Cervical Cage Research Articles

Our first experience with cervical expandable cage for vertebral body reconstruction

Abstract Vertebral body reconstruction after corpectomy using expandable cage has become a common surgical procedure especially at thoracic level. The recent published papers describe the successful use of expandable cages for cervical vertebral body reconstruction. In this paper we present our first experience with expandable cervical cage in the reconstruction of the cervical spine in a patient with cervical spondylotic myelopathy (CSM)

Surgical planning, manufacturing and implantation of an individualized cervical fusion titanium cage using patient-specific data

Most cervical fusion cages imperfectly mimic the anatomy of the intervertebral disc space. The production of individualized cages might be the next step to further improve spinal implants due to their enhanced load-bearing surface. To evaluate the planning, manufacturing, and implantation of an individualized cervical cage in co-operation with EIT and 3D Systems. A digital 3D model of the patient's cervical spine was rendered from the patients CT data. It was then possible to correct degenerative deformities by digitally repositioning the vertebrae and virtually resecting the osteophytes. The implantation of the cage can be simulated to check the accuracy of the fit. The cage is made of trabecular titanium and manufactured by Direct Metal Printing. The pilot project for the implantation of the first individualized cervical cage ever, resulted in a highly accurate fit. During surgery, the cage self-located into the correct position after suspending distraction due to the implants unique end plate design. Furthermore, it was impossible to move the cage in any direction with the inserting instrument after suspending distraction for the same reason. Thus, it can be assumed that an individualized cervical implant provides excellent primary stability. Preconditions for the manufacturing of individualized cervical fusion cages using specific patient data are given. The implantation is uncomplicated. The improved load-bearing surface will lower the rate of implant dislocation and subsidence. The production of individualized cages at a reasonable price has to be evaluated by spine surgeons and the industry.

Cervical Footprint Anthropometry in Indian Population: Implications on Design of Artificial Disc Replacement Devices.

Study DesignCross-sectional study.PurposeTo accurately measure the dimensions of cervical endplates based on computed tomography (CT) scans in Indian population and assess accuracy of match with currently available cervical disc prostheses.Overview of LiteratureThe dimensions of currently available cervical disc replacement implants are based on early published geometrical measurements of vertebrae endplates for Caucasian population. To author's knowledge, similar study has not been published for patients from Indian subcontinent.MethodsCT scans of cervical spine of patients from Indian subcontinent were collected and reviewed. Seventy patients (54 men and 16 women; aged 18–56 years with average of 37 years) who underwent CT scans of cervical spine were included in study. 3D CT scans of sub axial cervical spine (C3 to C7) were analyzed. The anterior-posterior (AP) and central mediolateral (CML) dimensions of superior and inferior endplates from C3 to C7 were measured using digital measuring system.ResultsA total of 560 endplates of 70 patients were included in the study. The AP diameter of cervical endplates ranged from 0.87 to 2.47 cm. The CML diameters ranged from 0.84 to 2.98 cm. For levels C3/C4 and C4/C5 for AP dimension Prestige-LP (90.5%) and Prodisc-C (89%) discs showed higher percentage of matching than Discover discs (58.5%). For CML diameter, Prestige-LP (69.5%), Prodisc-C (70%) and Discover (39.5%) discs showed almost similar matching with measured endplates. For levels C5/C6 and C6/C7 for AP dimension, Prestige-LP (67.25%), Prodisc-C (49.35%) and Discover (51.5%) discs showed similar matching. For CML diameter Prestige-LP (32%), Prodisc-C (27.5%) and Discover (42.2%) discs showed poor matching with measured endplates.ConclusionsThis study indicates need for redesign of cervical disc prostheses to match Indian patients. The collected anthropometric dimensions from this study may be used to design and develop indigenous artificial total disc replacement prosthesis and even cervical cages in India. With the present study being a small pilot study, the authors recommend anthropometric CT measurements in larger number of Indian patients in order to validate footprint dimensions for designing better-matched prosthesis.

