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Background: Spine boards are used to immobilise accident victims suspected of having spinal injury. Guidelines about the maximum time patients remain on the board are often exceeded and on occasions may lead to pressure ulcers. Etiological research has shown that two processes ultimately lead to pressure ulcers:"Ischemic damage" which takes several hours to initiate and "deformation damage" at high strains. The latter process is very quick and the first signs of cell damage are already evident within minutes. Thus in order to minimise the risk of pressure ulcer development during prolonged loading, a new soft-layered long spine board has been designed., Methods: A subject specific numerical approach has been adopted to evaluate the prototype spine board in comparison to a conventional spine board, with reference to the estimated strains in the soft tissues adjacent to the sacrum in the supine position. The model geometry is derived from magnetic resonance images of three human volunteers in an unloaded situation. The loaded images are used to "tune" the material parameters of skin, fat and muscle. The prediction of the deformed contours on the soft-layered board is used to validate the model., Findings: Comparison of the internal strains in muscle tissue near the spine showed that internal strains on the soft-layered board are reduced and maximum strains are considerably less than the threshold at which deformation damage is possible. By contrast, on the rigid spine board this threshold is exceeded in all cases., Interpretation: The prototype comfort board is able to reduce the risk for deformation damage and thus reduces the risk of developing pressure ulcers., (© 2013.)

Background: It is important to consider lumbar lordotic angle for setup of training program in field of sports and rehabilitation to prevent unexpected posture deviation and back pain. The purpose of this study was to to analyze the biomechanical impact of the level of lumbar lordosis angle during isokinetic exercise through dynamic analysis using a 3-dimensional musculoskeletal model., Methods: Gait analysis and isokinetic exercise for the healthy adults (n=10) were performed to design a 3-dimensional musculoskeletal model and then we made each model for normal lordosis, excessive lordosis, lumbar kyphosis, and hypo-lordosis according to lordotic angle and inputted experimental data as initial values to perform inverse dynamic analysis to quantify muscle joint torque, joint forces of each joint, system energy, and estimated muscle forces at lumbosacral joint., Findings: Comparing the joint torques, the largest torque of excessive lordosis was 16.6% larger than that of normal lordosis, and lumbar kyphosis was 11.7% less than normal lordosis. There existed no significant difference in the compressive intervertebral forces of each lumbar joint (P>0.05), but statistically significant difference in the anterioposterior shear force (lumbar kyphosis>hypo-lordosis>excessive lordosis>normal lordosis, P<0.05). Lastly, lumbar kyphosis required the least and most energy during flexion and extension respectively., Interpretation: During the rehabilitation process, more efficient training will be possible by taking into consideration not simply weight and height but biomechanical effects on the skeletal muscle system according to lumbar lordortic angles., (Copyright (c) 2010 Elsevier Ltd. All rights reserved.)

