Sagittal segmental alignment as predictor of adjacent-level degeneration after a cloward procedure

Radiographic Risk Factors for Adjacent Segment Disease Following Anterior Cervical Discectomy and Fusion (ACDF): A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVES

To assess the radiographic risk factors for adjacent segment disease (ASD) following anterior cervical discectomy and fusion (ACDF) for degenerative cervical spine pathologies.

METHODS

PubMed, Embase and the Cochrane Library databases were searched up to December 2023. The primary inclusion criteria were degenerative spinal conditions treated with ACDF, comparing radiological parameters in patients with and without postoperative ASD. The radiographic parameters included intervertebral disc height, cervical sagittal alignment, sagittal segmental alignment, range of motion, segmental height, T1 slope, sagittal vertical axis (SVA), thoracic inlet angle (TIA), and plate to disc distance (PPD). Risk of bias was assessed for all studies. The Cochrane Review Manager was utilized to perform the meta-analysis.

RESULTS

From 7044 articles, 13 retrospective studies were included in the final analysis. Three studies had "not serious" bias and the other 10 studies had serious or very serious bias. The total number of patients in the included studies was 1799 patients. Five studies included single-level ACDF, 2 studies included multi-level ACDF, and 6 studies included single or multi-level ACDF. On meta-analysis, the significant risk factors associated with ASD development were reduced postoperative cervical lordosis (mean difference [MD] = 3.35°, P = .002), reduced last-follow-up cervical lordosis (MD = -3.02°, P = .0003), increased preoperative to postoperative cervical sagittal alignment change (MD = -3.68°, P = .03), and the presence of developmental cervical canal stenosis (Odds ratio [OR] = 4.17, P < .001).

CONCLUSIONS

Decreased postoperative cervical lordosis, greater change in cervical sagittal alignment and developmental cervical canal stenosis were associated with an increased risk of ASD following ACDF.

Anterior cervical discectomy and fusion with a dynamic translational plating versus a rigid carbon fiber reinforced PEEK plating system - a comparison study of radiographic parameters

PURPOSE

In this study the authors compare the radiographic findings of patients undergoing 1-3 level ACDF a rigid CFRP plate and a translational titanium plate system with a focus on radiographic alignment.

MATERIAL AND METHODS

A retrospective review 70 consecutive patients undergoing a 1 to 3 level ACDF for cervical spondylosis was conducted. 2 groups depending on the cervical plating system were created including 38 patients in group 1 (dynamic plate) and 32 in group 2 (rigid CFRP plate). Plain neutral radiographs preoperatively, immediately after surgery and at most recent follow-up were used to assess parameters on sagittal alignment, fusion height, adjacent segment ossification (ASO), fusion rate and implant failure.

RESULTS

There were no significant differences between groups preoperatively. Both groups had a more than 12 months follow-up (p = 0.327). Improvement of C2-7 lordosis was seen in both groups but only in group 1 it reached statistical significance at final follow-up. Significant improvement in sagittal segmental alignment was noted in both groups following surgery. A significant sagittal correction of 5.5 ± 9.1 degrees (p = 0.002) was maintained through follow-up only in group 2. No significantly different was seen for segmental fusion rates and loss of fusion height. There were no instances of implant failure within both groups. Worsening of ASO was 20% for both groups.

CONCLUSION

ACDF allows for correction and maintenance of cervical alignment. Rigid rigid plate appears more effective at maintaining segmental lordotic correction. The fusion rate and implant failure was not different for both groups.

The impact of over-distraction on adjacent segment pathology and cage subsidence in anterior cervical discectomy and fusion

Over-distraction has been shown to be a risk factor for cage subsidence and postoperative neck pain after anterior cervical discectomy and fusion (ACDF). Biomechanical studies have demonstrated increased adjacent segment intradiscal pressure after ACDF. The purpose of this study is to determine if over-distraction of the index disc has an effect on adjacent segment pathology. A consecutive series of 145 patients who received primary ACDF for cervical degenerative pathologies from January 2010 to December 2017 were retrospectively reviewed. The patients were divided into: (1) Over-distraction group (postoperative-preoperative index disc height ≥ 2 mm), and (2) No-distraction group (postoperative-preoperative index disc height < 2 mm). Outcome measures included radiographic parameters, Japanese Orthopaedic Association (JOA) score, and incidences of cage subsidence, radiological and clinical adjacent segment pathologies (RASP and CASP) were compared between the two groups preoperatively, postoperatively, and at the final follow-up. The two groups were comparable with respect to age, follow-up length, JOA score, incidence of CASP, and radiographic parameters. The Over-distraction group (83 patients; 115 levels) had smaller preoperative index disc height (4.5 vs. 5.2 mm, p < 0.001), but taller postoperative index disc height (7.7 vs. 6.6 mm, p < 0.001) than No-distraction group (62 patients; 90 levels) Furthermore, significantly higher incidences of cage subsidence (47% vs. 31%, p = 0.04) and RASP (any progression: 48% vs. 15%, p < 0.001; progress ≥ 2 grades: 25% vs. 7%, p = 0.001) were observed in the Over-distraction group. The multivariate analysis indicated that over-distraction and multilevel fusion were independent risk factors for RASP. There were no clinical outcome differences between the Over-distraction group and the No-distraction group in ACDF. Over-distraction of the index level of ≥ 2 mm should be avoided because it significantly increases the incidences of RASP and cage subsidence.

Incidence of cervical kyphosis and cervical posterior translation in neck pain associated with radiological evidence of degenerative disc disease

BACKGROUND

Cervical kyphosis mechanically influences the intervertebral discs, which may lead to neck, shoulder, and scapular pain.

OBJECTIVES

To investigate the incidence of cervical kyphosis and posterior displacement of cervical vertebrae (cervical posterior translation index) in patients with radiologically evident degenerative disc disease.

DESIGN

Retrospective-cohort study.

METHODS

Ninety-five patients with radiologically evident degenerative disc disease were recruited at our clinic from 2015 to 2019. Radiography images were used to analyze the straight-line index in each patient in the upright posture. The straight-line index was calculated by drawing a reference line connecting the posterior inferior edges of C2 to C7 and normalizing the addition of the distances from the posterior inferior edges of C3, C4, C5, and C6 to the reference line, respectively. Straight-line index <0 was defined as cervical kyphosis and ≥0 as cervical lordosis, the cervical kyphosis. In cervical kyphosis group, the distance from the posterior inferior edges of C3, C4, C5, and C6 to the reference line was normalized by the reference line distance to determine posterior displacement. Multiple comparison tests aside from simple and multiple linear regression analysis were performed.

RESULTS

The incidence of cervical kyphosis in patients with radiologically evident degenerative disc disease was 60% (57/95 patients). Multiple comparison tests revealed that the cervical posterior translation indexes of C4 and C5 were significantly higher than those of C3, C4, and C6, in cervical kyphosis group.

CONCLUSIONS

Cervical kyphosis was present in 60% of patients with radiologically evident degenerative disc disease, with C5 showing the most posterior displacement.

The Efficacy of Cervical Lordosis Rehabilitation for Nerve Root Function and Pain in Cervical Spondylotic Radiculopathy: A Randomized Trial with 2-Year Follow-Up

Sagittal cervical alignment is a clinically related feature in patients suffering from chronic cervical spondylotic radiculopathy (CSR). We designed this randomized trial to explore the effects of cervical lordosis (CL) correction in thirty chronic lower CSR patients with CL < 20°. Patients were assigned randomly into two equal groups, study (SG) and control (CG). Both groups received neck stretching and exercises and infrared radiation; additionally, the SG received cervical extension traction. Treatments were applied 3× per week for 10 weeks after which groups were followed for 3 months and 2 years. The amplitude of dermatomal somatosensory evoked potentials (DSSEPS), CL C2−C7, and pain scales (NRS) were measured. The SG had an increase in CL post-treatment (p < 0.0001), this was maintained at 3 months and 2 years. No statistical improvement in CL was found for the CG. A significant reduction in NRS for SG after 10 weeks of treatment with non-significant loss of change at 3 months and continued improvement at 2 years was found. CG had less significant improvement in post-treatment NRS; the 3-month and 2-year measures revealed significant worsening in NRS. An inverse linear correlation between increased CL and NRS was found (r = −0.49; p = 0.005) for both groups initially and maintained in SG at the final 2-year follow-up (r = −0.6; p = 0.01). At 10 weeks, we found significant improvements in DSSEPS for both groups (p < 0.0001). We identified a linear correlation between initial DSSEPs and CL for both groups (p < 0.0001), maintained only in the SG at the final follow-up for all levels (p < 0.0001). Improved CL in the SG correlated with significant improvements in nerve root function and pain rating in patients with CSR at short and long-term follow-up. These observed effects indicate that clinicians involved in the treatment of patients with symptoms of cervical degenerative disorders should add sagittal curve correction to their armamentarium of rehabilitation procedures for relevant patient populations.

Allograft Subsidence Decreases Postoperative Segmental Lordosis With Minimal Effect on Global Alignment Following ACDF

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Studies investigating the impact of interbody subsidence in ACDF suggest a correlation between subsidence and worse radiographic and patient-reported outcomes. The purpose of this study was to assess whether allograft subsidence assessed on CT is associated with worse cervical alignment.

