A Study of the Growth and Development of the Human Fetal Hip Joint

Abstract

<p>Congenital hip disease (CHD), a condition in which the head of femur may be partially or completely separated from the acetabulum, is detected in one to 4 infants per 1,000 live births. At birth the hip joint is cartilaginous and underdeveloped. In cases of CHD the acetabulum is shallow, the femoral head is small and aspherical, ligament of the head of femur (LHF) is elongated, and the femoral angles are abnormal. These are measureable characteristics. However, no previous studies have given quantitative data for several dimensions of this joint in a sample of fetuses, at regular intervals of age, throughout the fetal period.</p> <p>The pattern of normal growth and development was studied in 280 hip joints from 140 fetuses between 12 weeks and term. Measurements were taken of acetabular depth, diameter, femoral head diameter, the length and width of the LHF, and the femoral torsion and neckshaft angles. Histological studies of ossification and labrum structure were undertaken on a number of acetabula at intervals throughout the fetal period.</p> <p>Acetabular depth was shown to be the slowest growing variable at the hip joint. The study confirmed previous reports that the acetabulum tends to become shallower towards term but suggested that the greatest amount of change in shape may occur early in the fetal period. In a sample of femoral heads a tendency for the head to become less spherical with age was revealed. With the exception of the neckshaft angle all variables demonstrated a moderate to high positive correlation with age. Variables were best fitted by a regression model which included a polynomial on age. Only for left LHF length and right LHF width was growth a simple interest function. The velocity of growth for ail dimensions, except the neck-shaft angle, was highest between 12 and 18 weeks. After this period a deceleration in the growth rate was noted, most noticeable in acetabular depth.</p> <p>No significant differences were detected between males and females, or between the right and left sides. This indicates that the higher incidence of CHD in females, and the greater involvement of the left hip must be explained by factors other than the growth of cartilage and bone.</p> <p>The LHF was shown to be variable in shape throughout the fetal period. It was not a distinctly linear structure in normal or abnormal hip joints. A strong correlation with acetabular dimensions was not evident.</p> <p>Booth femoral angles demonstrated variability throughout the fetal period and values reported are lower than those currently accepted for the newborn. Since the angles demonstrated poor to moderate correlation with the other hip dimensions, neither angle alone appears to provide a useful indicator of normal development. A change in the orientation of the lesser trochanter with age, correlated with the increase in torsion was observed. This is considered pertinent to the reading of femoral angles on radiographs.</p> <p>In 65 hip joints from 46 fetuses variation from descriptions of normal hip joint morphology was detected. Measurements of these joints did not differ significantly from those of normal hip joints. It is suggested that a number of these variants are microforms of CHD. An unexpected number of variants and abnormal socket features were localized to the anterosuperior quadrant and anterior socket wall.</p> <p>Comparison of data from abnormal joints (18) with data from the normal growth study permitted a more precise evaluation of the abnormality. From this comparison underdevelopment of apparently "normal" joints was detected.</p>