The Impact of Abduction Orthoses for the Treatment of Hip Dysplasia on the Development of Motor Skills: A Systematic Review and Meta-Analysis

<b>Background:</b> Developmental dysplasia of the hip (DDH) is the most common musculoskeletal condition in infants, and it is routinely managed with abduction orthoses. Despite high treatment success rates, concerns persist regarding potential delays in motor milestone acquisition. This meta-analysis evaluates the impact of orthotic treatment in children with DDH on early motor development. <b>Methods:</b> PubMed, Web of Science, and Embase were screened from inception to 17 February 2025. The review followed PRISMA guidelines. Risk of bias was assessed using the ROBINS-I tool V2 and visualized with the ROBVIS application. Mean differences in motor milestone achievement timepoints were compared in months between the intervention and control groups using a random effects meta-analysis model. A meta-regression was conducted to explore potential moderators of effect size. The protocol was prospectively registered in PROSPERO (ID: CRD42025648186). <b>Results:</b> Four studies, including 952 children, were analyzed-335 were treated for DDH with abduction orthoses, and 617 were healthy controls. Pavlik harness was used in three studies (<i>n</i> = 235), while the Koszla brace was used in one study (<i>n</i> = 100). Children in the orthosis group began walking approximately 0.55 months later than healthy controls (95% CI: 0.40 to 0.70). Sitting was also delayed by 1.11 months (95% CI: 0.76 to 1.47). No significant difference was found for crawling. <b>Conclusions:</b> The use of abduction orthoses may result in a slight, clinically marginal delay in achieving motor milestones, such as sitting and unaided walking. However, given that untreated DDH can lead to severe functional limitations, early intervention with orthoses remains a justified and safe standard of care.