METHODS

We performed a retrospective review of a prospective cohort of patients undergoing 1 to 3 level ACDF. Cervical alignment was assessed on standing radiographs performed preoperatively, less than 2 months postoperatively, and greater than 6 months postoperatively. Allograft subsidence was assessed on CT scan performed at least 6 months postoperatively. Patients with at least 1 level demonstrating greater than 4mm of cage subsidence were classified as severe subsidence. Student's t-test was used to compare all means between groups.

RESULTS

We identified 66 patients for inclusion, including 56 patients with non-severe subsidence and 10 patients with severe subsidence. For the entire cohort, there was a significant increase in C2-7 Lordosis (p = 0.005) and Segmental Lordosis (p < 0.00 001) from preoperative to early postoperative. On comparison of severely and non-severely subsided levels, severely subsided levels demonstrated a significantly greater loss of segmental lordosis from early to mid-term follow-up than non-severely subsided levels (-4.89 versus -2.59 degrees, p < 0.0001), manifesting as a significantly lower segmental lordosis at >6 months postoperative (0.54 versus 3.82 degrees, p < 0.00 001). There were no significant differences in global cervical alignment parameters between patients with severe and non-severe subsidence.

CONCLUSIONS

Severe subsidence is associated with a significant increase in loss of segmental lordosis, but has minimal effect on global cervical alignment parameters.

A New Potential Complication in 2-Level Anterior Cervical Discectomy and Fusion with Zero-Profile Devices: Collapse of the Middle Cervical Vertebra

OBJECTIVE

The objective of this study was to describe a new potential complication, collapse in the middle cervical vertebra of consecutive 2-level anterior cervical discectomy and fusion (ACDF), and discuss its possible mechanism.

METHODS

Clinical and radiologic outcome data from 27 consecutive 2-level ACDF patients using zero-profile devices were collected at 1, 3, 6, and 12 months postoperatively, as well as the last follow-up. Dysphagia was assessed using the Bazaz score, and clinical outcomes were analyzed using the neck disability index and Japanese Orthopaedic Association score. Radiographic evaluation included measurements of the overall and surgical segment curvature, identification of collapse, and assessment of the ratio of anterior height and wedge of the upper, middle, and lower vertebrae in the surgical segment.

RESULTS

The application of zero-profile devices to treat consecutive 2-level cervical spondylosis mostly resulted in good midterm clinical outcomes. Surprisingly, as evidenced by the significantly decreased anterior height and wedge ratio of the middle cervical vertebra, collapse was noted immediately in the middle vertebra in 4 patients at 1 month (n = 3) and 3 months (n = 1). The collapse increased for no more than 6 months, and there was no deterioration of clinical and radiological outcomes at the last follow-up.

CONCLUSIONS

Collapse in the middle cervical vertebra of consecutive 2-level ACDF with the application of zero-profile devices can occur in the early postoperative period, which may be due to axial stress concentration and blood supply damage in the middle cervical vertebral body.

Surgery-related Factors Do Not Affect Short-term Adjacent Segment Kinematics After Anterior Cervical Arthrodesis

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

The aim of this study was to identify surgical factors that affect adjacent segment kinematics after anterior cervical discectomy and fusion (ACDF) as measured by biplane radiography.

SUMMARY OF BACKGROUND DATA

Previous studies investigated the effect of surgical factors on spine kinematics as a potential etiology for adjacent segment disease (ASD). Those studies used static flexion-extension radiographs to evaluate range of motion. However, measurements from static radiographs are known to be unreliable. Furthermore, those studies were unable to evaluate the effect of ACDF on adjacent segment axial rotation.

METHODS

Patients had continuous cervical spine flexion/exten- sion and axial rotation movements captured at 30 images per second in a dynamic biplane radiography system preoperatively and 1 year after ACDF. Digitally reconstructed radiographs generated from subject-specific CT scans were matched to biplane radiographs using a previously validated tracking process. Dynamic kinematics, postoperative segmental kyphosis, and disc distraction were calculated from this tracking process. Plate-to-disc distance was measured on postoperative radiographs. Graft type was collected from the medical record. Multivariate linear regression was performed to identify surgical factors associated with 1-year post-surgery changes in adjacent segment kinematics. A secondary analysis was also performed to compare adjacent segment kinematics between each of the surgical factors and previously defined thresholds believed to be associated with adjacent segment degeneration.

RESULTS

Fifty-nine patients completed preoperative and postoperative testing. No association was found between any of the surgical factors and change in adjacent segment flexion/exten- sion or axial rotation range of motion (all P > 0.09). The secondary analysis also did not identify differences between adjacent segment kinematics and surgical factors (all P > 0.07).

CONCLUSION

Following ACDF for cervical spondylosis, factors related to surgical technique were not associated with short-term changes in adjacent segment kinematics that reflect the hypermobility hypothesized to lead to the development of ASD.Level of Evidence: 2.

Significance of Cervical Spine Computed Tomography Hounsfield Units to Predict Bone Mineral Density and the Subsidence After Anterior Cervical Discectomy and Fusion

STUDY DESIGN

This study was a retrospective review.

OBJECTIVE

The purpose of this study was to investigate the correlation analysis between Hounsfield units (HU) and dual x-ray absorptiometry (DXA) based on the clinical results of patients who underwent anterior cervical discectomy and fusion (ACDF) surgery.

SUMMARY OF BACKGROUND DATA

There is no technique to directly measure bone mineral density (BMD) in the cervical spine. As computed tomography is a very popular preoperative planning modality, using the HU value from that analysis to predict osteoporosis is important for patient outcomes and applications in the clinical field.

MATERIALS AND METHODS

We reviewed the records for 235 patients who underwent 1-level (n=120) or 2-level (n=115) ACDF surgery. In the 1-level ACDF group, the HU was measured from C3 to C6 vertebra, while that for the 2-level ACDF group was measured from 3 surgical index vertebrae. The correlation patterns were analyzed with the corresponding DXA (T-score) for each patient. Subsidence of fusion segment was defined as change in distance between plate-tip and upper (lower) margin of the vertebra (index level) after 4 months of follow-up. In addition, to determine the relevant factors that influence fusion segment subsidence, other preoperative (C2 slope, C7 slope, C2-C7 angle, and C2-C7 sagittal vertical axis) and postoperative parameters (coronal angle and segmental angle change) were measured.

RESULTS

The correlation coefficient between HU and DXA ranged from 0.57 to 0.71 in the 1-level ACDF group and from 0.59 to 0.66 in the 2-level ACDF group. The correlation between HU and DXA was statistically significant regardless of the degree of anterior osteophyte (r=-0.65 to 0.78). Total subsidence height was 3.8 mm after ACDF, and both HU and DXA were statistically correlated with total subsidence (r=0.26-0.28). In multivariate analysis, HU (middle vertebra) value was statistically associated with the degree of total subsidence. The high-subsidence group (≥4.5 mm) showed smaller HU values (284.1 vs. 316.0) and T-scores (-0.5 vs. 0.1) compared to the low-subsidence group (<4.5 mm). The discrepancy group, defined as cases with excess plate shift on 1 side, also showed smaller HU values (260.4 vs. 312.4) and higher degrees of total subsidence than the matched group.

CONCLUSIONS

The correlation between HU in cervical computed tomography and lumbar DXA (T-score) was statistically significant in both 1-level and 2-level ACDF. The level of BMD (HU or DXA) is a very important factor for clinically determining the amount and regularity of subsidence after ACDF. Therefore, HU can be a good alternative assessment to accurately reflect as much of the BMD degree as DXA in the cervical spine.

Influence of cervical spine sagittal alignment on range of motion after corpectomy: a finite element study

BACKGROUND

Sagittal alignment of the cervical spine might influence the development of radiological adjacent segment pathology (RASP) after central corpectomy (CC). Range of motion (ROM) of the adjacent segments is closely linked to the development of RASP.

METHODS

To investigate the ROM of the adjacent segments after CC, we developed a C2-T1 finite element (FE) model. The model with a lordotic sagittal alignment served as the baseline model. Models with straight and kyphotic alignment were generated using mesh morphing methods. Single-level corpectomy at C5 was done on these models. Segmental ROMs of intact and corpectomized spines were compared for physiologic flexion-extension loads.

RESULTS

The flexion ROM decreased by an average of 13% with the change in sagittal alignment from lordosis to kyphosis; however, a consistent decrease was not observed in extension. After CC, the ROM increased by an average of 95% and 31% in the superior and inferior adjacent segments. With kyphotic change in the sagittal alignment, the postoperative increase in flexion ROM exhibited a decreasing trend, while this was not seen in extension.

CONCLUSIONS

Kyphotic changes of the intact spine resulted in segmental stiffening, and after corpectomy, it resulted in inconsistent variations of segmental extension ROMs.

