Biomedical Engineering Reference
In-Depth Information
4.5 Nonuniform Biomechanical Properties Between Ligament/
Tendon Substance and Its Enthesis
The complexity and geometric irregularity of insertion sites makes it very difficult
to separate the biomechanical properties of the insertion sites and the ligament or
tendon midsubstance. Nevertheless, efforts have been made in the development of
testing devices and procedures such that a better understanding of the variation in
these properties can be made and quantitative data can be obtained.
4.5.1 Cross-Sectional Area Measurement
Accurate measurements of the cross-sectional area of the ligament or tendon
substance are necessary in the determination of stresses in these tissues during
uniaxial tensile tests. In the early days, devices and techniques included dial
calipers, constant pressure area micrometers, and thickness micrometers, but
these devices all required physical contact with the specimen, causing deforma-
tion and thus affecting the cross-sectional area measurements. In our laboratory,
we developed a laser micrometer to determine the cross-sectional shape and area
of soft tissue without needing to make contact with the specimen [
22
,
23
].
Recently, we have used a laser micrometer system with charge-coupled device
(CCD) laser displacement sensors to rapidly measure the cross-sectional area of
soft tissues, including those containing concavities [
24
]. This system has proven
able to determine cross-sectional area of soft tissues in an accurate, repeatable,
and rapid manner.
A schematic of the system and frame is shown in Fig.
4.9a
. The device is
composed of two main components: a CCD laser displacement sensor and a rotary
Fig. 4.9
(
a
) A simplified schematic of the charge-coupled device (CCD) laser reflectance system
and frame. (
b
) A diagram depicting an overhead view of the CCD laser reflectance system with a
biological specimen over the center of rotation (COR) of the system (reproduced, with permission,
from [
24
])
Search WWH ::
Custom Search