Poster 286: Biomechanical Analysis Evaluating Meniscal Extrusion Following Knotless Suture Anchor Fixation for Segmental Medial Meniscus Allograft Transplantation

OBJECTIVES: Segmental medial meniscus allograft transplantation (MAT) has been shown to restore knee biomechanics, however, stable fixation of the transplant is critical to avoid extrusion and maximize healing. The purpose of this study was to evaluate the degree of meniscal extrusion and biomechanical function of segmental MAT performed with meniscocapsular sutures versus repair augmentation with knotless suture anchors. METHODS: Ten fresh frozen cadaveric knees underwent central midbody medial meniscectomy (15-mm defect) and subsequently segmental medial MAT. Knees were loaded in a dynamic tensile testing machine to 1000 N for 20 seconds at 0°, 30°, 60°, and 90° of flexion. Four conditions were tested: (1) intact, (2) segmental defect, (3) inside-out segmental repair, and (4) anchors plus inside-out segmental repair of the MAT. Meniscal extrusion was measured for each test state using high-fidelity ultrasound imaging by three independent observers. Submeniscal medial and lateral pressure-mapping sensors assessed the mean contact pressure, peak contact pressure, mean contact area, and pressure mapping. Assessment of inter- and intraobserver reliability of measurements were done using intraclass correlation coefficients. A two-way repeated measures ANOVA was computed in order to evaluate whether there is a significant interaction between meniscal states and knee flexion angles on the outcome variables. If the P value was ≤ 0.05, a pairwise comparison of the means was determined using the Bonferroni method. RESULTS: At 0° of knee flexion, the segmental defect demonstrated the statistically significant higher degree of meniscal extrusion (2.08 mm ± 0.78 mm) compared with intact (1.02 mm ± 0.86 mm, P = 0.039) and anchor plus inside-out segmental repair (1.44 mm ± 0.76 mm, P = 0.044), but not for an inside-out segmental repair (1.55 mm ± 0.49 mm, P = 0.08). The segmental defect state also showed a higher degree of meniscal extrusion compared with all other states at 90° of knee flexion (P < 0.01). There was no difference in the degree of meniscal extrusion between the intact state and the inside-out repair or anchor plus inside-out segmental repair in all knee flexion angles (P > 0.05). Three observers showed good-to-strong intra-rater and moderate-to-strong inter-rater reliabilities for extrusion measurements. There was no significant difference in the mean contact pressure and peak contact pressure among four states in all knee flexion angles for both medial and lateral compartments except for that at 0° of knee flexion, there was a significantly lower peak pressure at the medial compartment after anchor plus inside-out segmental repair compared with the segmental defect state (P = 0.048). The medial contact area of the intact state was significantly higher than the other states at 0° of knee flexion (P < 0.05). However, the lateral contact area after anchor plus inside-out repair showed no significant difference compared with the intact state (P = 0.13). CONCLUSIONS: Segmental meniscus transplantation mechanics may be improved at full extension (0° of knee flexion) with the addition of knotless anchors. However, in terms of meniscus extrusion, the knotless anchors provided limited benefit over inside-out repair. Overall, a robust repair is achieved of a segmental meniscus with sutures and knotless anchors. Although, additional work is needed to assess long-term in vivo results.