The Hip-Spine Relationship in Total Hip Arthroplasty: How to Execute the Plan

Patients with spinopelvic pathology, including lumbar spine stiffness and sagittal spinal deformity, are at increased risk for postoperative complications, including instability, dislocation, and revision after total hip arthroplasty (THA). Recent evidence has suggested that the Lewinnek safe zone should no longer be considered an appropriate target for all patients, especially those with spinopelvic pathology, as the safe zone is a dynamic rather than static target. There are 2 distinct issues for arthroplasty surgeons to consider: lumbar spinal stiffness and sagittal spinal deformity, each of which has its own management.

In order to manage patients with spinopelvic pathology undergoing THA, a basic understanding of spinopelvic parameters, including sagittal balance, sacral slope, and anterior pelvic plane, is essential. Techniques outlined in this manuscript describe a systematic preoperative work-up and intraoperative management of acetabular component positioning according to patient-specific spinopelvic parameters, ensuring optimal component placement and a reduced risk for impingement, instability, and poor postoperative outcomes.

Evaluation of each patient's spinopelvic parameters informs patient classification according to the Hip-Spine Classification for THA. Patient classification is determined by the presence of spinal stiffness and spinal deformity, with corresponding scoring and classification into one of the 4 categories used to determine risk for postoperative dislocation, define patient-specific cup positioning, and create their functional safe zone.

A simple 2-step preoperative assessment with measurements of the anterior pelvic plane and the sacral slope on standing and seated lateral X-rays will identify patients at high risk for postoperative dislocation due to spinal deformity and/or stiffness. Accounting for spinopelvic pathology and adhering to the Hip-Spine Classification guidelines for acetabular component positioning can help reduce the burden of instability and revisions in this complex patient population.