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Research
Vertical stiffness is not related to anterior cruciate ligament elongation in professional rugby union players
  1. Benjamin G Serpell1,2,
  2. Jennie M Scarvell1,3,
  3. Mark R Pickering1,4,
  4. Nick B Ball5,
  5. Diana Perriman1,2,3,
  6. John Warmenhoven1,
  7. Paul N Smith1,2
  1. 1Trauma and Orthopaedic Research Unit, Canberra Hospital, Woden, Australian Capital Territory, Australia
  2. 2Medical School, Australian National University, Canberra, Australian Capital Territory, Australia
  3. 3University of Canberra Health Research Institute, Bruce, Australian Capital Territory, Australia
  4. 4School of Information Technology and Electrical Engineering, University of New South Wales, Canberra, Australian Capital Territory, Australia
  5. 5Research Institute for Sport and Exercise, University of Canberra, Bruce, Australian Capital Territory, Australia
  1. Correspondence to Dr Benjamin G Serpell; ben.serpell{at}gmail.com

Abstract

Background Novel research surrounding anterior cruciate ligament (ACL) injury is necessary because ACL injury rates have remained unchanged for several decades. An area of ACL risk mitigation which has not been well researched relates to vertical stiffness. The relationship between increased vertical stiffness and increased ground reaction force suggests that vertical stiffness may be related to ACL injury risk. However, given that increased dynamic knee joint stability has been shown to be associated with vertical stiffness, it is possible that modification of vertical stiffness could help to protect against injury. We aimed to determine whether vertical stiffness is related to measures known to load, or which represent loading of, the ACL.

Methods This was a cross-sectional observational study of 11 professional Australian rugby players. Knee kinematics and ACL elongation were measured from a 4-dimensional model of a hopping task which simulated the change of direction manoeuvre typically observed when non-contact ACL injury occurs. The model was generated from a CT scan of the participant's knee registered frame by frame to fluoroscopy images of the hopping task. Vertical stiffness was calculated from force plate data.

Results There was no association found between vertical stiffness and anterior tibial translation (ATT) or ACL elongation (r=−0.05; p=0.89, and r=−0.07; p=0.83, respectively). ATT was related to ACL elongation (r=0.93; p=0.0001).

Conclusions Vertical stiffness was not associated with ACL loading in this cohort of elite rugby players but a novel method for measuring ACL elongation in vivo was found to have good construct validity.

  • ACL
  • Rugby
  • Injury

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

https://doi.org/10.1136/bmjsem-2016-000150

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    Footnotes

    • Twitter Follow Benjamin Serpell at @benserpell1

    • Contributors MRP, JMS and PNS were instrumental in developing the image registration technology used in this project. JMS, NBB, DP, JW and BGS all spent considerable time collecting data while MRP contributed significantly to the processing of data. Finally, all authors read and approved the final manuscript.

    • Funding Funding was awarded for this project via the External Collaboration Grant from the University of Canberra.

    • Competing interests None declared.

    • Ethics approval Approved by the ACT Health Human Research Ethics Committee (Protocol ETH.4.11.072), and the Australian National University Human Research Ethics Committee (Protocol 2011/396).

    • Provenance and peer review Not commissioned; externally peer reviewed.