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Microanatomical Nerve Architecture of 6 Mammalian Species: Is Trans-Species Translational Anatomic Extrapolation Valid?
  1. Anna Server, MD*,,
  2. Miguel A. Reina, MD, PhD,§,
  3. André P. Boezaart, MD, PhD,
  4. Alberto Prats-Galino, MD, PhD**,
  5. Marielle Esteves Coelho, MVD, PhD†† and
  6. Xavier Sala-Blanch, MD‡‡,§§
  1. *Department of Anesthesiology, Hospital Universitari Vall d'Hebron
  2. School of Medicine. Universitat de Barcelona, Barcelona
  3. School of Medicine, CEU San Pablo University, and
  4. §Department of Anesthesiology, Madrid-Montepríncipe University Hospital, Madrid, Spain
  5. Departments of Anesthesiology and Orthopaedics and Rehabilitation, University of Florida College of Medicine, Gainesville, FL
  6. **Laboratory of Surgical NeuroAnatomy, Human Anatomy and Embryology Unit, Faculty of Medicine, Universitat de Barcelona
  7. ††Experimental Surgery Unit, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona
  8. ‡‡Human Anatomy and Embryology Unit, Faculty of Medicine, Universitat de Barcelona, and
  9. §§Department of Anesthesiology, Hospital Clinic, Barcelona, Spain
  1. Address correspondence to: André P. Boezaart, MD, PhD, Division of Acute and Perioperative Pain Medicine, Departments of Anesthesiology and Orthopaedic Surgery and Rehabilitation, University of Florida College of Medicine, 1600 SW Archer Rd, PO Box 100254, Gainesville, FL 32610 (e-mail: aboezaart{at}


Background and Objectives Various animal models have historically been used to study iatrogenic nerve injury during performance of conduction nerve blocks. Our aims were to compare the microstructures of nerves in commonly used species to those of humans and to explore the validity of the extrapolating these findings to humans.

Methods High-resolution, light-microscopic images were obtained from cross sections of sciatic nerves at their bifurcation from fresh rat, rabbit, pig, sheep, dog, and human cadavers. Various microanatomical characteristics were measured and compared between the species. P < 0.0033 indicated significant differences.

Results Forty-four samples were studied. There were some interspecies similarities, but the majority of the microanatomical measurements of all 5 species differed significantly from those of humans. Exceptions were rat fascicle cross-sectional area (P = 0.367) and fascicle circumference (P = 0.396); ratio of dog, pig, and sheep fascicle area to total nerve area (dog: P = 0.350; pig: P = 0.958; sheep: P = 0.052); and number of fascicles (pig: P = 0.454; sheep P = 0.077).

Conclusions Although some of the metrics could reasonably be expected to differ because of the size of the species—for example, nerve cross-sectional area—there was little microanatomical similarity between the sciatic nerves of humans and those of the nonprimate mammalian species studied. This may question the validity of some conclusions reached over the years by direct translation from these species to humans. Further studies on nerve function, intraneural injection, and microanatomy of nonhuman primate species are warranted.

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  • The authors declare no conflict of interest.

    This study served as a project for the Master in Advanced Medical Competences in Regional Anesthesia Based on Anatomy, School of Medicine, University of Barcelona, Barcelona, Spain, for A.S.

    The authors received internal funding from the Faculty of Medicine, Universitat de Barcelona, Barcelona, Spain; the Vall d'Hebron Research Institute, Barcelona, Spain; School of Medicine, University of CEU San Pablo, Madrid, Spain; and Department of Anesthesiology, University of Florida College of Medicine, Gainesville, FL, for this article.