Number, sizes and shapes of the articular facets within the canine tarsal joint cavities

The complex interplay of motion within the canine tarsal joint is governed primarily by the morphologic features of its articulating facets. Their num ber, sizes and shapes in the Art. tibiofibularis distalis, the Art. tarsi a nd the Artt. intermetatarseae were investigated in both hind limbs of ten G erman shepherds. Preserving the articular cartilage, the distal ends of Tib ia and Fibula, the Ossa tarsi and the proximal ends of the Ossa metatarsali a were dissected and silicon casts were prepared of all articular facets. T he following measurements were obtained from the silicon casts and directly from the articular facets: surface area, aspect ratio, shape factor and ma ximum elevation or depression. The canine tarsal joint cavities contained 66 articular facets with variati ons ranging from 60 to 70 facets. Two of them were very large (>300 mm(2)), seven large (100-200 mm(2)), 17 medium-sized (30-100 mm(2)) and 40 small ( <20 mm(2)). The shape of the articular facets were elongated, triangular, i rregular, oval or rounded. There existed only 4 highly arched articular fac ets with a maximum elevation or depression from 5.1 to 10.7 mm, but more th an 80 % (54) of the contacting facets were almost flat (elevation or depres sion <1 mm). Comparing the contacting facets - forming articular pairs - th ose of the talocrural joint were conspicuous: they differed significantly i n sizes and shapes. All other articular pairs showed quite high degrees of similarity. These anatomical pecularities were discussed considering their clinical - o rthopedic importance.