gms | German Medical Science

14th Triennial Congress of the International Federation of Societies for Surgery of the Hand (IFSSH), 11th Triennial Congress of the International Federation of Societies for Hand Therapy (IFSHT)

17.06. - 21.06.2019, Berlin

The Effect of Torsional Moment of Forearm Weight on the Posterolateral Rotatory Instability of a Lateral Ligament Deficient Elbow: An In Vitro Biomechanical Investigation

Meeting Abstract

  • presenting/speaker Armin Badre - Roth-McFarlane Hand & Upper Limb Centre, St. Joseph's Health Care, London, Canada
  • David Axford - Roth-McFarlane Hand & Upper Limb Centre, St. Joseph's Health Care, London, Canada
  • Sara Banayan - Roth-McFarlane Hand & Upper Limb Centre, St. Joseph's Health Care, London, Canada
  • Jim Johnson - Roth-McFarlane Hand & Upper Limb Centre, St. Joseph's Health Care, London, Canada
  • Graham King - Roth-McFarlane Hand & Upper Limb Centre, St. Joseph's Health Care, London, Canada

International Federation of Societies for Surgery of the Hand. International Federation of Societies for Hand Therapy. 14th Triennial Congress of the International Federation of Societies for Surgery of the Hand (IFSSH), 11th Triennial Congress of the International Federation of Societies for Hand Therapy (IFSHT), 11th Triennial Congress of the International Federation of Societies for Hand Therapy (IFSHT). Berlin, 17.-21.06.2019. Düsseldorf: German Medical Science GMS Publishing House; 2020. DocIFSSH19-367

doi: 10.3205/19ifssh1432, urn:nbn:de:0183-19ifssh14326

Published: February 6, 2020

© 2020 Badre et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.


Outline

Text

Objectives/Interrogation: Previous biomechanical studies of LCL injuries and their surgical repair, reconstruction and rehabilitation have primarily relied on gravity effects with the arm in the varus position. The application of torsional moments to the forearm manually is not reproducible; hence studies to date likely do not represent forces encountered clinically.

The aim of this investigation was to develop a new biomechanical model to quantify posterolateral stability of the elbow.

Methods: Six cadaveric arms were mounted in an elbow motion simulator in the varus position. A threaded screw was inserted on the dorsal aspect of the proximal ulna and a weight hanger was used to suspend 400g, 600g, and 800g of weight from the screw head to allow torsional moments to be applied to the ulna. An LCL injured (LCLI) model was created by sectioning of the common extensor origin, and the LCL.

Ulnohumeral rotation was recorded using an electromagnetic tracking system during simulated active and passive elbow flexion with the forearm pronated and supinated.

Results and Conclusions: During active motion with the forearm pronated, the addition of weights did not significantly increase the external rotation (ER) of ulnohumeral articulation (10.0±7.0°,P=.268 400g;10.5±7.1°,P=.156 600g;11.0±7.2°,P=.111 800g) compared to the LCLI (8.4±6.4°). However, with the forearm supinated, the addition of 800g but not 400g and 600g significantly increased the ER (8.2±5.7°,P=.083 400g;8.7±5.9°,P=.054 600g; 9.2±5.9°,P=.038 800g) compared to the LCLI (5.9±5.5°).

During passive motion with the forearm pronated, the addition of 600g and 800g but not 400g resulted in a significant increase in ER (9.3±7.8°,P=.103 400g;11.2±6.2°,P=.004 600g;12.7±6.8°,P=.006 800g) compared to the LCLI (3.7±5.4°). With the forearm supinated, the addition of 400g, 600g, and 800g significantly increased the ER (11.7±6.7°,P=.031 400g;13.5±6.8°,P=.019 600g;14.9±6.9°,P=.024 800g) compared to the LCLI (4.3±6.6°).

This novel biomechanical model demonstrates that the application of even small amounts of torsional moment on the forearm with the arm in the varus position exacerbates the rotational instability seen with the LCL deficient elbow. This new model allows for a more provocative testing of elbow stability after LCL repair or reconstruction, allowing smaller sample sizes to be used while still demonstrating clinically significant differences. Future biomechanical studies evaluating LCL injuries, repair and rehabilitation should consider using this testing protocol.