Osteochondrosis Disecans of the Tarsus in Labrador Retrievers: Clinical Signs, Radiological Data, and Force Plate Gait Evaluation After Surgical Treatment

Introduction
Osteochondrosis is a disease that affects endochondral ossification of cartilage in young, large, rapidly growing dogs. Osteochondrosis dissecans (OCD) of the tarsus is a manifestation of osteochondrosis affecting the medial or lateral trochlear ridge of the talus with partial or total detachment of a cartilage flap. Some investigators have reported hyperextension of the tarsus in standing dogs affected by OCD of the tarsus, even after surgical treatment. Researchers have been unable to agree on whether surgical treatment positively modifies the course of this disease.

Aims
To report the outcome of unilateral surgery, by a plantaromedial approach, in 15 Labrador retrievers with OCD of the medial trochlear ridge of the talus. To evaluate the influence on outcome of age at surgery, bilateral involvement, periarticular soft tissue increase, osteophyte size, decrease of range of joint motion (ROM) and follow-up. To assess the extent of tarsal hyperextension in the standing dog.

Material and Methods
A retrospective clinical and radiographic study was conducted and the post-treatment gait was analysed using a force plate. Ground reaction force data were compared with data derived from a control group of 24 healthy Labrador retrievers.

Results and Conclusions
Six dogs (40%) had an excellent or good clinical result. Propulsive and vertical forces significantly decreased in the operated limb and increased in the contralateral pelvic and ipsilateral or both thoracic limbs. The lameness was significantly correlated to the osteophyte size postoperatively, the ROM, the periarticular soft tissue increase, the length of the follow-up period, and the vertical ground force. No hyperextension instance was recorded.

Although most dogs improved, the prognosis remains guarded. This seems to be independent of age, bilateral involvement, or preoperative osteophyte size in these dogs. No relation between medial talar OCD and tarsal hyperextension instance was found in these dogs.