Optimized design of an enthesis-mimicking suture anchor-tendon hybrid graft for mechanically robust bone-tendon repair
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AbstractRepair of functionally graded biological interfaces requires joining dissimilar materials such as hard bone to soft tendon/ligament, with re-injuries/re-tears expected to be minimized by incorporating biomimick- ing, stress-reducing features within grafts. At bone-tendon interfaces (entheses), stress can be reduced via angled insertion, geometric flaring, mechanical gradation, and interdigitation of tissues. Here, we incor- porated enthesis attributes into 3D in silico and physical models of a unique suture anchor-tendon hybrid graft (SATHG) and investigated their effects on stress reduction via finite element analyses (FEA) studies. Over 20 different simulations altering SATHG angulation, flaring, mechanical gradation, and interdigitation identified an optimal design, which included 90 °angulation, 25 °flaring, and a compliant (ascending then descending) mechanical gradient in SATHG’s bone-to-tendon-like transitional region. This design reduced peak stress concentration factor (SCF) by 43.6 % relative to an ascending-only mechanical gradient typi- cally used in hard-to-soft tissue engineering. To verify FEA results, SATHG models were fabricated using a photocrosslinkable bone-tendon-like polyurethane (QHM polymer) for ex vivo tensile assessment. Tensile testing showed that ultimate load (132.9 N), displacement-at-failure (1.78 mm), stiffness (135.4 N/mm), and total work-to-failure (422.1 ×10−3 J) were highest in the optimized design. Furthermore, to assess envisioned usage, SATHG pull-out testing and 6-week in vivo implantation into large, 0.5-cm segmen- tal supraspinatus tendon defects was performed. SATHG pull-out testing showed secure bone attachment while histological assessment such as hematoxylin and eosin (H&E) together with Safranin-O staining showed biocompatibility including enthesis regeneration. This work demonstrates that engineering bio- materials with FEA-optimized, enthesis-like attributes shows potential for enhancing hard-to-soft tissue repair.
Acceptance Date09/01/2024
All Author(s) ListChenyang Wang, Xu Zhang, Dan Michelle Wang, Patrick S H Yung, Rocky S Tuan, Dai Fei Elmer Ker
Journal nameActa Biomaterialia
Year2024
Month3
Volume Number176
PublisherElsevier
Pages277 - 292
ISSN1742-7061
LanguagesEnglish-United States
KeywordsFinite element analysis, Scaffold design optimization, Modeling, Bone-tendon Scaffold, Rotator cuff repair, Musculoskeletal tissue engineering