Cervical cage without plating in management of type II / II A Hangman’s fracture combined with intervertebral disc injury

BackgroundSurgical intervention is increasingly performed as the primary treatment of unstable Hangman’s fracture. Some authors have advocated using anterior C2/3 discectomy with interbody fusion and plating to treat unstable Hangman’s fracture combined with intervertebral disc injury; however, there are few reports on unstable Hangman’s fracture treated by anterior interbody fusion with the cervical cage (PEEK material) solely.MethodsThis study was to assess the efficacy of the cervical cage in management of unstable Hangman’s fracture combined with intervertebral disc injury. A cohort of 15 patients with unstable Hangman’s fractures fulfilling the inclusion criteria were prospectively submitted to surgical treatment of anterior C2/3 discectomy and interbody fusion using the cervical cage without plating. According to the Levine and Edwards classification, there were 5 type II, and 10 type IIA cases. The clinical outcome (the visual analog scale and the clinical post-traumatic neck score), radiological findings (angulation, translation, and disc height), and bone healing were assessed at 3, 6, 12, and 24 months.ResultsAll the patients were followed up successfully. There were no intra- or postoperative complications observed. Solid fusion was achieved in all cases by 6 months after surgery. The local kyphotic angle was corrected significantly with the mean preoperative 12.31 ± 2.96 degrees, initial postoperative −1.98 ± 1.62 degrees and the latest follow-up −1.72 ± 1.60 degrees respectively (P < 0.05).The translation was also corrected significantly with the mean preoperative 3.20 ± 1.16 mm, initial postoperative 0.97 ± 0.36 mm, and the latest follow-up 1.05 ± 0.34 mm respectively (P < 0.05). The mean visual analog scale and the clinical post-traumatic neck score improved significantly following surgery (P < 0.05).ConclusionsThis case series demonstrates that anterior C2/3 discectomy and interbody fusion with the cervical cage solely is effective and reliable in management of type II / IIA Hangman’s fracture with C2/3 disc injury when properly indicated.

Radiological Signs of Adjacent Segment Degeneration Patients with Cervical Spondylotic Radiculopathy Treated with Posterior Cervical Cages: Two-Year Follow-Up

BACKGROUND CONTEXT: Select patients with nerve compression and cervical radiculopathy secondary to spondylosis can be successfully treated with indirect posterior cervical decompression and fusion with posterior cervical cages. Cervical fusion may have an influence on adjacent segment degeneration (ASD). PURPOSE: The aim of this study was to assess radiological signs of ASD at 2 years follow-up in patients treated with posterior cervical cages for cervical spondylotic radiculopathy. STUDY DESIGN/SETTING: Retrospective evaluation of cervical radiographs. PATIENT SAMPLE: Fifty-three patients who underwent posterior cervical fusion with DTRAX cervical cages for cervical spondylotic radiculopathy were enrolled into the study. The lateral cervical X-ray images were taken in neutral position preoperatively and at 1 and 2 years postoperatively. OUTCOME MEASURES: The adjacent levels were evaluation consisted of measurements of:1) Proximal junctional kyphosis (PJK);2) Disc height ratio (DHR) – ratio of the disc height and the lower vertebrae height measured in the in the middle;3) Heterotopic ossification (HO) – none,!50%, O50 % , complete bridging of the disc;4) Kellgren and Lawrence Osteoarthritis Severity Grade (OSG).5) Neck Disability Index(NDI), Visual Analog Scale(VAS), and SF-12 Mental(MCS) and Physical Component Score(PCS). METHODS: The results were compared with ANOVA test, with p!0.05 considered as significant. ASD was defined as an increase of HO or OSG by 1 grade in new cases and by 2 grades if pre-existing disc degeneration was present before surgery (DDS). RESULTS: There were no revision surgeries at the operated level or at adjacent levels. Disc degeneration signs were present before surgery (DDS) in 21 patients in upper level and in 22 patients in lower level. In 2 patients there were new grade 1 ASD changes, 1 in level above and 1 in level below at 2 years postoperatively. In patients with pre-existing disc degeneration at the adjacent level, there were 0 cases of adjacent level degeneration progression of 2 grade or more. There were no significant changes in DHR and in PJK in all patients and in patients with ASD, however, there were tendency in patients with signs of ASD to decrease DHR in time. The mean PJK before surgery was -1.02 64.6 , 1 year after surgery -0.86 64.7 and 2 years after surgery was -0.59 65.4 ; p50.5342The mean DHR in all patients before surgery was 43.3 66.3 , 1 year after surgery 43.3 66.6 and 2 years after surgery was 43.1 66.8 ; p50.7290The mean DHR in ASD patients before surgery was 44.1 65.6 , 1 year after surgery 42.667.2 and 2 years after surgery was 40.9 67.8 ; p50.1836.The mean preop and 2-year scores were: NDI: 32.3 vs 9.1 (p!0.0001); VAS Neck Pain: 7.4 vs 2.6(p!0.0001); VAS Arm Pain: 7.4 vs 2.6 (p!0.0001); SF-12 PCS: 34.6 vs 43.6(p!0.0001) and SF-12 MCS: 40.8 vs 51.4 (p!0.0001). CONCLUSIONS: Indirect decompression and posterior cervical fusion using the DTRAX Cage may be an effective option in select patients with single level cervical radiculopathy. In patients treated with posterior cervical cage progression of disc degeneration is much more common on the basis of preoperative changes than new ASD. Posterior cervical fusion with cervical cage does not induce or accelerate adjacent segment degeneration in the great majority of patients (more than 1 score). Further evaluation to establish long-term incidence of ASD in patients treated with posterior cervical cage is needed. FDA DEVICE/DRUG STATUS: DTRAX Cervical Cage (Providence Medical Technology, Inc.) (Approved for this indication).

