Short-term comparison of cervical fusion with static and dynamic plating using computerized motion analysis

Evaluation of bony fusion after anterior cervical discectomy: a systematic literature review and meta-analysis

Significant variability exists in reported fusion rates in the cervical spine after anterior discectomy. Here we review fusion assessment methods, timing of fusion with various intervertebral devices, and examine correlations with clinical outcomes. PubMed, Medline, Embase, Web of Science, Cochrane Library, and Emcare were searched on December 9 2024 for studies involving 1- or 2-level anterior cervical discectomy with quantitative fusion assessment via CT or X-ray. A meta-analysis was conducted using a random-effects model to pool fusion rates and their 95% confidence intervals (CIs) at different follow-up points, for different cage types and different cut-off values evaluating fusion. Sixty-four included studies evaluated 5633 patients. Pooled fusion rates increased over time: 55.6% (95% CI: 43.5%, 67.2%) of patients demonstrated fusion at three months, 74.4% (67.6%, 80.1%) at six months, 88.1% at 12 months (85.1%, 90.6%), and 91.8% (89.1%, 93.9%) at 24 months. Subgroup analysis revealed variation in fusion rates depending on cage type, with titanium cages yielding slightly higher rates at all follow-up times. Sensitivity analysis with fusion criteria showed that a cut-off value < 2 mm for interspinous distance yielded lower fusion rates than the cut-off < 2° for Cobb angle at 6 (70% vs. 77.3%), 12 (83.9% vs. 91.1%) and 24 months (89.5% vs. 91.7%). Results on the correlation between fusion and clinical outcomes were inconsistent. Fusion rates improved over time, approaching 56% at 3 months and 90% at 12 months. Notably, to alleviate heterogeneity across studies, there is a dire need to harmonize reporting guidelines in future research.

Diagnosis of spine pseudoarthrosis based on the biomechanical properties of bone

BACKGROUND CONTEXT

Failure to fuse following anterior cervical discectomy and fusion (ACDF) may result in symptomatic pseudoarthrosis. Traditional diagnosis involves computerized tomography to detect bridging bone and/or flexion-extension radiographs to assess whether segmental motion is above specific thresholds; however, there are currently no well-validated diagnostic tests. We propose a biomechanically rational approach to achieve a reliable diagnostic test for pseudoarthrosis.

PURPOSE

Develop and test a biomechanically based approach to the diagnosis of pseudoarthrosis.

STUDY DESIGN

Literature review, development of theory, re-analysis of a previously published study with surgical exploration as the gold-standard, and retrospective analysis of pooled studies to understand time to fusion.

METHODS

Fully automated methods were used to measure disc space strains (change in disc space height divided by initial height). Measurement error combined with the reported failure strain of trabecular bone led to a proposed strain threshold for diagnosis of pseudoarthrosis following ACDF. We reanalyzed previously reported flexion-extension radiographs for asymptomatic volunteers to assess whether flexion-extension radiographs, in the absence of fusion surgery, can be expected to provide sufficient stress on motion segments to allow for reliable strain-based fusion assessment. The sensitivity and specificity of strain- and rotation-based pseudoarthrosis diagnosis were assessed by reanalysis of previously reported post-ACDF flexion-extension radiographs, where intraoperative fusion assessments were also available. Finally, we assessed changes in strain over time using 9,869 flexion-extension radiographs obtained 6 weeks to 84 months post-ACDF surgery from 1,369 patients.

RESULTS

The estimated error in automated measurement of disc space strain from radiographs was approximately 3%, and the reported failure strain of bridging bone was less than 2.5%. On that basis, we propose a 5% strain threshold for pseudoarthrosis diagnosis. Reanalysis of a study in which intraoperative fusion assessments were available revealed 67% sensitivity and 82% specificity for strain-based diagnosis of pseudoarthrosis, which was comparable to rotation-based diagnosis. Analysis of post-ACDF flexion-extension radiographs revealed rapid strain reduction for up to 24 months, followed by a slower decrease for up to 84 months. When rotation is less than 2 degrees, the strain-based diagnosis differed from the rotation-based diagnosis in approximately 14% of the cases.

CONCLUSIONS

We propose steps for standardizing diagnosis of pseudoarthrosis based on the failure strain of bone, measurement error, and retrospective data. These steps include obtaining high-quality flexion-extension studies, the application of proposed diagnostic thresholds, and the use of image stabilization for conclusive diagnosis, when motion is near thresholds. The necessity for an accurate diagnosis with minimal radiation exposure underscores the need for further optimization and standardization in diagnosing pseudoarthrosis following ACDF surgery.

CLINICAL SIGNIFICANCE

In a symptomatic postspine fusion patient, it is important to diagnose or rule-out pseudoarthrosis. There are currently no well-validated diagnostic tests for this condition. Incorporating strain-based intervertebral motion analysis into the diagnosis could lead to a standardized and validated test for detecting spine pseudoarthrosis.

Is the anterior cervical dynamic plate fixation better than the anterior static plate fixation: a retrospective review with over 5 years follow-up

BACKGROUND

To compare the clinical and radiologic outcomes after anterior cervical dynamic or static plate fixation for short segment cervical degenerative disc diseases (DDD) for more than 5 years.

