recent case study, which concluded that histologic lesions observed in a case of FMCP were consistent with osteochondrosis 16 . However, a study comparing OCD flaps and FMCP fragments concluded that these 2 diseases were separate entities, OCD being a primary lesion of cartilage, and FMCP being a primary lesion of subchondral bone with secondary cartilage changes 17 .…”

Working Algorithm for Treatment Decision Making for Developmental Disease of the Medial Compartment of the Elbow in Dogs

“…Once the fragment is detached, its mobility may protect it from further load-bearing and cartilage abrasion, whereas loss of subchondral vascularity contributes to increasing cartilage thickness and even necrosis of the deeper layers of cartilage and/or bone typical of free osteochondral bodies within a joint, perhaps accounting for some reports of OC like lesions. 38 In our experience, it is common for the remaining intact portion of the medial aspect of the coronoid process to be affected by cartilage abrasion or eburnation because of persistent supraphysiologic loading with HUC. 39 Joint pain and lameness can occur when there is intact cartilage over underlying subchondral pathology.…”

Bone Scintigraphy for the Diagnosis of an Abnormal Medial Coronoid Process in Dogs

“…Increased osteoblastic activity, and thus increased bone turnover, is detected by bone scintigraphy, 19 even before detectable radiographically. This increased osteoblastic activity in subchondral bone may be a primary cause 26 or a consequence 18,24 of the disease of the MCP. Not in all patients, however, is MCP sclerosis related to fragmentation 27 .…”

“…Positive bone scintigraphy may be explained by the microscopic findings that bone sclerosis in the area of the MCP coincides with early coronoid lesions 20 . Sclerosis was also detectable using micro‐CT and is considered to be one of the radiographic signs of an abnormal MCP 18,24 . Increased osteoblastic activity, and thus increased bone turnover, is detected by bone scintigraphy, 19 even before detectable radiographically.…”