HIDDEN FLEXION INJURY OF THE CERVICAL SPINE
J. K. WEBB, R. B. K. BROUGHTON, T. MCSWEENEY and W. M. PARK, OSwEsTRY, ENGLAND
From the Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry, Shropshire
This paper describes seven patients who developed late vertebral deformity after fiexion injuries of the
cervical spine. In four the clinical and radiological features were subtle and because the patients walked into
an emergency department the severity of the injury was not initially appreciated. Certain specific clinical and
radiological features of flexion injury are described and emphasis is placed on the importance of correct
management. A radiological tetrad is described which should alert the surgeon to the possibility of damage
to the posterior interspinous complex of the cervical spine and so lead to further radiological investigations.
Despite the frequency of flexion injuries the alarming complications described in this paper are rare.
Flexion injury of the cervical spine and the mecha- sixteen and a half years. At the time of injury, tetraplegia
nism involved are well documented (Davis 1945 ; Roaf was complete in one patient and incomplete in another;
1960 ; Holdsworth 1963 ; Cheshire 1969 ; Braakman and a third patient had suffered transient tetraparesis.
Penning 1971), but few have noted the subtle changes of
flexion injury to the cervical spine which, if unrecognised
and untreated, may lead to late displacement with pos-
sibly disastrous consequences. The flexion injuries studied in this paper are anterior
subluxations and the radiological features, we believe,
indicate disruption of the posterior cervical complex. The
posterior cervical complex consists of the posterior articu-
Seven patients have been selected for this paper because lations stabilised by the capsule, intraspinous and supra-
the full extent of the damage to the posterior interspinous spinous ligaments and the ligamenta flava. The difficulty
complex was not initially apparent (Table I). No patient is to decide whether the lesion is complete and unstable
with overt fracture or dislocation is included. There were or whether there is only a partial tear, without instability
five males and two females, and their average age was (Figs. 1 and 2).
CLINIcAL INFORMATION CONCERNING SEVEN PATIENTS WITH FLEXION INJURY OF THE CERVICAL SPINE
anterior vertebral Neurological state
Case Age Type of Level of compression
number (years) Sex injury subluxation fracture Physical signs Initial Late Complications
I 20 Female Road traffic C.5-6 C.6 Pain and spasm Pain and instability
2 16 Female Road traffic C.4-5, C.6 Pain and spasm Pain and instability
3 20 Male Rugby C.5-6 C.7 Pain and spasm Pain and instability
4 20 Male Rugby C.4-5 C.5 and C.6 Pain and spasm Transient Full Late intervertebral
tetraparesis recovery displacement
5 14 Male Somersaulted C.3-4 C.4, C.5 and C.6 Pain and spasm Late vertebral
on ground deformity
6 14 Male Wrestling C.3-4 C.4 and C.5 Pain and spasm Complete No Late vertebral
tetraplegia improvement deformity
7 12 Male Trampoline C.3-4 C.4, C.5 and C.6 Pain and spasm Transient Full Late vertebral
tetraparesis recovery deformity
J. K. Webb, F.R.C.S., Senior Registrar, The Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry, Shropshire SYIO 7AG, England.
Dr R. B. K. Broughton, B.Ch., D.M.R.D., Lecturer in Radio-diagnosis, Welsh National School of Medicine Postgraduate Medical Centre,
Heath Park, Cardiff CF4 4XN, Wales.
T. McSweeney, M.Ch., M.Ch.Orth., F.R.C.S., Surgeon in Charge, Spinal Injuries Unit, The Robert Jones and Agnes Hunt Orthopaedic
Hospital, Oswestry, Shropshire SY1O 7AG, England.
Dr W. M. Park, Ch.B., F.R.C.R., Director of Radiology, The Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry, Shropshire
Sylo 7AG, England.
