Proximal Suspensory Desmitis in the Forelimb and the Hindlimb

The suspensory ligament (SL) can be divided into three separate regions which are subject to injury: the proximal part, the body, and the branches. For clinical purposes in the forelimb the proximal part extends from approximately 4 to 12 cm distal to the accessory carpal bone, and in the hindlimb from approximately 2 to 10 cm distal to the tarsometatarsal joint. In the forelimb, the SL originates from two heads which rapidly fuse. In the hindlimb this division is less obvious. The ligament contains a variable amount of muscular tissue (2–11%), which tends to be bilaterally symmetrical. In the forelimb the SL originates from the palmar carpal ligament and the proximal aspect of the third metacarpal bone, whereas in the hindlimb it originates principally from the proximoplantar aspect of the third metatarsal bone. In the forelimb the SL is innervated by the palmar metacarpal nerves, derived from the lateral palmar nerve, which receives fibres from both the ulnar and median nerves. The hindlimb SL is innervated by the plantar metatarsal nerves, derived from the tibial nerve. The proximal SL is closely related to the palmar outpouching of the middle carpal joint in the forelimb, and the plantar outpouching of the tarsometatarsal joint in the hindlimb. Proximal suspensory desmitis (PSD) is a common injury in both forelimbs and hindlimbs of athletic horses, and may occur unilaterally or bilaterally.