324 Anatomy Applied to Medicine and Surgery. 



will result. In every case, then, there must be a primary 

 downward dislocation, which is later converted into the 

 particular form present, since the structures forming and 

 protecting the joint, viz., the acetabulum and the capsular 

 ligament, are strong .and thick above, whereas, below, 

 they are almost wanting in the case of the acetabular mar- 

 gin, and weak in the case of the ligament, and it is on this 

 less protected portion of the joint that the head of the 

 bone, in abduction, rests. Wherever the rent in the cap- 

 sule be situated, most authorities agree that the untorn 

 part offers a considerable obstacle to reduction, although 

 different reasons have been assigned by different authori- 

 ties in explaining the opposition to the reduction of a dis- 

 location ; thus, Nathan Smith, for instance, considers that 

 the tension of the glutei muscles is responsible; Reid 

 thinks it is due to the abductors and the rotators, etc. 

 Reduction by Manipulation depends on the fulcrum- 

 like action of the untorn part of the capsule. In the re- 

 duction of a backward dislocation by manipulation, the leg 

 should be flexed on the thigh to enable the surgeon to use 

 the latter as a lever and for the purpose of relaxing the 

 hamstring muscles. He then, to relax the Y ligament, 

 raises the knee towards the patient's face, i.e., flexes the 

 thigh, with slight adduction until resistance is en- 

 countered. The limb is now gently carried outward, i.e., 

 circumducted, until resistance is met with, thus causing 

 the head of the bone to sweep around the acetabulum, 

 through an axis formed by the untorn part of the capsular 

 ligament, and to traverse, therefore, the path it followed 

 in arriving at its abnormal position. While this latter 

 movement is being performed, the thigh should be slightly 

 rotated outwards to relax the tense external rotator mus- 

 cles. The limb should now be gradually extended. Ham- 

 ilton says, "I do not know that the whole process should 



