The effects of tibia profile, distraction angle, and knee load on wedge instability and hinge fracture: A finite element study.
Several plate systems for high tibial osteotomy (HTO) have been developed to stabilize the opening wedge of an osteotomized tibia. Among them, the TomoFix system, having a quasi-straight and T-shaped design, has been widely adopted in the literature. However, this system is implemented by inserting a lag (i.e., cortical) screw through the proximal combi-hole, to deform the plate and pull the distal tibia toward the plate. This process potentially induces plate springback and creates an elastic preload on the osteotomized tibia, especially at the lateral hinge of the distracted wedge. Using the finite-element method, this study aims to investigate the contoured effect of lag-screw application on the biomechanical behavior of the tibia-plate construct. Two tibial profiles (normal and more concave), three distraction angles (6°, 9°, and 12°), and three knee loads (intraoperative: contouring plate; postoperative: weight and nonweight bearing) are systematically varied in this study. The wedge instability and fracture risk at the lateral hinge are chosen as the comparison indices. The results show the necessity of preoperative planning for a precontoured procedure, rather than elastic deformation using a lag screw. Within the intraoperative period, a more concave tibial profile and/or reduced distraction angle (i.e., 6° or 9°) necessitate a higher compressive load to elastically deform the plate, thereby deteriorating the lateral-hinge fracture risk. A precontoured plate is recommended in the case that the proximal tibia is highly concave and the distraction angle is insufficient to stretch the tibial profile.
Department of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan; Department of Orthopaedics, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan. Electronic address: 3689792@yahoo.com.tw.
Pei-Wei
PW
Weng
Department of Orthopaedics, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan. Electronic address: chiaxian@gmail.com.
Chia-Hsien
CH
Chen
Graduate Institute of Biomedical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei, Taiwan. Electronic address: nevereverro@gmail.com.
Chu-An
CA
Luo
Department of Orthopaedic Surgery, National Taiwan University Hospital, Taipei, Taiwan. Electronic address: drjssun@ntuh.gov.tw.
Jui-Sheng
JS
Sun
Department of Orthopaedics, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan. Electronic address: tsuangyh@gmail.com.
Yang-Hwei
YH
Tsuang
Department of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan. Electronic address: ckcheng2009@gmail.com.
Cheng-Kung
CK
Cheng
Graduate Institute of Biomedical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei, Taiwan. Electronic address: orthodent.cax@gmail.com.
Shang-Chih
SC
Lin
D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery; D010027:Osteotomy / Q000009:adverse effects; D013314:Stress, Mechanical; D013977:Tibia / Q000502:physiology* / Q000601:surgery; D013978:Tibial Fractures / Q000209:etiology / Q000503:physiopathology; D016474:Weight-Bearing
Finite element; High tibial osteotomy; Lateral hinge; Precontoured