Cervical Sagittal Alignment: Literature Review and Future Directions

Cervical alignment as a concept has come to the forefront for spine deformity research in the last decade. Studies on cervical sagittal alignment started from normative data, and expanded into correlation with global sagittal balance, prognosis of various conditions, outcomes of surgery, definition and classification of cervical deformity, and prediction of targets for ideal cervical reconstruction. Despite the recent robust research efforts, the definition of normal cervical sagittal alignment and cervical spine deformity continues to elude us. Further, many studies continue to view cervical alignment as a continuation of thoracolumbar deformity and do not take into account biomechanical features unique to the cervical spine that may influence cervical alignment, such as the importance of musculature connecting cranium-cervical-thoracic spine and upper extremities. In this article, we aim to summarize the relevant literature on cervical sagittal alignment, discuss key results, and list potential future direction for research using the '5W1H' framework; "WHO" are related?, "WHY" important?, "WHAT" to evaluate and "WHAT" is normal?, "HOW" to evaluate?, "WHEN" to apply sagittal balance?, and "WHERE" to go in the future?

Vertebral Body Sliding Osteotomy for Cervical Myelopathy With Rigid Kyphosis

Cervical spondylotic myelopathy is surgically demanding when associated with rigid kyphosis. Posterior surgery cannot restore cervical lordosis, and adequate decompression is not possible with rigid kyphosis. Vertebral body sliding osteotomy (VBSO) is a safe and novel technique for anterior decompression in patients with multilevel cervical spondylotic myelopathy. It is safe in terms of dural tear, pseudarthrosis, and graft dislodgement, which are demonstrated at high rates in anterior cervical corpectomy and fusion. In addition, VBSO is a powerful method for restoring cervical lordosis through multilevel anterior cervical discectomy and fusion above and below the osteotomy level. It may be a feasible treatment option for patients with cervical spondylotic myelopathy and kyphotic deformity. This is a technical note and literature review that describes the procedures involved in VBSO.

Improvement in cervical lordosis and sagittal alignment after vertebral body sliding osteotomy in patients with cervical spondylotic myelopathy and kyphosis

OBJECTIVE

Vertebral body sliding osteotomy (VBSO) is a safe, novel technique for anterior decompression in patients with multilevel cervical spondylotic myelopathy. Another advantage of VBSO may be the restoration of cervical lordosis through multilevel anterior cervical discectomy and fusion (ACDF) above and below the osteotomy level. This study aimed to evaluate the improvement and maintenance of cervical lordosis and sagittal alignment after VBSO.

METHODS

A total of 65 patients were included; 34 patients had undergone VBSO, and 31 had undergone anterior cervical corpectomy and fusion (ACCF). Preoperative, postoperative, and final follow-up radiographs were used to evaluate the improvements in cervical lordosis and sagittal alignment after VBSO. C0-2 lordosis, C2-7 lordosis, segmental lordosis, C2-7 sagittal vertical axis (SVA), T1 slope, thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt, and Japanese Orthopaedic Association scores were measured. Subgroup analysis was performed between 15 patients with 1-level VBSO and 19 patients with 2-level VBSO. Patients with 1-level VBSO were compared to patients who had undergone 1-level ACCF.

RESULTS

C0-2 lordosis (41.3° ± 7.1°), C2-7 lordosis (7.1° ± 12.8°), segmental lordosis (3.1° ± 9.2°), and C2-7 SVA (21.5 ± 11.7 mm) showed significant improvements at the final follow-up (39.3° ± 7.2°, 13° ± 9.9°, 15.2° ± 8.5°, and 18.4 ± 7.9 mm, respectively) after VBSO (p = 0.049, p < 0.001, p < 0.001, and p = 0.038, respectively). The postoperative segmental lordosis was significantly larger in 2-level VBSO (18.8° ± 11.6°) than 1-level VBSO (10.3° ± 5.5°, p = 0.014). The final segmental lordosis was larger in the 1-level VBSO (12.5° ± 6.2°) than the 1-level ACCF (7.2° ± 7.6°, p = 0.023). Segmental lordosis increased postoperatively (p < 0.001) and was maintained until the final follow-up (p = 0.062) after VBSO. However, the postoperatively improved segmental lordosis (p < 0.001) decreased at the final follow-up (p = 0.045) after ACCF.

CONCLUSIONS

Not only C2-7 lordosis and segmental lordosis, but also C0-2 lordosis and C2-7 SVA improved at the final follow-up after VBSO. VBSO improves segmental cervical lordosis markedly through multiple ACDFs above and below the VBSO level, and a preserved vertebral body may provide more structural support.

Two-level ACDF with a zero-profile stand-alone spacer compared to conventional plating: a prospective randomized single-center study

PURPOSE

Stand-alone zero-profile devices have already proven safety, and a reduced dysphagia rate was assumed. So far, no level-one evidence is available to prove the proposed advantages of zero-profile implants in multilevel procedures. The aim of this RCT was to compare the clinical and radiological outcome of a zero-profile spacer versus cage + plate in two-level ACDF.

METHODS

Consecutive patients with contiguous two-level cDD were randomly assigned either to the interventional group (zero-profile device) or to the control group (cage + plate). Primary endpoint of the study was the prevalence of dysphagia at 24 months. Disability, progress of adjacent segment degeneration, fusion status and loss of correction were analyzed as secondary outcome measure. Primary outcome parameter was statistically analyzed by Chi-square test.

RESULTS

Forty-one patients met inclusion criteria and were randomly assigned to the interventional and the control group. Dysphagia was frequent in either group at 3 months FU favoring interventional group (p = 0.078). At final FU, less patients of the interventional group complained about dysphagia, but the difference was not significant. No relevant differences at final FU were recorded for NPDI, loss of correction and adjacent-level degeneration. Fusion rate was slightly lower in the interventional group.

DISCUSSION

Two-level ACDF either by a stand-alone zero-profile spacer or cage + plate is safe. Using a zero-profile cage dysphagia was infrequent at 24 months, but the value did not reach statistical significance in comparison with the cage + plate. Hence, this randomized trial was not able to prove the proposed clinical superiority for dysphagia rates for zero-profile anchored spacer in two-level cDD.

A review of cervical spine alignment in the normal and degenerative spine

With recent advancements in surgical spine technology and techniques, the importance of regional and global spine alignment has become an important factor in surgical planning. Our review aims to consolidate the current literature on cervical and global alignment parameters and its relationship to cervical symptomatology, quality of life (QOL), requirements for surgery, potential surgical complications and health-related quality of life (HRQOL) outcomes.

0.5- to 1-Fold Intervertebral Distraction Is a Protective Factor for Adjacent Segment Degeneration in Single-level Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective analysis.

OBJECTIVE

This study aimed to compare the clinical and radiological outcomes of different degrees of distraction in anterior cervical discectomy and fusion (ACDF) and evaluate the risk factors for adjacent segment degeneration (ASD).

SUMMARY OF BACKGROUND DATA

ASD is a common complication following ACDF. Inadequate distraction of the intervertebral space during surgery is associated with ASD; however, there is still an ongoing debate regarding what degree of distraction is appropriate.

METHODS

This retrospective study enrolled 130 patients who underwent single-level ACDF for cervical degenerative disc disease and were followed up at least 2 years. The patients were divided into the following three groups according to the degree of distraction (≤0.5, 0.5-1, ≥1): insufficient distraction group (ID group), appropriate distraction group (AD group), and excessive distraction group (ED group). The clinical outcomes and radiological parameters were evaluated before and after operation and at the last follow-up. Risk factors for ASD were identified through logistic regression analysis.

RESULTS

A significant difference was found in the Visual Analog Scale values between the AD group and ED group at the final follow-up. Moreover, the highest upper segmental disc height (DH), highest lower segmental DH, and lowest incidence of ASD were found in the AD group among the three groups at last follow up. Logistic regression analysis revealed that segmental kyphosis (odds ratio = 2.821, P = 0.020) was a risk factor for the occurrence of ASD and 0.5- to 1-fold distraction (odds ratio = 0.350, P = 0.025) was a protective factor.

CONCLUSION

Good clinical and radiological outcomes were achieved in ACDF with 0.5- to 1-fold distraction. Segmental kyphosis is a risk factor for ASD in ACDF, whereas 0.5- to 1-fold distraction is a protective factor of ASD.

LEVEL OF EVIDENCE

4.

Repeat Radiography in Monitoring Structural Changes in the Treatment of Spinal Disorders in Chiropractic and Manual Medicine Practice: Evidence and Safety

There is substantial evidence for normal relationships between spine and postural parameters, as measured from radiographs of standing patients. Sagittal balance, cervical lordosis, thoracic kyphosis, lumbar lordosis, pelvic tilt, and the more complex understanding of the interrelations between these essential components of normal stance have evolved to where there are known, established thresholds for normalcy. These spinal parameters are reliably measured from X-ray images and serve as goals of care in the treatment of spine and postural disorders. Initial and follow-up spinal imaging by X-ray is thus crucial for the practice of contemporary and evidence-based structural rehabilitation. Recent studies have demonstrated that improvement in the spine and posture by nonsurgical methods offers superior long-term patient outcomes versus conventional methods that only temporarily treat pain/dysfunction. Low-dose radiation from repeated X-ray imaging in treating subluxated patients is substantially below the known threshold for harm and is within background radiation exposures. Since alternative imaging methods are not clinically practical at this time, plain radiography remains the standard for spinal imaging. It is safe when used in a repeated fashion for quantifying pre-post spine and postural subluxation and deformity patterns in the practice of structural correction methods by chiropractic and other manual medicine practices.

