Laparoscopic Trocars: Marketed versus True Dimensions-A Descriptive Study

Abstract

STUDY OBJECTIVE: To establish true dimensions of single-use laparoscopic trocars compared with marketed dimensions, calculate corresponding incision sizes, examine what trocar size categories are based on, and outline accessibility of information regarding true dimensions. DESIGN: Descriptive study. SETTING: Laparoscopic disposable trocars available in North America and Europe are marketed in several distinct categories. In practice, trocars in the same-size category exhibit different functionality (ability to introduce instruments/needles and retrieve specimens) and warrant different incision lengths. PATIENTS: Not applicable. INTERVENTIONS: Not applicable. MEASUREMENTS AND MAIN RESULTS: True dimensions for 125 trocars (bladeless, optical, and balloon) were obtained from 9 vendors covering 8 marketed size categories (3-, 3.5-, 5-, 8-, 10-, 11-, 12-, and 15-mm trocars). On average, true inner cannula diameter was 0.92 mm wider (SD, 0.41 mm; range, 0-2.4 mm) than the marketed size category, with the widest range in the 5 mm category. For 5-mm trocars, mean true inner diameter was 6.1 mm (SD, 0.45; range, 5.5-7.4) and true outer diameter 8.3 mm (SD, 0.71; range, 8.0-10.7). For 12-mm trocars, mean true inner diameter was 13.0 mm (SD, 0.21; range, 12-13.3) and outer diameter 15.3 mm (SD, 0.48; range, 14.4-16.8). Five-mm trocars necessitate a mean incision size of 13.0 mm (SD, 1.1; range, 12.1-16.8) and 12-mm trocars a mean incision of 24.0 mm (SD, 0.75; range, 22.6-26.4). No vendors stated actual diameters on company website or catalog. In one instance the Instructions For Use document contained the true inner diameter. CONCLUSION: Trocar size categories give a false sense of standardization when in actuality there are considerable within-category differences in both inner and outer diameters, corresponding to differences in functionality and required incision sizes. There is no universally applied definition for trocar size categories. Accessibility of information on true dimensions is limited.