Does Deformity Severity Dictate Which Side Initially Develops Symptoms in Bilaterally Dysplastic Hips?

Most patients with developmental dysplasia of the hip (DDH) have bilateral deformities, yet have asymmetric symptom development that is not well understood. This study aimed to identify relationships between deformity severity and symptom asymmetry in patients with bilateral DDH. Hip geometry from N = 230 patients was measured using lateral center-edge angle (LCEA), acetabular inclination, neck-shaft angle, alpha angle, and femoral version, and compared between initially symptomatic and contralateral hips. Patients were grouped into those with a "more dysplastic hip" (n = 133, based on >3° side-to-side LCEAs) or similar side-to-side deformities. Self-reported activity levels were also compared between those whose symptomatic hips were more severely deformed and those whose contralateral hips were more severely deformed. Symptomatic hips had more severe acetabular deformities, based on the LCEA and acetabular inclination, in 80% of subjects (p < 0.001). The only femoral measure to reveal differences between symptomatic and contralateral hips was neck-shaft angle; most patients had more severe angles on their symptomatic side (p = 0.003) though with a small effect (d = 0.14). Thus, acetabular deformities appear to drive asymmetric symptom development more than femoral deformities. Among the 20% of patients with more deformed contralateral hips, activity levels were not different from those with more deformed symptomatic hips. While self-reported activity was not linked to symptom asymmetry, factors not captured, such as limb dominance and activity type, may contribute. These findings further understanding of disease progression and symptom onset in bilateral DDH and can inform anticipatory interventions to reduce pain and promote long-term joint health.