recovered with dislocation on to the
dorsum ilii is usually able to walk and run about, but with a limp or
waddle which becomes more pronounced as he grows up. The condition
closely resembles a congenital dislocation, but the history, and the
presence of gross alterations in the upper end of the femur as seen
with the X-rays, should usually suffice to differentiate them.

_Treatment._--In the acute stage the limb is extended by means of the
weight and pulley, and kept at rest with the single or double long
splint, or by sand-bags. If there is suppuration, the joint should be
aspirated or opened by an anterior incision, and Murphy's plan of
filling the joint with formalin-glycerine may be adopted. In children,
it is remarkable how completely the joint may recover.

If there is dislocation, the head of the femur should be reduced by
manipulation with or without preliminary extension; it has been
successful in about one-half of the cases in which it has been
attempted. Preliminary tenotomy of the shortened tendons is required
in some cases. When reduction by manipulation is impossible, the joint
structures should be exposed by operation and the head of the bone
replaced in the acetabulum. When the upper end of the femur has
disappeared, the neck should be implanted in the acetabulum, and the
limb placed in the abducted position.

#Arthritis Deformans.#--This disease is comparatively common at the
hip, either as a mon-articular affection or simultaneously with other
joints.

[Illustration: FIG. 119.--Arthritis Deformans, showing erosion of
cartilage and lipping of articular edge of head of femur.]

_The changes in the joint_ are characteristic of the dry form of the
disease, and affect chiefly the cartilage and bone. The atrophy and
wearing away of the articular surfaces are accompanied by new
formation of cartilage and bone around their margins. The head of the
femur may acquire the shape of a helmet, a mushroom, or a limpet
shell, and from absorption of the neck the head may come to be sessile
at the base of the neck, and to occupy a level considerably below that
of the great trochanter (Fig. 120). These changes sometimes extend to
the upper part of the shaft, and result in curving of the shaft and
neck, suggesting a resemblance to a point of interrogation (Fig. 121).
The acetabulum may "wander" backwards and upwards, as in tuberculous
disease. It is usually deepened, and its floor projects on the pelvic
aspect; its