Posterior Cervical Lateral Mass Screw Fixation and Fusion to Treat Pseudarthrosis of Anterior Cervical Fusion

Outcomes of Revision Surgery for Pseudarthrosis After Anterior Cervical Fusion: Case Series and Systematic Review

STUDY DESIGN

Case series/systematic review.

OBJECTIVES

To report on patients undergoing posterior cervical fusion for symptomatic pseudarthrosis following anterior cervical discectomy and fusion (ACDF), and to assess outcomes reporting in the literature.

METHODS

Patients undergoing posterior instrumented fusion for pseudarthrosis after primary ACDF from 2013 to 2018 by a single surgeon were reviewed consecutively. Neck Disability Index (NDI) and visual analogue scale (VAS) arm/neck were recorded at preoperative, 6-month, and 1-year time points. A systematic review of the literature was performed, and outcomes reporting was recorded.

RESULTS

NDI scores were 54.4 (SD 19.1), 36.6 (SD 18.1), and 41.2 (SD 19.2) at preoperative, 6-month, and 1-year time points, respectively, with improvement from preoperatively to 6 months (P = .004). VAS neck scores were 8.1 (SD 1.3), 5.0 (SD 2.9), and 5.8 (SD 2.2) at preoperative, 6-month, and 1-year time points, respectively, with improvement from preoperatively to 6 months (P = .038). VAS arm scores were 5.1 (SD 4.1), 3.5 (SD 3.2), and 3.6 (SD 2.7) at preoperative, 6-month, and 1-year time points, respectively, with improvement although these did not reach statistical significance (P = .145). The most common subjective outcomes reported in the literature were general symptoms assessments (43%), ordinal scales (43%), and VAS neck (19%) scales, with the majority of studies (67%) documenting one measure.

CONCLUSIONS

Patient-reported outcomes demonstrate clinically meaningful improvement within the first 6 months after posterior fusion for pseudarthrosis. Studies demonstrate substantial variability and no standardization in outcomes reporting, limiting the ability to compare results across interventions and pathologies. Standardized reporting will enable comparisons to inform patients and physicians on the optimal approach to treat this difficult problem.

Cervical Interfacet Spacers to Promote Indirect Decompression and Enhance Fusion in Degenerative Spine: A Review

BACKGROUND

Among the posterior techniques, the use of cervical interfacet spacers (CISs) represents a promising technology whose potentialities are still being studied. The purpose of the present review was to assess the available data on CISs.

METHODS

A search on PubMed was performed. The search terms were "cervical interfacet spacers," "facet spacers," "DTRAX facet system," "Goel facet spacer," "pseudarthrosis," "cervical lordosis," "iatrogenic kyphosis," "cervical foraminal decompression," "cervical biomechanics," "atlantoaxial instability," and "subaxial instability."

RESULTS

Mechanical studies have shown that stand-alone CISs promoted stiffness in all directions, except for extension. Foraminal distraction was recorded in 86% of the cases. Clinical studies have shown that the use of CISs could promote successful arthrodesis, given the large surface area affected by fusion and decreasing the need for autografts. The effectiveness for the treatment of radiculopathy has been confirmed by several clinical studies. In a series of 154 levels of implanted CISs, no evidence of significant loss of cervical lordosis was identified. CISs could help in enhancing fusion in C1-C2 fixation.

CONCLUSIONS

Biomechanical studies on specimens showed a positive trend in increasing stiffness of the cervical spine, despite some controversial results. In clinical studies, facet distraction was shown to be a safe and valid option for clinical indirect decompression, although longer follow-up is required for confirmation. No evidence of the loss of cervical lordosis has been recorded. The long-term effects and CIS use in revision procedures as adjuvant implants to treat pseudarthrosis or atlantoaxial instability are currently under investigation, and further studies are needed.

Preoperative Radiographic Parameters to Predict a Higher Pseudarthrosis Rate After Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective study.

OBJECTIVE

To determine whether postoperative pseudarthrosis can be predicted from specific preoperative radiograph measurements.