A systematic review of the use of expandable cages in the cervical spine.

Expandable vertebral body replacement cages (VBRs) have been widely used for reconstruction of the thoracolumbar spine following corpectomy. However, their use in the cervical spine is less common, and currently, no expandable cages on the market are cleared or approved by the US Food and Drug Administration for use in the cervical spine. The objective of this study was to perform a systematic review on the use of expandable cages in the treatment of cervical spine pathology with a focus on fusion rates, deformity correction, complications, and indications. A comprehensive Medline search was performed, and 24 applicable articles were identified and included in this review. The advantages of expandable cages include greater ease of implantation with less risk of damage to the end plate, less intraoperative manipulation of the device, and potentially greater control over lordosis. They may be particularly advantageous in cases with poor bone quality, such as patients with osteoporosis or metastatic tumors that have been radiated. However, there is a potential risk of overdistraction, which is increased in the cervical spine, their minimum height limits their use in cases with collapsed vertebra, and the amount of hardware in the expansion mechanism may limit the surface area available for fusion. The use of expandable VBRs are a valuable tool in the armamentarium for reconstruction of the anterior column of the cervical spine with an acceptable safety profile. Although expandable cervical cages are clearly beneficial in certain clinical situations, widespread use following all corpectomies is not justified due to their significantly greater cost compared to structural bone grafts or non-expandable VBRs, which can be utilized to achieve similar clinical outcomes.

Static and dynamic fatigue behavior of topology designed and conventional 3D printed bioresorbable PCL cervical interbody fusion devices

Recently, as an alternative to metal spinal fusion cages, 3D printed bioresorbable materials have been explored; however, the static and fatigue properties of these novel cages are not well known. Unfortunately, current ASTM testing standards used to determine these properties were designed prior to the advent of bioresorbable materials for cages. Therefore, the applicability of these standards for bioresorbable materials is unknown. In this study, an image-based topology and a conventional 3D printed bioresorbable poly(ε)-caprolactone (PCL) cervical cage design were tested in compression, compression–shear, and torsion, to establish their static and fatigue properties. Difficulties were in fact identified in establishing failure criteria and in particular determining compressive failure load. Given these limitations, under static loads, both designs withstood loads of over 650N in compression, 395N in compression–shear, and 0.25Nm in torsion, prior to yielding. Under dynamic testing, both designs withstood 5 million (5M) cycles of compression at 125% of their respective yield forces. Geometry significantly affected both the static and fatigue properties of the cages. The measured compressive yield loads fall within the reported physiological ranges; consequently, these PCL bioresorbable cages would likely require supplemental fixation. Most importantly, supplemental testing methods may be necessary beyond the current ASTM standards, to provide more accurate and reliable results, ultimately improving preclinical evaluation of these devices.