322 THE JOURNAL OF BONE AND JOINT SURGERY
HIDDEN FLEXION INJURY OF THE CERVICAL SPINE 323
There are four characteristic radiological signs that Persistent instability with pain-Three patients (Table I,
suggest posterior cervical complex damage. Two of these Cases 1 to 3) presented with flexion injuries and the
occur at the level of the injury but two are associated radiographs were considered to be normal. These patients
features affecting other parts of the cervical spine. This continued to suffer neck pain. Radiographs at a later
radiological tetrad has been seen in the seven cases dis- stage revealed obvious disruption of the posterior inter-
cussed in this paper. spinous complex. The first patient continued to have
Localised features- Widening of the interspinous space- discomfort in the neck for nine months after the injury,
This is recognised by isolated and wide separation of the and at this stage lateral flexion and extension radiographs
interspinous processes at the level of the injury. The space revealed increasing instability in the cervical spine. In
FIG. 1 FIG. 2
Complete (Fig. I) and partial tears of the posterior cervical complex. Note : I) widening of the interspinous space ; 2) intervertebral
subluxation with opening of the apophysial joints; 3) vertebral compression fracture; and 4) loss of cervical lordosis.
is wide in comparison with that at other intervertebral the other two cases instability was evident at three and
levels and it persists in extension. six months after injury.
Intervertebral subluxation-Partial overriding of the apo-
physial joints permits forward and angular intervertebral CASE REPORT
displacement. The degree of abnormal movement will
Case 1-A woman aged twenty was injured when a passenger
be most evident in a radiograph taken with the neck in in a car that hit a tree. She complained of pain in the neck,
flexion. and examination showed spasm and restriction of movement.
Associated features- Vertebral compression fracture- Radiographs suggested subluxation of the fifth cervical ver-
This fracture may be subtle and only evident as a minor tebra on the sixth (Fig. 3) although these had been initially
regarded as normal in the hospital that she first attended. The
protrusion from the upper anterior aspect of the vertebral
wearing of a plaster collar for three months did not relieve
body. In three cases, two vertebrae were affected. The the pain. Radiographs later revealed instability (Fig. 4) and
compression fracture is not necessarily at the level of the posterior fusion was performed nine months after injury.
injury ; indeed it is usually below it. It may be accom-
Late intervertebral displacement-One patient came into
panied by a minor degree of widening of the pre-vertebral
Loss of normal cervical lordosis-Paraspinous muscle CASE REPORT
spasm leads to loss of the normal lordotic curve and will Case 4-A nineteen-year-old man was hit on the head from
behind during a game of rugby. He showed tetraparesis, and
also cause marked limitation of movement particularly
radiographs showed anterior subluxation of the fourth car-
vical vertebra on the fifth (Fig. 5). He was treated with skull
traction for three months and thereafter was in a Minerva
LATE COMPLICATIONS OF jacket for a further three months. Complete neurological
recovery occurred. At this stage, lateral radiographs taken in
flexion and extension were reported as normal (Fig. 6). Four
Three types of complication were seen after severe flexion months later he attended, unable to hold his head erect, and
injury in this small group of patients : 1) persistent insta- radiographs revealed complete dislocation of the fourth car-
vical vertebra on the fifth (Fig. 7).
bility with pain (three cases) ; 2) late intervertebral dis-
placement (one case) ; and 3) late vertebral deformity Comment-The lateral projections taken in flexion and
(three cases). extension six months after the injury to assess the stability
VOL. 58-B, No. 3, AUGUST 1976
324 J. K. WEBB, R. B. K. BROUGHTON, T. MCSWEENEY AND W. M. PARK
FIG. 3 FIG. 4
Case 1. Figure 3-Lateral radiographs of the cervical spine in extension and flexion, initially regarded as normal. Figure 4-Lateral
radiographs of the same spine six months later, in extension and flexion, showing anterior subluxation at the C.5-6 level.
of the cervical spine were considered normal. It was not CASE REPORT
appreciated at that time that spasm severely restricted Case 5-A fourteen-year-old boy somersaulted and landed on
flexion. In retrospect, we would consider these flexion the back of his neck. There was pain, spasm and restriction
ofmovement. Radiographs, including lateral projections taken
views as unacceptable and would undertake further
in flexion and extension, were considered normal (Fig. 8).
flexion strain views under heavy sedation. He presented six months later with a severe kyphosis but
Late vertebral deformity-Three very similar cases (Table without symptoms (Fig. 9).
