CLINICAL PRESENTATION OF RICKETS IN CHILDREN WITH ANGULAR KNEE DEFORMITIES IN LAGOS, NIGERIA: A PRELIMINARY STUDY

Abstract

Background: Rickets is a metabolic bone disease due to poor bone mineralization in children. There are few current studies detailing the clinical presentation and biochemical parameters in urban settings in sub-Saharan Africa. The aim is to document the clinical and biochemical presentation of rickets in children with angular deformities of the knees in an urban setting in Nigeria.

Methodology: This is a prospective observational study. A group of 44 children with angular deformities of the knees were recruited for this study between 1st January and 31^st December 2017 and divided into two groups. The first group consisted of 22 children who had radiological evidence of rickets and the second comprised 22 age-matched children who showed no radiological evidence of rickets. Biographic data, history (exposure to sunlight, breastfeeding), clinical data (weight, height, knee deformities and head circumference) and biochemical findings (serum calcium, phosphorus, alkaline phosphatase, total protein, albumin and vitamin D) were recorded in a Microsoft Excel spreadsheet (Microsoft Office 365) and analysed using SPSS version 23.

Results: The mean ages of the rickets group (RG) (54.86 months) and the non-rickets control group (NRG) (52.50 months) were well matched. The male/female ratio was 2:1 in the RG group and 1:1 in the NRG group. The mean Body Mass Index (BMI) for age Z- score was statistically higher among rickets cases compared to the non-rickets cases. There was no significant difference in weight for age Z score of both groups, but the height for age Zscore was significantly lower in the rachitic group. Head circumference was significantly higher in the NRG. The knee deformities were bilateral in 81.8% of the RG and 77.3% in the NRG. The commonest deformity of the knees seen in both groups was bilateral valgus deformity but there were far more windswept knees in the rickets group.

The mean serum calcium level was low in the RG and normal in the NRG but the difference was not statistically significant. Phosphorus levels were low in both groups without any statistically significant difference. The mean total serum protein was lower in the RG but normal in the NRG. Although the mean serum albumin level was significantly higher in the NRG, both groups were within normal limits. Serum Alkaline Phosphatase was significantly higher in the rachitic group. The vitamin D (25 (OH) D) distribution among the RG and NRG was the same.

Conclusion: In this study, bilateral genu valgum appears to be the commonest knee deformity seen in rickets, but windswept deformities also occur frequently. Calcium, rather than vitamin D deficiency appears to be the main aetiological factor in rickets. A larger series is required to validate these findings.