The influence of screw omission on construction stiffness and bone surface strain in the application of bone plates to cadaveric bone.

Biological fracture repair is becoming an increasingly popular means of fracture fixation. This technique involves a reduction in the amount of surgical trauma thereby preserving vascular supply and soft-tissue integrity combined with the implantation of less hardware. The aim is the stimulation of callus formation as the means by which fracture union occurs. This paper describes the mechanical effect of the symmetrical omission of screws on construction stiffness and bone surface strain following the application of bone plates to cadaveric bone. The influence of the pattern of screw omission was evaluated in both intact and osteotomized bone specimens. The application of bone plates using certain patterns of screw omission did not significantly effect the stiffness of the final construction whilst inherent bone surface strain was increased. It was concluded that the omission of screws in certain defined patterns for a given plate-bone construction may meet the criteria for 'biological fixation'. There was no apparent deleterious effect on structural stiffness following the omission of 40% of the total screw complement from a plate-bone construction.