Outcomes in Anterior Cervical Discectomy with Anchored Intersomatic Cage

Introduction The anchored cervical intersomatic cages made in PEEK is a new promising alternative to anterior cervical locking plates with autologous iliac bone graft for anterior cervical discectomy and fusion. The advantage of such devices is the lack of profile and can provide the stability needed to achieve the arthrodesis. Objectives This study aims to evaluate the outcomes and fusion rates of the anchored intersomatic cage for achieving a stable arthrodesis and compare this result with established fixation methods. The hypothesis is that this device would be associated with low short-term complications and dysphagia, and could achieve a solid fusion and maintains the pain relief. Patients and Methods This was a comparative study in a single center, 50 patients were enrolled; 25 patients who underwent anterior cervical discectomy and fusion with autologous bone graft and locking plate and 25 patients with cervical intersomatic cage with heterologous bone graft. The clinical features Neck and Pain Disability Index; radicular pain, neck pain, and patient satisfaction were evaluated with VAS; and dysphagia scores were recorded preoperative and postoperative. Radiographs evaluated the height of intervertebral disc, implant position, and cervical Cobb angle. All patients had a minimum follow-up of 12 months. Results In all the patients, we found that a stable arthrodesis was achieved; the neck pain and radicular pain significantly reduces after surgery, without change after 1 year of follow-up. We do not have any chronic dysphagia and only one patient complained of minor dysphagia that improved in 2 weeks. Conclusions The cervical-anchored intersomatic cages are new surgical alternative with good functional outcomes, low-complication rates, and better postoperative patient comfort. We think that this is a preliminary assessment and prospective randomized trials are necessary to confirm this observation.

Multilevel Cervical Arthroplasty versus Multilevel Fusion in Three-Level Cervical Disc Disease (Clinical and Radiological Outcomes)

Introduction The surgical treatment for cervical disc disease increased in the last decade using different surgical techniques. The percentage of the patients being surgically treated for three-level cervical disc disease remains small therefore the optimal surgical approach for these patients remains the subject of discussion. Multiple cervical disc arthroplasty, multilevel fusion, and hybrid procedures are among the options using the anterior approach. The aim of the study was to compare the multilevel cervical disc arthroplasty and multilevel fusion and compare clinical as well as the radiographic results in patients treated for three-level symptomatic cervical degenerative disc disease 2 years after the surgery. Methods Overall, 23 patients with three-level symptomatic cervical degenerative disc disease were treated with complete anterior cervical discectomy and either with ProDisc-C disc arthroplasty or with fusion using Cervios chronoOS prostheses (ACDF) or standalone cervical cages. Overall 8 multilevel arthroplasty and 14 ACDF's procedures were performed. Clinical outcomes were assessed before and 12 and 24 months after the procedure using neurological examination, the neck disability index (NDI) and visual analogue scale (VAS) for neck and arm pain, with 15% improvement in NDI and 20% in VAS defined as clinically significant. Comparison between both groups (arthroplasty and fusion group) was based on clinical outcomes using neurological examination, VAS, NDI, and patient's satisfaction. Preoperative and postoperative ROMs (range of motion) were evaluated by measuring the lateral and flexion–extension radiographs. Results Both groups had a statistically significant improvement in NDI and VAS for neck and arm pain ( p &lt; 0.05), 2 years after the surgery and the arthroplasty group had a slightly better improvement according to NDI (71.4% of patients in the arthroplasty group achieved ≥ 15% improvement in NDI and 67.5 of patients in ACDF group). The arthroplasty group showed faster recovery of C2 to C7 range of motion. There was a statistically significant difference in the C2 to C7 ROM between the two groups at 12 and 24 months postoperatively ( p &lt; 0.05). The ROM of the arthroplasty group approached the preoperative value at 12 months however it decreased again at 24 months. Conclusions Disc arthroplasty can be an effective alternative in the surgical treatment for the multilevel cervical disc disease, preserving segmental motion after surgery and providing improvement in pain and functional outcome for the patients. The right surgical treatment for the three-level disc disease remains the subject of discussion and more long-term follow-up studies will be needed to determine the definitive treatment.

