Mechanical Properties of Bioresorbable Self-reinforced Posterior Cervical Rods

Savage, Katherine; Sardar, Zeeshan M.; Pohjonen, Timo; Sidhu, Gursukhman S.; Eachus, Benjamin D.; Vaccaro, Alexander R.

doi:10.1097/bsd.0b013e318299c6d8

Cited by 4 publications

(5 citation statements)

References 11 publications

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“…After an average of 18 months follow-up, there was no evidence of adjacent segment diseases in any of the cases. In contrast to traditional metallic implants, some polymer materials have biodegradable properties that allow the implant to degrade gradually over time [13,14]. The Young's modulus of the polymer rods was found to be closer to that of bone, and the lower stiffness of the rods meant less gradual dynamic loading and stress shielding of the fusion site.…”

Section: Introductionmentioning

confidence: 99%

Biomechanical analysis of single-level interbody fusion with different internal fixation rod materials: a finite element analysis

Hsieh

Kuo

Chen

et al. 2020

BMC Musculoskelet Disord

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Background: Lumbar spinal fusion with rigid spinal fixators as one of the high risk factors related to adjacentsegment failure. The purpose of this study is to investigate how the material properties of spinal fixation rods influence the biomechanical behavior at the instrumented and adjacent levels through the use of the finite element method. Methods: Five finite element models were constructed in our study to simulate the human spine pre-and postsurgery. For the four post-surgical models, the spines were implanted with rods made of three different materials: (i) titanium rod, (ii) PEEK rod with interbody PEEK cage, (iii) Biodegradable rod with interbody PEEK cage, and (iv) PEEK cage without pedicle screw fixation (no rods). Results: Fusion of the lumbar spine using PEEK or biodegradable rods allowed a similar ROM at both the fusion and adjacent levels under all conditions. The models with PEEK and biodegradable rods also showed a similar increase in contact forces at adjacent facet joints, but both were less than the model with a titanium rod. Conclusions: Flexible rods or cages with non-instrumented fusion can mitigate the increased contact forces on adjacent facet joints typically found following spinal fixation, and could also reduce the level of stress shielding at the bone graft.

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Section: Introductionmentioning

confidence: 99%

Biomechanical analysis of single-level interbody fusion with different internal fixation rod materials: a finite element analysis

Hsieh

Kuo

Chen

et al. 2020

BMC Musculoskelet Disord

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“…This study demonstrated how biodegradable implants may offer superior outcomes for lumbar spine fusion over conventional metal spinal implants, including a lower contact force at adjacent facet joints, lower peak stresses in the adjacent disc and greater loading on the anterior bone graft region. Savage et al [ 20 ] found that biodegradable rods produced less stress shielding and offered better dynamic loading in the spine over titanium rods. In addition to mechanical advantages, the radiolucent feature of resorbable rods could allow for better imaging and potentially eliminate surgical complications associated with removing metallic implants.…”

Section: Discussionmentioning

confidence: 99%

“…FE models of the biodegradable spinal rods (self-reinforced copolymer rod, Inion Oy, Tampere, Finland) [ 20 ] and titanium spinal rods were incorporated into the CB PROT II Posterior Spinal System (Chin Bone Corp., Taiwan; US FDA 510(k): K142655), which consists of titanium alloy screws (diameter 5.5 mm) connected by vertical rods. The lumbar intervertebral cage was modeled from the ReBorn Essence cage (Baui Biotech Co. Ltd., New Taipei City, Taiwan) made of PEEK.…”

Section: Methodsmentioning

confidence: 99%

“…Biodegradable implants break down gradually over time when placed in the body. As the implant degrades, loading is transferred to the surrounding anatomical structures, and so could be expected to have lower levels of stress shielding [ 18 – 20 ]. Therefore, biodegradable rods may be an attractive alternative for use in posterior lumbar fixation because of the ability to gradually transfer loads from the fixator to the fusion mass during the fusion process.…”

