Correlation between cervical lordosis and adjacent segment pathology after anterior cervical spinal surgery

A Novel Intraoperative Posture-Adjustment Apparatus for Correction of Cervical Lordosis in Anterior Cervical Surgery

OBJECTIVE

Cervical alignment is a crucial factor related to the success of anterior cervical surgical procedures. In patients with severe spinal cord compression, a traditional neck pillow (TNP) may not adequately correct cervical position during surgery. Therefore, the aim of this study was to introduce this innovative intraoperative posture-adjustment apparatus (IPAA), and explored its clinical and radiological results in cervical angle correction against TNP in patients who had undergone anterior cervical surgery.

METHODS

The clinical and radiological data of 86 patients who underwent anterior cervical surgery with a minimum follow-up period of 1 year were retrospectively reviewed. Of these, 58 patients underwent IPAA, whereas 28 underwent TNP. Radiological parameters such as the degree of C2-C7 lordosis (CL), functional spinal unit angle (FSUA), C7 slope (C7S), fusion rate, and adjacent segment disease (ASD) were recorded and compared between the groups. Clinical outcomes including the Japanese Orthopaedic Association (JOA), neck disability index (NDI), visual analogue scale (VAS) for neck and arm were recorded. Complications such as kyphosis, dysphagia, Braden Scale score, revision surgery, hematoma, cerebrospinal fluid leakage, wound infection, and deep venous thrombosis were also recorded. The independent t-test or Mann-Whitney U test was used to compare continuous data, and categorical variables were assessed using the Pearson's chi-square test or Fisher's exact test.

RESULTS

Compared with the pre-operative data, the post-operative CL, FSUA, and C7S were significantly increased in both groups. CL, FSUA, and C7S in the IPAA group (14.44 ± 4.94°, 7.36 ± 2.91°, 16.54 ± 4.63°) were significantly higher than those in the TNP group (7.17 ± 8.19°, 4.99 ± 5.36°, 14.19 ± 4.48°; P < 0.05). Although there were no significant differences between the groups in terms of VAS arm and JOA scores, the post-operative and final follow-up NDI and VAS neck scores in the IPAA group were significantly lower than those in the TNP group (p < 0.05). At the last follow-up, the TNP group had significantly more kyphotic patients than the IPAA group (2 vs. 0, p = 0,041). There was no significant difference between the groups in terms of fusion rate, ASD, or complications such as dysphagia, Braden's Scale score, revision surgery, hematoma, cerebrospinal fluid leakage, wound infection, or deep venous thrombosis.

CONCLUSION

IPAA was shown to be more effective than TNP in adjusting cervical alignment (CL, FSUA, and C7S). These findings suggest that IPAA could be used as an alternative way to TNP in neck setting and cervical alignment adjustment and IPAA could potentially improve clinical outcomes after anterior cervical surgery.

The Effect of Subsidence on Segmental and Global Lordosis at Long-term Follow-up After Anterior Cervical Discectomy and Fusion

OBJECTIVE

Subsidence following anterior cervical discectomy and fusion (ACDF) may lead to disruptions of cervical alignment and lordosis. The purpose of this study was to evaluate the effect of subsidence on segmental, regional, and global lordosis.

METHODS

This was a retrospective cohort study performed between 2016-2021 at a single institution. All measurements were performed using lateral cervical radiographs at the immediate postoperative period and at final follow-up greater than 6 months after surgery. Associations between subsidence and segmental lordosis, total fused lordosis, C2-7 lordosis, and cervical sagittal vertical alignment change were determined using Pearson correlation and multivariate logistic regression analyses.

RESULTS

One hundred thirty-one patients and 244 levels were included in the study. There were 41 one-level fusions, 67 two-level fusions, and 23 three-level fusions. The median follow-up time was 366 days (interquartile range, 239-566 days). Segmental subsidence was significantly negatively associated with segmental lordosis change in the Pearson (r = -0.154, p = 0.016) and multivariate analyses (beta = -3.78; 95% confidence interval, -7.15 to -0.42; p = 0.028) but no associations between segmental or total fused subsidence and any other measures of cervical alignment were observed.

CONCLUSION

We found that subsidence is associated with segmental lordosis loss 6 months following ACDF. Surgeons should minimize subsidence to prevent long-term clinical symptoms associated with poor cervical alignment.

Fatty infiltration in cervical extensor muscle: is there a relationship with cervical sagittal alignment after anterior cervical discectomy and fusion?

Purpose

To investigate the relationship between the preoperative paraspinal Goutalier grade of fatty infiltration and postoperative cervical sagittal alignment in patients undergoing anterior cervical discectomy and fusion (ACDF).

Methods

A total of 101 patients who underwent single-level ACDF with the Zero-profile implant system between March 2011 and April 2020 were included in this study. Cervical sagittal alignment parameters, including the C2-C7 Cobb angle, functional spinal unit (FSU) angle, cervical sagittal vertical axis (SVA), and T1 slope (T1S), were assessed. Preoperative magnetic resonance images were used to classify patients according to Goutalier grade. Clinical outcomes including Neck Disability Index (NDI) scores, Japanese Orthepaedic Association (JOA) scores and Visual Analogue Scale (VAS) scores were collected and analyzed.

