SLR - January 2015 - Kevin J. Mahoney

Biomechanical Comparison of Krackow Locking Stitch versus Nonlocking Loop Stitch with Varying Number of Throws

Reference: Hahn, JM, Inceoglu, S, Wongworawat, M. Biomechanical Comparison of Krackow Locking Stitch versus Nonlocking Loop Stitch with Varying Number of Throws. Am J of Sports Med. 2014 Dec; 42(12):3003-8.

Scientific Literature Review

Reviewed By: Kevin J. Mahoney, DPM
Residency Program: HealthPartners Institute for Education and Research/Regions Hospital

Podiatric Relevance: This article compares the biomechanical strength of two common tendon repair suture techniques. The Krackow suture technique and the Whipstitch technique are both commonly used in primary repair of tendons as well as with tendon transfers. The hypothesis of the study was that the different suture techniques with varying number of suture loops would produce different biomechanical effects on tendon function.

Methods: The study was performed using porcine cadaveric flexor tendons. A total of 52 fresh-frozen porcine flexor digitorum tendons were used and assigned into 10 groups. The groups were separated into two suture configurations consisting of the Krackow stitch, and the Whipstitch with varying number of loops. The groups were further divided into 5 groups each consisting of two loops,  four loops,  six loops, eight loops and 10 loops. Each sample was preloaded to 5 N and then cyclically loaded for 200 cycles to 200 N at 1 Hz. Then the tendon-suture construct was analyzed for gap formation, tendon elongation, and tendon end width. The tendons were also tested for failure point. Each tendon was loaded to failure; the ultimate strength and mode of failure were recorded. Data were evaluated with two-way analysis of variance.

Results: The Krackow stitch produced less gap compared with the whipstitch (15.2mm vs 18.9 mm; p = .012). Gap formation was larger when the number of loops increased from 2 to 6 (p = .015). The Krackow technique was also found to increase the tendon length after cyclic loading, whereas the whipstitch shortened the length of the tendon (1.17 mm vs –0.14mm; p < .001). The Krackow technique also better preserved the transverse width (–0.64mm vs –1.39mm; p = .001). Both techniques were found to have similar ultimate strength (322.1 N vs 319.7 N; p = .676). All failures were due to suture breakage. There was no statistical difference in tendon elongation, width, failure load, or mode regardless of the number of throws.

Conclusions: Primary repair of tendon injuries such as the Achilles tendon, as well as multiple tendon transfer techniques in the foot and ankle are well documented. Both the Krackow locking suture technique and the nonlocking Whipstitch technique are commonly utilized in foot and ankle surgery. This study supports previous evidence that the Krackow suture technique is recommended for tendon reconstruction. Interestingly, there was no statistical improvement in strength with increased number of throws or loops. It should be noted that the study was performed with porcine flexor tendons and not human tissue. Also, the test was performed using non-physiologic load forces, without direct end to end repair. 

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