C Fractures and Dislocations of the
Vertebral Column
CHAPTER 10
MECHANISMS OF SPINAL FRACTURES
The vertebral column may be subjected to a wide variety or combination of stresses
resulting in dislocation, fracture and fracture-dislocation. Mechanism and classification
of injuries of the spinal column, with and without cord or spinal root involvement, have
been repeatedly discussed in the old and recent literature (Wagner & Stolper, 1898;
Jefferson, 1920-40; Bohler, 1937, 1963; Barnes, 1948, 1961; Taylor & Blackwood,
1948; Watson-Jones, 1950; Taylor, 1951; Schneider
et al.,
1954; Roaf, 1960; 1971;
Kahn, 1959; Witley & Forsyth, 1960; Zettel, 1962; Brocher, 1965-66, 1971; Forsyth &
Winston-Salem, 1964; Guttmann, 1931-71; Holdsworth, 1963; Petrie, 1964; Munro,
1966; Kuhlendahl, 1966; Bedbrook, 1969, 1971; Frankel
et at.,
1969; Cheshire, 1969;
Burke, 1971; Mayer & Peters, 1971; Braakman & Penning, 1971). However, views still
differ on various aspects. This is understandable, as the forces generated by the impact of
the violence causing vertebral and cord injuries produce not merely displacement of the
spine in one direction but often any combination of upward, forward, backward, lateral
and rotational movements. This is particularly true in accidents where the injured is
hurled violently from some position and finally lands against hard surfaces (hurling
mechanism). Moreover, there is still disagreement in the definition of stable and unstable
fractures, and the criteria used differ considerably. This, inevitably, has its consequences
on the initial management of spinal fractures and dislocations. The recent introduction
of the term 'Potential Instability' (Bedbrook, 1970) may not contribute to diminish the
confusion. In fact, it may give 'dynamic' or inexperienced surgeons an excuse to rush
immediately into unnecessary and useless operative procedure for internal stabilization.
Beatson (1963), in his excellent review, showed how difficult it is in the cervical spine to
be certain of cases which will prove pathologically unstable. Data given in the literature
on instability vary considerably. Gallic (1939), Ellis (1946), Durbin (1957) and others
report 10-12 per cent. In Cheshire's series (1969) of 257 cervical fractures, the late
instability rate varied between 4-8 and 7-3 per cent in all main groups. The high percen–
tage (21 per cent) of instability in his series of 19 cases of anterior subluxation is unusual.
In Bedbrook's cases (1970), the late instability was 6 per cent. In 37 cervical injuries,
published recently by Burke & Berryman (1971), three (8 per cent) showed late instability
following conservative treatment requiring surgical fusion. None showed neurological
deterioration because of the delay in fusion. In a series of 612 fractures of various levels
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