ay be complicated by
laceration of muscles, blood vessels, or nerves, or by fracture of one
or other of the bones in the vicinity.

#Dislocation on to the Dorsum Ilii.#--This, the commonest form of
dislocation of the hip, is usually the result of the patient falling
from a height, or receiving a heavy weight on the back while stooping
forward with the thigh flexed, slightly adducted, and rotated
medially. It is also said to have occurred from muscular action. The
shaft of the femur acts as the long limb of a lever of which the neck
is the short limb, the femoral attachment of the [inverted Y]-ligament
forming the fulcrum. The head, thus brought to bear upon the lower and
back part of the capsule, tears it and leaves the socket, passing
upwards and coming to rest on the dorsum of the ilium, above and
anterior to the tendon of the obturator internus (Fig. 73). The
articular surface is directed backward, while the trochanter looks
forward.

[Illustration: FIG. 72.--Dislocation of Right Femur on to Dorsum
Ilii.]

_Clinical Features._--The affected limb is flexed, adducted, and
inverted, so that the knee crosses the lower third of the opposite
thigh, and the ball of the great toe lies on the dorsum of the sound
foot. There is shortening to the extent of from 1-1/2 to 2 inches, the
trochanter being displaced above Nelaton's line, and lying nearer to
the anterior superior iliac spine than on the normal side. The patient
is unable to move the limb or to bear weight upon it; abduction and
lateral rotation are specially painful; and traction fails to restore
the limb to its proper length. On making these attempts a
characteristic elastic resistance is felt.

The head of the femur in its new position may sometimes be felt
through the fibres of the gluteus maximus, but swelling of the soft
parts often obscures this sign. The normal depression behind the
great trochanter is lost, the gluteal fold is raised, and there is
often a degree of lordosis which compensates for the flexion. The
fingers can be pressed more deeply into Scarpa's triangle on the
dislocated than on the normal side--a point in which this injury
differs from fracture of the base of the neck of the femur.

In a certain number of cases the lateral limb of the [inverted
Y]-ligament is ruptured and the limb is everted--_dorsal dislocation
with eversion_.

[Illustration: FIG. 73.--Dislocation on to Dorsum Ilii. Note relation
of neck of femur to tendons of obtura