Knot Security and End Suture Length

 

INTRODUCTION

Knot tying plays an important role in tendon repair strength. This is determined by multiple factors: suture material, knot configuration, tightness of throws and end suture length. Knot configuration in tendon repair is variable in clinical practice. Commonly used knot configurations include: 2:1:1:1, 2:1:1:1:1, 1:1:1:1:1, and 2:1:2. End suture length is also variable ranging between 2-4mm. In general the ESL is cut short in order to minimise the amount of suture material at the repair site and thus decrease adhesion formation and prevent catching.

OBJECTIVE

Investigate knot security in core flexor tendon repair using different knot configurations and ESLs.

METHODS

Part 1:

24 human cadaveric flexor tendons were repaired using either 4-strand Adelaide repair technique or 6-strand Tsai repair technique. The repairs were performed using 4-0 Ethibond, 4-0 Fibrewire or 4-0 Fibreloop. The tendon repairs were subjected to load-to-failure testing. Outcome measures were: 2mm gap force, ultimate tensile strength, and mode of failure.

Part 2:

12 different knot configurations were tied using 4-0 Ethibond and 4-0 Fibrewire. The knots were looped around 2 steel rods and subjected to load-to-failure testing until either the knot unravelled or the suture rupture. Outcome measures were: ultimate tensile strength and mode of failure. Once the optimum knot configuration was determined, different ESL’s were analysed to determine the optimum length.

RESULTS

Part 1:

The Fibrewire and Fibreloop repairs had significantly higher maximum tensile strength than the Ethibond repairs (mean 57.3N and 63.0N vs. 43.1N). The predominant mode of failure overall was by knot unravel.

Part 2:

Using 4-0 Ethibond, the lowest tensile strength was demonstrated with the 1:1 knot configuration (2.0N) and the highest tensile strength with the 3:3:3 knot configuration (27.9N). The optimum knot configurations were 2:1:1:1 and 1:1:1:1:1. Fibrewire was significantly stronger than Ethibond when used in both the 2:1:1:1 and 1:1:1:1:1 knot configurations (p<0.0001). Using 4-0 Fibrewire, the 1:1:1:1:1 knot configuration achieved knot security at 8mm ESL.

CONCLUSION

The predominant mode of flexor tendon repair failure was by knot unravel. Suture material, knot configuration, and ESL all play a significant role in knot security. The optimum repair in this study was achieved with 4-0 Fibrewire with a 1:1:1:1:1 knot configuration using an 8mm ESL.