SUMMARY OF BACKGROUND DATA

Various factors reportedly influence the occurrence of pseudarthrosis after anterior cervical discectomy and fusion (ACDF). However, to our knowledge, there are no reports on the relationships between preoperative radiographic parameters and pseudarthrosis.

METHODS

We analyzed 84 consecutive patients (45 males, 39 females, mean age, 58.9 ± 11.2 yrs) who underwent ACDF. In all patients, allografts filled with local chip bone were inserted after discectomy and anterior plating was performed. On preoperative plain radiographs, we analyzed C2-C7 sagittal vertical axis, T1 sagittal slope, segmental motion, global cervical motion, and location of fusion segments. Pseudarthrosis was diagnosed as interspinous motion >1 mm with superjacent interspinous motion ≥4 mm on magnified dynamic lateral radiographs. Multivariate logistic regression was used to analyze the risk factors for pseudarthrosis and the receiver operating characteristic (ROC) curve was used to define a cutoff value.

RESULTS

One hundred and twenty-five segments from 84 patients were included. The pseudarthrosis rate was 29% based on number of patients (24/84) and 20% based on number of segments (25/125). Multilevel surgery and segments at the lowest levels showed higher pseudarthrosis rates (P = 0.01). Per multivariate logistic regression analysis, greater preoperative segmental motion, greater preoperative T1 sagittal slope, and C6-7 segments were associated with a higher risk of pseudarthrosis (all P < 0.05). A segmental motion cutoff value of 12° demonstrated pseudarthrosis with sensitivity of 87%, specificity of 84%, and area under the curve of 0.899, indicating moderate accuracy.

CONCLUSION

Greater preoperative segmental motion, greater preoperative T1 sagittal slope, and lower fusion levels could be risk factors for pseudarthrosis following ACDF. Preoperative segmental motion >12° is likely to be an important indicator of the development of pseudarthrosis.

LEVEL OF EVIDENCE

3.

Diagnostic Accuracy of Somatosensory Evoked Potentials in Evaluating New Neurological Deficits After Posterior Cervical Fusions

STUDY DESIGN

This study examined the diagnostic accuracy of significant changes of somatosensory evoked potentials (SSEPs) to evaluate and predict postoperative neurological deficits after posterior cervical fusions (PCF). Eight hundred forty six eligible patients underwent PCF at the University of Pittsburgh Medical Center (UPMC), from 2010 to 2012.

OBJECTIVE

To assess the specificity and sensitivity of intraoperative monitoring in predicting postoperative neurological deficits during PCF.

SUMMARY OF BACKGROUND DATA

We calculated the predictive value, including sensitivity and specificity, of changes in SSEPs to identify neurological deficits postoperatively. We used a receiver operating characteristic (ROC) curve with SSEP categories as cutoff values to further evaluate the diagnostic accuracy of change in SSEPs and postoperative neurological deficit.

METHODS

All patients had preposition baselines and continuous SSEP monitoring throughout the surgery. Statistical analysis was completed using SPSS version 22 (IBM Corp., Armonk, NY).

RESULTS

Age and sex did not influence outcomes. Obesity affected patient outcome. The SSEP categories of significant changes and loss of responses resulted in a sensitivity/specificity of 0.30/0.96 and 0.16/0.98, respectively. The receiver operating characteristic curve has an area under the curve for significant change in/loss of SSEPs of 0.62/0.65 with a 95% confidence interval of 0.525 to 0.714/0.509 to 0.797.

CONCLUSION

Significant SSEP changes during PCF are a very specific but poorly sensitive indicator of postoperative neurological deficits. The odds ratio for significant changes in SSEPs and loss of waveforms was 9.80 and 11.82, respectively, with a 95% confidence interval of 4.695 to 20.46 and 4.45 to 31.41, respectively.

LEVEL OF EVIDENCE

1.

