A biomechanical comparison of multistrand flexor tendon repairs using an in situ testing model

An in situ testing model was used to evaluate the performance of zone II fl exor tendon repairs and to compare the biomechanical properties of 4-strand repairs with 2- and 6-strand repairs. Fifty digits from human cadaveric ha nds were mounted in a custom apparatus for in situ tensile testing. Intrate ndinous metallic markers were placed so that gap formation could be determi ned by fluoroscopy during tensile testing. Three 4-strand repairs (the 4-st rand Kessler, the cruciate, and a locked modification of the cruciate repai r) were compared with the 2-strand Kessler and the 6-strand Savage repairs. Ultimate tensile strength, load at 2-, 3-, and 4-mm gap formation, and wor k of flexion were determined. Work of flexion, while increased for the mult istrand repairs, did not show a statistically significant correlation with the number of strands crossing the repair site. The tensile strength of the 6-strand repair was significantly greater than each of the 2 or 4-strand r epairs. The tensile strength of all 4-strand repairs was significantly grea ter than the 2-strand repair. The 6-strand repair and the 2 cruciate repair s demonstrated a statistically increased resistance to gap formation compar ed with the 2-strand Kessler repair, but notably there was no statistically significant difference in gap resistance between the 2- and 4-strand Kessl er repairs. This in situ tensile testing protocol demonstrated that 4- and 6-strand repairs have adequate initial strength to withstand the projected forces of early active motion protocols. Three of the 4 multistrand repairs demonstrated improved gap resistance compared with the 2-strand repair. Th e presence of the second suture in the Kessler configuration significantly increases its strength bur not its gap resistance. (J Hand Surg 2000;25A:49 9-506. Copyright (C) 2000 by the American Society for Surgery of the Hand.) .