Evaluation of Subsidence in Stand-Alone Cervical Cage: Incidence, Risk Factors and Effects on Clinical and Radiological Picture

Background Data: Anterior Cervical Discectomy and Fusion is the gold standard for treating cervical degenerative disc disease associated with radiculopathy and/or myelopathy. When indicated, surgery can achieve neural tissuedecompression and biomechanical stabilization through bony fusion. One of the known complications of stand-alone anterior cervical cage is cage subsidence. Published literature however, contains mixed results in terms of rate of cagesubsidence, loss of lordosis and its clinical effects. Purpose: We report our experience in stand-alone anterior cervical cage, our subsidence rate and its effect on loss of lordosis and clinical picture Study Design: Retrospective clinical case study. Patients and Methods: we inserted seventy-two cervical cages (in fifty patients), who had Anterior Cervical Discectomy and Fusion using a stand-alone polyetheretherketone (PEEK) cage under our care. We recorded the self-reported Visual Analogue Score for arm and neck pain and measured the total intervertebral height/disc space or cage ratio, segmental Cobb angle, the distance between the anterior rim of the cage and the anterior vertebral body line, superior or inferior end plate violation and anterior or posterior cage migration on lateral X ray film preoperatively and on each follow up visit (day 1, 7-21 days, 3, and 6 months). Results: Our cage subsidence rate in the studied sample was 23.6% in 6 months (17 out of 62 cages subsided). We found a statistically significant correlation between immediate postoperative disc height and subsidence (the more distraction we applied to the disc space the more likely subsidence would happen). Cage subsidence did not increase the incidence of recurrence of radicular, myelopathic symptoms or neck pain although it resulted in significant loss of the segmental Cobb angle. Conclusions: Disc space over-distraction in stand-alone anterior cervical cage significantly increases the risk of subsidence. Subsidence significantly affects thesegmental Cobb angle but not the clinical outcome. (2015ESJ077)

Two-level anterior cervical discectomy and fusion using self-locking stand-alone polyetheretherketone cages with two anchoring clips placed in the upper and lower vertebrae, respectively

Anterior cervical discectomy and fusion (ACDF) is a widely accepted surgical procedure for the treatment of cervical degenerative disk diseases (CDDD). The purpose of our study was to investigate the reliability and efficacy of ACDF using self-locking stand-alone polyetheretherketone (PEEK) cages, with two anchoring clips placed in the upper and lower vertebrae, respectively. Twenty-six patients who underwent ACDF using a stand-alone PEEK cage packed with local osteophytes and cancellous allograft bone from January 2010 to January 2012 were enrolled in this study. Clinical findings were assessed using a visual analog scale (VAS), Japanese Orthopaedic Association (JOA) score, neck disability index (NDI), and Odom criteria. Intervertebral height and cervical fusion status were assessed on X-ray. Twenty-six patients underwent ACDF using a stand-alone PEEK cervical cage. All patients had a minimum 2 years of follow-up. The operative levels were C3/4, C4/5 in seven patients, C4/5, C5/6 in 13 patients, and C4/5, C6/7 in six patients. At 3 days, 6 months, and 2 years of follow-ups, the JOA scores were 10.41 ± 1.67, 13.78 ± 1.91, 14.42 ± 2.09, respectively, which was significantly higher (p < 0.01) than preoperative (7.34 ± 1.71), whereas VAS overall pain score was 4.35 ± 1.32, 1.73 ± 0.44, 1.32 ± 0.57, respectively, which was significantly lower (p < 0.01) than preoperative (8.01 ± 1.16). The NDI preoperatively was 33.94 ± 11.75, 23.53 ± 10.92 at 3 days postoperatively, 12.64 ± 8.36 at 6 months, and 10.74 ± 7.92 at 2 years of follow-ups. Intervertebral height was 5.99 ± 0.31 mm preoperatively, 8.70 ± 0.23 mm at 3 days, 8.34 ± 0.61 mm at 6 months, and 8.22 ± 0.35 mm at 2 years of follow-ups. According to Odom criteria, 10 patients (38.4%) presented with an excellent clinical outcome, 15 good (57.6%), 1 fair (3.8%), and no patient presented a poor outcome. Solid fusion was achieved in all patients (100%) at a mean time of 4.5 months. ACDF using a self-locking stand-alone PEEK cage with two anchoring clips placed in the upper and lower vertebrae, respectively, could be considered a safe and effective substitute for fusion in patients with two-level CDDD; it can effectively restore the intervertebral height, facilitate radiologic follow-up, cause few complications, and lead to satisfactory outcomes.