Posterior Cervical Fusion Using Cervical Interfacet Spacers in Patients With Symptomatic Cervical Pseudarthrosis

BACKGROUND

Posterior cervical fusion with cervical interfacet spacer (CIS) is a novel allograft technology offering the potential to provide indirect neuroforaminal decompression while simultaneously enhancing fusion by placing the allograft in compression.

OBJECTIVE

To analyze the clinical and radiological outcomes after posterior cervical fusion with CIS in patients with symptomatic anterior cervical pseudarthroses.

METHODS

Medical records of patients who underwent posterior cervical fusion with CIS for symptomatic pseudarthrosis after anterior cervical diskectomy and fusion were reviewed. Standardized outcome measures such as visual analog scale (VAS) score for neck and arm pain, Neck Disability Index (NDI), and upright lateral cervical radiographs were reviewed.

RESULTS

There were 19 patients with symptomatic cervical pseudarthrosis. Preoperative symptoms included refractory neck or arm pain. The average follow-up was 20 months (range, 12-56 months). There was improvement in VAS score for neck pain (P < .004), radicular arm pain (P < .007), and NDI score (P < .06) after surgery, with 83%, 72%, and 67% of patients showing improvement in their VAS neck pain, VAS arm pain, and NDI scores, respectively. Fusion rate was high, with fusion occurring at all levels treated for pseudarthrosis. There was a small improvement in cervical lordosis (mean difference, 2 ± 5.17°; P = .09) and slight worsening of C2-7 sagittal vertical axis after surgery (mean difference, 1.89 ± 7.87 mm; P = .43).

CONCLUSION

CIS provides an important fusion technique, allowing placement of an allograft in compression for posterior cervical fusion in patients with anterior cervical pseudarthroses. Although there was improvement in clinical outcome measures after surgery, placement of CIS had no clinically significant impact on cervical lordosis and C2-7 sagittal vertical axis.

The Position of the Aorta Relative to the Vertebrae in Patients With Lenke Type 1 Adolescent Idiopathic Scoliosis

STUDY DESIGN

A computed tomography study.

OBJECTIVE

The aim of the study was to clarify the position of the aorta relative to the spine in patients with Lenke type 1 adolescent idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Several authors have examined the position of the aorta in patients with scoliosis; however, their analysis included several types of curve. There is a possibility that the position of the aorta differs according to the scoliosis curve type.

METHODS

Thirty-eight patients with Lenke type 1 were analyzed. The angle (left pedicle aorta [LtP-Ao] angle) and distance (LtP-Ao distance) from the insertion point of the left pedicle screw to the aorta were measured from T4 through L2. The measured data were evaluated from 4 levels above to 4 levels below the apical vertebra. The difference between lumbar modifiers A and C was examined. Dangerous pedicles, which were defined as those in which the aorta entered the expected area based on the screw direction error and length, were counted from T10 to L2.

RESULTS

The aorta was located posterolaterally and adjacent to the vertebra at the middle thoracic level, and anteromedially and distant at the thoracolumbar level. LtP-Ao angle was largest at 1 level above the apical vertebra, and LtP-Ao distance was shortest at 2 levels above. LtP-Ao angle of Lenke 1A was significantly larger than 1C from T11 to L2, and LtP-Ao distance of 1A was significantly shorter than 1C from T11 to L1. When the screw length was 40 mm and the direction error was within 10°, there were a large number of dangerous pedicles at T11, regardless of the lumbar modifier.

CONCLUSION

The direction error has a potential risk of injuring the aorta around the apical vertebra. The selection of screws of the proper length is necessary to avoid a breach of the anterior vertebral wall at thoracolumbar level, especially at T11.

LEVEL OF EVIDENCE

3.

