## 4 Discussion
The pitches of the microthreads were 0.8 and 0.7 mm (Figure 2 (UP)), with reference to the optimal value reported by [PERSON] et al., and the contact areas of the cortical-to-implant surface in the conical part were 22.8 and 25.02 mm\({}^{2}\)[34]. However, the dimension and morphologies of our suture anchor design and dental cylindrical implant differed considerably; thus, the effects of the aforementioned reference values were considered in two levels for simplification in this study. The lower stress value on both the suture anchor and upper bone stress was observed in the 0.7 mm group (Tables 4-7); this level also exhibited the higher pullout strength in the displacement-controlled simulation (Tables 2 and 3), which indicated that the smaller microthread pitch was preferred in this case. The main purpose of rotator cuff repair is to attach injured soft tissue to the bone surface and to provide sufficient stability against the cyclic loading of anchor removal during mobilization for enhanced tissue healing. Relevant studies have examined other factors involved in rotator cuff repair failure, such as fixation strength, suture methods, bone quality, and implant location. We proposed a suture anchor design with favorable stress distribution and acceptable numerical analysis results; in vivo biomechanical tests are necessary to examine the complete functions of this suture anchor design in rotator cuff repair. This study has some limitations. First, the difference between in vitro testing and real-world suture anchor usage should be noted. Simple assumptions, including axial upward removal loading and material properties, such as Poisson's ratio, the constant which we assigned to the materials was based on the assumption that all materials were isotropic, can limit the complexity of FEA; as a trade-off, this simplification fails to provide sufficient evaluation in the living tissue environment in terms of osseointegration and physiological reactions. Furthermore, the mechanical properties of Mg-based metallic glass, a novel material, differed to some extent from those used in this FEA. In this study, the main differences between the two types of test blocks were density and Young's modulus. As the density decreased, the total volume of the test block that could withstand the pullout force of the suture anchor also decreased, which resulted in the suture anchor being released more easily. The low Young's modulus, indicating a higher likelihood of material yielding, is another factor that contributed to the marked difference in pullout strength between the 10- and 20-PCF groups. Notably, in both the mechanical tests and FEA, the ratio of the pullout strength of the 20-PCF group to that of the 10-PCF group was approximately 4, although there was ignorable deviation between pullout strengths measured in two methods, indicating that our FEA can provide a reliable prediction of the mechanical behavior of the suture anchor. For two testing methods, the strength in the osteoporotic bone was compared with testing in normal bone as the control group. The main purpose of this study was to assess the effects of various combinations of distinctive parameters through FEA. The parametrical comparison of simulation results might optimize the fixation strength of the new anchor in its future clinical application. Further studies will compare with conventional anchors made of titanium and biocomposite materials to understand the influence of different materials. Researchers have indicated the importance of bone mass regeneration in rotator cuff repair [35]. Second, loading conditions applied in mechanical tests cannot represent real-world loading conditions. Because of shoulder joint motions and the arrangement of tendons, an upward axial removal force appears to be desirable; thus, this procedure is regarded as a standard approach for testing suture anchors. Various loading angles should be considered in future studies.