Results

According to the Goutalier grade, 33 patients were classified as Goutalier 0–1 (Group A), 44 were classified as Goutalier 1.5–2 (Group B), and 24 were classified as Goutalier 2.5–4.0 (Group C). The mean age among the three groups showed significant differences (P = 0.007). At the last follow-up, the C2-C7 Cobb angle, FSU angle, and T1S improved after the surgery among the groups. Although there were varying degrees of loss of curvature among the different groups during the follow-up period, the postoperative cervical sagittal alignment parameters demonstrated no statistical differences among the three groups (P > 0.05). In addition, patients in all groups experienced significant relief of their symptoms, and the clinical scores were comparable among the groups (P > 0.05).

Conclusion

The complex nature of anterior cervical surgery requires surgical attention both in decompression and sagittal alignment. Our study demonstrates satisfactory postoperative cervical sagittal alignment of patients despite different grades of fatty infiltration of the multifidus muscle following single-level ACDF. Based on our results, the improvement and maintenance of cervical sagittal alignment after ACDF remains a complex problem that spine surgeons should consider before surgery.

THE PREVALENCE OF HETEROTOPIC OSSIFICATION AMONG PATIENTS AFTER CERVICAL DISK ARTHROPLASTY AT 5 YEARS

ABSTRACT Objective: This study was designed to evaluate the prevalence and grading of heterotopic ossification (HO) at five years, among patients after cervical disk arthroplasty (CDA). Methods: The CDA procedure with Activ C and M6-C prostheses was performed on 127 patients. The mean age of the cohort of patients was 38.4 years (range 18-49). The mean follow-up time was 58.4 months, ranging from 51 to 66 months. Results: Grade 1 ossifications were present in 11 (8.6 %) levels. A total of 45 (35.4 %) segments showed grade 2 HO. HO that led to restrictions in range of motion were present in 13 (10.2 %) cases. Five years after surgery, 9 (7.0 %) patients with grade 4 ossifications were found only in the M6-C artificial disk prosthesis group. In the analysis of patient survival following the occurrence of HO, all patients showed median survival of 28.3±5.6 months. The group that received the Activ C artificial disk prosthesis showed statistically longer survival (49.5±7.8 months) than the M6-C disk group. Conclusions: In our study 61.4% of patients exhibited HO after a mean follow-up of 58.4 months. In the analysis of patient survival after HO, all patients showed median survival of 28.3±5.6 months. The group that received the Activ C artificial disk prosthesis showed statistically longer survival (49.5±7.8 months) than the M6-C disk group. Level of evidence III; Cross-sectional Observational Study.

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.

Is there a difference in the outcomes of anterior cervical discectomy and fusion among female patients with different menopausal statuses?

BACKGROUND

The surgical outcomes of anterior cervical discectomy and fusion (ACDF) in female patients according to menopausal status remain unclear. The objective of this study was to investigate the differences in these outcomes among female patients with different menopausal statuses.

METHODS

Ninety-one patients undergoing single-level or consecutive two-level ACDF with a minimum 12-month postoperative follow-up were included in this study. There were 38 patients in the premenopausal group, 28 patients in the early postmenopausal group, and 25 patients in the late postmenopausal group. The clinical outcomes were evaluated by means of the neck disability index (NDI) scores, Japanese Orthopedic Association (JOA) scores, and visual analog scale (VAS) scores. Radiological parameters included cervical lordosis (CL), the functional spinal unit (FSU) angle, range of motion (ROM) of the total cervical spine, ROM of the FSU, anterior and posterior FSU height, implant subsidence, adjacent segment degeneration (ASD), and Hounsfield unit (HU) values.

RESULTS

All groups showed significant improvements in their JOA, VAS, and NDI scores (P < 0.05). The differences in preoperative and final follow-up CL, ROM of C2-7, FSU angle, and ROM of FSU were not statistically significant among the three groups (P > 0.05). The anterior FSU height loss rate showed a significant difference (P = 0.043), while there was no difference in the posterior FSU height loss rate (P = 0.072). The fusion rates in the early and late postmenopausal groups were consistently lower than those in the premenopausal group during the follow-up period. All patients had satisfactory outcomes at the final follow-up.

CONCLUSION

There were no significant differences in clinical or other related outcomes of single-level or consecutive two-level ACDF in the long term among female patients with different menopausal statuses. However, the early bony fusion rates and anterior FSU height loss rates were poorer in late postmenopausal patients than in premenopausal or early postmenopausal patients. Hence, importance should be attached to the protection of late postmenopausal patients in the early postoperative period to guarantee solid bony fusion.

Comparison of Clinical and Imaging Outcomes of Cervical Disc Replacement in Patients with Different Hounsfield Units

OBJECTIVE

To compare clinical and imaging outcomes after cervical disc replacement (CDR) in patients with different Hounsfield units (HU).

METHODS

We performed a retrospective study of patients with cervical degenerative disc disease treated by 1-level and 2-level Prestige-LP arthroplasty. The patients were divided into group A (HU <320), group B (HU 320-347), and group C (HU >347) according to the results of cervical vertebral HU measurement in the literature, and the clinical and radiographic results were compared among the 3 groups.

RESULTS

A total of 127 patients were reviewed, comprising 13 patients in group A, 31 patients in group B, and 83 patients in group C. The clinical parameters were significantly improved postoperatively in the 3 groups (P < 0.05). However, no significant differences were found among the 3 groups at the final follow-up (P > 0.05). The mean postoperative intervertebral space height (ISH) was 4.76 ± 0.45 mm, 5.23 ± 0.81 mm, and 6.26 ± 1.12 mm in the 3 groups, respectively. The postoperative ISH in group C was significantly higher than those in the other groups at the final follow-up (P < 0.001). One patient in group A and 1 patient in group B had implant subsidence, and degeneration at the inferiorly adjacent level was radiographically identified in 30.77% patients in group A, 16.13% patients in group B, and 9.64% patients in group C. However, there were only significant differences between group A and group C in subsidence (P = 0.011) and occurrence of adjacent level degeneration (P = 0.032).

