bones of the forearm are those most frequently the seat of greenstick
fracture (Fig. 41). _Fissures_ occur on the flat bones of the skull,
the pelvic bones, and the scapula; or in association with other
fractures in long bones, when they often run into joint surfaces.
_Depressions_ or indentations are most common in the bones of the
skull.

The bone at the seat of fracture may be broken into several pieces,
constituting a _comminuted_ fracture. This usually results from severe
degrees of direct violence, such as are sustained in railway or
machinery accidents, and in gun-shot injuries (Fig. 2).

[Illustration: FIG. 2.--Radiogram of Comminuted Fracture of both Bones
of Forearm.]

_Sub-periosteal_ fractures are those in which, although the bone is
completely broken across, the periosteum remains intact. These are
common in children, and as the thick periosteum prevents displacement,
the existence of a fracture may be overlooked, even in such a large
bone as the femur.

A bone may be broken at several places, constituting a _multiple_
fracture (Fig. 1).

_Separation of bony processes_, such as the coracoid process, the
epicondyle of the humerus, or the tuberosity of the calcaneus, may
result from muscular action or from direct violence. _Separation of
epiphyses_ will be considered later.

(2) _According to the Direction of the Break._--_Transverse_ fractures
are those in which the bone gives way more or less exactly at right
angles to its long axis. These usually result from direct violence or
from end-to-end pressure. _Longitudinal_ fractures extending the
greater part of the length of a long bone are exceedingly rare.
_Oblique_ fractures are common, and result usually from indirect
violence, bending, or torsion (Fig. 3). _Spiral_ fractures result from
forcible torsion of a long bone, and are met with most frequently in
the tibia, femur, and humerus.

[Illustration: FIG. 3.--Showing (1) Oblique fracture of Tibia; (2)
Oblique fracture with partial separation of Epiphysis of upper end of
Fibula; (3) Incomplete fracture of Fibula in upper third. Result of
railway accident. Boy aet. 16.]

(3) _According to the Relative Position of the Fragments._--The bone
may be completely broken across, yet its ends remain in apposition,
in which case there is said to be _no displacement_. There may be an
_angular_ displacement--for example, in greenstick fracture. In
transverse fractures of the patella or of the olecranon there