Fig. 70.—Adjustable Double-inclined Plane.
Dislocation of the Hip
It is unnecessary for our present purpose to attempt a comprehensive classification of the numerous varieties of dislocation that have been met with at the hip-joint. It will suffice if we divide them into those in which the head of the femur passes backward, and comes to rest on the dorsum ilii, or in the vicinity of the great sciatic notch; and those in which it passes forward and comes to rest in the obturator foramen, or on the pubes ([Fig. 71]).
Fig. 71.—Diagram of the most common Dislocations of the Hip.
The backward are much more common than the forward dislocations, in contrast to what obtains at the shoulder, where the forward varieties predominate.
On account of the great strength of the hip-joint, dislocation is by no means a common injury. It occurs most frequently in strong adults after the epiphyses have ossified, and before the bones have commenced to become brittle; and it is much more common in men than in women. It is invariably the result of severe violence, the limb at the moment being in such a position that the ligaments are on the stretch and the muscles taken at a disadvantage. The head of the femur usually leaves the joint at the lower and back part, where the socket is most shallow and the ligaments weakest. The ligamentum teres is almost always torn from its femoral attachment, and one or more of the muscles inserted in the region of the trochanters may be ruptured. The [inverted Y]-shaped ligament, on the other hand, is seldom torn, and so long as it remains intact the dislocation belongs to one or other of the types above named. All atypical dislocations, such as the supra-cotyloid, infra-cotyloid, ilio-pectineal, are due to rupture of some part of the [inverted Y]-ligament, and are so rare as not to call for individual description. The central dislocation of German authors, in which the head is driven through the floor of the acetabulum, is described on [page 126].