Background: Patients with borderline acetabular dysplasia are a controversial patient population in hip preservation, as some have primarily impingement-based symptoms and others have instability-based symptoms. Borderline dysplasia is most commonly defined as a lateral center-edge angle (LCEA) of 20° to 25°. However, its prevalence has not been well established in the literature.
Purpose: To (1) define the prevalence of borderline hip dysplasia in the general population as well as in populations presenting with hip pain using a systematic review and meta-analysis of the literature and (2) describe differences between male and female patients as well as differences in prevalence from that of classic acetabular dysplasia.
Study design: Systematic review; Level of evidence, 3.
Methods: A systematic review of the literature was performed using search terms to capture borderline dysplasia, or studies reporting prevalence by LCEA. The search yielded 1932 results, of which 11 articles met inclusion criteria and were included in the final systematic review. Studies were grouped by patient cohort as (1) asymptomatic general population, (2) asymptomatic targeted population (eg, athletes in a specific sport), and (3) symptomatic hip pain population. The reporting of prevalence rates by subject or by hip was recorded. In a study, the rates of borderline dysplasia were compared with those of classic acetabular dysplasia (LCEA, <20°).
Results: The 11 studies included 19,648 hips (11,754 patients). In the asymptomatic general population, the pooled estimate of the prevalence of borderline dysplasia was 19.8% by subject and 23.3% by hip (range, 16.7%-46.0%). The targeted subpopulation group included 236 athletes with subgroups in ballet, football, hockey, volleyball, soccer, and track and field with prevalence ranging from 17.8% to 51.1%. The prevalence of borderline dysplasia in groups presenting with hip pain was 12.8% (range, 12.6%-16.0%). Borderline acetabular dysplasia was 3.5 times more common than classic acetabular dysplasia in the asymptomatic general population.
Conclusion: This study demonstrated a prevalence of borderline dysplasia of 19.8% to 23.3% in the asymptomatic general population. Additionally, an estimated prevalence of 12.8% of hips in symptomatic patients highlights the common decision-making challenges in this population.
Keywords: acetabular dysplasia; borderline hip dysplasia; prevalence.
© The Author(s) 2022.