Static and Dynamic Differences in Fixation Stability between a Spacer Plate and a Small Stature Plate Fixator Used for High Tibial Osteotomies: A Biomechanical Bone Composite Study

Abstract

Background. The objective of the present study was to compare mechanical strength and stability of the newly designed spacer plate with the gold standard plate for the treatment of medial knee joint osteoarthritis. Materials and Methods. Ten fourth-generation tibial bone composites underwent a medial open-wedge high tibial osteotomy (HTO) according to standard techniques, using five TomoFix plates and five Contour Lock plates. Static compression load to failure and load-controlled cyclical fatigue failure tests were performed. Forces and horizontal displacements were measured; plastic deformations and dynamic stiffness were determined. Results and Discussion. In all samples, rotation of the tibial head and fracture of the opposite cortex were observed. Behaviors of the specimens under static loading were comparable between groups. Cyclic testing revealed lateral significant higher stiffness until failure for the Contour Lock compared to the TomoFix plate. No visible implant failure was observed in any group. Conclusion. Considering the static analysis, both plates offered sufficient stability under physiologic loads of up to 3000 N. The Contour Lock plate-fixated specimens showed a higher stability during the cyclic testing, supposedly due to the wider distance between the fixation screws.

Biomechanik neuer Implantate für die HTO

“…Die Proben wurden in einem standardisierten Versuchsaufbau in 4 Schritten vorbereitet [18] Published results indicate high fusion rates and good clinical results with the TomoFix™ plate, which is contrary to our findings. A certain amount of interfragmentary motion rather than high mechanical strength and stiffness seem to be important for bone healing which is outside the scope of this paper.…”

Verhinderung einer Fraktur der Gegenkortikalis bei aufklappender Osteotomie

“…Zur Minderung des Frakturrisikos haben Kessler et al [7] bei der lateral zuklappenden HTO das Verfahren [8,[14][15][16]. Eine anteroposteriore Entlastungsbohrung ("hinge drill") am Ende der horizontalen Osteotomie soll die Kapazität des Biegungsscharniers zur elastischen Deformierung erhöhen und im Idealfall Frakturen der Gegenkortikalis vermeiden [7].…”

A pilot hole does not reduce the strains or risk of fracture to the lateral cortex during and following a medial opening wedge high tibial osteotomy in cadaveric specimens

“…Once the specimens were secured in the MTM, they were subjected to a staircase cyclic loading protocol. The system initially applied a sinusoidal waveform between 200 N and 800 N at 1.8 Hz that was incrementally increased by 200 N every 5000 cycles, until failure or to a maximum force of 2400 N. 19 , 20 The lower loads were used to simulate the mean ground reaction forces obtained from in vivo patient data, 18 while the higher forces were used to determine the extreme values. Failure was defined as a breakage of the plate, the lateral cortical hinge, or a complete fracture that resulted in segmental separation.…”