Al. Osvalder et al., A METHOD FOR STUDYING THE BIOMECHANICAL LOAD RESPONSE OF THE (IN-VITRO) LUMBAR SPINE UNDER DYNAMIC FLEXION SHEAR LOADS, Journal of biomechanics, 26(10), 1993, pp. 1227-1236
A method was developed to study the biomechanical response of the lumb
ar motion segment (Functional Spinal Unit, FSU) under a dynamic (trans
ient) load in flexion. In order to inflict flexion-distraction types o
f injuries (lap seat-belt injuries) different load pulses were transfe
rred to the specimen by means of a padded pendulum. The load response
of the specimen was measured with a force and moment transducer. The f
lexion angulation and displacements were determined by means of high-s
peed photography. Two series of tests were made with ten specimens in
each and with two different load pulses: one moderate load pulse (peak
acceleration 5 g, rise time 30 ms, duration 150 ms) and one severe lo
ad pulse (peak acceleration 12 g, rise time 15 ms, duration 250 ms). T
he results showed that the moderate load pulse caused residual permane
nt deformations at a mean bending moment of 140 Nm and a mean shear fo
rce of 430 N at a mean flexion angulation of 14-degrees. The severe lo
ad pulse caused evident signs of failure of the segments at a mean ben
ding moment of 185 Nm and a mean shear force of 600 N at a mean flexio
n angulation of 19-degrees. Significant correlations were found betwee
n the load response and the size of the specimen, as well as between t
he load response and the bone mineral content (BMC) in the two adjacen
t vertebrae. Comparisons with lumbar spine response to static flexion-
shear loading indicated that the specimens could withstand higher bend
ing moments before injury occurred during dynamic loading, but the def
ormations at injury tended to be smaller for dynamic loading.