larity in the outline of the front of the column recognizable by palpation through the soft parts. The head may be rigidly fixed, or, more rarely, freely movable. These differences depend partly on the position of the dislocated bone, the presence or ab

sence of associated fracture, and the extent of the injury to the connecting ligaments, partly on the direction and character of the dislocating force, and partly on the contraction or relaxation of the muscles which control the position taken by the unaffected joints above the seat of injury. In the majority of cases the head is bent forward, and an angle with its apex directed backward is formed by the two segments above and below the dislocation. Attempts to move the head and pressure at the seat of injury are very painful. In these patients the irregularity in the line of the transverse processes may also be recognized by the touch; and if the dislocation is not too low the projection of the body of the vertebra may be felt in the pharynx.

FIG. 31.

Of the symptoms of bilateral dislocation backward nothing positive can be said. In most of the supposed cases the head has been bent backward, the face directed somewhat upward, the tissues of the front of the neck tense, and respiration and deglutition somewhat interfered with.

Paralysis, partial or complete, is frequently observed. Its immediate importance, its urgency, as a symptom varies accordingly as the dislocated joint is above or below the point of exit of the phrenic nerve. The fourth cervical nerve, from which the phrenic mainly arises, though it receives a branch also from the third or fifth, leaves the vertebral canal through the foramen between the third and fourth vertebræ, but leaves the side of the cord at a somewhat higher point. A dislocation below the third cervical vertebra may cause paralysis of all the accessory muscles of respiration that act by raising the ribs, but, the diaphragm continuing to act, prolongation of life is possible. If, on the other hand, the dislocation is at a higher point, and the trunks going to form the phrenic nerve are injured or the cord is so compressed or torn that the integrity of the corresponding fibres within it is destroyed, or they are all cut off from the respiratory centre, then the diaphragm also, being no longer innervated by these nerves, immediately ceases to act, and the individual dies asphyxiated. In a few cases the threatening symptoms have been instantly relieved by changing the position of the patient or by systematic reduction of the dislocation. In all such threatening

cases and in those that have been immediately fatal the injury is, as a rule, at one of the upper joints. In the exceptions there have been associated injuries to which the death is to be attributed.

If the paralysis is due to compression or laceration of the cord it may be complete of both motion and sensation below the point of injury, or it may involve only the motor nerves. It seems probable that the partial paralyses are due to pressure not upon the cord but upon a nerve trunk in the intervertebral foramen.

Loss of control over the sphincters, incontinence of urine, and the other secondary symptoms of injury to the cord have been already considered.

Prognosis.-The mortality of dislocations of the lower six cervical vertebræ, excluding cases of diastasis, is, according to Blasius, fifty-six per cent., or, excluding all doubtful cases, sixty-six per cent. This estimate is open to the serious objection that it rests upon a principle of selection which views with suspicion every diagnosis that is not verified by post-mortem examination. Since there is good ground for this suspicion in many cases and no better alternative method of selection is practicable, it seems better to assume that the percentage cannot at present be determined. According to the same statistics the mortality is greatest, 88.4 per cent., in the double dislocation forward, while that of the unilateral forward sinks to 34.9 per cent. In the fatal cases death, as a rule, comes promptly, within the first week. Suppuration has been observed about the seat of injury in cases that remained unreduced.

Treatment. In unilateral dislocation forward, at least in those produced by muscular action, Völker says reduction is usually easy and free from danger. Mention has been made above of the case in which a boy reduced his own dislocation by resting his head and shoulder against a wall and pressing upon the prominence in the neck with his thumb.

Simple traction upon the head, the counter-extension being made by the weight of the body, followed by rotation of the face toward the dislocated side has proved successful, but it seems better and is generally recommended that the articular process should be freed by still further abducting the head and upper segment of the column (away from the side of the dislocation), and then, when freed, should be rotated backward into place. If traction is used it should be made in the direction of the long axis of the upper segment, not in that of the lower one, for in the latter case the strain would come wholly or mainly upon the untorn connections on the non-dislocated side and rather tend to depress the dislocated articular process still further in front of the corresponding lower one than to raise it above it.

