CT Reveals Density Deficits and Compensation in Canine Tarsal Osteochondrosis

Subchondral Bone Density Changes of the Talus in Dogs With Tarsocrural Osteochondrosis

Yasamin Vali 1, Walter Dingemanse 2, Magdalena Müller-Gerbl 3, Eberhard Ludewig 4, Henri van Bree 5, Ingrid Gielen 6

Background:
Osteochondrosis (OC) and osteochondritis dissecans (OCD) are developmental orthopedic diseases commonly affecting rapidly growing large-breed dogs. The tarsocrural joint, particularly the medial trochlear ridge of the talus, is a recognized site for lesions in Labrador Retrievers. These lesions arise from disturbances in endochondral ossification and are linked to joint overloading. This study aimed to assess subchondral bone mineral density changes in dogs with tarsocrural OC/OCD using computed tomography osteoabsorptiometry (CTOAM), with particular focus on comparing affected and contralateral joints.

Methods:
This retrospective study included 8 Labrador Retrievers with unilateral tarsocrural OC/OCD. CT scans were used to evaluate subchondral bone density distribution in both affected and contralateral tarsal joints. Densitograms were created using maximum intensity projections, and density maxima were mapped and quantified. Two dogs also underwent follow-up CT after arthroscopic surgery. Data were analyzed for differences in mean and peak bone mineral density and density distribution patterns over time.

Results:
The medial trochlear ridge of the talus in affected joints showed a focal area of significantly decreased bone density (mean 612.6 ± 88.4 mg HA/cm³), surrounded by a sclerotic rim. Contralateral joints showed significantly higher bone density (mean 780.7 ± 39.8 mg HA/cm³, P = 0.001). Follow-up scans in two dogs revealed dynamic remodeling: in one dog, the defect density decreased further, while in the other, density increased post-surgery. Contralateral joints showed consistent increases in mean and maximum density over time, suggesting compensatory adaptation to altered loading due to lameness.

Limitations:
The study was limited by its small sample size and retrospective design. The absence of a healthy control group restricts comparisons, and follow-up data were limited to only two dogs. Results may be biased by the inclusion of only clinically affected referral cases. Furthermore, no correlation was made between density changes and clinical severity or functional outcomes.

Conclusions:
Tarsocrural OC/OCD in Labrador Retrievers leads to focal subchondral bone density deficits in the medial trochlear ridge, with compensatory increased density in the contralateral limb. These findings support the biomechanical theory of disease progression and adaptation, and underscore the utility of CTOAM in detecting and monitoring subclinical joint remodeling. Further prospective studies with larger populations are needed to explore the clinical implications and progression of these changes.

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