Association between sagittal balance and adjacent segment degeneration in anterior cervical surgery: a systematic review and meta-analysis

Background

ASD is a relatively common degenerative alteration after cervical surgery which occurs above or below the fused segment. In addition, some patients may need reoperation to treat severe ASD after the primary surgery. It was considered that sagittal balance is correlated with postoperative clinical outcomes; however, few studies have reported the influence of sagittal balance on ASD. The present study is designed to investigate whether sagittal balance impacts the pathology of adjacent segment disease (ASD) in patients who undergo anterior cervical surgery for degenerative cervical disease.

Methods

Databases including Pubmed, Embase, Cochrane library, and Web of Science were used to search for literature published before June 2018. Review Manager 5.3 was used to perform the statistical analysis. Sagittal balance parameters before and after surgery were compared between patients with and without ASD. Weighted mean difference (WMD) was summarized for continuous data and P < 0.05 was set for the level of significance.

Results

A total of 221 patients with ASD and 680 patients without ASD from seven articles were studied in this meta-analysis. There were no significant differences in most sagittal balance parameters between the two groups, except for postoperative cervical lordosis (CL) (WMD -3.30, CI -5.91, − 0.69, P = 0.01).

Conclusions

Some sagittal balance parameters may be associated with the development of ASD after anterior cervical surgery. Sufficient restoration of CL may decrease the incidence of ASD. The results in present study needed to be expanded carefully and further high-quality studies are warranted to investigate the impact of sagittal balance on ASD.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2800-0) contains supplementary material, which is available to authorized users.

Cervical and Cervicothoracic Sagittal Alignment According to Roussouly Thoracolumbar Subtypes

STUDY DESIGN

Cross-sectional cohort.

OBJECTIVE

To determine normative radiographic sagittal cervical alignment in asymptomatic volunteers based on Roussouly thoracolumbar sagittal alignment subtypes.

SUMMARY OF BACKGROUND DATA

Comprehension of differences in cervicothoracic alignment with respect to variations in thoracolumbar alignment is limited.

METHODS

Asymptomatic adults were recruited and the following parameters measured: PI, PT, SS, LL, orbital tilt, orbital slope, occipital slope and incidence, occiput-C2 lordosis, C2-7 lordosis, occiput-C7 lordosis, CBVA, T1 slope, cervicothoracic alignment, T2-5 kyphosis, and C2-C7 sagittal vertebral alignment (SVA). Each was classified into one of Roussouly's four thoracolumbar subtypes and cervical alignment parameters were compared between groups.

RESULTS

Eighty-seven individuals [male-23; female-64; average age 49 ± 16 yr (22-77 yr)] were included for analysis. The four groups were not different by age, sex, and body mass index (BMI). Lumbopelvic parameters (PI, SS, PT, LL) were different between Roussouly types. Average values for all patients included: CBVA (-1 ± 9°), occiput-C2 lordosis (28 ± 9°), occiput-C7 lordosis (39 ± 14°), C2-7 lordosis (11 ± 14°), C2-7 SVA (21 ± 9 mm), T1 slope (25 ± 9°), C6-T4 angle (5 ± 8°), T2-5 angle (16 ± 7°), thoracic kyphosis (47 ± 13°). No sagittal radiographic alignment measurements of the cervical spine and cervicothoracic junction were different between groups, except for the global cervical lordosis (occiput-C7 Cobb), which was found to be lowest for Roussouly type 2 (35 ± 14°) and highest for type 4 (48 ± 14°) (P = 0.01). Mean C2-C7 sagittal Cobb, T2-T5 sagittal Cobb, and T1 slope were not different between groups.

CONCLUSIONS

In asymptomatic volunteers, normative sagittal alignment parameters of the cervical spine, cervicothoracic junction, and thoracic spine based on variations in thoracolumbar sagittal alignment, as proposed by Roussouly, are established. These data may guide surgical correction of cervicothoracic deformities to ensure appropriate restoration of normal cervicothoracic parameters to maintain good horizontal gaze and overall sagittal plane alignment.

LEVEL OF EVIDENCE

3.

Changes in the Sagittal Cranio-Cervical Posture Following a 12-Week Intervention Using a Simple Spinal Traction Device

STUDY DESIGN

Non-controlled clinical trial.

OBJECTIVE

To assess the efficacy of a simple home spinal traction device on sagittal cranio-cervical posture and related symptoms.

SUMMARY OF BACKGROUND DATA

Forward head protraction (FHP) and cranio-cervical malalignment were shown to be consequential in the development adverse musculoskeletal radiographic findings and symptoms in that region.

METHODS

Participants (n = 13, 18-36-year-old) were drawn from a mildly symptomatic population, all presented with cranio-cervical malalignment and considerable FHP. Participants used a simple home spinal traction device for 12 weeks, 10 min/d. Sagittal cervical radiographs and the SF36 health survey were obtained pre/post intervention and guideline compliance was recorded. Radiographic evaluation included typical measurements of sagittal cranio-cervical alignment and FHP (e.g., atlas plane line, vertical axis line, sagittal cranial angle, absolute rotation angle). Standard paired samples t tests, chi-squared, and effect size analyses were used to assess pre- and post-intervention changes.

RESULTS

Each of the key radiographic variables recorded significant moderate to very large positive changes as a result of the intervention. Similarly, Chi-squared analyses indicated that saggital cervical spine configuration tended to become more lordotic (P = 0.007), with four participants shifting from a kyphotic to a lordotic presentation. SF36 health survey data demonstrated mostly significant positive changes throughout all tested domains, and moderate positive changes were recorded across all radiographic cranio-cervical mesured paramenters (e.g., decreased FHP, increased cervical lordosis, and cranial extention). Participants indicated high level of protocol compliance.

CONCLUSION

This study has demonstrated that the unsupervised daily use of a simple home spinal traction device (Thoracic Pillow) proved effective in bringing positive plastic changes to the sagittal cranio-cervical alignment and reduction in symptoms in the tested population during a short intervention period.

LEVEL OF EVIDENCE

3.

Surgical Strategies to Prevent Adjacent Segment Disease in the Cervical Spine

The most popular approach to treating symptomatic cervical disk disease is anterior cervical discectomy and fusion. Although this procedure has significant long-term clinical success, it is associated with progressive adjacent segment degeneration with an annual incidence of ∼3%. Total disk arthroplasty was designed as an alternative to fusion that could preserve segmental motion at the operative level and potentially delay or prevent adjacent-level breakdown. The etiology of adjacent segment pathology (ASP) is multifactorial, and it is likely that most cases of ASP are unavoidable. When attempting to surgically prevent ASP, it is important to consider nonfusion alternatives, be judicious in one's level selection, and attempt to restore sagittal alignment. When ASP becomes a clinical problem, it is important to have an algorithm for how best to treat it.

Relationship Between Sagittal Balance and Axial Symptoms in Patients with Cervical Spondylotic Myelopathy Treated with Anterior Cervical Discectomy and Fusion

Purpose: The purpose of this study was to investigate the sagittal balance of the cervical spine and the clinical outcomes of anterior cervical discectomy and fusion (ACDF) for the treatment of cervical spondylotic myelopathy and to explore whether sagittal balance is related to the incidence of postoperative axial symptoms. Methods: Sixty-seven consecutive patients who underwent ACDF for the treatment of cervical spondylotic myelopathy from January 2014 to December 2016 were enrolled in our study. Sagittal balance parameters (global lordotic angle, segmented lordotic angle, T1 slope, and C2-7 sagittal vertical axis [C2-7 SVA] were recorded in the preoperative period and at 1 month, 3 months, and 1 year postoperatively. Clinical outcomes (JOA and NDI scores) and incidence of axial symptoms were also evaluated before and after surgery. Subgroup analysis included 20 patients with preoperative abnormal sagittal balance group (C2-7 SVA larger than 20 mm), and these patients were divided into two groups, namely axial symptom group and nonaxial symptom group. Result: The sagittal balance parameters (global lordotic angle, segmented lordotic angle, and TI slope) and the clinical outcomes after surgery significantly improved. The subgroup analysis within the preoperative abnormal sagittal balance group showed significant differences in postoperative and change in C2-7 SVA between patients with and without postoperative axial symptoms. Conclusion: ACDF can be applied to restore the sagittal alignment of the cervical spine and effectively improve clinical outcomes for the treatment of cervical spondylotic myelopathy. Sagittal balance improvement may be associated with the low incidence of postoperative axial symptoms for patients with abnormal cervical sagittal balance before surgery.

