Article Text

Download PDFPDF
Variations in Epidural Catheter Manufacture: Implications for Bending and Stiffness
  1. David M. Eckmann, Ph.D., M.D.
  1. From the Department of Anesthesia, University of Pennsylvania Health System, Philadelphia, Pennsylvania and Institute of Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania.
  1. Reprint requests: David M. Eckmann, Ph.D., M.D., Department of Anesthesia, The University of Pennsylvania, 3400 Spruce Str, Philadelphia, PA 19104. E-mail: eckmanndm{at}


Background and Objectives There is no formal evaluation method used to relate epidural catheter design and manufacture to clinical outcomes, such as subarachnoid or intravascular catheter placement. We analyzed catheter bending stiffness to determine the range of stiffness of catheters commonly used. We hypothesized that catheter material has a greater influence on stiffness than does cross-sectional shape.

Methods We determined the elastic modulus by axial load testing and the area moment of inertia using calibrated microscopic measurements of cross-sectional geometry for 6 different catheter types, including 2 types of wire styletted catheters. We calculated bending stiffness as the product of the elastic modulus and the area moment of inertia.

Results Catheters had similar area moments of inertia, but markedly different elastic moduli. Nylon and polyurethane catheters had the same bending stiffness, which was twice as high as that of coil reinforced catheters (P < .05), but 35% lower than that of radiopaque catheters (P < .05). Nylon and radiopaque wire styletted catheters had similar bending stiffness, which were 23-fold to 90-fold greater than that of the nonstyletted catheters (P < .05).

Conclusions Catheters currently available establish the range of bending stiffness that should not be exceeded, only optimized to clinical outcome. Clinical studies are needed to correlate the incidence of unintentional intravascular or subarachnoid catheter placement or migration and bending stiffness. Catheter technology improvements may enhance safety and increase the likelihood of successful catheter insertion, maintenance, and removal. Reg Anesth Pain Med 2003;28:37-42.

  • Bending stiffness
  • Catheter: Epidural
  • Mechanics: Buckling
  • Modulus of elasticity

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • This work should be attributed to the University of Pennsylvania Department of Anesthesia.