Usefulness of polyetheretherketone (PEEK) cage with plate augmentation for anterior arthrodesis in traumatic cervical spine injury

The bone morphogenetic protein 2 analogue L51P enhances spinal fusion in combination with BMP2 in an in vivo rat tail model

Bone morphogenic protein 2 (BMP2) is known to induce osteogenesis and is applied clinically to enhance spinal fusion despite adverse effects. BMP2 needs to be used in high doses to be effective due to the presence of BMP2 inhibitors. L51P is a BMP2 analogue that acts by inhibition of BMP2 inhibitors. Here, we hypothesized that mixtures of BMP2 and L51P could achieve better spinal fusion outcomes regarding ossification. To test whether mixtures of both cytokines are sufficient to improve ossification, 45 elderly Wistar rats (of which 21 were males) were assigned to seven experimental groups, all which received spinal fusion surgery, including discectomy at the caudal 4-5 level using an external fixator and a porous β-tricalcium phosphate (βTCP) carrier. These βTCP carriers were coated with varying concentrations of BMP2 and L51P. X-rays were taken immediately after surgery and again six and twelve weeks post-operatively. Histological sections and µCT were analyzed after twelve weeks. Spinal fusion was assessed using X-ray, µCT and histology according to the Bridwell scale by voxel-based quantification and a semi-quantitative histological score, respectively. The results were congruent across modalities and revealed high ossification for high-dose BMP2 (10 µg), while PBS induced no ossification. Low-dose BMP2 (1 µg) or 10 µg L51P alone did not induce relevant bone formation. However, all combinations of low-dose BMP2 with L51P (1 µg + 1/5/10 µg) were able to induce similar ossificationas high-dose BMP2. These results are of high clinical relevance, as they indicate L51P is sufficient to increase the efficacy of BMP2 and thus lower the required dose for spinal fusion. STATEMENT OF SIGNIFICANCE: Spinal fusion surgery is frequently applied to treat spinal pathologies. Bone Morphogenic Protein-2 (BMP2) has been approved by the U .S. Food and Drug Administration (FDA-) and by the "Conformité Européenne" (CE)-label. However, its application is expensive and high concentrations cause side-effects. This research targets the improvement of the efficacy of BMP2 in spinal fusion surgery.

Multiscale Mechanical Characterization of Polyether-2-ketone (PEKK) for Biomedical Application

Polyether-ether-2-ketone (PEKK) is a high-performance thermoplastic polymer used in various fields, from aerospace to medical applications, due to its exceptional mechanical and thermal properties. Nonetheless, the mechanical behavior of 3D-printed PEKK still deserves to be more thoroughly investigated, especially in view of its production by 3D printing, where mechanical properties measured at different scales are likely to be correlated to one another and to all play a major role in determining biomechanical properties, which include mechanical strength on one side and osteointegration ability on the other side. This work explores the mechanical behavior of 3D-printed PEKK through a multiscale approach, having performed both nanoindentation tests and standard tensile and compression tests, where a detailed view of strain distribution was achieved through Digital Image Correlation (DIC) techniques. Furthermore, for specimens tested up to failure, their fractured surfaces were analyzed through Scanning Electron Microscopy (SEM) to clearly outline fracture modes. Additionally, the internal structure of 3D-printed PEKK was explored through Computed Tomography (CT) imaging, providing a three-dimensional view of the internal structure and the presence of voids and other imperfections. Finally, surface morphology was analyzed through confocal microscopy. The multiscale approach adopted in the present work offers information about the global and local behavior of the PEKK, also assessing its material properties down to the nanoscale. Due to its novelty as a polymeric material, no previous studies have approached a multiscale analysis of 3D-printed PEKK. The findings of this study contribute to a comprehensive understanding of 3D-printed PEKK along with criteria for process optimization in order to customize its properties to meet specific application requirements. This research not only advances the knowledge of PEKK as a 3D-printing material but also provides insights into the multifaceted nature of multiscale material characterization.

