Congenital Sacro-coccygeal Sinuses and Fistulæ.—The post-anal dimple, a shallow depression frequently observed over the tip of the coccyx, may be due to traction exerted on the skin at this spot by the remains of the neurenteric canal, or by the caudal ligament of Luschka. Sometimes the integument is retracted to such an extent that one or more sinuses are formed, lined with skin which is furnished with hairs, sweat, and sebaceous glands. The bursting of a dermoid, or its being incised in mistake for an abscess, may result in the formation of such a sinus, which fails to heal and may persist for years.
In some cases the depression communicates with the vertebral canal, constituting a complete sacro-coccygeal fistula, which may be lined with cylindrical or ciliated epithelium.
From the accumulation of secretions and subsequent infection, these conditions may be associated with a persistent offensive discharge, and they are liable to be mistaken for ano-rectal fistulæ. They are best dealt with by complete excision, and as primary union cannot be expected, the wound should be treated by the open method.
CHAPTER XVIII
DEVIATIONS OF THE VERTEBRAL COLUMN
Three main deviations of the vertebral column are described: Lordosis, in which it is unduly arched forwards; Kyphosis, in which it is unduly arched backwards; and Scoliosis or lateral deviations, in which the spine deviates to one side of the middle line.
Lordosis or anterior curvature of the spine with the convexity forwards, is chiefly met with in the lumbar region as an exaggeration of the natural curvature. A minor degree of lordosis sometimes occurs as a peculiarity in the conformation of the individual and may be present in several members of the same family; also in street-hawkers and others who carry weights suspended in front of them; in very obese persons; in those who suffer from large abdominal tumours, such as fibroids; and in pregnant women. In its more marked and typical forms it is met with as a compensatory deviation when the pelvis is tilted forwards in association with flexion of one or of both hip-joints. Illustrations of this association are found in congenital dislocation of the hip, particularly when this is bilateral, in tuberculous disease of the hip when recovery has occurred with ankylosis in the flexed position, and in Charcot's disease of the hip. The resuming of the erect position with tilting of the pelvis from flexion at the hip is necessarily attended by an exaggeration of the forward curvature of the lumbar spine. Its relationship to the erect posture is readily demonstrated by noting its partial or complete disappearance when the patient is sitting and the tilting of the pelvis is thus eliminated.
Lordosis elsewhere than in the lumbar segment is met with as a compensatory deviation to kyphotic or backward curvature of the spine: in [Fig. 211], for example, a kyphotic projection in the mid-thoracic region has led to a lordosis in the cervico-thoracic segment above, and in the thoracico-lumbar segment below, the forward curve being again a necessary outcome of the resuming of the erect posture. The absence of a compensatory lordosis in such a condition would warrant the inference that the patient had been bed-ridden.
Kyphosis or posterior curvature of the spine with the convexity backwards, is met with at all periods of life, and results from a wide range of conditions.
In infancy it is a common result of general debility. The child need not appear to be badly nourished, it may even be fat and look well, but there is a want of muscular vigour such as should enable it to hold itself erect in the sitting posture. It is to be noted that a considerable degree of kyphosis may exist without interference with the normal outlook in the erect posture, and, therefore, the question of compensatory curvature does not arise. In the adolescent a degree of kyphosis in the cervico-thoracic region is common, and is spoken of as “round shoulders”; it is largely a matter of habit that requires correction by the governess or nurse. Among agricultural labourers and gardeners after middle life, and in the aged, this type of curvature is of common occurrence and is evidently associated with their occupation. An exaggerated form of the same cervico-thoracic kyphosis is met with in patients suffering from progressive muscular atrophy, poliomyelitis, osteitis deformans of Paget, acromegaly, and many allied conditions in which either the muscular or the mental vigour is deficient, and the patient adopts the cervico-thoracic kyphosis as the attitude of rest.