Implications of the spinopelvic relationship for total hip arthroplasty

Abstract

Total hip arthroplasty is one of the most successful procedures in medicine. It aims to replicate the anatomy of the patient's hip joint to allow mobilization and reduce pain. To maintain stability, the changes in pelvic positioning between sitting and standing need to be considered. The spinopelvic relationship normally adjusts the position of the pelvis on sitting to antevert the acetabulum and reduce the amount of flexion at the hip. When this relationship is affected by normal variation or pathological changes, this can have implications for the arthroplasty surgeon. An anteverted or retroverted pelvis can lead to edge loading, wear, impingement and dislocation. Therefore, strategies to identify patients at risk are important to reduce complications. Sitting and standing lateral radiographs, and measurement of the change in sacral slope, can identify those with a stiff spinopelvic junction. Mitigation has mainly focused on adjusting the placement of the acetabular component within safe zones. However, use of dual mobility components, increasing offset and head size, have also been identified as possible methods. To date, there is a lack of prospective evidence or biomechanical studies assessing hip arthroplasty in these patients.