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Kiapour A, Massaad E, Kodigudla MK, Kelkar A, Begley MR, Goel VK, Block JE, Shin JH. Resisting subsidence with a truss Implant: Application of the "Snowshoe" principle for interbody fusion devices. J Biomech 2023; 155:111635. [PMID: 37216894 DOI: 10.1016/j.jbiomech.2023.111635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 04/10/2023] [Accepted: 05/09/2023] [Indexed: 05/24/2023]
Abstract
The primary objective was to compare the subsidence resistance properties of a novel 3D-printed spinal interbody titanium implant versus a predicate polymeric annular cage. We evaluated a 3D-printed spinal interbody fusion device that employs truss-based bio-architectural features to apply the snowshoe principle of line length contact to provide efficient load distribution across the implant/endplate interface as means of resisting implant subsidence. Devices were tested mechanically using synthetic bone blocks of differing densities (osteoporotic to normal) to determine the corresponding resistance to subsidence under compressive load. Statistical analyses were performed to compare the subsidence loads and evaluate the effect of cage length on subsidence resistance. The truss implant demonstrated a marked rectilinear increase in resistance to subsidence associated with increase in the line length contact interface that corresponds with implant length irrespective of subsidence rate or bone density. In blocks simulating osteoporotic bone, comparing the shortest with the longest length truss cage (40 vs. 60 mm), the average compressive load necessary to induce subsidence of the implant increased by 46.4% (383.2 to 561.0 N) and 49.3% (567.4 to 847.2 N) for 1 and 2 mm of subsidence, respectively. In contrast, for annular cages, there was only a modest increase in compressive load when comparing the shortest with the longest length cage at a 1 mm subsidence rate. The Snowshoe truss cages demonstrated substantially more resistance to subsidence than corresponding annular cages. Clinical studies are required to support the biomechanical findings in this work.
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Affiliation(s)
- Ali Kiapour
- Department of Neurosurgery Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
| | - Elie Massaad
- Department of Neurosurgery Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Manoj K Kodigudla
- Engineering Center for Orthopedic Research Excellence, The University of Toledo, Toledo, OH, USA
| | - Amey Kelkar
- Engineering Center for Orthopedic Research Excellence, The University of Toledo, Toledo, OH, USA
| | - Matthew R Begley
- Department of Mechanical Engineering, University of California, Santa Barbara, CA, USA
| | - Vijay K Goel
- Engineering Center for Orthopedic Research Excellence, The University of Toledo, Toledo, OH, USA
| | | | - John H Shin
- Department of Neurosurgery Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
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Abar B, Kwon N, Allen NB, Lau T, Johnson LG, Gall K, Adams SB. Outcomes of Surgical Reconstruction Using Custom 3D-Printed Porous Titanium Implants for Critical-Sized Bone Defects of the Foot and Ankle. Foot Ankle Int 2022; 43:750-761. [PMID: 35209733 PMCID: PMC9177519 DOI: 10.1177/10711007221077113] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Treating critically sized defects (CSDs) of bone remains a significant challenge in foot and ankle surgery. Custom 3D-printed implants are being offered to a small but growing subset of patients as a salvage procedure in lieu of traditional alternates such as structural allografts after the patient has failed prior procedures. The long-term outcomes of 3D-printed implants are still unknown and understudied because of the limited number of cases and short follow-up durations. The purpose of this study was to evaluate the outcomes of patients who received custom 3D-printed implants to treat CSDs of the foot and ankle in an attempt to aid surgeons in selecting appropriate surgical candidates. METHODS This was a retrospective study to assess surgical outcomes of patients who underwent implantation of a custom 3D-printed implant made with medical-grade titanium alloy powder (Ti-6Al-4V) to treat CSDs of the foot and ankle between June 1, 2014, and September 30, 2019. All patients had failed previous nonoperative or operative management before proceeding with treatment with a custom 3D-printed implant. Univariate and multivariate odds ratios (ORs) of a secondary surgery and implant removal were calculated for perioperative variables. RESULTS There were 39 cases of patients who received a custom 3D-printed implant with at least 1 year of follow-up. The mean follow-up time was 27.0 (12-74) months. Thirteen of 39 cases (33.3%) required a secondary surgery and 10 of 39 (25.6%) required removal of the implant because of septic nonunion (6/10) or aseptic nonunion (4/10). The mean time to secondary surgery was 10 months (1-22). Multivariate logistic regression revealed that patients with neuropathy were more likely to require a secondary surgery with an OR of 5.76 (P = .03). CONCLUSION This study demonstrated that 74% of patients who received a custom 3D-printed implant for CSDs did not require as subsequent surgery (minimum of 1-year follow-up). Neuropathy was significantly associated with the need for a secondary surgery. This is the largest series to date demonstrating the efficacy of 3D-printed custom titanium implants. As the number of cases using patient-specific 3D-printed titanium implant increases, larger cohorts of patients should be studied to identify other high-risk groups and possible interventions to improve surgical outcomes. LEVEL OF EVIDENCE Level IV, case series.