Modification of polyetheretherketone implants: From enhancing bone integration to enabling multi-modal therapeutics

Polyetheretherketone (PEEK) is a popular thermoplastic material widely used in engineering applications due to its favorable mechanical properties and stability at high temperatures. With the first implantable grade PEEK being commercialized in 1990s, the use of PEEK has since grown exponentially in the biomedical field and has rapidly transformed a large section of the medical devices landscape. Nowadays, PEEK is a standard biomaterial used across a wide range of implant applications, however, its bioinertness remains a limitation for bone repair applications. The increasing demand for enhanced treatment efficacy/improved patient quality of life, calls for next-generation implants that can offer fast bone integration as well as other desirable therapeutic functions. As such, modification of PEEK implants has progressively shifted from offering desirable mechanical properties, enhancing bioactivity/fast osteointegration, to more recently, tackling post-surgery bacterial infection/biofilm formation, modulation of inflammation and management of bone cancers. Such progress is also accompanied by the evolution of the PEEK manufacturing technologies, to meet the ever increasing demand for more patient specific devices. However, no review has comprehensively covered the recently engaged application areas to date. This paper provides an up-to-date review on the development of PEEK-based biomedical devices in the past 10 years, with particularly focus on modifying PEEK for multi-modal therapeutics. The aim is to provide the peers with a timely update, which may guide and inspire the research and development of next generation PEEK-based healthcare products. STATEMENT OF SIGNIFICANCE: Significant progress has been made in PEEK processing and modification techniques in the past decades, which greatly contributed to its wide applications in the biomedical field. Despite the high volume of published literature on PEEK implant related research, there is a lack of review on its emerging applications in multi-modal therapeutics, which involve bone regeneration, anti-bacteria/anti-inflammation, and cancer inhibition, etc. This timely review covers the state-of-the-art in these exciting areas and provides the important guidance for next generation PEEK based biomedical device research and development.

Biologically Modified Polyether Ether Ketone as Dental Implant Material

Polyether ether ketone (PEEK) is a non-toxic polymer with elastic modulus close to human bone. Compared with metal implants, PEEK has advantages such as evasion of stress shielding effect, easy processing, and similar color as teeth, among others. Therefore, it is an excellent substitute material for titanium dental orthopedic implants. However, PEEK's biological inertia limits its use as an implant. To change PEEK's biological inertia and increase its binding ability with bone tissue as an implant, researchers have explored a number of modification methods to enhance PEEK's biological activities such as cellular compatibility, osteogenic activity, and antibacterial activity. This review summarizes current biological activity modification methods for PEEK, including surface modification and blending modification, and analyzes the advantages and disadvantages of each modification method. We believe that modified PEEK will be a promising dental and orthopedic implant material.

Correlation of Anterior Interbody Graft Choice With Patient-Reported Outcomes in Cervical Spine Trauma

STUDY DESIGN

Ambispective observational cohort study.

OBJECTIVES

Synthetic graft usage avoids morbidity associated with harvest and reduces operative time. This study aims to evaluate outcomes of anterior cervical stabilization surgery using a synthetic cage in comparison with iliac crest bone graft (ICBG) following cervical spine trauma.

METHODS

An ambispective review was conducted on patients from the Alfred Trauma Registry. Consecutive patients treated at a level 1 trauma center, aged 18 years and older who were treated with standalone anterior cervical stabilization following spine trauma (2011-2016) were included in the study. Primary outcome measures were patient overall satisfaction, Neck Disability Index (NDI), neck pain 10-point visual analogue scale (VAS-neck) and arm pain 10-point visual analogue scale (VAS-arm). Secondary outcome measures were radiographic evidence of fusion and rate of revision surgery. All patients had follow-up for at least 1 year.

RESULTS

Between 2011 and 2016, 114 traumatic disc levels in 104 patients were treated. ICBG was used in 32% and polyetheretherketone (PEEK) cage in 68% of the patients. Both groups had similar demographic metrics. There was no significant difference in primary outcome measures between the graft types: (1) patient satisfaction (P = .15), (2) NDI (P = .11), (3) VAS-neck (P = .13), and (4) VAS-arm (P = .20). Radiology based fusion assessment 6 months postsurgery did not show statistical significance (P = .10). The rates of revision surgery were similar.