The effects of aging on the profile of the cervical spine

The study aims to investigate the effects of aging on the cervical spine.Outpatients in the study were grouped by age. The cervical spine image in the sagittal plane from participants in the supine position was acquired with MRI. Thoracic inlet angle (TIA), T1 slope (T1S), neck tilt (NT), and cervical angle (CC2-7) were measured.NT and TIA measured 41.84 ± 9.26 and 64.15 ± 10.72 in participants younger than 40, and 53.02 ± 9.52 and 72.09 ± 10.49 in participants older than 40 (P < .01). CC2-7 measured 6.11 ± 9.88 in participants younger than 40, significantly lower compared with participants older than 40, which measured 10.89 ± 11.02 (P = .003). TIS did not differ significantly between the 2 groups (P = .087). No significant difference was found in all measurements between the female and male participants. Age was moderately correlated with NT (r = 0.466, P < .01) and TIA (r = 0.512, P < .01), but weakly correlated with CC2-7 (r = 0.315, P < .01) and TIS (r = 0.210, P = .005). TIA showed a strong correlation with NT (r = 0.748, P < .01) and a moderate correlation with T1S (r = 0.458, P < .01). Lastly, T1S was strongly correlated with CC2-7 (r = 0.701, P < .01).The result showed that NT, CC2-7, and TIA, but not T1S, increased with age.

Increasing the cervical and lumbar lordosis is possible despite overt osteoarthritis and spinal stenosis using extension traction to relieve low back and leg pain in a 66-year-old surgical candidate: a CBP® case report

[Purpose] To present the case of the dramatic relief of low back pain, leg pain and disability in an older female with osteoarthritis, lumbar spinal stenosis and hypolordosis of the cervical and lumbar spine. [Participant and Methods] A 66-year-old female presented with chronic low back pain, right leg pain, numbness and weakness. Despite being recommended for surgery, the patient sought alternative treatment. The patient was treated with Chiropractic BioPhysics^® rehabilitation of the spine with the objective to increase the lumbar and cervical lordoses. Cervical and lumbar extension exercises and traction were performed as well as spinal manipulation. Treatment was performed approximately three times per week for 6.5 months. [Results] Re-assessment after treatment demonstrated significant reduction of low back pain, leg pain and other health improvements. X-rays showed structural improvements in the cervical and lumbar spine despite advanced osteoarthritis. [Conclusion] Lumbar and cervical hypolordosis subluxation may be increased in those with spinal deformity caused symptoms, despite the presence of osteoarthritis and degenerative stenosis of the spine. Spinal x-rays as used in the assessment and monitoring of patients being treated with contemporary spinal rehabilitation methods are not harmful and should be used for routine screening purposes.

Prognostic Value of Lordosis Decrease in Radiographic Adjacent Segment Pathology After Anterior Cervical Corpectomy and Fusion

While cervical lordosis alteration is not uncommon after anterior cervical arthrodesis, its influence on radiological adjacent segment pathology (RASP) is still unclear. Biomechanical changes induced by arthrodesis may contribute to ASP onset. To investigate the correlation between cervical lordosis decrease and RASP onset after anterior cervical corpectomy and fusion (ACCF) and to determine its biomechanical effect on adjacent segments after surgery, 80 CSM patients treated with ACCF were retrospectively studied, and a baseline finite element model of the cervical spine as well as post-operation models with normal and decreased lordosis were established and validated. We found that post-operative lordosis decrease was prognostic in predicting RASP onset, with the hazard ratio of 0.45. In the FE models, ROM at the adjacent segment increased after surgery, and the increase was greater in the model with decreased lordosis. Thus, post-operative cervical lordosis change significantly correlated with RASP occurrence, and it may be of prognostic value. The biomechanical changes induced by lordosis change at the adjacent segments after corpectomy may be one of the mechanisms for this phenomenon. Restoring a well lordotic cervical spine after corpectomy may reduce RASP occurrence and be beneficial to long-term surgical outcomes.

Survivorship Analysis of Clinical Adjacent-Segment Pathology After Single-Level Cervical Fusion

Background

Clinical adjacent-segment pathology (CASP) is an important problem after anterior cervical surgery. The purpose of this study was to predict prevalence of CASP and determine the possible risk factors for CASP after single-level anterior cervical discectomy and fusion surgery.

Material/Methods

We retrospectively reviewed a series of patients who underwent single-level cervical discectomy and fusion surgery (ACDF). Both basic and radiographic data of patients were collected. Life-table method and Kaplan-Meier analysis were used to calculate prevalence of CASP and disease-free survival rate. Cox analysis was performed to determine the predictive factors for it.

Results

A total of 256 patients were included in this study. The mean length of follow-up was 70.64 months. Among them, 31 patients were diagnosed as having CASP during follow-up. Nineteen of them were at the cephalad adjacent segment, and the other 12 were at the caudal segment. After ACDF procedures, 10.01% of patients developed new symptoms of CASP within 5 years, and the incidence increased to 23.89% after 10 years. The incidence rate of CASP was an average of 2.46% per year. Multivariate Cox regression analysis showed that congenital stenosis (hazard ratio [HR], 3.250; 95% confidence interval [CI], 1.538–6.867) and degeneration of adjacent segment (HR, 2.681; 95% CI, 1.259–5.709) were correlated with the incidence of CASP.

Conclusions

Patients with congenital stenosis and pre-existing degenerative changes of adjacent segments had a higher risk of developing CASP after single-level anterior cervical discectomy and fusion.

Kinematic analysis of the relationship between Modic changes and sagittal balance parameters in the cervical spine

The aim of this study is to investigate the relationship between the Modic changes (MCs) and sagittal parameters of the cervical spine.We conducted a retrospective review of 100 outpatients with magnetic resonance imaging (MRI) scans of the cervical spine (50 male and 50 female). MRI parameters were measured, including neck tilt, T1 slope (T1 ), thoracic inlet angle (TIA), and cervical lordosis (CL: Cobb C2-7). Patients were divided into 4 groups according to the presence or absence of MC and T1s, respectively: MC(+) and MC(-) groups, as well as H-T1s (T1s ≥25°) and L-T1s subgroups (T1s <25°). Relationships between the MC and sagittal alignment in the cervical spine and other parameters were evaluated via Spearman correlation coefficient. Radiologic parameters were compared between the MC(+) group and MC(-) group, and the prevalences of MC were compared between the H-T1s and L-T1s groups.T1s was significantly correlated with TIA and CL, with correlation coefficients of 0.562 and 0.725, respectively. T1 slope was significantly higher in patients with MC than those without MC (P = .041), and the prevalence of MC was higher in the H-T1s group than the L-T1s group (37.5% and 17.1%, respectively). However, the relationship between the parameters of sagittal balance and MC was not significant.The present study demonstrated that high T1 slope is a potential risk factor for the development of MC due to impaired sagittal balance, especially in the C5-6 cervical segment.

In-Depth Analysis on Influencing Factors of Adjacent Segment Degeneration After Cervical Fusion

BACKGROUND To explore the related influencing factors of adjacent segment degeneration (ASD) after cervical discectomy and fusion (ACDF). MATERIAL AND METHODS A retrospective analysis of 263 patients who underwent ACDF was carried out. Cervical x-ray and magnetic resonance imaging (MRI) were required before operation, after operation, and at the last follow-up. General information and some radiographic parameters of all patients were measured and recorded. According to the imaging data, patients were put into one of two groups: non-ASD group and ASD group. The differences between the two groups were compared by t-test and χ²-test, and the related influencing factors of ASD were analyzed by logistic regression. RESULTS In all, 138 patients had imaging ASD. Comparing the age, the postoperative cervical arc chord distance (po-CACD), and the plate to disc distance (PDD) of the two groups, differences were statistically significant (p<0.05). The gender, the fusion segment number, the pre-CACD, the pre-and-po CACD, the preoperative cervical spinal canal ratio, and the upper and lower disc height (DH) showed no statistical difference between the two groups (p>0.05). The results of logistic regression analysis showed that there were significant correlations in the following characteristics: age, postoperative po-CACD, and the PDD (p<0.05). Of all these characteristics, the correlation of age was the highest (R=1.820). CONCLUSIONS Age, po-CACD, and PDD were risk factors for ASD after ACDF. The older the operation age, the worse the recovery was of postoperative physiological curvature of cervical spine, and a PDD < 5 mm was more likely to lead to ASD.

Longitudinal Study of the Six Degrees of Freedom Cervical Spine Range of Motion During Dynamic Flexion, Extension, and Rotation After Single-level Anterior Arthrodesis

STUDY DESIGN

A longitudinal study using biplane radiography to measure in vivo intervertebral range of motion (ROM) during dynamic flexion/extension, and rotation.

OBJECTIVE

To longitudinally compare intervertebral maximal ROM and midrange motion in asymptomatic control subjects and single-level arthrodesis patients.

SUMMARY OF BACKGROUND DATA

In vitro studies consistently report that adjacent segment maximal ROM increases superior and inferior to cervical arthrodesis. Previous in vivo results have been conflicting, indicating that maximal ROM may or may not increase superior and/or inferior to the arthrodesis. There are no previous reports of midrange motion in arthrodesis patients and similar-aged controls.

METHODS

Eight single-level (C5/C6) anterior arthrodesis patients (tested 7 ± 1 months and 28 ± 6 months postsurgery) and six asymptomatic control subjects (tested twice, 58 ± 6 months apart) performed dynamic full ROM flexion/extension and axial rotation whereas biplane radiographs were collected at 30 images per second. A previously validated tracking process determined three-dimensional vertebral position from each pair of radiographs with submillimeter accuracy. The intervertebral maximal ROM and midrange motion in flexion/extension, rotation, lateral bending, and anterior-posterior translation were compared between test dates and between groups.

