Minor displacements of the coccyx

Glasgow Medical Journal

1922, Volume 98, pages 118-125

Cyriax, EF.

The above title refers to minor displacements of the coccyx on the sacrum; I have never seen one occurring in the inter-coccygeal joints. Although the profession have long ago recognised that major displacements (i.e., complete dislocation) of the coccyx may occur, they have been loth to admit the possibilities of minor displacements (i.e., incomplete dislocation) thereof. Indeed, no attempt seems to have been made to distinguish the above two classes, and the question of whether a complete displacement is present or not appears to be determined by the severity of the symptoms, and not by the amount of displacement. Thus, a small displacement with marked symptoms would be considered as being a complete dislocation, whereas a similar one, or one even greater in amount, with hardly any symptoms, might be considered as not being a displacement at all. This, though perhaps clinically correct, is anatomically quite the reverse. Every joint which normally permits of movement, especially when, as in the case of the sacro-coccygeal joint, it possesses an interarticular cartilage and a rudimentary or actual synovial membrane, can be the seat of minor as well as major displacements. Indeed, in most joints the former are commoner than the latter, and the sacrococcygeal articulation is no exception to the rule.

Causes. - Minor displacements of the coccyx seldom occur after middle life, due no doubt to the fact that the sacrococcygeal joint generally becomes united about this time, and they are very much commoner in females, due in all probability to the latter possessing greater mobility of this joint in common with the other joints of the pelvis. In about half of the cases that I have had under my care there has been a history of direct violence, such as falls on the buttock or kicks on the bone. I have also met with each of the following causes in one instance: Rheumatic fever (see below), straining at stool, pelvic cellulitis, sudden effort to save falling. In the remainder of the eases, all of them being forward displacements, with tilting in the same direction, there was apparently no cause, but as they all occurred in persons of sedentary habits and flabby muscles, I think that they owed their origin to over-use of the sitting position, whereby the bone was gradually pushed forwards - this is analogous to the method of production of various other deformities.

Varieties. - Displacement forwards is by far the commonest variety, the coccyx either remaining in its correct plane or else becoming abnormally tilted, this being nearly always in a forwards direction. Backward displacements are rarer, but when they do occur are also sometimes associated with tilts- nearly always forwards. These two varieties could quite well be classed respectively as localised kyphosis and lordosis of the sacro-coccygeal region. I have never met with a minor lateral or a minor rotary displacement, but if they did occur-and I cannot see why they should not do so - they would fall under the heading of scoliosis in this area.

Pathology. - As regards the actual sacro-coccygeal joint, it may become affected by synovitis, adhesions, and thickenings, just as in the case of minor displacements elsewhere. As regards the structures adjacent to the joint and the bone, the displacement induces changes in the normal anatomical equilibrium in all of them, specially the nerves, the sacro-coccygeal and the coccygeal ganglion. If compensation arises, no further nervous changes will ensue, but if it does not do so, these nervous structures may, in the course of time, become irritated or inflamed, and corresponding symptoms will result.

Symptoms. - These are analogous to those of minor displacements of bones elsewhere. In a few cases there may be none at all, though pain is usually experienced, and may be either constantly present or may only arise when the sitting position is assumed, specially if this be done on a hard seat. The pain is usually aggravated by travelling in motors and trains, and is often increased during defecation, sometimes to such an extent that the patient dreads having rectal evacuations, and constipation ensues. The resultant overloading of the rectum, with perhaps the ensuing necessity to strain at stool, may act in a vicious circle with the nerve irritation. In order to avoid pain, the patients often sit sideways on a chair, frequently continually changing so as to rest alternately on each buttock. In more than one case I have known the patient to have a chair specially constructed so as to remove all pressure in the middle line. In severer cases even this may be insufficient, and relief from pain is only obtained by lying down on one or other side.

Pressure over the joint when applied as if to increase the deformity nearly always increases the pain, but may relieve it when administered in the opposite direction. Palpation of the bony margins adjacent to the joint may show undue projection of the lower edge of the sacrum or the upper edge of the coccyx, as the case may be, and an abnormal amount of separation is detectable in major degrees of forward tilts. Attempts at passive movements of the joint may elicit coarse grating sounds, and nearly always induce pain, specially when such movements increase the amount of displacement.