CONCLUSIONS

This study showed no significant difference in patient-reported outcome measures when comparing the usage of PEEK cage and ICBG in anterior stand alone cervical spine stabilization. Level 1 evidence studies are required to further investigate this finding.

Outcomes of Anterior Cervical Fusion Using Polyetheretherketone Cage with Demineralized Bone Matrix and Plate for Management of Subaxial Cervical Spine Injuries

Objective

We evaluated the usefulness of a polyetheretherketone (PEEK) cage filled with demineralized bone matrix (DBM) and plate fixation in anterior interbody fusions for subaxial cervical spine injuries.

Methods

A retrospective review of 98 patients (58 women, 40 men; mean age, 49.7 years; range, 17–78 years) who underwent single-level anterior cervical discectomy and fusion (ACDF) using a PEEK cage filled with DBM and plate fixation for subaxial cervical spine injuries from March 2005 to June 2018 was conducted. Bone fusion, interbody height (IBH), segmental lordosis, and adjacent segment degeneration (ASD) development were assessed with plain radiographs and computed tomography. Clinical outcomes were assessed using a visual analog scale (VAS) for pain and the Frankel grade for neurologic function.

Results

The mean follow-up period was 27.6 months (range, 6–142 months). Twenty-one patients (21.4%) had an improvement of at least one Frankel grade. The mean preoperative and final follow-up neck pain VAS scores were 8.3±0.9 and 2.6±1.5 (p<0.05). All patients showed solid fusion at the final follow-up. The mean preoperative and final Cobb's angles were −3.7±7.9° and 1.9±5.1° (p<0.05). The mean preoperative and final IBHs were 36.9±1.7 mm and 38.2±1.8 mm (p<0.05). Five patients (5%) showed ASD.

Conclusion

ACDF using a PEEK cage filled with DBM and plate fixation yielded high fusion rates and satisfactory clinical outcomes without donor-site morbidity. This procedure is safe and effective for single-level subaxial cervical spine injuries.

Antibacterial properties of nano-silver coated PEEK prepared through magnetron sputtering

OBJECTVE

We aimed to investigate the cytotoxicity and antibacterial properties of nano-silver-coated polyetheretherketone (PEEK) produced through magnetron sputtering and provide a theoretical basis for its use in clinical applications.

METHODS

The surfaces of PEEKs were coated with nano-silver at varying thicknesses (3, 6, 9, and 12nm) through magnetron sputtering technology. The resulting coated PEEK samples were classified into the following groups according to the thickness of the nano-silver coating: PEEK-3 (3nm), PEEK-6 (6nm), PEEK-9 (9nm), PEEK-12 (12nm), and PEEK control group. The surface microstructure and composition of each sample were observed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive spectrum (EDS) analysis. The water contact angle of each sample was then measured by contact angle meters. A cell counting kit (CCK-8) was used to analyze the cytotoxicity of the mouse fibroblast cells (L929) in the coated groups (n=5) and group test samples (n=6), negative control (polyethylene, PE) (n=6), and positive control group (phenol) (n=6). The antibacterial properties of the samples were tested by co-culturing Streptococcus mutans and Straphylococcus aureus. The bacteria that adhered to the surface of samples were observed by SEM. The antibacterial adhesion ability of each sample was then evaluated.

RESULTS

SEM and AFM analysis results showed that the surfaces of control group samples were smooth but compact. Homogeneous silver nano-particles (AgNPs) and nano-silver coating were uniformly distributed on the surface of the coated group samples. Compared with the control samples, the nano-silver coated samples had a significant increase in surface roughness (P<0.05) as the thickness of their nano-silver coating increased. EDS analysis showed that not only C and O but also Ag were present on the surface of the coated samples. Moreover, the water contact angle of modified samples significantly increased after nano-silver coating modification (P<0.01). CCK-8 cytotoxicity test results showed that coated samples did not exhibit cytotoxicity. The antibacterial experimental results showed that the nano-silver coating can significantly improve the antibacterial activity and bacterial adhesion ability of the PEEK samples.

SIGNIFICANCE

The compact and homogeneous nano-silver coating was successfully prepared on the surface of PEEK through magnetron sputtering. The nano-silver coated PEEKs demonstrated enhanced antibacterial activities and bacterial adhesion abilities and had no cytotoxic effects.