Three-dimensional printing for fabricating individualized endplate matching cervical cage

Objective To explore the feasibility of fabricating individualized cervical cage by three-dimensional printing and to verify the endplate matching of cage.Methods Ten fresh adult cervical specimens(5males and 5females,C1-C7)were subjected to CT-scan.The original Dicom data were fed into the Mimics software to create the fifth and sixth cervical vertebra and disc model,which was used to prepare individualized cervical cage using three-dimensional printing technique.All the specimens received anterior cervical discectomy and fusion in C5/6 disc,and CT-scan was taken postoperatively to access the endplate matching of cage.The matching degree was accessed at 36 points in each cage;excellent matching was defined as the distance between endplate and cage being less than 1mm,good as the distance being greater than or equal to 1mm while less than 2mm,and poor as the distance being greater than or equal to 2mm.Results Gross observation found that the cage well fit the veterbral disc,with satisfactory stability,with no cage being too large for implanting into the veterbral disc or cage dropout.Six(60%)specimens had excellent matching on all the 36 points.Three specimens had 14(3.89%)points matched good,including one with 6points and two with 4points each;the last specimen had 3(0.83%)points matched poor.A total of 343points(95.28%)had excellent matching in the present study.Conclusion Mimics software can well present the anatomical structures of cervical vertebral body and intervertebral disc,enabling individualized design of cervical cage.Three-dimensional printing can achieve rapid prototyping of individualized cage,which can well match the host endplate.

Is the radiographic subsidence of stand-alone cages associated with adverse clinical outcomes after cervical spine fusion? An observational cohort study with 2-year follow-up outcome scoring.

BackgroundThe stand-alone treatment of degenerative cervical spine pathologies is a proven method in clinical practice. However, its impact on subsidence, the resulting changes to the profile of the cervical spine and the possible influence of clinical results compared to treatment with additive plate osteosynthesis remain under discussion until present.MethodsThis study was designed as a retrospective observational cohort study to test the hypothesis that radiographic subsidence of cervical cages is not associated with adverse clinical outcomes. 33 cervical segments were treated surgically by ACDF with stand-alone cage in 17 patients (11 female, 6 male), mean age 56 years (33–82 years), and re-examined after eight and twenty-six months (mean) by means of radiology and score assessment (Medical Outcomes Study Short Form (MOS-SF 36), Oswestry Neck Disability Index (ONDI), painDETECT questionnaire and the visual analogue scale (VAS)).ResultsSubsidence was observed in 50.5% of segments (18/33) and 70.6% of patients (12/17). 36.3% of cases of subsidence (12/33) were observed after eight months during mean time of follow-up 1. After 26 months during mean time of follow-up 2, full radiographic fusion was seen in 100%. MOS-SF 36, ONDI and VAS did not show any significant difference between cases with and without subsidence in the two-sample t-test. Only in one type of scoring (painDETECT questionnaire) did a statistically significant difference in t-Test emerge between the two groups (p = 0.03; α = 0.05). However, preoperative painDETECT score differ significantly between patients with subsidence (13.3 falling to 12.6) and patients without subsidence (7.8 dropped to 6.3).ConclusionsThe radiological findings indicated 100% healing after stand-alone treatment with ACDF. Subsidence occurred in 50% of the segments treated. No impact on the clinical results was detected in the medium-term study period.

Biomechanical Assessment of Anchored Cervical Interbody Cages

A new anchored cervical interbody polyetheretherketone spacer was devised that uses only 2 integrated variable-angle screws diagonally into the adjacent vertebral bodies instead of the established device that uses 4 diagonal fixed-angle screws. To compare in vitro the stability provided by the new 2-screw interbody spacer with that of the 4-screw spacer and a 4-screw anterior plate plus independent polyetheretherketone spacer. Three groups of cadaveric specimens were tested with 2-screw anchored cage (n = 8), 4-screw anchored cage (n = 8), and standard plate/cage (n = 16). Pure moments (1.5 Nm) were applied to induce flexion, extension, lateral bending, and axial rotation while measuring 3-D motion optoelectronically. In all 3 groups, the mean range of motion (ROM) and lax zone were significantly reduced relative to the intact spine after discectomy and fixation. The 2-screw anchored cage allowed significantly greater ROM (P < .05) than the standard plate during flexion, extension, and axial rotation and allowed significantly greater ROM than the 4-screw cage during extension and axial rotation. The 4-screw anchored cage did not allow significantly different ROM or lax zone than the standard plate during any loading mode. The 2-screw variable-angle anchored cage significantly reduces ROM relative to the intact spine. Greater stability can be achieved, especially during extension and axial rotation, by using the 4-screw cage or standard plate plus cage.

