Radiological and clinical femoroacetabular impingement after slipped capital femoral epiphysis treated by in situ fixation.

Background: The treatment of slipped capital femoral epiphysis (SCFE) is always surgical. In situ fixation (ISF) is widely accepted to stop the epiphysis slipping. Femoroacetabular impingement (FAI) is recognized as a complication after ISF and is one of the major causes of early hip osteoarthritis.

Study aim: The aim of this study was to characterize the relation between clinical and radiological signs of FAI.

Methods: A monocentric study that included all consecutive children treated for SCFE by ISF between 2006 and 2017 was performed. Clinical examination consisted in range of motion (ROM) measurement for both hips, impingements tests and functional scores (Harris Hip Score (HHS) and Womac score). Radiological analysis was based on signs of impingement (alpha angle, anterior head neck offset (OS), anterior head neck offset ratio (HNOR).

Results: 36 hips were included. At follow-up, the difference between the mean hip ROM on the SCFE side and the healthy side were statistically significant in abduction and in internal rotation. Ten (28%) hips presented at least one clinical test positive for FAI (FADDIR and/or FABER). All the patients presented a good or excellent functional score. Eight patients (22%) presented all radiological signs of impingement; among these, 3 had a clinical sign of FAI. Twenty-eight hips (78%) presented at least one radiological sign of FAI; among these, 10 had clinical signs of FAI.

Conclusion: Despite a high rate of radiological FAI, less than one-third of patients have clinical signs of FAI after ISF for SCEFE.

Level of evidence: III: retrospective study.