Biomechanical comparison of seven internal fixation devices for the lumbosacral junction.

For comparison purposes, seven different internal fixation systems were applied sequentially to each of six fresh-frozen cadaver spines at the lumbosacral junction. The spines were loaded to a maximum flexion bending moment of 12 Newton meters and an extension moment of 6 Nm. Resultant angular motion was recorded with an electrogoniometer. The Synthes and Kaneda devices provided the most rigid fixation in flexion and extension testing. The Luque internal fixation system was as effective as the Kaneda and Synthes systems at limiting extension but was slightly less successful at limiting flexion. The Knodt system was effective at limiting extension but less effective in limiting flexion. The interfacet screws were effective at limiting flexion but less effective at limiting extension. Harrington rods to the sacral alae were the least effective system in both directions. Sublaminar wires did little to improve their performance.