Mechanical testing of a flexible fixation device for the lumbar spine

J C Leahy, K J Mathias, D W L Hukins, D E T Shepherd, Wiliam F Deans

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The aim of this study was to test mechanically a new flexible fixation system for the lumbar spine. This device incorporates loops of polyester braid which are secured by a crimped titanium sleeve. In tensile tests, all loops failed, by slippage through the crimped sleeve, at 434 +/- 25 N (mean +/- standard deviation from five loops) for a single crimp and 415 +/- 15 N (from five loops) for two crimps. The intact system was then tested according to the ASTM standard. In a static test, all five specimens failed by slippage of the braid through the sleeve. Initial slippage occurred between 600 and 700 N, but the mean maximum load sustained was 1090 +/- 140 N. Dynamic tests were performed on ten constructs at a frequency of 5 Hz, under a range of loading conditions. The maximum load applied in any of the tests was 825 N. Two constructs did not complete the required 5 x 10(6) test cycles because of fracture of their spinous process hooks. However, other tests, under the same conditions, showed no signs of failure. Fracture occurred as a result of fretting damage from the recommended stainless steel roll pins.

Original languageEnglish
Pages (from-to)489-495
Number of pages7
JournalProceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine
Volume214
Publication statusPublished - 2000

Keywords

  • spine
  • flexible stabilization
  • mechanical testing

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