Computed tomography and morphometry of the carpal canal in the dog

This study has been carried out to determine the normal size and shape of the carpal canal in the dog and to describe the salient anatomic structures with the aid of computed tomography. Computed tomographic examination of the carpal region was performed in the left and right forelimbs of 5 male and 5 female healthy German shepherd dogs, respectively. Areas, depths and widths of the carpal canal and identification of the anatomical structures were determined at two levels of the carpal region. The frozen forelimbs of two cadavers were sectioned with a saw to correlate the CT images with these sections. All scans were studied using both bony and soft tissue windows. The measurements of the right and left carpal canals did not differ significantly in male or female dogs, respectively although they were larger in the male than female dogs. In addition to this, the measurements of the carpal canal were larger in the distal than the proximal slice. The lateral tip of the deep digital flexor tendon was located more cranially in the distal part than in the proximal part of the carpal canal. Thus, the distance between the bones and the deep digital flexor tendon decreased and the distance between the deep and superficial digital flexor tendons increased. This localization is important in regard to neuropathy because the median nerve was located between the deep and superficial flexor tendons and this region was wider at the distal than the proximal part of the carpal canal. As a result of this study, it was found that the carpal canal of the dog much resembled that of humans and this similarity can easily generate a predisposition to focal neuropathy namely, carpal tunnel syndrome in dogs.