Load Distribution in the Lumbar Spine During Modeled Compression Depends on Lordosis

Abstract

Excessive or incorrect loading of lumbar spinal structures is commonly assumed as one of the factors to accelerate degenerative processes, which may lead to lower back pain. Accordingly, the mechanics of the spine under medical conditions, such as scoliosis or spondylolisthesis, is well-investigated. Treatments via both conventional therapy and surgical methods alike aim at restoring a “healthy” (or at least pain-free) load distribution. Yet, surprisingly little is known about the inter-subject variability of load bearings within a “healthy” lumbar spine. Hence, we utilized computer tomography data from 28 trauma-room patients, whose lumbar spines showed no visible sign of degeneration, to construct simplified multi-body simulation models. The subject-specific geometries, measured by the corresponding lumbar lordosis (LL) between the endplates of vertebra L1 and the sacrum, served as ceteris paribus condition in a standardized forward dynamic compression procedure. Further, the influence of stimulating muscles from the M. multifidus group was assessed. For the range of available LL from 28 to 66°, changes in compressive and shear forces, bending moments, as well as facet joint forces between adjacent vertebrae were calculated. While compressive forces tended to decrease with increasing LL, facet forces were tendentiously increasing. Shear forces decreased between more cranial vertebrae and increased between more caudal ones, while bending moments remained constant. Our results suggest that there exist significant, LL-dependent variations in the loading of “healthy” spinal structures, which should be considered when striving for individually appropriate therapeutic measures.

Spielt es eine Rolle, ob das ISG als Schmerzquelle diagnostiziert wird?

“…B. je nach Rumpf-Flexionsmuster. Wird der Rumpf mit verringerter LWS-Lordose flektiert (lumbales Flexionsmuster), wirken höhere Scherkräfte ein, während eine Vorwärtsbeuge bei normaler oder erhöhter Lordose (Hüftflexionsmuster) die Kompressionskräfte verstärkt 22 23 24 . Damit lässt sich u. a. die Validität einer Subgruppenbildung nach Bewegungskontrollmustern in der LBP-Rehabilitation begründen 25 .…”

“…For example, the forces on the spine vary based on the pattern of trunk flexion. During trunk flexion with a reduced lordosis (i. e., lumbar flexion pattern), there is more shear and with a normal or increased lordosis (i. e., hip flexion pattern) there is more compression 22 23 24 . This is part of the validity of subgrouping movement pattern control in LBP rehabilitation 25 .…”

Augmenting the Cobb angle: Three-dimensional analysis of whole spine shapes using Bézier curves

“…As reported previously [24,33] , computer tomography (CT) data of all spines were obtained from trauma-room patients with otherwise healthy spines (no sign of degeneration), provided anonymized by the University Medical Center in Mainz. The 39 subjects (28 male, 9 female, 2 unknown) were of rather young average age (32 ± 20 years, excluding the two unknown) with a range between 16 and 75 years.…”

“…Both, segmentation and insertion points were subsequently checked by a team of neurosurgeons, cf. [24,33] . Further, assuming constant bone density, the COM of all vertebrae were calculated.…”

“…Regarding the latter, see next Section 4.3 . Regarding the former, prior studies [5,12,24] have shown the significance of spinal shape on the internal load distribution. The main advantage of our method is the approximation of vertebral COM, instead of whole vertebrae, which is applicable on 2D radiographs (see Fig.…”