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Parametric Control of the Stiffness of Lumbar Segments
Author(s) -
Wachowski M. M.,
Mansour M.,
Hawallek T.,
KubeinMeesenburg D.,
Hubert J.,
Nägerl H.
Publication year - 2011
Publication title -
strain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.477
H-Index - 47
eISSN - 1475-1305
pISSN - 0039-2103
DOI - 10.1111/j.1475-1305.2009.00686.x
Subject(s) - stiffness , kinematics , anatomy , lumbar , position (finance) , rotation (mathematics) , differential (mechanical device) , physics , mathematics , geometry , structural engineering , medicine , engineering , classical mechanics , finance , economics , thermodynamics
To clarify relations between kinematics and mechanics of lumbar spinal segments (L3/L4, L4/L5) versus thoracic T6/T7. Measurements of rotational angle–torque characteristics and migrations of the instantaneous helical axis (IHA) in cyclic segment motions; correlation of IHA‐position and differential segment stiffness by applying theorem of Steiner. In neutral axial position of the thoracic segment (α = 0), IHA was found within central areas of the intervertebral disc. No change of axial IHA‐positions by flexion/extension. In axial rotation IHA‐migrations along wide arches from one joint to the other and S‐shaped characteristics: strong dependence of IHA‐migration and the differential stiffness on the degree of flexion/extension. In flexion/extension, J‐shape of the characteristic and simultaneous anterior/posterior IHA‐migration. Correlation of initial differential segment stiffness and IHA‐position via theorem of Steiner. The following conclusions are obtained: 1. Non‐linearity of the characteristics is hardly produced by the soft tissues but mainly by IHA‐migration and IHA‐tilting. 2. The segment stiffness in axial rotation is parametrically controlled via the degree of additional flexion/extension. 3. The autochthon muscles are able to control the segment stiffness in axial rotation via shifting the resulting force line in anterior/posterior direction without change of its amount about the factor 3–5.