BACKGROUND: Radiographs can diagnose slipped capital femoral epiphysis (SCFE) on the anterior-posterior (AP) pelvis view and the frog-leg lateral view of the hips. On the AP radiograph, the lack of intersection between a line drawn parallel to the superior edge of the femoral neck (Klein's Line) and the epiphysis confirms a slip. Despite broad knowledge of the Klein's Line principle, application is difficult and inaccurate, especially in mild cases. On the frog-leg lateral radiograph, Southwick head/shaft angle and Wilson percent epiphyseal displacement commonly quantify the slip. Here, we set out to evaluate the intraobserver and interobserver reliability and the efficacy of these methods. METHODS: Five separate observers on 2 separate occasions evaluated 30 AP and 30 frog-leg lateral radiographs of patients with unilateral SCFE for head/shaft angle, percent epiphyseal displacement, and width of epiphysis lateral to Klein's Line. RESULTS: We calculated the minimum difference required for 2 measurements to be considered different with 95% confidence ("minimum agreement difference"). For head/shaft angle, the intraobserver minimum agreement difference was +/-7.27 degrees and the interobserver +/-8.80 degrees; for percent epiphyseal displacement, the intraobserver was +/-7.18% and the interobserver was +/-7.27%; and for width of epiphysis lateral to Klein's Line, the intraobserver was +/-1.98 mm and the interobserver +/-2.16 mm. For each of these measures, the slipped hips significantly differed from the control hips (P<0.001 in all cases). Our analysis of the classical definition of Klein's Line--the lack of intersection between Klein's Line and the epiphysis as a sign of a slip--identified only 40.3% of slips. By modifying Klein's Line such that we measure the width of epiphysis lateral to Klein's Line, we improved sensitivity to 79% if a difference of 2 mm between hips indicated a slip. CONCLUSIONS: On the basis of our findings, head/shaft angle and percent epiphyseal displacement provide reliable and efficacious means of radiographic SCFE diagnosis. The classic definition of Klein's line fails to identify 60% of slips. We propose a modification of Klein's Line to improve sensitivity.
BACKGROUND: Radiographs can diagnose slipped capital femoral epiphysis (SCFE) on the anterior-posterior (AP) pelvis view and the frog-leg lateral view of the hips. On the AP radiograph, the lack of intersection between a line drawn parallel to the superior edge of the femoral neck (Klein's Line) and the epiphysis confirms a slip. Despite broad knowledge of the Klein's Line principle, application is difficult and inaccurate, especially in mild cases. On the frog-leg lateral radiograph, Southwick head/shaft angle and Wilson percent epiphyseal displacement commonly quantify the slip. Here, we set out to evaluate the intraobserver and interobserver reliability and the efficacy of these methods. METHODS: Five separate observers on 2 separate occasions evaluated 30 AP and 30 frog-leg lateral radiographs of patients with unilateral SCFE for head/shaft angle, percent epiphyseal displacement, and width of epiphysis lateral to Klein's Line. RESULTS: We calculated the minimum difference required for 2 measurements to be considered different with 95% confidence ("minimum agreement difference"). For head/shaft angle, the intraobserver minimum agreement difference was +/-7.27 degrees and the interobserver +/-8.80 degrees; for percent epiphyseal displacement, the intraobserver was +/-7.18% and the interobserver was +/-7.27%; and for width of epiphysis lateral to Klein's Line, the intraobserver was +/-1.98 mm and the interobserver +/-2.16 mm. For each of these measures, the slipped hips significantly differed from the control hips (P<0.001 in all cases). Our analysis of the classical definition of Klein's Line--the lack of intersection between Klein's Line and the epiphysis as a sign of a slip--identified only 40.3% of slips. By modifying Klein's Line such that we measure the width of epiphysis lateral to Klein's Line, we improved sensitivity to 79% if a difference of 2 mm between hips indicated a slip. CONCLUSIONS: On the basis of our findings, head/shaft angle and percent epiphyseal displacement provide reliable and efficacious means of radiographic SCFE diagnosis. The classic definition of Klein's line fails to identify 60% of slips. We propose a modification of Klein's Line to improve sensitivity.
Authors: A Lam; S A Boenerjous; Y Lo; J M Abzug; J Kurian; M C Liszewski; D E Sanderson; J M Scholnick; B H Taragin; J A Gomez; N Y Otsuka; R Hanstein Journal: J Child Orthop Date: 2018-04-01 Impact factor: 1.548
Authors: Daniel A Maranho; Sarah D Bixby; Patricia E Miller; Shayan Hosseinzadeh; Michael George; Young-Jo Kim; Eduardo N Novais Journal: Clin Orthop Relat Res Date: 2020-05 Impact factor: 4.755