Feasibility of local bone dust as a graft material in anterior cervical discectomy and fusion

A modified measurement method for functional spinal unit ROM of cervical spine

The interspinous process motion (ISM) method can provide a more accurate assessment of postoperative subaxial cervical fusion than Cobb angle method which is used more commonly in clinical practice. However, the ISM method presents the measurement results in millimeters which cannot be directly compared with the Cobb angle measurement data. We proposed a modified measurement method for cervical functional spinal unit range of motion  (FSU ROM) and evaluate its repeatability and reliability in measuring the ROM of the surgical segment after cervical artificial disc replacement surgery. A total of 81 patients who underwent cervical artificial disc replacement surgery in our department were retrospectively reviewed. Postoperative flexion-extension dynamic cervical radiographs were used for the measurement of FSU ROM of the surgical segment. The modified measurement method (M1) and the traditional Cobb angle measurement method (M2) were used. In the comparative analysis, there was no statistically significant difference between the two measurement methods (P > 0.05). Linear correlation study showed significant correlation between the two methods (P < 0.01), with a correlation coefficient of 0.947. Bland-Altman analysis showed the average difference between the two methods was 0.13°, the most of the measured data points fell within the 95% confidence interval. The M1 method demonstrated high intra-observer reliability (ICC = 0.957) and inter-observer reliability (ICC = 0.947). The M2 method showed good intra-observer reliability (ICC = 0.889) and good inter-observer reliability (ICC = 0.874). The M1 method yielded an SEM of 0.64° and an MDC of 1.49° for FSU ROM measurement, while the M2 method resulted in an SEM of 1.14° with an MDC of 2.66°.The modified measurement method for assessing cervical FSU ROM demonstrates satisfactory repeatability and reliability, provide higher measurement precision.

Does Spinal Cord-Canal Mismatch Adversely Affect the Clinical Outcomes of Anterior Cervical Discectomy and Fusion for the Treatment of Cervical Myelopathy?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To clarify whether clinical outcomes of anterior cervical discectomy and fusion (ACDF), is affected by presence of spinal canal-cord mismatch (SCCM).

SUMMARY OF BACKGROUND DATA

SCCM is considered a factor that would moderately influence surgeons to perform posterior surgery since it could widen the spinal canal, while an anterior approach could only remove degenerative pathologies grown into the spinal canal.

MATERIALS AND METHODS

We retrospectively reviewed 186 patients who underwent ACDF and had been followed-up for more than two years. Patients with spinal cord occupation ratio (SCOR) of ≥0.7 were classified into the SCCM group, while those with a SCOR of <0.7 were included in the no-SCCM group. Patient demographics, cervical sagittal parameters, neck pain visual analog scale (VAS), arm pain VAS, and Japanese Orthopedic Association (JOA) score were assessed. JOA score was the primary outcome of the study.

RESULTS

One hundred and forty-seven patients (79.0%) were included into the no-SCCM group, while 39 patients (21.0%) were classified into the SCCM group. Postoperative radiographic parameters including C2-C7 lordosis, C2-C7 sagittal vertical axis, and range of motion did not significantly differ between the two groups. Neck pain VAS, arm pain VAS, and JOA score (no-SCCM group, from 13.7±2.5 to 14.6±2.3, P <0.001; SCCM group, from 13.8±1.6 to 15.0±2.0, P <0.001) significantly improved after the operation in both groups, and results were not significantly different between the two groups. Furthermore, SCOR was not significantly associated with JOA recovery rate at two years postoperatively in linear regression analysis.

CONCLUSION

Clinical and radiographic outcomes of ACDF were not affected by the presence of SCCM. Furthermore, SCOR was not significantly associated with neurological recovery at two years of follow-up. Therefore, ACDF can be safely and effectively applied for treating cervical myelopathy, regardless of the presence of SCCM, when other factors favor the anterior approach.

LEVEL OF EVIDENCE

Level III.

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

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

Which Radiographic Parameter Can Aid in Deciding Optimal Allograft Height for Anterior Cervical Discectomy and Fusion?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To identify preoperative radiographic parameters that can guide optimal allograft height selection for anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Allograft height selection for ACDF depends on intraoperative assessment supported by trials; however, there is currently no radiographic reference parameter that could aid in allograft height selection for improved outcomes.

METHODS

A total of 148 patients who underwent ACDF using allografts and were followed up for more than 1 year were retrospectively reviewed. Fusion rates, subsidence, segmental lordosis, and foraminal height were assessed. Segments were divided into 2 groups according to whether the inserted allograft height was within 1 mm from the following 3 reference radiographic parameters: (1) uncinate process height, (2) adjacent disc height, and (3) preoperative disc height +2 mm.

RESULTS

This study included 101 patients with 163 segments. Segments with an allograft-uncinate height difference of ≤1 mm had a significantly higher fusion rate at 1-year follow-up compared with segments with allograft-uncinate height difference of >1 mm [85/107 (79.4%) vs. 35/56 (62.5%); P =0.025]. Subsidence, segmental lordosis, and foraminal height did not significantly differ between the groups when segments were divided according to uncinate height. Multivariate logistic regression analysis demonstrated that allograft-uncinate height difference of ≤1 mm and allograft failure were factors associated with fusion.

CONCLUSIONS

The uncinate process height can guide optimal allograft height selection for ACDF. Using an allograft with an allograft-uncinate height difference of ≤1 mm resulted in a higher fusion rate. Therefore, the uncinate process height should be checked preoperatively and used in conjunction with intraoperative assessment when selecting allograft height.

