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19. Effects of restressing on the mechanical properties of stress-shielded patellar tendons in rabbits

Author

Yamamoto, Noritaka, Hayashi, Kozaburo, Kuriyama, Hiroyuki, Ohno, Kazunori, Yasuda, Kazunori, and Kaneda, Kiyoshi

Subjects
Patella -- Research, Tendons -- Research, Rabbits as laboratory animals -- Research, Morphology (Animals) -- Research, Engineering and manufacturing industries, Science and technology
Abstract

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 restressing, although the recovery was incomplete. These results indicate that the mechanical properties and morphology of tendinous tissue change in response to mechanical demands.

Published
1996

44. Effects of Stress Shielding on the Transverse Mechanical Properties of Rabbit Patellar Tendons

Author

Yamamoto, Ei, Hayashi, Kozaburo, and Yamamoto, Noritaka

Subjects
Tendons -- Analysis, Ligaments -- Analysis, Strength of materials -- Testing, Engineering and manufacturing industries, Science and technology
Abstract

With the aim of studying mechanisms of the remodeling of tendons and ligaments, the effects of stress shielding on the rabbit patellar tendon were studied by performing tensile and stress relaxation tests in the transverse direction. The tangent modulus, tensile strength, and strain at failure of non-treated, control patellar tendons in the transverse direction were 1272 kPa, 370 kPa, and 40.5 percent, respectively, whereas those of the tendons stress-shielded for 1 week were 299 kPa, 108 kPa, and 40.4 percent, respectively. Stress shielding markedly decreased tangent modulus and tensile strength in the transverse direction, and the decreases were larger than those in the longitudinal direction, which were determined in our previous study. For example, tensile strength in the transverse and longitudinal direction decreased to 29 and 50 percent of each control value, respectively, after 1 week stress shielding. In addition, the stress relaxation in the transverse direction of stress-shielded patellar tendons was much larger than that of nontreated, control ones. In contrast to longitudinal tensile tests for the behavior of collagen, transverse tests reflect the contributions of ground substances such as proteoglycans and mechanical interactions between collagen fibers. Ground substances provide lubrication and spacing between fibers, and also confer viscoelastic properties. Therefore, the results obtained from the present study suggest that ground substance matrix, and interfiber and fiber-matrix interactions have important roles in the remodeling response of tendons to stress. [S0148-0731 (00)00806-2]

Published
2000

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