I, Cases 5 to 7), all in patients aged between twelve and
Comment-The radiographs taken on arrival, although
fourteen years, were studied in this department. One
reported as normal, definitely show the radiological tetrad
child was tetraplegic, another was tetraparetic and the
suggesting damage to the posterior complex.
third walked into the casualty department complaining
of pain in the neck after a fall. The lateral radiographs
taken in flexion and extension in the last two cases were
MANAG EM ENT
reported normal and the patients were observed later as
out-patients. It was four and six months after injury Our method of treating flexion injury of the cervical spine
that the severity of the damage was fully appreciated. without overt fracture or dislocation has been modified
Review of all the original films showed the radiological in the light of experience gained from the cases described
signs of instability of the posterior elements. in this paper.
FIG. 5 FIG. 6 FIG. 7
Case 4. Figure 5-Lateral radiograph of the cervical spine showing minimal anterior subluxation at the C.4-5 level. Figure 6-Radio-
graphs six months later in extension and flexion. Flexion is severely restricted and the radiological tetrad is visible. Figure 7-One year
following injury the radiograph shows severe vertebral displacement.
THE JOURNAL OF BONE AND JOINT SURGERY
HIDDEN FLEXION INJURY OF THE CERVICAL SPINE 325
A patient who has sustained direct or indirect violence and radiological examination must be performed meticu-
to the head or cervical spine is examined for signs of lously so that all signs, however subtle, will be recognised.
injury, in particular, spasm and pain on neck movement. If the radiological tetrad is present a decision must be
All patients undergo a standard radiographic examination made about the integrity of the posterior interspinous
of the cervical spine which includes anterior-posterior and complex. If this is completely disrupted and instability
lateral radiographs and trans-oral views of the dens. If is recognised, the patient is at risk of late complications.
these three radiographs reveal no fracture or dislocation, If a partial disruption is present and the spine is stable,
then lateral radiographs in flexion and extension are taken late complications do not occur. Fusion at the involved
and examined for any abnormal features-in particular, level or levels should be considered in the presence of
widening of the interspinous space, intervertebral sub- complete disruption of the posterior cervical complex.
luxation, vertebral compression fracture and loss of the In the interpretation of cervical spinal injury it is
normal lordotic curve or limitation of flexion. often hard to decide whether radiographic appearances
FIG. 8 FIG. 9
Case 5. Figure 8-Lateral radiographs of the cervical spine of a child in extension and flexion, showing
the radiological tetrad. Figure 9-Radiograph taken six months later shows severe deformity.
If there is limitation of movement or suggestion of are normal. The normal cervical spine is lordotic in the
instability of the cervical spine a collar is provided. A neutral position. Hadley (1944), Davis (1945) and Nagle
few days later, further fiexion and extension films are (1957) reported that the cervical spine was straight after
taken. If movement is restricted, and particularly if the minor injury without ligament damage. On the other
radiological signs previously described are present, it is hand, Juhl, Miller and Roberts (1962), Fineman, Borrelli,
essential to assess whether the cervical spine is unstable. Rubinstein, Epstein and Jacobson (1963) and Cattell and
The neck is subject to strain while under vision with the Filtzer (1965) found that the cervical spine could be
image intensifier. If spasm restricts the range of move- straight, kyphotic and angulated in a proportion of
ment the examination is repeated with the patient well patients without any history of trauma. In our small
relaxed by sedation. General anaesthesia has not been group there was no doubt that the cervical spine was
necessary in any of our cases. The surgeon must see the damaged. The difficulty in three instances (Table I, Cases
interfacetal joints while flexing and extending the neck. I to 3) was in deciding whether or not there was complete
If instability is recognised, the segments involved should destruction of the posterior cervical complex.
be fused. Discography has been done : it may provide Spasm is an important physical sign associated with
further information about the number of segments in- restriction ofmovement. Hubbard (1974) describing injury
volved (Fig. 10). of the cervical spine in children and adolescents found
spasm in 42 per cent of patients with unstable injuries.
