olence, such as the passage of a wheel over the limb or
a severe blow, the bones give way at the point of impact, and the line
of fracture tends to be transverse, both bones being broken at the
same level (Fig. 89). There is little or no displacement, and such as
there is is angular, and is determined by the direction of the
fracturing force.

[Illustration: FIG. 89.--Radiogram of Transverse Fracture of both
Bones of Leg by direct violence.]

When the violence is _indirect_, as from a fall on the feet, or a
twist of the leg, the tibia usually gives way at the junction of its
lower and middle thirds, and the fibula at a higher level (Fig. 90).
Torsion of the tibia is probably the most important factor in the
production of the fracture, the distal fragment being fixed by the
pressure of the foot upon the ground, while the proximal fragment is
rotated by the impetus of the body. Both fractures are usually
oblique--that in the tibia running from above downward, forward, and
medially, and it is generally found that the obliquity of the fibular
fracture corresponds with that in the tibia.

[Illustration: FIG. 90.--Radiogram of Oblique Fracture of both Bones
of Leg by indirect violence.]

There is usually considerable displacement, the weight of the lower
portion of the limb causing it to fall backwards and to roll away from
the middle line, and the traction of the calf muscles pulling up the
heel and pointing the toes. The proximal fragment forms a projection
on the front of the limb.

On account of the superficial position of the tibia and the pointed
character of the fragments, this fracture is frequently rendered
compound by the bone being forced through the skin. The projecting
piece of bone is usually the distal end of the proximal fragment. This
fracture is often comminuted. It has been observed that when the line
of fracture forms the letter V on the subcutaneous surface of the
tibia, there is invariably a fissure passing down along the back of
the bone into the ankle-joint--a complication which adds to the risk
of subsequent stiffness and impaired usefulness of the limb. Apart
from this, the ankle is usually sprained in fractures by indirect
violence, and we have frequently found the superior tibio-fibular
articulation torn open in severe fractures of both bones of the leg
from indirect violence.

_Clinical Features._--The tibial fracture is readily recognised by
detecting an irregularity on running the finger