An experimental study on stress-shielding effects of locked compression plates in fixing intact dog femur.

BACKGROUND: In orthopedic application, stress-shielding effects of implant materials cause bone loss, which often induces porosis, delayed bone healing, and other complications. We aimed to compare the stress-shielding effects of locked compression plate (LCP) and limited-contact dynamic compression plate (LC-DCP) in dogs with plate-fixed femurs. METHODS: Bilateral intact femurs of 24 adult dogs were fixed by adult forearm 9-hole titanium plates using minimally invasive plate osteosynthesis (MIPPO) technology, with LCP on the left and LC-DCP on the right femurs. Dogs were sacrificed at 6 weeks, 12 weeks, and 24 weeks after surgery, and bone specimens were used to evaluate the efficacies of different fixing methods on bones through X-ray, dual-energy X-ray absorptiometry (DEXA), histology, MicroCT, and biomechanics analyses. RESULTS: X-ray results showed significant callus formation and periosteal reaction in the LC-DCP group. Bone cell morphology, degree of osteoporosis, and bone mineral density (BMD) changes of the LCP group were significantly better than that of the LC-DCP group. MicroCT results showed that the LCP group had significantly reduced degree of cortical bone osteoporosis than the LC-DCP group. Tissue mineral density (TMD) in the LCP group was higher than that in the LC-DCP group at different time points (6 weeks, 12 weeks, and 24 weeks). Biomechanics analyses demonstrated that the compressive strength and flexural strength of bones fixed by LCP were better than that by LC-DCP. CONCLUSIONS: Stress-shielding effects of LCP are significantly weaker than that of LC-DCP, which is beneficial to new bone formation and fracture healing, and LCP can be widely used in clinic for fracture fixation.

Effect of bending direction on the mechanical behaviour of 3.5 mm String-of-Pearls and Limited Contact Dynamic Compression Plate constructs.

OBJECTIVE: To compare the bending properties of String-of-Pearls® (SOP) and Limited Contact Dynamic Compression Plate® (LC-DCP) constructs in orthogonal bending directions. METHODS: 3.5 mm SOP and LC-DCP plates were fixed to a bone model simulating a comminuted tibial fracture. Specimens were non-destructively tested in both mediolateral and craniocaudal bending for 10 cycles. Bending stiffness and total angular deformation were compared using parametric analyses (p <0.05). RESULTS: For both constructs, stiffness was significantly less when bending moments were applied against the thickness of the plates (mediolateral bending) than against the width (craniocaudal bending). When compared to the mediolateral plane, bending constructs in the craniocaudal plane resulted in a 49% (SOP group) and 370% (LC-DCP group) increase in stiffness (p <0.001). Mediolateral bending stiffness was significantly greater in the SOP than the LC-DCP constructs. Conversely, in craniocaudal bending, SOP constructs stiffness was significantly less than that of the LC-DCP constructs. The differences between the two constructs in total angular deformation had an identical pattern of significance. CLINICAL SIGNIFICANCE: This study found that SOP showed less variability between the orthogonal bending directions than LC-DCP in a comminuted fracture model, and also described the bi-planar bending behaviour of both constructs. Although not exhibiting identical bending properties in both planes, SOP constructs had a more homogenous bending behaviour in orthogonal loading directions. The difference between the SOP with a circular cross sectional shape compared to the rectangular shape of standard plates is probably responsible for this difference.

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.

The Comparison of LC-DCP versus LCP Fixation in the Plate Augmentation for the Nonunion of Femur Shaft Fractures after Intramedullary Nail Fixation

PURPOSE: The purpose of this study was to evaluate the efficacy of the surgical treatment through the comparison of LC-DCP (Limited Contact-Dynamic Compression Plate) versus LCP (Locking Compression Plate) fixation in the plate augmentation for the nonunion of femur shaft fractures after intramedullary nail fixation. MATERIALS AND METHODS: Twenty-four patients with the nonunion of femur shaft fractures after intramedullary nail fixation who underwent plate augmentation were evaluated from Mar. 2001 to Sept. 2005. The group with LC-DCP augmentation was done bicortical screw fixation and the group with LCP was done monocortical fixation. RESULTS: There was one case of nail breakage in LC-DCP group, but sound bony union were achieved uneventfully in all the cases of both group. LCP fixation was slightly superior to LC-DCP fixation in view of the bony union time, operating time, postoperative Hb down, amount of postoperative transfusion, but there was no statistical difference (p>0.05). CONCLUSION: We got the satisfactory results after monocortical LCP augmentation as well as bicortical LC-DCP fixation and have concluded that monocortical LCP fixation was an effective treatment option for nonunion of femur shaft fracture occurred after Intrmedullary nail fixation.

Comparison of LC-DCP versus LCP for Internal Fixation of Humeral Shaft Fractures in Elderly Patient

PURPOSE: To compare outcomes of humeral shaft fractures fixed with locking compression plate and those fixed with dynamic compression plate in elderly patients. MATERIALS AND METHODS: Nineteen consecutive elderly patients with a fracture of the humeral diaphysis were evaluated retrospectively. Ten patients had been fixed with LC-DCP, and nine had been fixed with LCP. Radiological and clinical results were compared and comparison of implants was done. RESULTS: Loosening of the plate occurred in one case each from the LCP group and the LC-DCP group. The rest of the patients achieved union uneventfully without any complications. Union rate, clinical score and hardware were not significantly different between the two groups. One patient who developed loosening in the LC DCP underwent reoperation whereas one patient with loosening in the LCP was successfully managed conservatively. CONCLUSION: Principle of fracture fixation was more important than plate selection in humeral shaft fracture of elderly patient.