864 LUXATION OF THE PHALANGES. 



of the flexor pedis perforans over the posterior surf ace of the three phalanges, 

 while the tendon of the flexor pedis perforatus passes behind the perforans 

 over the fetlock and coronary joints. The metacarpo-phalangean 

 aponeurosis forms a strong fibrous brace for the flexor tendons at the 

 sesamoids and pastern, and supports and protects the nerves and blood- 

 vessels. In company with the sesamoid ligaments, the extensor pedis 

 and flexors perforans and perforatus tendons act in fixing the fetlock joint : 

 with the posterior coronary assisted by the lateral ligaments, they also 

 fix the coronet and pedal joints, and thus sustain the weight of the body. 



The terms dorsal and volar flexion are hereafter used to describe the 

 movements occurring in the digit: the first indicates anterior flexion, 

 the movement produced by the extensor, or resulting from weakness or 

 rapture of the flexors : the second indicates posterior flexion, or movement 

 produced by the flexor muscles. 



I.— LUXATION OF THE PHALANGES. 



The union of the three phalangeal joints is so strong that displace- 

 ments (luxations) are exceedingly rare, and must always be preceded 

 by extensive rupture of ligaments or tendon. Luxation of the 

 fetlock-joint is seen in race-horses after complete rupture of the 

 flexor tendons ; the lower end of the metacarpus then passes down- 

 wards over the posterior margin of the articular surface of the os 

 suffraginis, causing excessive dorsal flexion of the fetlock-joint. 

 Less frequently, the metacarpus is displaced anteriorly ; this 

 indicating rupture of the lateral and sesamoid ligaments. Lateral 

 displacements are exceedingly rare, and are necessarily accompanied 

 by rupture of the lateral ligaments. They are sometimes produced 

 by violent struggles to free the foot which has accidentally become 

 fixed, as, for example, between railway-metals. Wilhelm saw lateral 

 displacement in the hind leg of a horse which had run away and had 

 fallen. The joint was directed outwards. Siedamgrotzky has 

 described three similar cases. In other animals luxations of the 

 phalanges are still less common. 



The diagnosis is easy. The altered position of the joint, and 

 the changes discovered by manual examination, leave no room for 

 doubt. 



The course of luxations is almost always unfavourable, on 

 account of the excessive rupture of tissue. The larger animals either 

 die from decubitus, or more or less marked lameness remains which 

 prevents them working. Reported cases, however, show that 

 recovery may occasionally take place. 



Wilhelm records recovery in eight weeks in the above-described 

 case. He placed the horse in slings, and after reducing the dislocation, 

 applied a wooden splint fastened to the metacarpus by straps. 



