Elbow Osteoarthritis Secondary to Adjacent Bone Remodeling and Fracture

Kenneth A. Johnson, MVSc, PhD, FACVSc, DACVS, DECVS

Three papers are published in this issue on the topic of disorders of the canine elbow that are frequently associated with development of secondary osteoarthritis.[1] [2] [3] The pathogenesis of osteoarthritis involves a complex interaction between the hyaline cartilage, adjacent subchondral bone, synovial membrane, and synovial fluid. There are multiple pathways by which the development of osteoarthritis can be initiated.

In equine and canine athletes, repetitive high-impact, supraphysiologic loading of joints can initiate a cascade of subchondral bone remodeling, which leads to changes in the mechanical properties of the subchondral bone.[4] This involves bone microdamage, necrosis, osteoclastic resorption, and new bone formation that is more dense and sclerotic than the original normal bone. Continued loading of this remodeled bone cause micro-cracks, minor fragmentation, or catastrophic fractures. This is accompanied by degeneration of the overlying hyaline cartilage.

Fragmentation of the medial coronoid process of the ulna, associated with elbow arthrosis, was first described more than 40 years ago. Although there have been many theories proposed, the etiology of this disease remains unknown. However, the much greater availability of computed tomography has facilitated the noninvasive quantification of bone density in working dog elbows. Ellis and colleagues have found breed differences in the apparent bone density of the medial coronoid process in unaffected dogs.[1] These are important observations that might open a door to better understanding of this elbow disease. Perhaps these variations in bone density may be linked to alterations in the mechanical properties of the subchondral bone that subsequently affect the overlying hyaline cartilage.

Most fractures of the lateral portion of the humeral condyle in puppies are due to being dropped from a height, and are considered to be traumatic. However, many humeral condylar fractures in skeletally mature dogs, especially Spaniel breeds, are associated with humeral intracondylar fissures (HIF). Although the cause of HIF is currently debated and unproven, the associated complete condylar fractures could be considered to be pathological fractures of the metaphyseal bone. Previous studies found that complications with fixation failure were common. The purpose of this recent study was to report the clinical outcome of repair of humeral condylar fractures with a lateral epicondylar anatomical plate.[2] Follow-up with the Liverpool Osteoarthritis in Dogs instrument found that median scores indicated mild impairment of function. This is perhaps not surprising because it is known that all elbows with repaired humeral condylar fractures develop secondary osteoarthritis. Moreover, radiographic follow-up found that the epicondylar portion of these fracture had usually healed (53/53 elbows), but the intracondylar articular portion of the fracture often remained unhealed (21/53 elbows). This persistent fracture nonunion suggests that chronic remodeling of pathologic bone, such as HIF, permanently interrupts the normal fracture healing process.

Another study of humeral condylar fractures in French Bulldogs found that 40% of dogs with repaired humeral condylar fractures had an HIF in the “normal” contralateral elbow.[3] The authors concluded that HIF should be considered a cause of humeral condylar fractures in French Bulldogs and that computed tomography of both elbows should be performed in French Bulldogs that are presented for repair of a humeral condylar fracture.

Kenneth A. Johnson

Editor-in-Chief, Veterinary and Comparative Orthopaedic and Traumatology

Publication History

Article published online:
16 September 2024

• References

• 1 Ellis LF, House AK, Shimura K, Frances M. Comparison of Hounsfield units within humeral trochlea and medial coronoid process in a population of Labrador X Golden Retriever Guide dogs and Border Collies. Vet Comp Orthop Traumatol 2024; 37 (05) 223-229
• 2 Jones RL, Tomlinson AW, Barnes DM. et al. Clinical assessment of a lateral epicondylar anatomical plate for stabilization of humeral condylar fracture in dogs. Vet Comp Orthop Traumatol 2024; 37 (05) 243-250
• 3 Lopez de la Oliva P, Arnott L, Roses L, Marshall W, Arnott D. Humeral condylar fracture in French Bulldogs: prevalence of contralateral intracondylar fissure, treatment and outcome. Vet Comp Orthop Traumatol 2024; 37 (05) 236-242
• 4 Stewart HL, Kawcak CE. The importance of subchondral bone in the pathophysiology of osteoarthritis. Front Vet Sci 2018; 5: 178