Acta chirurgiae orthopaedicae
et traumatologiae Čechoslovaca

Acta Chir Orthop Traumatol Cech. 2023; 90(5):301-313 | DOI: 10.55095/achot2023/036

Biomechanical Comparison of the Roof Step Cut Technique with the Bulk Bone Graft Technique During Total Hip Arthroplasty for Hip Dysplasia: a Finite Element AnalysisOriginal papers

L. ZHANG¹, R. ALKENTAR², S. MANÓ³, J. SZABÓ¹, T. MANKOVITS⁴, Z. CSERNÁTONY¹

¹ Department of Orthopedic Surgery, Faculty of Medicine, University of Debrecen, Hungary

² Doctoral School of Informatics, Faculty of Informatics, University of Debrecen, Hungary

³ Laboratory of Biomechanics, Department of Orthopedic Surgery, Faculty of Medicine, University of Debrecen, Hungary

⁴ Department of Mechanical Engineering, Faculty of Engineering, University of Debrecen, Hungary

PURPOSE OF THE STUDY: Different techniques have been reported to reconstruct the deficient acetabulum during total hip arthroplasty (THA). The purpose of this study was to compare the biomechanical features of the bulk bone graft (BBG) technique (Harris acetabular plasty) and the Roof Step Cut (RSC) technique using finite element analysis.

MATERIAL AND METHODS: Based on a female patient's dysplastic hip CT scan, 3D models were assembled according to the two techniques. For the Harris technique, an irregular BBG was sculpted from a solid sphere, while for the RSC technique, the graft was sculpted into a step-cut shape with a similar size. Each graft was fixed with two compression screws at two different angles (0° and 45°). Four finite element models were used to compare the von Mises stress distribution and total deformation of the grafts and the screws. The pressure and sliding distances of the contacts between the bone graft, metal cup and acetabular host bone were also analyzed.

RESULTS: For both of the bone grafts and the screws, compared to the Harris models, the maximum stress of the RSC models was significantly lower (16.56 MPa, 25.50 MPa vs 97.13 MPa, 112.72 MPa) and the total deformation was significantly smaller (0.0096 mm, 0.0089 mm vs 0.022 mm, 0.018 mm). 45° inserted screws generated higher stress at the end of the screws and on the outside of the bone graft. In case of 0° inserted screws, the maximum value was mainly located in the middle of the screws, inside the screw channel as well as at the contact area between the graft and the host bone. At all analyzed contacts, the RSC technique shows significantly lower pressure and sliding distances, irrelevant to the screw's insertion angle. In comparison, the model of BBG with 45° screws showed a significant sliding effect and higher contact pressure.

CONCLUSIONS: Compared with the BBG technique, the step-shaped graft of the RSC technique could significantly reduce the maximum stress and deformation of the graft and the screws, and decrease the pressure and sliding distance between the bone graft, metal cup and the acetabular host bone. The angle of screw placement affects the location of stress and deformation.

Keywords: developmental dysplasia of the hip, total hip arthroplasty, acetabular reconstruction, bone graft, finite element analysis

Published: November 11, 2023  Show citation