Factors influencing cage subsidence in anterior cervical corpectomy and discectomy: a systematic review.

PURPOSE: Various factors have been examined in relation to cage subsidence risk, including cage material, cage geometry, bone mineral density, device type, surgical level, bone graft, and patient age. The present study aims to compare and synthesize the literature of both clinical and biomechanical studies to evaluate and present the factors associated with cage subsidence. METHODS: A comprehensive search of the literature from January 2003 to December 2021 was conducted using the PubMed and ScienceDirect databases by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Following the screening for inclusion and exclusion criteria, a total of 49 clinical studies were included. Correlations between clinical and biomechanical studies are also discussed. RESULTS: Patients treated with the cage and plate combination had a lower subsidence rate than patients with the stand-alone cage. Overall, Polyetheretherketone material was shown to have a lower subsidence rate than titanium and other materials. The subsidence rate was also higher when the surgery was performed at levels C5-C7 than at levels C2-C5. No significant correlation was found between age and cage subsidence clinically. CONCLUSIONS: Cage subsidence increases the stress on the anterior fixation system and may cause biomechanical instability. Severe cage subsidence decreases the Cobb angle and intervertebral height, which may cause destabilization of the implant system, such as screw/plate loosening or breakage of the screw/plate. Various factors have been shown to influence the risk of cage subsidence. Examining clinical research alongside biomechanical studies offers a more comprehensive understanding of the subject.

The improved bioactive n-HA/PA66 cage versus the PEEK cage in anterior cervical fusion: results from a 6-year follow-up and a case-matched study.

BACKGROUND: The nanohydroxyapatite/polyamide 66 (n-HA/PA66) cage, a bioactive nonmetal cage, is fabricated in a hollow cylindrical shape and has been widely used for decades with good clinical outcomes for anterior cervical fusion. However, there remain some radiological complications, such as a slightly high subsidence rate. To improve the clinical outcomes, the improved n-HA/PA66 cage now has been developed into a trapezoidal and wedge shape, a better biomechanical shape matching the cervical spine that is similar to that of the PEEK cage. However, there have been no long-term comparisons of the improved n-HA/PA66 cage and PEEK cage in anterior cervical reconstruction. METHODS: Fifty-eight patients who underwent single-level anterior cervical decompression and fusion (ACDF) with the improved n-HA/PA66 cage (n-HA/PA66 group) were matched with patients with the PEEK cage (PEEK group) by clinical presentation, segment, age and sex. All patients underwent a minimum of 6 years of follow-up. The radiographic parameters (cage subsidence, fusion status, cervical lordosis, and segmental sagittal alignment) and clinical parameters (10-point visual analogue scale, Neck Disability Index and Japanese Orthopedic Association scores) from patients were evaluated before surgery, immediately after surgery, and at the latest follow-up. RESULTS: The n-HA/PA66 and PEEK groups were well matched in terms of clinical presentation, segment, age, and sex at surgery. The n-HA/PA66 and PEEK cages had similar fusion rates at 6 months postoperatively (n-HA/PA66: 58.6% vs. PEEK: 51.7%, P = 0.455) and at the last follow-up (n-HA/PA66: 96.6% vs. PEEK: 93.1%, P = 0.402). The respective cage subsidence rates in the n-HA/PA66 and PEEK groups were 6.9 and 12.1% (P = 0.342). The correction of SA was similar between the groups at the final follow-up (n-HA/PA66: 4.29 ± 1.99 vs. PEEK: 3.99 ± 2.59 P = 0.464). There were no significant differences between the two groups in mean cervical lordosis, visual analogue scale scores of the neck and arm, NDI scores, JOA scores or patients' overall satisfaction at the final follow-up. CONCLUSION: After single-level ACDF, the improved n-HA/PA66 cage had similar excellent results in both radiological and clinical outcomes compared with the PEEK cage over 6 years of follow-up. According to these results, the improved n-HA/PA66 cage and the PEEK cage could be comparable for ACDF.

A comparison of contiguous two-level anterior cervical discectomy and fusion using a structural allograft versus a Polyetheretherketone (PEEK) cage: the results of a three-year follow-up.

