SLR - February 2015 - Lisa D. Breshears

Knotted Versus Knotless Suture Bridge Repair of the Achilles Tendon Insertion: A Biomechanical Study

Reference: Cox JT, Shorten PL, Gould GC, Markert RJ, Barnett MD Jr, Laughlin RT. Knotted Versus Knotless Suture Bridge Repair of the Achilles Tendon Insertion: A Biomechanical Study. Am J Sports Med. 2014 Nov; 42(11):2727-33.

Scientific Literature Review

Reviewed By: Lisa D. Breshears, DPM
Residency Program: Chino Valley Medical Center, Chino, CA

Podiatric Relevance: Surgical interventions involving insertional Achilles tendinopathy traditionally involve a tendon-splitting approach. However, this approach may not afford the visualization needed to fully debride the pathologic tissue. Completely detaching the Achilles tendon has been utilized to achieve better visualization, but there is no consensus on the optimal reattachment techniques. This article aimed to assess the biomechanical properties of the knotted and knotless suture bridge for the reattachment of the Achilles tendon to the calcaneus. The authors hypothesized that there would be no statistically significant biomechanical difference in the knotted suture bridge and the knotless suture bridge.
 
Methods: This was a cadaveric study in which 10 fresh frozen cadavers were stripped down to the calcanei and the attached Achilles tendon. Each cadaver had one heel assigned to either the knotted suture bridge or the knotless suture bridge. All cadaveric specimens were without foot deformities and gross abnormalities. The Achilles tendon was released from the calcaneus with an incision in all the specimens. The knotted technique utilized two 4.5 Biocork-Corkscrew FT anchors (Arthrex) proximally. They were then fastened to the Achilles tendon in a horizontal mattress technique and tied with five hand-tied knots. One tail end was cut, and the other tail end was then threaded into the 3.5 mm Bio-PushLock anchor (Arthrex). The knotless technique utilized four SwiveLock Anchors (Arthrex) without tying any knots. Suture anchors were all donated by Arthrex. The specimens were then attached to a material testing machine, and several reference points were placed in order to measure repair site displacement, gapping, and tendon strain. The authors also assessed for the reattached footprint size, ultimate load at failure, and tendon stiffness.

Results: When the construct was loaded between 10 and 100 N for 2000 cycles, the mean tendon strain was 208 percent greater in the knotless repair group compared to the knotted repair group (p=0.011). The mean load to failure was 62 percent greater in the knotted repair group versus the knotless repair group (p=0.001). There was no statistical significant difference between the two groups for the footprint size (p= 0.40), displacement (p=0.17), and tendon stiffness (p=0.17). There was also no loosing of the anchors, but both study groups had failed at the tendon-suture site.

Conclusion: The authors concluded that the knotted suture bridge was biomechanically superior to the knotless suture bridge. Although this article does indicate that the knotted suture bridge is biomechanically superior, it does so with a cadaveric study. Some of the reasons many surgeons would consider using a knotless suture bridge is because of the decreased risk of wound dehiscence and the tendon thickening from the suture knots. Highly active patients who place more load on the Achilles tendon may be at a higher risk for failure at the tendon-suture interface, and the knotted suture bridge may be indicated for those patients.  

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