Natural course of excessive genu varum without underlying pathology in children

Background: Despite genu varum’s status as a common pediatric problem, there remain no serial studies investigating the natural course of excessive physiologic genu varum in children. This study, therefore, aims to identify the natural course of the anatomical tibiofemoral angle (aTFA) in children with excessive physiologic genu varum without any underlying pathological conditions. Materials and methods: Between 1997 and 2008, among 70 children who had been referred from a primary hospital to evaluate angular deformity of the knee, 29 consecutive limbs (10 bilateral and 9 unilateral) of 19 healthy Korean children with excessive physiologic genu varum equal to or greater than 2 standard deviations (SDs) of the aTFA at their initial visit until all children were 6 years of age. We analyzed the value of the aTFA as well as the changes in patterns, and compared our findings with results from previous studies. Results: The mean aTFA at the initial visit was 18° varus (range: 9° to 36°), the mean age of normalization was 3.2 years, and the mean value of the aTFA was varus 17.2° at the age of 1 year, followed by a steady decrease to 0° at almost the age of 3.3 years. Starting at the age of 4 years, the aTFA was a mean of 5.2° genu valgum and gradually changed until the age of 6 years, where it was sustained at an average of 3.4° genu valgum. Conclusion: Excessive physiological genu varum exceeding 2 SD in young Korean children improved spontaneously without the need for prosthetics or orthotics.


Introduction
Genu varum is a common pediatric problem that results in consultations regarding the need for surgery. Although in the majority of cases, genu varum is physiologic and resolves spontaneously, physicians need to differentiate between physiologic angular variations and pathological conditions that require special evaluation and treatment [1][2][3][4][5][6]. Although physiological changes in knee alignment are well established, inexperienced physicians cannot be confident of spontaneous recovery and may recommend ineffective and harmful intervention, such as bracing, in cases of excessive physiologic genu varum [6][7][8]. Several studies have been conducted to investigate mean values and overall physiologic changes in the anatomical tibiofemoral angle (aTFA) by age [9][10][11][12][13]. To our knowledge, however, there have been no serial studies investigating the natural course of excessive physiologic genu varum in children. Therefore, we conducted this study to identify the mean values and natural course of the aTFA in excessive physiologic genu varum exceeding more than 1 standard deviation (SD) from the normal value for the aTFA in Korean children [12]. Afterward, we compared our findings with recently reported generalized overall changes in the aTFA in Korean children as well as findings of studies in other countries [2,6,[8][9][10][11][12][13][14][15][16].

Materials and methods
A retrospective study approved the deliberation of the ethics committee (IRB No. 2013-07-058) from September 6, 2013, to September 5, 2014. Between 1997 and 2008, among 70 children who were referred to our hospital for excessive genu varum at the recommendation of a primary physician or the request of a concerned parent, we reviewed 29 consecutive limbs (10 bilateral and 9 unilateral) of 19 healthy Korean children (11 boys and 8 girls) with excessive physiologic genu varum equal to or greater than 2 SDs of the aTFA at their initial clinical visit and were monitored until all children were 6 years of age, procuring all necessary follow-up data for the children throughout this period. We defined excessive physiologic genu varum as the presence of genu varum of more than 2 SDs and without any underlying pathological conditions. Patients whose genu varum was associated with underlying pathological conditions and who had experienced bracing or the use of an insole were excluded.
The children were grouped according to age, and their chronological age was rounded off to the nearest integer, similar to the method of a previous study regarding the development of normal aTFA in Korean children [12]. In this study, those whose ages ranged from 2 years and 7 months to 3 years and 6 months were placed in the group of 3-yearolds.
In general, full-length standing teleroentgenograms were obtained with the patient standing and the patella pointing straight ahead, indicating the neutral position of the lower extremity. However, for participants who were too young to stand, radiographs were obtained in the supine position. The degree of varus was defined as the bisecting angle between the intramedullary lines of the femur and the tibia. The serial tibiofemoral angle (TFA) was measured (146 measurements) with the use of a Picture Archiving and Communication System (PACS) network (Marosis, DICOH version 3.0; INFINITT, Seoul, Korea) and the average was used for subsequent analysis. Serial aTFAs were measured and compared with the results from previous studies [8]. All measurements were made by two examiners using standard techniques to minimize inter-and intra-examiner bias. The neutralization time of the aTFA and the difference between neutralizing times of the aTFA by gender were analyzed. The changing pattern of the aTFA was assessed and compared with findings from previous studies.
Statistical analysis was performed using SPSS software package 15.0 (IBM, Armonk, NY, USA). To examine patients' baseline characteristics, we analyzed the aTFA and descriptive statistics. To determine the correlation between the TFA and various parameters such as age, sex, duration until normalization, and various values of the aTFA in different ethnic groups, we used the independent t-test and one-way analysis of variance. The mean, SD, and 95% confidence intervals were calculated for age and sex. Statistical significance was set at a value of p < 0.05. All statistical analysis was performed by a single statistician.

Results
The mean age of participants at the initial office visit was 17.7 months (range: 9 to 36 months), and the mean duration of follow-up was 40.9 months (range: 10 to 70 months). The mean aTFA at the initial visit was 18° (range, 9° to 36°), and the mean time elapsed from the initial visit to normalization was 20.3 months. The mean age of normalization was 3.2 years. Regarding changes in aTFA according to age, the mean aTFA was 17.2° varus at 1 year, followed by a steady decrease to an aTFA of 0° at almost 3.3 years. At the age of 4 years, the aTFA was 5.2° of valgus and gradually changed until the age of 6 years, where it remained at an average of 3.4° genu valgum (Figure 1).
The overall pattern of the chronological changes in the aTFA was similar to that found in previous studies; however, the physiological genu varum was converted to genu valgum at between 3 and 4 years of age. Neutralization of the aTFA (TFA = 0°) was seen at an average of 3.3 years of age. Moreover, there was no period of the peak valgus at age 3 to 4 years in a normative pattern. The final average TFA was 3.4° valgus after six years of follow-up. All limbs spontaneously recovered to the normal range for the aTFA when the participants were 6 years of age ( Figure 2).

Discussion and conclusions
Genu varum is a common pediatric concern prompting referrals to specialists to address parents' doubts. Whether the varus positioning is caused by a transient physiologic condition or by pathological conditions such as infantile tibia vara (Blount disease), rickets, or focal fibrocartilaginous dysplasia, accurate diagnosis is critical because treatment and prognosis differ per etiology [17].
Age-related overall patterns in TFA change, along with mean values and normal ranges of TFAs in growing children of different ethnic The overall pattern of the chronological changes in the anatomical tibiofemoral angle was similar to that found in previous studies; however, the physiological genu varum was converted to genu valgum at between 3 and 4 years of age groups, have already established by several researchers [6,9,10,[12][13][14]16]. Overall chronological changes and spontaneous resolution of physiologic genu varum have been documented by many excellent studies [7][8][9]18,19]. However, it is not easy for inexperienced orthopedic surgeons to be confident that excessive physiologic genu varum will spontaneously resolve. Thus, we investigated the natural course of excessive genu varum to confirm whether it always spontaneously resolves.
In the evaluation of knee alignment, less invasive and less expensive clinical methods have been used, including measurement of the TFA and the intermalleolar and intercondylar distance [6,9,[14][15][16]20]. However, we used radiological analysis for children with excessive physiologic genu varum because it was necessary to obtain more accurate radiological references [10][11][12][13]18], to rule out underlying pathological conditions, to investigate serial changes in the aTFA objectively, and to compare results with the normative data on chronological changes in knee angles that have already been studied using radiographs.