ure too
early, or to a progressive softening of the injured vertebra and of
the bodies of those adjacent to it. This leads to an alteration in the
shape of the affected bones, which can be demonstrated by means of the
X-rays. The usual history is that some considerable time after the
patient has resumed work he suffers from pain in the back, and
radiating pains round the body and down the legs. He becomes more and
more unfit for work, and a marked projection appears in the back and
may come to involve several vertebrae. While the condition is
progressive, the prominent vertebrae are painful and tender. In course
of time the softening process is arrested, and the affected bones
become fused, so that the area of the spine involved becomes rigid and
permanent deformity results. So long as the condition is progressive
the patient should be kept in the recumbent and hyper-extended
position over a roller-pillow and, when he gets up, the spine should
be supported by a jacket.

#Dislocation and Fracture-Dislocation.#--It is seldom possible at the
bedside to distinguish between a complete dislocation of the spine and
a fracture-dislocation. _Fracture-dislocation_ is by far the more
common lesion of the two, and is the injury popularly known as a
"broken back." It may occur in any part of the column, but is most
frequently met with in the thoracic and thoracico-lumbar regions. It
usually results from forcible flexion of the spine, as, for example,
when a miner at work in the stooping posture is struck on the
shoulders by a heavy fall of coal. The spine is acutely bent, and
breaks at _the angle of flexion and not at the point struck_. The
lesion consists in a complete bilateral dislocation of the articular
processes, together with a fracture through one or more of the bodies.
This fracture is usually oblique, running downwards and forwards. The
upper fragment with the segment of the spine above it is displaced
downwards and forwards, and the cord is crushed between the posterior
edge of the broken body and the arch of the vertebra above it (Fig.
208). In almost every case the cord is damaged beyond repair.

[Illustration: FIG. 208.--Fracture--Dislocation of Ninth Thoracic
Vertebra, showing downward and forward displacement of upper segment,
and compression of cord by upper edge of lower segment.

(Anatomical Museum, University of Edinburgh.)]

_Total dislocation_, in which the articular processes on both sides
are displaced a