Abstract
Diagnosis of pathological genu varum in infants is difficult due to the fact that the degree of physiological bending of the tibia on X-ray film has not been investigated statistically. X-ray examinations have been carried out on 328 healthy infants to analyze the development and physiolgical bending of the tibia and their changes with age (month), and the following conclusions were reached.
1. Because of the remarkable and rapid changes in the development of infant tibia, monthly examination is required to know the physiological conditions.
2. The development of the tibia is more rapid in younger infants, and is most marked in newborns under 3 month of age.
3. In order to know the degree of bending of tibia, roentgenography on the lower extremities in the standard position (stretching the bilateral lower extremities together in parallel with the patellae facing straight forward) is necessary. The bending appears to be lessened when the tibia is more inwardly rotated, while it is exaggerated and appears similar to genu varum when the tibia is more outmardly rotated.
4. The site of bending is usually located nearer to the upper end of the bone than at the metaphysis. Upper third of the shaft of the bone is comparatively straight and increases in its length gradually with age.
5. The lines connecting A and B at the proximal end of the tibia and C and D at the distal end form an angle (∠α) at the median side of the bone. Since the angle (∠α) is correlated with the indices (PQ/MN×100) and (PQ/AC×100=bending index), the dgeree of bending may be exbressed quantitatively by ∠α.
6. The values of ∠α obtained from the study indicate that physiological inward bending is present in newborn babies which derreases in this severity rapidly within one month after birth and thereafter, gradually with age. A mild increase in bending is again observed in 16-18 months of age which is considered to be due to the load of body weight on the lower extremities at the onset of standing and walking.
