IMPROVED FRACTURE-HEALING WITH LESS RIGID PLATES - A BIOMECHANICAL STUDY IN DOGS

The effect of axial plate flexibility on bone healing was investigated with four experimental plating systems using elastic inserts to manag e their axial flexibility in compression, The plates were tested in 72 dogs that underwent unilateral femoral osteotomy and noncompression p lating on alternate sides, The femurs of 18 dogs were plated with each of the four plating systems: six for 8 weeks, six for 16 weeks, and s ix 6 for 24 weeks. Each osteotomized femur and its contralateral contr ol were removed at the end of the plating periods and tested in multid irectional nondestructive bending to evaluate the polar distributions of their flexural rigidity, Results from each pair of bones were used to calculate parameters defining the relative mechanical status of the healing bone, These parameters were used to evaluate the effects of p lating system axial flexibility and time on healing, It tvas found tha t: within the selected range of axial flexibility there was an optimal value that produced the best healing; healing progressed with a dimin ishing I ate leading to a steady state; and all four plating systems p roduced healing superior to that obtained with dynamic compression pla tes.