Multiplanar deformity analysis of untreated Blount disease.

Abstract

Although varus malalignment of the proximal tibia is the primary pathology in Blount disease, other deformities may exist. To assess multiplanar lower limb deformities, children with previously untreated early- and late-onset Blount disease who subsequently needed surgical correction were identified. Preoperative frontal and sagittal plane deformity analysis using Paley's methodology and rotational profile assessment using prone clinical examination were performed by a single examiner. Results were compared between the 2 groups and with uninvolved limbs within each group. Additionally, rotational profile of the lower limb was compared with age-matched values. Over an 8-year period, 60 limbs (40 patients) including 26 with early-onset and 34 with late-onset Blount met the inclusion criteria. Although both groups exhibited proximal tibial varus, procurvatum, and internal torsion, patients with early-onset Blount disease had greater severity. Unlike the younger patients, approximately one third of the varus malalignment of the affected extremity was attributed to the distal femur in the late-onset patients. Neither group showed any significant deformity of the proximal femur and distal tibia or sagittal plane deformity of the distal femur. There was a correlation between the severity of varus malalignment of the limb with magnitude of proximal tibial deformities in both groups and with distal femoral varus in the late-onset group of patients. Multiplanar deformity analysis is a valuable tool in the comprehensive evaluation of children with Blount disease.