Polyetheretherketone Cage with Demineralized Bone Matrix Can Replace Iliac Crest Autografts for Anterior Cervical Discectomy and Fusion in Subaxial Cervical Spine Injuries

Objective

This study aimed to compare the clinical and radiologic outcomes of patients with subaxial cervical injury who underwent anterior cervical discectomy and fusion (ACDF) with autologous iliac bone graft or polyetheretherketone (PEEK) cages using demineralized bone matrix (DBM).

Methods

From January 2005 to December 2010, 70 patients who underwent one-level ACDF with plate fixation for post-traumatic subaxial cervical spinal injury in a single institution were retrospectively investigated. Autologous iliac crest grafts were used in 33 patients (Group I), whereas 37 patients underwent ACDF using a PEEK cage filled with DBM (Group II). Plain radiographs were used to assess bone fusion, interbody height (IBH), segmental angle (SA), overall cervical sagittal alignment (CSA, C2–7 angle), and development of adjacent segmental degeneration (ASD). Clinical outcome was assessed using a visual analog scale (VAS) for pain and Frankel grade.

Results

The mean follow-up duration for patients in Group I and Group II was 28.9 and 25.4 months, respectively. All patients from both groups achieved solid fusion during the follow-up period. The IBH and SA of the fused segment and CSA in Group II were better maintained during the follow-up period. Nine patients in Group I and two patients in Group II developed radiologic ASD. There were no statistically significant differences in the VAS score and Frankel grade between the groups.

Conclusion

This study showed that PEEK cage filled with DBM, and plate fixation is at least as safe and effective as ACDF using autograft, with good maintenance of cervical alignment. With advantages such as no donor site morbidity and no graft-related complications, PEEK cage filled with DBM, and plate fixation provide a promising surgical option for treating traumatic subaxial cervical spine injuries.

Comparison Between Acrylic Cage and Polyetheretherketone (PEEK) Cage in Single-level Anterior Cervical Discectomy and Fusion: A Randomized Clinical Trial

STUDY DESIGN

Prospective, single-blind randomized-controlled clinical study.

OBJECTIVE

To compare polyetheretherketone (PEEK) cage with a novel Acrylic cage to find out which fusion cage yielded better clinical outcomes following single-level anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

ACDF is considered a standard neurosurgical treatment for degenerative diseases of cervical intervertebral disks. There are many options, including bone grafts, bone cement, and spacers made of titanium, carbon fiber, and synthetic materials, used to restore physiological disk height and enhance spinal fusion, but the ideal device, which would provide immediate structural support and subsequent osteointegration and stability, has not been identified yet. To overcome this, we designed a new, inexpensive Acrylic cage.

MATERIALS AND METHODS

A total of 64 patients were eligible to participate and were randomly allocated to undergo ACDF either with Acrylic interbody fusion cage filled with bone substitute (n=32) or PEEK cage (n=32). Nurick's grading was used for quantifying the neurological deficit. Clinical and radiologic outcome was assessed preoperatively, immediately after surgery, and subsequently at 2, 6, and 12 months of follow-up using Odom's criteria and dynamic radiographs (flexion-extension) and computed tomography scans, respectively.

RESULTS

There was a statistically significant improvement in the clinical outcomes of the Acrylic cage group compared with the PEEK cage group (mean difference: -0.438; 95% confidence interval, -0.807 to -0.068; P=0.016). There was a statistically significant difference in disk space height increase between the 2 groups at the 6- and 12-month follow-up. The Acrylic cage achieved higher fusion rate (good fusion) than the PEEK cage (96.9% vs. 93.8%). Intervertebral angle demonstrated a significant difference among the 2 treated groups throughout the follow-up period.

CONCLUSION

This study suggests that the use of Acrylic cage is associated with good clinical and radiologic outcomes and it can be therefore a good substitute for bone graft and other cages in ACDF.

Anterior cervical interbody fusion using polyetheretherketone cage filled with synthetic bone graft in acute cervical spine injury

PURPOSE

The aim of this study was to assess the interbody fusion rate for patients treated by anterior cervical interbody fusion (ACIF) using polyetheretherketone (PEEK) cages filled with synthetic bone graft in acute cervical spine injury.

