Ultrasonographic examination of the carpal canal in dogs

Abstract

The aim of this study was to determine the course of the median nerve and its adjacent structures in the carpal canals of 8 healthy dogs by using high-frequency transducers. Before performing ultrasonography, the transverse and posteroanterior diameters as well as the perimeter of the carpus were measured at just proximal to the side of the carpal pad. The anatomical structures were then determined at two levels of the carpal canal, which were named the proximal and distal levels, on the transverse sonograms. The cross-sectional areas, perimeters and the transverse and posteroanterior diameters of the median nerve were measured at these levels. Although all the measurements were larger at the proximal level, significant differences between the proximal and distal levels were determined for the cross-sectional area, the perimeter and the transverse diameter of the median nerve. On the transverse sonogram, the deep digital flexor tendon was seen in almost the center of the carpal canal like a comma shape and also it had a small concavity on the caudal side. The superficial digital flexor tendon was seen as an ovoid shape on the transverse sonograms and it was located nearly at the posterior side of the carpal canal. Both tendons were seen as intermediate-grade echogenic structures. The median artery was located inside of the concavity of the deep digital flexor tendon. Also, the median nerve was seen at the posteromedial side of the median artery. As a result of this study, the cross-sectional areas of the median nerve ranged between 1.01-2.68 mm2 at the proximal level and between 0.93-1.91 mm2 at the distal level.

Anatomy of the Palmar Region of the Carpus of the Dog

“…On the other hand, Evans and de Lahunta [ 9 ] described that the canalis carpi has a wider extent, being the space generated deep to the flexor retinaculum and occupied by the tendons of the flexor carpi radialis , flexor digitorum superficialis , and flexor digitorum profundus muscles, the nervus medianus , the arteria and vena mediana , and the arteria and nervus ulnaris . This was also supported by Turan et al [ 10 , 11 , 12 ] in later studies about the diagnosis of potential carpal canal syndrome in dogs. Ettema et al [ 13 ], however, stated that the tendon of the flexor digitorum superficialis muscle is not located inside the canalis carpi .…”

“…The inconsistency found in the literature is probably related to the non-differentiation between the superficial and deep parts of the flexor retinaculum . Dyce et al [ 7 ], Evans and de Lahunta [ 9 ], and Turan et al [ 10 , 11 , 12 ] made their descriptions assuming that the flexor retinaculum was only constituted by the superficial part, which led to the inclusion of other tendons and neurovascular structures inside the hypothetical canalis carpi . However, the superficial part of the retinaculum did not generate a true canal below because, by definition, a canal is a tubular duct or channel.…”

Carpal canal lipoma causing lameness in a dog

“…It has been reported that nerves in humans have increased accumulations of connective tissue in areas of normal anatomic compression, and in a report on peripheral nerve compression secondary to lipomas in humans, the masses were found to be derived from the fatty tissues adjacent to the nerves (13,15). An ultrasonographic study of the canine carpal canal found a difference in echogenicity of the median nerve compared to other peripheral nerves, which the authors postulated as being secondary to an extra accumulation of connective tissue around the nerve (16). In this case, the CT showed the presence of normal adipose tissue in the carpal canal of the contralateral limb (ǠFig 1B).…”

The Structure of the Brachial Plexus in Selected Representatives of the Caniformia Suborder

“…The similarities demonstrated in our study suggest that it is possible to use the techniques of surgery and anaesthesia applied to the domestic dog [ 45 , 46 , 47 ]. The knowledge of the anatomy of nerves and muscle innervation is used in clinical diagnostics— for example, to differentiate injuries in the brachial plexus and around the periphery of the thoracic limb [ 48 , 49 , 50 , 51 , 52 ].…”