CONCLUSIONS

The HU value has a large variation range among the patients with T-score ≥ -2.5. We found significantly increased rates of implant subsidence, loss of ISH, and adjacent segment degeneration in patients with lower HU value undergoing CDR. However, these radiographic complications did not predispose patients with lower HU value to worse clinical outcomes. Routine application of HU combined with dual-energy X-ray absorptiometry measurement to evaluate bone quality may help to screen the optimal candidates for CDR and reduce the implant-related complications.

Sagittal wedging of intervertebral discs and vertebral bodies in the cervical spine and their associations with age, sex and cervical lordosis: A large-scale morphological study

Many recent studies have focused on the functional and clinical importance of cervical lordosis. However, there is little accurate knowledge of the anatomical parameters that constitute cervical lordosis (i.e., the sagittal wedging angles of intervertebral discs and vertebral bodies) and their associations with age and sex. Standing lateral cervical radiographs of 1020 subjects (424 males, 596 females) with a mean age of 36.6 ± 17.0 years (range 7-95 years) were evaluated retrospectively. Cervical lordosis, the sum of intervertebral disc wedging angles from C2/C3 to C6/C7 and the sum of vertebral body wedging angles from C3 to C7 were measured. The sum of intervertebral disc wedging and the sum of vertebral body wedging were 20.6° ± 14.7° and -12.8° ± 10.3°, respectively. The sum of intervertebral disc wedging increased significantly with age and was significantly greater in males than females, whereas there was no sex-related difference in the sum of vertebral body wedging. The sum of intervertebral disc wedging was negatively correlated with sum of vertebral body wedging. Wedging of discs contributed to C2-C7 cervical lordosis more significantly than wedging of vertebral bodies. There were moderate positive correlations between cervical lordosis and intervertebral disc wedging angles at C3/C4, C4/C5 and C5/C6; weak correlations were observed at C2/C3 and C6/C7. This study constitutes the largest currently available analysis comprehensively documenting the anatomical characteristics of sagittal wedging of intervertebral discs and vertebral bodies in the cervical spine. The findings could improve understanding of the internal architecture of cervical lordosis among clinicians.

The Changes in Cervical Biomechanics After CTDR and Its Association With Heterotopic Ossification: A Systematic Review and Meta-analysis

STUDY DESIGN

A systematic review and meta-analysis.

OBJECTIVES

Cervical total disc replacement (CTDR) can preserve range of motion (ROM) of the operated spinal segment in cadaver studies. Evidence is less clear in clinical trials. The present study aims to investigate the differences in cervical biomechanics before and after CTDR and its association with heterotopic ossification (HO) development.

METHOD

Articles that reported the rate of HO and ≥1 difference in cervical biomechanics were included in quantitative analyses. We pooled the mean difference (MD) of cervical biomechanics before and after CTDR. Subgroup analyses and metaregression analyses were conducted to identify potential contributors to heterogeneity.

RESULTS

Of the 599 studies screened, 35 studies were included in the final analysis. In comparison with preoperative values, ROM of the spinal segment inferior (MD: 0.38; 95% CI: 0.02 to 0.74) and superior (MD: 0.43; 95% CI: 0.12 to 0.75) to the surgical spinal segment, functional spinal unit (FSU) angle (MD: 2.23; 95% CI: 1.11 to 3.35), and C2/C7 Cobb angle (MD: 3.49; 95% CI: 1.73 to 5.25) significantly increased after CTDR. In contrast, FSU and cervical ROM at baseline were no different from follow-up. On multivariable meta-regression analyses, HO and ROM-limiting HO were not associated with changes in cervical biomechanics. Single-level CTDR and duration of follow-up were associated with changes in cervical biomechanics.

CONCLUSION

Our study reported the pooled mean of biomechanics at baseline and final follow-up and their differences. The changes in biomechanics were not associated with the rates of HO and ROM-limiting HO.

Cervical disc arthroplasty versus anterior cervical discectomy and fusion for the treatment of single-level disc degenerative disease with preoperative reversible kyphosis

OBJECTIVE

Whether and when cervical disc arthroplasty (CDA) could be indicated for preoperative cervical spine kyphosis is unclear. The purpose of the study was to compare the clinical and radiological outcomes of single-level CDA and single-level anterior cervical discectomy and fusion (ACDF) in the patient with preoperative reversible kyphosis.

PATIENTS AND METHODS

From 2014-2018, patients who underwent single-level CDA and single-level ACDF were consecutively reviewed. The Japanese Orthopedic Association score, Neck Disability Index and VAS were used to evaluate clinical outcomes. Range of motion (ROM), C2-7 Cobb angle, functional spinal unit (FSU) angle, and heterotopic ossification (HO) were assessed.

RESULTS

Thirty-eight CDA patients (a mean follow-up of 39.8 months) and 42 ACDF patients (37.6 months) with preoperative reversible kyphosis were included. Both groups had significant improvements in clinical outcomes, without statistically significant differences. Before surgery, there was no significant difference in cervical alignment and ROM between groups. After surgery, both groups had a significant increase in C2-7 angle and FSU without significant inter-group differences. At the last follow-up, CDA group consisted of 5 cases of lordosis, 11 cases of kyphosis and 22 cases of straight spine, while the corresponding case number in ACDF group was 4, 12 and 26 (P = 0.866). The C2-7 ROM was preserved in both groups. The segmental ROM of CDA group decreased mildly from 8.3° preoperatively to 5.1° finally, whereas the segmental ROM of ACDF group decreased significantly to nearly zero. 60.5 % (23/38) patients in CDA group developed HO with 9 levels of grade Ⅲ and 3 levels of grade Ⅳ.

