Medial Humeral Epicondylitis in Cats

Abstract

Objective: To describe medial humeral epicondylitis in cats based on radiographic, anatomic, and histologic observations. Study Design: Prospective cohort study. Animals: Feline cadavers (n = 60). Methods: Extended craniocaudal, and extended and flexed mediolateral radiographic projections were taken of both elbows of 60 consecutive European shorthair cats that died or were euthanatized. Elbows with new bone formation at the medial epicondyle were dissected and embedded in methyl-methacrylate (MMA). For comparison, both elbows of a cat with no radiographic changes were prepared in a similar manner. Sections of the MMA blocks were Giemsa stained and examined with light microscopy. Results: Bilateral new bone formation was identified radiographically at the medial aspect of the humeral epicondyle in 6 cats (10%). All of these cats had mineral deposition in the humeral head of the flexor carpi ulnaris muscle. Other findings were cartilage damage (n = 3 cats), an additional loose medial joint body (1), and tendinosis (3). The ulnar nerve was flattened and displaced caudally, and signs of chronic epineural fibrosis were present in 2 severely affected cats. Conclusions: Ten percent of this feline population had radiographic evidence of medial humeral epicondylitis with chronic degeneration, mineralization, and metaplastic bone formation in damaged fibrillar matrix involving the origin of the humeral head of the flexor carpi ulnaris muscle. New bone formation caused displacement and compression of the ulnar nerve in severely affected elbows. Based on our findings, medial humeral epicondylitis appears to be a common disorder in cats with potential clinical sequelae.People participating in athletic activities may develop lateral (tennis elbow) or medial humeral epicondylitis depending on the mechanical demands on the elbow and its muscular attachments, inherent to the type of sport activity. Both types of epicondylitis are caused by repetitive overuse injuries. Medial humeral epicondylitis in people is usually associated with sports like baseball and golf. In children, overuse injuries can lead to medial epicondylar apophysitis and epicondylar avulsion fractures referred to as little leaguer's elbow.

Medial humeral epicondylitis in clinically affected cats

“…This prospective cohort study describes the findings and long‐term outcome in cats clinically affected with MHE. Chronic MHE, attributed to inflammation of the origin of the humeral head of the FCUM was found in all cats, consistent with postmortem findings in a previous study . In a previous study in dogs, medial epicondylitis was associated with calcified tissue in the origin of the flexor digitalis profundus muscle .…”

“…Radiographic and histologic evidence of medial humeral epicondylitis (MHE) has been reported in 10% of cats in a postmortem study of 60 cats . Findings associated with MHE were chronic degeneration, mineralization, and metaplastic bone formation in the origin of the humeral head of the flexor carpi ulnaris muscle (FCUM) .…”

“…Radiographic and histologic evidence of medial humeral epicondylitis (MHE) has been reported in 10% of cats in a postmortem study of 60 cats . Findings associated with MHE were chronic degeneration, mineralization, and metaplastic bone formation in the origin of the humeral head of the flexor carpi ulnaris muscle (FCUM) . This chronic condition, affecting the medial side of the elbow, was frequently found to result in flattening and caudal displacement of the ulnar nerve, periosteal adhesions, and epineural fibrosis, as well as loose joint bodies and tendinosis on postmortem examination .…”

Surgical management of medial humeral epicondylitis, cubital synovial osteochondromatosis and humeroradial subluxation in a cat

“…1 This condition also frequently results in flattening and displacement of the ulnar nerve, periosteal adhesions and epineural fibrosis, as well as intra-articular mineralized bodies. 1 …”

“…1 It was postulated that the thickened and partially mineralized joint capsule lead to subluxation of the humeral condyle and subsequent cartilage defects. However, in a more recent study involving clinically affected cats with MHE, there was no mention of subluxation affecting any cat.…”