Tendon

Tendon

1. 60% of the wet weight is water

2. 60%-85% of the dry weigth is composed of type 1 collagen

   • Responsible for the elasticity of the tissue

3. Has the structure of the type "Crimp" or "Zigzag" that allow the tissue to suffer up to 3% of strain without damage

4. The high amount of organized components (collagen) makes the T2 of tendons really short

   • Traditional MRI can not capture the signal
     • UTE (Ultra Short Time of Echo) comes as a alternative to capture this type of signal. UTE uses echos with 10ms
       • Usually on of the reasons why the TE is not that small is because we need time to turn on the gradients

5. There is the hypothesis that mechanical changes occours before the anatomical changes

6. During stretching two main events occour: Decrease of crimps and their angle gets flat and the water redistributes within the tissue

   • The diameter of large collagen fibrils decreases and less interspace areas can be found in loaded tendons

7. Some papers found a increase of UTE-MRI parameters after exercise and some did not found significant differences with load (Load < 10N for the authors previous study)

   • The goal of the paper is to apply a higher amount of load (>10N) and measure T2*, T1 and MTR
     • 6 samples were used, that came from 3 donors. The samples were divided randomly into two groups
       • Group A: One loading step (15 N)
       • Group B: Two loading steps (15 and 30 N)
       • They load the tendons with a loading device. The amount of load is measure by the deformatiospringsn and stiffness of the spring
         • Three acquisition protocols were used: dual-echo 3D-UTE-Cones sequences (T2* - 8:36min), TR 3D-UTE-Cones sequences (T1 - 20:08min), and 3D-UTE-MT-Cones sequences (MT - 7:28min)
           • High resolution: 0,20 x 0,20
       • Segmented into two ROIs: whole and core regions of tendon
     • The T2* of all the samples showed a decrease in both ROIs (whole and core regions) with load
       • T1 did not have a consistent trend. Some increase after the first load and some decrease
         • MTR also did not have a consistent trend but in most cases there was a increase in the MTR with load
       • However the decrease was smaller after the second step of load
       • Only the decrease of the T2* after the first load (core regions and whole) achieved statistical significance
     • RESULTS: The results for the T2* measurements DO NOT agree with the literature. Some papers found a increase on T2* after load or exercise and others a decrease or no change
       • LIMITATIONS: small number of samples and the age of the donors