Mind The Gap Between The Fracture Line And The Length Of The Working Area: A Finite Element Analysis Using An Extramedullary Fixation Model

To determine the ideal working area for a simple transverse fracture line treated with a bridge plate. Methods: A 2-D finite element analysis of a hypothetical femur was performed for the quantitative evaluation of a large-fragment titanium alloy locking plate based on the principle of relative stability in a case of a simple transverse diaphyseal fracture. Two simulations (one case of strain and another case of stress distribution) were analyzed in three unique situations according to the von Mises stress theory. Load distributions were observed when the bone was subjected to a single vertical load of 1,000. N. Results: The longer the length of the implant flexion, which coincided with the working area of the plate, the greater the flexion of the implant. The highest concentrations of stress on the plate occurred in the region around the screws closest to the bone gap. The closer the screws to the fracture site, the greater the demands on the plate. Conclusion: When using a large-fragment titanium alloy locking plate to stabilize a simple transverse fracture based on the principle of relative stability (bridge plate), the distance between the proximal and distal screws closest to the fracture line must be long. The farther away this fixation is, the lower the stress on the plate and the greater the dissipation of force in the form of deflection. © 2017 Sociedade Brasileira de Ortopedia e Traumatologia

Finite Element Analysis Of The Equivalent Stress Distribution In Schanz Screws During The Use Of A Femoral Fracture Distractor

To evaluate the mechanical stress and elastic deformation exercised in the thread/shaft transition of Schanz screws in assemblies with different screw anchorage distances in the entrance to the bone cortex, through the distribution and location of tension in the samples.An analysis of 3. D finite elements was performed to evaluate the distribution of the equivalent stress (triple stress state) in a Schanz screw fixed bicortically and orthogonally to a tubular bone, using two mounting patterns: (1) thread/shaft transition located 20. mm from the anchorage of the Schanz screws in the entrance to the bone cortex and (2) thread/shaft transition located 3. mm from the anchorage of the Schanz screws in entrance to the bone cortex. The simulations were performed maintaining the same direction of loading and the same distance from the force vector in relation to the center of the hypothetical bone. The load applied, its direction, and the distance to the center of the bone were constant during the simulations in order to maintain the moment of flexion equally constant. The present calculations demonstrated linear behavior during the experiment. It was found that the model with a distance of 20. mm between the Schanz screws anchorage in the entrance to the bone cortex and the thread/shaft transition reduces the risk of breakage or fatigue of the material during the application of constant static loads; in this model. the maximum forces observed were higher (350. Mpa). The distance between the Schanz screws anchorage at the entrance to the bone cortex and the smooth thread/shaft transition of the screws used in a femoral distractor during acute distraction of a fracture must be farther from the entrance to the bone cortex, allowing greater degree of elastic deformation of the material, lower mechanical stress in the thread/shaft transition, and minimized breakage or fatigue. The suggested distance is 20. mm. © 2016 Sociedade Brasileira de Ortopedia e Traumatologia

Subtrochanteric and Distal Femur Fractures in a Patient with Femoral Shaft Fracture Malunion and Knee Disarticulation: A Rare and Challenging Case Report

This study aims to describe a rare and challenging case of a patient who presented ipsilateral subtrochanteric and distal femur fractures due to low‑energy trauma. The peculiarity of this case is the presence of femoral shaft fracture malunion and knee disarticulation in the same limb resulting from an accident suffered 30 years ago. The patient underwent femoral diaphyseal osteotomy and fixation of the subtrochanteric and distal femur fractures with a long cephalomedullary nail and distal femur locking plate, respectively. Despite the magnitude of the surgical procedure, all fractures healed, preserving the femoral length with the absence of infection and clinical complications. There was an improvement of the preinjury function attributed to the osteotomy of the femoral diaphyseal, which alleviated the anterior thigh discomfort.Keywords: Amputation, Distal femur fracture, Femoral shaft fracture, Femur, Femur  fractures, Fracture fixation, Fracture malunion, Fractures, Intramedullary nail, Knee disarticulation,  Subtrochanteric fractur

Proximal Humeral Fractures: An Understanding Of The Ideal Plate Positioning

Purpose The present study aims to evaluate if the bicipital groove can be used as a parameter for ideal plate positioning in proximal humeral fixation applying locking compression plate. Method The authors questioned whether the bicipital groove can be used as a parameter for ideal plate positioning applying locking compression plate for proximal humeral fractures. A method using the bicipital groove as the main parameter was developed using computed tomography scan (CT-scan). Seventy shoulders presenting fracture absence were used to calculate proper plate positioning, allowing the largest area for locked screw placement into the humeral head. Intraclass correlation coefficient and Bland and Altman graphics calculated intra-observer reliability for CT-scan evaluation. Results All observers presented satisfactory plate positioning using this method. The mean differences for observers were close to zero, suggesting high interobserver reproducibility. A significant (p <0.0001) intra-observer agreement existed for the three evaluators. Observer 2 agreement was the strongest (ICC = 0.98), showing almost perfect reproducibility measurement, followed by observer 3 (ICC = 0.84) with good reproducibility, and lastly observer 1 demonstrated moderate degree agreement (ICC = 0.47). Conclusion Considering the CT-scan analysis, the bicipital groove can be used as a parameter for ideal plate positioning in proximal humeral fractures. This method demonstrated satisfactory intra-observer reproducibility. Adopting this method, longer and better distributed screw placement provides more stable fixation for proximal humeral fractures. © 2014 SICOT aisbl