may usually be determined by the
use of the X-rays. In performing the operation, care must be taken to
disturb the periosteum as little as possible, otherwise there may
follow excessive formation of new bone.

Operative interference is sometimes necessary for ankylosis or locking
of the joint after the fracture is united, or to relieve the ulnar
nerve when it is involved in callus. _Volkmann's ischaemic contracture_
is liable to occur after fractures in the region of the elbow from
impairment of the blood supply as a result of tight bandaging.

FRACTURE OF THE UPPER END OF THE ULNA

#Fracture of the olecranon# is a comparatively common injury in
adults. It usually follows a fall on the flexed elbow, and results
from the direct impact, supplemented by the traction of the triceps
muscle. In a few cases it has been produced by muscular action alone.
The line of fracture may pass through the tip of the process, or
through its middle, less frequently through the base. It may be
transverse, oblique, T- or V-shaped, but is rarely comminuted or
compound.

_Clinical Features._--As the fracture almost invariably implicates the
articular surface, there is considerable swelling from effusion of
blood into the joint. The power of extending the forearm is impaired,
and other symptoms of fracture are present. The amount of displacement
depends upon the level of the fracture, and the extent to which the
aponeurotic expansion of the triceps is torn. As the fracture is
usually near the tip, the displacement is comparatively slight, the
prolongation of the fibres of insertion of the triceps on to the sides
and posterior part of the process holding the small fragment in
position; and the fracture may easily escape recognition. When the
line of fracture is nearer the base, however, the contraction of the
triceps tends to separate the fragments widely (Fig. 35), and a
distinct gap, which is increased on flexing the elbow, may often be
felt between them, and if the elbow is passively extended, the
fragments may be brought into apposition, and crepitus elicited.

[Illustration: FIG. 35.--Radiogram of Fracture of Olecranon Process,
showing marked degree of displacement.

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

When there is little displacement, bony union may result, but in many
cases the fragments are united only by fibrous tissue. The upper
fragment sometimes forms attachments to the shaft of the humerus, and
this l