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DISTRACTION FORCES REQUIRED DURING GROWTH ROD LENGTHENING



Abstract

Background: To quantify the distraction forces required to lengthen a standard subcutaneous domino linked two rod construct. This was a seminal piece of work as part of a project to design a magnetic coil driven micro electromechanical internal device that would mitigate the need for surgical lengthenings of these growth rod constructs.

Methods: A distraction tool with strain gauge was designed and built in the RNOH Department of Biomechanics and following calibration and testing was used to perform five distraction procedures. Subjects were five patients with early onset progressive scoliosis unresponsive to conservative treatment modalities who have previously had a subcutaneous rodding procedure and are hence having regular lengthenings. Forces were transduced and collected on a laptop computer in theatre running a piece of software specifically written for the experiment.

Results: Forces will be displayed in graphical format with correlation with pre- and post-lengthening radiographs.

Conclusion: The magnitude of force required to achieve distraction is compatible with that achievable via a magnetic coil driven internal micro electromechanical device that we are currently in the design phase of producing.

The abstracts were prepared by Mr Colin E. Bruce. Correspondence should be addressed to Colin E. Bruce, Consultant Orthopaedic Surgeon, Alder Hey Children’s Hospital, Eaton Road, Liverpool, L12 2AP.

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