that is, deviation towards the radial side; but it may
follow a direct blow on the back of the humerus, a fall on the elbow,
or a twist of the forearm.

[Illustration: FIG. 36.--Backward Dislocation of Elbow, in a boy aet.
10, caused by a fall off a wall, landing on the elbow.]

_Morbid Anatomy._--All the ligaments of the elbow, except the annular
(orbicular), are torn or stretched. The radius and ulna pass backward,
the coronoid process coming to rest opposite the olecranon fossa
behind the humerus, and the head of the radius behind the lateral
condyle. The condyles of the humerus bear their normal relations to
one another. The olecranon and the triceps tendon form a marked
prominence on the back of the elbow, the tip of the olecranon lying
above and behind the condyles. The lower end of the humerus lies in
the flexure of the joint with the biceps tendon tightly stretched over
it. The coronoid process is often broken, or the tendon of the
brachialis torn. The median and ulnar nerves may be stretched or torn.
Not infrequently the bones of the forearm are displaced towards the
medial side as well as backward.

Occasionally, as a sequel to the dislocation, processes of bone
develop in relation to the insertion of the brachialis and interfere
with the movements of the joint. These outgrowths are due to
displacement of bone-forming elements, either at the time of the
original injury or as a result of forcible efforts at reduction.
According to D. M. Greig, they do not develop in the tendon of the
brachialis, but under it, and are not of the nature of myositis
ossificans. In from four to six weeks after reduction of the
dislocation, the movements begin to be restricted, and a hard mass can
be felt in the cubital fossa, which with the X-rays is seen to be a
bony outgrowth springing from the quadrilateral space on the front of
the elbow below the coronoid process (Fig. 37). This gradually
increases in size and leads to fixation of the joint. In most cases
the effects reach their maximum in about six months, and then
reabsorption of the mass begins.

[Illustration: FIG. 37.--Bony Outgrowth in relation to insertion of
Brachialis Muscle, following Backward Dislocation of Elbow.

(Sir Robert Jones' case. Radiogram by Dr. D. Morgan.)]

If the disability shows no sign of abatement within a year, or if the
bony outgrowth is producing pressure effects on the median nerve, it
should be removed by operation.

It is important no