In every patient in the present series, the presence of
spasm could be deduced in lateral flexion and exten-
Flexion injury of the cervical spine is relatively common, sion radiographs by loss of normal lordotic curvature
but the complications described in this paper are rare. and marked decrease in the range of total cervical move-
The diagnosis of flexion injury may be difficult: clinical ment. Limitation of cervical motion or angular kyphosis
VOL. 58-B, No. 3, AUGUST 1976
326 J. K. WEBB, R. B. K. BROUGHTON, T. MCSWEENEY AND W. M. PARK
of the cervical spine may be produced if the patient flexes tenor ligament complex has been ruptured, healing such
and extends incorrectly (Juhl et al. 1962; Fineman et al. as to restore the original strength does not occur”.
1963). The correct method of flexing and extending the Although some might disagree with this statement, it is
head must, therefore, be demonstrated to every patient. a safe concept with which to initiate the management of
If movement is restricted and the other features of the cervical injury. We have found that strain views enable
radiological tetrad are present, it is important to see the us to identify the unstable posterior cervical complex
effect of strain on the cervical spine under vision with the through marked interspinous opening and forward sub-
image intensifier. luxation, particularly of the apophysial joints (Fig. 1 1).
The recommendation regarding strain views may be Since we have been aware of this clinical entity, a number
controversial. Holdsworth (1963) stated “when the pos- of patients have presented with similar radiological signs
FIG. 10 FIG. 11
Figure lO-Discograph showing disruption of a disc one level below the level of visible subluxation. Figure 1 F-Strain views of
a cervical spine showing severe subluxation at a level C.5-6 previously suspected of injury. The patient was heavily sedated
but the strain views have not always shown increasing
intraspinous widening or forward subluxation. The fre-
quency with which the latter group of patients have
appeared suggests to us that the incomplete type of lesion
is more common than the very rare complete rupture.
The patients with incomplete rupture have now been
followed for an average of eighteen months and have not
developed any of the complications described in this paper.
Operative fusion was performed in five patients. A
posterior approach was preferred for a number of
reasons ; in particular because the extent of the injury
could be assessed and the necessary length of fusion
determined. Anterior cervical fusion is a relatively easy
procedure and most workers claim a high success rate
(Cloward 1958; Robinson, Walker, Ferlic and Wiecking
FIG. 12 1962; Connolly, SeymourandAdams 1965; Simmons and
Section of the posterior interspinous ligamentshowing disruption Bhalla 1969), but where an attempt is made to fuse more
of the normal architectural pattern of the collagen fibres. ( x 100.) than one segment the failure rate is significantly higher
(a) Normal collagen fibres. (b) Pale staining degenerate collagen
fibres. (Cloward 2 per cent, Robinson 12 per cent, Connolly
THE JOURNAL OF BONE AND JOINT SURGERY
HIDDEN FLEXION INJURY OF THE CERVICAL SPINE 327
21 per cent). It may be argued that an anterior approach spinous ligament and it was found that in each case the
could weaken the vertebral complex still further, par- normal architectural pattern of the fibres had been dis-
ticularly if the graft is absorbed or extruded. Simmons rupted. An example of the histological findings is shown
and Bhalla (1969) showed experimentally that anterior in Figure 12. Degenerate collagen and excessive fibrous
keystone grafts were extruded when disruption of the tissue can be seen. All the posterior fusions have been
posterior cervical complex was produced on a stress successful and the patients are now asymptomatic with
machine. no significant limitation of movement after an average
Operation confirmed damage to the posterior inter- follow-up of twenty months.
It is a great pleasure to record our gratitude to Mr D. Jones of the Photography Department, Institute of Orthopaedics, for the illustrations.
Braakman, and Penning, L. (1971) injuries of the Cervical
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