Age influence on resistance and deformation of the human sutured meniscal horn in the immediate postoperative period

Abstract

Introduction: To preserve knee function, surgical repair is indicated when a meniscal root disinsertion occurs. However, this surgery has not yet achieved complete recovery of the joint´s natural biomechanics, with the meniscus-suture interface identified as a potentially determining factor. Knowing the deformation and resistance behavior of the sutured meniscal horn and whether these properties are preserved as the patient ages could greatly contribute to improving repair outcomes. Methods: A cadaveric experimental study was conducted on human sutured menisci classified into three n = 22 age groups (young ≤55; 55 < middle-aged ≤75; 75 < old) were subjected to load-to-failure test by suture pulling. Meniscal thickness at the suture hole was measured and the applied traction force and tissue deformation in the suture area in the direction of traction were recorded during the test. The traction load that initiated the meniscal cut-out, $F_c$, maximum load borne by the meniscus, $F_u$, tissue stress at the cut-out initiation, $S_c$, and equivalent stiffness modulus at the suture area, $m_s$, were calculated. Results: At the tissue level, the resistance in terms of $S_c$ decrease with age (young: 47.2 MPa; middle-aged: 44.7 MPa; old: 33.8 MPa) being significantly different between the young and the old group (p = 0.015). Mean meniscal thickness increased with age (young: 2.50 mm; middle-aged: 2.92 mm; old: 3.38 mm; p = 0.001). Probably due to thickening, no differences in resistance were found at the specimen level, i.e., in $F_c$ (overall mean 58.2 N) and $F_u$ (overall mean 73.6 N). As for elasticity, $m_s$ was lower in the old group than in the young group (57.5 MPa vs. 113.6 MPa, p = 0.02) and the middle-aged one (57.5 MPa vs. 108.0 MPa, p = 0.04). Conclusion: Regarding the influence of age on the sutured meniscal horn tissue, in vitro experimentation revealed that meniscal horn specimens older than 75 years old had a more elastic tissue which was less resistant to cut-out than younger menisci at the suture hole area. However, a thickening of the meniscal horns with age, which was also found, leveled out the difference in the force that initiated the tear, as well as in the maximum force borne by the meniscus in the load-to-failure test.

Keywords: age influence; human meniscal tissue; meniscal root detachment; suture; tissue resistance.

FIGURE 1

Sutured meniscus with N°2 non-absorbable, high resistance, 100% UHMWPE, braided fiber thread at 5 mm from its internal edge and its root junction. Marks are shown in an intact specimen that was discarded for not meeting the inclusion criterion.

FIGURE 2

Uniaxial traction/compression testing machine: 1) load cell; 2) mechanical clamp to secure the suture free ends; 3) clamp with three orthogonal rotational degrees of freedom; 4) linear positioning table with two orthogonal linear degrees of freedom.

FIGURE 3

Experimental setup. Mark1 and Mark2 on the surface of one meniscus specimen can be observed.

FIGURE 4

Mean (numerical value in each column) and SD of the thickness of the meniscal horns at the suture hole area: (A) for each age group; (B) for each age group at the lateral and medial location. For the groups with significant differences, the percentage difference between means with respect to the oldest group is indicated. Significant difference: *Young vs. Old.

FIGURE 5

Mean (numerical value in each column) and SD of mechanical properties of the meniscal horns for each age group: (A) cut-out force (B) ultimate force (C) cut-out resistance (D) equivalent stiffness modulus. For the groups with significant differences, the percentage difference between means with respect to the oldest group is indicated. Significant difference: *Young vs. Old; ^& Middle-aged vs. Old.

FIGURE 6

Mean (numeric value in each column) and SD of mechanical properties of the lateral and medial meniscal horns for each age group: (A) cut-out force; (B) ultimate force (C) cut-out resistance (D) equivalent stiffness modulus. For the groups with significant differences, the percentage difference between means with respect to the oldest group is indicated. Significant difference: *Young vs. Old; ^& Middle-aged vs. Old.