In Vivo Creep Model of Human Lumbar Spine Segments in Pure Centric Tension

M. Kurutz (Hungary)


Spine biomechanics, traction bath therapy, lumbar FSU model, spring-dashpot model, creep, damping.


The goal of this study was to create a viscoelastic tensile model of human lumbar-lumbosacral motion segments for numerical simulation of traction therapies. The in vivo creep model is based on a large-scale experimental analy sis of elongations of human lumbar segments in pure cen tric tension, when the effect of muscles can be excluded. Time-dependent in vivo elongations of segments L3-L4, L4-L5 and L5-S1 have been measured during the usual 20 minutes long traction hydrotherapy of patients, by using a subaqual ultrasound measuring method documented by Kurutz et al. in [1] and [2]. Elongations of segments were considered as change of the distance between two neighbouring spinous processes. Patients were freely sus pended on cervical support in lukewarm water for 20 minutes, with fully relaxed muscles. The traction load was constant during the treatment, thus, a creeping process developed and could be dicumented numerically. The creep proceff has been measured in the gruop of patients with less degenerated segments, loaded by 20-20 N extra weights on ankles. The extra loads were prescribed by medical initiation. Patients with more degenerated seg ments have been excluded from the creep analysis.

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