Structure-mechanical analysis of various fixation constructs for basicervical fractures of the proximal femur and clinical implications; finite element analysis

Joon-Woo Kim; Chang-Wug Oh; Beom-Soo Kim; Se-Lin Jeong; Gu-Hee Jung; Dong-Hyun Lee

doi:10.1016/j.injury.2022.12.004

Structure-mechanical analysis of various fixation constructs for basicervical fractures of the proximal femur and clinical implications; finite element analysis

Injury. 2023 Feb;54(2):370-378. doi: 10.1016/j.injury.2022.12.004. Epub 2022 Dec 5.

Authors

Joon-Woo Kim¹, Chang-Wug Oh¹, Beom-Soo Kim², Se-Lin Jeong³, Gu-Hee Jung⁴, Dong-Hyun Lee⁵

Affiliations

¹ Department of Orthopaedic surgery, School of Medicine, Kyungpook National University, Kyungpook National University Hospital, 130 Dongduk-ro, Jung-gu, Daegu 41944, Republic of Korea.
² Department of Orthopedic Surgery, Keimyung University Dongsan Hospital, Keimyung University School, 1035, Dalgubeol-daero, Dalseo-gu, Daegu 42601, Republic of Korea.
³ Institute of Health sciences (Medical ICT convergence research center), college of medicine, Gyeongsang national university, Jinju, Republic of Korea.
⁴ Institute of Health sciences (Medical ICT convergence research center), college of medicine, Gyeongsang national university, Jinju, Republic of Korea; Department of Orthopaedic surgery, Gyeongsang national university, college of medicine and Gyeongsang national university Changwon hospital, 1, Samjeongja-ro, Seongsan-gu, Changwon-si, Gyeongsangnam-do, 51472, Republic of Korea. Electronic address: jyujin2001@hotmail.com.
⁵ Department of Orthopaedic surgery, Gyeongsang national university, college of medicine and Gyeongsang national university Changwon hospital, 1, Samjeongja-ro, Seongsan-gu, Changwon-si, Gyeongsangnam-do, 51472, Republic of Korea.

PMID: 36529550
DOI: 10.1016/j.injury.2022.12.004

Abstract

Objective: This present study was conducted to determine the structural-mechanical stability of various fixation constructs through finite element (FE) analysis following simulation of a basicervical fracture and to introduce the clinical implications.

Materials and methods: We simulated fracture models by using a right synthetic femur (SAWBONES®). We imported the implant models into ANSYS® for placement in an optimal position. Five assembly models were constructed: (1) multiple cancellous screws (MCS), (2) FNS (femoral neck system®), (3) dynamic hip screw (DHS), (4) DHS with anti-rotation 7.0 screw (DHS + screw), and PFNA-II (Proximal Femoral Nail Antirotation-II®). The femur model's distal end was completely fixed and 7° abducted. We set the force vector at a 3° angle laterally and 15° posteriorly from the vertical ground. Analysis was done using Ansys® software with von Mises stress (VMS) in megapascals (MPa) and displacement (mm) RESULTS: The displacements of the proximal femur were 10.25 mm for MCS, 9.66 mm for DHS, 9.44 mm for DHS + screw, 9.86 mm for FNS, and 9.31 mm for PFNA-II. The maximum implant VMS was 148.94 MPa for MCS, 414.66 MPa for DHS, 385.59 MPa for DSH + screw, 464.07 MPa for FNS, and 505.07 MPa for PFNA-II. The maximum VMS at the fracture site was 621.13 MPa for MCS, 464.14 MPa for DHS, 64.51 MPa for DHS + screw, 344.54 MPa for FNS, and 647.49 MPa for PFNA-II. The maximum VMS at the fracture site was in the superior area with the high point around the posterior screw in the MCS, anterosuperior corner in the DHS, the posteroinferior site of the FNS, and posterosuperior site around the entry point in the PFNA-II. In the DHS + screw, the stresses were distributed evenly and disappeared at the maximum VMS fracture site.

Conclusion: Based on the fracture site and implant's stress distribution, the model receiving the optimal load was a DHS + screw construct, and the FNS implant could be applied to anatomically reduced fractures without comminution. Considering the high-stress concentration around the entry point, a PFNA-II fixation has a high probability of head-neck fragment rotational instability.

Keywords: Basicervical fracture; Finite element analysis; Internal fixation; Proximal femur.

MeSH terms

Bone Screws
Femoral Neck Fractures* / surgery
Femur
Finite Element Analysis
Fracture Fixation, Internal
Hip Fractures* / surgery
Humans