BACKGROUND: Allografts and polyetheretherketone (PEEK) cages are the two most commonly used materials in anterior cervical discectomy and fusion (ACDF). However, their effectiveness in two-level ACDF remains controversial. The primary aim of this retrospective study was to compare the clinical and radiological outcomes of two-level ACDF with plate fixation using either a structural allograft or a PEEK cage. METHODS: From 2010 to 2015, 88 consecutive patients underwent two-level ACDF, of whom 53 received an allograft and 35 patients received a PEEK cage. All PEEK cages were filled with local autografts. All clinical outcomes were prospectively collected before and six months and two years after surgery. Clinical efficacy was evaluated using a visual analogue scale for neck pain and limb pain, the Neck Pain and Disability Score, the Neck Disability Index, the Neurogenic Symptom Score, and the Japanese Orthopedic Association score. Radiological outcomes were assessed preoperatively, immediately after surgery, and at the final follow-up. RESULTS: A preoperative comparison revealed no difference between the two patient groups in terms of age, sex, body mass index, smoking status, preoperative symptoms, operation level, or follow-up (mean = 42.8 months). No differences in the improvements in clinical outcomes were observed between the two groups. Both groups showed significant improvement in mean disc height, segmental height, and segmental lordosis postoperatively. The fusion rate for the PEEK cage was 100% at both levels, while the fusion rate for the allograft group was 98.1% at the cephalad level and 94.2% at the caudad level (p > 0.05). Subsidence at the cephalad level occurred in 22.9% (8/35) of segments in the PEEK group and 7.7% (4/52) of segments in the allograft group (p = 0.057). At the caudal level, a higher incidence of cage subsidence was noted in the PEEK group than in the allograft group [37.1% (13/35) versus 15.4% (8/52)] (p = 0.02). Overall, subsidence was noted in 30% (21/70) of the PEEK group and in 11% (12/104) of the allograft group (p <  0.05). CONCLUSION: The use of PEEK cages resulted in a higher rate of subsidence in two-level ACDF than the use of allografts. Two-level ACDF using either allografts or PEEK cages resulted in similar clinical outcomes, radiological improvements in alignment and fusion rates.

Implantation of an empty polyetheretherketone cage in anterior cervical discectomy and fusion: a prospective randomised controlled study with 2 years follow-up.

PURPOSE: To compare the clinical outcomes, radiographic results and fusion rate of ACDF between empty PEEK cages and PEEK cages packed with ß-tricalcium phosphate. METHODS: Forty-five patients were prospectively enrolled with cervical degenerative disc disease who requiring ACDF with a PEEK cage. 23 patients were randomised to the study group (empty cages) and 22 patients were in the control group (cages filled with ß-tricalcium phosphate). Both patient groups were fixed with a cervical locking plate. A CT scan was performed 12 months postoperatively and 24 months if not confirmed fused at 12 months to evaluate the status of fusion. Clinical status was evaluated using the Japanese Orthopaedic Association (JOA) score, the Oswestry Disability Index (ODI) and the Visual Analogue Scale (VAS). RESULTS: 46 levels (97.88%) in the study group and 44 levels (97.77%) in the control group were confirmed as fused at 24 months. There was no significant difference between the fusion rates observed in the study and control groups (p = 0.82). There was no significant difference in JOA, ODI, or VAS scores at 24 months follow-up. The results showed that the members of the non-fusion group tended to be older than the individuals in the fusion group at 12 months, but was not significant in statistics. CONCLUSIONS: Similar fusion rates and clinical outcomes were achieved when using ACDF with PEEK cages and instrumentation, regardless of whether the cage was filled with bone substitute at 24 months follow-up. Fusion rates improved over time and are comparable between both groups. These slides can be retrieved under Electronic Supplementary material.

A prospective clinical and radiographic 12-month outcome study of patients undergoing single-level anterior cervical discectomy and fusion for symptomatic cervical degenerative disc disease utilizing a novel viable allogeneic, cancellous, bone matrix (trinity evolution™) with a comparison to historical controls.

