en عمومى General نامه به سردبیر Letter to editor <br> <div dir="ltr" style="text-align: justify;"></div><div dir="ltr" style="text-align: justify;"></div> <span style="line-height:1;"><span style="font-family:Times New Roman;"><span style="font-size:12pt"><span aptos="">Dear Editor</span></span></span><br> <span style="font-size:11pt"><span style="unicode-bidi:embed"><span calibri=""><span new="" roman="" times="">I read with great interest the recent article by Qin et al. introducing a two-stage metamaterial scaffold (TMS) that decouples strength and modulus, achieving an effective stiffness of only 13 MPa while retaining sufficient load-bearing capacity.<u>^[1]</u> By enabling >2 % callus strain <i>in vivo</i>, the TMS activated mechanosensitive calcium channels and HIF-1&alpha; signaling, thereby enhancing both osteogenesis and angiogenesis. This work challenges the conventional &ldquo;modulus-matching&rdquo; paradigm by highlighting mechanical strain as a key driver of bone regeneration.<br> While the compressive behavior of the TMS is well-characterized, two critical aspects require further clarification. First, many skeletal sites are subject to complex tensile and shear forces, which bone scaffolds must withstand to maintain functionality in physiological conditions; however, the performance of TMS under such loading modes remains unexplored.<u>^[2]</u> Second, long-term <i>in vivo</i> studies are essential to evaluate fatigue resistance, remodeling dynamics, and potential late-stage stress shielding.<u>^[3]</u> Previous reports have shown that functionally graded designs can improve fatigue life by up to 30%.<u>^[4]</u> In addition, patient-specific finite element (FE) modeling could further optimize strain-targeted scaffold designs by predicting callus strain distribution under realistic physiological loading, as demonstrated in fibular healing studies where case-specific FE models incorporating anatomical geometry significantly improved the accuracy of strain and stress distribution predictions.<u>^[5]</u><br> By addressing these points, the TMS approach could be better positioned for translational success. Overall, this study represents a significant step toward strain-optimized scaffold design and provides a valuable foundation for next-generation orthopedic implants.</span></span></span></span><br> &nbsp;</span> Metamaterial, Scaffold, orthopedic implants 94 95 http://umj.umsu.ac.ir/browse.php?a_code=A-10-5908-1&slc_lang=en&sid=1 Erkan Karatas erkan.karatas@erzurum.edu.tr 3700319475328460038023 3700319475328460038023 Yes Erzurum Technical University, Erzurum 25100, Turkiye