METHODS

Sixty-four patients who underwent anterior cervical one level discectomy or corpectomy with an anterior cervical plate system were followed for an average of 6.8 years for clinical and radiographic outcomes. Among the sixty-four patients, thirty-eight patients were fixed with a static plate (ORION and CSLP plate system) and the other twenty-six patients were fixed with a dynamic plate (ABC plate). Radiographic data were collected included the global sagittal alignment of the cervical spine (C2-C7), the local height and angle of the operated level pre-operatively, postoperatively and at last follow-up. A clinical assessment was performed at pre-operatively, three months postoperatively and final follow-up using the Japanese Orthopedic Association (JOA) /Visual Analogue Score(VAS)/ Neck Disablility Index(NDI) scoring system.

RESULTS

The mean follow-up time was 6.8 years. At final review, there were two cases of suspicious pseudarthrosis which were from ABC plate fixation group while the other cases all gained solid fusion. The height of fusion segment gained significantly improvement for both dynamic and static plate group post-operation, and all groups demonstrated a significant loss in height postoperatively. Generally, for the one level ACDF group, the height decrease was 0.5 mm for static plate and 1.6 mm for dynamic group which was significantly different(p < 0.05). And for one level ACCF group, this type of difference was not seen in which decreasing was 1.7 mm for static group and 1.8 mm for dynamic group. Segmental lordosis of the fusion segments was increased significantly both post-operation and final follow-up than before-operation for both one and two segments fusion. Global cervical lordosis from C2-C7 was increased in the early postoperative period in all groups, and at final follow-up the total lordosis was still getting better compared with early postoperative period, but this increase was not statistically significant. Clinical assessment of JOA/NDI showed that there was significantly improvement 3-month post-operation compared with pre-operation, and the score could get a slight further improvement at the final follow-up.

CONCLUSION

Our study demonstrated a statistically similar fusion rate between dynamic and static cervical plate fixation. However, the height gained with static plate fixation for single segment disease was maintained better than with dynamic plate fixation and there was no difference between JOA outcome scores between groups. Despite the reported improved biomechanics of dynamic plate fixation, further research needs to be done to show the clinical advantage of dynamic plate fixation.

Dynamic Radiographs Are Unreliable to Assess Arthrodesis Following Cervical Fusion: A Modeled Radiostereometric Analysis of Cervical Motion

STUDY DESIGN

In vitro study.

OBJECTIVE

The purpose of the present study was to utilize an idealized cervical spine model to determine whether the parallax effect or changes in the position of the spine relative to the x-ray generator influence intervertebral motion parameters on dynamic cervical spine radiographs.

SUMMARY OF BACKGROUND DATA

The utility of flexion-extension radiographs in clinical practice remains in question due to poor reliability of the parameters utilized to measure motion.

MATERIALS AND METHODS

A cervical spine model with tantalum beads inserted into the tip of each spinous process was utilized to measure interspinous process distance (IPD) on plain radiographs. The model was then manipulated to alter the generator angle and generator distance, and the IPD was measured. The impact of individual and combined changes in these parameters on IPD was assessed. Multivariate analysis was performed to identify independent drivers of variability in IPD measurements.

RESULTS

Isolated changes in the generator distance and generator angle and combined changes in these parameters led to significant changes in the measured IPD at each intervertebral level in neutral, flexion, and extension, which, in many instances, exceeded an absolute change of >1 mm or >2 mm. Multivariate analysis revealed that generator distance and generator angle are both independent factors impacting IPD measurements that have an additive effect.

CONCLUSIONS

In an idealized cervical spine model, small clinically feasible changes in spine position relative to the x-ray generator produced substantial variability in IPD measurements, with absolute changes that often exceeded established cutoffs for determining the presence of pathologic motion across a fused segment. This study further reinforces that motion assessment on dynamic radiographs is not a reliable method for determining the presence of an arthrodesis unless these sources of variability can be consistently eliminated.

LEVEL OF EVIDENCE

3.

Finite element analysis of the effect of anterior dynamic plating on two-level anterior cervical discectomy fusion biomechanics

BACKGROUND

Limitations of anterior cervical discectomy and fusion (ACDF) relate to mechanical failure of the construct after recurring subsidence and migration. This study aims to evaluate the effect of the maximum rotation of variable angle screws on the range of motion (ROM), cage migration, and subsidence.

METHODS

Five finite element (FE) models were developed from a C2-C7 cervical spine model. The first model was an intact C2-C7 spine model, and the second model was an altered C2-C7 model with C4-C6 cage insertion and a 2-level static plate. The other three models were altered C2-C7 models with the same C4-C6 cage insertion and a 2-level dynamic plate.

RESULTS

ROM of C4-C6 in the static plate model was reduced by about 14º from the intact model, while only reduced by about 9^o in dynamic plate models. The maximum migration and subsidence at the cage-endplate interface in the dynamic plate models were lower than that in the static plate model under all moments. The von-Mises stress of the C3-C4 and C6-C7 discs in the dynamic plate models was lower than that in the static plate model.

CONCLUSION

Results indicate dynamic plating has promising potential (higher ROM and lower von Mises stress of discs) for stabilization in multilevel ACDF than static plate, though both dynamic plate and static plate has lower ROM than the intact model. Lower screw rotational angle has superior biomechanical performance (lower migration and subsidence) to higher rotational angle in multilevel applications regardless of loading.

Does Dynamic Anterior Plate Fixation Provide Adequate Stability for Traumatic Subaxial Cervical Spine Fractures at Mid-Term Follow-Up?

