This study aims to elucidate the topographical anatomy of the carpal flexor retinaculum or palmar anular carpal ligament (PACL) in the horse. Ten specimen of the carpus of five healthy horses were studied by dissection in layers. Slices of 5 mm in thickness facilitated observation of the soft tissues. The superficial layer of the PACL subdivides into five compartments: one for the palmar nerve and the arterial and venous branches, one for only the radial artery, one for the radial vein, and one for the tendon of the radial carpal flexor muscle, and finally for the deep layer that supports all tendinous structures located palmar to the carpus, as well as the median artery and palmar medial nerve. The sections of the segmented PACL that are affected by carpal canal syndrome may vary with the aetiology of the space-occupying process. Precise anatomical knowledge of the structures may help in understanding the pathological processes and determining the most appropriate therapy.

Aus dem Institut für Anatomie 1 und der Klinik für Orthopädie der Huf-und Klauentiere 2 der Veterinärmedizinischen Universität Wien Zusammenfassung Der tiefe Zehenbeuger des Pferdes entsteht sowohl an der Vorder-als auch an der Hintergliedmaße aus drei Köpfen, die sich jeweils zur tiefen Beugesehne vereinigen, die zusätzlich im Bereich des Metapodiums von einem Ligamentum accessorium verstärkt wird. Am Acropodium verläuft die tiefe Beugesehne (TBS) entlang der drei Gleitschilder, Scutum proximale, medium und-distale, wo sie jeweils von synovialen Strukturen geschützt ist. Ohne vorher Sehnenfasern abzugeben, inseriert sie an der Facies flexoria des Hufbeins. In halber Höhe der palmaren beziehungsweise. plantaren Seite des Kronbeins treffen die Synovialmembranen der Fesselbeugesehenscheide, des Hufgelenks und der Bursa podotrochlearis, nur von wenig und lockerem Bindegewebe getrennt, aufeinander, wodurch eine scheinbare Verbindung der TBS mit dem Kronbein entsteht, die aber auf Grund ihrer Beschaffenheit keine Kraft überleiten kann. Einen Kronbeinschenkel der tiefen Beugesehne gibt es nicht.

The synovial structures of the M. fibularis longus were studied by dissection on 23 cat, 28 dog, 20 pig, 17 ox, 15 sheep and 17 goat limbs. Five injections with Technovit into the tarsometatarsal joint were made for each species. The dog had two tendon sheaths while all other species had only one lateral one. The mesotendon approached the tendon from the medial aspect and was fenestrated in the dog (here only in the proximal segment), pig, sheep, and goat, but in the cat and ox the fenestration was inconstant. In the area of the lateral malleolus the lateral tendon sheath narrowed (in the dog only in the proximal segment). The synovial structures on the plantar aspect in the cat, dog, pig, and sheep were formed by a recess of the tarsometatarsal joint; while in the ox and goat they formed a tendon sheath that took its origin from the same joint. The plantar recess surrounded the tendon three quarters of the way in the dog, and in cat, pig, and sheep only half way. Nomenclaturial consequences for the NAV are discussed.

Zusätzlich zur Riechschleimhaut dient das Organum vomeronasale der Wahrnehmung von Gerüchen und vor allem von Pheromonen. Das Organ weist bei einem mittelgroßen Pferd eine Längenausdehnung, beginnend von einer gedachten Querebene ca. 10 cm kaudal des Naseneinganges bis zu einer Querebene durch die Mitte des zweiten Vormahlzahnes auf. Beim Flehmen kontrahieren sich die Mm. levator labii superioris, levator nasolabialis, caninus und lateralis nasi. Die Oberlippe und die Nasenspitze werden angehoben und der Naseneingang durch die Annäherung der Lamina an das Cornu des Flügelknorpels stark verengt. Dadurch wird die Luft während des Flehmens direkt in die nasenhöhlenseitige Öffnung des Vomeronasalorgans geleitet. Beim Flehmen nehmen die Pferde eine charakteristische Körperhaltung ein.

Schlüsselwörter: Pferd, Hufkissenbänder, myxoides Gewebe, Stereologie, Cavalieri-Methode. Digital cushions in horses: An elastic component of the equine digital organThe digital cushion in horses, hoof, and hoof cartilage are structures reducing mechanical loads. The digital cushion is fixed to adjacent structures by ligaments and thick fibre bundles. The pars torica of the digital cushion is localised between the heels, the pars cunealis is underlying the frog. Due to the hoof mechanism during locomotion, the pars torica undergoes more significant deformation than the pars cunealis. It is unknown whether different mechanical loads result in a different structure and fixation of the individual parts of the digital cushion. The aim of our study was to answer these questions. Digital organs of horses with an age of 0.5-28 years were examined macroscopically (n=20) and microscopically (n=20). The quantitative composition of the pars cunealis and the pars torica of the digital cushion in young and adult horses was assessed by the Cavalieri method, a stereological method for volume estimation based on section analysis. The compact pars cunealis and the soft-elastic pars torica already differed macroscopically. On the palmar/plantar side of the pars cunealis, massive fibre layers were predominantly directed towards the toe axis. The pars torica was fixed to the hoof cartilages by chondropulvinal ligaments and finger-shaped interdigitations. The digital cushion contained 39.3% dense, irregular, connective tissue, 37.6% tissue with matrix rich in hyaluronic acid, 17.4% elastic fibres and 5.7% adipose tissue. Dense connective tissue was found mainly in the pars cunealis. In foals, the pars torica contained more adipose tissue than in adult horses, where it was replaced by dense connective tissue and tissue with a hyaluronic-acid rich matrix. Elastic fibres were mainly detected in the pars torica and the transition zone between pars torica and pars cunealis. The composition of the digital cushion varied individually, probably due to different work loads and purposes of use of the examined horses. Further studies, preferentially in horses under the same training conditions are necessary to obtain information on the influence of mechanical loads on the inner structure of digital cushions.