Deformities Of The Long Bones

The most obvious change at the outset is swelling of the cartilaginous ends (see Fig. 268) of the long bones, giving a clubbed or knobbed appearance to the limbs. This is common to all the long bones, and is the condition generally taken in practice as evidence of the existence of the disease. The bones are also arrested in their growth, so that they are stunted while at the same time they are unduly thick.

The remaining deformities occur in the majority of cases in the lower limbs, and are the result of the weight of the body acting on the bones in their weakened condition.

Similar deformities are met with in the bones of the arms (see Fig. 268) in cases where external force is frequently applied to them, as where a child in creeping leans on the arms, or where a nurse frequently lifts a child by one arm (Macewen). The deformities consist mainly of curvatures of the shafts of the bones, along with shifting of the epiphyses in some cases.

Shifting of the epiphyses is due to the condition of the ossifying cartilage. The extended blue zone at the cartilaginous border, being soft, allows the epiphysis to change its position according to the direction of pressure, and so at the ankle the epiphysis is sometimes displaced inwards, and, as it were, overhangs the joint on its internal aspect. The same may occur at the knee-joint, and the internal condyle may exceed in length the external even after the disease has been cured.

Fig. 268. - Humerus and radius and ulna in rickets. The humerus is much swollen in its upper parts. The bones of the fore-arm are much bent.

The curvatures of the bones (see Figs. 268 and 269) are due mainly to the weight of the body acting on the softened shafts, and as the pressure acts mainly on the lower limbs the two principal forms are genu valgum and genu varum.

Genu valgum, or knock-knee, is a condition in which the thigh and leg form an angle at the knee with its apex inwards. This deformity depends usually on several alterations. There is generally a curve of the lower third of the femur, with its convexity inwards, the effect of this being that the internal condyle is lower and the external higher than normal. Along with this there is usually the lengthening of the internal condyle already referred to, and illustrated in Fig. 265, p. 533. As a rule the tibia is not bent, the two conditions named taking the chief part in producing the deformity, but sometimes the shaft of the tibia is at an angle with the epiphysis, as if the latter were to some extent overhanging the former. In addition the femur or tibia sometimes shows an anterior curvature, which of course does not increase the valgum condition.

Genu varum, or bow-legs, is the converse condition to genu valgum. The shafts of the femur and tibia are curved, with the convexity outwards, but these bones take part in the deformity in very different degrees, the tibial curve being more frequent and usually more pronounced than that of the femur.

The long bones being soft and flexible are not so liable as normal bones to complete fractures, but they are specially liable to Partial fractures or infractions If the bone is suddenly bent it does not break across, but is partially torn as when an attempt is made to break a green stick. In this case the concave surface of the bent bone gives way and the convex surface does not. The marrow is torn by the broken concave portion, the broken edges of which may be projected through the marrow to the opposite internal wall. This kind of fracture has been aptly compared by Virchow to the breaking of a quill. These infractions occur most frequently at the lower part of the tibia, also in the pelvis and ribs, and less frequently in the bones of the arm.

Deformities Of The Chest

The junction of the cartilaginous and bony ribs is analogous to the ossifying cartilage of a long bone, and undergoes a similar thickening in rickets. These parts of the ribs are therefore knobbed, and there is thus a row of knobs on each side of the chest - the so-called Rachitic rosary (Pig. 270). The chest is also liable to deformity from the flexibility of the ribs.'

Fig. 269. - Bending of tibia and fibula from rickets. The active disease had ceased in this case.

During inspiration the lateral aspects of; the ribs are drawn inwards from being unable to withstand the atmospheric pressure, so that instead of the natural arch with the convexity outwards, these lateral portions are flattened or even rendered concave. As the ribs take thus a straighter course the sternum is pushed forward, and the anteroposterior diameter of the chest increased.

Deformities Of The Vertebrae

The vertebrae very often escape in the milder forms of rickets, but in many cases they also are composed of abnormally spongy bone, and allow of the occurrence of curvature. Such curvatures are mostly exaggerations of the normal anteroposterior curves, but lateral curvature alsc-occurs. Any considerable curvature will cause narrowing of the chest, and if this be associated with the deformity mentioned above, the interference with the circulation and respiration may be serious.

Deformities Of The Pelvis

These are of great importance in the female in relation to the possible occurrence of pregnancy in after life. The chief deformity is produced by the weight of the body acting through the vertebral column on the sacrum. This bone is pushed forward and the pelvis undergoes a corresponding displacement of its parts, the antero-posterior diameter being diminished. The growth of the bones here also is stunted, and the pelvis therefore remains unduly small.

The bones of the head frequently undergo very marked deformities. The bones of the face, like the bones generally, are stunted in their growth so that the face is small. It is also stated that the jaws by the action of the muscles undergo changes in shape by which the lower jaw is shortened and the upper jaw lengthened, so that the teeth of the latter overlap very much those of the former. While these are the conditions in the face the bones in the cranium present striking peculiarities. The flat bones ossify from membrane, and in rickets we have the ossification lingering behind so that at their borders these bones present somewhat broad areas in which there is soft tissue like that under the periosteum. The effect of this is to cause an apparent widening of the sutures and extension of the fontanelles. The closure of the fontanelles is also delayed. The thickness of the skull is increased, just as is that of the shafts of the long bones, the pericranium like the periosteum generally producing a thick layer of loose ill-formed bone. The cranium is thus enlarged in circumference, and at the same time it is commonly flattened on the summit. The enlargement of the cranium, with the stunted condition of the face, causes the well-known overhanging of the brow so often seen.

Another occasional consequence of rickets is the condition designated Craniotabes. As we shall see afterwards, this is frequently a consequence of syphilitic disease of the bones, but it occurs also in rickets. The bone in rickets is soft, possessing less power of resistance than normal bone. If the child be lying constantly on one spot, or if the contents of the skull be increased, as in chronic hydrocephalus, then the pressure on the bone may cause it to waste. This occurs most frequently when both these conditions are present, and the bone is as it were between two pressures.

Fig. 270. - Swellings at junction of cartilaginous and osseous ribs - the so-called Rachitic rosary.

In this way may occur thinning and actual perforation of the skull, so that in the midst of the bones there will be holes, where the brain is covered by the soft parts alone. From the nature of the case it will be understood that these apertures are mostly in the occipital or the parietal bone, according as the child lies mostly on its back or side.

Recovery

This takes place in rickets by the removal of the insanitary conditions, or by the termination of the period of growth. The ossification advances in the cartilage and under the periosteum. The spongy bone produced under the periosteum becomes dense, and so the bone may be unduly heavy and thick, while it is stunted. The deformities having occurred in a rigid structure are rendered even more fixed by the completion of the ossification. There is, however, in the course of time an effort on the part of nature to restore the normal architecture of the bones (see Fig. 265); where they are bent absorption occurs on the convex surfaces and increased new-formation on the concave; there may be considerable restoration of the proper shape in the long bones, but usually much less in the pelvis, head, and thorax.