Section: Introductionmentioning

confidence: 99%

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Assessment of the suitability of biodegradable rods for use in posterior lumbar fusion: An in-vitro biomechanical evaluation and finite element analysis

et al. 2017

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Interbody fusion with posterior instrumentation is a common method for treating lumbar degenerative disc diseases. However, the high rigidity of the fusion construct may produce abnormal stresses at the adjacent segment and lead to adjacent segment degeneration (ASD). As such, biodegradable implants are becoming more popular for use in orthopaedic surgery. These implants offer sufficient stability for fusion but at a reduced stiffness. Tailored to degrade over a specific timeframe, biodegradable implants could potentially mitigate the drawbacks of conventional stiff constructs and reduce the loading on adjacent segments. Six finite element models were developed in this study to simulate a spine with and without fixators. The spinal fixators used both titanium rods and biodegradable rods. The models were subjected to axial loading and pure moments. The range of motion (ROM), disc stresses, and contact forces of facet joints at adjacent segments were recorded. A 3-point bending test was performed on the biodegradable rods and a dynamic bending test was performed on the spinal fixators according to ASTM F1717-11a. The finite element simulation showed that lumbar spinal fusion using biodegradable implants had a similar ROM at the fusion level as at adjacent levels. As the rods degraded over time, this produced a decrease in the contact force at adjacent facet joints, less stress in the adjacent disc and greater loading on the anterior bone graft region. The mechanical tests showed the initial average fatigue strength of the biodegradable rods was 145 N, but this decreased to 115N and 55N after 6 months and 12 months of soaking in solution. Also, both the spinal fixator with biodegradable rods and with titanium rods was strong enough to withstand 5,000,000 dynamic compression cycles under a 145 N axial load. The results of this study demonstrated that biodegradable rods may present more favourable clinical outcomes for lumbar fusion. These polymer rods could not only provide sufficient initial stability, but the loss in rigidity of the fixation construct over time gradually transfers loading to adjacent segments.

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“…A recent in vitro characterization study compared bioresorbable posterior cervical rods to commonly used Ti alloy rods. 41 The bioresorbable implants were shown to have adequate shear resistance but less load resistance and stiffness compared to the Ti rods. However, the stiffness of the bioresorbable rods (16.6-21.4 N/mm) was similar to bone, which resulted in better gradual dynamic loading.…”

Section: Bioabsorbablesmentioning

confidence: 99%

New biomaterials for orthopedic implants

Ong¹,

Yun²,

White³

2015

ORR

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With the increasing use of orthopedic implants worldwide, there continues to be great interest in the development of novel technologies to further improve the effective clinical performance of contemporary treatment modalities and devices. Continuing research interest also exists in developing novel bulk biomaterials (eg, polycarbonate urethanes, silicon) or novel formulations of existing but less widely used biomaterials (eg, polyaryletherketones, polyetheretherketone). There is also growing focus on customizing the material properties of bioabsorbables and composite materials with fillers such as bioactive ceramics. In terms of tissue engineering, more recent developments have focused on basic engineering and biological fundamentals to use cells, signaling factors, and the scaffold material itself to better restore tissue and organ structure and function. There has also been recent controversy with the use of injectables as a nonsurgical approach to treat joint disorders, but more attention is being directed toward the development of newer formulations with different molecular weights. The industry has also continuously sought to improve coatings to supplement the function of existing implants, with the goal of improving their osseointegrative qualities and incorporating antimicrobial properties. These include the use of bone morphogenetic protein, bisphosphonates, calcium phosphate, silicon nitride, and iodine. Due to the widespread use of bone graft materials, recent developments in synthetic graft materials have explored further development of bioactive glass, ceramic materials, and porous titanium particles. This review article provides an overview of ongoing efforts in the above research areas.

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Mechanical Properties of Bioresorbable Self-reinforced Posterior Cervical Rods

Cited by 4 publications

References 11 publications

Biomechanical analysis of single-level interbody fusion with different internal fixation rod materials: a finite element analysis

Biomechanical analysis of single-level interbody fusion with different internal fixation rod materials: a finite element analysis

Assessment of the suitability of biodegradable rods for use in posterior lumbar fusion: An in-vitro biomechanical evaluation and finite element analysis

New biomaterials for orthopedic implants

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