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Seasonal variation in children with developmental dysplasia of the hip
1Department of Orthopaedic Surgery, Indiana School of Medicine, James Whitcomb Riley Children's Hospital, Indiana University, ROC 4250, 705 Riley Hospital Drive, Indianapolis, IN, 46202, USA, rloder@iupui.edu.
Insights
Developmental dysplasia of the hip (DDH) shows some seasonal birth variation, partly supporting the cold weather clothing hypothesis. However, diverse birth patterns suggest complex genetic and environmental interactions influence DDH etiology.
Area of Science:
- Orthopedics
- Pediatrics
- Epidemiology
Background:
- Developmental dysplasia of the hip (DDH) is a condition with suspected links to seasonal birth patterns.
- Previous theories suggest a higher incidence in infants born during colder months, potentially due to clothing practices.
Purpose of the Study:
- To investigate seasonal variations in DDH births at the author's institution.
- To compare these findings with existing literature using rigorous mathematical analysis.
Main Methods:
- A case series of 424 children with DDH (1993-2012) was analyzed for birth month.
- Cosinor analysis was employed to detect temporal patterns.
- Data from 22,936 additional cases from the literature were incorporated for a comprehensive analysis.
Main Results:
- A non-uniform distribution of birth months was observed in both the institutional and combined literature data.
- Cosinor analysis of institutional data revealed double peaks in March and October.
- Across 23,360 total cases, 70.3% showed a single winter peak, while other patterns (no variation, summer peak, double peaks) were also noted.
Conclusions:
- Findings partially support the cold weather/tight clothing hypothesis for DDH etiology.
- The presence of non-winter peaks and varied seasonal patterns suggests other factors are involved.
- Heterogeneity in genetic factors interacting with environmental and metabolic influences likely contributes to the diverse seasonal variations observed in DDH.
Background:
It has been postulated that developmental dysplasia of the hip (DDH) is more frequent in infants born in the winter months. It was the purpose of this study to ascertain if there was any seasonal variation in DDH at the author's institution and compare/contrast our results with those in the literature using rigorous mathematical fitting.
Methods:
All children with DDH treated at the author's institution from 1993 to 2012 were identified. The month of birth was recorded and temporal variation was analyzed using cosinor analysis. Similar data from the literature was analyzed.
Results:
There were 424 children (363 girls, 61 boys). An additional 22,936 children were added from the literature for a total of 23,360. Pearson's Chi-square test demonstrated a non-uniform distribution in the month of birth for both our 424 children as well as the combined literature series in both the Northern and Southern hemispheres. Cosinor analysis of the 424 children demonstrated double peaks in mid-March and mid-October. For the entire 23,360 children, no seasonal variation was observed in 2,205 (9.4 %), a single winter peak in 16,425 (70.3 %), a single summer peak in 1,280 (5.5 %), and double peaks in the spring and autumn in 3,450 (14.8 %).
Conclusions:
This study partly supports the hypothesis of tight clothing/cold temperature as one factor in the etiology of DDH with the tighter clothing/swaddling increasing the risk of DDH. However ~20 % of the DDH births demonstrated a non-winter peak. The single summer and double spring/autumn peaks, as well as in those series where no seasonal variation was noted, refutes the cold winter clothing hypothesis. Perhaps these different patterns in seasonal variation represent the heterogeneity of the genetic factors in DDH interacting with external factors (temperature and clothing) and internal factors (metabolic). Further study will be required to understand these different patterns in DDH seasonal variation.
Level Of Evidence:
IV-case series.
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