Effect of Horizontal Medialization of the Hip Center of Rotation on Clinical Outcomes After Total Hip Arthroplasty in Crowe Types I and II Developmental Hip Dysplasia.

BACKGROUND: The objective of our study was to investigate the effect of horizontal medialization of the hip center of rotation (COR) on clinical outcomes after primary unilateral total hip arthroplasty (THA) in patients who had Crowe types I and II developmental dysplasia of the hip (DDH).

METHODS: A total of 189 patients who had Crowe types I and II DDH and underwent primary unilateral THA between January 2017 and December 2024 were retrospectively included. According to the postoperative horizontal COR difference, patients were divided into a horizontal COR reconstruction group (-five millimeters (mm) ≤ horizontal COR difference ≤ five mm, n = 108) and a COR medialization group (horizontal COR difference < -five mm, n = 81). Clinical scores, pain, postoperative limping, and radiographic parameters were compared between groups, whereas complications were summarized descriptively.

RESULTS: Harris Hip Score (HHS), Oxford Hip Score (OHS), and Visual Analog Scale (VAS) pain scores improved significantly after surgery in both groups. There were no significant differences observed between groups in postoperative HHS, OHS, VAS score, or limping. Radiographic analysis showed no significant differences in vertical COR difference, leg-length difference, or femoral offset difference. There was no statistically significant difference in the proportion of patients who had a global offset difference within ± five mm. There were three dislocations in the horizontal COR reconstruction group and two in the medialization group, and no nerve injury, aseptic loosening, periprosthetic fracture, or periprosthetic joint infection was observed.

CONCLUSION: In patients who have Crowe types I and II DDH, when the acetabular cup remained within the true acetabulum, a certain degree of horizontal COR medialization after THA was not observed to be associated with poorer clinical outcomes. With adequate cup coverage and initial stability, a certain degree of horizontal COR medialization may be a clinically acceptable reconstruction strategy.