PURPOSE: This multicenter clinical study was performed to assess the safety and effectiveness of Trinity Evolution(®) (TE), a viable cellular bone allograft, in combination with a PEEK interbody spacer and supplemental anterior fixation in patients undergoing anterior cervical discectomy and fusion (ACDF). METHODS: In a prospective, multi-center study, 31 patients that presented with symptomatic cervical degeneration at one vertebral level underwent ACDF with a PEEK interbody spacer (Orthofix, Inc., Lewisville, TX, USA) and supplemental anterior fixation. In addition all patients had the bone graft substitute, Trinity Evolution (Musculoskeletal Transplant Foundation, Edison, NJ, USA), placed within the interbody spacer. At 6 and 12 months, radiographic fusion was evaluated as determined by independent radiographic review of angular motion (≤4°) from flexion/extension X-rays combined with presence of bridging bone across the adjacent endplates on thin cut CT scans. In addition other metrics were measured including function as assessed by the Neck Disability Index (NDI), and neck and arm pain as assessed by individual Visual Analog Scales (VAS). RESULTS: The fusion rate for patients using a PEEK interbody spacer in combination with TE was 78.6 % at 6 months and 93.5 % at 12 months. When considering high risk factors, 6-month fusion rates for patients that were current or former smokers, diabetic, overweight or obese/extremely obese were 70 % (7/10), 100 % (1/1), 70 % (7/10), and 82 % (9/11), respectively. At 12 months, the fusion rates were 100 % (12/12), 100 % (2/2), 100 % (11/11) and 85 % (11/13), respectively. Neck function, and neck/arm pain were found to significantly improve at both time points. No serious allograft related adverse events occurred and none of the 31 patients had subsequent additional cervical surgeries. CONCLUSIONS: Patients undergoing single-level ACDF with TE in combination with a PEEK interbody spacer and supplemental anterior fixation had a high rate of fusion success without serious allograft-related adverse events.

Influence of cervical bone mineral density on cage subsidence in patients following stand-alone anterior cervical discectomy and fusion.

PURPOSE: Anterior cervical discectomy and fusion (ACDF) is a common procedure for the treatment of cervical degenerative diseases. However, cage subsidence remains a frequent problem. We therefore investigated if cage design and site-specific bone mineral density (BMD) contribute to the rate and direction of subsidence following ACDF. METHODS: Patients were prospectively included and received two different cages (groups 1 and 2) using minimization randomization. The degree and direction of cage subsidence were determined using plain radiographs. Neck pain intensity on the visual analogue scale (VAS), the neck disability index (NDI), and the patient satisfaction index were recorded up to 12 months after surgery. RESULTS: 88 patients were analysed with a mean age of 53.7 ± 11.8 years. BMD values decreased in craniocaudal direction from 302.0 ± 62.2 to 235.5 ± 38.9 mg/cm(3). Both groups showed significant height gain after the operation (both p < 0.001), followed by height loss at 3 months (both p < 0.05) and at 3-12 months after the operation (both p > 0.05). Both groups showed improvement of VAS neck pain intensity (both p < 0.05) and NDI (both p < 0.05). The direction of cage subsidence was similar, no correlations were found between cage subsidence and BMD or various clinical parameters. CONCLUSIONS: Implant geometry of both cages and variations of the operative procedure promoted a relatively high degree of cage subsidence. Further studies are necessary to identify a relation of BMD and subsidence using optimized implant geometry and by controlling additional intraoperative variables.

Comparison of the effects of different artificial discs on hybrid surgery: A finite element analysis.

In recent years, artificial cervical discs have been used in intervertebral disc replacement surgery and hybrid surgery (HS). The advantages and disadvantages of different artificial cervical discs in artificial cervical disc replacement surgery have been compared. However, few scholars have studied the biomechanical effects of various artificial disc prostheses on the human cervical spine in HS which include the Anterior Cervical Discectomy and Fusion (ACDF) and Cervical Disc Arthroplasty (CDA). This study compared the biomechanical behavior of Mobi-C and Prestige LP in the operative and adjacent segments during two-level hybrid surgery. A three-dimensional finite element model of C2-C7 was first established and validated. Subsequently, clinical surgery was then simulated to establish a surgical model of anterior cervical fusion at the C4-C5 level. Mobi-C and Prestige-LP artificial disc prostheses were implanted at the C5-C6 level to create two hybrid models. All finite element models were fixed on the lower endplate of the C7 vertebra and subjected to a load of 73.6 N and different directions of 1 Nm torque on the odontoid process of the C2 vertebra to simulate human flexion, extension, lateral bending, and axial rotation. This paper compares the ROM, intervertebral pressure, and facet joint force after hybrid surgery with the intact model. The results show that compared with Prestige LP, Mobi-C can improve ROM of the replacement segment and compensate for the intervertebral pressure of the adjacent segment more effectively, but the facet joint pressure of the replacement segment may be higher.

Clinical and radiological outcomes of non-window-type bioactive glass-ceramic cage in single-level ACDF versus PEEK cage filled with autologous bone.

