Objective To make biomechanical evaluation on ultimate pullout strength of the suture anchors based on the angle of suture anchor (SA) implanted into the humerus during arthroscopic rotator cuff repair (RCR) surgery. Methods Polyurethane materials with densities of 0.16 g/cm3 and 0.32 g/cm3 were used to simulate osteoporosis and normal cancellous bone, and polyurethane materials with densities of 0.64 g/cm3 and 3 mm thickness were used to simulate human cortical bone. The two kinds of cancellous bone models were respectively adhered together with cortical bone model to construct human humerus model. Titanium metal suture anchors were inserted into humerus models at 45°, 60°, 75° and 90° angle, then the continuous tensile experiments were performed, and 45° pulling direction between the humerus model surface and suture anchor was used to simulate the supraspinatus physiological traction direction, and each group was continuously tested 8 times, recording the pullout strength and failure modes. ResultsThe pullout force of high-density bone models was significantly higher than that of low-density bone models (P＜0.001), and at the same density, compared with 45°, 60° and 75°, the implant angle of 90° has a larger pullout force (P＜0.01). Conclusions In the model of humerus, the 90° implantation of suture anchor showed better biomechanical properties, and the vertical implantation of anchor in the repair of rotator cuff was beneficial to the knotting during operation and postoperative recovery of the supraspinatus.

Objective To explore the influence of hook deflection angle and inclination angle on mechanical properties of the soft tissue suture passer hook. Methods Taking the end face far away from the tip of the needle (end face 1) as the study object, a mathematical model was established with the moment as dependent variable and the hook deflection angle and inclination angle as the independent variable. The moment was solved by the mathematical model with the deflection angle and inclination angle of 0°, 10°, 20° and 30°. Based on the finite element analysis method, 16 three-dimensional geometric hook models with deflection angle and inclination angle of 0°, 10°, 20° and 30° were established by SolidWorks. The stress analysis was carried out by ANSYS Workbench. Under the same puncture force, the maximum von Mises stress of each hook and the reaction moment of end face far away from the tip of the needle were calculated. Results The results from theoretical analysis and numerical simulation showed that the reaction moment of end face 1 increased with the increase of deflection angle, and increased with the decrease of inclination angle. The hook with deflection angle of 0° and inclination angle of 30° had the minimum reaction moment. The finite element analysis results showed that with the deflection angle of 0°, the maximum von Mises stress of the hook was the smallest and did not change with the inclination angle of the hook changing. Conclusions The established mathematical model can accurately explain the relationship between the moment at the end face of the hook and the deflection angle and inclination angle of the hook. This study provides the theoretical basis for designing hook geometry of the soft tissue suture passer, and improves the safety of the soft tissue suture passer in operation process.