Title: Helical plating – a novel technique to increase stiffness in defect fractures

Authors: M Lenz, P Varga, D Mischler, B Gueorguiev, K Klos, A Fernandez dell’Oca, P Regazzoni, RG Richards, SM Perren

Address: AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos Platz, Switzerland

E-mail: boyko.gueorguiev at aofoundation.org

Abstract: Single-plate fixation bridging bone defects provokes nonunion and risks plate-fatigue failure due to under- dimensioned implants. Adding a helical plate to bridge the fracture increases stiffness and balances load sharing. This study compares the stiffness and plate surface strain of different constructs in a transverse contact and gap femoral shaft fracture model.
Eight groups of six synthetic femora each were formed: intact femora; intact femora with lateral locking plate; contact and gap transverse shaft osteotomies each with lateral locking plate, lateral locking plate and helical locking plate, and long proximal femoral nail.
Constructs underwent non-destructive quasi-static axial and torsional loading. Plate surface strain evaluation was performed under 200 N axial loading. Constructs with both lateral and helical plates demonstrated similar axial and torsional stiffness– independent of the contact or gap situations – being significantly higher compared to lateral plating (p < 0.01). Torsional stiffness of the constructs, with both lateral and helical plates in the gap situation, was significantly higher compared to this situation stabilised by a nail (p < 0.01). Plate surface strain dropped from 0.3 % in the gap situation with a lateral plate to < 0.1 % in this situation with both a lateral and a helical plate.
Additional helical plating increases axial and torsional construct stiffness in synthetic bone and seems to provide well-balanced load sharing. Its use should be considered in very demanding situations for gap or defect fractures, where single-plate osteosynthesis provides inadequate stiffness for fracture healing and induces nonunion.

Key Words: Double plating, helical plate, locking plate, surface strain, nonunion, fatigue failure.

Publication date: August 19th 2021

Article download: Pages 110-121 (PDF file)
DOI: 10.22203/eCM.v042a08