Background: Children with Blount disease tend to be heavier than
their peers; however, the relationship between the magnitude of obesity and
the severity of limb deformities in Blount disease has not been well
studied.
Methods: A retrospective review of the preoperative medical records
and radiographs of patients with previously untreated Blount disease was
conducted. Demographic information including gender, ethnicity, the age when
deformity was first noted, the age at the examination, and the body mass index
was recorded. Frontal and sagittal plane deformities were analyzed by one
examiner using full-length standing radiographs. The association of body mass
index with various demographic and deformity parameters was then analyzed.
Results: Over an eight-year period, forty-five patients with
sixty-five limbs affected by Blount disease were identified. Seventeen
children (twenty-seven limbs) had early-onset Blount disease, and twenty-eight
children (thirty-eight limbs) had late-onset disease. Fifteen of the children
with early-onset disease and twenty-six of those with late-onset disease were
overweight. There was no significant relationship between body mass index and
gender, ethnicity, or laterality. The children with early-onset disease tended
to have a lower body mass index but a greater magnitude of radiographic
deformities compared with the children with late-onset disease. Greater varus
malalignment (r = 0.74, p < 0.0001) and tibial procurvatum (r = -0.79, p =
0.002) were noted with an increasing body mass index in the early-onset, but
not the late-onset, group of patients. Irrespective of the age at onset, the
correlation of body mass index with frontal and sagittal plane deformities was
stronger in extremely obese children (body mass index of =40).
Conclusions: There is a significant relationship between the
magnitude of obesity and biplanar radiographic deformities in children with
the early-onset form of Blount disease and in those with a body mass index of
=40. These clinical findings are consistent with the literature concerning
the effect of compressive forces on growth at the proximal tibial physis.
Level of Evidence: Prognostic Level II. See Instructions
to Authors for a complete description of levels of evidence.