Knotless anchor fixation for transosseous meniscus root repair using suture tape is inferior compared to button and screw fixation: a biomechanical study

Background: 2 mm wide Ultra-High-Molecular-Weight-Polyethylene (UHMWPE) tape improves contact pressure at root repair sites compared to high strength suture and provides stronger repair construct. UHMWPE tape is commonly used in rotator cuff repair and fixation is often achieved with knotless suture anchors. For meniscal root repair the optimal method for tape fixation has not been established.
Purpose: We hypothesised that the use of suture anchors for the tibial fixation of 2 mm UHMWPE tape trans-osseous root repairs would lead to better biomechanical performance compared to other fixation methods.
Methods: In 25 porcine knees the medial meniscus posterior root attachment was divided, a standardised trans-tibial root repair performed with 2 mm UHMWPE tape and testing performed by cyclic loading followed by load to failure. Tibial fixation was randomised to 5 tibial fixation types: i) Cortical Fixation Button, ii) Pound-in Suture Anchor with screw down interference suture locking iii) Tap-in Suture Anchor with inner locking plug iv) Post Screw v) Post Screw and Washer.
Results: There was not difference in displacement during cyclic loading between tibial fixation groups, but a highly significant difference in the max. load at failure. Repairs in both suture anchor fixation groups all failed by tape slippage at relatively low loads (median 145 N and 116 N) respectively. Repairs tied over a cortical button, post screw or screw and washer failed by tape breakage at loads of 421 N, 405 N and 531 N.
Conclusion: For meniscal root repairs with 2 mm UHWMPE tape, use of suture anchors offers weaker fixation compared to tying over a button or post screw/washer. Whilst suture anchor fixation may be adequate for non-weight bearing post-operative protocols it may not allow for more accelerated weight bearing.
Keywords: Tibial fixation; Knotless anchors; Mechanical testing; Failure load; Meniscus root repair