Background: It remains questionable if the treatment of cervical fractures with dynamic plates in trauma surgery provides adequate stability for unstable fractures with disco-ligamentous injuries. The primary goal of this study was to assess the radiological and mid-term patient-reported outcome of traumatic subaxial cervical fractures treated with different plate systems. Patients and Methods: Patients, treated with anterior cervical discectomy and fusion (ACDF) between 2001 and 2015, using either a dynamic plate (DP: Mambo™, Ulrich, Germany) or a rigid locking plate (RP: CSLP™, Depuy Synthes, USA), were identified. For radiological evaluation, the sagittal alignment, the sagittal anterior translation and the bony consolidation were evaluated. After at least two years, the patient-reported outcome measures (PROM) were evaluated using the German Short-Form 36 (SF-36), Neck Disability Index (NDI) and the EuroQol in 5 Dimensions (EQ-5D) scores. Results: 33 patients met the inclusion criteria (DP: 13; RP:20). Twenty-six patients suffered from AO Type B or C fractures. Both the sagittal alignment and the sagittal translation could be sufficiently improved in both groups (p ≥ 0.05). No significant loss of reduction could be observed at the follow-up in both groups (p ≥ 0.05). Bony consolidation could be observed in 30 patients (DP: 12/13 (92%); RP: 18/20 (90%); (p ≥ 0.05)). In 20 patients, PROMs could be evaluated (follow-up: 71.2 ± 25.5 months). The whole cohort showed satisfactory PROM results (EQ-5D: 72.0 ± 4.9; SF-36 PCS: 41.9 ± 16.2, MCS: 45.4 ± 14.9; NDI: 11.0 ± 9.1). without significant differences between the DP and RP group (p ≥ 0.05) Conclusion: The dynamic plate concept provides enough stability without a difference in fusion rates in comparison to rigid locking plates in a population that mostly suffered fragile fractures.

Biomechanical Comparison of 1-Level Corpectomy and 2-Level Discectomy for Cervical Spondylotic Myelopathy: A Finite Element Analysis

BACKGROUND Anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF) are effective treatments for cervical spondylotic myelopathy (CSM), but it is unclear which is better. In this study, we compared the biomechanical properties of 2-level ACDF and 1-level ACCF. MATERIAL AND METHODS An intact C3-C7 cervical spine model was developed and validated, then ACDF and ACCF simulation models were developed. We imposed 1.0 Nm moments and displacement-controlled loading on the C3 superior endplate. The range of motions (ROMs) of surgical and adjacent segments and von Mises stresses on endplates, fixation systems, bone-screw interfaces, and bone grafts were recorded. RESULTS ACDF and ACCF significantly reduced the surgical segmental ROMs to the same extent. ACCF induced much lower stress peaks in the fixation system and bone-screw interfaces and higher stress peaks on the bone graft. ACDF induced much lower stress peaks on the C4 inferior endplate and equivalent stress on the C6 superior endplate. There was no difference in the ROMs of surgical and adjacent segments and the intradiscal stress of adjacent levels between ACDF and ACCF. CONCLUSIONS Both ACDF and ACCF can provide satisfactory spinal stability. ACDF may be beneficial for subsidence resistance due to the lower stress peaks on the endplate. The ACCF may perform better in long-term stability and bone fusion owing to the lower stress peaks in the fixation system and bone-screw interfaces, and higher stress peaks in the bone graft.

Eleven-Year Follow-Up of Two Cohorts of Patients Comparing Stand-Alone Porous Tantalum Cage Versus Autologous Bone Graft and Plating in Anterior Cervical Fusions

BACKGROUND

Anterior cervical discectomy and fusion with a porous tantalum cage is an accepted method to treat degenerated cervical discs, with good results, similar to those with autologous bone graft and plating at short- and mid-term follow-up. However, to date, long-term follow-up studies have been performed.

METHODS

We performed a retrospective, single-center study to evaluate the outcomes of 2 cohorts from a previous prospective randomized controlled trial comparing stand-alone tantalum cage (group 1, 27 patients) with autologous bone graft and plating (group 2, 30 patients) for single-level anterior cervical discectomy and fusion at 11 years of follow-up. The usual clinical and radiological outcomes and "overall success," proposed by the Food and Drug Administration, were evaluated.

RESULTS

The improvement in clinical outcomes achieved postoperatively was maintained similarly in the 2 cohorts at 11 years of follow-up. In group 1, the cage had subsided 2-3 mm in 12 patients (44%), segmental lordosis was maintained in 16 patients (59%), adjacent segment degeneration had developed or progressed in 27 of the adjacent segments (50%) in 15 patients (56%), and postoperative nonprogressive deformation of the anterior aspect of the cage was observed in 7 (26%) and minor fragmentation in 3 (11%) patients. In group 2, segmental lordosis was maintained in 90% of the patients and adjacent segment degeneration had developed or progressed in 15 patients (50%).

CONCLUSIONS

These results show that the clinical and radiological outcomes achieved at mid-term follow-up using a tantalum cage for single-level anterior cervical discectomy and fusion will be maintained for 11 years postoperatively, similar to the results with autologous bone graft and plating.

