Femoroacetabular impingement after slipped capital femoral epiphysis: does slip severity predict clinical symptoms?

BACKGROUND: Femoroacetabular impingement (FAI) may be common after slipped capital femoral epiphysis though the actual frequency is unknown. The purpose of this study was to determine the frequency of symptomatic FAI in young adults after slipped capital femoral epiphysis and define its relationship with slip severity.

METHODS: We retrospectively reviewed a consecutive series of 49 patients (65 hips) to determine patient and slip characteristics and treatments. Patients were then recalled for clinical and radiographic review to assess symptoms, particularly impingement, and outcomes after skeletal maturity.

RESULTS: Thirty-six patients (49 hips) were reviewed clinically and radiographically with a mean follow-up of 6.1 years (range: 2.2 to 13.1 y). All patients had reached skeletal maturity. Thirty-one percent (15/49) of patients complained of hip pain or stiffness, whereas 32% (16/49) had clinical signs of impingement. The Southwick slip angle and grade of slip or Loder's classification of physeal stability were not predictive of impingement at follow-up. The anterior head-neck offset angle (alpha angle) correlated most strongly with FAI (r=0.26). No pre-slips or prophylactically pinned hips developed clinical impingement in this review.

CONCLUSIONS: In the absence of radiographic indicators to predict FAI, we advocate all but those hips pinned prophylactically or for pre-slip should be followed into adulthood and clinically monitored for impingement. Grade of slip in adolescence cannot be used as a predictive tool for FAI later in life.

LEVEL OF EVIDENCE: Level II, retrospective study.