A continuous pure moment loading apparatus for biomechanical testing of multi-segment spine specimens

An apparatus is described that enables the application of continuous pure m oment loads to multi-segment spine specimens. This loading apparatus allows continuous cycling of the spine between specified flexion and extension (o r right and left lateral bending) maximum load endpoints. Using a six-degre e-of-freedom load cell and three-dimensional optoelectronic stereophotogram metry, characteristic displacement versus load hysteresis curves can be gen erated and analyzed for different spinal constructs of interest. Unlike qua si-static loading, the use of continuous loading permits the analysis of th e spine's behaviour within the neutral zone. This information is of particu lar clinical significance given that the instability of a spinal segment is related to its flexibility within the neutral zone. Representative curves for the porcine lumbar spine in flexion-extension and lateral bending are p resented to illustrate the capabilities of this system. (C) 2000 Elsevier S cience Ltd. All rights reserved.