Mechanical behavior of fixation components for periprosthetic fracture surgery.
BACKGROUND
Reliable periprosthetic fracture treatment needs detailed knowledge on the mechanical behavior of the fixation components used. The holding capacity of three conventional fixation components for periprosthetic fracture treatment was systematically investigated under different loading directions.


METHODS
Locking compression plates were fixed to a 7 cm long part of diaphyseal fresh frozen human femur with either a single 1.7 mm cerclage cable, a 5.0mm monocortical or a bicortical locking screw (n=5 per group). Constructs were loaded in lateral, torsional and axial direction with respect to the bone axis in a load-to-failure test. Corresponding stress distribution around the screw holes was analyzed by finite element modeling.


RESULTS
Both screw fixations revealed significantly higher stiffness and ultimate strength in axial compression and torsion compared to the cerclage (all P<0.01). Ultimate strength in lateral loading and torsion was significantly higher for bicortical screws (mean 3968 N SD 657; mean 28.8 Nm SD 5.9) compared to monocortical screws (mean 2748 N SD 585; mean 14.4 Nm SD 5.7 Nm) and cerclages (mean 3001N SD 252; mean 3.2 Nm SD 2.0) (P≤0.04). Stress distribution around the screw hole varied according to the screw type and load direction.


CONCLUSIONS
Fixation components may be combined according to their individual advantages to achieve an optimal periprosthetic fracture fixation.
AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos-Platz, Switzerland; Dept. of Trauma, Hand and Reconstructive Surgery, University Hospital Jena, Erlanger Allee 101, D-07747 Jena, Germany. Electronic address: mark.lenz@med.uni-jena.de.
Mark
M
Lenz
Stephan Marcel
SM
Perren
Boyko
B
Gueorguiev
Dankward
D
Höntzsch
Markus
M
Windolf
D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D018483:Diaphyses / Q000503:physiopathology / Q000601:surgery; D004548:Elasticity; D019544:Equipment Failure Analysis; D005269:Femur / Q000503:physiopathology / Q000601:surgery; D020342:Finite Element Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D016268:Internal Fixators; D008422:Materials Testing; D008962:Models, Theoretical; D057068:Periprosthetic Fractures / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery*; D013314:Stress, Mechanical; D054159:Torsion, Mechanical; D016474:Weight-Bearing
Bicortical screw; Cable cerclage; Monocortical screw; Periprosthetic fracture