Principles of treatment in late stages of Perthes disease.

It is of paramount importance to distinguish hips that may or may not be suitable for containment in the transitional stage (fragmentation to early reossification stage), because long-term clinical and radiological outcomes may be influenced by the choice of treatment. This article summarizes the definition of hinge abduction, pathoanatomy of hinge segment, assessment of hinge abduction, determination of reducible and irreducible hinge abduction, and treatment strategies for containable and uncontainable hips in the transitional stage.