RESULTS

Adjacent segment maximal ROM did not increase over time during flexion/extension, or rotation movements. Adjacent segment maximal rotational ROM was not significantly greater in arthrodesis patients than in corresponding motion segments of similar-aged controls. C4/C5 adjacent segment rotation during the midrange of head motion and maximal anterior-posterior translation were significantly greater in arthrodesis patients than in the corresponding motion segment in controls on the second test date.

CONCLUSION

C5/C6 arthrodesis appears to significantly affect midrange, but not end-range, adjacent segment motions. The effects of arthrodesis on adjacent segment motion may be best evaluated by longitudinal studies that compare maximal and midrange adjacent segment motion to corresponding motion segments of similar-aged controls to determine if the adjacent segment motion is truly excessive.

LEVEL OF EVIDENCE

3.

Kinematic Magnetic Resonance Imaging Assessment of the Degenerative Cervical Spine: Changes after Anterior Decompression and Cage Fusion

Study Design A prospective cohort study. Objective Decompression and fusion of cervical vertebrae is a combined procedure that has a high success rate in relieving radicular symptoms and stabilizing or improving cervical myelopathy. However, fusion may lead to increased motion of the adjacent vertebrae and cervical deformity. Both have been postulated to lead to adjacent segment pathology (ASP). Kinematic magnetic resonance imaging (MRI) has been increasingly used to evaluate range of motion (ROM) of the cervical spine and ASP. Our objective was to measure ASP, cervical curvature, and ROM of individual segments of the cervical spine using kinematic MRI before and 24 months after monosegmental cage fusion. Methods Eighteen patients who had single-level interbody fusion were included. ROM (using kinematic MRI) and degeneration, spinal stenosis, and cervical curvature were measured preoperatively and 24 months postoperatively. Results Using kinematic MRI, segmental motion of the cervical segments was measured with a precision of less than 3 degrees. The cervical fusion did not affect the ROM of adjacent levels. However, pre- and postoperative ROM was higher at the levels immediately adjacent to the fusion level compared with those further away. In addition, at 24 months postoperatively, the number of cases with ASP was higher at the levels immediately adjacent to fusion level. Conclusions Using kinematic MRI, ROM after spinal fusion can be measured with high precision. Kinematic MRI can be used not only in clinical practice, but also to study intervention and its effect on postoperative biomechanics and ASP of cervical vertebrae.

Prevalence of adjacent segment disease following cervical spine surgery: A PRISMA-compliant systematic review and meta-analysis

Prevalence estimates of adjacent segment degeneration (ASD) following cervical spine surgery varied greatly in current studies. We conducted a systematic review and meta-analysis to summarize the point prevalence of ASD after cervical spine surgery.

METHODS

Comprehensive electronic searches of PubMed, Embase, Web of Knowledge, and Cochrane Library databases were conducted to identify any study published from initial state to January 2016. Those reporting the prevalence of ASD after cervical surgery were included. A random-effects model was used to estimate the prevalence of radiographic ASD, symptomatic ASD, and reoperation ASD. Univariate meta-regression analyses were conducted to explore the potential associations between prevalence and length of follow-up. All analyses were performed using R version 3.2.3 (R Foundation for Statistical Computing).

RESULTS

A total of 83 studies were included in the meta-analysis. The prevalence of radiographic ASD, symptomatic ASD, and reoperation ASD after cervical surgery was 28.28% (95% confidence interval [CI], 20.96-36.96), 13.34% (95% CI, 11.06-16.00), and 5.78% (95% CI, 4.99-6.69), respectively, in a general analysis. It was found 2.79%, 1.43%, and 0.24% additions per year of follow-up in the incidence of radiographic ASD, symptomatic ASD, and reoperation ASD, respectively.

CONCLUSION

This meta-analysis provides some details about the prevalence of radiographic ASD, symptomatic ASD, and reoperation ASD after cervical spine surgery. However, the results of this meta-analysis should be interpreted with caution because of the heterogeneity among the studies.

Adjacent Segment Pathology after Anterior Cervical Fusion

Anterior cervical fusion has become a standard of care for numerous pathologic conditions of the cervical spine. However, subsequent development of clinically significant disc disease at levels adjacent to fused discs is a serious long-term complication of this procedure. As more patients live longer after surgery, it is foreseeable that adjacent segment pathology (ASP) will develop in increasing numbers of patients. Also, ASP has been studied more intensively with the recent popularity of motion preservation technologies like total disc arthroplasty. The true nature and scope of ASP remains poorly understood. The etiology of ASP is most likely multifactorial. Various factors including altered biomechanical stresses, surgical disruption of soft tissue and the natural history of cervical disc disease contribute to the development of ASP. General factors associated with disc degeneration including gender, age, smoking and sports may play a role in the development of ASP. Postoperative sagittal alignment and type of surgery are also considered potential causes of ASP. Therefore, a spine surgeon must be particularly careful to avoid unnecessary disruption of the musculoligamentous structures, reduced risk of direct injury to the disc during dissection and maintain a safe margin between the plate edge and adjacent vertebrae during anterior cervical fusion.

Sagittal alignment of the spine-pelvis-lower extremity axis in patients with severe knee osteoarthritis: A radiographic study

Objectives

Normal sagittal spine-pelvis-lower extremity alignment is crucial in humans for maintaining an ergonomic upright standing posture, and pathogenesis in any segment leads to poor balance. The present study aimed to investigate how this sagittal alignment can be affected by severe knee osteoarthritis (KOA), and whether associated changes corresponded with symptoms of lower back pain (LBP) in this patient population.

Methods

Lateral radiograph films in an upright standing position were obtained from 59 patients with severe KOA and 58 asymptomatic controls free from KOA. Sagittal alignment of the spine, pelvis, hip and proximal femur was quantified by measuring several radiographic parameters. Global balance was accessed according to the relative position of the C7 plumb line to the sacrum and femoral heads. The presence of chronic LBP was documented. Comparisons between the two groups were carried by independent samples t-tests or chi-squared test.

Results

Patients with severe KOA showed significant backward femoral inclination (FI), hip flexion, forward spinal inclination, and higher prevalence of global imbalance (27.1% versus 3.4%, p < 0.001) compared with controls. In addition, patients with FI of 10° (n = 23) showed reduced lumbar lordosis and significant forward spinal inclination compared with controls, whereas those with FI > 10° (n = 36) presented with significant pelvic anteversion and hip flexion. A total of 39 patients with KOA (66.1%) suffered from LBP. There was no significant difference in sagittal alignment between KOA patients with and without LBP.

Conclusions

The sagittal alignment of spine-pelvis-lower extremity axis was significantly influenced by severe KOA. The lumbar spine served as the primary source of compensation, while hip flexion and pelvic anteversion increased for further compensation. Changes in sagittal alignment may not be involved in the pathogenesis of LBP in this patient population.

Cite this article: W. J. Wang, F. Liu, Y.W. Zhu, M.H. Sun, Y. Qiu, W. J. Weng. Sagittal alignment of the spine-pelvis-lower extremity axis in patients with severe knee osteoarthritis: A radiographic study. Bone Joint Res 2016;5:198–205. DOI:10.1302/2046-3758.55.2000538.

Is Cervical Sagittal Imbalance a Risk Factor for Adjacent Segment Pathomechanics After Multilevel Fusion?

STUDY DESIGN

A biomechanical study using human spine specimens.

OBJECTIVE

The aim of this study was to assess whether the presence of cervical sagittal imbalance is an independent risk factor for increasing the mechanical burden on discs adjacent to cervical multilevel fusions.

SUMMARY OF BACKGROUND DATA

The horizontal offset distance between the C2 plumbline and C7 vertebral body (C2-C7 Sagittal Vertical Axis (SVA)) or the angle made with vertical by a line connecting the C2 and C7 vertebral bodies (C2-C7 tilt angle) are used as radiographic measures to assess cervical sagittal balance. There is level III clinical evidence that sagittal imbalance caused by kyphotic fusions or global spinal sagittal malalignment may increase the risk of adjacent segment pathology.

METHODS

Thirteen human cadaveric cervical spines (Occiput-T1; age: 50.6 years; range: 21-67) were tested first in the native intact state and then after instrumentation across C4-C6 to simulate in situ two-level fusion. Specimens were tested using a previously validated experimental model that allowed measurement of spinal response to prescribed imbalance. The effects of fusion on segmental angular alignments and intradiscal pressures in the C3-C4 and C6-C7 discs, above and below the fusion, were evaluated at different magnitudes of C2-C7 tilt angle (or C2-C7 SVA).

RESULTS

When compared with the pre-fusion state, in situ fusion across C4-C6 segments required increased flexion angulation and resulted in increased intradiscal pressure at the C6-C7 disc below the fusion in order to accommodate the same increase in C2-C7 tilt angle or C2-C7 SVA (P < 0.05). The adjacent segment mechanical burden due to fusion became greater with increasing C2-C7 tilt angle or SVA.

