Euler's theorem is a proven proposition that is used to predict when a loaded long column will collapse. The N is a constant that describes the column's end condition. The end condition of the suture is free and results in an N constant equal to 1. E is the modulus of elasticity of the column material or in this case the suture material. I is the section moment of inertia of the column or in this example proportional to the suture diameter raised to the 4th power.
L is the unsupported free length of a column.
This is similar to the free length of suture from the exit port of the delivery jaws until it is supported once again in the receiving jaws. The critical load derived from Euler's theorem is calculated for various suture materials to determine which materials will not collapse while penetrating tissue. The theorem is then proven in practice through actual use of the suture materials.