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Affiliation(s)
- Bijan Abar
- Dept. of Orthopaedic Surgery, Duke University School of Medicine, Durham, NC,Dept. of Mechanical Engineering and Materials Science, Duke University, Durham, NC
| | - Nicholas Kwon
- Dept. of Orthopaedic Surgery, Duke University School of Medicine, Durham, NC
| | - Nicholas B. Allen
- Dept. of Orthopaedic Surgery, Duke University School of Medicine, Durham, NC
| | - Trent Lau
- Dept. of Mechanical Engineering and Materials Science, Duke University, Durham, NC
| | - Lindsey G. Johnson
- Dept. of Orthopaedic Surgery, Duke University School of Medicine, Durham, NC
| | - Ken Gall
- Dept. of Mechanical Engineering and Materials Science, Duke University, Durham, NC
| | - Samuel B. Adams
- Dept. of Orthopaedic Surgery, Duke University School of Medicine, Durham, NC
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Kiapour A, Seim HB, Atkinson BL, Lalor PA, Block JE. Bone Mineralization and Spinal Fusion Evaluation of a Truss-based Interbody Fusion Device: Ovine Finite Element Analysis with Confirmatory In Vivo Outcomes. Spine (Phila Pa 1976) 2022; 47:E319-E327. [PMID: 34593736 PMCID: PMC8912963 DOI: 10.1097/brs.0000000000004256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 09/01/2021] [Accepted: 09/02/2021] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Finite element analysis (FEA) and in vivo ovine spinal interbody fusion study. OBJECTIVE To determine comparative load-induced strain amplitudes, bone mineralization and fusion outcomes associated with different diameter struts in a truss-based interbody fusion device. SUMMARY OF BACKGROUND DATA Additive manufacturing technology has been employed to develop implants that actively participate in the fusion process. The truss device enables the optimal transfer of compressive and tensile stresses via the struts. Mechanobiologic principles postulate that strut diameter can be regulated to allow different magnitudes of strain distribution within the struts which may affect fusion rates. METHODS Modeling of strain distributions as a function of strut diameter (0.75, 1.0, 1.25, and 1.5 mm) employed FEA that simulated physiologic loading conditions. A confirmatory in vivo ovine lumbar spinal interbody fusion study compared fusion scores and bone histomorphometric variables for cages with 0.75 and 1.5 mm strut diameters. Outcomes were compared at 3-, 6-, and 12-month follow-up intervals. RESULTS FEA showed an inverse association between strut diameter and peak strain amplitude. Cages with 1.0, 1.25, and 1.5 mm struts had peak strain values that were 36%, 60%, and 73% lower than the 0.75 mm strut strain value. In vivo results showed the mean fusion score for the 0.75 mm diameter strut cage was significantly greater by 3-months versus the 1.5 mm strut cage, and remained significantly higher at each subsequent interval (P < 0.001 for all comparisons). Fusion rates were 95%, 100%, and 100% (0.75 mm) and 72.7%, 86.4%, and 95.8% (1.5 mm) at 3, 6, and 12 months. Thinner struts had greater mineralized bone tissue and less fibrous/chondral tissue than the thicker struts at each follow-up. CONCLUSION Validating FEA estimates, cages with smaller diameter struts exhibited more rapid fusion consolidation and more aggressive osseointegration compared with cages with larger diameters struts.Level of Evidence: 4.
