A Patient-specific Navigational Template for Precise Acetabular Placement in Unilateral Total Hip Arthroplasty: A Cadaveric Study

Abstract

Background Total hip arthroplasty (THA) is a widely performed reconstructive surgical intervention. In this paper, we describe a novel patient-specific navigational template to assist in acetabular component implantation in unilateral THA. Methods The template was produced based on data preoperatively acquired with computed tomography (CT) scan. We used the mirror image of the healthy contralateral acetabular anatomical structure to ensure accurate acetabular component implantation in unilateral THA. The surface of the template was designed to conform to the unique contours of the cadaveric acetabular fossa by reverse engineering technology. The orientation of the navigation channel was defined by the acetabular central axis which was determined by the contralateral acetabular centre of rotation, anteversion angle and abduction angle. Each template was formed from acrylate resin by using rapid prototyping (RP) technique. Finally, the template was tested in 20 cadavers scheduled for unilateral THA and postoperative medical imaging was used to evaluate the accuracy and validity of the template. Results During the operation, the acetabular fossa template was easy to obtain in all cases. The abduction angle ( β ) of the cup was (49.9°±4.1°) versus (49.5°±4.7°) on the contralateral side. The anteversion angle (α) of the cup was (17.7° ± 3.1°) versus (18.3°±3.5°) on the contralateral side. In the operative hip, the height of the prosthesis centre(H)was (21.6 mm±2.8 mm) versus (21.9 mm±3.4 mm) in the contralateral side, and the horizontal location of the prosthesis centre(W) was (29.7 mm±3.1 mm) versus (30.90 mm±3.31 mm) in the contralateral side. There was no significant difference in the cup abduction (β) or anteversion (α) angle between the operative and contralateral sides (P=0.7531>0.05 for β and P=0.5996>0.05 for α); In addition, there was no significant difference in the height(H)or horizontal location(W) of the acetabular centre between the operative and contralateral sides (P=0.6494>0.05 for W and P=0.5143>0.05 for H). Conclusion The navigational template is a promising tool for facilitating preoperative planning and intraoperative techniques. With the aid of the template, an acetabular prosthesis can be precisely implanted to the expected position in unilateral THA.