Anatomy of the Palmar Region of the Carpus of the Dog

Arthrographic description of the canine carpal joint cavities and its recesses

Joint effusion is diagnostically important. The canine carpal joint effusion, which is sometimes difficult to detect clinically, has received less attention in diagnostic ultrasound (US) studies. The aim of the present study was to provide a description of the morphological appearance of the canine carpal joint cavities and recesses using US, radiography, helical computed tomography (CT) and three-dimensional volume rendering technique (3D-VRT) images and to prove the applicability of musculoskeletal US for the detection of artificial carpal joint effusion in dogs. The understanding of the characteristics of these structures in normal patients is essential in the diagnosis. Twenty-eight clinically and radiologically unremarkable canine carpal cadavers of different breeds were examined, representative images were selected and anatomical structures were labelled. The canine carpal joint cavities and in particular its recesses had a complex appearance with a basic structure found in all dogs: Antebrachiocarpal joint: dorsoproximal antebrachiocarpal recess, dorsodistal antebrachiocarpal recess, medial antebrachiocarpal recess, lateral antebrachiocarpal recess and five palmar antebrachiocarpal recesses. Middle carpal joint: two dorsal middle carpal recesses, medial common middle carpal and carpometacarpal recess, lateral common middle carpal and carpometacarpal recess, four palmar middle carpal recesses. The carpometacarpal joint had dorsal and palmar funnel-shaped and irregular, finely tubular extensions, the most prominent ran dorsal to metacarpal III, the maximum distal end represented the proximal metacarpal diaphysis. All recesses presented ultrasonographically as a generalized anechogenic to hypoechoic filled continuation of the articular capsule with an indistinct peripheral hypoechogenic to isoechogenic fine capsule, the synovial-connective tissue interface was difficult to identify. The novel results of this study provide the first morphological description of the ultrasonographic, radiographic and computed tomographic arthrographic appearance of the canine carpal joint cavities and recesses with different injection volumes. The canine carpal joint cavities and in particular its recesses had a complex appearance with a basic structure found in all dogs. The applicability of musculoskeletal US to visualize an artificial carpal effusion has been demonstrated. The results of this study, and in particular US, give the practitioner an advantage in visualizing joint effusion and assist in the decision to perform arthrocentesis.

Intraspecific anatomical variations of the extensor tendons of the carpus and digits with a reexamination of their insertion sites in the domestic dog (Canis lupus familiaris): a cadaveric study

BACKGROUND

The aim of the current study was to investigate the frequency of variations of the extensor tendons of the carpus and digits in the domestic dog (Canis lupus familiaris) with a reexamination of their insertions as well as the morphometric measurements of the tendons and the brachioradialis muscle. In total, we investigated 68 paired thoracic limbs of the domestic dog (16 females and 18 males) which were fixed in a 10% formalin solution.

RESULTS

The extensor carpi radialis (ECR) tendons showed striking variations in both splitting and insertion sites. In 4.4% of dissections, ECR had three tendons. Of these tendons, the extra tendon either attached independently on the fourth metacarpal bone (one right) or joined its counterpart tendon at the distal end (cross-connections) (one bilateral). It is worth mentioning that one of the ECR tendons split into two or three slips which inserted on the first, second, third, or fourth metacarpal bone in 11 (16.2%) of the specimens. In addition, we found a long tendinous slip originating from the ECR tendons to digit II or III in 7.4% of the distal limbs. The most common type of contribution to digit III was a third tendon of the extensor digiti I et II (ED III) joining the extensor digitorum lateralis (EDL III) with a frequency of 17.6%. In other types of variations, the contribution to digit III was incomplete. A part of the abductor pollicis longus (APL) deep to the superficial part of the flexor retinaculum seemed to continue up to the flexor digitorum superficialis (FDS) tendon.

CONCLUSIONS

The rare intraspecific variations of the extensor tendons of the manus described in the current research are valuable from both clinical and phylogenetic perspectives. Nonetheless, their functional importance needs more studies.

Ultrasonographic anatomy of the palmar region of the carpus of the dog

The palmar region of the canine carpus may be injured by traumatic, inflammatory, infectious, neoplastic, and degenerative disorders. The normal ultrasonographic anatomic features of the dorsal region of the canine carpus have been published, however information regarding the palmar region is currently lacking. The aims of this prospective, descriptive, anatomic study were (1) to describe the normal ultrasonographic characteristics of the palmar carpal structures in medium to large-breed dogs, and (2) to establish a standardized ultrasonographic protocol for evaluating them. As in the previously published study, the current study consisted of two phases: (1) identification phase, in which the palmar structures of the carpus were identified ultrasonographically in fifty-four cadaveric specimens and an ultrasonographic protocol to examine them was developed; and (2) descriptive phase, in which the ultrasonographic characteristics of the main palmar structures in twenty-five carpi of thirteen living healthy adult dogs were documented. The tendons of the flexor muscles of the carpus and digits, the superficial and deep parts of the retinaculum flexorum, the carpal canal and the median and ulnar neurovascular structures were ultrasonographically identified and described. Findings from the current study can serve as a reference for evaluating dogs with suspected injury involving the palmar carpal region using ultrasonography.