Bioactive glass-ceramic (BGC) cage is a substitute for polyether ether ketone (PEEK) cages in anterior cervical discectomy and fusion (ACDF). Only a few comparative studies exist using PEEK and non-window-type BGC cages (CaO-SiO2-P2O5-B2O3) in single-level ACDF. This study compared PEEK cages filled with autologous iliac bone grafts and BGC cages regarding clinical safety and effectiveness. A retrospective case series was performed on 40 patients who underwent single-level ACDF between October 2020 and July 2021 by a single orthopedic spine surgeon. The spacers used in each ACDF were a PEEK cage with a void filled with an autologous iliac bone graft and a non-window-type BGC cage in 20 cases. The grafts were compared pre-operatively and post-operatively at 6 weeks and 3, 6, and 12 months. Post-operative complications were investigated in each group. Clinical outcome was measured, including Visual Analog Scale (VAS) scores of neck and arm pains, Japanese Orthopedic Association score (JOA), and Neck Disability Index (NDI). Dynamic lateral radiographs were used to assess the inter-spinous motion (ISM) between the fusion segment and subsidence. The fusion status was evaluated using a computed tomography (CT) scan. Overall, 39 patients (19 and 20 patients in the PEEK and BGC groups, respectively) were recruited. Eighteen (94.7%) and 19 (95.0%) patients in the PEEK and BGC groups, respectively, were fused 12 months post-operatively, as assessed by ISM in dynamic lateral radiograph and bone bridging formation proven in CT scan. The PEEK and BGC groups showed substantial improvement in neck and arm VAS, JOA, and NDI scores. No substantial difference was found in clinical and radiological outcomes between the PEEK and BGC groups. However, the operation time was considerably shorter in the BGC group than in the PEEK group. In conclusion, a non-window-type BCG cage is a feasible substitute for a PEEK cage with an autologous iliac bone graft in single-level ACDF.

A novel nanohydroxyapatite/polyamide-66 cage for reducing the subsidence rate after single-level anterior cervical discectomy and fusion: a comparative study of 7-year follow-up.

BACKGROUND: A novel nanohydroxyapatite/polyamide-66 cage (n-HA/PA66 cage) with a horseshoe shape was designed to lower the subsidence rate of the traditional hollow cylindrical n-HA/PA66 cage. However, no studies have compared the incidence of subsidence in the two cages. The purpose of this study was to compare the long-term clinical and radiological outcomes of the novel n-HA/PA66 cage with the hollow cylindrical n-HA/PA66 cage after anterior cervical discectomy and fusion (ACDF) to treat single-level cervical degenerative disk disease (CDDD). METHODS: Fifty-two patients with novel n-HA/PA66 cages (Group A) and fifty-five patients with hollow cylindrical n-HA/PA66 cages (Group B) were included. The radiological parameters included intervertebral height (IH), C2-7 angle (C2-7a), segmental alignment (SA), subsidence rate, and fusion rate. The clinical outcomes were visual analog scale (VAS) scores, Japanese Orthopedic Association (JOA) scores, and patient satisfaction rates. RESULTS: The pre- and postoperative SA, C2-7a, and fusion rates of the patients in Groups A and B were similar. The preoperative and 6-month postoperative IHs in both groups were comparable. However, the final follow-up IH in Group B was significantly smaller than that in Group A (35.9 mm vs. 36.7 mm). The difference in the subsidence rates at the final follow-up between Group A (5.8%, 3/52) and Group B (18.2%, 10/55) was significant. The VAS score, JOA score, and patient satisfaction rate were not significantly different. CONCLUSIONS: The novel n-HA/PA66 cage had similar favorable SA, C2-7a, fusion rate, and clinical outcomes compared to the hollow cylindrical n-HA/PA66 cage for treating single-level ACDF. Moreover, the novel n-HA/PA66 cage achieved a lower subsidence rate and higher IH than the hollow cylindrical n-HA/PA66 cage at the final follow-up.

A Comparison of Corpectomy ACDF Hybrid Procedures with Nano-Hydroxyapatite/Polyamide 66 Cage and Titanium Mesh Cage for Multi-level Degenerative Cervical Myelopathy: A Stepwise Propensity Score Matching Analysis.