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Affiliation(s)
- Ali Kiapour
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA
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Loenen ACY, Noailly J, Ito K, Willems PC, Arts JJ, van Rietbergen B. Patient-Specific Variations in Local Strain Patterns on the Surface of a Trussed Titanium Interbody Cage. Front Bioeng Biotechnol 2022; 9:750246. [PMID: 35087797 PMCID: PMC8786731 DOI: 10.3389/fbioe.2021.750246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 12/21/2021] [Indexed: 11/13/2022] Open
Abstract
Introduction: 3D printed trussed titanium interbody cages may deliver bone stimulating mechanobiological strains to cells attached at their surface. The exact size and distribution of these strains may depend on patient-specific factors, but the influence of these factors remains unknown. Therefore, this study aimed to determine patient-specific variations in local strain patterns on the surface of a trussed titanium interbody fusion cage.Materials and Methods: Four patients eligible for spinal fusion surgery with the same cage size were selected from a larger database. For these cases, patient-specific finite element models of the lumbar spine including the same trussed titanium cage were made. Functional dynamics of the non-operated lumbar spinal segments, as well as local cage strains and caudal endplate stresses at the operated segment, were evaluated under physiological extension/flexion movement of the lumbar spine.Results: All patient-specific models revealed physiologically realistic functional dynamics of the operated spine. In all patients, approximately 30% of the total cage surface experienced strain values relevant for preserving bone homeostasis and stimulating bone formation. Mean caudal endplate contact pressures varied up to 10 MPa. Both surface strains and endplate contact pressures varied more between loading conditions than between patients.Conclusions: This study demonstrates the applicability of patient-specific finite element models to quantify the impact of patient-specific factors such as bone density, degenerative state of the spine, and spinal curvature on interbody cage loading. In the future, the same framework might be further developed in order to establish a pipeline for interbody cage design optimizations.
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Affiliation(s)
- Arjan C. Y. Loenen
- Laboratory for Experimental Orthopaedics, Department of Orthopaedic Surgery, CAPHRI, Maastricht University Medical Center, Maastricht, Netherlands
- Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands
| | - Jérôme Noailly
- Department of Information and Communication Technologies, BCN MedTech, Universitat Pompeu Fabra, Barcelona, Spain
| | - Keita Ito
- Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands
| | - Paul C. Willems
- Laboratory for Experimental Orthopaedics, Department of Orthopaedic Surgery, CAPHRI, Maastricht University Medical Center, Maastricht, Netherlands
| | - Jacobus J. Arts
- Laboratory for Experimental Orthopaedics, Department of Orthopaedic Surgery, CAPHRI, Maastricht University Medical Center, Maastricht, Netherlands
- Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands
| | - Bert van Rietbergen
- Laboratory for Experimental Orthopaedics, Department of Orthopaedic Surgery, CAPHRI, Maastricht University Medical Center, Maastricht, Netherlands
- Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands
- *Correspondence: Bert van Rietbergen,
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Loenen ACY, Peters MJM, Bevers RTJ, Schaffrath C, van Haver E, Cuijpers VMJI, Rademakers T, van Rietbergen B, Willems PC, Arts JJ. Early bone ingrowth and segmental stability of a trussed titanium cage versus a polyether ether ketone cage in an ovine lumbar interbody fusion model. Spine J 2022; 22:174-182. [PMID: 34274502 DOI: 10.1016/j.spinee.2021.07.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 07/04/2021] [Accepted: 07/08/2021] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Lumbar interbody fusion is an effective treatment for unstable spinal segments. However, the time needed to establish a solid bony interbody fusion between the two vertebrae may be longer than twelve months after surgery. During this time window, the instrumented spinal segment is assumed to be at increased risk for instability related complications such as cage migration or subsidence. It is hypothesized that the design of new interbody cages that enable direct osseointegration of the cage at the vertebral endplates, without requiring full bony fusion between the two vertebral endplates, might shorten the time window that the instrumented spinal segment is susceptible to failure. PURPOSE To quantify the bone ingrowth and resulting segmental stability during consolidation of lumbar interbody fusion using two different cage types. STUDY DESIGN Preclinical ovine model. METHODS Seven skeletally mature sheep underwent bi-segmental lumbar interbody fusion surgery with one conventional polyether ether ketone (PEEK) cage, and one newly developed trussed titanium (TT) cage. After a postoperative time period of 13 weeks, non-destructive range of motion testing, and histologic analysis was performed. Additionally, sample specific finite element (FE) analysis was performed to predict the stability of the interbody fusion region alone. RESULTS Physiological movement of complete spinal motion segments did not reveal significant differences between the segments operated with PEEK and TT cages. The onset of creeping substitution within the cage seemed to be sooner for PEEK cages, which led to significantly higher bone volume over total volume (BV/TV) compared with the TT cages. TT cages showed significantly more direct bone to implant contact (BIC). Although the mean stability of the interbody fusion region alone was not statistically different between the PEEK and TT cages, the variation within the cage types illustrated an all-or-nothing response for the PEEK cages while a more gradual increase in stability was found for the TT cages. CONCLUSIONS Spinal segments operated with conventional PEEK cages were not different from those operated with newly developed TT cages in terms of segmental stability but did show a different mechanism of bone ingrowth and attachment. Based on the differences in development of bony fusion, we hypothesize that TT cages might facilitate increased early segmental stability by direct osseointegration of the cage at the vertebral endplates without requiring complete bony bridging through the cage. CLINICAL SIGNIFICANCE Interbody cage type affects the consolidation process of spinal interbody fusion. Whether different consolidation processes of spinal interbody fusion result in clinically significant differences requires further investigation.
