Strength of Interference Screw Fixation of Meniscus Prosthesis Matches Native Meniscus Attachments

Purpose: Meniscal surgery is one of the most common orthopaedic surgical interventions. Total meniscus replacements have been proposed as a solution for patients with irreparable meniscal injuries. Reliable fixation is crucial for the success and functionality of such implants. The aim of this study was to characterise an interference screw fixation system developed for a novel fibre-matrix-reinforced synthetic total meniscus replacement in an ovine cadaveric model.

Methods: Textile straps were tested in tension to failure (n = 15) and in cyclic tension (70-220 N) for 1000 cycles (n = 5). The textile strap-interference screw fixation system was tested in 4.5 mm-diameter single anterior and double posterior tunnels in North of England Mule ovine tibias aged > 2 years using titanium alloy (Ti6Al4Va) and polyether-ether-ketone (PEEK) screws (n ≥ 5). Straps were preconditioned, dynamically loaded for 1000 cycles in tension (70-220 N), the fixation slippage under cyclic loading was measured, and then pulled to failure.

Results: Strap stiffness was at least 12 times that recorded for human meniscal roots. Strap creep strain at the maximum load (220 N) was 0.005 following 1000 cycles. For all tunnels, pull-out failure resulted from textile strap slippage or bone fracture rather than strap rupture, which demonstrated that the textile strap was comparatively stronger than the interference screw fixation system. Pull-out load (anterior 544 ± 119 N; posterior 889 ± 157 N) was comparable to human meniscal root strength. Fixation slippage was within the acceptable range for anterior cruciate ligament graft reconstruction (anterior 1.9 ± 0.7 mm; posterior 1.9 ± 0.5 mm).

Conclusion: These findings show that the textile attachment-interference screw fixation system provides reliable fixation for a novel ovine meniscus implant, supporting progression to in vivo testing. This research provides a baseline for future development of novel human meniscus replacements, in relation to attachment design and fixation methods. The data suggest that surgical techniques familiar from ligament reconstruction may be used for the fixation of clinical meniscal prostheses.