OBJECTIVE: Previous studies have found satisfactory clinical results with the nano-hydroxyapatite/polyamide 66 (n-HA/PA66) cage to reconstruct the stability of anterior cervical column. However, studies evaluating the long-term outcomes of the n-HA/PA66 cage in multi-level degenerative cervical myelopathy (MDCM) have not been reported. This study aims to compare the outcomes of corpectomy anterior cervical discectomy and fusion (ACDF) hybrid procedures between the n-HA/PA66 cage and titanium mesh cage (TMC) to treat MDCM. METHODS: After the screening for eligibility, this retrospective study involved 90 patients who underwent corpectomy ACDF hybrid (CACDFH) procedure from June 2013 to June 2018. The CACDFH procedure is the combination of ACDF and anterior cervical corpectomy and fusion (ACCF). According to the cage utilized, we categorized patients into a n-HA/PA66 cage group and a TMC group. Then, stepwise propensity score matching (PSM) was performed to maintain comparable clinical data between groups. All the patients were followed up ≥4 years and the longest follow-up time was 65.43 (±11.49) months. Cage subsidence, adjacent segment degeneration (ASD), segmental height (SH), segmental angle (SA), cervical lordosis (CL), and clinical data (visual analogue scale [VAS] and Japanese Orthopaedic Association [JOA] score) was evaluated preoperatively, at 1 week, and at the final surgery follow-up. The independent student's t test and chi-square test were applied to compare the differences between groups. RESULTS: Through PSM analysis, 25 patients from the n-HA/PA66 group were matched to 25 patients in the TMC group. The occurrence of ASD was 16.0% (4/25) in the n-HA/PA 66 group, which was significantly less than in the TMC group at 44.0% (11/25) (p = 0.031). Moreover, the cage subsidence rate was significantly higher in the TMC group as compared to the n-HA/PA 66 group (40.0% vs. 12.0%, p = 0.024). But there was no significant difference in SH, SA, and CL at any time after surgery as determined through follow-up. The VAS and JOA scores significantly improved in both groups at 3 months postoperative and at final follow-up. However, there were no significant differences in the VAS and JOA score at any time between the two groups in preoperative (p > 0.05). CONCLUSION: The n-HA/PA66 cage is associated with lower rate of cage subsidence and ASD than the TMC in the treatment of MDCM. The n-HA/PA66 cage could be superior to the TMC in corpectomy ACDF hybrid procedures.

Comparison between Three-Dimensional Printed Titanium and PEEK Cages for Cervical and Lumbar Interbody Fusion: A Prospective Controlled Trial.

OBJECTIVES: The three-dimensional printing titanium (3DPT) cage with excellent biomechanical properties and osseointegration capabilities has been initially used in spinal fusion, while the polyetheretherketone (PEEK) cage, a bioinert material device, has been a widely used for decades with relatively excellent clinical outcomes. This study was performed to investigate the early radiographic and clinical outcomes of 3DPT cage versus PEEK cage in patients undergoing anterior cervical discectomy and fusion (ACDF) and transforaminal lumbar interbody fusion (TLIF). METHODS: This prospective controlled trial, from December 2019 to June 2022, included patients undergoing ACDF and TLIF with 3DPT cages and compared them to patients using PEEK cages for treating spinal degenerative disorders. The outcome measures included radiographic parameters (intervertebral height [IH], subsidence, fusion status, and bone-cage interface contact) and clinical outcomes (Japanese Orthopaedic Association [JOA], Neck Disability Index [NDI], Oswestry Disability Index [ODI], Short Form 12-Item Survey [SF-12], Visual Analog Scale [VAS], and Odom's criteria). Student's independent samples t test and Pearson's chi-square test were used to compare the outcome measures between the two groups before surgery and at 1 week, 3 and 6 months after surgery. RESULTS: For the patients undergoing ACDF, the 3DPT (18 patients/[26 segments]) and PEEK groups (18 patients/[26 segments]) had similar fusion rates at 3 months and 6 months follow-up (3 months: 96.2% vs. 83.3%, p = 0.182; 6 months: 100% vs. 91.7%, p = 0.225). The subsidence in the 3DPT group was significantly lower than that in the PEEK group (3 months: 0.4 ± 0.2 mm vs. 0.9 ± 0.7 mm p = 0.004; 6 months: 0.7 ± 0.3 mm vs. 1.5 ± 0.8 mm, p < 0.001). 3DPT and PEEK cage all achieved sufficient contact with the cervical endplates. For the patients undergoing TLIF, the 3DPT (20 patients/[26 segments]) and PEEK groups (20 patients/[24 segments]) had no statistical difference in fusion rate (3 months: 84.6% vs. 58.3%, p = 0.059; 6 months: 92.3% vs. 75%, p = 0.132). The subsidence was lower than that in the PEEK group without significantly difference (3 months: 0.9 ± 0.7 mm vs.1.2 ± 0.9 mm p = 0.136; 6 months: 1.6 ± 1.0 mm vs. 2.0 ± 1.0 mm, p = 0.200). At the 3-month follow-up, the bone-cage interface contact of the 3DPT cage was significantly better than that of the PEEK cage (poor contact: 15.4% vs. 75%, p < 0.001). The values of UAR were higher in the 3DPT group than in the PEEK group during the follow-up in cervical and lumbar fusion, there were more statistical differences in lumbar fusion. There were no significant differences in the clinical assessment between 3DPT or PEEK cage in spinal fusion. CONCLUSION: The 3DPT cage and PEEK cage can achieve excellent clinical outcomes in cervical and lumbar fusion. The 3DPT cage has advantage in fusion quality, subsidence severity, and bone-cage interface contact than PEEK cage.