CONCLUSION

For the patients with single-level disc degenerative disease and preoperative reversible kyphosis, both CDA and ACDF achieved satisfactory and comparable clinical results. CDA was non-inferior to ACDF regarding the radiological outcomes of cervical alignment. Patients in CDA group had a relatively high incidence of HO formation.

Cervical sagittal alignment after Prestige LP cervical disc replacement: radiological results and clinical impacts from a single-center experience

BACKGROUND

Cervical disc replacement (CDR) has been widely used to treat one- and two-level cervical degenerative disc disease. Studies have shown the effectiveness of CDR in preserving range of motion (ROM) and delaying adjacent segment degeneration (ASD). Cervical sagittal alignment is an important factor affecting favorable clinical outcomes in cervical spine surgery. This study aimed to explore whether cervical sagittal alignment can be maintained after CDR and to identify the impact of cervical sagittal alignment on outcomes after CDR.

METHODS

This was a single-center, retrospective study. 132 patients who underwent one-level CDR were included. Cervical sagittal alignments, including cervical lordosis (CL), segmental alignment (SA), sagittal vertical axis (SVA), T1 slope (T1s), and T1s minus CL (T1s-CL), were measured. The effects of cervical sagittal alignment on the CDR outcomes were analyzed. Patients were divided into the heterotopic ossification (HO) group and ASD group to determine the potential impacts of cervical sagittal parameters.

RESULTS

The cervical sagittal alignment parameters, except for the SVA, were significantly improved after CDR and showed decreasing trends at the last follow-up. Significantly higher CL and T1s were found in patients with better ROM after CDR. SVA ≥ 20 mm increased the risk of anterior HO (odds ratio = 2.945, P = 0.007). Significantly kyphotic SA and lower T1s values were found in the ASD patients than in the non-ASD patients (P < 0.05). Patients with ASD at the inferior level showed significantly worse CL (P < 0.05).

CONCLUSION

CDR had limited function of improving cervical sagittal alignment. Poor cervical sagittal alignment after CDR was associated with HO, ASD, and less ROM.

Outcomes After Cervical Disc Arthroplasty Versus Stand-Alone Anterior Cervical Discectomy and Fusion: A Meta-Analysis

STUDY DESIGN

Systemic review and meta-analysis.

OBJECTIVES

To review and compare surgical outcomes for patients undergoing stand-alone anterior cervical discectomy and fusion (ACDF) versus cervical disc arthroplasty (CDA) for the treatment of cervical spine disease.

METHODS

A systematic search was performed on PubMed, Medline, and the Cochrane Library. Comparative trials measuring outcomes of patients undergoing CDA and stand-alone ACDF for degenerative spine disease in the last 10 years were selected for inclusion. After data extraction and quality assessment, statistical analysis was performed with R software metafor package. The random-effects model was used if there was heterogeneity between studies; otherwise, the fixed-effects model was used.

RESULTS

In total, 12 studies including 859 patients were selected for inclusion in the meta-analysis. Patients undergoing stand-alone ACDF had a statistically significant increase in postoperative segmental angles (mean difference 0.85° [95% confidence interval = 0.35° to 1.35°], P = .0008). Patients undergoing CDA had a decreased rate of developing adjacent segmental degeneration (risk ratio = 0.56 [95% confidence interval = -0.06 to 1.18], P = .0745). Neck Disability Index, Japanese Orthopedic Association score, Visual Analogue Scale of the arm and neck, as well as postoperative cervical angles were similar between the 2 treatments.

CONCLUSIONS

When compared with CDA, stand-alone ACDF offers similar clinical outcomes for patients and leads to increased postoperative segmental angles. We encourage further blinded randomized trials to compare rates of adjacent segmental degeneration and other postoperative outcomes between these 2 treatments options.

The Assessment of Paravertebral Ossification Progression After Cervical Disc Arthroplasty Based on CT Images: A Long-term Follow-up

Objective

This study focused on the assessment of paravertebral ossification (PO) after cervical disc arthroplasty (CDA) using computed tomography (CT) images.

Methods

In this retrospective study, 52 patients (from 2004 to 2010) who received CDA at a single center were included (32 males). Preoperative and follow‐up X‐ray and CT images of all patients who underwent single‐level CDA were collected. PO from the C2/3 to C7/T1 in each patient was graded based on a CT grading system. Each segment was divided into operative level, adjacent level, or non‐adjacent level. The McAfee' classification system was used to grade PO using X‐ray plain film. The range of motion (ROM) and scores of neurological symptoms (Japanese Orthopaedic Association [JOA] score and Neck Disability Index [NDI]) at both preoperative and final follow‐up time were acquired. Progression and classification of PO in each group was compared using the chi‐square test. ROM between groups were compared using independent t‐test. JOA score and NDI between groups were compared using Mann–Whitney U test.