Growth and alignment of the pediatric subaxial cervical spine following rigid instrumentation and fusion: a multicenter study of the Pediatric Craniocervical Society

OBJECTIVE The long-term effects of surgical fusion on the growing subaxial cervical spine are largely unknown. Recent cross-sectional studies have demonstrated that there is continued growth of the cervical spine through the teenage years. The purpose of this multicenter study was to determine the effects of rigid instrumentation and fusion on the growing subaxial cervical spine by investigating vertical growth, cervical alignment, cervical curvature, and adjacent-segment instability over time. METHODS A total of 15 centers participated in this multi-institutional retrospective study. Cases involving children less than 16 years of age who underwent rigid instrumentation and fusion of the subaxial cervical spine (C-2 and T-1 inclusive) with at least 1 year of clinical and radiographic follow-up were investigated. Charts were reviewed for clinical data. Postoperative and most recent radiographs, CT, and MR images were used to measure vertical growth and assess alignment and stability. RESULTS Eighty-one patients were included in the study, with a mean follow-up of 33 months. Ninety-five percent of patients had complete clinical resolution or significant improvement in symptoms. Postoperative cervical kyphosis was seen in only 4 patients (5%), and none developed a swan-neck deformity, unintended adjacent-level fusion, or instability. Of patients with at least 2 years of follow-up, 62% demonstrated growth across the fusion construct. On average, vertical growth was 79% (4-level constructs), 83% (3-level constructs), or 100% (2-level constructs) of expected growth. When comparing the group with continued vertical growth to the one without growth, there were no statistically significant differences in terms of age, sex, underlying etiology, surgical approach, or number of levels fused. CONCLUSIONS Continued vertical growth of the subaxial spine occurs in nearly two-thirds of children after rigid instrumentation and fusion of the subaxial spine. Failure of continued vertical growth is not associated with the patient's age, sex, underlying etiology, number of levels fused, or surgical approach. Further studies are needed to understand this dichotomy and determine the long-term biomechanical effects of surgery on the growing pediatric cervical spine.

Clinical outcome following anterior cervical discectomy and fusion with and without anterior cervical plating for the treatment of cervical disc herniation-a 25-year follow-up study

Extreme long-term clinical outcome studies following anterior cervical discectomy and fusion (ACDF) with an autologous iliac crest with and without Caspar plating (ACDF + CP) for the treatment of radiculopathy caused by cervical disc herniation (CDH) are extremely rare. Hospital records of patients who underwent ACDF or ACDF + CP for the treatment of CDH at least 17 years ago were reviewed. Information about diagnosis, surgery, pre- and postoperative clinical process, and repeated procedure was analyzed. At final follow-up, patients were reviewed with a standardized questionnaire including the current neurological status, Neck Disability Index (NDI), Odom's criteria, a modified EQ-5D, and limitations in quality of life. One hundred twenty-two patients with a mean follow-up of 25 years were evaluated. ACDF was performed in 80 and ACDF + CP in 42 patients, respectively. At final follow-up, 81.1% of patients were free of radicular pain and had no repeated procedure. According to Odom's criteria, 86.1% of good to excellent functional recovery was noted. The mean NDI and EQ-5D was 14% and 5 points, respectively. There was no significant difference in the assessed clinical outcome parameters between patients treated with ACDF and ACDF + CP. The rate for repeated procedure due to degenerative cervical disorders was 10.7 and 7.4% due to symptomatic adjacent segment disease with 25 years. ACDF and ACDF + CP achieved a high rate radicular pain relief (89.3%) and clinical success (86.1%) for the treatment of CDH within a 25 years follow-up. No statistical difference concerning clinical outcome and rate of repeated procedure was detected.

The Effect of Dynamic Versus Static Plating Systems on Fusion Rates and Complications in 1-Level and/or 2-Level Anterior Cervical Discectomy and Fusion: A Systematic Review

STUDY DESIGN

A systematic review.

OBJECTIVE

To determine the effect of plate design on fusion rates in patients undergoing a 1- and 2-level anterior cervical discectomy and fusion (ACDF).

METHODS

Articles published between January 1, 2002 and January 1, 2015 were systematically reviewed to determine the fusion rate of 1- and 2-level ACDFs using either a fully constrained or semiconstrained locking plate. Additional variables that were collected included the number of levels, the type of graft/cage used, the study design, the method for determining fusion, and complications.

RESULTS

Fifty-two articles and 3053 patients were included. No significant difference in the fusion rate for 1- and 2-level ACDF using a fully constrained plate (96.1%) and a semiconstrained plate (95.29%) was identified (P=0.84). No difference (P=0.85) in the total complication rate between fully constrained plates (3.20%) and semiconstrained plates (3.66%), or the rate of complications that required a revision (2.17% vs. 2.41%, P=0.82) was identified. However, semiconstrained plates had a nonsignificant increase in total dysphagia rates (odds ratio=1.660, P=0.28) and short-term dysphagia rates (odds ratio=2.349, P=0.10).

CONCLUSIONS

In patients undergoing a 1- or 2-level ACDF, there is no significant difference in the fusion or complication rate between fully constrained plates and semiconstrained plates.

LEVEL OF EVIDENCE

Level II-systematic review.