Subsidence Performance of the Bioactive Glass-Ceramic (CaO-SiO2-P2O5-B2O3) Spacer in Terms of Modulus of Elasticity and Contact Area: Mechanical Test and Finite Element Analysis.

OBJECTIVE: The objective of this study is to evaluate the subsidence performance of a bioactive glass-ceramic (CaO-SiO2-P2O5-B2O3) spacer in terms of its modulus of elasticity and contact area using mechanical tests and finite element analysis. METHODS: Three spacer three-dimensional models (Polyether ether ketone [PEEK]-C: PEEK spacer with a small contact area; PEEK-NF: PEEK spacer with a large contact area; and Bioactive glass [BGS]-NF: bioactive glass-ceramic spacer with a large contact area) are constructed and placed between bone blocks for compression analysis. The stress distribution, peak von Mises stress, and reaction force generated in the bone block are predicted by applying a compressive load. Subsidence tests are conducted for three spacer models in accordance with ASTM F2267. Three types of blocks measuring 8, 10, and 15 pounds per cubic foot are used to account for the various bone qualities of patients. A statistical analysis of the results is conducted using a one-way Analysis of variance and post hoc analysis (Tukey's Honestly Significant Difference) by measuring the stiffness and yield load. RESULTS: The stress distribution, peak von Mises stress, and reaction force predicted via the finite element analysis are the highest for PEEK-C, whereas they are similar for PEEK-NF and BGS-NF. Results of mechanical tests show that the stiffness and yield load of PEEK-C are the lowest, whereas those of PEEK-NF and BGS-NF are similar. CONCLUSIONS: The main factor affecting subsidence performance is the contact area. Therefore, bioactive glass-ceramic spacers exhibit a larger contact area and better subsidence performance than conventional spacers.

Comparison of Outcomes Between Cage Materials Used for Patients Undergoing Anterior Cervical Discectomy and Fusion with Standalone Cages: A Systematic Review and Meta-Analysis.

INTRODUCTION: Interbody cages are currently being used to address diseases of the vertebra requiring surgical stabilization. Titanium cages were first introduced in 1988. Polyetheretherketone (PEEK) cages are used frequently as one of the alternatives to titanium cages in current practice. This study aimed to compare available cage materials by reviewing the surgical and radiographic outcomes following anterior cervical discectomy and fusion. METHODS: A comprehensive search of several electronic databases was conducted following the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. Baseline characteristics, operative outcomes, arthrodesis rates, subsidence rates, and complications were collected from included studies. Collected outcomes were further stratified according to the procedure type, the number of levels operated, and graft used to compare cage materials. RESULTS: Following the screening for inclusion criteria, a total of 37 studies with 2363 patients were included. The median age was 49.5 years and the median follow-up was 26 months. Overall, no significant differences were found between PEEK and titanium cages regarding fusion, neurologic deficit, subsidence rates, or "good and excellent" outcome according to Odom criteria. However, the standalone comparison between PEEK, titanium, and poly-methyl-methacrylate (PMMA) cages showed a significantly lower fusion rate for PMMA (PEEK: 94%, PMMA: 56%, titanium: 95%, P < 0.01). CONCLUSIONS: In the present systematic review and meta-analysis, a comparison of the long-term patient-reported and the radiographic outcomes associated with the use of titanium and PEEK, intervertebral body cages showed similar findings. However, there were significantly lower fusion rates for PMMA cages when using a standalone cage without graft material.

Characterizing dysphagia after spinal surgery.

