Effects of Stress Shielding on the Mechanical Properties of Rabbit Patellar Tendon

1993 ◽  
Vol 115 (1) ◽  
pp. 23-28 ◽  
Author(s):  
N. Yamamoto ◽  
K. Ohno ◽  
K. Hayashi ◽  
H. Kuriyama ◽  
K. Yasuda ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Patellar Tendon ◽  
Steel Wire ◽  
Stress Shielding ◽  
Maximum Load ◽  
Tensile Tests ◽  
Tibial Tubercle ◽  
Cross Sectional ◽  
Knee Ligament ◽  
Control Value

Mechanical properties of the stress-shielded patellar tendon were studied in the rabbit knee. Stress shielding was accomplished by stretching a stainless-steel wire installed between the patella and tibial tubercle and thus, releasing the tension in the patellar tendon completely. Tensile tests were carried out on the specimens obtained from the patellar tendons which were exposed to the stress shielding for 1 to 6 weeks. The stress shielding changed the mechanical properties of the patellar tendon significantly: it decreased the tangent modulus and tensile strength to 9 percent of the control values after 3 weeks. There was a 131 percent increase in the cross-sectional area and a 15 percent decrease in the tendinous length. Remarkable changes were also observed in the structural properties: for example, the maximum load of the bone-tendon complex decreased to 20 percent of the control value after 3 weeks. Histological studies showed that the stress shielding increased the number of fibroblasts and decreased the longitudinally aligned collagen bundles. These results imply that if no stress is applied to the autograft in the case of augmentative reconstruction of the knee ligament, the graft strength decreases remarkably.

scholarly journals Experimental Investigation into Corrosion Effect on Mechanical Properties of High Strength Steel Bars under Dynamic Loadings

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Hui Chen ◽  
Jinjin Zhang ◽  
Jin Yang ◽  
Feilong Ye
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Dynamic Loading ◽  
High Strength Steel ◽  
High Strength ◽  
Tensile Tests ◽  
Reinforcing Steel ◽  
Test Results ◽  
Cross Sectional ◽  
Steel Bars

The tensile behaviors of corroded steel bars are important in the capacity evaluation of corroded reinforced concrete structures. The present paper studies the mechanical behavior of the corroded high strength reinforcing steel bars under static and dynamic loading. High strength reinforcing steel bars were corroded by using accelerated corrosion methods and the tensile tests were carried out under different strain rates. The results showed that the mechanical properties of corroded high strength steel bars were strain rate dependent, and the strain rate effect decreased with the increase of corrosion degree. The decreased nominal yield and ultimate strengths were mainly caused by the reduction of cross-sectional areas, and the decreased ultimate deformation and the shortened yield plateau resulted from the intensified stress concentration at the nonuniform reduction. Based on the test results, reduction factors were proposed to relate the tensile behaviors with the corrosion degree and strain rate for corroded bars. A modified Johnson-Cook strength model of corroded high strength steel bars under dynamic loading was proposed by taking into account the influence of corrosion degree. Comparison between the model and test results showed that proposed model properly describes the dynamic response of the corroded high strength rebars.

Habitual loading results in tendon hypertrophy and increased stiffness of the human patellar tendon

2008 ◽  
Vol 105 (3) ◽  
pp. 805-810 ◽  
Author(s):  
C. Couppé ◽  
M. Kongsgaard ◽  
P. Aagaard ◽  
P. Hansen ◽  
J. Bojsen-Moller ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Patellar Tendon ◽  
Cross Sectional Area ◽  
Isometric Contractions ◽  
Sectional Area ◽  
Cross Sectional ◽  
Strength Difference ◽  
Distal Tendon

The purpose of this study was to examine patellar tendon (PT) size and mechanical properties in subjects with a side-to-side strength difference of ≥15% due to sport-induced loading. Seven elite fencers and badminton players were included. Cross-sectional area (CSA) of the PT obtained from MRI and ultrasonography-based measurement of tibial and patellar movement together with PT force during isometric contractions were used to estimate mechanical properties of the PT bilaterally. We found that distal tendon and PT, but not mid-tendon, CSA were greater on the lead extremity compared with the nonlead extremity (distal: 139 ± 11 vs. 116 ± 7 mm2; mid-tendon: 85 ± 5 vs. 77 ± 3 mm2; proximal: 106 ± 7 vs. 83 ± 4 mm2; P < 0.05). Distal tendon CSA was greater than proximal and mid-tendon CSA on both the lead and nonlead extremity ( P < 0.05). For a given common force, stress was lower on the lead extremity (52.9 ± 4.8 MPa) compared with the nonlead extremity (66.0 ± 8.0 MPa; P < 0.05). PT stiffness was also higher in the lead extremity (4,766 ± 716 N/mm) compared with the nonlead extremity (3,494 ± 446 N/mm) ( P < 0.05), whereas the modulus did not differ (lead 2.27 ± 0.27 GPa vs. nonlead 2.16 ± 0.28 GPa) at a common force. These data show that a habitual loading is associated with a significant increase in PT size and mechanical properties.