MATERIALS AND METHODS

Twenty-nine patients (mean age: 49 years) with monosegmental instability due to cervical spine injury were followed. We assessed the rate of and time to interbody fusion at 1-year follow-up. In case of secondary displacement, we analysed its causes and surgical management.

RESULTS

The rate of fusion was 86.2%. The mean time to fusion was 7.2 months. Interbody fusion was observed at 3 months in 4 patients, at 6 months in 14 and at 1 year in 7. Four patients had secondary displacement within 3 months.

CONCLUSION

ACIF with a PEEK cage filled with synthetic bone graft seems to be an alternative to iliac crest bone graft with no morbidity related to the harvest site.

Effect of different surface treatments and thermocycling on shear bond strength to polyetheretherketone

This study was designed to evaluate the shear bond strength of an adhesive/composite system subjected to different pretreated polyetheretherketone (PEEK) surfaces using different thermocycling conditioning methods. A total of 128 specimens were equally divided into four main groups ( n = 32/group): control (no pretreatment), air abrasion, argon plasma pretreatment, and femtosecond laser groups. The surface topographies and surface roughness were observed by atomic force microscopy after different pretreatments. The specimens were bonded with SE Bond/Clearfil AP-X™. All bonded specimens were stored in distilled water at 37°C for 24 h. Afterward, each group was divided into three subgroups ( n = 8/group) as follows: (a) stored in water for 56 h (37°C); (b) thermal aging for 5000 cycles (5°C/55°C); and (c) thermal aging for 10,000 cycles (5°C/55°C). The shear bond strengths were measured. Air abrasion, argon plasma pretreatment, and femtosecond laser significantly strengthened the bond of SE Bond/Clearfil AP-X™ to PEEK composite compared with that without additional pretreatment. In the same surface pretreatment, the shear bond strengths of specimens conditioned using water storage were higher than that using thermocycles (TCs). Additionally, the specimens with 5000 TC showed significantly higher shear bond strength than that with 10000 TC.

Indication for spinal fusion and the risk of adjacent segment pathology: does reason for fusion affect risk? A systematic review

STUDY DESIGN

A systematic review.

OBJECTIVE

To determine whether different indications or reasons for spinal fusion are associated with different risks of subsequent adjacent segment pathology (ASP) in the lumbar and cervical spine.

SUMMARY OF BACKGROUND DATA

Pre-existing degeneration at levels adjacent to an arthrodesis may play a role in the development of symptomatic adjacent segment pathology. Although most spinal arthrodeses occur in patients with degenerative spinal disease, spinal fusion occurs in the pediatric and trauma population, and also congenitally. Evaluating the risk of ASP in these populations may shed light on its etiology.

METHODS

A systematic search was conducted in PubMed and the Cochrane Library for articles published between January 1, 1990, and December 31, 2011. We included all articles that described the risk of radiographical adjacent segment pathology (RASP) following surgical fusion for degenerative disease, for trauma, or for conditions requiring fusion in pediatrics in the lumbar or cervical spine. In addition, we included studies recording ASP in patients with congenital fusion.

RESULTS

Nineteen studies met our inclusion criteria. In patients who underwent fusion in the lumbar spine for degenerative reasons, the RASP rate averaged 12.4% during an average of 5.6-year follow-up. For patients who underwent fusion in the cervical spine for degenerative reasons, the average RASP rate was 25.3% during a 2.3-year follow-up. For patients with Klippel-Feil syndrome and congenital fusion, the RASP rate averaged 49.7% during an average of 23.5-years of follow-up. In patients who were fused for scoliosis, the average RASP rate was 20.3% of 3.9-year follow-up. However there is significant variation between studies in patient population, follow-up, and definition of RASP.

CONCLUSION

In the cervical spine, the rate of RASP in patients with fusion for degenerative reasons indications is greater than the rate of RASP in patients with congenital fusion suggesting that the pre-existing health and status of the adjacent level at the time of fusion may play a contributory role in the development of ASP. There is insufficient evidence in the literature to determine whether the indication/reason for fusion affects the risk of RASP in the lumbar spine

CONSENSUS STATEMENT

In the cervical spine, the rate of RASP in patients with fusion for degenerative reasons indications is greater than the rate of RASP in patients with congenital fusion suggesting that the pre-existing health and status of the adjacent level at the time of fusion may play a contributory role in the development of ASP. Strength of Statement: Weak.

