1. Approximately 25 per cent. of dislocated hips may be expected to become perfect or excellent after bloodless reduction. This percentage is increased to 35 in hips in which the dislocation is reduced during the first three years of life.
2. Another 15 per cent. of hips may be expected to become functionally satisfactory for a varying number of years, with the understanding that eventually symptoms of fatigue, pain, and limp may arise. This percentage is increased to 20 when the dislocation has been reduced before the end of the third year.
3. Failure (subluxation or recurrence of complete dislocation) may be expected in 60 per cent. of all primarily reducible dislocations, and in 45 per cent. of those reduced in the first three years.
4. The form and the degree of the dysplasia of the various structures of the hip joint which is present at birth, and the ability or inability of resumption and continuation of normal growth after reduction, are the essential factors that determine the end result.
5. The time factor (age of the child at time of reduction) is of secondary influence, inasmuch as the end results are better in hips in which the reduction was carried out during the first three years of life than in those reduced after this age. It is not this factor, however, which determines the result in the large group of hips in which reduction was achieved early. The high percentage of cures nesulting from the treatment of predislocation seems to prove the great importance of the time factor; but this is open to question, because many cases of predislocation are cured spontaneously or by minimal treatment.
6. The "perfect" end results are to be found only among those cases that are amenable to bloodless reduction. If open operation is necessary for reduction, one can always observe the presence of one or more of those structural deformities that make the development of a perfect hip impossible. Of marked importance and frequency among these are the deformities of the neck of the femur and a high capsular attachment.
7. Various operative procedures are of great value to restore stability of the hip and to improve its function. Complete restoration of normal function and a close approach to normal anatomy may be obtained by a timely, wisely selected, and properly executed operation in cases of prolonged acetabular aplasia, unaccompanied by other, more serious deformities.