CONCLUSION

Cervical sagittal imbalance arising from regional and/or global spinal sagittal malalignment may play a role in exacerbating adjacent segment pathomechanics after multilevel fusion and should be considered during surgical planning.

LEVEL OF EVIDENCE

N/A.

Radiologic Findings and Risk Factors of Adjacent Segment Degeneration after Anterior Cervical Discectomy and Fusion : A Retrospective Matched Cohort Study with 3-Year Follow-Up Using MRI

Objective

The purpose of this study was to figure out the radiologic findings and risk factors related to adjacent segment degeneration (ASD) after anterior cervical discectomy and fusion (ACDF) using 3-year follow-up radiography, computed tomography (CT), and magnetic resonance image (MRI).

Methods

A retrospective matched comparative study was performed for 64 patients who underwent single-level ACDF with a cage and plate. Radiologic parameters, including upper segment range of motion (USROM), lower segment range of motion (LSROM), upper segment disc height (UDH), and lower segment disc height (LDH), clinical outcomes assessed with neck and arm visual analogue scale (VAS), and risk factors were analyzed.

Results

Patients were categorized into the ASD (32 patients) and non-ASD (32 patients) group. The decrease of UDH was significantly greater in the ASD group at each follow-up visit. At 36 months postoperatively, the difference for USROM value from the preoperative one significantly increased in the ASD group than non-ASD group. Preoperative other segment degeneration was significantly associated with the increased incidence of ASD at 36 months. However, pain intensity for the neck and arm was not significantly different between groups at any post-operative follow-up visit.

Conclusion

The main factor affecting ASD is preoperative other segment degeneration out of the adjacent segment. In addition, patients over the age of 50 are at higher risk of developing ASD. Although there was definite radiologic degeneration in the ASD group, no significant difference was observed between the ASD and non-ASD groups in terms of the incidence of symptomatic disease.

Narrative review of the in vivo mechanics of the cervical spine after anterior arthrodesis as revealed by dynamic biplane radiography

Arthrodesis is the standard of care for numerous pathologic conditions of the cervical spine and is performed over 150,000 times annually in the United States. The primary long-term concern after this surgery is adjacent segment disease (ASD), defined as new clinical symptoms adjacent to a previous fusion. The incidence of adjacent segment disease is approximately 3% per year, meaning that within 10 years of the initial surgery, approximately 25% of cervical arthrodesis patients require a second procedure to address symptomatic adjacent segment degeneration. Despite the high incidence of ASD, until recently, there was little data available to characterize in vivo adjacent segment mechanics during dynamic motion. This manuscript reviews recent advances in our knowledge of adjacent segment mechanics after cervical arthrodesis that have been facilitated by the use of dynamic biplane radiography. The primary observations from these studies are that current in vitro test paradigms often fail to replicate in vivo spine mechanics before and after arthrodesis, that intervertebral mechanics vary among cervical motion segments, and that joint arthrokinematics (i.e., the interactions between adjacent vertebrae) are superior to traditional kinematics measurements for identifying altered adjacent segment mechanics after arthrodesis. Future research challenges are identified, including improving the biofidelity of in vitro tests, determining the natural history of in vivo spine mechanics, conducting prospective longitudinal studies on adjacent segment kinematics and arthrokinematics after single and multiple-level arthrodesis, and creating subject-specific computational models to accurately estimate muscle forces and tissue loading in the spine during dynamic activities.

Outcomes of secondary laminoplasty for patients with unsatisfactory results after anterior multilevel cervical surgery

Objective

To investigate the causes for failed anterior cervical surgery and the outcomes of secondary laminoplasty.

Methods

Seventeen patients failed anterior multilevel cervical surgery and the following conservative treatments between Feb 2003 and May 2011 underwent secondary laminoplasty. Outcomes were evaluated by the Japanese Orthopaedic Association (JOA) Scale and visual analogue scale (VAS) before the secondary surgery, at 1 week, 2 months, 6 months, and the final visit. Cervical alignment, causes for revision and complications were also assessed.

Results

With a mean follow-up of 29.7±12.1 months, JOA score, recovery rate and excellent to good rate improved significantly at 2 months (p<0.05) and maintained thereafter (p>0.05). Mean VAS score decreased postoperatively (p<0.05). Lordotic angle maintained during the entire follow up (p>0.05). The causes for secondary surgery were inappropriate approach in 3 patients, insufficient decompression in 4 patients, adjacent degeneration in 2 patients, and disease progression in 8 patients. Complications included one case of C5 palsy, axial pain and cerebrospinal fluid leakage, respectively.

Conclusion

Laminoplasty has satisfactory results in failed multilevel anterior surgery, with a low incidence of complications.

Relationship between cervical sagittal alignment and quality of life in ankylosing spondylitis

PURPOSE

Little information is available on the relationship between cervical sagittal alignment and health-related quality of life (HRQOL) in ankylosing spondylitis (AS) patients. The aim of this study was to identify relationships between cervical sagittal alignment and HRQOL in AS.

METHODS

The study and control groups comprised 102 AS patients (15 women and 87 men) and age- and sex-matched 50 controls, respectively. All underwent anteroposterior and lateral radiographs and completed clinical questionnaires. The radiographic parameters examined were C2-C7 lordosis, C2-C7 sagittal vertical axis (SVA), T1 slope and T1 slope minus C2-C7 lordosis (TS-CL). A visual analogue scale (VAS 0-10) score for neck pain, the neck disability index (NDI), neck pain and disability (NPAD) scale and bath ankylosing spondylitis disease activity index (BASDAI) were administered to evaluate QOL. Statistical analysis was performed to determine the significances of differences between the study and control groups. In addition, correlations between radiological parameters and clinical questionnaires were sought.

RESULTS

AS patients and controls were found to be different significantly in terms of C2-C7 SVA, T1 slope, and TS-CL. However, no significant intergroup difference was observed for C2-C7 lordosis (P > 0.05). Correlation analysis revealed significant relationships between radiographic parameters and QOL. Multiple regression analysis was performed to identify predictors of QOL, and the results obtained revealed that C2-C7 SVA significantly predicted VAS, NDI, and NPAD scores and that age predicted NPAD score.

CONCLUSIONS

Cervical sagittal parameters were found to be significantly different in AS patients and normal controls. Correlation analysis revealed significant relationships between radiographic parameters and QOL. In particular, C2-C7 SVA was found to be a significant predictor of QOL in AS patient.

Sagittal alignment as a predictor of clinical adjacent segment pathology requiring surgery after anterior cervical arthrodesis

BACKGROUND CONTEXT

Postoperative malalignment of the cervical spine may alter cervical spine mechanics and put patients at risk for clinical adjacent segment pathology requiring surgery.

PURPOSE

To investigate whether a relationship exists between cervical spine sagittal alignment and clinical adjacent segment pathology requiring surgery (CASP-S) following anterior cervical fusion (ACF).

STUDY DESIGN

Retrospective matched study.

PATIENT SAMPLE

A total of 122 patients undergoing ACF between 1996 and 2008 were identified, with a minimum of 2 years of follow-up.

OUTCOME MEASURES

Radiographs were reviewed to measure the sagittal alignment using C2 and C7 sagittal plumb lines, distance from the fusion mass plumb line to the C2 and C7 plumb lines, the alignment of the fusion mass, caudally adjacent disc angle, the sagittal slope angle of the superior end plate of the vertebra caudally adjacent to the fusion mass, T1 sagittal angle, overall cervical sagittal alignment, and curve patterns by Katsuura classification.

METHODS

A total of 122 patients undergoing ACF between 1996 and 2008 were identified, with a minimum of 1 year of follow-up. Patients were divided into groups according to the development of CASP (control/CASP-S) and by number/location of levels fused. Radiographs were reviewed to measure the sagittal alignment using C2 and C7 sagittal plumb lines, distance from the fusion mass plumb line to the C2 and C7 plumb lines, the alignment of the fusion mass, caudally adjacent disc angle, the sagittal slope angle of the superior end plate of the vertebra caudally adjacent to the fusion mass, T1 sagittal angle, overall cervical sagittal alignment, and curve patterns by Katsuura classification. Appropriate statistical tests were performed to calculate relationships between the variables and the development of CASP-S. No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this article.

RESULTS

The groups were similar with regard to demographic and surgical variables. Lordosis was preserved in 82% (50/61) of the control group but in only 66% (40/61) of the CASP-S group (p=.033). More patients with a straight curve pattern developed CASP-S. The distance from the C2 to the C7 plumb line and T1 sagittal slope angle were lower in the CASP-S group with C5-C6 fusions compared with the control group. Also, the distance from C5-C6 fusion mass to C7 plumb line and C7 sagittal slope angle were lower in the CASP-S group with C5-C6 fusions.

CONCLUSIONS

Our results suggest that malalignment of the cervical spine following an ACF at C5-C6 has an effect on the development of clinical adjacent segment pathology requiring surgery.

Long-term outcome of the Cloward procedure for single-level cervical degenerative spondylosis. Clinical and radiological assessment after a 22-year mean follow-up

PURPOSE

To evaluate the long-term outcomes of the classical Cloward procedure in single-level cervical spondylosis.

