In patients with variable changes in pelvic inclination, total hip arthroplasty (THA) is required for accurate cup installation to prevent dislocation. Here we reported the use of THA for hip ankylosis due to juvenile idiopathic arthritis (JIA) and variable pelvic inclination with changes in posture. The patient was a 55-year-old woman, who had received medical treatment for JIA until the age of 14 year. She had been examined two years previously for bilateral leg pain and gait disturbance. Clinically, the lumbar spine had degenerative changes and the left hip joint was ankylosed at a 50-degree -flexed position, causing severe lordosis of the pelvis and lumbar spine and more severe lordosis during changes in posture. We treated the lumbar spine by laminectomy, and then THA was performed under a navigation system. Postoperatively, the patient was relieved of her symptoms and her ambulatory ability was improved. Anteversion of the pelvis with changes in posture remains, but the large femoral head has ensured that no dislocation has occurred up to the present.
In cases of variable pelvic inclination due to changes in posture, use of a navigation system is useful intraoperatively for accurate cup installation, and a large femoral head matches any postoperative changes in pelvic inclination.