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Wang C, Zhang X, Wang DM, Yung PSH, Tuan RS, Ker DFE. Optimized design of an enthesis-mimicking suture anchor-tendon hybrid graft for mechanically robust bone-tendon repair. Acta Biomater 2024; 176:277-292. [PMID: 38244656 DOI: 10.1016/j.actbio.2024.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 11/22/2023] [Accepted: 01/09/2024] [Indexed: 01/22/2024]
Abstract
Repair 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 biomimicking, 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 incorporated 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 typically 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 segmental 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 biomaterials with FEA-optimized, enthesis-like attributes shows potential for enhancing hard-to-soft tissue repair. STATEMENT OF SIGNIFICANCE: Successful repair of hard-to-soft tissue injuries is challenging due to high stress concentrations within bone-tendon/ligament grafts that mechanically compromise repair strength. While stress-reducing gradient biomaterials have been reported, little-to-no attention has focused on other bone-tendon/ligament interface (enthesis) features. To this end, a unique bone-tendon graft (SATHG) was developed by combining two common orthopaedic devices along with biomimetic incorporation of four enthesis-like features to reduce stress and encourage widespread clinician adoption. Notably, utilizing designs based on natural stress dissipation principles such as anchor insertion angle, geometric flaring, and mechanical gradation reduced stress by 43.6 % in silico, which was confirmed ex vivo, while in vivo studies showed SATHG's ability to support native enthesis regeneration. Thus, SATHG shows promise for hard-to-soft tissue repairs.
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Affiliation(s)
- Chenyang Wang
- Institute for Tissue Engineering and Regenerative Medicine, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; School of Biomedical Sciences, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR
| | - Xu Zhang
- Institute for Tissue Engineering and Regenerative Medicine, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; School of Biomedical Sciences, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; Center for Neuromusculoskeletal Restorative Medicine, InnoHK, Hong Kong Science Park, Hong Kong SAR
| | - Dan Michelle Wang
- Institute for Tissue Engineering and Regenerative Medicine, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; School of Biomedical Sciences, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; Ministry of Education Key Laboratory for Regenerative Medicine, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; Center for Neuromusculoskeletal Restorative Medicine, InnoHK, Hong Kong Science Park, Hong Kong SAR; Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Lui Che Woo Clinical Science Building, Prince of Wales Hospital, Hong Kong SAR
| | - Patrick S H Yung
- Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Lui Che Woo Clinical Science Building, Prince of Wales Hospital, Hong Kong SAR; Center for Neuromusculoskeletal Restorative Medicine, InnoHK, Hong Kong Science Park, Hong Kong SAR; Institute for Tissue Engineering and Regenerative Medicine, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR
| | - Rocky S Tuan
- Institute for Tissue Engineering and Regenerative Medicine, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; School of Biomedical Sciences, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; Center for Neuromusculoskeletal Restorative Medicine, InnoHK, Hong Kong Science Park, Hong Kong SAR; Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Lui Che Woo Clinical Science Building, Prince of Wales Hospital, Hong Kong SAR
| | - Dai Fei Elmer Ker
- Institute for Tissue Engineering and Regenerative Medicine, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; School of Biomedical Sciences, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; Ministry of Education Key Laboratory for Regenerative Medicine, Lo Kwee-Seong Biomedical Sciences Building, Area 39, The Chinese University of Hong Kong, Hong Kong SAR; Center for Neuromusculoskeletal Restorative Medicine, InnoHK, Hong Kong Science Park, Hong Kong SAR; Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Lui Che Woo Clinical Science Building, Prince of Wales Hospital, Hong Kong SAR.
