Double-loop cerclage resists greater loads for more cycles than twist and single-loop cerclage.

OBJECTIVE

To compare the mechanical performance of cerclage secured with twist, single-loop, and double-loop knots subjected to cyclic loading.

STUDY DESIGN

In vitro biomechanical study.

SAMPLE POPULATION

Twist, single-loop and double-loop cerclage configurations of 1.0 mm wire.

METHODS

The peak load resisted by each cerclage type was determined (n = 6). Cerclage were loaded cyclically to 80%, 60%, 40%, or 20% of its peak load (n = 8 per load level). The number of cycles until each cerclage loosened (residual tension <10 N) was recorded.

RESULTS

All wires that failed did so by loosening. Twist cerclage cycled to 390 N and 290 N loosened within the first 10 cycles, and, when cycled to 100 N, they loosened by 250 cycles. All twist knots loosened by untwisting. Single-loop cerclage cycled to 320 N loosened within 10 cycles. At 240 N, 5 single-loop cerclage resisted 250 cycles before loosening. At 160 N, 2 of the 8 single-loop cerclage did not loosen by 100 000 cycles. When cycled to 640 N, one of the double-loop cerclage did not loosen following 500 000 cycles. When cycled to 480 N, 3 of the 8 wires did not loosen.

CONCLUSION

Double-loop cerclage will be tighter and are better able to resist cycling than twist or single-loop cerclage.

CLINICAL SIGNIFICANCE

Use of double-loop cerclage to stabilize bone fragments or prevent fissure propagation can be expected to provide greater resistance to loosening than twist or single-loop cerclage, both initially and with repeated loading.