Poster 123: Biomechanical Comparison of Four All-inside Meniscus-Based Repairs to Radial Tears of Human Cadaveric Lateral Menisci

OBJECTIVES: Meniscal injuries are among the most common orthopedic injuries in the United States. Radial meniscus tears were historically treated with partial meniscectomy, often leading to poor outcomes. Radial tear repair preserves meniscal tissue, may delay knee degeneration, and leads to better long-term outcomes. Repair techniques for radial tears vary and should be evaluated for differences in biomechanical properties and failure mechanisms. All-inside, meniscus-based suture repairs have shorter operating times, minimize risk of nerve injury, and are increasingly possible with novel devices. Our objective was to evaluate the strength based on load-to-failure of four all-inside meniscus-based repair techniques for radial tears in human cadaveric lateral menisci. We chose two techniques that bridged the tear directly – the Double Vertical (DV, Figure 1) and Double Vertical Cross (DVX, Figure 2). We chose two other techniques that added horizontal reinforcing stitches to engage the bridging stitches – the All-inside Rebar (AR, Figure 3) and our novel Oblique Box (OB, Figure 4). We hypothesized that AR and OB would have higher load to failure than DV and DVX. METHODS: 36 fresh-frozen human adult lateral menisci were randomized into four groups of nine. Dissection, repair, and testing were completed one meniscus at a time to minimize the time period from thawing to testing. Each meniscus was dissected from its tibial bone block, and a complete radial tear was created at the midbody of the meniscus. Suture repairs were performed using 2-0 braided suture and a straight needle. Menisci were repaired using the DV, DVX, AR, and OB techniques with meniscus- based suturing to simulate the all-inside, meniscus-based approach. All suture dimensions were standardized as indicated on Figures 1-4, and all knots were tied on the superior surface of the menisci. The suture patterns for all repair types used loops that passed above the superior and below the inferior surfaces of the meniscus. The DV repair used two sutures in loops perpendicular to the tear. DVX used two sutures in loops that crossed over the tear. AR used two sutures in loops parallel to the tear acting as reinforcing rebar and two bridging sutures perpendicular to the tear and outside the rebar sutures. OB used two sutures to create a trapezoidal reinforcing box on either side of the tear and two bridging sutures in loops perpendicular to the tear and inside the box. The repaired menisci were loaded on an Instron 5944 test frame with 2 kN load cell using custom clamps. They underwent cyclic loading of 5-30 N for 500 cycles at 10 mm/min, a 30-minute resting period, and a single trial of load-to-failure at 10 mm/min. The ultimate load at failure was analyzed via one-way ANOVA with Tukey’s test for pairwise comparisons and significance set at p<0.05. RESULTS: Failure occurred due to suture cutout in all specimens. Repair constructs that lacked a reinforcing-type suture (DV and DVX) cut through or “cheese-wired” at lower loads than repairs with reinforcing sutures (AR and OB). Mean ± standard deviation ultimate load values for each repair group were 60 N ± 24.5 for DV, 58 N ± 17.4 for DVX, 168 N ± 33.9 for AR, and 105 N ± 9.0 for OB. The ultimate load for all repair techniques were significantly different from each other by Tukey’s test with the exception of the DV and DVX comparison. These results show that reinforcing vertical suture meniscus repairs with some type of horizontal suture (e.g. AR or OB) significantly increases ultimate load at failure for all-inside, meniscus-based techniques. CONCLUSIONS: In a cadaveric lateral meniscus model, all-inside radial repairs using rebar suture, or horizontal suture reinforcing techniques, had higher ultimate load at failure and reduced risk of “cheese wiring”. The AR repair sustained the highest ultimate load at failure, nearly 3x stronger than the two non-reinforcing type repair constructs. These data may provide useful information for surgeons during repair to radial meniscus tears. Future biomechanical study should compare all-inside vs. inside-out repairs to maximize patient outcomes. Cross reference of repair patterns with clinical outcomes using the prospective registry data may support optimal surgical techniques to improve meniscus repair outcomes.