Clinical studies have recently documented that there is sufficient evidence to suggest that abnormal motion may be an indicator of abnormal mechanics of the spine and, therefore, may be associated with some types of low-back pain. However, designating a motion as abnormal requires knowledge of normal motions. This work hence aims to develop an accurate computational model to simulate the bio-mechanical response of the whole lumbosacral spinal unit (L1-S1) under physiological loadings and constraint conditions. In order to meet this objective, computed tomography (CT) scanning protocols, finite element (FE) analysis and accurate constitutive modelling have been integrated. Then the ranges of motion (ROM) under flexion, extension and lateral bending moment were measured and compared with experimental data, finding an excellent agreement. In particular, the ability of the model to reproduce the relative rotation between each couple of vertebrae was proved. Finally, the shear stresses for the most extreme load cases were reported in order to predict which are the most risky conditions and where the maximum damage would be located. The results indicate that the greater values of the stresses were located at L4-S1 levels just in the interfaces between disc and vertebrae across the posterior and posterolateral zone. This result can be clinically correlated with the existence of damage exactly where the stresses were maximal in the proposed finite element model., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Objective: Quantification of the maximum anatomical cross-sectional area of the lumbar back muscles as a function of torso flexion angle and development of prediction equations as a function of torso flexion and anthropometric measures., Background: Cross-sectional areas of the lumbar back muscles used as inputs into biomechanical models have traditionally been derived from subjects lying in the neutral supine posture. However, it is known that the cross-sectional area of muscle is altered as the torso angle changes., Design: Experimental design consisted of a two-factor multivariate analysis of variance on the cross-sectional area of the lumbar torso muscle across the lumbar levels, as a function of gender and torso angle. Hierarchical linear regression was utilized to assess the association between cross-sectional area and individual and torso posture characteristics., Method: Axial MRI scans, through and parallel to each of the lumbar intervertebral discs at four torso flexion positions were obtained from subjects in a lateral recumbent posture. Cross-sectional areas were quantified and converted into anatomical cross-sectional areas utilizing known fascicle orientations., Results: The maximum anatomical cross-sectional area was located between the L(3)/L(4) and L(4)/L(5) level in the neutral posture. The anatomical cross-sectional areas at the L(4)/L(5) and L(5)/S(1) decreased during torso flexion, however, the percent change varied as a function of the individual level. The majority of the anatomical cross-sectional area variability was explained by gender and body mass. Lumbar curvature explained a larger proportion of the anatomical cross-sectional area variability at the lower lumbar levels than at the higher lumbar levels., Conclusions: The maximum anatomical cross-sectional area of the lumbar back muscles occur at the neutral torso posture and did not decrease as a function of torso flexion. When using maximum anatomical cross-sectional area or specific lumbar level anatomical cross-sectional areas, it appears necessary to account for gender and body mass. At the lower lumbar levels, knowledge of spinal curvature plays an increasing role in the estimation of the size of the lumbar torso muscle cross-sectional area., Relevance: This research indicates the lower lumbar level trunk muscle anatomical cross-sectional area decrease as torso flexion increases, however, the maximum lumbar trunk muscle anatomical cross-sectional area does not vary as a function of torso flexion. Accounting for gender, body mass, torso characteristics and lumbar curvature may help increase accuracy of anatomical cross-sectional area prediction, as well as muscle force predictions from biomechanical models.

Introduction: We describe a reproducible and less invasive surgical approach to sacral neuromodulation (InterStim Therapy) in the treatment of voiding dysfunction. Twenty patients underwent modified lead implantation (mean operative time 45 minutes) without any difficulties or complications, with a mean follow-up of 8 months (range 1 to 14).Technical Considerations. The highlights of these modifications include (a) fluoroscopy to localize the S3 foramen; (b) paramedian incision; (c) use of a cutoff S3 finder needle and a 14-gauge Angiocath to direct permanent lead into the S3 foramen without dissection; (d) use of lateral fluoroscopy to determine the depth of the Angiocath insertion; and (e) anchoring the lead to the lumbodorsal fascia (superficial to the sacral periosteum) using a moveable lead anchor system. These modifications simplify and minimize the invasiveness of this therapy without compromising the efficacy., Conclusions: Because of the simplicity of these modifications, we are currently using an implanted lead, rather than the temporary percutaneous lead, to assess patients' clinical response before implanting a pulse generator.

To verify that maximization of endurance is important among the functional criteria determining trunk muscle activation patterns, symmetric and asymmetric exertions were simulated using a detailed model consisting of 114 muscle slips crossing the lumbosacral junction and employing a cost function which maximizes endurance. First, the question whether meaningful comparisons can be made between activity predictions for individual muscle slips and surface EMG data recorded from larger anatomical entities was addressed. This was answered affirmatively, since activation patterns predicted by a coarse and a middle version of the model, in which activation was constrained to be equal within 14 or 32 groups of muscle slips, were similar to those predicted with each muscle slip controlled independently. Median correlation coefficients between activity vectors predicted by the simplified models and the detailed model were 0.88 and 0.97, respectively. The coarse model underestimated the endurance capacity by a median of 21%, the middle model by only 0.7%. Second, predicted activities within anatomical entities defined at this level of detail were compared to reference data derived from the literature (Lavender et al. 1992, Human Factors 34, 239-247; 1992, Journal of Orthopaedic Research 10, 691-700; Vink et al., 1988, Electromyography and Clinical Neurophysiology 28, 517-525). The predicted activity patterns of the erector spinae, external oblique and rectus abdominis muscles closely resembled the EMG patterns (r2 = 0.48-0.99). Furthermore, the observed distribution of activity between parts of the erector spinae muscle was adequately predicted.

