Lumbar spinal loads vary with body height and weight.
ABSTRACT Knowledge about spinal loading is required for designing and preclinical testing of spinal implants. It is assumed that loading of the spine depends upon body weight and height, as well as on the spine level, but a direct measurement of the loading conditions throughout the spine is not yet possible. Here, computer models can allow an estimation of the forces and moments acting in the spine. The objective of the present study was to calculate spinal loads for different postures and activities at several levels of the thoracolumbar spine for various combinations of body height and weight. A validated musculoskeletal model, together with commercially available software (AnyBody Technology), were used to calculate the segmental loads acting on the centre of the upper endplate of the vertebrae T12 to L5. The body height was varied between 150 and 200cm and the weight between 50 and 120kg. The loads were determined for five standard static postures and three lifting tasks. The resultant forces and moments increased approximately linearly with increasing body weight. The body height had a nearly linear effect on the spinal loads, but in almost all loading cases, the effect on spinal loads was stronger for variation of body weight than of body height. Spinal loads generally increased from cranial to caudal. The presented data now allow the estimation of the spinal load during activities of daily living on a subject specific basis, if body height and weight are known.
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ABSTRACT: After spinal surgery, physiotherapeutic exercises are performed to achieve a rapid return to normal life. One important aim of treatment is to regain muscle strength, but it is known that muscle forces increase the spinal loads to potentially hazardous levels. It has not yet been clarified which exercises cause high spinal forces and thus endanger the surgical outcome. The loads on vertebral body replacements were measured in 5 patients during eleven physiotherapeutic exercises, performed in the supine, prone, or lateral position or on all fours (kneeling on the hands and knees). Low resultant forces on the vertebral body replacement were measured for the following exercises: lifting one straight leg in the supine position, abduction of the leg in the lateral position, outstretching one leg in the all-fours position, and hollowing the back in the all-fours position. From the biomechanical point of view, these exercises can be performed shortly after surgery. Implant forces similar or even greater than those for walking were measured during: lifting both legs, lifting the pelvis in the supine position, outstretching one arm with or without simultaneously outstretching the contralateral leg in the all-fours position, and arching the back in the all-fours position. These exercises should not be performed shortly after spine surgery.PLoS ONE 01/2014; 9(7):e102005. · 3.53 Impact Factor
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ABSTRACT: Knowledge of in vivo human lumbar loading is critical for understanding the lumbar function and for improving surgical treatments of lumbar pathology. Although numerous experimental measurements and computational simulations have been reported, non-invasive determination of in vivo spinal disc loads is still a challenge in biomedical engineering. The object of the study is to investigate the in vivo human lumbar disc loads using a subject-specific and kinematic driven finite element approach. Three dimensional lumbar spine models of three living subjects were created using MR images. Finite element model of the L3-4 disc was built for each subject. The endplate kinematics of the L3-4 segment of each subject during a dynamic weight lifting extension was determined using a dual fluoroscopic imaging technique. The endplate kinematics was used as displacement boundary conditions to calculate the in-vivo disc forces and moments during the weight lifting activity. During the weight lifting extension, the L3-4 disc experienced maximum shear load of about 230N or 0.34 bodyweight at the flexion position and maximum compressive load of 1500N or 2.28 bodyweight at the upright position. The disc experienced a primary flexion-extension moment during the motion which reached a maximum of 4.2Nm at upright position with stretched arms holding the weight. This study provided quantitative data on in vivo disc loading that could help understand intrinsic biomechanics of the spine and improve surgical treatment of pathological discs using fusion or arthroplasty techniques.Clinical biomechanics (Bristol, Avon) 12/2013; · 1.76 Impact Factor
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ABSTRACT: Activities with high spinal loads should be avoided by patients with back problems. Awareness about these activities and knowledge of the associated loads are important for the proper design and pre-clinical testing of spinal implants. The loads on an instrumented vertebral body replacement have been telemetrically measured for approximately 1000 combinations of activities and parameters in 5 patients over a period up to 65 months postoperatively. A database containing, among others, extreme values for load components in more than 13,500 datasets was searched for 10 activities that cause the highest resultant force, bending moment, torsional moment, or shear force in an anatomical direction. The following activities caused high resultant forces: lifting a weight from the ground, forward elevation of straight arms with a weight in hands, moving a weight laterally in front of the body with hanging arms, changing the body position, staircase walking, tying shoes, and upper body flexion. All activities have in common that the center of mass of the upper body was moved anteriorly. Forces up to 1650 N were measured for these activities of daily life. However, there was a large intra- and inter-individual variation in the implant loads for the various activities depending on how exercises were performed. Measured shear forces were usually higher in the posterior direction than in the anterior direction. Activities with high resultant forces usually caused high values of other load components.PLoS ONE 01/2014; 9(5):e98510. · 3.53 Impact Factor