Southwick's head-shaft angles: normal standards and abnormal values observed in obesity and in patients with epiphysiolysis

Southwick's angles measured in the anteroposterior and Lauenstein frog-leg views have been used for planning surgical treatment of deformities caused by slipped capital femoral epiphysis (SCFE). Clinically established epiphysiolysis is associated with a decrease in anteroposterior angles and an increase in Lauenstein angles. Obesity is one of the factors involved in the development of SCFE, but its influence in Southwick's angles has not been previously described. Additionally, few reports describe normal values adjusted for sex and bone age. In this study, we determined Southwick's angles in normal control participants (n=70), in patients with obesity (n=31) and in patients with epiphysiolysis (n=33). The intra-observer variations were 1.7 and 23.3% for the anteroposterior and Lauenstein angles, respectively. No significant differences were detected in the control group when these individuals were compared according to sex or chronological age. Obese patients showed a significant increase in the anterposterior angle when compared with control individuals. The hip with epiphysiolysis presented a significant reduction in the anteroposterior angle and an increase in the Lauenstein angle, when the same was compared with the contralateral hip or with the control values. In patients with unilateral SCFE the Lauenstein angle of the normal hip was detected as increased, which was possibly related to the obesity associated with decreased insulin resistance presented by these patients. We conclude that the detection of risk for developing SCFE should include an expanded clinical and radiological profile characterized by pubertal males who present obesity associated with insulin resistance and an increase in Southwick's anteroposterior angle.