TIBIOFEMORAL ANGLE DEVELOPMENT IN A COHORT OF NIGERIAN CHILDREN DURING THE FIRST THREE YEARS OF LIFE

Abstract

Knowledge of Tibio-Femoral Angle (TFA) development facilitates clinical decisions in managing childhood knee mal-alignment. Findings from cross-sectional studies on TFA development in Nigerian children vary in values and the age at which the initial varus changes to valgus pattern. It has been suggested that longitudinal studies would provide more reliable description of TFA development in children than cross-sectional surveys. This longitudinal study was therefore conducted to examine the TFA development in a cohort of Nigerian children during the first three years of life, compare TFA between boys and girls and determine the relationship between TFA and selected anthropometric variables. One hundred and fifty two apparently healthy children without any obvious congenital deformities were consecutively recruited within 21 days of life into this study from three infant welfare clinics in Sagamu Local Government Area. The TFA was measured directly using a universal goniometer and indirectly by measuring Inter-Condylar Distance (ICD) and Inter-Malleolar Distance (IMD). Limb and trunk lengths were measured using non-extensible measuring tape. Height and weight were measured using infantometer/height meter and weighing scale respectively. Measurements were taken on each child at first contact and monthly until three years of age. Data were analysed using descriptive statistics, t-test and Pearson’s correlation at p = 0.05. Participants were 71 boys and 81 girls. At first contact, TFA pattern was varus with a mean of 13.2±3.80. Using goniometry, TFA pattern remained varus in all children until 15 months of age; decreased gradually and turned neutral (00) at 18 months. The knee v angle became valgus in 85.0% of the children at 19 months, and in all the children at 33 months. Mean valgus knee angle rose from -2.4±2.50 at 19 months to -8.5±2.50 at 27 months and decreased slightly to -7.7±2.20 at 36 months. Using ICD/IMD, TFA showed a similar course of development from maximum ICD (varus) at first contact (2.5±0.7cm) to minimum ICD (0.1±0.4cm) at 15 months. At 16 months, the children had predominantly valgus pattern (IMD) with few remaining as varus (16.7%) and neutral (23.3%). Ninety percent of children had changed to valgus pattern by 19 months. The mean IMD (valgus) increased from -0.1±0.8cm at 16 months to -2.0±1.5cm at 29 months. There was no significant difference in the TFA values by sex or side of lower limb. The TFA values by goniometry correlated significantly with those by ICD/IMD (r = 0.77) and each of weight (r = -0.77), height (r = -0.84), trunk length (r = -0.88) and limb length (r = -0.88). The tibiofemoral angle development in the cohort of Nigerian children was maximum varus during the first 21 days of life, thereafter decreased and became neutral at 18 months, turned valgus at 19 months, increasing till three years of age; similar to that described for American and Korean children. A valgus angle before 15 months of age may be considered unusual. The tibiofemoral angle values herein presented may be used when assessing lower limb alignment in Nigerian children during the first three years of life.