Corticosteroids reduce the tensile strength of isolated collagen fascicles.
BACKGROUND
Overuse tendon injuries are frequent. Corticosteroid injections are commonly used as treatment, although their direct effects on the material properties of the tendon are poorly understood.


OBJECTIVE
To examine the influence of corticosteroids on the tensile strength of isolated collagen fascicles.


METHODS
Controlled laboratory study.


METHODS
Single strands (300-500 mum) of rat-tail collagen fascicles were incubated in either high (1 mL of 40 mgmL(-1) mixed with 0.5 mL saline 9%) or low (1 mL of 40 mgmL(-1) mixed with 2 mL saline 9%) concentration of methylprednisolone acetate (Depomedrol) for 3 or 7 days, while the control segment from the same fascicle was kept in saline (N = 64). After the incubation period, the fascicles underwent displacement to failure in a mechanical test rig at 0.13 mm/s, and thereafter hydroxylysyl pyridinoline and lysyl pyridinoline cross-link content was evaluated in a high-performance liquid chromatography system. Data for each group were analyzed with a 2-way analysis of variance (time x incubation) for ultimate stress (mean +/- standard deviation).


RESULTS
In the high-concentration groups, 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 and 25.6 +/- 4.6 MPa, respectively; P < .05). In the low-concentration groups, strength was reduced after 3 (12.0 +/- 3.1 MPa) and 7 days (10.9 +/- 2.5 MPa) compared to the controls (31.5 +/- 5.0 MPa and 32.4 +/- 5.6 MPa, respectively; P < .05). The amount of cross-linking was unaffected by the intervention.


CONCLUSIONS
Data show that the tensile strength of isolated fascicles is markedly reduced after 3- and 7-day incubation in both high and low concentration of corticosteroids, although the observed effect on whole tendon remains unknown.


CONCLUSIONS
Corticosteroids may weaken specific regions of the injected tendon and leave it more prone to rupture. This weakening effect is manifested in the individual collagen fascicles that constitute the tendon.
Haraldsson
Bjarki Thor
BT
Institute of Sports Medicine Copenhagen, Bispebjerg Hospital, Bispebjerg Bakke 23, 2400 Copenhagen NV, Denmark.
Langberg
Henning
H
Aagaard
Per
P
Zuurmond
Anne-Marie
AM
van El
Benno
B
Degroot
Jeroen
J
Kjaer
Michael
M
Magnusson
S Peter
SP
D000818:Animals; D003094:Collagen / Q000502:physiology*; D005938:Glucocorticoids / Q000494:pharmacology* / Q000627:therapeutic use; D066298:In Vitro Techniques; D008297:Male; D008775:Methylprednisolone / Q000031:analogs & derivatives* / Q000494:pharmacology; D000077555:Methylprednisolone Acetate; D051381:Rats; D013708:Tendon Injuries / Q000188:drug therapy; D013718:Tensile Strength / Q000187:drug effects*
D005938:Glucocorticoids; D000077555:Methylprednisolone Acetate; D003094:Collagen; D008775:Methylprednisolone