Hind Limb First Digit (Dewclaw) In Dog: Morphologic And X-Ray Investigations In Relation With Genetic And Surgical Aspects

The domestic carnivores have five digits in front limbs and generally, four in the pelvic limbs, the first digit being absent. Scarcely ever in cats and more frequently in dogs, the first digit can be present in pelvic limbs, as a rudiment, more or less developed, being known as "dewclaw". This term is used also for the first digit of the thoracic limb, being more reduced than the rest of the digits, but is more proper for the pelvic limb. Genetically, the presence of the dewclaw in pelvic limb, simple or double, and double in thoracic limb is known as hind-limb-specific preaxial polydactyly - PPD. Taking into account these aspects, we set out to analyse the morphological and structural variability of the hind limb dewclaw in dogs, in relation with the development degree of the first metatarsal bone, using clinical and imagistic exam. The most of the animals were patients of two veterinary clinics having various pathologies of the legs. Clinically were identified two animals having dewclaw in pelvic limb, one being simple and not joined and the other one, double and joined. The X-ray exam, even the number of the animals with dewclaw wasn't high, revealed many morphologic types of the dewclaw: simple and not joined dewclaw, without phalanges (one case); simple and not joined dewclaw, in his structure having one or two phalanges (three cases); simple and joined dewclaw, the osseous structure including two phalanges, simultaneously being present the first metatarsal bone represented by the proximal and distal extremity (two cases); simple dewclaw, well developed, with two phalanges and joined with the first metatarsal bone completely developed (two cases). In most of the cases (seven) was noted the lack of the dewclaw, but the presence of the proximal extremity of the first metatarsal bone and, in other two cases the first metatarsal bone was completely absent. Can be noted firstly an obvious polymorphism of the dewclaw in dogs, this aspect being important especially when the surgical removal is necessary.