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Updated: 16 min 34 sec ago

Getting PEEK to Stick to Bone: The Development of Porous PEEK for Interbody Fusion Devices.

16 min 34 sec ago
Related Articles

Getting PEEK to Stick to Bone: The Development of Porous PEEK for Interbody Fusion Devices.

Tech Orthop. 2017 Sep;32(3):158-166

Authors: Torstrick FB, Safranski DL, Burkus JK, Chappuis JL, Lee CSD, Guldberg RE, Gall K, Smith KE

Abstract
Interbody fusion cages are routinely implanted during spinal fusion procedures to facilitate arthrodesis of a degenerated or unstable vertebral segment. Current cages are most commonly made from polyether-ether-ketone (PEEK) due to its favorable mechanical properties and imaging characteristics. However, the smooth surface of current PEEK cages may limit implant osseointegration and may inhibit successful fusion. We present the development and clinical application of the first commercially available porous PEEK fusion cage (COHERE®, Vertera, Inc., Atlanta, GA) that aims to enhance PEEK osseointegration and spinal fusion outcomes. The porous PEEK structure is extruded directly from the underlying solid and mimics the structural and mechanical properties of trabecular bone to support bone ingrowth and implant fixation. Biomechanical testing of the COHERE® device has demonstrated greater expulsion resistance versus smooth PEEK cages with ridges and greater adhesion strength of porous PEEK versus plasma-sprayed titanium coated PEEK surfaces. In vitro experiments have shown favorable cell attachment to porous PEEK and greater proliferation and mineralization of cell cultures grown on porous PEEK versus smooth PEEK and smooth titanium surfaces, suggesting that the porous structure enhances bone formation at the cellular level. At the implant level, preclinical animal studies have found comparable bone ingrowth into porous PEEK as those previously reported for porous titanium, leading to twice the fixation strength of smooth PEEK implants. Finally, two clinical case studies are presented demonstrating the effectiveness of the COHERE® device in cervical spinal fusion.

PMID: 29225416 [PubMed - in process]

Contrast Enhanced μCT Imaging of Early Articular Changes in a Pre-Clinical Model of Osteoarthritis.

Tue, 2017-12-12 05:45

Contrast Enhanced μCT Imaging of Early Articular Changes in a Pre-Clinical Model of Osteoarthritis.

Osteoarthritis Cartilage. 2017 Oct 28;:

Authors: Reece DS, Thote T, Lin ASP, Willett NJ, Guldberg RE

Abstract
OBJECTIVE: The objective of this study was to characterize early osteoarthritis (OA) development in cartilage and bone tissues in the rat medial meniscus transection (MMT) model using non-destructive equilibrium partitioning of an ionic contrast agent micro-computed tomography (EPIC-μCT) imaging. Cartilage fibrillation, one of the first physiological developments in OA, was quantified in the rat tibial plateau as three-dimensional (3D) cartilage surface roughness using a custom surface-rendering algorithm.
METHODS: Male Lewis rats underwent MMT or sham-operation in the left leg. At one- and three-weeks post-surgery, the animals (n=7-8 per group) were euthanized and the left legs were scanned using EPIC-μCT imaging to quantify cartilage and bone parameters. In addition, a custom algorithm was developed to measure the roughness of 3D surfaces. This algorithm was validated and used to quantify cartilage surface roughness changes as a function of time post-surgery.
RESULTS: MMT surgery resulted in significantly greater cartilage damage and subchondral bone sclerosis with the damage increasing in both severity and area from one-to three-weeks post-surgery. Analysis of rendered 3D surfaces could accurately distinguish early changes in joints developing OA, detecting significant increases of 45% and 124% in surface roughness at one- and three-weeks post-surgery respectively.
CONCLUSION: Disease progression in the MMT model progresses sequentially through changes in the cartilage articular surface, extracellular matrix composition, and then osteophyte mineralization and subchondral bone sclerosis. Cartilage surface roughness is a quantitative, early indicator of degenerative joint disease in small animal OA models and can potentially be used to evaluate therapeutic strategies.

