s more before he is able to resume active employment.

The #acetabulum# may be fractured by force transmitted through the
femur, usually from a fall on the great trochanter, less frequently
from a fall on the feet or other form of violence. It may merely be
fissured, or the head of the femur may be forcibly driven through its
floor into the pelvic cavity, either by fracturing the bone or, in
young subjects, by bursting asunder the cartilaginous junction of the
constituent bones. When the femoral head penetrates into the
pelvis--the _central dislocation of the hip_ of German writers--the
condition simulates a fracture of the neck of the femur, but the
trochanteric region is more depressed and the trochanter lies nearer
the middle line. The limb is shortened, and movements of the joint are
painful and restricted, especially medial rotation. In some cases
there is pain along the course of the obturator nerve.

On rectal or vaginal examination there is localised tenderness over
the pelvic aspect of the acetabulum, and in some cases a convex
projection, or even crepitating fragments can be detected. The
diagnosis is completed by an X-ray picture.

When the head of the femur penetrates the acetabulum, reduction should
be attempted by traction and manipulation. The pelvis is held rigid,
and the thigh is flexed and forcibly adducted, while the medial side
of the thigh rests against a firm sand-bag; the femoral head is thus
lifted out of the pelvis. In a recent injury the amount of force
required is relatively slight. The head is kept in its corrected
position by extension.

Fracture of the _upper and back part of the rim_ of the acetabulum may
accompany or simulate dorsal dislocation of the hip. Crepitus may be
present in addition to the symptoms of dislocation, and after
reduction the displacement is easily reproduced. The treatment is by
extension with the limb adducted.

#Fracture of Individual Bones of the Pelvis.#--_Ilium._--The expanded
portion of the iliac bone is often broken by direct violence, the
detached fragments varying greatly in size and position (Fig. 56).

The whole or part of the _crest_ may be separated by similar forms of
violence.

When the fracture implicates the _ala_ of the bone, it usually starts
at the triangular prominence near the middle of the crest, and runs
backwards or forwards, passing for a variable distance into the iliac
fossa. The displaced fragment can sometimes be palpated and mad