Results

The average follow‐up time was 81.2 months. In comparison with the preoperative status, the progression of PO development in left and right areas (the Luschka joints areas) in the operative level groups was significantly more severe (area L,χ² value = 36.612, P < 0.001; area R, χ² value = 39.172, P < 0.001) than the non‐adjacent level groups. In contrast, although the prevalence of PO in all areas of the adjacent level groups was higher than that of the non‐adjacent level group in the same segments, there was no significant difference (P > 0.05) in the progression of PO development. The follow‐up high‐grade (grades III and IV) PO incidence rate using X‐ray grading system (3.85%) was significantly lower than that using CT grading system in area L (42.31%) and R (38.46%), but close to that in area A (5.77%) and P (1.92%). The final follow‐up ROM was not significantly different with preoperative ROM in patients with low‐grade PO (9.47° ± 4.12° vs. 9.76° ± 3.69°, P = 0.794). However, in patients with high‐grade PO, the final follow‐up ROM was significantly lower than preoperative ROM (5.77° ± 3.32° vs. 9.28° ± 4.15°, P < 0.001). There was no significant difference for JOA score and NDI at follow‐up between patients with high‐grade and low‐grade PO (JOA, 16.2 ± 1.1 vs. 16.8 ± 0.9, P = 0.489; NDI, 8.9 ± 6.1 vs. 8.0 ± 7.3, P = 0.317).

Conclusion

High‐grade PO was observed in the areas of the Luschka joints at the operative level after CDA, which was difficult to observe using X‐ray plain film. The PO formation at adjacent segments was not significant.

The Rate of Heterotopic Ossification Following Cervical Disc Arthroplasty: A Systematic Review and Comparison of Data

STUDY DESIGN

Systematic review.

OBJECTIVES

The purpose of the current study is to determine the overall incidence of Heterotopic Ossification (HO) following cervical disc arthroplasty (CDA) as well as per annum rates.

SUMMARY OF BACKGROUND DATA

CDA is a well-established surgical modality for treatment of one- and two-level degenerative disc disease that has failed conservative treatment. Despite its proven mid-term clinical success, the potential for accelerated HO following CDA remains an area of clinical concern.

METHODS

A MEDLINE literature search was performed using PubMed, the Cochrane Database of Systematic Reviews, and Embase from January 1980 to February 2018. We included studies involving adult patients, who underwent CDA, documentation of HO, with >12 month follow-up. The pooled results were obtained by calculating the effect size based on the logit event rate. Per annum rates were determined based on weighted averages according to average follow-up period.

RESULTS

The initial database review resulted in 230 articles, with 19 articles that met inclusion and exclusion criteria. These pooled results included 2151-disc levels and 1732 patients (50% men and 50% women) who underwent CDA and were evaluated for postoperative HO. The mean age was 45 years with a mean follow-up of 60 months. Sixteen studies reported the occurrence of severe HO resulting in 22.8% of disc levels developing severe HO. When stratifying these studies based on funding type, severe HO was reported at a rate of 21.6% by IDE studies and 27.9% by independent studies.

CONCLUSION

The findings of the pooled data show the incidence of severe HO following CDA to be 22.8%. However, there is a significant difference in reported rates of mild and severe HO between IDE and independent data. This alludes to possible underreporting of HO and severity of HO in the industry sponsored IDE studies when compared with independent studies.

LEVEL OF EVIDENCE

2.

Could self-locking stand-alone cage reduce adjacent-level ossification development after aneterior cervical discectomy and fusion?

Numerous studies have shown that cervical arthrodesis is associated with the adjacent-segment pathology (ASP), such as adjacent-level ossification development (ALOD). However, it still remains largely unclear whether the self-locking stand-alone implant system can reduce the incidence of ALOD. In the present study, we prospectively recruited 120 patients with cervical degenerative disc disease (CDDD) who were treated by anterior cervical discectomy and fusion (ACDF). These patients were randomly and evenly divided into the ROI-C group and plate group. Clinical and radiologic follow-up was performed at 3, 6, 12, 24 and 36 months after surgery. Clinical evaluation included preoperative and postoperative assessments of Japanese Orthopaedic Association (JOA) score and Neck Disability Index (NDI) score. The presence and severity of ALOD, as well as the C2-7 Cobb angle, were assessed on the lateral cervical films during follow-up. There were no significant differences in JOA and NDI scores at each time point during the follow-up period between the two groups. ALOD occurred in 8.8% of 58 patients and 6.7% of 104 levels in the cage group. Moreover, ALOD occurred in 20.1% of 57 patients and 17.8% of 101 levels in the plate group. The ALOD was more serious in the plate group compared with the cage group. The C2-7 Cobb angle was significantly improved compared with that before the operation and could be maintained during the follow-up in both groups. The self-locking stand-alone cage was efficacious for ACDF, and it could reduce the incidence of ALOD compared with anterior plate and cage.

Cervical Total Disc Replacement and Heterotopic Ossification: A Review of Literature Outcomes and Biomechanics

Anterior cervical discectomy and fusion (ACDF) immobilizes surgical segments and can lead to the development of adjacent segment degeneration and adjacent segment disease. Thus, cervical total disc replacement (CTDR) has been developed with the aim to preserve the biomechanics of spine. However, heterotopic ossification (HO), a complication following CTDR, can reduce the segmental range of motion (ROM) and defects the motion-preservation benefit of CTDR. The pathological process of HO in CTDR remains unknown. HO has been suggested to be a self-defense mechanism in response to the non-physiological biomechanics of the cervical spine following CTDR. The current literature review is concerned with the association between the biomechanical factors and HO formation and the clinical significance of HO in CTDR. Endplate coverage, disc height, segmental angle, and center of rotation may be associated with the development of HO. The longer the follow-up, the higher the rate of ROM-limiting HO. Regardless of the loss of motion-preservation benefit of CTDR in patients with HO, CTDR confers patients with a motion-preservation period before the development of ROM-limiting HO. This may delay the development of adjacent segment degeneration compared with ACDF. Future clinical studies should explore the association between HO and changes in biomechanical factors of the cervical spine.