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Affiliation(s)
- Arjan C Y Loenen
- Department of Orthopedic Surgery, Laboratory for Experimental Orthopedics, CAPHRI, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Biomedical Engineering, Orthopedic Biomechanics, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Marloes J M Peters
- Department of Orthopedic Surgery, Laboratory for Experimental Orthopedics, CAPHRI, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Raymond T J Bevers
- Department of Orthopedic Surgery, Laboratory for Experimental Orthopedics, CAPHRI, Maastricht University Medical Center, Maastricht, the Netherlands
| | | | | | - Vincent M J I Cuijpers
- Department of Biomaterials, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Timo Rademakers
- Department of Cell Biology-Inspired Tissue Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht, the Netherlands
| | - Bert van Rietbergen
- Department of Orthopedic Surgery, Laboratory for Experimental Orthopedics, CAPHRI, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Biomedical Engineering, Orthopedic Biomechanics, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Paul C Willems
- Department of Orthopedic Surgery, Laboratory for Experimental Orthopedics, CAPHRI, Maastricht University Medical Center, Maastricht, the Netherlands
| | - Jacobus J Arts
- Department of Orthopedic Surgery, Laboratory for Experimental Orthopedics, CAPHRI, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Biomedical Engineering, Orthopedic Biomechanics, Eindhoven University of Technology, Eindhoven, the Netherlands.
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Hunt JP, Begley MR, Block JE. Truss implant technology™ for interbody fusion in spinal degenerative disorders: profile of advanced structural design, mechanobiologic and performance characteristics. Expert Rev Med Devices 2021; 18:707-715. [PMID: 34160337 DOI: 10.1080/17434440.2021.1947244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Introduction: Interbody fusion devices are customarily used in fusion of the anterior spinal column for treatment of degenerative disc disease. Their traditional role is to reestablish and maintain intervertebral disc height, contain bone graft and provide mechanical support for the spine while osseointegration takes place. Utilizing the principles of mechanobiology, a unique biokinetic interbody fusion device has been developed that employs an advanced structural design to facilitate and actively participate in the fusion consolidation process.Areas covered: This article profiles and characterizes 4WEB Medical's Truss Implant Technology™ which includes a range of 3D-printed titanium spinal interbody implants and non-spinal implants whose design is based on truss structures enabled by advances in additive manufacturing. Four main areas of the implant design and functionality are detailed: bio-architecture, mechanobiologic underpinnings, bioactive surface features, and subsidence resistance. Pre-clinical and clinical examples are provided to describe and specify the bioactive roles and contributions of each design feature.Expert opinion: The distinct and unique combination of features incorporated within the truss cage design results in a biokinetic implant that actively participates in the bone healing cascade and fusion process.
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Affiliation(s)
| | - Matthew R Begley
- Department of Engineering, University of California, Santa Barbara, Santa Barbara, USA
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Wang H, Su K, Su L, Liang P, Ji P, Wang C. The effect of 3D-printed Ti6Al4V scaffolds with various macropore structures on osteointegration and osteogenesis: A biomechanical evaluation. J Mech Behav Biomed Mater 2018; 88:488-496. [DOI: 10.1016/j.jmbbm.2018.08.049] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 08/05/2018] [Accepted: 08/29/2018] [Indexed: 12/25/2022]
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Strains in trussed spine interbody fusion implants are modulated by load and design. J Mech Behav Biomed Mater 2018; 80:203-208. [DOI: 10.1016/j.jmbbm.2018.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 01/06/2018] [Accepted: 02/02/2018] [Indexed: 12/31/2022]
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