» Foot

Camelids have a skeletal structure of the foot similar to that of domestic ungulates; however, there are some differences of note. Because camelids do not have hooves, but instead have nails and a soft pad (sole, or "slipper"), they are not ungulates, even though they are sometimes referred to as such.

The nails possess primary and secondary laminae, although they are not as well developed as those in the horse. Fig. 38.38 shows the feet of a llama, and Fig. 38.39 shows the palmar and dorsal aspects of the llama foot.

Camelid Nails: The nails need to be trimmed regularly, and they are non-weight bearing.

The fused metacarpal and metatarsal bones have separate articular surfaces for each digit, as in ruminants, and similar to ruminants, they also have two proximal sesamoids per digit. However, in contrast to ruminants, the two synovial compartments of the metacarpophalangeal or metatarsophalangeal joints usually do not communicate in the camelid. There are no vestigial digits or associated skeletal structures. Each digit has an ergot at the level of the fetlock joint, and a ligament of the ergot descends on the abaxial side of each digit from the ergot to the digital cushion.

Within the foot, there are proximal, middle, and distal phalanges, but camelids lack a distal sesamoid bone. Because of the stance of the camelid, the proximal interphalangeal joint is hyperextended. The angle of the first phalanx with the ground is normally 52 degrees. The bones of the hindfoot of a camel, which are similar to those in llamas and alpacas, are shown in Fig. 38.40.

Each digit has a combined palmar annular ligament and proximal interdigital ligament to hold the digital flexor tendons in place. The digital flexors share a tendon sheath at the level of the fetlock joint. The deep digital flexor tendon connects to the middle phalanx; this connection is termed the vinculum, and it carries vasculature to the bone. The deep digital flexor tendon also has fibers that enter the digital cushion.

The deep digital flexor is reinforced by a cartilage plate as it passes over the middle scutum (a flat plate where the superficial digital flexor tendon inserts on the middle phalanx) at this level. Also at this level, a distal digital annular ligament is present over the deep digital flexor tendon, and an interdigital ligament passes between the two digits. The distal scutum is a thick cartilage plate in the location of the distal sesamoid bone of other species, attached to the distal phalanx and the digital cushion, and over which the deep digital flexor tendon passes. Some of these features are shown in Fig. 38.41.