Unless the avascular necrosis is mild, this complication causes altered proximal femoral growth, creates deformity, and often leads to degenerative arthritis.
Types The spectrum of AVN includes severe necrosis, extensive physeal bridge formation, and shortening of the femoral neck, which leads to degenerative arthritis during adult life. At the other end of the spectrum is the mild resolving form characterized by irregular ossification but without physeal bridge formation and subsequent deformity.
Type 1 This pattern is common and usually resolves spontaneously with no residual deformity.
Type 2 This type of bridge is common and may not be apparent in early childhood, becoming obvious toward the end of growth. These bridges cause a tethering of growth and, if eccentric, a tilting of the growth plate.
Type 3 This type of bridge is relatively uncommon and produces some shortening of the inferior aspect of the femoral neck and a more vertical orientation of the physis.
Type 4 Central bridges cause total arrest with shortening of the femoral neck, relative trochanteric overgrowth, and mild femoral shortening.
Management of Avascular Necrosis in Children
Manage the deformity based on its severity and the type of deformity.
Prevention Attempt to prevent AVN by using preliminary traction and open reduction in stiff hips with an obstructing limbus, percutaneous adductor tenotomy, femoral shortening in the child, and immobilization in the “safe” or human position. Despite all precautions, AVN may still occur.
Early signs The early signs of AVN are often followed by evidence of a growth disturbance.
Deformity The type and severity of the avascular necrosis is related to the location and extent of the physeal bridge. The residual deformities of Type 4 AVN often require a combined distal and lateral transfer of the trochanter and a contralateral arrest of the distal femoral epiphysis. These procedures may be combined with the procedures performed at the age calculated to be appropriate for the epiphysiodesis to correct the leg length difference.