Biomechanical study of a unilocking T-plate system for prophylactic internal fixation of the radial osteocutaneous donor site using the XXXX tibia model.

@entity1298 @entity742 @entity174
Prophylactic internal fixation (PIF), with a bone plate in either the anterior (over the section defect) or posterior (on intact cortex) position, has substantially reduced the incidence of @entity174 at the donor site of the radial osteocutaneous free flap. This study uses the @entity742 tibia model to compare the effectiveness of new T-shaped titanium plates utilising a unilocking screw system with a 3.5 mm steel plate and bicortical screw fixation system commonly applied for PIF. Forty matched pairs of adult @entity742 tibias were tested in torsion and 4-point bending. An osteotomised bone was significantly weaker (p<0.001) than an intact bone in both bending and torsion with a mean loss of 77% and 64% of strength respectively. The tibia withstood much greater bending loads. All of the constructs significantly strengthened an osteotomised bone by a factor of 1.73-2.43 times in bending and 1.54-2.63 in torsion. The 2.4 mm T-plate in an anterior position (section) was the baseline against which other plates in differing positions were compared. The 3.5 mm T-plate section, @entity1298 section and @entity1298 cortex constructs had 41%, 30% and 2% greater mean bending strengths respectively but only the 3.5 mm T-plate section result approached statistical significance (p=0.06). In torsion the @entity1298 section, 3.5 mm T-plate section and @entity1298 cortex constructs had 56% (p=0.01), 27% (p=0.06) and 25% greater mean strengths respectively. When compared to an intact bone the mean bending strength restored by the @entity1298 section (84%) and 3.5 mm T-plate section (87%) constructs was greatest and effectively restored the strength to that of an intact bone (100%). In torsion the mean strength restored by the @entity1298 section (62%), @entity1298 cortex (44%), 3.5 mm T-plate section (40%) and 2.4 mm T-plate (36%) remained significantly less than an intact bone. All of the plate constructs significantly strengthened an osteotomised bone but overall the 3.5 mm T-plate section and @entity1298 section were the strongest constructs and most suitable for PIF. The lighter 2.4 mm T-shaped titanium plate was least effective. The strongest reinforcement in bending and torsion was the 3.5 mm T-plate section and @entity1298 section respectively. The 3.5 mm @entity1298 section plate was significantly stronger (p=0.01) than the 3.5 mm T-plate in torsion and remains the most effective construct for resisting torsional stresses, which are probably the commonest cause of @entity174 in clinical practice.