A Meta-Analysis of the Clinical and Fusion Results following Treatment of Symptomatic Cervical Pseudarthrosis

Study Design Systematic literature review and meta-analysis. Objective This study is a meta-analysis assessing the fusion rate and the clinical outcomes of cervical pseudarthrosis treated with either a posterior or a revision anterior approach. Methods A literature search of PubMed, Cochrane, and Embase was performed. Variables of interest included fusion rate and clinical success. The effect size based on logit event rate was calculated from the pooled results. The studies were weighted by the inverse of the variance, which included both within- and between-study error. The confidence intervals were reported at 95%. Heterogeneity was assessed using the Q statistic and I (2), where I (2) is the estimate of the percentage of error due to between-study variation. Results Sixteen studies reported fusion outcomes; 10 studies reported anterior and/or posterior results. The pooled fusion success was 86.4% in the anterior group and 97.1% in the posterior group (p = 0.028). The anterior group demonstrated significant heterogeneity with Q value of 34.2 and I (2) value of 73.7%; no heterogeneity was seen in the posterior group. The clinical outcomes were reported in 10 studies, with eight reporting results of anterior and posterior approaches. The pooled clinical success rate was 77.0% for anterior and 71.7% for posterior (p = 0.55) approaches. There was significant heterogeneity in both groups (I (2) 16.1; 19.2). Conclusions Symptomatic cervical pseudarthrosis can be effectively managed with either an anterior or a posterior approach. The posterior approach demonstrates a significantly greater fusion rate compared with the anterior approach, though the clinical outcome does not differ between the two groups.

Revision surgery for failed cervical spine reconstruction: review article

BACKGROUND

As the number of cervical spine procedures performed continues to increase, the need for revision surgery is also likely to increase. Surgeons need to understand the etiology of post-surgical changes, as well as have a treatment algorithm when evaluating these complex patients.

QUESTIONS/PURPOSES

This study aims to review the rates and etiology of revision cervical spine surgery as well as describe our treatment algorithm.

METHODS

We used a narrative and literature review. We performed a MEDLINE (PubMed) search for "cervical" and "spine" and "revision" which returned 353 articles from 1993 through January 22, 2014. Abstracts were analyzed for relevance and 32 articles were reviewed.

RESULTS

The rates of revision surgery on the cervical spine vary by the type and extent of procedure performed. Patient evaluation should include a detailed history and review of the indication for the index procedure, as well as lab work to rule out infection. Imaging studies including flexion/extension radiographs and computed tomography are obtained to evaluate potential pseudarthrosis. Magnetic resonance imaging is helpful to evaluate the disc, neural elements, soft tissue, and to differentiate scar from infection. Sagittal alignment should be corrected if necessary.

CONCLUSIONS

Recurrent or new symptoms after cervical spine reconstruction can be effectively treated with revision surgery after identifying the etiology, and completing the appropriate workup.

Lateral mass screw fixation in the cervical spine: a systematic literature review

BACKGROUND

Lateral mass screw fixation with plates or rods has become the standard method of posterior cervical spine fixation and stabilization for a variety of surgical indications. Despite ubiquitous usage, the safety and efficacy of this technique have not yet been established sufficiently to permit "on-label" U.S. Food and Drug Administration approval for lateral mass screw fixation systems. The purpose of this study was to describe the safety profile and effectiveness of such systems when used in stabilizing the posterior cervical spine.

METHODS

A systematic search was conducted in MEDLINE and the Cochrane Collaboration Library for articles published from January 1, 1980, to December 1, 2011. We included all articles evaluating safety and/or clinical outcomes in adult patients undergoing posterior cervical subaxial fusion utilizing lateral mass instrumentation with plates or rods for degenerative disease (spondylosis), trauma, deformity, inflammatory disease, and revision surgery that satisfied our a priori inclusion and exclusion criteria.

RESULTS

Twenty articles (two retrospective comparative studies and eighteen case series) satisfied the inclusion and exclusion criteria and were included. Both of the comparative studies involved comparison of lateral mass screw fixation with wiring and indicated that the risk of complications was comparable between treatments (range, 0% to 7.1% compared with 0% to 6.3%, respectively). In one study, the fusion rate reported in the screw fixation group (100%) was similar to that in the wiring group (97%). Complication risks following lateral mass screw fixation were low across the eighteen case series. Nerve root injury attributed to screw placement occurred in 1.0% (95% confidence interval, 0.3% to 1.6%) of patients. No cases of vertebral artery injury were reported. Instrumentation complications such as screw or rod pullout, screw or plate breakage, and screw loosening occurred in <1% of the screws inserted. Fusion was achieved in 97.0% of patients across nine case series.