Does preoperative inferior endplate morphology influence the outcomes of cervical disc arthroplasty at C5-C6 level: A retrospective study

OBJECTIVES

Despite encouraging clinical results, the postoperative segmental kyphosis was observed in many cervical disc arthroplasty (CDA) studies. Most studies discussed technical factors related to kyphosis. However, the cervical endplate, which contacted directly with prostheses and distributed the compressive load across the vertebral body, was seldom investigated. The purpose of the study was to investigate the effects of the inferior endplate morphology on clinical and radiological outcomes after C5/C6-level CDA with Prestige-LP Disc.

PATIENTS AND METHODS

One hundred and thirty-two patients with C5/C6-level CDA were retrospectively reviewed. Their preoperative inferior endplates on the mid-sagittal plane were visually classified into 3 types: type I with the endplate concavity apex located posteriorly, type II with the apex located in the middle and type III with the apex located anteriorly. Sagittal diameter of endplate, endplate concavity depth and endplate concavity apex location were measured. Japanese Orthopedic Association (JOA), visual analogue scale (VAS) and Neck Disability Index (NDI) scores were used to evaluate clinical outcomes. Range of motion (ROM) and sagittal alignment including C2-7 and C5-6 angle were assessed.

RESULTS

The type I, type II and type III endplates accounted for 25.00 %, 51.52 % and 23.48 % of 132 individuals. Most patients achieved significant reduction in VAS scores and NDI but the significant increase in JOA scores. No substantial differences in clinical outcomes were found among the 3 endplate types. Compared with preoperative values, the C5-6 ROM, C2-7 ROM and C2-7 angle were preserved, while the C5-6 angle increased significantly from kyphosis to lordosis. At the last follow-up, type I endplate had the least C5-6 angle (2.03°, 3.94° and 4.46° for type I, II and III endplates) and the highest incidence of segmental kyphosis at C5-C6 level (33.30 %, 14.70 % and 9.70 % in the same order, P = 0.028).

CONCLUSIONS

Patients achieved satisfactory clinical outcomes after C5/C6-level CDA without significant differences among three endplate types. Type I endplate had a high incidence of segmental kyphosis at C5-C6 level.

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.

Influence of Fusion on the Behavior of Adjacent Disc Arthroplasty in Contiguous 2-Level Hybrid Surgery In Vivo

OBJECTIVE

To investigate whether the behavior of disc arthroplasty in 2-level hybrid surgery (HS) was affected by adjacent fusion in vivo compared with cervical disc arthroplasty (CDA) alone.

METHODS

Seventy-nine patients undergoing either a 1-level CDA or contiguous 2-level HS were retrospectively reviewed. Radiologic assessments included segmental lordosis (SL), intervertebral disc height (IDH), changes in SL and IDH, range of motion (ROM) of the disc replacement and its adjacent segments, migration and subsidence of the prosthesis, heterotopic ossification (HO), and adjacent segment degeneration (ASD) adjacent to the arthroplasty level. Clinical features and outcome scores were also recorded.

RESULTS

Compared with 1-level CDA, the increased SL and IDH immediately after surgery in 2-level HS were more likely to be lost throughout the follow-up period. However, both groups generally maintained the SL and IDH of the arthroplasty segment postoperatively. Two-level HS did not exhibit hypermobility of the disc prosthesis and preserved preoperative ROM of the adjacent segment of the device. The HS group showed adverse effects on the prosthesis stability, but there was no significant difference in the number of cases of obvious migration or subsidence between the groups. The differences in HO, ASD, and clinical outcomes between the groups were not significant at the final follow-up.

CONCLUSIONS

Although the fusion in 2-level HS partially affected the behavior of adjacent disc arthroplasty compared with CDA alone, it did not cause severe complications and adverse clinical outcomes. However, large-scale and long follow-up trials are warranted.

Placement of Titanium Mesh in Hybrid Decompression Surgery to Avoid Graft Subsidence in Treatment of Three-Level Cervical Spondylotic Myelopathy: Cephalad or Caudal?

Background

Hybrid decompression has been used to treat patients with cervical spondylotic myelopathy (CSM). However, no published study has investigated the effect of titanium mesh (TM) located cephalad or caudal in hybrid decompression surgery on the graft subsidence in treatment of three-level CSM.

Material/Methods

Forty-eight cases with three-level CSM who underwent the procedure of hybrid decompression from Jan 2014 to Jan 2017 were retrospectively reviewed. Radiological outcomes immediately postoperatively and at the final follow-up were compared between cases from group A (TM located cephalad, n=21) and group B (TM located caudal, n=27).

Results

No differences were observed in the 2 groups in terms of number, sex, or duration of follow-up. The average follow-up was 4.38±0.439 months in group A and 4.81±0.509 months in group B (p>0.05). The index loss of anterior (AIBH), middle (MIBH), and posterior interbody height (PIBH) in group A were 0.857±0.448/1.00±0.525/1.33±0.608, respectively, which were all lower than that in group B (P<0.05), as was the occurrence of TM subsidence. However, there was no significance difference in height loss of adjacent intervertebral space between groups. All angles were decreased at the final follow-up in both groups (p<0.05). More decrease of C2–C7 angle occurred in group B (p>0.05), and segmental angle in group A decreased more than in group B (p>0.05).

Conclusions

TM inferior to intervertebral cage (IC) in hybrid decompression has a higher risk for developing subsidence, and when the choice of the position of TM is available in hybrid decompression surgery, TM located cephalad was recommend to alleviate TM subsidence.

