This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
The hip-joint is capable of flexion, extension, adduction, abduction, and rotation. From the hip to the foot is a straight line; it can be shortened by disease or injury of the bones of the thigh or leg, and in rare cases it can be lengthened by disease at the epiphyses producing a more rapid growth than normal. It is almost unknown for hyperextension of the hip to exist, because if the femur is intact the iliofemoral ligament prevents it. If the head is gone then the upper end of the femur luxates upward and backward. Rotation likewise produces little effect on the posi- , tion of the greater trochanter. Deformities due to flexion, abduction, adduction, and shortening are common.
Fig. 497, A shows the normal position; Fig. 497, B shows hyperflexion at the hip. The increased forward bend of the pelvis necessitates an increase in the lumbar curve in order to maintain the anteroposterior equilibrium.
Fig. 497. - Distortions accompanying affections of the lower extremity.
Fig. A. - Normal erect position, showing the normal inclination of the pelvis and normal relation of the back and buttocks.
Fig. B. - The pelvis has been tilted forward and downward, being flexed on the thighs; this results in an increased hollowing of the back and an increased protrusion of the buttocks.
Fig. C. - The left thigh is adducted and the right abducted. If the left hip is ankylosed in a position of adduction, as shown, then the pelvis is tilted down on the right, inclining the spine immediately above in the same direction. This moves the centre of gravity to the right, but is compensated by a shifting of the pelvis to the left, thus bringing the vertical through the centre of gravity within the base of support. If the right hip is ankylosed in abduction, the same condition results. In order to compensate for the uneven lengths of the limbs produced by tilting the pelvis, the knee of the apparently lengthened limb is bent.
Fig. D. - The solid outline shows the position assumed when the right leg is shorter than the left. By placing a block under the short right leg the pelvis is raised to a horizontal line and the curves of the spine are straightened, as shown by the dotted outline.
Thus lordosis is produced with the accompanying hollowing of the back and projection of the buttock. This is common in coxalgia and congenital luxations of the hip. Hyperadduction and Hyperabduction. - If there is hyperadduction, as when one hip is ankylosed in a position of adduction, as shown in the left limb (Fig. 497, C), the pelvis is carried up toward the left; to restore the balance the spine is inclined to the right. If, however, the right limb is hyperabducted or fixed in a position of abduction, then in assuming the upright posture the right hip descends and the spine is inclined toward the side of the affected limb, as seen in the right hip of Fig. 497, C. In treating these conditions the spine can be brought straight by raising the abducted limb, but doing so will increase their inequality still more and shift the pelvis too far to the left. For this reason raising the shoe is not advisable, but an osteotomy and removal of the adduction or abduction is the proper treatment.
The shortening of one limb produces the same effect as the lengthening of the opposite one: in other words it is the inequality of the limbs that counts. In Fig. 497, D the right extremity is the shorter; this causes the pelvis to tilt to the right, carrying the lower part of the spine with it and producing a right convex curve which is most marked in the lumbar region. To restore the equilibrium the parts above are carried to the left. Thus a lateral curvature is produced, which, contrary to those which originate in the spine, is accompanied by tilting of the pelvis. In these cases the deformity may be great. If the spinal curvature extends high the shoulders may be uneven, the hips are uneven in height and one projects farther out than the other, the legs may be visibly unequal in length, and there is marked limping of gait. The remedy is obvious. The short limb is to be made equal to the long one by raising the shoe or by other means.