HIP DYSPLASIA: RISK FACTORS AND THEIR ASSOCIATED DIAGNOSTIC SEVERITY

Developmental dysplasia of the hip (DDH) affects 1–3% of all infants, making it the most common pediatric hip disorder. The spectrum of DDH spans from mild dysplasia of the acetabulum to a hip that is dislocated and irreducible, resulting in severe long-term issues including pain, limping, and early-onset osteoarthritis of the hip. Previous studies have focused on identifying risk factors for DDH, what remains unknown however is the relationship between DDH risk factors and the severity of dysplasia at diagnosis. The aim of this study was to determine whether certain DDH risk factors had a stronger association with severity of hip dysplasia at time of diagnosis. Data from a global, prospective registry of patients diagnosed with DDH was analyzed. Clinical and radiologic diagnostic data was utilized to correlate DDH risk factors with severity of dysplasia. For this study, severity was characterized by four categorical variables: clinical (dislocated and irreducible hip), ultrasound (a-angle < 4 5-degrees, femoral head coverage < 3 5%), and radiograph (IHDI classification three or four). Potential risk factors included breech presentation, family history, female, first born, and swaddling history, and were assessed using univariable and multivariable logistic regression models. Multivariable models included all risk factors with an additional adjustment for the contributing centre as a random effect. Out of the 4682 patients analyzed, 1515 were born breech, 644 had an immediate family history of DDH, 3878 were female, 2511 were first born, and 2133 had a history of swaddling. From a pathology severity standpoint, 573 patients clinically had a dislocated and irreducible hip, 954 had an alpha angle None of the risk factors were identified as having an increased association with a dislocated and irreducible hip on clinical examination, or with an IHDI Grade of three or four. In contrast, female and first-born infants had significant positive associations with ultrasound parameters of an alpha-angle of In addition to clinical examination, ultrasound remains one of the main diagnostic and monitoring hip dysplasia modalities. Our study identified that first born and female infants were more likely to have ultrasound-defined severe DDH at diagnosis. In North America, selective ultrasound screening is performed for infants with specific DDH risk factors, neither of which are female nor first born. Therefore, the stronger association between female and first born patients and DDH severity in comparison to other risk factors may be attributed to their omission from the selective screening process. While it may not be feasible to scan all first born and female infants by ultrasound, the results from our study emphasize the importance of clinically screening those of this profile at birth and thereafter to ensure enrollment into adequate monitoring and treatment programs.