The factors affecting distribution of anesthetic within the spinal column are of current interest due to recent reports of neurological injury occurring during spinal anesthesia. This paper describes a numerical model for simulating anesthetic dispersion, and applies the model to the evaluation of spinal-column size, anesthetic injection rate, and catheter orientation as factors influencing the anesthetic distribution. The model is based upon the finite-element method and incorporates a three-dimensional geometry derived from images of human spinal columns. Simulation results show that the ratio of the cross-sectional dimension of the subarachnoid space within the spinal column to the diameter of the catheter is a critical parameter, with low values of this ratio producing the most uniform anesthetic distributions. Increasing injection rate is found to produce a less uniform distribution in a global sense (higher total volume of anesthetic in the 'sacral' half) but a more uniform distribution in a localized sense (lower concentrations at critical points). Finally, the anesthetic distribution is demonstrated to be highly sensitive to orientation angle at high injection rates.

The purpose of this study was to use anatomical data obtained from cadavers, and geometrical scaling data obtained from MRI scans of living subjects, to assess the line of action and mechanical function of the psoas major muscle in three dimensions about each lumbar spine level. In addition, the line of action of the psoas major was documented as a function of lordosis. A total of seven cadavers were dissected from which fibre/tendon architecture was measured, while MRI scans were performed on 15 males to obtain centroid paths and area scales of the muscle over its length. In this way, the curving path of muscle line of action was accommodated together with force and moment predictions that recognized the presence of a tendon at lower lumbar levels (up to L3 in some subjects) significantly increasing the stress. Results confirm that the mechanics of the psoas cannot be adequately represented with a series of straight line vectors from vertebral origins to insertion. Moreover, the mechanical action of the psoas major does not change as a function of lumbar spine lordosis as the muscle path of action changes in accordance with changes in spine posture. Functionally, contrary to claims, the psoas cannot act as a 'derotator' of the spine, does not impose large shear forces on the spine in any posture except at L5-S1, and cannot have major affects to 'control lordosis'. It has the potential to stabilize the lumbar spine with compressive loading and with bilateral activation, to laterally flex it, and can create large anterior shear forces but only at L5-S1.

The mechanical loading on the body during the act of lifting has been estimated frequently. The opposite act of lowering has received much less attention. The aim of the present study was to compare the mechanical loading of the musculoskeletal system in lifting and lowering. Eight subjects repetitively lifted and lowered a load, using two different techniques (a leg and a back technique). The ankle, knee, hip and lumbosacral joint moments were estimated and the myoelectrical (EMG) activity of seven (leg and back) muscles was recorded. The differences between the lifting and lowering phase for the leg technique were similar to those observed when the back technique was applied. The joint moment curves in lifting showed a high level of agreement with the (time-reversed) moment curves in lowering. Peak moments in lowering were only slightly lower than in lifting (peak lumbar moments were 5.4% lower). These small differences were related to different acceleration profiles at the centre of gravity of the body/load complex. The EMG activity was considerably lower in lowering than in lifting. The mean EMG in lowering (average for seven muscles) was only about 69% of the EMG in lifting. This was attributed to the different types of muscle actions involved in lifting (mainly concentric) and lowering (mainly eccentric). Furthermore, the EMG results suggest that similar inter-muscular coordination is involved in lowering and lifting. The results give rise to the assumption that in lifting and lowering similar muscle forces are produced to meet the (nearly) equal joint moments, but in lowering these forces are distributed over a smaller cross-sectional area of active muscle, which might imply a higher risk of injury.

The physical and mechanical properties of calf lumbar and sacral trabecular bone were determined and compared with those of human trabecular bone. The mean tissue density (1.66 +/- 0.12 g cm-3), equivalent mineral density (169 +/- 36 mg cm-3), apparent density (453 +/- 89 mg cm-3), ash density (194 +/- 59 mg cm-3), ash content (0.6 +/- 0.05%), compressive strength (7.1 +/- 3.0 MPa) and compressive modulus (173 +/- 97 MPa) of calf trabecular bone are similar to those of young human. There were moderate, positive linear correlations between apparent density and equivalent mineral density, ash density, and compressive strength; and between compressive strength and equivalent mineral density (R2 ranging from 0.35 to 0.48, p less than 0.001). Apparent density, ash density, and equivalent mineral density did not differ significantly in different regions. In contrast to humans, the compressive strength increased from posterior, near the facet, to the anterior vertebral body. These comparisons of physical and mechanical properties, as well as anatomical comparisons by others, indicate that the calf spine is a good model of the young non-osteoporotic human spine and thus useful for the testing of spinal instrumentation.