Is Nice knot suture comparable to wire for cerclage fixation? A biomechanical performance study.

BACKGROUND

Cerclage fixation is a known orthopedic technique shown to be beneficial for circumferential augmentation when screw fixation cannot be used or is undesirable. However, ongoing advances in suture materials and knot techniques exist, and there is a paucity of evidence existing which evaluates comparisons between the two. The objective of this study was to investigate the strength and durability of cerclage fixation between the Nice knot suture technique and monofilament wire.

METHODS

Static displacement over time and compression load testing were analyzed. Compression testing was conducted with the Jamar Hydraulic Hand Dynamometer. Distraction testing was conducted using the Instron test system with its associated program. The Nice knot was tied using number 2 and number 5 FiberWire (Arthrex) and compared to monofilament wire. Clinical failure (displacement of 10 mm), absolute failure (opening of the knot or material failure), maximum compression achieved, and steady state compression maintained were the outcomes of interest.

RESULTS

Double-stranded monofilament wire produces maximum consistent compression of 90 kg, followed by single-stranded monofilament wire (60 kg). Number 5 FiberWire has a higher maximum compression load than number 2 FiberWire (50 kg vs. 22 kg), but it is lower than that of the double-stranded monofilament wire constructs. When compared to the single-stranded monofilament construct, the number 5 FiberWire Nice knot is comparable ( < .05). Average steady state compression achieved after 10 minutes of resting showed double-stranded monofilament wire to be 65 kg compared to single- stranded monofilament wire at 42 kg, which when, compared to suture, number 5 FiberWire measured at 15 kg and number 2 FiberWire at 8 kg. Average tension results from Instron distraction testing showed the double-stranded monofilament wire construct was able to withstand greater forces up to a displacement of 6 mm, after which the number 5 FiberWire Nice knot was stiffer. Number 5 FiberWire shows the most linear tension relationship, revealing it more efficiently withstands elastic forces. Load to failure was higher in the number 5 FiberWire Nice knot construct than that in both the monofilament wire constructs. The modes of failure for the Nice knot were always at the knot suture interface rather than at the knot.

CONCLUSION

We propose this suture technique to be a viable alternative method for cerclaging to fix upper limb long-bone fractures.