Diet-related changes in mechanical properties of rat vertebrae

1992 ◽  
Vol 262 (2) ◽  
pp. R318-R321 ◽  
Author(s):  
G. J. Salem ◽  
R. F. Zernicke ◽  
R. J. Barnard
Keyword(s):  
Mechanical Properties ◽  
Vertebral Body ◽  
Calcium Metabolism ◽  
Bone Mineralization ◽  
Maximum Load ◽  
Control Group ◽  
Buffer Solution ◽  
Cross Sectional ◽  
Lumbar Vertebral Body ◽  
Significant Difference

High fat and sucrose (HFS) diets may induce glucose intolerance, alter calcium metabolism, and lead to deficits in bone mineralization, development, and mechanical properties. To determine the mechanical and structural consequences of a HFS diet on rapidly growing vertebrae, female Sprague-Dawley rats (8 wk) were assigned randomly (2:1) either to a control group (n = 20) fed a low-fat complex-carbohydrate diet or an experimental group (n = 10) fed a HFS diet for 10-12 wk. The sixth lumbar vertebral body (L6) was isolated from the pedicles, morphological measures were taken, and compression was tested at a fast strain rate, while immersed in a warmed (37 degrees C) isotonic physiological buffer solution. No significant difference in body mass existed between HFS and control groups; nevertheless, HFS L6 cross-sectional areas, lengths, and volumes were significantly smaller than controls. The HFS L6 also had significantly lower mechanical properties, including initial maximum load, energy at initial maximum load, and strain energy density at initial maximum load. Diets high in sucrose and fat content have been associated with changes in calcium metabolism, and the results of the current study suggest that in immature vertebrae, a HFS diet may adversely affect vertebral body mechanical integrity and strength.

Effects of Restressing on the Mechanical Properties of Stress-Shielded Patellar Tendons in Rabbits

1996 ◽  
Vol 118 (2) ◽  
pp. 216-220 ◽  
Author(s):  
Noritaka Yamamoto ◽  
Kozaburo Hayashi ◽  
Hiroyuki Kuriyama ◽  
Kazunori Ohno ◽  
Kazunori Yasuda ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Patellar Tendon ◽  
Stress Shielding ◽  
Tangent Modulus ◽  
Tissue Change

We studied the effects of restressing on the mechanical properties and morphology of stress-shielded rabbit patellar tendons. After completely unloading the patellar tendon for 1 to 3 weeks, tension was again applied to the tendon for the subsequent 3 to 12 weeks. Although the stress shielding markedly decreased the tangent modulus and tensile strength of the tendon, restressing significantly increased them. However, the mechanical properties of the tendon were not completely recovered even after a prolonged period of restressing. The microstructure of the tendon was also restored by although the recovery was incomplete. These results indicate that the mechanical properties and morphology of tendinous tissue change in response to mechanical demands.

Effect of stress shielding on the mechanical properties of healing tissue in the patellar tendon after removal of its central third

2002 ◽  
Vol 2002.13 (0) ◽  
pp. 21-22
Author(s):  
Takafumi HIRO ◽  
Yoshiaki KITAMURA ◽  
Harukazu TOHYAMA ◽  
Kazunori YASUDA ◽  
Kozaburo HAYASHI
Keyword(s):  
Mechanical Properties ◽  
Patellar Tendon ◽  
Stress Shielding ◽  
Healing Tissue

scholarly journals Microstructural Features and Mechanical Properties after Industrial Scale ECAP of an Al 6060 Alloy

2010 ◽  
Vol 667-669 ◽  
pp. 1153-1158 ◽  
Author(s):  
Philipp Frint ◽  
Matthias Hockauf ◽  
T. Halle ◽  
G. Strehl ◽  
Thomas Lampke ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shear Zone ◽  
High Performance ◽  
Large Scale ◽  
Low Voltage ◽  
Tensile Tests ◽  
Industrial Applications ◽  
Industrial Scale ◽  
Opening Angle ◽  
Cross Sectional

