3D Printed Clamps for In Vitro Tensile Tests of Human Gracilis and the Superficial Third of Quadriceps Tendons

Abstract

Recent soft tissue studies have reported issues that occur during experimentation, such as the tissue slipping and rupturing during tensile loads, the lack of standard testing procedure and equipment, the necessity for existing laboratory equipment adaptation, etc. To overcome such issues and fulfil the need for the determination of the biomechanical properties of the human gracilis and the superficial third of the quadriceps tendons, 3D printed clamps with metric thread profile-based geometry were developed. The clamps’ geometry consists of a truncated pyramid pattern, which prevents the tendons from slipping and rupturing. The use of the thread application in the design of the clamp could be used in standard clamping development procedures, unlike in previously custom-made clamps. Fused deposition modeling (FDM) was used as a 3D printing technique, together with polylactic acid (PLA), which was used as a material for clamp printing. The design was confirmed and the experiments were conducted by using porcine and human tendons. The findings justify the usage of 3D printing technology for parts manufacturing in the case of tissue testing and establish independence from the existing machine clamp system, since it was possible to print clamps for each prepared specimen and thus reduce the time for experiment setup.

Development of a 3D Printed Double-Acting Linear Pneumatic Actuator for the Tendon Gripping

“…We also present a special tool for machining the inner cylinder body. This study is an extension of previously published work [ 21 ]. Finally, conclusions were drawn and the final design is proposed at the functional prototype level.…”

“…To validate the design and functionality of the proposed actuator, we decided to perform the stress-relaxation test of tendons. The experiment setup and tendons preparation can be found in [ 21 ]. Moreover, the same interpretation applies to the validation of the actuator design in this study, as the same actuator was used for gripping the proposed clamps along with the human gracilis and quadriceps tendons.…”

“…Contamination of the test fluid was kept to a minimum. The application tests of the actuator were carried out with the porcine [ 26 ] and human gracilis and quadriceps tendons [ 21 ]. It was necessary to select the appropriate cylinder diameter and to determine the gripping force (axial force) in order to calculate the expected ultimate tensile force (radial force) of both types of tendons.…”

“…To fulfil the gripping task, it was decided to design the cylinder with a diameter of 50 mm, which allows the maximum axial force of 1900 N to be achieved. However, gripping in advance has been solved with the new tendon clamping technique presented in [ 21 ] using bolt preloads. With this technique, the actuator was used just to hold the clamps together with the tendon within the jaws with 0.3 MPa of pressure.…”

The Development of a Gracilis and Quadriceps Tendons Calibration Device for Uniaxial Tensile Tests

“…to successfully develop something new. The result and an example of such collaboration can be seen in [22][23][24][25][26][27][28]. The need to make this calibration device arose from the work presented in [21].…”