Biomechanical Evaluation of Spring Ligament Augmentation With the FiberTape Device in a Cadaveric Flatfoot Model

Abstract

Background: The structural importance of the spring ligament complex in arch stability has been described. Furthermore, the pathology of this complex is often noted in patients with posterior tibial tendon dysfunction. The purpose of this biomechanical study was to evaluate spring ligament repair alone versus augmentation with the FiberTape device in a cadaveric flatfoot model. Methods: Eight paired, below-the-knee, cadaveric specimens underwent flatfoot creation and reconstruction. The experimental group received augmentation with FiberTape (InternalBrace). After potting, specimens were loaded statically to measure talonavicular contact pressures and flatfoot correction. Cyclic loading was performed in a stepwise fashion. Loading was performed at 1 Hz and 100 cycles, at 100-N intervals from 500 to 1800 N, with the Achilles tendon also loaded to simulate weightbearing in the postoperative period. Results: Control specimen analysis demonstrated failures of 8 of 8 (100%) spring ligament suture repairs, occurring through suture cut-through (5 specimens), suture fatigue and elongation (2), or knot failure (1). One of 8 (12.5%) FiberTape-augmented repairs failed after cyclic loading. The difference in number of repair failures was statistically significant between the 2 groups ( P = .0014). Analysis revealed that at forces of 1600 N ( P = .03) and 1700 N ( P = .02) there were statistically significant differences between the FiberTape-augmented group and the control group, with a greater collapse in the lateral Meary talo–first metatarsal angle in the controls. There was no significant difference or abnormal increase in contact pressures of the talonavicular joint in both groups. Conclusion: FiberTape augmentation of the spring ligament appears biomechanically safe and effective under cyclic loading. Clinical relevance: Spring ligament augmentation with this device may be another biomechanically safe and reasonable treatment modality for surgeons during flatfoot reconstruction. It is possible that early protected weightbearing after these procedures may be performed.