Radiological Fusion Criteria of Postoperative Anterior Cervical Discectomy and Fusion: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

Diagnosis of pseudarthrosis after anterior cervical fusion is difficult, and often depends on the surgeon's subjective assessment because recommended radiographic criteria are lacking. This review evaluated the available evidence for confirming fusion after anterior cervical surgery.

METHODS

Articles describing assessment of anterior cervical fusion were retrieved from MEDLINE and SCOPUS. The assessment methods and fusion rates at 1 and 2 years were evaluated to identify reliable radiographical criteria.

RESULTS

Ten fusion criteria were described. The 4 most common were presence of bridging trabecular bone between the endplates, absence of a radiolucent gap between the graft and endplate, absence of or minimal motion between adjacent vertebral bodies on flexion-extension radiographs, and absence of or minimal motion between the spinous processes on flexion-extension radiographs. The mean fusion rates were 90.2% at 1 year and 94.7% at 2 years. The fusion rate at 2 years had significant independence (P = .048).

CONCLUSIONS

The most common fusion criteria, bridging trabecular bone between the endplates and absence of a radiolucent gap between the graft and endplate, are subjective. We recommend using <1 mm of motion between spinous processes on extension and flexion to confirm fusion.

Clinical and radiographic outcomes of cervical disc arthroplasty with Prestige-LP Disc: a minimum 6-year follow-up study

Background

Cervical disc arthroplasty (CDA) has been considered as an alternative to cervical arthrodesis in the treatment of cervical degenerative disc diseases (CDDD). The aim of this study was to assess the long-term clinical and radiographic outcomes of CDA with Prestige-LP Disc.

Methods

A total of 61 patients who underwent single- or two-level CDA with Prestige-LP Disc were retrospectively investigated at a minimum of 6-year follow-up. Clinical assessments included visual analogue scale (VAS) for neck and arm pain, Neck Disability Index (NDI), and Japanese Orthopedic Association (JOA) score. Radiological evaluations included range of motion (ROM) of the index and adjacent levels, segmental angle, cervical sagittal alignment, heterotopic ossification (HO) and adjacent segment degeneration (ASD).

Results

Significant and maintained improvement in VAS for neck and arm, NDI and JOA were observed after a mean follow-up of 82.3 months (p < 0.001). The preoperative ROM of the index level was 9.7°, which was maintained at 2-and 4-year follow-up (9.3°, p = 0.597; 9.0°, p = 0.297), but was decreased to 8.0° at final follow-up (p = 0.019). Mobility was maintained in 80.5% (62/77) of the implanted prostheses at final follow-up. ROM of the superior and inferior adjacent segments, cervical sagittal alignment and cervical angel were all maintained. The incidence of HO was 42.9% at final follow-up, but it did not influence the clinical outcome. Radiographic ASD were detected in 29.5% of the patients. However, the incidence of symptomatic ASD was only 6.6%.

Conclusion

Cervical disc arthroplasty with Prestige-LP Disc demonstrated a maintained and satisfactory clinical outcome at a minimal of 6-year follow-up, with majority of the prostheses remained mobile. Cervical disc arthroplasty with Prestige-LP Dis can be considered as an effective surgical method in treating CDDD.

Clinical and radiological outcome at 10 years of follow-up after total cervical disc replacement

PURPOSE

Previous studies have demonstrated that total cervical disc replacement (cTDR) represents a viable treatment alternative to the 'gold standard' anterior cervical discectomy and fusion for the treatment of well-defined cervical pathologies at short- and mid-term follow-up (FU). However, the implementation and acceptance of a non-fusion philosophy is closely associated with its avoidance of adjacent segment degeneration. Proof of the functional sustainability and clinical improvement of symptoms at long-term FU is still pending. The aim of this ongoing prospective study was to investigate the clinical and radiological results of cTDR at long-term FU.

METHODS

50 patients were treated surgically within a non-randomised prospective study framework with cTDR (ProDisc C™, Synthes, Paoli, PA, USA). Patients were examined preoperatively followed by routine clinical and radiological examinations at 1, 5 and 10 years after surgery, respectively. In addition to the clinical scores, conventional X-ray images of the cervical spine were taken in anteroposterior and lateral view as well as flexion/extension images. Clinical outcome scores included parameters such as the Neck Disability Index (NDI), Visual Analogue Scale (VAS), arm and neck pain self-assessment questionnaires as well as subjective patient satisfaction rates. The radiological outcome variables included the range of motion (ROM) of the implanted prosthesis between maximum flexion and extension images, the occurrence of heterotopic ossifications and radiographic signs of adjacent segment degenerative changes. The reoperation rate following cTDR was recorded as a secondary outcome variable.

RESULTS

A significant and maintained clinical improvement of all clinical outcome scores was observed after a mean FU of 10.2 years (VASarm 6.3-2.1; VASneck 6.4-1.9; NDI 21-6; p < 0.05). An increase in the incidence and the extent of heterotopic ossifications was noted during the post-operative course with a significant influence on the function of the prosthesis, which, however, did not reveal any detrimental effect on the patients' clinical symptomatology. Prosthesis mobility declined from 9.0° preoperatively and 9.1° at 1 year FU to 7.7° and 7.6° at the five- and ten-year FU examinations, respectively. Radiological signs of adjacent segment degeneration were detected in 13/38 (35.7%), however, in only 3/38 (7.9%) patients this radiological changes were associated with clinical symptoms requiring conservative treatment. Intraoperative technical failure in two cases required interbody fusion with a cage (2/50). One patient (1/48, 2.1%) treated this motion device had revision surgery at the index level.

