Skiagram of coxa vara; deformity most marked at the epiphyseal junction. This illustrates the mechanical limitation of abduction caused by the deformity, and the compensatory tilting of the pelvis. (Whitman.)
Fig. 270
Congenital misplacement, with consequent atrophy and shortening. (Calot.)
Pathological changes are noted in the capsule itself, as well as in the bony components of the joint. Thus the capsule is usually elongated and stretched out of shape, while its lower portion may be adherent to the margin of the acetabulum or may be shut off into a small cavity by itself, this cavity having but a small connection with the balance of the capsule and affording irresistible obstacles to reduction. With changed joint relations the muscular arrangements are also changed, some being lengthened, others shortened, as would naturally follow from the approximation or separation of their points of origin and insertion. Conspicuous change is seen in the upper end of the femur, which is often atrophied, while the neck is shorter than normal, its angle lessened, and the head of the bone often altered in shape. A secondary acetabulum is in time formed and is usually found upon the side of the ilium. This is shallow and insufficient to ensure firm support for the head of the femur, even were this well developed. Aside from these changes the pelvis is usually poorly developed on the affected side, its inclination increased, the sacrum forced forward and downward, the pelvic outlet widened, while a considerable degree of lumbar lordosis is present ([Fig. 270]).
The condition is rarely noted until a growing infant begins to learn to walk. The condition is one which has no symptoms, only signs, and these do not at first attract attention. Sometimes it will have been noted that there is an abnormality about the hip, with too free play, or a snapping sound about the joint. When the condition is unilateral there is a marked limp which increases with the age of the child. With each step the femoral head is pushed upward on the side of the ilium, and, in consequence, the pelvis is tilted toward the outside, as well as twisted downward and forward. The limb being thus actually shortened, the limp or waddling gait is easily accounted for. Along with it there is usually flattening of the tibia, while the trochanter may be felt and often seen on a level considerably above that where it properly belongs. Motility in the joint is abnormally free, and with a child on its back, by alternately pulling and pushing, the abnormally free play of the upper end of the femur may be easily demonstrated, either with the limb in its extended or the flexed position.
When the misplacement is bilateral the individual is more symmetrically deformed. The lordosis is increased, the abdomen protrudes, the thighs are separated more widely than is normal, leaving perhaps a considerable space in the perineum; the gait is of a peculiar waddling character, which makes locomotion apparently difficult, although it is free from pain. In these cases abnormal mobility of the hip may be demonstrated on each side.
As these patients grow through adolescence into maturity they sometimes improve, but usually suffer more and more difficulty in locomotion, while the abdominal protrusion and the lordosis become more and more pronounced.
Three varieties of congenital misplacement are described as backward, upward, and forward. It is in those instances where the head of the bone rests well back or well forward upon the ilium that the gait is most pronounced, but in all instances the great trochanter will be found above Nélaton’s line.