Preliminary evaluation of the Sternum Screw: a novel method for improved sternal closure to prevent dehiscence

Sternal dehiscence is a relatively rare but serious complication of sternal closure with an unacceptable mortality and morbidity rate. The 6 mm cannulated Sternum Screws are a novel approach that aims to prevent dehiscence. The screws are placed on either side of the sternotomy and wire threaded through the cannula and closed customarily. The Sternum Screws make the bone non-penetrable at the same time retaining the familiarity of conventional stainless steel wire. This novel technique was tested in sheep sterna to compare its efficacy to conventional wire closure. Using tensile testing in a testing machine, randomised controlled closures of the Sternum Screws and No. 5 stainless steel wires were evaluated until system failure. Seventeen matched pairs were tested. The Sternum Screw closure was on average 36% stronger, 284+/-43 N (mean+/-SD) compared to conventional wire closure alone, 215+/-38 N (mean+/-SD) [p<0.0001 by t-test]. System failure in 82% of Sternum Screw closures, however, was due to wire breakage or untwisting rather than the screw itself. In all these cases the screw remained intact in bone. 71% of conventional wire closures failed by dehiscing through the sterna. The mean forces required for wire dehiscence and wire failure in the Sternum Screws may be achieved in vivo during large coughs. The study shows there is merit in further evaluating the approach as a method of preventing dehiscence. It also highlights the use of alternative wiring techniques increase the tensile strength of the closure yet retain the familiarity and versatility of conventional wire.