The Association between Gender and Familial Prevalence of Hip Dysplasia in Danish Patients

The development of hip dysplasia is associated with several risk factors. 1 of these risk factors is gender, since 80% of patients with symptomatic hip dysplasia are females. Another risk factor for hip dysplasia is familial predisposition of hip dysplasia. Several studies indicate that the risk of hip dysplasia is increased with familial prevalence of hip dysplasia. However, little is known about the association between the familial prevalence and gender and the development of hip dysplasia.

Purpose
The aim of the study was to estimate the prevalence of hip dysplasia among relatives to Danish patients with hip dysplasia operated with periacetabular osteotomy (PAO), and the degree of relationship of affected family members. Furthermore, to assess the association between gender and family predisposition in the same group of patients.

Method
The study is a cross-sectional study, with a descriptive and an analytical part. The study population consists of 676 patients drawn from a clinical database of patients operated with PAO at Aarhus University hospital from 1998 to 2014. Information about gender, operated hip side and age was collected from the clinical PAO database, while information about familial prevalence was collected through questionnaires. The association between gender and familial prevalence of hip dysplasia was presented as the prevalence proportions ratio (PPR), tested by χ2 test. Stratification was conducted for the variables age and operated hip side, with the Mantel-Haenszels analytical method, and tested for statistical significance by χ2.
The familial prevalence of hip dysplasia in the study population was 30% (95% CI, 27%-34%), with 73% reporting affected first-degree relatives. Females have 32% increased risk of familial prevalence of hip dysplasia compared to males, but this difference in risk was not statistically significant (p = 0.10).

Conclusions
The study shows that females have 32% increased familial prevalence of hip dysplasia compared to males, but the increased prevalence was not statistically significant probably due to the low power of the study.