Constipation is occasionally present (see above); this is probably also in part due to the displacement causing pressure on the coccygeal ganglion, which is motor for portions of the large intestine (1). Various reflex pains may arise, the commonest being sciatica. In two such cases pressure upon the coccyx, as if to increase the deformity, caused great increase in the sciatica as long as the pressure was maintained. In two other cases a similar pressure caused a feeling of nausea, though there were no digestive anomalies.


(a) In the case of displacement en masse without tiltings. The principles of treatment are on the same lines as for displacements elsewhere, namely, reposition followed when necessary by mechano-therapeutics. Reposition is generally quite easy unless large numbers of adhesions have formed, and is practically painless; I have never yet had occasion to employ anaesthetics. As a preliminary to reposition, it is highly advisable to obtain relaxation of the joint area. This is best effected by means of manual vibrations applied during the space of a few minutes, either over the posterior surface of the bone or simultaneously over both anterior and posterior surfaces, the thumb being placed over the posterior and the forefinger over the anterior surface of the bone, either through the perineum if it is sufficiently yielding or else per rectum. The bone is then grasped with the forefinger and thumb, and gently moved alternately backwards and forwards, and, if needs be, also from side to side, with gradually increasing range. Then with a sudden movement the bone is replaced. The reposition is generally attended by a sound similar to the one that occurs with reposition of bones elsewhere, and immediate amelioration of symptoms is generally the result. Amongst unusual ones thus improved may be mentioned (1) pain in the anterior tibial nerve remaining after great improvement in sciatica; (2) difficulty and pain when walking from arthritis of the hip-joint; (3) difficulty with micturition.

Sometimes reposition per se will effect a cure, no further treatment being required. This, however, applies only to, simple cases of recent date. In most others it is generally advisable to give a few days' treatment of mechano-therapeutics, consisting of manual vibrations over the coccyx, followed by passive (movements of flexion and extension of the affected joint with a few resisted exercises for the gluteal muscles.

(b) In the case of tiltings. When combined with displacements they can often be corrected simultaneously with reposition of the bone. When tiltings exist per se, they are to be treated by gradual stretching of the shortened ligaments, together with stretching or rupture, as the case may be, of any adhesions, just as with contractures elsewhere.

So far, all my cases of displacement en masse and all those combined with tiltings, with one exception (this case is described below), have resulted in complete and permanent cure. I am of the opinion that were the above treatment more universally adopted, a great proportion of excisions of the coccyx would become unnecessary.

I give herewith the notes of one of my cases which I consider presents some unusual features:-

F. S,, Belgian soldier, contracted rheumatic fever during September, 1914, and was taken to a hospital in Antwerp. In consequence of the German advance he was taken two days later on a stretcher to Ghent, where he remained for eight days, after which he was taken to England. In all, he remained in bed for about ten months before he was allowed to get up and lie on a couch. By June, 1915, his joints were quite free, though he was very weak; during July, 1915, he was allowed to walk, but he found it very difficult, chiefly owing to the fact that he felt jerky. This gradually became worse, so that by June, 1916, he was unable, though much stronger in himself, to walk more than about 200 yards in consequence of the muscular spasms that invariably supervened as soon as he was on his feet. Walking this distance took him about half an hour, and left him temporarily completely exhausted.

I first saw the patient on 16th June, 1916. When he lies down there are no jerks, but they begin with modified intensity as soon as he sits up, and are very marked indeed when he stands. The jerks consist of intermittent contractions, chiefly located to the muscles of the calf, though the glutei participate to a less extent. Their rate is about six per second, and they appear to he equal on both sides. They cause rapid violent alternating rising up and down on the toes, so that even when standing his body as a whole moves alternately up and down with great intensity, shaking the floor quite violently; they occur with the same force when he tries to walk. He takes thirty minutes to walk upstairs in his residence from the ground floor to the top floor, having to rest on each landing, and the jerks cause the whole house to shake so that anybody on the top floor knows at once when he is starting from the bottom. The jerks are not accompanied by any pain though they induce great fatigue, and (apart from the glutei) do not occur is the trunk or arms. The reflexes are normal, beyond some increase in the right knee jerk; there is no constipation or bladder trouble.