Evaluation of biomechanical strength, stability, bioactivity, and in vivo biocompatibility of a novel calcium deficient hydroxyapatite/poly(amino acid) composite cervical vertebra cage

A new type of cervical vertebra cage was prepared using a novel composite, calcium deficient hydroxyapatite/poly(amino acid) (HA/PAA), and its mechanical properties, in vitro stability and bioactivity, and in vivo biocompatibility were characterized. The results showed that the axial compressive loads of the HA/PAA cage were in the range of 10058–10612 N and the lateral compressive loads were in the range of 1180–2363 N, and varied with the height of the cervical vertebra cages. After immersion in simulated body fluid (SBF) for 16 weeks, the axial compressive loads of the cage decreased from 10058 to 7131 N and the lateral compressive loads decreased from 1180 to 479 N. In addition, the weight loss decreased 6.01%, showing that HA/PAA composites had good stability during the incubation period. The pH value of SBF was also monitored during the whole soaking period; it fluctuated in the range of 6.9–7.4. Scanning electron microscope and energy dispersive spectrometer results showed the cage was bioactive with a new apatite layer attached on the surface. The histological evaluation revealed that new bone tissue bonded tightly with the surfaces of the implants, showing excellent biocompatibility. In conclusion, the HA/PAA cage showed sufficient strength, good stability, bioactivity, and biocompatibility, and has potential applications for clinical cervical vertebrae repair.

Comparison of outcomes and safety of using hydroxyapatite granules as a substitute for autograft in cervical cages for anterior cervical discectomy and interbody fusion.

After cervical discectomy, autogenic bone is packed into the cage to increase the rate of union between adjacent vertebral bodies, but donor site-related complications can still occur. In this study we evaluate the use of hydroxyapatite granules as a substitute for autograft for interbody fusion. From November 2008 to November 2011, 236 patients participated in this study. Peek cages were packed with autologous bone grafts taken from the iliac crest in 112 patients and hydroxyapatite (HA) granules in 124 patients. Patients were followed for 12 months. The patients' neurological signs, results, and complications were fully recorded throughout the procedure. Radiological imaging was done to assess the fusion rate and settling ratio. Formation of bony bridges at the third month was higher in the autograft group versus the granule group. However, there was no difference between both groups at the 12-month follow-up assessment. No difference (P> 0.05) was found regarding improvement in neurological deficit as well as radicular pain and recovery rate between the two groups. Interbody fusion cage containing HA granules proved to be an effective treatment for cervical spondylotic radiculopathy and/or myelopathy. Clinical and neurological outcome, radiographic measurement and fusion rate in cage containing HA are similar and competitive with autograft packed cages.

Acute monoplegia associated with non-traumatic intradural cervical disc herniation: A case report

Intradural disc herniation has been reported as a rare and particular type of intervertebral disc herniation. It occurs mostly in the lumbar spine, and rarely in the cervical or thoracic spine. Non-traumatic cervical intradural disc herniation is rare, with only 17 cases reported in English literature at the cervical region and can manifest itself by severe symptoms such as Brown-Sequard syndrome, transverse myelopathy and radiculopathy. We present a unique case of intradural cervical disc herniation only causing lower extremity monoplegia. To our knowledge, this is the first case described in the literature. The patient underwent microsurgical removal of the herniated disc via an anterior approach followed by interbody fixation using a cervical cage.

Development of a Low-Cost Polymethylmethacrylate Stand-Alone Cervical Cage: Technical Note