The biomechanical stability of a novel spacer with integrated plate in contiguous two-level and three-level ACDF models: an in vitro cadaveric study

BACKGROUND CONTEXT

Anterior cervical plating increases stability and hence improves fusion rates to treat cervical spine pathologies, which are often symptomatic at multiple levels. However, plating is not without complications, such as dysphagia, injury to neural elements, and plate breakage. The biomechanics of a spacer with integrated plate system combined with posterior instrumentation (PI), in two-level and three-level surgical models, has not yet been investigated.

PURPOSE

The purpose of the study was to biomechanically evaluate the multidirectional rigidity of spacer with integrated plate (SIP) at multiple levels as comparable to traditional spacers and plating.

STUDY DESIGN

An in vitro cervical cadaveric model.

METHODS

Eight fresh human cervical (C2-C7) cadaver spines were tested under pure moments of ±1.5 Nm on spine simulator test frame. Each spine was tested in intact condition, with only anterior fixation and with both anterior and PI. Range of motion (ROM) was measured using Optotrak Certus (NDI, Inc., Waterloo, Ontario, Canada) motion analysis system in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) at the instrumented levels (C3-C6). Repeated-measures analysis of variance was used for statistical analysis.

RESULTS

All the surgical constructs showed significant reduction in motion compared with intact condition. In two-level fusion, SIP (C4-C6) construct significantly reduced ROM by 66.5%, 65.4%, and 60.3% when compared with intact in FE, LB, and AR, respectively. In three-level fusion, SIP (C3-C6) construct significantly reduced ROM by 65.8%, 66%, and 49.6% when compared with intact in FE, LB, and AR, respectively. Posterior instrumentation showed significant stability only in three-level fusion when compared with their respective anterior constructs. In both two-level and three-level fusion, SIP showed comparable stability to traditional spacer and plate constructs in all loading modes.

CONCLUSIONS

The anatomically profiled spacer with integrated plate allows treatment of cervical disorders with fewer steps and less impact to cervical structures. In this biomechanical study, spacer with integrated plate construct showed comparable stability to traditional spacer and plate for two-level and three-level fusion. Posterior instrumentation showed significant effect only in three-level fusion. Clinical data are required for further validation of using spacer with integrated plate at multiple levels.

Cervical radiculopathy: a review

BACKGROUND

Cervical radiculopathy is defined as a syndrome of pain and/or sensorimotor deficits due to compression of a cervical nerve root. Understanding of this disease is vital for rapid diagnosis and treatment of patients with this condition, facilitating their recovery and return to regular activity.

PURPOSE

This review is designed to clarify (1) the pathophysiology that leads to nerve root compression; (2) the diagnosis of the disease guided by history, physical exam, imaging, and electrophysiology; and (3) operative and non-operative options for treatment and how these should be applied.

METHODS

The PubMed database was searched for relevant articles and these articles were reviewed by independent authors. The conclusions are presented in this manuscript.

RESULTS

Facet joint spondylosis and herniation of the intervertebral disc are the most common causes of nerve root compression. The clinical consequence of radiculopathy is arm pain or paresthesias in the dermatomal distribution of the affected nerve and may or may not be associated with neck pain and motor weakness. Patient history and clinical examination are important for diagnosis. Further imaging modalities, such as x-ray, computed tomography, magnetic resonance imaging, and electrophysiologic testing, are of importance. Most patients will significantly improve from non-surgical active and passive therapies. Indicated for surgery are patients with clinically significant motor deficits, debilitating pain that is resistant to conservative modalities and/or time, or instability in the setting of disabling radiculopathy. Surgical treatment options include anterior cervical decompression with fusion and posterior cervical laminoforaminotomy.

CONCLUSION

Understanding the pathophysiology, diagnosis, treatment indications, and treatment techniques is essential for rapid diagnosis and care of patients with cervical radiculopathy.