Context/Objective: Dysphagia after spinal surgery is well recognised. Characteristics of post-operative dysphagia are not well defined. This study explored severity, longevity, and physiological characteristics of dysphagia.Design: Prospective, observational study.Setting: Tertiary urban hospital.Participants: Two-hundred fifty patients consecutively receiving spinal surgery.Interventions: Demographic and clinical information were collected. Flexible endoscopic evaluation of swallowing (FEES) and videofluoroscopic study of swallowing (VFSS) recordings were analyzed.Outcomes Measures: FEES recordings were analyzed using three validated symptom scales. VFSS recordings were analyzed using 10 objective digital measures of timing, displacement and symptoms.Results: Of 250 patients, 75 were referred for swallowing assessment. Sixty-two received FEES and 11 VFSS. Patients with anterior approach surgery for cervical level injuries represented 85% of referrals (n = 64). Secretion accumulation, aspiration and residue scores decreased significantly within 2 months for most patients. For those with persisting dysphagia, objective VFSS measures demonstrated significant impairments in pharyngeal constriction, hyoid displacement and pharyngoesophageal segment opening with corresponding residue and aspiration scores. By 6 months, all patients had returned to a regular diet except three patients following anterior cervical discectomy and fusion (ACDF) who remained nil by mouth with severe physiological impairments.Conclusions: A quarter of patients following spinal surgery present with dysphagia. For most, symptoms decrease significantly by 2 months and patients return to normal diets. Early screening of dysphagia is critical to avoid secondary complications and prolonged hospitalizations. For some, significant pharyngeal impairments persist and high-quality case series exploring efficacy of rehabilitation programmes are needed.

Integral Fixation Titanium/Polyetheretherketone Cages for Cervical Arthrodesis: Evolution of Cage Design and Early Radiological Outcomes and Fusion Rates.

OBJECTIVE: To evaluate the initial outcomes of a composite cage with integral fixation using the Redmond titanium (Ti)/polyetheretherketone (PEEK) anterior cervical discectomy and fusion (ACDF) device. METHODS: Data from 50 consecutive patients were prospectively collected from a single senior surgeon cohort. All cages were between 5 and 8 mm in height, and were packed with supercritical CO2 sterilized allograft. Patients were followed up for a minimum of 6 months, and implant complications were assessed. RESULTS: From the original cohort, three were unavailable for follow-up. Forty-seven patients with a total of 58 operative levels were observed for a mean of 7.9 months. A fusion rate of 96% was achieved. Good to excellent outcomes were seen in 92% of patients. There were no cases of implant Ti/PEEK delamination or implant failure, with excellent early fusion rates using supercritical CO2 allograft. CONCLUSIONS: The present study demonstrates the development of a composite ACDF cage design that is a safe and effective treatment option with the potential for early osseointegration and interbody fusion. Supercritical CO2 sterilized allograft was an effective graft material supporting fusion.

Is stand alone PEEK cage the gold standard in multilevel anterior cervical discectomy and fusion (ACDF)? Results of a minimum 1-year follow up.

INTRODUCTION: This study was designed to evaluate the clinical and radiologic results of stand-alone synthetic polyetheretherketone (PEEK) cages for two- or three-level anterior cervical discectomy and fusion (ACDF), with a focus on subsidence. MATERIALS AND METHODS: We retrospectively reviewed a total of 68 patients who underwent two- or three-level ACDF with a stand-alone PEEK cage between April 2005 and August 2016. Radiologic parameters were assessed on lateral radiographs, and fusion was assessed on computed tomography scans. For the evaluation of clinical outcomes, visual analogue scale, neck disability index, and modified Japanese Orthopedic Association scores were measured. RESULTS: Among the total of 68 patients with a total of 144 segments, ACDF at two and three levels was performed in 60 and 8 patients, respectively, with a mean follow-up duration of 27.6 months. The overall fusion rate was 81.3% (117 of 144 segments), and subsidence occurred in 63 segments (43.8%) at the last follow-up. There was no statistically significant difference between the subsidence group and the nonsubsidence group in terms of fusion rate, radiologic outcomes, and clinical outcomes (p > .05). CONCLUSION: Subsidence might be an inevitable course and only a radiologic phenomenon with no effect on the clinical and radiologic outcomes of the use of stand-alone cages.

Fivefold higher rate of pseudarthrosis with polyetheretherketone interbody device than with structural allograft used for 1-level anterior cervical discectomy and fusion.

In BriefThe authors examined fusion rates after single-level anterior cervical discectomy and fusion, comparing use of a structural allograft with use of polyetheretherketone (PEEK) interbody devices packed with bone graft. The results demonstrate superior results of structural allograft in terms of arthrodesis rates and reoperation rates. Currently, reimbursement rates substantially favor the use of PEEK and other synthetic devices, which the authors believe should be changed based on the results of this study.

