## 2 Materials and Methods
### Biomechanical Testing  
A single-axis testing machine (Figure 1), specially designed for biomechanical tests [46], was used to subject the sutured meniscus to a load-to-failure test. Three orthogonal axes are defined in the testing machine, with the \(z\)-axis coinciding with the servomotor screw that sets the direction of traction (Figure 1). The suture-meniscus set was placed in the testing machine in two phases. First, the meniscus was fixed with a clamp at approximately 8 mm from the suture point, using sandpaper surrounding the clamping area to increase friction. The meniscus was carefully oriented with the cranial surface facing the outer side of the testing machine, the longitudinal fibers of the horn were aligned to the loading direction, and the suture hole was centered with the actuator head in the loading direction. Second, the two free ends of the suture were also wrapped in sandpaper and attached to a mechanical clamp on the machine head, with 55 mm between the puncture point and the limit of the clamp when the suture is pulled manually, with just enough traction to keep it vertical. Fifty-five millimeters were selected as representative of the expected suture length in a transtibial meniscal horn repair [14; 47]. An electronic inclinometer (Bubble Level 3D, v. 2.2.4, Maleirbag, 2022, Puebla, Mexico, installed on the smartphone M2002F4 LG, Xiaomi, Beijing, China) was used to orient the meniscus so that its cranial and caudal surfaces were within the plane defined by the \(z\)-axis (traction direction) and the \(y\)-axis (transverse direction) of the testing machine as close as possible. Once the meniscus-suture set had been placed on the testing machine, two ink points were marked with a surgical pen on the cranial side. Aided by the inclinometer to identify the direction of traction on the meniscal surface, the points were located along a line in that direction passing through the suture hole: Point1 on the suture limb coincident with the meniscus-suture interface; and Point2 on the opposite side of the hole in its immediate surroundings (Figure 2). These marks were used for videogrammetric analysis of the displacements around the hole in the direction of traction.  
The servo controller of the testing machine (SGDH-15 AE-S-OY, Yaskawa Electric, Fukuoka, Japan) recorded the actuator displacement in the pull direction, and a 2000 N  
Figure 1: Uniaxial testing machine and the videogrammetric system: (1) digital camera; (2) load cell; (3) clamp on the head of the testing machine to fix the suture; (4) clamp on the base of the testing machine to fix the meniscus.  
Figure 2: (**a**) Meniscus specimen on the testing machine. The marks for videogrammetric tracking can be observed. (**b**) Detail of the suture hole area.  
load cell of accuracy class 0.1 (U2B, HBM, Darmstadt, Germany) registered the applied traction force. Both signals were sampled at 1000 Hz. For videogrammetric analysis, a digital camera (VCXU-124C, Baumer, Frauenfeld, Switzerland) (Figure 1), synchronized with the sensors of the testing machine, was placed facing the cranial surface of the meniscus. For this purpose, the camera was mounted on a tripod (808 RC4, [PERSON], Cassola, Italy) featuring three rotating orthogonal mechanisms (Figure 1), and, using the electronic inclinometer, it was positioned to align its image plane with the plane containing the \(z\) and \(y\) axes of the testing machine, i.e., approximately parallel to the mid transverse plane of the meniscus. The camera was equipped with a 2.8/75 mm lens (C7528-M, Pentax, Tokyo, Japan). Images were acquired with a 250 ms sampling period.  
The sutured meniscus was initially pulled to 1 N at 0.05 mm/s, held at this load level for 5 s to allow the specimen to stabilize, and then subjected to a displacement-controlled load-to-failure test at 0.1 mm/s.