METHODS

A retrospective study of 28 patients who were affected by cervical degenerative spondylosis at C4-C7 segments and treated by the Cloward technique at a single level from 1985-1995 was conducted. The average follow-up period was 22 years (range, 17-27 years). Preoperative clinical complaints were recorded and compared to the current clinical status. Preoperative, 3-6 months postoperative and a current radiographic study were analysed by evaluating the segmental and global sagittal alignment of the cervical spine as well as the occurrence of adjacent disc degeneration.

RESULTS

The most frequently operated segment was C5-C6 (57.1 %), followed by C6-C7 (32.1 %) and C4-C5 (7.1 %). Pain relief and symptom recovery experienced 3-6 months following the surgery was maintained at the most recent follow-up in 85 % of patients. Adjacent disc degeneration was detected in a total of 17 cases (60.7 %). Overall, a group of 14 cases (50 %) had increased lordosis at C2-C7 at the most recent follow-up, with a mean gain of 1.5º Cobb. According to Odom's criteria, 17 patients (60.8 %) presented with excellent clinical outcome, 6 (21.4 %) presented with good outcome, 5 had a (17.8 %) fair outcome, and none had a poor outcome.

CONCLUSIONS

The Cloward technique provided excellent long-term clinical outcome in the treatment of single-level cervical degenerative spondylosis. There were no major alterations of the cervical sagittal balance, and the development of adjacent segment disease (ASD) was not specifically associated with the previous surgery.

Evidence-based analysis of adjacent segment degeneration and disease after ACDF: a systematic review

BACKGROUND CONTEXT

Follow-up studies of patients undergoing anterior cervical discectomy and interbody fusion (ACDF) have demonstrated varying degrees of radiographic degeneration at adjacent levels, with most cases being asymptomatic (adjacent segment degeneration, ASDeg) and far fewer being symptomatic (adjacent segment disease, ASDz). Controversy remains as to whether these conditions are related to altered biomechanics or represent the natural history of cervical spondylosis at the adjacent segment.

PURPOSE

To provide an evidence-based analysis of the peer-reviewed literature on clinical studies of ASDeg and ASDz after ACDF.

STUDY DESIGN/SETTING

Systematic review of existing literature.

METHODS

The MEDLINE database was queried for clinical studies reporting ASDeg and/or ASDz after ACDF. Articles written in the English language with a minimum follow-up of 2 years were independently reviewed and analyzed by two authors, and the level of evidence was assigned. Data were pooled to generate summary outcomes and organized by number of levels, technique, and graft/implants.

RESULTS

Of the 238 articles returned from the MEDLINE database query, 14 met inclusion criteria. An average of 168 patients was enrolled per study with an average follow-up of 106.5 months. Graft materials, cage design, plate fixation system, and length of fusion varied widely. Additionally, no clear standard was seen for radiographic assessment modalities (eg, plain lateral radiograph, flexion-extension radiographs, computed tomography, or magnetic resonance imaging). Validated clinical outcome measures were used in 43% (6/14) of the studies. The average incidence of ASDeg was 47.33% (459.14/970) with a range from 16% to 96%. The frequency-weighted average for ASDz was 11.99% (263.70/2,199) with a range from 1.80% to 36.00%. Follow-up ranged from 24 to 296 months with no reliable commonalities, which prohibited a meta-analysis.

CONCLUSIONS

This review highlights the heterogeneous methodology of the peer-reviewed literature on ASDeg and ASDz after ACDF and the paucity of high-level clinical data published on these conditions. Despite the low level of evidence to define the incidence of ASDeg and ASDz, it is clear that radiographic ASDeg is more common than symptomatic ASDz, indicating that adjacent segment pathology remains subclinical in a large subset of patients. This analysis underscores the need for standardized radiographic measures in the assessment of ASDeg and validated clinical outcome measures for ASDz after ACDF. Consistent methodology and multi-surgeon collaboration may improve the quality of clinical data on ASDeg and ASDz and elucidate the true etiology and incidence of these conditions.

Congenital stenosis and adjacent segment disease in the cervical spine

Symptomatic adjacent segment disease (ASD) after anterior cervical fusion (ACF) is reported in 25% of patients at 10 years postoperatively. Debate continues as to whether this degeneration is due to the natural history of the disk or the changed biomechanics after ACF. This study explored whether congenital stenosis predisposes patients to an increased incidence of ASD after ACF. A retrospective review of 635 patients with myelopathy or radiculopathy was performed; 364 patients had complete records for review. Patients underwent 1- to 5-level ACF (94 one-level, 145 two-level, 79 three-level, 45 four-level, and 1 five-level). Radiographs were evaluated for bony congenital stenosis using validated parameters, and ASD was measured according to Hilibrand's criteria and correlated with symptomatic ASD. Congenital stenosis was found in 21.7% of patients and radiographic ASD in 33.5%, with a significant association between these parameters. However, symptomatic ASD occurred in 11.8% of patients; no association between congenital stenosis and symptomatic ASD or myelopathy and ASD was found. Clinical results demonstrated excellent or good Robinson scores in 86.2% of patients and Odom scores in 87% of patients. Despite mostly excellent to good outcomes, symptomatic ASD is common after ACF. Although congenital stenosis appears to increase the incidence of radiographic ASD, it does not appear to predict symptomatic ASD.

The effect of age on cervical sagittal alignment: normative data on 100 asymptomatic subjects

STUDY DESIGN

Retrospective study.

OBJECTIVE

To determine age-related changes in cervical sagittal alignment using whole-spine standing radiographs in asymptomatic adults.

SUMMARY OF BACKGROUND DATA

Modern surgical techniques have emphasized the importance of maintaining proper sagittal alignment. But there is a paucity of literature investigating age-related changes in cervical sagittal alignment.

METHODS

One hundred healthy unoperated adults who were free of spinal problems obtained whole-spine standing radiographs. They consisted of 2 groups divided by age: those in their 20s and those older than 60 years. Each group had an equal ratio of males and females. Distances from C2 as well as C7 plumb lines to the following points were measured: thoracic and lumbar apex as well as the posterior superior corner of the S1 vertebral body. In addition, Cobb angles for C0-C2, C2-C7, thoracic kyphotic angle, lumbar lordotic angle, and T1 sagittal slope angles were measured.

RESULTS

The distance between the C2 and C7 plumb lines did not vary with age. The thoracic apex shifted caudally from T6 in the younger group to T7 in the older group. The most common lumbar apex was L4 for both groups. The distance from C2, as well as C7 plumb lines to the posterior superior corner of the S1 vertebral body, as well as the thoracic apex increased significantly in the older group. On the contrary, the distance from the 2 plumb lines to the lumbar apex decreased in the older group. Also, C2-C7 angle increased and T1 sagittal slope angle decreased in the older group compared with the younger group. However, no difference was found for the other Cobb angles between the 2 groups.

CONCLUSION

The distances between the plumb lines from C2 and C7 were maintained but C2-C7 sagittal angle increased with aging.

Prevalence of adjacent segment degeneration after spine surgery: a systematic review and meta-analysis

STUDY DESIGN

Systematic review of published prevalence of adjacent segment degeneration (ASD) after spine surgery.

OBJECTIVE

To evaluate the prevalence of ASD in patients after cervical and lumbar spine surgery.

SUMMARY OF BACKGROUND DATA

ASD is a common complication after spine surgery in long-term follow-up. A large body of literature has been reported on the topic, but no meta-analysis of the epidemiological data on ASD has been published

METHODS

We searched the MEDLINE until March 2012 published in English language that reported the prevalence of ASD after spine surgery. We determined the ASD rates by calculating proportions and 95% confidence interval (CI) for each study and then pooled the data to derive a pooled proportion and 95% CI.

RESULTS

A total of 94 studies with 34,716 patients from 19 countries were included. The occurrence of radiograph ASD ranged from 4.8% to 92.2%, and the pooled prevalence was 29.3% (95% CI, 22.7%-35.8%) by the random-effects model. The occurrence of symptoms ASD ranged from 0.0% to 30.3%, and the pooled prevalence was 7.4% (95% CI, 6.4%-8.5%). In cervical position, the occurrence of radiograph ASD and symptoms ASD was 32.8% (95% CI, 17.8%-47.9%) and 6.3% (95% CI, 4.8%-7.8%); in lumbar position, the occurrence of radiograph ASD and symptoms ASD was 26.6% (95% CI, 21.3%-31.9%) and 8.5% (95% CI, 6.4%-10.7%). In the 0.5- to 2- or less, more than 2- to 5- or less, and more than 5- to 20- or less year diagnosis time, the radiograph ASD prevalence was 21.8% (16.0%-27.6%), 33.6% (21.8%-45.4%), and 37.4% (10.7%-64.1%), respectively; and the symptoms ASD prevalence was 6.5% (4.8%-8.1%), 12.1% (8.2%-16.0%), and 3.2% (2.5%-4.0%), respectively.

CONCLUSION

Spine surgery is associated with significant risk of ASD. These figures may be useful in the estimation of the burden of the ASD after spine surgery.