Traditional experimental methods are unable to study the kinematics of whole lumbar spine specimens under physiologic compressive preloads because the spine without active musculature buckles under just 120 N of vertical load. However, the lumbar spine can support a compressive load of physiologic magnitude (up to 1200 N) without collapsing if the load is applied along a follower load path. This study tested the hypothesis that the load–displacement response of the lumbar spine in flexion–extension is affected by the magnitude of the follower preload and the follower preload path. Twenty‐one fresh human cadaveric lumbar spines were tested in flexion–extension under increasing compressive follower preload applied along two distinctly different optimized preload paths. The first (neutral) preload path was considered optimum if the specimen underwent the least angular change in its lordosis when the full range of preload (0–1200 N) was applied in its neutral posture. The second (flexed) preload path was optimized for an intermediate specimen posture between neutral and full flexion. A twofold increase in flexion stiffness occurred around the neutral posture as the preload was increased from 0 to 1200 N. The preload magnitude (400 N and larger) significantly affected the range of motion (ROM), with a 25% decrease at 1200 N preload applied along the neutral path. When the preload was applied along a path optimized for an intermediate forward‐flexed posture, only a 15% decrease in ROM occurred at 1200 N. The results demonstrate that whole lumbar spine specimens can be subjected to compressive follower preloads of in vivo magnitudes while allowing physiologic mobility under flexion–extension moments. The optimized follower preload provides a method to simulate the resultant vector of the muscles that allow the spine to support physiologic compressive loads induced during flexion–extension activities. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.

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1. Spores of the Bacillus welchii group of bacteria were found on 100 per cent of the uniforms of Belgian soldiers who had come directly from the trenches, and in the meshes of all the samples examined of the new cloth from which the uniforms were made. 2. In fifteen out of twenty fresh war wounds members of this group of bacteria were found. Of the fifteen patients, only three later developed gas gangrene. Once the spores of Bacillus welchii have been carried into a wound the deep-lying lacerated muscle tissue appears to be the most important factor in the onset of gas gangrene. 3. Bacillus welchii is able to grow and produce gas in broth containing up to 40 per cent saccharose. Some strains were able to multiply and produce gas in 50 per cent saccharose broth; but none of those examined were able to grow when the concentration of the sugar reached 60 per cent. 4. The bubbling of pure oxygen through milk or dextrose broth cultures of Bacillus welchii has a definite depressor action on the production of gas. This does not appear to be-due to a reduced number of organisms in the culture.

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