The effects of total hip arthroplasty (THA) on pelvic parameters and lumbar lordosis in hip osteoarthritis secondary to developmental dysplasia of the hip (DDH)

Objective: To evaluate the effects of total hip arthroplasty(THA) on sagittal alignment of the lumbosacral spine and pelvis in patients with hip osteoarthritis secondary to developmental dysplasia of the hip(DDH) during mid- to long-term follow-up. Methods: Between 2015 and 2022, 47 of 187 patients who underwent unilateral THA for DDH met inclusion criteria.According to the Crowe classification, 27 patients with Type 1–2 were assigned to Group A and 20 with Type 3–4 to Group B. The cohort included 39 females and 8 males (mean age 47 years, range 18–70) with a mean follow-up of 3.4 years. Pre- and postoperative standing lateral radiographs were analyzed for lumbar lordosis, sacral slope, pelvic tilt, pelvic obliquity, and pelvic incidence. Clinical evaluation included low-back and hip VAS, Back Pain Index, Oswestry Disability Index, and Harris Hip Score. Results: Group B showed a significant postoperative reduction in pelvic tilt (25°→13°, p=0.04). Other radiologic parameters showed no significant differences (p>0.05). Across groups, low-back and hip VAS decreased, and functional scores improved significantly without intergroup differences (p = 0.0001). Positive correlations existed among spinopelvic parameters, while negative correlations were found between these parameters and VAS scores (p<0.05). Conclusion: THA corrects excessive pelvic anteversion in Crowe Type 3–4 hips, whereas lumbar lordosis remains unchanged. Despite minimal radiologic change, pain and function improved markedly. Pelvic incidence remained a stable spinopelvic parameter after THA for DDH-related osteoarthritis. Keywords: Developmental Dysplasia of the Hip; Total Hip Arthroplasty; Pelvic Parameters; Lumbar Lordosis; Sagittal Balance; Crowe Classification.