Biomechanical Performance of Transtibial Pull-Out Posterior Horn Medial Meniscus Root Repair Is Improved With Knotless Adjustable Suture Anchor-Based Fixation

Abstract

Background: While posterior medial meniscus root (PMMR) techniques have evolved, there remains a need to both optimize repair strength and improve resistance to cyclic loading.

Hypothesis: Adjustable tensioning would lead to higher initial repair strength and reduce displacement with cyclic loading compared with previously described transtibial pull-out repair (TPOR) fixation techniques.

Study design: Controlled laboratory study.

Methods: A total of 56 porcine medial menisci were used. Eight intact specimens served as a control for the native meniscus. For the others, PMMR tears were created and repaired with 6 different TPOR techniques (8 in each group). Fixed PMMR repairs were executed using 4 different suture techniques (two No. 2 cinch sutures, two cinch tapes, two No. 2 simple sutures, and two No. 2 sutures in a Mason-Allen configuration) all tied over a cortical button. Adjustable PMMR repairs using Mason-Allen sutures were fixed with an adjustable soft tissue anchor fixation tensioned at either 80 N or 120 N. The initial force, stiffness, and relief displacement of the repairs were measured after fixation. Repair constructs were then cyclically loaded, with cyclic displacement and stiffness measured after 1000 cycles. Finally, the specimens were pulled to failure.

Results: The PMMR repaired with the 2 cinch sutures fixed technique afforded the lowest (P < .001) initial repair load, stiffness, and relief displacement. The adjustable PMMR repairs achieved a higher initial repair load (P < .001) and relief displacement (P < .001) than all fixed repairs. The 2 cinch sutures fixed technique showed an overall higher cyclic displacement (P < .028) and was completely loose compared with the native meniscus functional zone. Repairs with adjustable intratunnel fixation showed displacement with cyclic loading similar to the native meniscus. With cyclic loading, the Mason-Allen adjustable repair with 120 N of tension showed less displacement (P < .016) than all fixed repairs and a stiffness comparable to the fixed Mason-Allen repair. The fixed Mason-Allen technique demonstrated a higher ultimate load (P < .007) than the adjustable Mason-Allen techniques. All repairs were less stiff, with lower ultimate failure loads, than the native meniscus root attachment (P < .0001).

Conclusion: Adjustable TPOR led to considerably higher initial repair load and relief displacement than other conventional fixed repairs and restricted cyclic displacement to match the native meniscus function. However, the ultimate failure load of the adjustable devices was lower than that of a Mason-Allen construct tied over a cortical button. All repair techniques had a significantly lower load to failure than the native meniscus root.

Clinical relevance: Knotless adjustable PMMR repair based on soft anchor fixation results in higher tissue compression and less displacement, but the overall clinical significance on healing rates remains unclear.

Keywords: adjustable pull-out repair; biomechanics of ligament; knee; meniscus; meniscus root; root tear.

Figure 1.

(A-D) Various fixed groups and (E) the adjustable suture repair groups (2 groups), with testing algorithm and outcome variables. A, anchor fixation; MA, Mason-Allen; TCL, 2 cinch loops; TCS, 2 cinch sutures; TS, 2 sutures.

Figure 2.

(A) The adjustable implant with (B-I) stepwise surgical preparation of the adjustable Mason-Allen root repair (shown with intact medial tibial plateau).

Figure 3.

Biomechanical setup for (A) primary fixation of the transtibial pull-out meniscus root repair in line with the actuator axis and for (B) cyclic testing with load applied in alignment with the circumferential fibers of the meniscus.

Figure 4.

Initial repair load and corresponding relief displacement to reach the time-zero valley position (2-N load on the repair) with statistical analysis (different shaded backgrounds indicate statistical significance levels) and percentage deviation between adjustable and fixed Mason-Allen repair (asterisks with italic values). MA, Mason-Allen; TCL, 2 cinch loops; TCS, 2 cinch sutures; TS, 2 sutures.

Figure 5.

Displacement after 1000 load cycles with statistical analysis (different shaded backgrounds indicate statistical significance levels) and percentage deviation of adjustable to the fixed Mason-Allen group (asterisks with italic values). MA, Mason-Allen; TCL, 2 cinch loops; TCS, 2 cinch sutures; TS, 2 sutures.

Figure 6.

Representative hysteresis curves of various suture- and cinch-based repair groups at the end of testing (cycle 1000) illustrating the final loading situation of the adjustable and fixed repairs in reference to the native meniscus. MA, Mason-Allen; TCL, 2 cinch loops; TCS, 2 cinch sutures; TS, 2 sutures.

Figure 7.

Mean and standard deviation values of the ultimate load during pull to failure with percentage deviation of adjustable to the fixed Mason-Allen group (asterisks with italic values). Different shaded backgrounds indicate statistical significance differences. MA, Mason-Allen; TCL, 2 cinch loops; TCS, 2 cinch sutures; TS, 2 sutures.