CONCLUSION

Cervical total disc replacement with ProDisc C demonstrated a significant and maintained improvement of all clinical outcome parameters at a follow-up of ≥10 years. The present long-term data reveal that with an exceptionally low implant-related reoperation rate and low symptomatic adjacent segment degeneration rate, cTDR may be regarded as a safe and viable treatment option.

The prevalence of heterotopic ossification among patients after cervical artificial disc replacement: A systematic review and meta-analysis

BACKGROUND

Prevalence estimates of heterotopic ossification (HO) following cervical artificial disc replacement (ADR) varied widely in previous studies. We conducted a systematic review and meta-analysis to summarize its point prevalence.

METHODS

Electronic searches of PubMed, Web of Science, Embase, and Cochrane Library databases were conducted to identify studies that reported prevalence of HO. Definitions of HO and severe HO were based on McAfee grading system. Random-effects model was used to estimate the pooled prevalence. We conducted subgroup analyses according to the different length of follow-up time, and performed univariate metaregression analyses to explore the effects of potential variables on the overall prevalence.

RESULTS

A total of 38 studies were included in this study. The pooled data showed that the prevalence of HO after cervical ADR within the 1 to 2 years, 2 to 5 years, and 5 to10 years of follow-up was 38.0% (95% confidence interval [CI], 30.2%-46.5%), 52.6% (95% CI, 43.1%-61.9%), and 53.6% (95% CI, 40.0%-66.7%), respectively, while the prevalence of severe HO was 10.9% (95% CI, 9.0%-13.2%), 22.2% (95% CI, 15.5%-30.7%), and 47.5% (95% CI, 30.0%-65.8%), respectively. Follow-up time was positively associated with the prevalence of severe HO (P < .01), and the 1-month growth of mean follow-up went with 0.63% increase of severe HO.

CONCLUSION

This meta-analysis reported data on the prevalence of HO and severe HO after cervical ADR, and provided information on its process of development. These should be useful to enable surgeons and patients to gain a better understanding of HO after cervical ADR.

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.

The application of a new type of titanium mesh cage in hybrid anterior decompression and fusion technique for the treatment of continuously three-level cervical spondylotic myelopathy

PURPOSE

To evaluate the efficacy and safety of a new type of titanium mesh cage (NTMC) in hybrid anterior decompression and fusion method (HDF) in treating continuously three-level cervical spondylotic myelopathy (TCSM).

METHODS

Ninety-four cases who had TCSM and accepted the HDF from Jan 2007 to Jan 2010 were included. Clinical and radiological outcomes were compared between cases who had the NTMC (Group A, n = 45) and traditional titanium mesh cage (TTMC, Group B, n = 49) after corpectomies. Each case accepted one polyetheretherketone cage (PEEK) after discectomy.

RESULTS

Mean follow-up were 74.4 and 77.3 months in Group A and B, respectively (p > 0.05). Differences in cervical lordosis (CL), segmental lordosis (SL), anterior segmental height (ASH) and posterior segmental height (PSH) between two groups were not significant preoperatively, 3-days postoperatively or at final visit. However, losses of the CL, SL, ASH and PSH were all significantly larger in Group B at the final visit, so did incidences of segmental subsidence and severe subsidence. Difference in preoperative Japanese Orthopedic Association (JOA), visual analog scale (VAS), neck disability index (NDI) or SF-36 between two groups was not significant. At the final visit, fusion rate, JOA, and SF-36 were all comparable between two groups, but the VAS and NDI were both significantly greater in Group B.

CONCLUSIONS

For cases with TCSM, HDF with the NTMC and TTMC can provide comparable radiological and clinical improvements. But application of the NTMC in HDF is of advantages in decreasing the subsidence incidence, losses of lordosis correction, VAS and NDI.

Cervical cages placed bilaterally in the facet joints from a posterior approach significantly increase foraminal area

PURPOSE

Foraminal stenosis is a common cause of cervical radiculopathy. Posterior cervical cages can indirectly increase foraminal area and decompress the nerve root. The aim of this study was to assess the influence of bilateral posterior cervical cages on the surface area and shape of the neural foramen.

METHODS

Radiographic analysis was performed on 43 subjects enrolled in a prospective, multi-center study. CT scans were obtained at baseline and 6- and 12-months after cervical fusion using bilateral posterior cervical cages. The following measurements were performed on CT scan: foraminal area (A), theoretical area (TA), height (H), superior diagonal (DSI), inferior diagonal (DIS), and inferior diagonal without implant (DISI). Comparisons were performed using R-ANOVA with a significance of α < 0.05.

RESULTS

Foraminal area, height, TA and DISI were significantly greater following placement of the implant. The mean (SD) A increased from 4.01 (1.09) mm(2) before surgery to 4.24 (1.00) mm(2) at 6 months, and 4.18 (1.05) mm(2) at 12 months after surgery (p < 0.0001). Foraminal height (H) increased from mean (SD) 9.20 (1.08) mm at baseline to 9.65 (1.06) mm and 9.55 (1.14) mm at 6- and 12-months post-operatively, respectively (p < 0.0001). The mean DIS did not change significantly. There was a significant decrease in DSI: 6.18 (1.59) mm pre-operatively, 5.95 (1.47) mm and 5.73 (1.46) mm at 6- and 12-months (p < 0.0001).

CONCLUSIONS

Implantation of bilateral posterior cervical cages can increase foraminal area and may indirectly decompress the nerve roots. Correlation between increase in foraminal area and clinical outcomes needs further investigation.