Influence of Suture Material on the Biomechanical Behavior of Suture-Tendon Specimens

Authors: Bisson LJ, Manohar LM, Wilkins RD, Gurske-Deperio J, Ehrensberger MT.

References: Am J Sports Med. 2008 Mar 21

BACKGROUND: Despite technical advances in rotator cuff surgery, recurrent or persistent defects in the repaired tendon continue to occur. Improved strength of sutures and suture anchors has resulted in the most common site of failure being the suturetendon interface.

HYPOTHESIS: The type of suture material used has a significant effect on the biomechanics of the suture-tendon interface.

STUDY DESIGN: Controlled laboratory study.

METHODS: Thirty-two bovine infraspinatus specimens were randomly assigned to simple suture fixation using No. 2 Fiberwire, Ultrabraid, Orthocord, or Ethibond. Each specimen was subjected to cyclic testing from 5 to 30 N for 30 cycles, followed by load-to-failure testing.

RESULTS: Cyclic testing revealed significantly greater elongation with Ultrabraid, whereas peak-to-peak displacements were lowest for Fiberwire and greatest for Orthocord. Load-to-failure testing revealed no significant differences between any suture material for ultimate tensile load. Fiberwire and Orthocord repairs had the highest stiffness. The most common failure mode during load-to-failure testing was suture breakage in Ethibond specimens and suture cutting through the tendon in the polyblend suture specimens.

CONCLUSION: The type of suture material has a significant effect on the biomechanical behavior of the suture-tendon interface.

CLINICAL RELEVANCE: The type of suture may influence early gap formation and ultimate healing of rotator cuff repairs.

Load to Failure.
Load-to-failure testing showed no significant differences between any suture material with respect to ultimate tensile load. There was a significant difference in stiffness between several suture-tissue specimens, with Ethibond constructs being less stiff than Orthocord and Fiberwire but not significantly different than Ultrabraid. Fiberwire was stiffer than Ultrabraid but was not significantly stiffer than Orthocord.

Mechanism of Failure.
All Fiberwire and Ultrabraid specimens failed as a result of suture pulling through the tendon. Three Ethibond and 6 Orthocord specimens failed by suture pulling through the tendon; the remaining 5 Ethibond and 2 Orthocord specimens failed by suture breakage away from the knot.

Cyclic Loading.
Cyclic testing showed significantly lower elongation for Fiberwire than Ultrabraid, but the magnitude of the differences between suture materials was minimal (<0.1 mm). Peak-to-peak displacement was significantly greater for Ethibond and Orthocord, but once again the magnitude of this difference was relatively small (approximately 0.3 mm)

Load-to-Failure Testing.
Ultimate tensile load was highest in Fiberwire, followed by Ultrabraid, Orthocord, and finally Ethibond. Stiffness was greatest for Fiberwire and Ultrabraid, followed by Orthocord and finally by Ethibond.

 Biomechanical Behavior of Suture-Tendon Specimensa

Cyclic loading test
    Elongation, mm0.98 (0.29)0.95 (0.40)1.04 (0.18)1.48 (0.30)b
    Peak-to-peak displacement, mm0.87 (0.09)c0.55 (0.12)b1.02 (0.08)b0.74 (0.08)c
Load-to-failure test
    Ultimate tensile load, N133 (15)152 (56)181 (55)165 (49)
    Stiffness, N/mm9.2 (2.3)c16.5 (3.8)d14.8 (2.5)e12.2 (2.5)f

aValues are mean (SD).
bSignificantly different versus all others.
cSignificantly different versus Fiberwire and Orthocord.
dSignificantly different versus Ethibond and Ultrabraid.
eSignificantly different versus Ethibond.
fSignificantly different versus Fiberwire.


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