Effect of sternal wire twisting on sternotomy closure rigidity

Abstract

Introduction: Wire twisting is the commonest method of median sternotomy closure. However, wire twisting weakens the wire and fracture may occur at the base of the twisted portion. We investigated how wire twisting affects the physical characteristics of sternotomy closure since rigid fixation promotes quicker primary bone healing.

Methodology: The maximum strength and rigidity of wire closure were tested in a steel sternal model, with varying number of twists, ranging from none to ten twists. Pearson correlation coefficient was used to investigate the relationship between the number of twists versus the maximum closure strength and rigidity. Regression analysis was used to relate closure rigidity with test load and number of wire twists.

Results: Maximum rigidity occurred at two-twists, and decreased from three to ten-twists. Pearson correlation coefficient showed a strong relationship between the number of twists versus maximum closure strength (r = 0.833, p = 0.003) and rigidity (r = 0.819, p = 0.004). The regression model identified load (p < 0.001) and number of twists as significant (p < 0.001), explaining 88.9% of the total variance in displacement. The maximum strength of all twisted closures far exceeded the threshold for wire cutting through bone; suggesting that maximum closure strength is clinically not an important parameter as closure rigidity.

Conclusions: In order to maximize rigidity in the wound closure and optimize primary bone healing, the optimal number of wire twists should be kept low. Excessive number of twists should be avoided as this weakens the closure and increases the amount of foreign material in the wound, theoretically increasing the risk of wound sepsis.