CONCLUSIONS

The risks of complications were low and the fusion rate was high when lateral mass screw fixation was used in patients undergoing posterior cervical subaxial fusion. Nerve root injury attributed to screw placement occurred in only 1% of 1041 patients. No cases of vertebral artery injury were identified in 758 patients. Screw or rod pullout, screw or plate breakage, and screw loosening occurred in <1% of the screws inserted.

Screw-related complications in the subaxial cervical spine with the use of lateral mass versus cervical pedicle screws

Object

Lateral mass screws (LMS) have been used extensively with a low complication rate in the subaxial spine. Recently, cervical pedicle screws (CPS) have been introduced, and are thought to provide more optimal stabilization of the subaxial spine in certain circumstances. However, because of the concern for neurovascular injury, the routine use of CPS in this location remains controversial. Despite this controversy, however, there are no articles directly comparing screw-related complications of each procedure in the subaxial cervical spine. The purpose of this study was to evaluate screw-related complications of LMS and CPS in the subaxial cervical spine.

Methods

A PubMed/MEDLINE and Cochrane Collaboration Library search was executed, using the key words “lateral mass screw” and “cervical pedicle screw.” Clinical studies evaluating surgical procedures of the subaxial cervical spine in which either LMS or CPS were used and complications were reported were included. Studies in which the number of patients who had subaxial cervical spine surgery and the number of screws placed from C-3 to C-7 could not be specified were excluded. Data on screw-related complications of each study were recorded and compared.

Results

Ten studies of LMS and 12 studies of CPS were included in the analysis. Vertebral artery injuries were slightly but statistically significantly higher with the use of CPS relative to LMS in the subaxial cervical spine. Although the use of LMS was associated with a higher rate of screw loosening, screw pullout, loss of reduction, pseudarthrosis, and revision surgery, this finding was not statistically significant.

Conclusions

Based on the available literature, it appears that perioperative neurological and late biomechanical complication rates, including pseudarthrosis, are similarly low for both LMS and CPS techniques. In contrast, vertebral artery injuries, although statistically significantly more common when using CPS, are extremely rare with both techniques, which may justify their nonroutine use in select cases. Given the paucity of well-designed studies available, this recommendation may be a reflection of deficiencies in the available studies. Surgeons using either technique should have intimate knowledge of cervical anatomy and an adequate preoperative evaluation for each patient, with the final selection based on individual case requirements and anatomical limitations.

Position of the aorta relative to the spine in patients with thoracolumbar/lumbar kyphosis secondary to ankylosing spondylitis

STUDY DESIGN

A computed tomographic study.

OBJECTIVE

To explore the anatomic relationship between the aorta and the spine in patients with thoracolumbar/lumbar kyphosis secondary to ankylosing spondylitis (AS).

SUMMARY OF BACKGROUND DATA

The lumbar spinal osteotomy has been widely adopted for the correction of thoracolumbar/lumbar kyphosis caused by AS. During this procedure, the aorta may be stretched at the osteotomized level and in proximity to the tip of the pedicle screw, both of which imply a potential risk of the aortic injury. To date, no reports have been specifically published for describing the position of the aorta relative to the spine in patients with AS with fixed thoracolumbar/lumbar kyphosis.

METHODS

Thirty-three patients with AS with thoracolumbar/lumbar kyphosis and 38 age- and sex-matched patients with a normal spine were included in this study. For each subject, the left pedicle-aorta angle and distance were measured from T9 to L3 on the computed tomographic scans. Radiographs were analyzed to measure the global kyphosis, lumbar lordosis, and to record the apex of the kyphotic curve.