There is no abnormality over the posterior surface of either the sacrum or the coccyx, but per rectum there is diffuse tenderness over the whole anterior surface of the latter. No abnormal thickenings or fibrous bands can be detected in this area. Pressure on the posterior surface of the coccyx, thus causing it to move forwards, causes a considerable amount of pain. Palpation shows that the coccyx is displaced forwards at the sacro-coccygeal joint, and in addition, has a forward tilt. When the patient stands up and exhibits the muscular spasms referred to above, these are immediately totally inhibited by pressing the coccyx through the perineum in a backward direction, and remain in abeyance as long at this pressure is maintained. This pressure, if kept up while he walks, enables him to do to perfectly normally.

Partially relaxing it causes the jerks to reappear in direct proportion to the degree of such relaxation. This test was repeated by me on number of subsequent occasions, and invariably with the same result. No other pressure on or at the side of the vertebral column, or any other form of spinal manipulation or nerve friction on the spinal nerves, modifies the jerks in the very slightest degree.

The fact that the calf muscles and the glutei are the only muscles involved points to an irritative bilateral lesion in the neighbourhood of the fifth lumbar, first and second sacral segments, though it is very difficult to come to any conclusion either regarding its precise nature or why extension of the coccyx should abolish the jerks.

The treatment, consisting of vibrations over the coccyx followed by mobilisation and reposition, was commenced on 19th June, and was applied on 33 occasions until 31st July, and on 50 subsequent occasions from 7th September and 11th November, 1916. The actual reposition of the displacement was effected in two sittings, but this did not exercise any change in the tilt of the bone, which only commenced to show signs of improvement about one week later. On 24th June the rate of the jerks was only about half its former one, and they were much diminished in intensity, so that walking was easier. On 2nd July he walked half a mile. On 31st July he walked three-quarters of a mile, and could get upstairs in his house in ten minutes instead of half an hour.

On 7th September, when I saw the patient again, his condition was only very slightly worse than when I last saw him on 31st July. From now onwards improvement once again set in, and on 27th October he walked a mile and a half, and did not feel unusually fatigued; he could now walk upstairs as fast as any normal person.

10th November. - The jerks are practically unnoticeable, excepting in very slight degree to the patient himself; nobody else notices them when he walks upstairs. Yesterday he walked two miles in fifty minutes without a pause, and did not feel fatigued.

Unfortunately at this juncture, the patient was suddenly removed from London to a hospital in Ireland, after which he was in the course of time taken to other hospitals, and finally sent back to Belgium. Within about three weeks of stopping the treatment I had been giving him, his condition began to get worse, and continued to do so slowly but progressively in spite of various other treatments employed, such as spinal massage, electricity, hot and cold water baths, &c. During 1920 a special spinal jacket was constructed for him, the lower end of which fitted round the anterior edge of the coccyx and drew it backwards by means of a powerful spring. This inhibited the jerks, and enabled him to walk, though with some difficulty.

During a stay in Belgium during Easter, 1922, I saw the patient once again. The general condition is worse than when I saw him last; there is considerable emaciation and weakness of all the muscles of the body. When he is wearing the jacket he can walk slowly with the help of a stick, and his gait very much resembles the spastic type. The maximum amount he can walk without stopping is about three-quarters of an hour. On removing the jacket the patient's condition as regards the jerks is much worse than when I first saw him. Attempts to stand, even with support under both arms, produce violent spasms in both legs which get progressively worse the longer the patient makes the effort, and are very similar to the volition jerks found in disseminated sclerosis. After he has tried for a few seconds to stand up, the jerks become so violent that I told him to sit down again, fearing that the patient would throw himself and the chair and his supporters on to the floor if he continued.

When the patient had sat down again the jerks in his legs persisted, but were cut short by the patient exercising compression of his thigh with both hands. I then turned the patient partially over on his side, and, passing my finger into the rectum again, exercised pressure backwards on the coccyx in the same manner as five years previously. During the time that I kept this up the patient was requested to stand up, which he did without any jerks appearing at all, and maintained this position quite steadily. A slight relaxation of the pressure caused the jerks to reappear in modified degree. In all other respects the physical signs are practically unchanged; nothing abnormal can be felt per rectum. The reflexes are less pronounced than before, the left knee-jerk being almost absent and the right one sluggish.


1. Cyriax, E. P. and R. J., Zeit. f. allgem. Phys., 1913, vol. xiv, pp. 297-308.

2. Cyriax, E. P. The Medical press and circular 1922, N.S., vol. cxiii, pp. 47-49.

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