Management of subaxial cervical instability in very young or small-for-age children using a static single-screw anterior cervical plate: indications, results, and long-term follow-up

OBJECTIVE Subaxial cervical instability in very young or small-for-age children is uncommon and typically arises from trauma or skeletal dysplasia. Various operative techniques have been used to achieve stabilization in pediatric patients with evidence of instability, including anterior, posterior, and combined approaches. In this study, the authors report their results with subaxial cervical instability in this patient population treated using a static single-screw anterior cervical plate (ACP) system and allograft fusion. METHODS In a retrospective chart review, the authors identified all patients 6 years of age or younger who underwent an anterior cervical fusion procedure using a static single-screw ACP system either as a stand-alone construct or as part of an anterior-posterior stabilization procedure. Reasons for fusion included trauma, tumor, and congenital anomalies. RESULTS Five patients 6 years of age or younger underwent anterior cervical fusion using a static single-screw system during the 19-year study period. Follow-up ranged from 12 to 51 months (mean 26.8 months). Two patients underwent repeat surgery, one 7 days after and the other 21 months after their initial procedure. At last follow-up, a mean vertical growth of 22.8% was seen across the fused segments, with no evidence of kyphotic or lordotic abnormalities. CONCLUSIONS In very young or small-for-age children, the use of a static single-screw ACP system appears to be a safe and effective option to manage subaxial cervical instability. Bony fusion and continued longitudinal growth occur within the fused segments, with no evidence of long-term cervical malalignment.

Early Radiographic and Clinical Outcomes Study Evaluating an Integrated Screw and Interbody Spacer for One- and Two-Level ACDF

BACKGROUND

Multiple techniques and implants can be used in ACDF, the newest of which are integrated cage and screw constructs. These devices may be beneficial over anterior plate constructs due to a negligible anterior profile that may reduce dysphagia. The goal of this study is to review the early radiographical and clinical results associated with a low profile integrated intervertebral cage in one- and two-level anterior column fusions.

METHODS

Fusion rates, incidence of hardware failure and deformity correction were assessed through 1 year. Patientreported scores, including VAS for neck pain, and improvements in axial neck pain and neurologic deficit from the preoperative baseline were quantified at 3, 6 and 12 months post-operatively. The incidence of dysphagia was recorded.

RESULTS

Lordosis and disc space height at the operated levels increased an average of 4.5° and 3.3mm after device placement (p<0.001). Sagittal plane correction was maintained at 1 year. VAS improved from an average of 5.1 preoperatively to 3.1 immediately postoperatively and was maintained at 12 months. At 3 months, patient-reported improvements in axial neck pain and neurologic deficit were 85% and 93%, respectively. Reported improvements were sustained for both parameters at 12 months (77% and 86%, respectively). Fusion was noted in 93% of the operated levels. There were two documented cases of dysphagia that lasted more than 5 weeks, both following two level ACDFs with the test device (3.5% rate of chronic dysphagia).

CONCLUSIONS

The low profile integrated device improved lordosis at the operated level that was maintained at 1 year. Fusion rates with the new device are consistent with ACDF using anterior plating. In combination with improvements in pain and a minimal rate of dysphagia, study findings support the use of integrated interbody spacers for use in one- and two-level ACDF procedures.

LEVEL OF EVIDENCE

Level IV, Case Series.

Methods of evaluating lumbar and cervical fusion

Introduced in 1911, spinal fusion is now widely used to stabilize the cervical, thoracic, and lumbar spine. Despite advancements in surgical techniques, including the use of instrumentation and optimizing bone graft options, pseudarthrosis remains one of the most significant causes of clinical failure following attempted fusion. Diagnosis of this common complication is based on a focused clinical assessment and imaging studies. Pseudarthrosis classically presents with the onset of or return of axial or radicular symptoms during the first postoperative year. However, this diagnosis is complicated because other diagnoses can mimic these symptoms (such as infection or adjacent segment degeneration) and because many cases of pseudarthrosis are asymptomatic. Computed tomography and assessment of motion on flexion/extension radiographs are the two preferred imaging modalities for establishing the diagnosis of pseudarthrosis. The purpose of this article was to review the current status of imaging and clinical practices for assessing fusion following spinal arthrodesis.

Cervical foraminal and discal height after dynamic rotational plating in the cervical discectomy and fusion

STUDY DESIGN

This is a retrospective study.

PURPOSE

To evaluate the effect of the dynamic rotational plate to the intervertebral foraminal and discal height after anterior cervical discectomy and fusion.

OVERVIEW OF LITERATURE

There is no report regarding the changes of foraminal and discal height following cervical dynamic rotational plating.

METHODS

We reviewed the outcomes of 30 patients (36 levels), who were followed-up for an average of 15 months (range, 12-57 months) after undergoing fusions with anterior cervical dynamic rotational plating for cervical radiculopathy, from March 2005 to February 2009. The changes of foraminal and intervertebral discal height of the operated levels were observed on oblique and lateral radiographs obtained at the preoperative, postoperative and follow-up examinations.

RESULTS

The foraminal and discal height increased sufficiently, immediately following the operation. However, follow-up results showed gradual decrease in the foraminal and discal height. After 6 months of the surgery, they showed little difference compared with the preoperative heights. However, clinically, patients showed improvements in radiating pain during the follow-up period.

CONCLUSIONS

Anterior cervical dynamic rotational plating was an effective treatment modality for cervical radiculopathy without the deterioration of the foraminal and intervertebral discal height.

Systematic review of the effect of dynamic fixation systems compared with rigid fixation in the anterior cervical spine

PURPOSE

Anterior cervical fixation is a procedure widely employed in medical practice, with different fixation systems in use. This study aimed to perform a systematic review of the literature comparing the use of rigid and dynamic cervical plates regarding the fusion rate and complications.

METHODS

A search was conducted in PubMed, Lilacs, and Cochrane databases and selecting comparative studies on the use of rigid and dynamic cervical plates. Prospective randomized studies were selected to describe the final results regarding the clinical and radiological outcomes; comparative observational studies were also cited. Complications of using the dynamic cervical plate were also evaluated.