Bilateral dislocations in opposite directions are to be classed with the preceding as dislocations by abduction and rotation, and treated in the same manner. Probably the differential diagnosis could not be made clinically.

In bilateral dislocations forward it has been recommended by Hueter that the reduction should be made first on one side and then on the other by abduction and rotation, as if dealing with two unilateral dislocations forward.

The methods that have been employed with success have combined

traction upon the head, either in the sitting or recumbent posture, with pressure upon the front and back of the neck at suitable points.

After reduction the patient should be kept quiet for some time, and if reproduction of the dislocation is feared a retentive dressing should be applied. It must be rigid enough to prevent any flexion of the neck forward or back, and, after unilateral dislocation, should include the head so as to prevent rotation. Such a dressing might be conveniently made with plaster-of-Paris.

DISLOCATIONS OF THE DORSAL VERTEBRÆ.

The cartilaginous surfaces of the articular processes in the dorsal region are placed more nearly in a vertical plane than those of the cervical vertebræ; the superior ones look backward and slightly upward and outward, the inferior ones, with the exception of those of the twelfth, look forward and slightly downward and inward; the inferior ones of the twelfth are placed like those of the lumbar vertebræ and look outward and somewhat forward. This disposition does not in itself make dislocation to either side by rotation or direct dislocation backward with fracture difficult; dislocation forward is made possible by flexion sufficient to raise the inferior articular processes of the upper vertebræ above the superior ones of the lower. Dislocation between the twelfth dorsal and first lumbar vertebræ seems to be much less favored by the relations of the processes, and yet this is the point in the combined dorsal and lumbar regions where dislocation is by far most common. Blasius (loc. cit., vol. 103, p. 46), collected twenty-two cases in which the character of the dislocation was demonstrated by autopsy; of these one was of the third dorsal vertebræ, three of the fifth, one of the sixth, one of the ninth, three of the tenth, two of the eleventh, and eleven of the twelfth ; of the doubtful cases ten were of the twelfth, four of the eleventh, and one each of the fifth, eighth, and tenth. This greater frequency at the twelfth has been attributed to the greater normal mobility of this joint, but as the mobility is equally great, or even greater, between the lumbar vertebræ where dislocation is much more rare, this explanation is not sufficient. The explanation given by Chas. Bell' of the greater frequency of fractures at the same point seems equally applicable to dislocations; it rests upon the combination of rigid and flexible segments in the column and finds the greatest frequency at the junction of such segments. This is supported by the experiments of Bonnet, who found that forced flexion of the dorso-lumbar column had its maximum effect between the eleventh dorsal and second lumbar, and especially at the first lumbar. Motion between the dorsal vertebræ is limited not only by their relations to each other but also by the attached ribs.

The observed varieties are the bilateral forward and backward with about equal frequency, the bilateral in opposite directions, and the lateral. Of the latter there are only two demonstrated cases, Bell and Mohrenstein, twelfth dorsal, and even in these Blasius thinks the injury was primarily a unilateral dislocation forward or backward, which was

1 Quoted in Fractures, p. 261.

followed by bodily lateral displacement. In the few cases in which the condition of the adjoining ribs is noted, these have been found sometimes dislocated and sometimes fractured not far from the column. The degree of injury to the cord varies with the character and extent of the displacement. Other pathological conditions have been considered above.

The causes have been forcible flexion of the trunk forward and the direct action of great violence upon the back or side of the spinal column, as in the fall of a heavy object, or the passage of the wheel of a wagon across the body.

The symptoms of the dislocation are found in recognizable changes in the position and relations of the dislocated vertebræ, especially in the prominence of its spinous process or of the underlying one, or in its lateral displacement, and in a deviation of the column which creates an angle at the seat of the dislocation, the apex of which is usually directed backward. In some cases it is noted that the articular processes of one or the other of the two adjoining vertebræ form prominences under the skin.

Excessive mobility at the seat of dislocation has also been observed in most cases.