Efficacy and safety of oblique posterior endplate resection for wider decompression (trumpet-shaped decompression) during anterior cervical discectomy and fusion

OBJECTIVE

Anterior cervical discectomy and fusion (ACDF) provides a limited workspace, and surgeons often need to access the posterior aspect of the vertebral body to achieve sufficient decompression. Oblique resection of the posterior endplate (trumpet-shaped decompression [TSD]) widens the workspace, enabling removal of lesions behind the vertebral body. This study was conducted to evaluate the efficacy and safety of oblique posterior endplate resection for wider decompression.

METHODS

In this retrospective study, 227 patients who underwent ACDF for the treatment of cervical myelopathy or radiculopathy caused by spondylosis or ossification of the posterior longitudinal ligament and were followed up for ≥ 1 year were included. Patient characteristics, fusion rates, subsidence, and patient-reported outcome measures, including the neck pain visual analog scale (VAS) score, arm pain VAS score, and Neck Disability Index (NDI), were assessed. Patients who underwent TSD during ACDF (TSD group) and those who underwent surgery without TSD (non-TSD group) were compared.

RESULTS

Fifty-seven patients (25.1%) were included in the TSD group and 170 patients (74.9%) in the non-TSD group. In the TSD group, 28.2% ± 5.5% of the endplate was resected, and 26.0% ± 6.1% of the region behind the vertebral body could be visualized via the TSD technique. The resection angle was 26.9° ± 5.9°. The fusion rate assessed on the basis of interspinous motion, intragraft bone bridging, and extragraft bone bridging did not significantly differ between the two groups. Furthermore, there were no significant intergroup differences in subsidence. The patient-reported outcome measures at the 1-year follow-up were also not significantly different between the groups.

CONCLUSIONS

TSD widened the workspace during ACDF, and 26% of the region posterior to the vertebral body could be accessed using this technique. The construct stability was not adversely affected by TSD as demonstrated by the similar fusion and subsidence rates among patients who underwent TSD and those who did not. Therefore, TSD can be safely applied during ACDF when compressive lesions extend behind the vertebral body and are not limited to the disc space, enabling adequate decompression without disrupting the construct stability.

Using a mixture of local bone dust and morselized bone as graft materials in single- and double-level ACDF

Background

Using a cage filled with local bone in anterior cervical discectomy and fusion (ACDF) can eliminate morbidities associated with autograft harvest from the iliac crest while achieving high fusion rates. However, there is still no consensus regarding the methods for using local bone grafts. This retrospective study was performed to compare the clinical and radiological outcomes of using a mixture of bone dust and morselized bone versus morselized bone alone in ACDF.

Methods

A retrospective study of 228 patients affected by cervical degenerative disease who had undergone single- or double-level ACDF between January 2014 and June 2018 was performed. Nanohydroxyapatite/polyamide-66 (n-HA/PA66) combined with morselized bone was used in 111 patients (group A: single-level ACDF in 51 patients and double-level ACDF in 60 patients), whereas the n-HA/PA66 cage combined with a mixture of bone dust and morselized bone was used in 117 patients (group B: single-level ACDF in 58 patients and double-level ACDF in 59 patients). The fusion rate, extent of cage subsidence, fusion segmental height (FSH), C2-7 lordosis, segmental sagittal alignment (SSA), 10-point visual analog scale (VAS) score, and Neck Disability Index (NDI) were compared between the two groups.

Results

The VAS score and NDI were significantly reduced after the operation in group A and group B. At the final follow-up, the fusion rate was 90.2 % (46/51) and 94.8 % (55/58) in patients treated with single-level ACDF in group A and group B, respectively (p > 0.05). In patients treated with double-level ACDF, bone fusion was achieved in 52 patients (86.7 %) in group A and 55 patients (93.2 %) in group B (p > 0.05). The fusion rate of single- and double-level ACDF was higher in patients in group B than those in group A at the 3-month, 6-month and 12-month follow-ups (p < 0.05). The extent of cage subsidence after single- and double-level ACDF was lower in patients in group B (1.5 ± 0.5 mm and 2.3 ± 0.8 mm, respectively) than in those in group A (1.8 ± 0.7 mm and 2.9 ± 1.4 mm, respectively) (p < 0.05). There was no significant difference between the two groups in the C2-7 lordosis, FSH, SSA, VAS score, or NDI before or after the operation (p > 0.05).

Conclusions

Using a mixture of local bone dust and morselized bone as cage-filling materials yielded comparably good clinical outcomes as using morselized bone alone in single- and double-level ACDF. However, the mixture graft of bone dust and morselized bone was more beneficial in promoting early fusion and reducing cage subsidence.

Comparison between selective caudal fixed screw construct and all variable screw construct in anterior cervical discectomy and fusion

This retrospective comparative study aimed to compare the efficacy of selective caudal fixed screw constructs with all variable screw constructs in anterior cervical discectomy and fusion (ACDF). Thirty-five patients who underwent surgery using selective caudal fixed screw construct (SF group) were compared with 44 patients who underwent surgery using all variable constructs (AV group). The fusion rate, subsidence, adjacent level ossification development (ALOD), adjacent segmental disease (ASD), and plate-adjacent disc space distance were assessed. The one-year fusion rates assessed by computed tomography bone bridging and interspinous motion as well as the significant subsidence rate did not differ significantly between the AV and SF groups. The ALOD and ASD rates and plate-adjacent disc space distances did not significantly differ between the two groups at both the cranial and caudal adjacent levels. The number of operated levels was significantly associated with pseudarthrosis in the logistic regression analysis. The stability provided by the locking mechanism of the fixed screw did not lead to an increased fusion rate at the caudal level. Therefore, the screw type should be selected based on individual patient’s anatomy and surgeon’s experience without concern for increased complications caused by screw type.