RESULTS

Seven comparative studies were included in the review. Five of these were prospective and randomized studies that did not report significant differences in the clinical outcome. One study reported a faster fusion rate when dynamic cervical plate was used, and another study showed a higher fusion rate when a dynamic cervical plate was applied on multiple levels. Four studies investigated the complications of using a dynamic plate and reported that changes in the cervical curvature angle and material failure were the most frequent complications.

CONCLUSIONS

There were no clinical differences between the two types of cervical fixation systems. A difference in the fusion rates could not be found at any follow-up time or in any of the studies. There was a loss of lordotic correction in the dynamic systems and a higher rate of complications in patients with a loss of lordotic correction.

Loss of lordosis and clinical outcomes after anterior cervical fusion with dynamic rotational plates

PURPOSE

The cervical dynamic rotational plating system may induce bone graft subsidence, so it may cause loss of cervical lordosis. However there were few studies for alignments of cervical spines influencing the clinical results after using dynamic rotational plates. The purpose is to evaluate the effect of graft subsidence on cervical alignments due to the dynamic rotational cervical plates and correlating it with the clinical outcomes of patients undergoing anterior cervical fusion.

MATERIALS AND METHODS

Thirty-three patients with disease or fracture underwent anterior cervical decompression and fusion using a dynamic rotational plate. The presence and extent of implant complications, graft subsidence, loss of lordosis were identified and Visual Analog Scale score (VAS score), Japanese Orthopaedic Association score (JOA score), clinical outcomes based on Odom's criteria were recorded.

RESULTS

Fusion was achieved without implant complications in all cases. The mean graft subsidence at 6 months after the surgery was 1.46 mm. The lordotic changes in local cervical angles were 5.85° which was obtained postoperatively. VAS score for radicular pain was improved by 5.19 and the JOA score was improved by 3. Clinical outcomes based on Odom's criteria showed sixteen excellent, ten good and two satisfactory results. There was no significant relationship between clinical outcomes and changes in the cervical angles.

CONCLUSION

Dynamic rotational anterior cervical plating provides comparable clinical outcomes to that of the reports of former static cervical platings. The loss of lordosis is related to the amount of graft settling but it is not related to the clinical outcomes.

Safety and effectiveness of bone allografts in anterior cervical discectomy and fusion surgery

STUDY DESIGN

Systematic review.

OBJECTIVE

The primary aim of this review was to evaluate clinical and radiographic outcomes in studies of anterior cervical discectomy and fusion (ACDF) using allograft versus ACDF with autograft, ACDF with cage devices, and cervical disc arthroplasty for the treatment of symptomatic cervical disc disease.

SUMMARY OF BACKGROUND DATA

ACDF remains the standard of care for patients with cervical radiculopathy who are unresponsive to conservative medical care. However, no known study has compared patient outcomes after ACDF with allograft, ACDF with autograft, ACDF with cage, and disc arthroplasty.

METHODS

After applying strict inclusion criteria, 21 comparisons from 20 studies formed the basis for this review. Patient outcomes included neck and arm pain, neck disability index (NDI), physical component summary (PCS), and mental component summary (MCS) scores from the SF-36, radiographic fusion rate, and select adverse events (e.g., wound infection, dysphagia, and adjacent segment degeneration).

RESULTS

The four treatment groups included ACDF with allograft (allograft, n = 1341), ACDF with autograft (autograft, n = 568), ACDF with cage (cage, n = 87), and cervical disc arthroplasty (arthroplasty, n = 603). Neck pain was reduced similarly by 63% to 69% in all groups. Comparable improvements were realized in arm pain after ACDF with allograft (75%) or arthroplasty (73%) that were greater than other treatment groups (62-68%). There was notable improvement in neck disability (61-65%) with allograft and arthroplasty after treatment. PCS scores improved with allograft (42%) and arthroplasty (44%). MCS scores improved modestly (16-21%) with allograft and arthroplasty. Fusion rates were 91% for allograft and autograft and 97% for cage. Adverse events were uncommon in all groups.

CONCLUSION

ACDF with allograft, ACDF with autograft, ACDF with cage, and cervical disc arthroplasty show similar improvements in pain, function, and quality of life with correspondingly low adverse event rates. All ACDF procedures result in high fusion rates.

Sagittal alignment after Bryan cervical arthroplasty

STUDY DESIGN

Prospective, randomized, Food and Drug Administration Investigational Device Exemption trial from one study site.

OBJECTIVE

Examine the radiographic sagittal alignment of the Bryan cervical disc for one-level disease.

SUMMARY OF BACKGROUND DATA

Prospective, randomized studies demonstrate Bryan arthroplasty provides statistically better functional outcomes than anterior cervical discectomy and fusion. Uncontrolled case reports describe kyphosis after disc replacement. No prospective study has critically assessed sagittal alignment after cervical arthroplasty.

METHODS

Forty-eight patients reviewed with a minimum follow-up of 2 years. Quantitative motion analysis determined the change in overall (C2-C7) and treatment-level sagittal alignment, disc space heights, and range of motion.

RESULTS

Preoperatively, overall sagittal alignment was equivalent in the two groups. At 24-month follow-up, overall lordosis for the cohorts was not statistically different from preoperative values for each group. In addition, overall lordosis was not significantly different at 24 months when comparing Bryan patients with the fusion patients. The average change in disc angle from preoperative to immediate postoperative at the treated level in the Bryan disc group was a nonsignificant increase in lordosis of 0.92°. The anterior disc height was the same at all time points, but the posterior disc height was slightly (0.7 mm) more in the Bryan than in the fusion patients (P = 0.04). The angular range of motion in the Bryan group was statistically equivalent at all time points. At the fused levels, average range of motion decreased from 6.4° to 0.9° at 24 months (P < 0.0001).