Future applications of ultrafine-grained, high performance materials produced by equal-channel angular pressing (ECAP) will most likely require processing on an industrial scale. There is a need for detailed microstructural and mechanical characterisation of large-scale, ECAP-processed billets. In the present study, we examine the microstructure and mechanical properties as a function of location and orientation within large (50 x 50 x 300 mm³) billets of an Al 6060 alloy produced by ECAP (90° channel angle) with different magnitudes of backpressure. The internal deformation is analysed using a grid-line method on split billets. Hardness is recorded in longitudinal and cross-sectional planes. In order to further characterise the local, post-ECAP mechanical properties, tensile tests in different layers are performed. Moreover, low voltage scanning transmission electron microscopy observations highlight relevant microstructural features. We find that the homogeneity and anisotropy of mechanical properties within the billets depend significantly on the geometry of the shear zone. We demonstrate that deformation gradients can be reduced considerably by increasing the backpressure: The opening-angle of the fan-shaped shear zone is reduced from ψ ≈ 20 ° to ψ ≈ 7 ° when the backpressure is increased from 0 to 150 MPa. Backpressures of 150 MPa result in excellent homogeneity, with a relative variation of tensile mechanical properties of less than 7 %. Our investigation demonstrates that ECAP is suitable for processing homogenous, high performance materials on a large scale, paving the way for advanced industrial applications.

Mechanical Properties of the Rabbit Patellar Tendon

1992 ◽  
Vol 114 (3) ◽  
pp. 332-337 ◽  
Author(s):  
N. Yamamoto ◽  
K. Hayashi ◽  
H. Kuriyama ◽  
K. Ohno ◽  
K. Yasuda ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Structural Properties ◽  
Patellar Tendon ◽  
Tensile Tests ◽  
The Other ◽  
Central Portion ◽  
Mechanical And Structural Properties ◽  
Lateral Portion

The mechanical and structural properties of the patellar tendon fascicle-bone units of rabbit knees were determined by tensile tests, particularly focusing on their local differences. There were no significant differences in the strains measured by a video dimension analyzer among the proximal, middle, and distal regions of the central portion of tendon. The mechanical properties of the medial portion agreed well with those of the central portion. However, significant differences were observed in the tensile strength between the lateral and the other two portions: the tensile strength of the lateral portion was about 16 percent larger than those in the other portions.

Effects of complete stress-shielding on the mechanical properties and histology of in situ frozen patellar tendon

1993 ◽  
Vol 11 (4) ◽  
pp. 592-602 ◽  
Author(s):  
Kazunori Ohno ◽  
Kazunori Yasuda ◽  
Noritaka Yamamoto ◽  
Kiyoshi Kaneda ◽  
Kozaburo Hayashi
Keyword(s):  
Mechanical Properties ◽  
Patellar Tendon ◽  
Stress Shielding

Mechanical properties and collagen cross-linking of the patellar tendon in old and young men

2009 ◽  
Vol 107 (3) ◽  
pp. 880-886 ◽  
Author(s):  
C. Couppé ◽  
P. Hansen ◽  
M. Kongsgaard ◽  
V. Kovanen ◽  
C. Suetta ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Patellar Tendon ◽  
Structural Integrity ◽  
Young Men ◽  
Activity Level ◽  
Cross Linking ◽  
Collagen Concentration ◽  
Cross Sectional ◽  
Age Related

Age-related loss in muscle mass and strength impairs daily life function in the elderly. However, it remains unknown whether tendon properties also deteriorate with age. Cross-linking of collagen molecules provides structural integrity to the tendon fibrils and has been shown to change with age in animals but has never been examined in humans in vivo. In this study, we examined the mechanical properties and pyridinoline and pentosidine cross-link and collagen concentrations of the patellar tendon in vivo in old (OM) and young men (YM). Seven OM (67 ± 3 years, 86 ± 10 kg) and 10 YM (27 ± 2 years, 81 ± 8 kg) with a similar physical activity level (OM 5 ± 6 h/wk, YM 5 ± 2 h/wk) were examined. MRI was used to assess whole tendon dimensions. Tendon mechanical properties were assessed with the use of simultaneous force and ultrasonographic measurements during ramped isometric contractions. Percutaneous tendon biopsies were taken and analyzed for hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP), pentosidine, and collagen concentrations. We found no significant differences in the dimensions or mechanical properties of the tendon between OM and YM. Collagen concentrations were lower in OM than in YM (0.49 ± 0.27 vs. 0.73 ± 0.14 mg/mg dry wt; P < 0.05). HP concentrations were higher in OM than in YM (898 ± 172 vs. 645 ± 183 mmol/mol; P < 0.05). LP concentrations were higher in OM than in YM (49 ± 38 vs. 16 ± 8 mmol/mol; P < 0.01), and pentosidine concentrations were higher in OM than in YM (73 ± 13 vs. 11 ± 2 mmol/mol; P < 0.01). These cross-sectional data raise the possibility that age may not appreciably influence the dimensions or mechanical properties of the human patellar tendon in vivo. Collagen concentration was reduced, whereas both enzymatic and nonenzymatic cross-linking of concentration was elevated in OM vs. in YM, which may be a mechanism to maintain the mechanical properties of tendon with aging.

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