Protective effect of the thoracic cage on parenchyma in response to trauma direction in blunt thoracic trauma: an experimental study.

BACKGROUND: We aimed to investigate the protective potential of the thoracic cage on the parenchyma in response to blunt trauma from different directions in an animal model. METHODS: Female Wistar albino rats were divided into control, anterolateral, lateral and posterolateral trauma groups, with six rats in each group. A weight of 500 g was dropped from a height of 40 cm on the left hemithorax to produce an energy of 1.96 joules, using a specially designed platform. Respiratory rates and heart rates were noted before and at 0, 1, and 5 minutes after trauma. Twenty-four hours later, the left lungs were excised for wet lung weight measurement, histological examinations and tissue malondialdehyde determination. RESULTS: Severe pulmonary contusion was observed in all trauma groups according to histological parameters. Malondialdehyde was increased in both the lateral and posterolateral groups. Wet lung weight was increased only in the posterolateral trauma group when compared to controls. Histologically, macrophages were increased and mononuclear cell infiltration was significant in the posterolateral trauma group. There were no significant changes in physiological parameters in the groups. CONCLUSION: Lung parenchyma seems to be badly affected after trauma to the posterolateral thoracic wall. Different thoracic regions may respond differently to the same traumatic stress, and this may be related to the biomechanical properties of the thoracic cage.

Mechanical performance of hybrid Ilizarov external fixator in comparison with Ilizarov circular external fixator.

OBJECTIVE: The aim of this study was to determine the stiffness characteristics of the standard and hybrid Ilizarov fixators. DESIGN: Five different frame models (one standard and four hybrid Ilizarov) were designed. Four full rings were used in the standard Ilizarov frame. Two rings were placed proximal and two rings were placed distal to the osteotomy line with two wires at 90 degrees to each other on each ring. The distal tibial fixation of all the hybrid configurations and standard Ilizarov fixator were the same, and only the proximal fixations were different. In hybrid models, different numbers of 90 degrees femoral arches (1-3) were fixed to the proximal segment by using the half-pins with different numbers (2-4) and different angles to each other (45 degrees and 90 degrees ). BACKGROUND: Numerous investigations have been performed to compare the mechanical properties of different frames. The Ilizarov method of fracture fixation and limb lengthening has recently gained international recognition. But its application is difficult in some anatomic localization, so that hybrid ring fixation frames of various configurations are gaining clinical popularity. METHODS: Five different frame models were applied to the sheep tibial bones. The midpoint of the tibial bones was osteotomised and the osteotomy distracted for 2 cm. Four identical samples for each model were created and each identical sample of each model (n=1) were tested four times in axial compression, antero-posterior and medio-lateral bending, and torsion. RESULTS: In standard Ilizarov fixator, axial and bending stiffness was found to be more than all hybrid Ilizarov fixator models. Between the hybrid fixators, higher axial and bending stiffness was found when the number of femoral arches and half-pins were increased. Different angles between the half-pins formed 67% alteration in medio-lateral bending stiffness. No significant difference was found for torsional stiffness between the fixator models. CONCLUSIONS: For optimum fixator stiffness in hybrid fixators, at least three femoral arches and four half-pins must be used and these half-pins should be placed at 90 degrees angles and at different planes to each other. However, it should be remembered that, hybrid fixator models had less axial and bending stiffness than standard Ilizarov fixator model. RELEVANCE: For optimum fixator stiffness in hybrid fixators, at least three femoral arches and four half-pins must be used. However, it should be remembered that, hybrid fixator models had less axial and bending stiffness than standard Ilizarov fixator model.