Biomechanical optimization of the far cortical locking technique for early healing of distal femur fractures

Ahmed Sarwar; Aaron Gee; Habiba Bougherara; Paul R T Kuzyk; Emil H Schemitsch; Radovan Zdero

doi:10.1016/j.medengphy.2021.02.003

Biomechanical optimization of the far cortical locking technique for early healing of distal femur fractures

Med Eng Phys. 2021 Mar:89:63-72. doi: 10.1016/j.medengphy.2021.02.003. Epub 2021 Feb 5.

Authors

Ahmed Sarwar¹, Aaron Gee², Habiba Bougherara¹, Paul R T Kuzyk³, Emil H Schemitsch⁴, Radovan Zdero⁵

Affiliations

¹ Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada.
² Orthopaedic Biomechanics Lab, Victoria Hospital, (Room A6-144), 800 Commissioners Road, London, ON N6A-5W9, Canada.
³ Department of Surgery, University of Toronto, Toronto, ON, Canada.
⁴ Orthopaedic Biomechanics Lab, Victoria Hospital, (Room A6-144), 800 Commissioners Road, London, ON N6A-5W9, Canada; Department of Surgery, Western University, London, ON, Canada.
⁵ Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada; Orthopaedic Biomechanics Lab, Victoria Hospital, (Room A6-144), 800 Commissioners Road, London, ON N6A-5W9, Canada; Department of Surgery, Western University, London, ON, Canada; Department of Mechanical and Materials Engineering, Western University, London, ON, Canada. Electronic address: radovan.zdero@lhsc.on.ca.

PMID: 33608126
DOI: 10.1016/j.medengphy.2021.02.003

Abstract

This finite element study optimized far cortical locking (FCL) technology for early callus formation in distal femur fracture fixation with a 9-hole plate using FCL screws proximal to, and standard locking screws distal to, the fracture. Analyses were done for 120 possible FCL screw configurations by varying FCL screw distribution and number. A hip joint force of 700 N (i.e. 100% x body weight) was used, which corresponds to a typical 140 N "toe-touch" foot-to-ground force (i.e. 20% x body weight) suggested to patients immediately after surgery. Increased FCL screw distribution (i.e. shorter plate working length) caused a decrease at the medial side and an increase at the lateral side of the axial interfragmentary motion (AIM), mildly affected shaft and condylar cortex Von Mises max stress (σ_MAX), increased plate σ_MAX, and decreased shaft FCL screw and condylar locking screw σ_MAX. Increased FCL screw number decreased AIM and σ_MAX on the shaft cortex, condylar cortex, plate, and FCL screws, but not condylar screws. The optimal FCL screw configuration had 3 FCL screws in plate holes #1, 5, and 6 (proximal to distal) for optimal AIM of 0.2 - 1 mm and reduce shear fracture motion, thereby encouraging early callus formation.

Keywords: Biomechanics; Distal femur fracture; Far cortical locking; Optimization.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Biomechanical Phenomena
Bone Plates
Bone Screws*
Femoral Fractures* / surgery
Femur / diagnostic imaging
Femur / surgery
Fracture Fixation, Internal
Humans