Incidence of distal femoral and distal tibial deformities in infantile and adolescent Blount disease

The purpose of this study was to assess distal femoral and tibial deformity in patients with infantile and adolescent Blount disease. This was a retrospective review of patients at the authors' institution diagnosed with Blount disease. Thirty-eight patients (21 in the infantile group and 17 in the adolescent group) met the study criteria. Measurements of the anatomic lateral distal femoral angle (aLDFA), anatomic lateral distal tibial angle (aLDTA), and tibiofemoral angle (TFA) were made from long-leg radiographs. The results of the infantile and adolescent measurements were compared with each other and to a normal database. Intraobserver and interobserver error was determined. The adolescent aLDFA measurements were significantly greater (more varus) than for the infantile group and normal database. The aLDTA (ankle) measurements were not statistically different between the two groups, or from the normal database. Analysis of both intraobserver and interobserver error for the aLDFA and aLDTA showed good reliability.