Mechanical and structural properties of collagen fascicles ... - ISMC

Similarly, a thin bundle of collagen (~40 mm in length and ~2 mm in diameter) was isolated
proximal to the rupture site, i.e. from the healthy part of the tendon. From each sample two adjacent
strands of fascicles (ø 300 - 530 µm) enclosed in a fascicular membrane were dissected. The
specimen was deformed to ~3 % strain in three independent load-displacement cycles in a small-
scale mechanical rig. Cycle 1: the fascicles and the fascicular membrane were intact. Cycle 2: one
fascicle was transversally cut while the other fascicle and the fascicular membrane were kept intact.
Cycle 3: both fascicles were cut in opposite ends while the fascicular membrane was left intact. A
decline in peak force of 45 % and 55 % from cycle 1 to cycle 2, and 93 % and 92 % from cycle 2 to
cycle 3 was observed in the patellar and Achilles tendon fascicles, respectively. A decline in
stiffness of 39 % and 60 % from cycle 1 to cycle 2, and of 93 % and 100 % from cycle 2 to cycle 3
was observed in the patellar and Achilles tendon fascicles, respectively.
The main finding of the study was that lateral force transmission between adjacent
collagen fascicles in human tendons is small or negligible, suggesting that tendon fascicles largely
act as independent structures and that force transmission principally takes place within the
individual fascicles.
Study IV
The purpose of the study was to examine the effect of a corticosteroid environment on the tensile
strength of isolated collagen fascicles and to examine the effects of corticosteroids on cross-links
(hydroxylysyl pyridinoline and lysyl pyridinoline) density in isolated collagen fascicles from rat
tail-tendon. A ~60 mm section was cut from the proximal end of the skinned rat-tail, subsequently
single fascicles were teased out and divided into a proximal and distal section. The strands were
incubated in either high (1mL of 40 mgmL -1 mixed with 0.5 mL saline 9% - HC) or low
concentration (1mL of 40 mgmL -1 mixed with 2 mL saline 9% - LC) of methylprednisolone acetate
(Depo-medrol®) for 3 or 7 days while the control segment from the same fascicle was kept in
saline. There was an equal number of fascicles strands from the proximal and the distal part of the
specimen in each of the intervention groups and the corresponding control group. The main findings
in this study were that in the HC groups the strength was reduced after 3 (16.6±4.6 MPa) and 7
(8.6±1.7 MPa) days compared to the controls (30.2±5.0 MPa, 25.6±4.6 Mpa respectively), P