SLR - July 2012 - John D. Schwerdt
Reference: Ortiz C, Wagner E, Mococain P, Labarca G, Keller A, Del Buono A, Maffulli N (2012). Biomechanical comparison of four methods of repair of the Achilles tendon: A laboratory study with bovine tendons. Journal of Bone and Joint Surgery Br Vol. 94-B, No.5, 663-667
Scientific Literature Review
Reviewed by: John D. Schwerdt, MA, DPM
Residency Program: New York Hospital Queens
Podiatric Relevance:
Early weightbearing and ambulation after Achilles tendon repair have been shown to yield better outcomes more frequently in the current literature than traditionally believed. This paradigm shift places more importance on the strength of a surgical knot during the repair. The investigative team used bovine tendons as a human correlate in this laboratory study to compare the Krackow, Dresden, an oblique Dresden technique and a triple-stranded Dresden technique, all using #2 fiberwire.
Methods:
Twenty bovine tendons, extending up to the myotendinous junction, were harvested from two-year-old cows, less than 24 hours after slaughter and immediately frozen, and were defrosted and maintained in normal saline in preparation. They were measured at their narrowest point with calipers and transected four centimeters superior to the insertion, and assigned into four five-tendon groups, each with one of the assigned techniques. The triple-stranded Dresden technique simply took the standard two-stitch approach and added a third equidistant stitch proximally. The oblique technique used crossing suture patterns distally as well as proximally. The standard Dresden and Krackow techniques were performed as previously described in the literature. The strength of the repairs was measured electronically with the assistance of a pulley and clamp, applying a 50N force every five seconds until a five millimeter gap was measured in the tendon, which was operationally defined as failure.
Results:
There was no significant difference in average tendon width between groups, and all the specimens were loaded to failure. The mean resistance to distraction was greatest in the triple-stranded Dresden group (246.1N), and this was significantly greater than that of the Dresden and Krackow groups. The mean load to failure was also highest in the triple-stranded Dresden group (675N), which was significantly greater than the other three groups. Post hoc power analysis showed the experimental design yielded an 86 percent probability to detect a five percent difference in load to gap formation, and an 80 percent probability to detect a five percent difference in load to failure.
Conclusions:
In this experimental model, the triple-stranded Dresden technique yielded the most distraction resistance and greatest load to failure. Studies in the human model would have to be performed to make a stronger case for extrapolating these findings into clinical practice.