CONCLUSION

With the Bryan disc, there was an insignificant increase in lordosis of 0.9° at immediate postoperative time point. Overall cervical sagittal alignment is not different between the experimental and control populations. This prospective study does not demonstrate a clinically significant increase in segmental kyphosis after Bryan disc arthroplasty. Global cervical lordosis is statistically equivalent between arthroplasty and fusion groups at 2 years follow-up.

Prospective analysis of imaging prediction of pseudarthrosis after anterior cervical discectomy and fusion: computed tomography versus flexion-extension motion analysis with intraoperative correlation

STUDY DESIGN

A prospective comparison of quantitative motion analyzed (QMA) flexion/extension radiographs versus computed tomography (CT) as an analytical predictor of cervical pseudarthrosis. Intraoperative confirmation of the fusion was performed.

OBJECTIVE

To prospectively compare motion analyzed flexion/extension radiographs to CT to predict pseudarthroses. Define motion thresholds on flexion/extension radiographs to define pseudarthroses.

SUMMARY OF BACKGROUND DATA

Assessment of postoperative fusion success is an important factor in assessing success after anterior cervical spine fusion. Gross intervertebral motion can be used as a measure; however, the current "gold standard" for determining fusion status is a CT to assess bridging bone. Defining the amount of intervertebral motion at the fusion site has been previously addressed and definitions have varied widely.

METHODS

Data were analyzed at 47 fusion segments. Intervertebral motion at the fusion site was measured from flexion/extension radiographs taken at least 1 year after the cervical spine fusion. Motion was quantified from digitized radiographs by an independent researcher using proprietary quantitative motion analysis (QMA) software. CT scans on all patients were analyzed for fusion status by a neuroradiologist. Those patients determined to have a symptomatic pseudarthrosis were revised and intraoperative motion at the facet joints was documented. Correlation between intraoperative findings, CT and QMA was performed.

RESULTS

Using greater than 4° of measured motion on flexion/extension radiographs resulted in a Spearman correlation P-value of 0.096 (95% confidence interval: -0.06 to 0.66). Using greater than 1° of motion, the Spearman correlation P < 0.0001 (95% CI: 0.54-0.90). The positive predictive value (PPV) using 4° of motion as the criterion was 100%, indicating a high specificity. The negative predictive value (NPV) was 52%, indicating a low sensitivity. Using greater than 1° of motion, the PPV was 100% and the NPV was 73%. Findings from CT showed an identical PPV and NPV to assessments made using greater than 1° of rotation. Specificity and positive predictive value were 100% for all criteria. Using a lack of bridging on CT or more than 1° of intervertebral motion during flexion/extension increased the sensitivity to 85% and the negative predictive value to 85%.

CONCLUSION

A threshold level of 4° of motion is commonly used to identify a pseudarthrosis. Our prospective study suggests that this value has a high PPV, but a low specificity and would miss many of the pseudarthroses that have angular motion less than 4° (sensitivity 23%). By lowering the threshold for angular motion to 1°, the sensitivity improves to 77%. CT scan has been touted as the gold standard, and it has a high positive predictive value of 100%. However, its NPV was slightly lower than using 1° of motion on QMA analyzed flexion-extension films (73% vs. 79%). In conclusion, although CT scan has long been regarded as the gold standard for determining a pseudarthrosis in the cervical spine, the interpretation is subjective and vulnerable to both type I and type II errors. Analysis of motion using Quantitative Motion Analysis is seemingly less subjective than CT and in our prospective study was more predictive of an operatively confirmed pseudarthrosis.

A Comparison of fixed-hole and slotted-hole dynamic plates for anterior cervical discectomy and fusion

STUDY DESIGN

A retrospective review of clinical data at 1 institution was performed.

OBJECTIVES

To compare the clinical and radiologic outcomes between fixed-hole and slotted-hole dynamic cervical plates.

SUMMARY OF BACKGROUND DATA

Anterior cervical plating is commonly used to increase stability and promote spinal fusion. Two techniques, fixed-hole dynamic plating that uses variable angled screws and slotted-hole dynamic plating that permits sliding, are viable options, but there have been no clinical studies comparing their effectiveness.

METHODS

Fifty-six patients at 1 institution having anterior cervical discectomy and fusion for degenerative disease over a 5-year period were entered into this study. Surgeries were performed with 1 of the dynamic plates for 1 to 3 levels. For the slotted-hole dynamic plate group, a slotted-hole plate was used (ABC, Aesculap, Tuttlingen, Germany or C-tek, Biomet, Parssipany, NJ) and for the fixed-hole dynamic plated group, a variable angled screw was used (C-tek, Biomet, Parssipany, NJ). Radiographic measurements included were graft subsidence, lordotic angle change from each end plate of fusion construct, and implant translation from end plates after a minimum of 12 months follow-up. Fusion state and clinical outcome using Odom's criteria were also evaluated.

RESULTS

Demographics were not different among patient populations. The average age of the patients was 51.0 years (range: 27 to 77 y). Mean follow-up period was 20.6 months (range: 12 to 41 mo). Slotted-hole dynamic plates were used for 29 patients (ABC plate, 17; C-tek plate, 12) and fixed-hole dynamic plates for 27 patients. Clinical outcomes and pseudoarthrosis rates were similar for both types of plates. Radiographic measurements showed a statistically significant increased incidence of graft subsidence and implant translation with the slotted-hole dynamic plates. Loss of lordosis was also greater in the slotted-hole dynamic plated group, although the difference was not statistically significant.

