Clinical biomechanics
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Clinical biomechanics · Oct 2011
Biomechanical evaluation of different offset versions of a cementless hip prosthesis by 3-dimensional measurement of micromotions.
Cementless hip prostheses with different offsets are frequently used to restore the rotation center of the hip. However, a rising offset is theoretically associated with a potential risk for increased interface stresses and early loosening. ⋯ According to the measured micromotions no offset version of the CLS Spotorno can be declared as superior. The assumption that the varus version is characterized by extended interface stresses could not be confirmed. Furthermore, it could be demonstrated that according to the principle of proximal load transfer of the CLS Spotorno stem an osseous integration of the distal part cannot be expected and that the risk for stress shielding appears to be relatively low.
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Clinical biomechanics · Jul 2011
Biomechanical effects of insertion location and bone cement augmentation on the anchoring strength of iliac screw.
Iliac screw loosening has been a clinical problem in the lumbo-pelvic reconstruction. Although iliac screws are commonly inserted into either upper or lower iliac column, the biomechanical effects of the two fixations and their revision techniques with bone cement remain undetermined. The purpose of this study was to compare the anchoring strengths of the upper and lower iliac screws with and without cement augmentation. ⋯ The lower iliac screw technique should be the preferred choice in lumbo-pelvic stabilization surgery; cement augmentation may serve as a useful salvage technique for iliac screw loosening; preoperative evaluation of bone quality is crucial for predicting fixation strength of iliac screw.
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Clinical biomechanics · Jun 2011
The comminuted midshaft clavicle fracture: a biomechanical evaluation of plating methods.
The optimal plate location and fixation method for midshaft fractures of the clavicle remains undetermined. The objective of this study was to develop a realistic biomechanical model with which to compare superior with inferior-medial plate placement, and the failure resistance of locked and against non-locked constructs. ⋯ Operative fixation of midshaft clavicle fractures is controversial, though becoming more widely accepted. Few biomechanical data are available to assist surgical decision-making. Inferior plates may be better equipped to resist the in vivo loads experienced by the clavicle during early rehabilitation after internal fixation, particularly during the shoulder flexion motions associated with eating.
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Clinical biomechanics · May 2011
Should extramedullary fixations for hip fractures be removed after bone union?
Osteosynthesis implants, which remain in the patient after fracture union to save additional surgery, may affect the strain distribution within the bone. A reduction of strain within the bone is known to result in localized bone loss ("stress shielding") and increased fracture risk. The purpose of this study was to examine whether extramedullary fixations for femoral neck fractures have to be removed after fracture union to prevent reductions in cortex strains. ⋯ Removal of osteosynthesis implants after bone union reverts bone strains to pre-fracture levels, and might prevent further bone loss induced by stress shielding.
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Clinical biomechanics · May 2011
Diurnal variation in stature: do those with chronic low-back pain differ from asymptomatic controls?
Stature loss is a commonly used measure of spinal load. The aim of this study was to investigate the pattern of diurnal stature change in those with and without chronic low-back pain, over a 24-h period. ⋯ No significant difference existed between groups in relation to total stature loss; however the low-back pain group appeared to reach their nadir earlier, possibly exposing other spinal structures to loading for a greater duration. This is supported by the relationship found between stature loss and discomfort. The reversal in stature loss in the afternoon may be of clinical significance and warrants further investigation.