Stand-alone cervical cages aim to provide primary stability, yield solid fusion in the long-term course, and maintain physiologic alignment. However, many implants designed for these purposes fail in achieving these goals. Following implantation, relatively high rates of cage subsidence and failure of disc height maintenance may lead to cervical kyphosis and poor alignment of the cervical spine. At the same time, costs for cage implantation are relatively high compared with their unfavorable radiologic performance. Thus the aim of the study was to develop and test mechanically a low-cost polymethylmethacrylate (PMMA) cage with similar mechanical and procedural properties compared with a commercial polyetheretherketone (PEEK) cage. Following determination of the cage design, a casting mold was developed for the production of PMMA cages. Nine cages were produced and compared with nine PEEK cages using static compression tests for 0 and 45 degrees according to the recommendations of the American Society for Testing and Materials. Mean compressive yield strength, mean yield displacement, mean tensile strength, and mean stiffness were determined. At 0 degrees axial compression, the mean compressive yield strength, mean displacement, and mean tensile strength of the PMMA cage was significantly higher compared with the PEEK cage (p < 0.001). Stiffness of both implants did not differ significantly (p = 0.903). At 45 degrees axial compression, PEEK cages could not be investigated because slipping of the holding fixture occurred. Under these conditions, PMMA cages showed a mean compressive yield strength of 804.9 ± 60.5 N, a mean displacement of 0.66 mm ± 0.05 mm, a mean tensile strength of 7.92 ± 0.6 N/mm(2), and a mean stiffness of 1,228 ± 79.4 N/mm. The newly developed PMMA cage seems to show similar to superior mechanical properties compared with the commercial PEEK cage. Considering a preparation time of only 10 minutes and the low price for the PMMA material, the cost-benefit ratio clearly points to the use of the PMMA cage. However, clinical effectiveness has to be proven in a separate study.

Is the radiographic subsidence of stand-alone cages associated with adverse clinical outcomes after cervical spine fusion: an observational cohort study with 2-year follow-up outcome scoring

The stand-alone treatment of degenerative cervical spine pathologies is a proven method in clinical practice. However, its impact on subsidence, the resulting changes to the profile of the cervical spine and the possible influence of clinical results compared to treatment with additive plate osteosynthesis remain under discussion until present. This study was designed as a retrospective observational cohort study to test the hypothesis that radiographic subsidence of cervical cages is not associated with adverse clinical outcomes. 33 cervical segments were treated surgically by ACDF with stand-alone cage in 17 patients (11 female, 6 male), mean age 56 years (33–82 years), and re-examined after eight and twenty-six months (mean) by means of radiology and score assessment (Medical Outcomes Study Short Form (MOS-SF 36), Oswestry Neck Disability Index (ONDI), painDETECT questionnaire and the visual analogue scale (VAS)). Subsidence was observed in 50.5% of segments (18/33) and 70.6% of patients (12/17). 36.3% of cases of subsidence (12/33) were observed after eight months during mean time of follow-up 1. After 26 months during mean time of follow-up 2, full radiographic fusion was seen in 100%. MOS-SF 36, ONDI and VAS did not show any significant difference between cases with and without subsidence in the two-sample t-test. Only in one type of scoring (painDETECT questionnaire) did a statistically significant difference in t-Test emerge between the two groups (p = 0.03; α = 0.05). However, preoperative painDETECT score differ significantly between patients with subsidence (13.3 falling to 12.6) and patients without subsidence (7.8 dropped to 6.3). The radiological findings indicated 100% healing after stand-alone treatment with ACDF. Subsidence occurred in 50% of the segments treated. No impact on the clinical results was detected in the medium-term study period.

Empty Bladed PEEK Cage for Interbody Fusion after Anterior Cervical Discectomy.

Cervical disc herniation (CDH) can be treated using different anterior and posterior methods. Anterior cervical discectomy and fusion (ACDF) is currently gold standard and provides bony fusion and good clinical outcome. Recently many studies reported good clinical and radiological outcomes in cases who underwent anterior cervical discectomy (ACD) and reconstruction with empty cage. This study aimed to review our results after cervical microdiscectomy reconstructed with empty polyether ether ketone (PEEK) cage. Twenty-five cases with single level CDH who underwent microdiscectomy were included to this study. Reconstruction was performed using empty bladed cervical PEEK cages. Clinical (Visual analogue scale (VAS) and Odom scores) and radiological results (intervertebral disc and foraminal heights, mean cervical spine lordosis angle, and fusion rate) were reviewed one day and one year after surgery. There were 18 males and 7 females, aged between 25 and 54 years (mean: 40.8). Mean neck and arm VAS scores reduced from 2.9 to 1.4, and from 7.2 to 1.8, respectively. Odom scores were found to be 1.6 and 1.4 at 1st day and one year postoperatively, respectively. Subsidence was seen in three cases (12%). There was no significant change in heights of neural foramina and intervertebral discs, and no change in cervical spine lordosis, when compared postoperative 1st day and one year radiographs. Fusion was detected in 92% of cases in one year. Bladed cervical cages are safe with almost no risk of dislocation. Empty cages provide acceptable rates of fusion and subsidence.