CONCLUSIONS

The use of a fixed-hole dynamic plate is more favorable in regards to graft subsidence and implant translation in the follow-up period, although clinical outcome and fusion rates are similar in patients with either the fixed-hole or slotted-hole dynamic plates.

Dynamic constructs for spinal fusion: an evidence-based review

Dynamic stabilization of the spine has applications in cervical and lumbar degenerative disease and in thoracolumbar trauma. There is little evidence to support the use of dynamic cervical plates rather than rigid anterior cervical fixation. Evidence to support the use of dynamic constructs for fusion in the lumbar spine is also limited. Fusion rates, implant loosening, and failure are significant concerns that limit the adoption of current devices. This article provides a synopsis of the literature on human subjects. There is a need for high-quality evidence for interventions for spinal pathology. An evidence-based approach to the management of spinal disorders will require ongoing assessment of clinical outcomes and comparison of effectiveness between alternatives.

Techniques for anterior cervical decompression for radiculopathy

OBJECT

The objective of this systematic review was to use evidence-based medicine to identify the best techniques for anterior cervical nerve root decompression.

METHODS

The National Library of Medicine and Cochrane Database were queried using MeSH headings and keywords relevant to techniques for the surgical management of cervical radiculopathy. The guidelines group assembled an evidentiary table summarizing the quality of evidence (Classes I-III). The group formulated recommendations that contained the degree of strength based on the Scottish Intercollegiate Guidelines network. Validation was done through peer-review by the Joint Guidelines Committee of the American Association of Neurological Surgeons/Congress of Neurological Surgeons.

RESULTS

Both anterior cervical discectomy (ACD) and anterior cervical discectomy with fusion (ACDF) are equivalent treatment strategies for 1-level disease with regard to functional outcome (Class II). Anterior cervical discectomy with fusion may achieve a more rapid reduction of neck and arm pain compared to ACD with a reduced risk of kyphosis, although functional outcomes may be similar. Anterior cervical discectomy with fusion is not a lasting means of increasing foraminal or disc height compared to ACD. Anterior cervical plating (ACDF with instrumentation) improves arm pain (but not other clinical parameters) better than ACDF in the treatment of 2-level disease (Class II). With respect to 1-level disease, plating may reduce the risk of pseudarthrosis and graft problems (Class III) but does not necessarily improve clinical outcome alone (Class II). Cervical arthroplasty is recommended as an alternative to ACDF in selected patients for control of neck and arm pain (Class II).

CONCLUSIONS

Anterior cervical discectomy, ACDF, and arthroplasty are effective techniques for addressing surgical cervical radiculopathy.

Implant complications, fusion, loss of lordosis, and outcome after anterior cervical plating with dynamic or rigid plates: two-year results of a multi-centric, randomized, controlled study

STUDY DESIGN

Prospective, controlled, randomized, multicenter study.

OBJECTIVE

To analyze implant complications and speed.

SUMMARY OF BACKGROUND DATA

Rigid plate designs, in which the screws are locked to the plate, are in common use and thought to provide more fixation than dynamic designs, in which the screws may glide when the graft is settling. The aim of the study is to analyze (1) implant complications, (2) speed of fusion, (3) loss of lordosis, and (4) clinical outcome in both types of plates.

METHODS

One hundred thirty-two patients were included and assigned by randomization to one of the groups in which they received a routine anterior cervical discectomy and autograft fusion with either a dynamic plate (ABC, study group) or a rigid plate (CSLP, control group). At discharge, after 3 and 6 months and finally after 2 years, implant complications, segmental mobility, absence of radiolucencies, absence of bone sclerosis, evidence of bridging trabecular bone, loss of lordosis, Visual Analog Scale (VAS) and Neck Disability Score were recorded. All radiographic measurements were performed by an independent radiologist.

RESULTS

There have been 4 patients with implant complications within the control group and no implant complications within the study group, P = 0.045. Mean segmental mobility before discharge for the study group was 1.7 mm, 1.4 mm after 3 months, 0.8 mm after 6 months, and 0.4 mm after 2 years. For the control group, these values were 1.0, 1.8, 1.6, and 0.5 mm. The difference at 6 months between both groups was significant (P = 0.024). Neither absence of radiolucencies, nor absence of sclerosis, nor evidence of bridging bone showed significant differences between the 2 groups through the postoperative follow-up (P > 0.05). The loss of segmental lordosis for the study group with respect to intraoperative radiograph was 1.3 degrees at discharge and 4.3 degrees after 2 years. For the control group, these values were 0.9 degrees , 0.7 degrees . The difference at 2 years was significant (P = 0.003). Clinical postoperative outcome (VAS and ODI) was not different between the 2 groups through the postoperative follow-up (P > 0.05).

CONCLUSION

Dynamic cervical plate designs provide less implant complications (no patient) compared with rigid plate designs (4 patients). Speed of fusion was faster in the presence of a dynamic plate. However, loss of segmental lordosis is significantly higher if dynamic plates are used, which did not result in differences regarding clinical outcome between dynamic and constrained plates after 2 years. Thus, dynamic plates should be considered to be the preferred treatment option because of the lower risk for implant failure-related revision surgery.