Contributions of the Distal Femur and Proximal Tibia to Idiopathic Genu Varum and Genu Valgum in Adolescents.

Backgroud: Different from adults, adolescents with genu varum or valgum can be treated with hemi-epiphysiodesis. We conducted a study to report our recent experience of treating idiopathic genu varum and valgum with clinical relevance to planning of hemi-epiphysiodesis. The aim of this study was to compare the varus and valgus groups focusing on the contribution of the distal femur and proximal tibia to the deformities.

Methods: Among patients who visited the outpatient clinic during the recent 4 years, adolescents with genu varum (the varus group) or valgum (the valgus group) greater than 5° were included. The mechanical lateral distal femoral angle (mLDFA) and medial proximal tibial angle (MPTA) were measured. The contribution to deformity (%) in each of the distal femur and the proximal tibia was calculated.

Results: One hundred twenty patients and their 120 legs (randomly selected in bilateral cases) were included. In the varus group (n = 51), the mean hip-knee-ankle alignment was varus 7.1° (range, 5.1°-12.1°). The contribution to deformity was 74.1% ± 27.6% at the proximal tibia (MPTA, 81.9° ± 2.0°) and 14.9% ± 25.1% at the distal femur (mLDFA, 88.1° ± 1.7°). In the valgus group (n = 69), the mean alignment was valgus 6.6° (range, 5.1°-11.9°). The contribution was 69.8% ± 30.8% at the distal femur (mLDFA, 82.4° ± 2.1°) and 33.1% ± 27.8% at the proximal tibia (MPTA = 89.2° ± 1.9°). In subgroup analyses, the MPTA was significantly lower in the varus ≥ 8.4° group than the varus < 8.4° group. The mLDFA was significantly lower and the frequency of MPTA > 91.5° was significantly higher in the valgus ≥ 7.7° group than the valgus < 7.7° group.

Conclusions: Genu varum was mainly associated with deformity of the proximal tibia, whereas genu valgum was related to deformities of the distal femur and proximal tibia. Considering the predominant deformity of the proximal tibia, performing hemi-epiphysiodesis only at the proximal tibia is ideal in most adolescents with genu varum.