Biomechanical design using in-vitro finite element modeling of distal femur fracture plates made from semi-rigid materials versus traditional metals for post-operative toe-touch weight-bearing

Gee, Aaron; Bougherara, Habiba; Schemitsch, Emil H.; Zdero, Radovan

Affiliations

¹Orthopaedic Biomechanics Lab, Room A6-144, Victoria Hospital, 800 Commissioners Road, London N6A5W9, Canada

²Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Canada

³Department of Surgery (Division of Orthopaedic Surgery), Western University, London, Canada

⁴Department of Mechanical and Materials Engineering, Western University, London, Canada

Abstract and keywords

This proof-of-concept study designs distal femur fracture plates from semi-rigid materials vs. traditional metals for toe-touch weight-bearing recommended to patients immediately after surgery. The two-fold goal was to (a) reduce stress shielding (SS) by increasing cortical bone stress thereby reducing the risk of bone absorption and plate loosening, and (b) reduce delayed healing (DH) via early callus formation by optimizing axial interfragmentary motion (AIM). Finite element analysis was used to design semi-rigid plates whose elastic moduli E ensured plates permitted AIM of 0.2 - 1 mm for early callus formation. A low hip joint force of 700 N (i.e. 100% x body weight) was applied, which corresponds to a typical 140 N toe-touch foot-to-ground force (i.e. 20% x body weight) recommended to patients after surgery. Analysis was done using 2 screw materials (steel or titanium) and types (locked or non-locked). Steel and titanium plates were also analyzed. Semi-rigid plates (vs. metal plates) had lower overall femur/plate construct stiffnesses of 508 - 1482 N/mm, higher cortical bone stresses under the plate by 2.02x - 3.27x thereby reducing SS, and lower E values of 414 - 2302 MPa to permit AIM of 0.2 - 1 mm thereby reducing DH.

Keywords: Biomechanics; Distal femur fracture; Semi-rigid material; Plate; Toe-touch

Links

DOI: 10.1016/j.medengphy.2020.11.015

PubMed: 33461680

WoS: 000612061300012

History

Received: 2020-01-27

Revised: 2020-11-29

Accepted: 2020-11-29

Online: 2020-12-2

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Cited By (1)

Year	Entry
2022	Djuricic A, Gee A, Schemitsch EH, Quenneville CE, Zdero R. Biomechanical design of a new percutaneous locked plate for comminuted proximal tibia fractures. Med Eng Phys. June 1, 2022;104:103801.