Locking Plate in Proximal Tibial Fracture: A Correlation between the Coronal Alignment of Tibia and Joint Screw Angle

PURPOSE: The purpose of this study is to evaluate the relationship between the angle formed between the proximal most screw through the locking compression plate-proximal lateral tibia (LCP PLT) and the joint line, and to evaluate if this angle can be used intraoperatively as an assessment tool to determine normal alignment of the tibia in the coronal plane. MATERIALS AND METHODS: There are two parts to this study: in the first part, LCP PLT was applied to 30 cadaveric adult tibia. The angle between the joint line and the proximal most screw was measured and termed as the 'joint screw angle' (JSA). In the second part, 56 proximal tibial fractures treated with LCP PLT were retrospectively studied. Two angles were measured on the radiographs, the medial proximal tibial angle (MPTA) and the JSA. Their relationship was analyzed statistically. RESULTS: The average JSA was 1.16 degrees in the anatomical study. Statistical analysis of the clinical study showed that the normal MPTA had a direct correlation with an acceptable JSA. CONCLUSION: We therefore conclude that the JSA can be used intraoperatively to assess the achievement of a normal coronal axis.

Effect of Fracture Gap on Biomechanical Stability of Compression Bone-Plate Fixation System after Bone Fracture Augmentation

PURPOSE: The goal of this study using the biomechanical test was to evaluate the mechanical stability of the bone-plate fixation system according to changes of the fracture gap sizes and widths. MATERIALS AND METHODS: For mechanical test, four types with different fracture models simulating the clinical situations were constructed depending on the gap size (FGS, mm) and the gap width (FGW, %) at the fracture site: 0 mm/0%, 1 mm/100%, 4 mm/100%, 4 mm/50%. For analyzing the effects of fracture gap on the biomechanical stability of the bone-plate fixation system, 4-point bending test was performed under all same conditions. RESULTS: It was found that the fracture gap sizes of 1 and 4 mm decreased mechanical stiffness by about 50~60% or more. Furthermore, even without fracture gap size, 50% or more fracture gap width considerably decreased mechanical stiffness and suggested the possibility of plate damage through strain results. CONCLUSION: Our findings suggested that at least 50% contact of the fracture faces in a fracture surgery would be maintained to increase the mechanical stability of the bone-plate fixation system.

A Finite Element Analysis of Biomechanical Stability of Compression Plate Fixation System in according to Existing of Fracture Gap after Bone Fracture Augmentation

PURPOSE: This study using the finite element analysis (FEA) focused on evaluating the biomechanical stability of the LC-DCP in accordance with existing of the fracture gap at the facture site after bone fracture augmentation. MATERIALS AND METHODS: For FEM analysis, total eleven types with different fracture models considering clinical fracture cases were constructed according to the fracture gap sizes (0, 1, 4 mm)/widths (0, 25, 50, 75, 100%). Limited contact dynamic compression plate (LC-DCP) fixation system was used in this FEM analysis, and three types of load were applied to the bone-plate fixation system: compressive, torsional, bending load. RESULTS: The results in FEM analysis showed that the 1, 4 mm fracture gap sizes and 75% or more fracture gap widths increased considerably the peak von Mises stress (PVMS) both the plate and the screw under all loading conditions. PVMS were concentrated on the center of the LC-DCP bone-plate, and around the necks of screws. CONCLUSION: Based on the our findings, we recommend at least 50% contact of the fracture faces in a fracture surgery using the compression bone-plate system. Moreover, if x-ray observation after surgery finds 100% fracture gap or 50% or more fracture gap width, supplementary measures to improve biomechanical stability must be taken, such as restriction of walking of the patient or plastering.

Biomechanical Analysis of Hybrid External Fixation for the Distal Tibial Fractures: A FEM Study

PURPOSE: To analyze the biomechanical effects of different frame configurations of the hybrid external fixators for distal tibial fractures on the frame stiffness and stress distribution with a finite element method (FEM). MATERIALS AND METHODS: Five configurations were simulated: Group I: two wires with convergence angle of 60degrees, Group II: 3rd wire on a bisector axis of the group I. Group III: two wires with 30degrees. Group IV: 3rd wire on a bisector axis. Group V: two wires with 30degree and a half pin on the distal articular fragment. Each group was simulated under compression, torsion, anterior-posterior and lateral-medial bending load. Stiffness, stress and deformation values were calculated. RESULTS: The overall stiffness was increased by 15~30% with the addition of a third wire, and by 150~400% with a anteromedial half pin on the articular fragment. The half pin decreased the stress level of the frame by about 43% and the deformation of the 5/8 ring by about 30%. CONCLUSION: The addition of a half pin on the articular fragment is not only a method of increasing the stiffness but also a way of decreasing the stress concentration and the deformation of the frame.