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Archives of Orthopaedic and Trauma Surgery

, Volume 137, Issue 5, pp 663–671 | Cite as

A cadaveric biomechanical study comparing the ease of femoral nail insertion: 1.0- vs 1.5-m bow designs

  • Huan Yuan
  • Yves Acklin
  • Peter Varga
  • Boyko Gueorguiev
  • Markus Windolf
  • Devakar Epari
  • Michael Schuetz
  • Beat Schmutz
Trauma Surgery

Abstract

Introduction

Anatomic fit of intramedullary nails was suggested by previous studies to improve significantly when the nail radius of curvature (ROC) is closer to the average femoral anatomy. However, no attempt has been made to investigate the impact of different ROC designs on the nail insertion process. Therefore, this biomechanical study quantitatively compared the ease of insertion between femoral intramedullary nails with a 1.0-m and a 1.5-m bow radius.

Materials and methods

Long TFN-ADVANCED™ (TFNA, 1.0 m ROC) and Proximal Femoral Nail Antirotation nails (PFNA, 1.5 m ROC) were implanted pairwise into seven paired cadaver femora. All bones were reamed 1.5 mm larger than the nail diameter. Using a material testing machine, intramedullary nailing was then performed stepwise with 20-mm steps and a 10-mm/s insertion rate, and force was measured. The nail deformation caused by the insertion was assessed through 3D computer models built from pre- and post-nailing CT scans. The ease of insertion between TFNA and PFNA nails was quantified in terms of insertion force, insertion energy and nail deformation.

Results

There was no significant difference in the peak force generated during nailing between TFNA and PFNA nails (P = 0.731). However, the force measured at the end of insertion (P = 0.002) was significantly smaller in TFNA nails compared to PFNA nails. After implantation, TFNA nails showed significantly smaller deformation when compared to PFNA nails (P = 0.005, both ends aligned). Furthermore, less energy was required to insert TFNA nails; however, the difference was not significant (P = 0.25).

Conclusions

Compared to PFNA nails, a significant decrease in insertion force and nail deformation was found at the end of insertion for TFNA nails. Results suggest that TFNA having a 1.0-m ROC is easier to insert for the set of femora used in this study compared to PFNA with a 1.5-m ROC.

Keywords

Femur Intramedullary nail Nail insertion Biomechanical test Radius of curvature (ROC) Insertion force Nail deformation 

Notes

Acknowledgements

The authors would like to acknowledge and thank Mr. Dieter Wahl from AO Research Institute for his excellent support during the nail insertion test.

Compliance with ethical standards

Funding

None.

Conflict of interest

B. Schmutz has received an industrial scholarship from DePuy Synthes Australia.

Ethical approval

The study was approved by the internal institutional board.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.Institute of Health and Biomedical InnovationQueensland University of TechnologyKelvin GroveAustralia
  2. 2.Biomedical ServicesAO Research Institute DavosDavosSwitzerland

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