Classification in slipped capital femoral epiphysis. Sonographic assessment of stability and remodeling.

In a prospective study of 26 hips in 21 patients with slipped capital femoral epiphyses (SCFEs), serial sonography was more sensitive than radiography in showing epiphyseal displacement and reduction. Reductions were associated with grossly visible hip joint effusions. The initial slips were reduced by treatment in seven of 11 hips with effusion. The 15 hips without effusion were unreduced. After stabilization and pinning, the effusion did not recur in any case. Sonography is sensitive and free from projectional errors in the assessment of metaphyseal remodeling. If any remodeling is present, the SCFE is at least three weeks in duration. A new classification into acute, acute-on-chronic, and chronic SCFEs is proposed, based on the objective sonographic data. Joint effusion represents physeal instability or recent progression, and remodeling is a sign of chronicity. An acute SCFE is characterized by effusion, whereas a slip without effusion but with remodeling is designated as chronic. An acute-on-chronic SCFE is associated with both effusion and remodeling. Joint effusion suggests that SCFEs should be operatively fixed and that displacement may diminish with traction or intraoperative positioning of the hip.