Origins of eponymous instruments in spine surgery.

Every day, spine surgeons call for instruments named after surgical pioneers. Few know the designers or the histories behind their instruments. In this paper the authors provide a historical perspective on the Penfield dissector, Leksell rongeur, Hibbs retractor, Woodson elevator, Kerrison rongeur, McCulloch retractor, Caspar pin retractor system, and Cloward handheld retractor, and a biographical review of their inventors. Historical data were obtained by searching the HathiTrust Digital Library, PubMed, Google Scholar, Google Books, and Google, and personal communications with relatives, colleagues, and foundations of the surgeon-designers. The authors found that the Penfield dissectors filled a need for delicate tools for manipulating the brain and that the Leksell rongeur increased surgical efficiency during war-related laminectomies. Hibbs' retractor facilitated his spine fusion technique. Woodson was both a dentist and a physician whose instrument was adopted by spine surgeons. Kerrison rongeurs were developed in otology to decompress bone near the facial nerve. The McCulloch, Caspar, and Cloward retractors helped improve exposure during the emergence of new techniques, i.e., microdiscectomy and anterior cervical discectomy and fusion. The histories behind these eponymous instruments remind us that innovation sometimes begins in other specialties and demonstrate the role of innovation in improving patient care.

Comparison of allograft and polyetheretherketone (PEEK) cage subsidence rates in anterior cervical discectomy and fusion (ACDF).

Structural allografts and PEEK cages are commonly used interbody fusion devices in ACDF. The subsidence rates of these two spacers have not yet been directly compared. The primary aim of this study was to compare the subsidence rate of allograft and PEEK cage in ACDF. The secondary aim was to determine if the presence of subsidence affects the clinical outcome. We reviewed 67 cases (117 levels) of ACDF with either structural allograft or PEEK cages. There were 85 levels (48 cases) with PEEK and 32 levels (19 cases) with allograft spacers. Anterior and posterior disc heights at each operative level were measured at immediate and 6months post-op. Subsidence was defined as a decrease in anterior or posterior disc heights >2mm. NDI of the subsidence (SG) and non-subsidence group (NSG) were recorded. Chi-square test was used to analyze subsidence rates. T-test was used to analyze clinical outcomes (α=0.05). There was no statistically significant difference between subsidence rates of the PEEK (29%; 25/85) and allograft group (28%; 9/32) (p=0.69). Overall mean subsidence was 2.3±1.7mm anteriorly and 2.6±1.2mm posteriorly. Mean NDI improvement was 11.7 (from 47.1 to 35.4; average follow-up: 12mos) for the SG and 14.0 (from 45.8 to 31.8; average follow-up: 13mos) for the NSG (p=0.74). Subsidence rate does not seem to be affected by the use of either PEEK or allograft as spacers in ACDF. Furthermore, subsidence alone does not seem to be predictive of clinical outcomes of ACDF.

Subsidence after single-level anterior cervical fusion with a stand-alone cage.

To investigate the risk factors for subsidence in patients treated with stand-alone anterior cervical discectomy and fusion (ACDF) using polyetheretherketone (PEEK) cages for single-level degenerative cervical disease. Seventy-seven consecutive patients who underwent single-level stand-alone ACDF with a PEEK cage between 2005 and 2012 were included. Subsidence was defined as a decrease in the interbody height of more than 3mm on radiographs at the 1-year follow-up compared with that in the immediate post-operative image. Patients were divided into the subsidence and non-subsidence groups. The following factors were investigated in relation to the occurrence of subsidence: age, pre-operative overall cervical sagittal angle, segmental angle of the operated level, interbody height, cage height, cage devices and cage location (distance between anterior margin of the body endplate and that of the cage). The clinical outcomes were assessed with visual analog scale, modified Japanese Orthopedic Association score and neck disability index. Twenty-six out of the 77 (33.8%) patients had radiological signs of cage subsidence. Solid fusion was achieved in 25 out of the 26 patients (96.2%) in the subsidence group and in 47 out of the 51 patients (92.2%) in the non-subsidence group. More than 3mm distance between anterior margin of the vertebral body and that of the cage was significantly associated with subsidence (p<0.05). However, subsidence did not correlate with fusion rate or clinical outcomes. Cage location was the only significant risk factor. Therefore, cage location should be taken into consideration during stand-alone ACDF using PEEK cages.