Characterization of surgical needles.

The acuity (sharpness) of surgical needle points was assessed by measuring the force required for repeat needle penetrations through a medium-gauge latex sheet glued to a perforated Plexiglas frame. The data on the variation in the applied force with repeat penetrations showed that needles obeyed the general relation: P = A + B.n; where P is the applied penetration force in grams, n is the number of penetrations and A and B are constants. Constant A characterized the needle-point acuity and B the maintenance of acuity. This relationship indicated both needle acuity and acuity maintenance with repeated passes through a reproducible target material. Determining the microhardness of needles provided data on their strength which helped to account for differences in the acuity of apparently similar needles. The tensile strength of the union between suture and needle was determined to evaluate the security of suture attachment.