Temporal changes in the tensile strength of ultra-high-molecular-weight polyethylene cable embedded in muscle tissue

BackgroundWires and cables have been used extensively for spinal sublaminar wiring, but damages to the spinal cord due to compression by metal wires have been reported. We have used more flexible ultra-high-molecular-weight polyethylene cable (Tekmilon tape) instead of metal wires since 1999 and have obtained good clinical outcomes. Although the initial strength of Tekmilon tape is equivalent to metal wires, the temporal changes in the strength of Tekmilon tape in the body should be investigated to show that sufficient strength is maintained over time until bone union is complete.MethodsTekmilon tape was embedded into the paravertebral muscle of 10-week-old male Japanese white rabbits. Samples were embedded for 0, 1, 3, 6 or 12 months. At the end of each period, sequential straight tensile strength and sequential knot-pull tensile strength were measured.FindingsThe initial strength of Tekmilon tape in muscle tissue was maintained over time, with 92% straight tensile strength and 104% knot-pull tensile strength at 6 months, and values of 77% and 100% at 12 months, respectively. Since single knot is clinically relevant, it is very important that the knot-pull tensile strength did not decrease over a 12-month period. This suggests that temporal changes in the tensile strength of Tekmilon tape are negligible at 1 year.InterpretationTekmilon tape maintains sufficient strength in vivo until bone union has occurred. It is useful for sublaminar wiring instead of metal materials due to its flexibility and strength and may reduce the risk of neurological damage.