[Variability of the femoral head and neck antetorsion angle in ultrasonographic measurements of healthy children and in selected diseases with hip disorders treated surgically].

Changes in the angle of femoral head and neck antetorsion during childhood play an important role in the physiological development of the hip joint. In the course of some diseases the angle increases pathologically, necessitating surgical treatment. Recent technical advances have enabled the application of ultrasonography (USG) for the measurement of antetorsion angle. In this study the results of USG have been verified by comparison with results of direct measurement during varus derotational osteotomy of 163 femoral proximal ends in 104 children. Values for femoral head and neck antetorsion obtained by USG correlated closely with those obtained during surgery, justifying the use of ultrasonography for the further part of this study. An increase in antetorsion was observed in 56 joints (77%) in a group of 38 children with spastic cerebral palsy subjected to surgery. Mean angle of antetorsion was 37 degrees (SD +/- 11). The angle returned to its pre-operative values within 2-3 years from surgery. In the group of 25 children with Perthes disease, increased antetorsion was found in 11 (44%) joints subjected to surgery and in 8 (32%) normal joints. The angle changed during the observation period, confirming the opinion that the increase is a secondary event in this disease. The angle was much greater than normal for age in the group of 21 children with congenital hip dysplasia. Basing on the results of surgery it is concluded that corrective osteotomy of femoral proximal end in cases of increased antetorsion and valgity of femoral neck is not a sufficient procedure to prevent the angle from reverting to pre-operative values and should be supplemented by osteotomy of the pelvis. Furthermore, ultrasonography has emerged as the best method currently available for measurement of femoral head and neck antetorsion. The correlation coefficient for USG vs. direct (intraoperative) measurement was 0.9 in all groups, reaching 0.93 in the spastic cerebral palsy group, in which contractures and limited mobility are responsible for very low coefficients in the case of other methods. The use of USG for assessment of femoral antetorsion has revealed, particularly after longer observation periods, that the angle in the apparently normal contralateral extremity exceeded values normal for age.