PMID: 29107695 [PubMed - as supplied by publisher]

Wireless Implantable Sensor for Noninvasive, Longitudinal Quantification of Axial Strain Across Rodent Long Bone Defects.

Tue, 2017-11-07 05:30

Wireless Implantable Sensor for Noninvasive, Longitudinal Quantification of Axial Strain Across Rodent Long Bone Defects.

J Biomech Eng. 2017 Nov 01;139(11):

Authors: Klosterhoff BS, Ghee Ong K, Krishnan L, Hetzendorfer KM, Chang YH, Allen MG, Guldberg RE, Willett NJ

Abstract
Bone development, maintenance, and regeneration are remarkably sensitive to mechanical cues. Consequently, mechanical stimulation has long been sought as a putative target to promote endogenous healing after fracture. Given the transient nature of bone repair, tissue-level mechanical cues evolve rapidly over time after injury and are challenging to measure noninvasively. The objective of this work was to develop and characterize an implantable strain sensor for noninvasive monitoring of axial strain across a rodent femoral defect during functional activity. Herein, we present the design, characterization, and in vivo demonstration of the device's capabilities for quantitatively interrogating physiological dynamic strains during bone regeneration. Ex vivo experimental characterization of the device showed that it possessed promising sensitivity, signal resolution, and electromechanical stability for in vivo applications. The digital telemetry minimized power consumption, enabling extended intermittent data collection. Devices were implanted in a rat 6 mm femoral segmental defect model, and after three days, data were acquired wirelessly during ambulation and synchronized to corresponding radiographic videos, validating the ability of the sensor to noninvasively measure strain in real-time. Together, these data indicate the sensor is a promising technology to quantify tissue mechanics in a specimen specific manner, facilitating more detailed investigations into the role of the mechanical environment in dynamic bone healing and remodeling processes.

PMID: 28975256 [PubMed - in process]

Deformation and fatigue of tough 3D printed elastomer scaffolds processed by fused deposition modeling and continuous liquid interface production.

Thu, 2017-10-05 04:45

Deformation and fatigue of tough 3D printed elastomer scaffolds processed by fused deposition modeling and continuous liquid interface production.

J Mech Behav Biomed Mater. 2017 Jul 01;75:1-13

Authors: Miller AT, Safranski DL, Wood C, Guldberg RE, Gall K

Abstract
Polyurethane (PU) based elastomers continue to gain popularity in a variety of biomedical applications as compliant implant materials. In parallel, advancements in additive manufacturing continue to provide new opportunities for biomedical applications by enabling the creation of more complex architectures for tissue scaffolding and patient specific implants. The purpose of this study was to examine the effects of printed architecture on the monotonic and cyclic mechanical behavior of elastomeric PUs and to compare the structure-property relationship across two different printing approaches. We examined the tensile fatigue of notched specimens, 3D crosshatch scaffolds, and two 3D spherical pore architectures in a physically crosslinked polycarbonate urethane (PCU) printed via fused deposition modeling (FDM) as well as a photo-cured, chemically-crosslinked, elastomeric PU printed via continuous liquid interface production (CLIP). Both elastomers were relatively tolerant of 3D geometrical features as compared to stiffer synthetic implant materials such as PEEK and titanium. PCU and crosslinked PU samples with 3D porous structures demonstrated a reduced tensile failure stress as expected without a significant effect on tensile failure strain. PCU crosshatch samples demonstrated similar performance in strain-based tensile fatigue as solid controls; however, when plotted against stress amplitude and adjusted by porosity, it was clear that the architecture had an impact on performance. Square shaped notches or pores in crosslinked PU appeared to have a modest effect on strain-based tensile fatigue while circular shaped notches and pores had little impact relative to smooth samples. When plotted against stress amplitude, any differences in fatigue performance were small or not statistically significant for crosslinked PU samples. Despite the slight difference in local architecture and tolerances, crosslinked PU solid samples were found to perform on par with PCU solid samples in tensile fatigue, when appropriately adjusted for material hardness. Finally, tests of samples with printed architecture localized to the gage section revealed an effect in which fatigue performance appeared to drastically improve despite the localization of strain.

PMID: 28689135 [PubMed - as supplied by publisher]

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