Generalized joint hypermobility and functional recovery after THA for unilateral Hartofilakidis type C developmental dysplasia of the hip: a retrospective cohort study

Background Generalized joint hypermobility (GJH) is common in developmental dysplasia of the hip (DDH) and may affect recovery after total hip arthroplasty (THA) for Hartofilakidis type C, but its impact on the trajectory of postoperative functional recovery in this severe subgroup has not been clearly characterized. Methods We retrospectively reviewed patients aged 18–40 years who underwent THA for unilateral Hartofilakidis type C DDH (2018–2023). GJH was defined as a Beighton score ≥ 5. All procedures used a direct anterior approach with proximal femoral osteotomy for exposure and selective femoral shortening at the lesser trochanter level when reduction would otherwise impose excessive neurovascular tension or unacceptable residual leg-length discrepancy (LLD). Radiographic parameters and LLD were assessed. Harris Hip Score (HHS) was recorded preoperatively and at 1, 3, 6, and 12 months. Longitudinal HHS was analysed using a linear mixed-effects model; effect sizes were quantified by Cohen’s d and partial η 2 . Results Fifty-eight patients were included (21 GJH, 37 non-GJH). Postoperative LLD was reduced without a between-group difference. Cup position at 6 months was similar; femoral offset tended to be higher in GJH ( p = 0.057). Femoral shortening distance was smaller in GJH ( p < 0.001). Observed HHS was lower in GJH at 1–6 months ( p < 0.001) but similar at 12 months. The linear mixed-effects model (LMM) showed significant time, group, and time × group effects ( p < 0.001). Adjusted between-group differences were largest at 1 month and progressively diminished, becoming non-significant at 12 months. One dislocation occurred in the GJH group; no revisions were required. Conclusions In young adults with unilateral Hartofilakidis type C DDH, GJH did not compromise 12-month hip function after THA but was associated with a slower early recovery trajectory, with the largest deficit during the first 1–3 postoperative months.