Are medial ossified structure in the elbow clinically significant?

Acta Veterinaria Scandinavica 2020

Medial humeral epicondylar lesions and discreet calcified structures in the canine elbow: radiographic description of 183 cases

Arne Magnus Rørvik, Cathrine Trangerud* and Jorunn Grondalen^

Background
Medial humeral epicondylar lesions and associated calcified structures in the canine elbow have been poorly described, with prior studies focusing on small, clinically selected populations. This study aimed to assess the prevalence, radiographic characteristics, and breed predispositions for these lesions in a large cohort of dogs screened for elbow dysplasia (ED) in Norway. It also evaluated the association between these lesions and periarticular new bone formation (PNBF) to understand their clinical significance.

Methods
A prospective observational study was conducted over four years using radiographs from 14,073 dogs submitted to the Norwegian ED screening program. Elbows were evaluated in mediolateral and craniocaudal projections. Lesions were categorized as flexor enthesopathy (FE), fragmented medial epicondyle (FME), medial ossified structure (MOS), or medial lucent lesion (MLL). Prevalence, distribution, and PNBF were analyzed. Breed differences were explored for breeds with more than 500 radiographed individuals.

Results
Prevalence:
-Lesions were found in 1.3% of dogs (183/14,073), involving 211 elbows.
-MOS (0.7%) was the most common finding, followed by MLL (0.25%), FE (0.14%), and FME (0.07%).

Breed Predisposition:
-Labrador Retrievers and Newfoundland dogs had higher rates of FE (1.04% and 0.33%, respectively) and MOS (1.3% and 3.8%, respectively).
-Some breeds, like German Shepherds, showed no cases of FE despite high representation.

Lesion Characteristics:
-MOS was commonly located in middle or distal areas of the medial epicondyle.
-FE was characterized by bony spur formation and irregular bone structure at the medial epicondyle.
-FME presented as craters with adjacent bony fragments, particularly in young dogs.

PNBF:
-Increased PNBF was significantly associated with FE and FME but not with MOS or MLL.

Limitations
The study lacked clinical data for the included dogs, making it challenging to correlate radiographic findings with clinical lameness or discomfort. Some cases may have been underdiagnosed due to exclusion criteria or limited imaging capabilities.

Conclusions
This study provides a detailed radiographic characterization of medial humeral epicondylar lesions and highlights significant breed differences in prevalence. FE and FME are associated with increased PNBF and may have clinical relevance, whereas MOS and MLL appear to have limited impact on joint health. The findings underscore the need for breed-specific screening and further research to clarify the clinical implications of these lesions.

Medial ossified structure, in four elbows in craniocaudal in a–c mediolateral projections. a Medial ossified structure (MOS) in a middle location (white arrow) in a 12-month-old male Curly Coated Retriever. b MOS in a distal location (white arrow) in a 15-month-old female Howavart. c MOS in a caudal location (white arrow) in a 40-month-old male German Shepherd. Note the even structure of the distal edge of the medial epicondyle (black arrow) and the lack of spur formation and changes in the edge of the epicondyle. d MOS in various locations (white arrows) in the right elbow in a 34-month-old female Rottweiler. A similar lesion was present in left elbow

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