2017 ISAKOS Biennial Congress ePoster #1525
How Could Plate Geometry and Screw Insertion be Optimized for a Balanced Stability of the Fixator and the Lateral Hinge in Open Wedge High Tibial Osteotomy
Yong-Seuk Lee, MD, PhD, Prof., Seongnam, Kyung-gi KOREA, REPUBLIC OF
Oui Sik Yoo, MS, Seoul KOREA, REPUBLIC OF
Myung Chul Lee, MD, PhD, Prof., Seoul KOREA, REPUBLIC OF
Young Woong Jang, MS, Seoul KOREA, REPUBLIC OF
Seoul National University Bundang Hospital, Seongnam, Kyung-gi, KOREA, REPUBLIC OF
FDA Status Not Applicable
By improving plate geometry and insertion angle of the screw, newly developed LCFit OWHTO System is considered as more favorable fixation system regarding balanced stability between fixative and lateral hinge.
The stable fixation of the bony fragment and the maintenance of the lateral hinge as a fulcrum could be two important mechanical prerequisites for accomplishing a successful open wedge high tibial osteotomy (OWHTO). For this, the plate should be contoured to the postoperative bony geometry and the screws should be inserted to the direction of the hinge area to support the lateral hinge.
This study was conducted to compare the stabilities of our new fixator (LCfit) and the commonly used fixator (Tomofix) in terms of the fixator and the lateral hinge using a finite element (FE) analysis. The hypothesis of this study is that our new fixator could optimize for the balanced stability of the fixator and the lateral hinge.
Study design: Descriptive Laboratory Study
Virtual surgery models were made using a CT data of 69 OWHTO. The physiological load conditions were applied on top of the tibia (=1,400N). We verified the stabilities between the new anatomical plate and the screw and between the tibial lateral hinge portion and the screw to evaluate the balanced stability. We also evaluated the alterations in the stress distribution characteristics of the two FE models. The region of interest (ROI) was determined at the anterolateral, lateral, and posterolateral areas, including the lateral hinge and the PVMS was evaluated.
The stresses measured at the three ROIs were generally lower in the LCfit than in the TomoFix. The stress value of the Tomofix was 87.1Mpa, which was 3.7 times bigger than that of the LCfit (23.1Mpa). The stress around the lateral hinge area sharply increased or decreased in the TomoFix model, but only mildly decreased in the LCfit. The PVMS (236.1MPa) in the TomoFix was measured at the distal fragment of the tibia, whereas that of the LCfit (249.4 MPa) was measured at the linked wedge block. Generally, the stress in the TomoFix tended to be concentrated in the screw and it showed an average of 75.1% higher value than the LCfit.
The analysis result herein showed that by improving the plate geometry and the insertion angle of the screw, the newly developed LCfit OWHTO system can be considered as a more favorable fixation system in terms of the balanced stability between the fixator and the lateral hinge. However, this result was obtained only from theoretical models; hence, the need for validation in a controlled clinical setting.
Keywords: Knee, Osteoarthritis, Open wedge high tibial osteotomy, Fixative, Finite element