Paralysis appears to be more common and more complete in the forward than in the backward dislocations, and in a few cases has disappeared after reduction.

The symptoms resemble so closely those of fracture that the differential diagnosis, in the absence of post-mortem examination, can rarely be made with certainty. The failure to obtain crepitation is no proof of the absence of fracture, and when present it may be due to the presence of an associated unimportant fracture. Reduction and the absence of a tendency to reproduction of the deformity are the best obtainable evidence that the injury was a dislocation.

The prognosis, as regards either the preservation of life or the full restoration of function, is not favorable. The uncertainty of the diagnosis in most cases of survival and the comparative fewness of the cases deprive the percentages of value, and it can only be said that the injury seems more likely to prove fatal when it is situated in the upper part of the region than when in the lower, and that in quite a number of cases more or less complete recovery has followed. In one that has been under my observation for two years the patient, a girl fourteen years old, has been in good health although she remains completely paralyzed below the level of the breasts; the injury appears to have been a diastasis at the fourth or fifth dorsal vertebra, and was caused by a fall down the narrow airshaft of a tenement house from a height of about sixty feet. Such prolongation of life has, however, seldom been reported. In other cases there has been a permanent deformity or an abnormal mobility at the injured point.

Treatment. Reduction, by extension and counter-extension at the hips and shoulders, has been tried, and sometimes with success. If it is obtained the patient must be kept absolutely recumbent for several weeks, and preferably with the trunk enveloped in a plaster-of-Paris dressing, and the same measures should be employed even when reduction has not

been effected, in order to favor the consolidation of the bones in their new positions.

It seems not improbable that the knife may yet be resorted to with advantage to expose the dislocated bone and enable the surgeon to act with better knowledge of the actual displacement and of the difficulties to be overcome. I believe, however, that such an operation should not be done until after the soft parts have had time to recover from the laceration of the original traumatism.

DISLOCATIONS OF THE LUMBAR VERTEBRÆ.

The possibility of the occurrence of pure dislocation of the lumbar vertebræ, which has been long in doubt because of the close interlocking of the processes and the strength of the ligaments, is proved by two cases collected by Blasius and also, it may be said, by two others in which there was present associated but unimportant fracture of some of the processes. The first two cases are those of Curling' and Porta.2

Curling presented a specimen preserved in the London Hospital Museum the intervertebral disk between the third and fourth lumbar vertebræ was destroyed, with slight splintering of the edge of the bone at one or two places; the body of the third projected nearly half an inch in front of that of the fourth, and the articular processes of the two bones were separated to the same distance; the ligaments connecting the laminæ and the spinous processes were stretched but not materially torn. The other two cases are those of Keig and Cloquet. In the former a sailor twenty-three years old was crushed under a heavy iron cylinder which fell across his back. The second lumbar vertebra was displaced backward seven lines, the upper articular process of the third becoming lodged in the notch of the second; the tip of the right lower articular process of the second was broken off but not separated from the rest; the left transverse processes of the first and second vertebræ were broken off (by muscular action, it was thought), and the spinous processes of the ninth, tenth, and eleventh dorsal vertebræ and the left eleventh and twelfth ribs were broken. The right sacro-lumbalis muscle was completely divided transversely, and the liver and spleen ruptured.

In another case Porta found at the autopsy a pure diastasis between the third and fourth lumbar vertebrae, the bones being separated a few lines without lateral or antero-posterior displacement, and all the ligaments being torn; the spinous process of the third was broken at its base.

The conditions which so effectually oppose dislocation with or without fracture are the great breadth, thickness, and elasticity of the intervertebral disks, the large masses of muscle that lie on each side of the spinous processes, and the arrangement of the articular processes by which those of each upper vertebra are received between those of the next lower and

Curling: London Hospital Reports, vol. 3, p. 355.

2 Quoted by Blasius: Loc. cit., vol. 103, p. 55.

Keig: Schmidt's Jahrbuch, vol. 107, p. 69. (Blasius writes the name Keli.) Blasius: Loc. cit., from Journal des Difformités, vol. 1, p. 453.