Abstract
Abstract
Objectives
The patella tendon (PT) is commonly used as a graft material for anterior cruciate ligament reconstruction (ACLR). The function of the graft is to restore the mechanical behaviour of the knee joint. Therefore, it is essential that a robust methodology be developed for the mechanical testing of the PT, as well as for the tissue engineered grafts derived from this tissue. Our objectives were to (1) survey the literature, in order to define the state-of-the-art in mechanical testing of the PT, highlighting the most commonly used testing protocols, and (2) conduct validation studies using porcine PT to compare the mechanical measurements obtained using different methodological approaches.
Methods
A PubMed search was performed using a boolean search term to identify publications consisting of PT tensile testing, and limited to records published in the past ten years (2010–2020). This returned a total of 143 publications. A meta-analysis was undertaken to quantify the frequency of commonly used protocol variations (pre-conditioning regime, strain rates, maximum strain, etc.). Validation studies were performed on porcine PT (n=4) using Instron tensile testing apparatus to examine the effect of preconditioning on low-strain (toe-region) mechanical properties.
Results
Ramp-to-failure testing was found to be most commonly performed (included in over 90 % of publications), followed by stress relaxation and cyclic testing (∼25 %). Preconditioning was most commonly cyclic (27 %), involving 10–100 cycles. Validation studies show the number of cycles and duration of preconditioning, has no significant effect on toe region transition strain, transition stress, or sensitivity to increasing strain.
Conclusions
There is a lack of standardisation in the mechanical testing of PT, which could have implications for the comparison of studies conducted using different protocols. However, variations in preconditioning regime have no effect on low-strain mechanical properties.
