Comparison of Acetabular Cup Fixation With and Without Screws in Total Hip Arthroplasty for Sickle Cell Disease: A CT Based Migration Analysis

Total Hip Arthroplasty (THA) is an effective treatment for end-stage hip disease; however, in patients with Sickle Cell Disease (SCD), altered bone biology poses unique challenges to acetabular component fixation. Poor bone quality, sclerosis, infarcts, and trabecular abnormalities may compromise press-fit stability, leading surgeons to use supplemental acetabular screws based on intraoperative judgment. Despite widespread practice, objective evidence supporting screw fixation in SCD is lacking, and existing studies are largely confined to populations with normal bone biology and rely on low-precision radiographic methods.

This prospective cohort study aims to compare early acetabular cup stability in SCD patients undergoing primary uncemented THA with and without supplemental screw fixation using a CT- based markerless migration analysis. The primary objective is to quantify three-dimensional acetabular cup migration at one year postoperatively. Secondary objectives include evaluation of cup inclination and version changes, assessment of radiological stability using Moore’s signs adapted to CT imaging, and comparison of functional outcomes using the Modified Harris Hip Score (mHHS).

The study will be conducted at the Department of Orthopaedics, AIIMS Raipur, over a two-year period following Institutional Ethics Committee approval. Adult patients (>18 years) with avascular necrosis of the femoral head secondary to SCD undergoing primary unilateral THA will be included. Patients undergoing revision THA, those with AVN due to other etiologies, prior pelvic surgeries, major acetabular defects requiring augments, or inability to comply with follow-up or CT imaging will be excluded. Convenience sampling will be used, with the decision to use screws made intraoperatively based on cup stability.

All patients will undergo standardized preoperative evaluation, surgery, and postoperative rehabilitation. A baseline CT scan of the pelvis and hips will be obtained within one week of surgery, followed by a repeat CT scan at one year. CT-based migration analysis will be performed using 3D Slicer software. The pelvis will serve as the fixed reference body through rigid registration using Iterative Closest Point (ICP) algorithms. Cup migration will be quantified by calculating centroid displacement in superior–inferior, medial–lateral, and anterior–posterior directions, along with rotational changes in inclination and version. Radiological stability will be assessed using Moore’s signs adapted for CT imaging. Functional outcomes will be evaluated using mHHS preoperatively and at 3, 6, and 12 months postoperatively.

Based on prior RSA data, a sample size of 17 patients per group (34 total) has been calculated to detect a clinically meaningful difference in migration.Statistical analysis will compare migration parameters, radiological stability, and functional outcomes between screw and no-screw groups, with correlation analyses to assess relationships between migration and clinical outcomes. This study aims to provide objective, high-precision evidence to guide acetabular fixation strategies in SCD patients undergoing THA