RESULTS

At T9-L3 levels, patients with AS with thoracolumbar/lumbar kyphosis exhibited significantly smaller left pedicle-aorta angles (from 10.23° to -11.56°) and larger distances (from 39.0 to 55.5 mm) than those with a normal spine. With increased global kyphosis, the aorta shifted more laterally to the right at periapical levels (L1 and L2, P < 0.05). Notably, the aorta was located at the middle front of the vertebrae at T12-L1 levels and far away from the vertebrae at L2 and L3 levels.

CONCLUSION

In patients with AS with thoracolumbar/lumbar kyphosis, the aorta is positioned more anteromedially relative to the vertebral body than that in the normal subjects. The aorta is far away from the vertebral body at L2 and L3 levels, thus it could be much safer to perform osteotomy below L1.

LEVEL OF EVIDENCE

4.

Analysis of cervical sagittal alignment after screw-rod fixation

BACKGROUND

The use of posterior instrumentation constructs is well established for subaxial cervical stabilizations/fusions. The importance of global and regional sagittal alignment has become increasingly recognized.

OBJECTIVE

To perform an analysis using computed tomography scans to determine the effect of posterior instrumentation on postoperative cervical sagittal alignment at long-term follow-up.

METHODS

Over a period of 6 years, 56 consecutive patients (38 male and 18 female patients; mean age, 47 years) underwent cervical screw-rod fixation. Plain radiographs, computed tomography scans, and magnetic resonance images were analyzed preoperatively to assess sagittal alignment (C2-C7). Postoperatively, computed tomography scans and serial radiographs were obtained in all patients. With the use of independent observers, changes in sagittal alignment were determined by comparing the preoperative and postoperative imaging studies.

RESULTS

In total, 390 screws were placed in the cervical spines of 56 patients. Definitive radiographic fusion was detected in all 56 patients (100%). There were no incidences of instrumentation failures or lucencies surrounding any screws. Patients with preoperative kyphosis (n = 19; mean, +9.9°) improved their sagittal alignment by 6.5° (final mean, +3.4°), whereas patients with preoperative lordosis (n = 37; mean -15.44°) maintained their lordosis (final mean, -15.3°). Mean duration of follow-up was 32.5 months.

CONCLUSION

Radiographic analysis showed lateral mass fixation to be safe and effective. Certain operative techniques allowed substantial deformity correction and maintenance of long-term correction of deformity. Screw-rod fixation may be an effective method for maintaining lordotic cervical alignment in previously lordotic patients and for significantly correcting kyphotic deformity in patients with a preoperative kyphosis.

Radiological Efficacy of Cervical Lateral Mass Screw Insertion and Rod Fixation by Modified Magerl's Method (Yoon's Method) with Minimum 2 Years of Follow-up

Objective

Cervical lateral mass screw insertion and rod fixation is a useful method for stabilizing the cervical disease, so various modified techniques were present. Many surgeons had reported the biomechanical safety according to the screw positioning method in the cervical spine, but the modified Magerl's method (Yoon's method) was not well studied. So, this study assessed the radiological efficacy of the modified Magerl's method with long-term follow-up.

Methods

This study retrospectively reviewed 323 lateral mass screws of 50 patients who had followed-up at least 2 years. Radiologic data were analyzed as parameters of complications after operation, including kyphotic or lordotic change, bone fusion, pull-out or malposition of screw, foraminal stenosis, adjacent disc degeneration or aggravation, pseudoarthrosis, and vertebral artery injury.

Results

The mean follow-up period was 32 (24 to 52) months. There were kyphotic changes in 4.0%(2 of 50 cases). Unsuccessful bone fusion occurred in 4.0%(2 of 50 cases). Among the 323 screws, screw pull-out (4.0%. 2 of 50cases, 3 of 323 screws), foraminal invasion (1.2% of total screws), and facet injury (0.6% of total screws) occurred.

Conclusion

The lateral mass screw insertion and rod fixation by the modified Magerl's method (Yoon's method) is a safe and reliable technique with low rate of complication related to instruments in minimum 2 years follow-up.