Primary Fixation and Cyclic Performance of Posterior Horn Medial Meniscus Root Repair With Knotless Adjustable Suture Anchor-Based Fixation: A Human Biomechanical Evaluation Over 100,000 Loading Cycles.

Background: Recent biomechanical evidence for adjustable suture anchor (ASA)-based posterior medial meniscus root (PMMR) fixation has shown promising results compared with conventional transtibial pull-out repair (TPOR). However, ASA fixation has not been evaluated in human tissue to 100,000 cycles.

Hypothesis: ASA repair would lead to increased primary fixation strength and less cyclic displacement than conventional TPORs.

Study design: Controlled laboratory study.

Methods: A total of 32 human medial menisci were used, 8 of which were intact specimens and served as native controls. For the others, PMMR tears were created and repaired using 3 different techniques (n = 8 group). Two conventional PMMR repairs were prepared consisting of two No. 2 simple sutures (TSS) and two No. 2 sutures in a Mason-Allen (MA) configuration, all tied over a cortical button. The knotless ASA repair was fixed in MA with repair sutures tensioned at 120 N (MA-120). The repairs' initial force, stiffness, and relief displacement from the tensioned state toward repair unloading (2 N) were measured after fixation. All repair constructs were loaded for 100,000 cycles, with displacement and stiffness measured, and finally were pulled to failure.

Results: The TPORs demonstrated similar primary fixation and cyclic loading behavior except for initial cyclic displacement (cycle 10). The ASA repair provided a higher initial repair load (P < .001) and stiffness (P < .001) with relief displacement similar to conventional TPORs. Lower initial cyclic displacement (P < .011; cycle 10) with overall higher repair stiffness (P < .011) resulted in significantly lower displacement (P < .001) throughout testing for ASA repair. Although both TPORs were completely loose after 100,000 cycles, the ASA repair achieved near-native dynamic meniscal stabilization. The TSS repair had lower overall ultimate load (P < .001) and ultimate stiffness (P < .023) compared with the ASA repair. All repairs had lower ultimate stiffness and loads than the native meniscus (P < .001).

Conclusion: The ASA repair resulted in improved primary PMMR fixation that was stiffer with less cyclic displacement than conventional TPORs and approached that of the human meniscal function after 100,000 load cycles in a cadaveric model. However, all repair techniques had lower ultimate strength than the native human PMMR.

Clinical relevance: Knotless ASA meniscus root fixation resulted in higher tissue compression and less displacement in a cadaveric model; however, future clinical series with surveillance imaging will define the overall significance of healing rates.