An understanding of the remodelling of tendon is crucial for the development of scientific methods of treatment and rehabilitation. This study tested the hypothesis that tendon adapts structurally in response to changes in functional loading. A novel model allowed manipulation of the mechanical environment of the patellar tendon in the presence of normal joint movement via the application of an adjustable external fixator mechanism between the patella and the tibia in sheep, while avoiding exposure of the patellar tendon itself. Stress shielding caused a significant reduction in the structural and material properties of stiffness (79%), ultimate load (69%), energy absorbed (61%), elastic modulus (76%) and ultimate stress (72%) of the tendon compared with controls. Compared with the material properties the structural properties exhibited better recovery after re-stressing with stiffness 97%, ultimate load 92%, energy absorbed 96%, elastic modulus 79% and ultimate stress 80%. The cross-sectional area of the re-stressed tendons was significantly greater than that of stress-shielded tendons. The remodelling phenomena exhibited in this study are consistent with a putative feedback mechanism under strain control. This study provides a basis from which to explore the interactions of tendon remodelling and mechanical environment.
"or back pain are strongly related to moderately increased spinal loading arising from body weight ( Videman et al . , 2010 ) , occupation ( Videman et al . , 2006 ) , or leisure activities ( Videman et al . , 2007 ) , presumably because all skeletal tissues even - tually adapt to moderate and habitual levels of loading ( Skrzypiec et al . , 2007 ; Rumian et al . , 2009 ; Sugiyama et al . , 2012 ) . Cyclic loading of animal ten - dons causes deterioration if the loading is severe , and adaptation if it is moderate . ( Andarawis - Puri et al . , 2012 ) . In the words of Nietzsche : " What does not kill me makes me stronger ! ""
[Show abstract][Hide abstract] ABSTRACT: We designed and validated a novel knee joint fixation/distraction system to study tendon-to-bone healing in an in vivo rat model of anterior cruciate ligament (ACL) reconstruction. The system uses an external fixator to apply a cyclic distraction of the knee joint while monitoring the resultant force developed across the joint, thus providing a temporal indication of structural changes during the healing process of the bone-tendon-bone reconstruction. The validation was performed using an optical kinematic tracking system to determine the local displacement of the knee. The average system compliance was determined to be 42.4 +/- 8.8 mum/N with a coefficient of variation of 20.7%. The compliance was used to obtain a best fit correction factor which brought the total root mean square error of knee joint distraction to within 179 mum (16.1%) of the applied distraction. We performed a pilot study using 15 rats that had ACL reconstructions using a flexor digitorum longus tendon autograft and found that the animals tolerated the indwelling fixator and daily anesthesia over a 10 day loading protocol. Our knee joint fixation/distraction system provides a valuable tool to study how mechanical stimuli affect in vivo bone-tendon-bone healing.
Journal of Medical Devices 03/2010; 4(1):15003. DOI:10.1115/1.4001158 · 0.42 Impact Factor
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