Luxation of the Femur.

Etiology and Occurrence.—­Uncomplicated femoral luxation is of less frequent occurrence in the horse than in the other domestic animals.  The deep cotyloid cavity renders disarticulation difficult and luxation does not often take place.  Complications that usually occur are rupture of the round (coxofemoral) ligament or fracture of the neck of the femur.  Falls or violent strains are necessary to produce this luxation.  Goubaux is quoted by Cadiot and Almy[41] as having observed the head of the femur in an instance wherein luxation had long existed.  In this case autopsy revealed the fact that the inner portion (two-thirds) of the head of the femur had completely disappeared.

Luxation of the femur is observed in old emaciated animals that are worked on slippery pavements.  Occasionally, evidence of chronic luxation of the femur is observed in the anatomical laboratory.  The chronicity of the condition is obvious when one notes the well formed articulation which Nature provides for the head of the femur, where fracture or other serious complications are not present.

Symptomatology.—­In every case there must exist either restriction of movement or an evident abnormal position of the leg, or both conditions may exist at once.  Also, the leg may be markedly shortened.  Manifestation of this affection varies, depending upon the character of the luxation (position of the head of the humerus with relation to the acetabulum).  Lusk[42] cites a case of a mule which had suffered femoral luxation.  The animal was destroyed and on autopsy the head of the femur found to be contained within a false articular cavity situated about four inches above the acetabulum.  In Dr. Lusk’s case as he states it, the following symptoms were presented:  “Limb shortened and fixed in a position of adduction.  While standing the affected limb hung directly across and in front of the opposite one; upper trochanter very prominent; skin over hip joint very tense.  The mobility of the limb was very limited, especially in the forward direction.”

Being very prominent when there is an upward luxation and less perceptible in downward displacement, the location of the trochanter major is an indicator of the character of the luxation with respect to the position of the head of the femur.  This variation of position causes abnormal tenseness or looseness of the skin over the region of the trochanter major.  Rectal examination is of aid in locating the head of the humerus.

Treatment.—­When it is evident that a subject should be given treatment and not destroyed, the animal must be cast and completely anesthetized.  With complete relaxation thus secured by rotation of the limb, using the hip joint region as a pivot, reduction may be effected.  Traction is exerted in the same direction from the acetabulum that the head of the femur is situated and by pressing over the joint, the displaced bone may be returned in position.  If luxation is downward, traction on the extremity will tend to dislodge the head of the femur from the inferior acetabular margin making reduction possible.