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Ker DFE, Wang D, Behn AW, Wang ETH, Zhang X, Zhou BY, Mercado-Pagán ÁE, Kim S, Kleimeyer J, Gharaibeh B, Shanjani Y, Nelson D, Safran M, Cheung E, Campbell P, Yang YP. Functionally Graded, Bone- and Tendon-Like Polyurethane for Rotator Cuff Repair. ADVANCED FUNCTIONAL MATERIALS 2018; 28:1707107. [PMID: 29785178 PMCID: PMC5959293 DOI: 10.1002/adfm.201707107] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Indexed: 05/25/2023]
Abstract
Critical considerations in engineering biomaterials for rotator cuff repair include bone-tendon-like mechanical properties to support physiological loading and biophysicochemical attributes that stabilize the repair site over the long-term. In this study, UV-crosslinkable polyurethane based on quadrol (Q), hexamethylene diisocyante (H), and methacrylic anhydride (M; QHM polymers), which are free of solvent, catalyst, and photoinitiator, is developed. Mechanical characterization studies demonstrate that QHM polymers possesses phototunable bone- and tendon-like tensile and compressive properties (12-74 MPa tensile strength, 0.6-2.7 GPa tensile modulus, 58-121 MPa compressive strength, and 1.5-3.0 GPa compressive modulus), including the capability to withstand 10 000 cycles of physiological tensile loading and reduce stress concentrations via stiffness gradients. Biophysicochemical studies demonstrate that QHM polymers have clinically favorable attributes vital to rotator cuff repair stability, including slow degradation profiles (5-30% mass loss after 8 weeks) with little-to-no cytotoxicity in vitro, exceptional suture retention ex vivo (2.79-3.56-fold less suture migration relative to a clinically available graft), and competent tensile properties (similar ultimate load but higher normalized tensile stiffness relative to a clinically available graft) as well as good biocompatibility for augmenting rat supraspinatus tendon repair in vivo. This work demonstrates functionally graded, bone-tendon-like biomaterials for interfacial tissue engineering.
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Affiliation(s)
- Dai Fei Elmer Ker
- Department of Orthopaedic Surgery Stanford University 300 Pasteur Drive, Stanford, CA 94305, USA
| | - Dan Wang
- Department of Orthopaedic Surgery Stanford University 300 Pasteur Drive, Stanford, CA 94305, USA
| | - Anthony William Behn
- Department of Orthopaedic Surgery Stanford University 300 Pasteur Drive, Stanford, CA 94305, USA
| | - Evelyna Tsi Hsin Wang
- Department of Material Science and Engineering Stanford University 496 Lomita Mall, Stanford, CA 94305, USA
| | - Xu Zhang
- Institute for Tissue Engineering and Regenerative Medicine The Chinese University of Hong Kong New Territories, Hong Kong SAR
| | - Benjamin Yamin Zhou
- Department of Mathematics Stanford University Building 380, Sloan Mathematical Center, Stanford, CA 94305, USA
| | | | - Sungwoo Kim
- Department of Orthopaedic Surgery Stanford University 300 Pasteur Drive, Stanford, CA 94305, USA
| | - John Kleimeyer
- Department of Orthopaedic Surgery Stanford University 300 Pasteur Drive, Stanford, CA 94305, USA
| | - Burhan Gharaibeh
- Department of Biological Sciences University of Pittsburgh 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Yaser Shanjani
- Department of Orthopaedic Surgery Stanford University 300 Pasteur Drive, Stanford, CA 94305, USA
| | - Drew Nelson
- Department of Mechanical Engineering Stanford University 440 Escondido Mall, Stanford, CA 94305, USA
| | - Marc Safran
- Department of Orthopaedic Surgery Stanford University 300 Pasteur Drive, Stanford, CA 94305, USA
| | - Emilie Cheung
- Department of Orthopaedic Surgery Stanford University 300 Pasteur Drive, Stanford, CA 94305, USA
| | - Phil Campbell
- Engineering Research Accelerator Carnegie Mellon University 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
| | - Yunzhi Peter Yang
- Department of Orthopaedic Surgery Stanford University 300 Pasteur Drive, Stanford, CA 94305, USA
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