Study design Retrospective study. Objective This study aimed to compare the fusion order between the cranial and caudal levels in two-level anterior cervical discectomy and fusion (ACDF) with a zero-profile device in the treatment of cervical spondylopathy. Summary of background data Fusion is the standard used to judge the success of ACDF. However, the fusion order in two-level ACDF remains uncertain. The mechanical environment of different levels is different, which may affect the fusion rate or fusion order. Methods From 2014 to January 2019, data of consecutive patients with two-level cervical disk degenerative disease who underwent ACDF were retrospectively reviewed. Radiological assessments were based on the range of motion of the fusion level, segment slope, and disk height, and complications were assessed. Data were analyzed using the paired t, Mann-Whitney U, χ2, Fisher exact, and rank-sum tests and logistic regression analysis. Results In total, 118 patients were ultimately enrolled for analysis in the study. The respective fusion rates of the cranial and caudal levels were 26.27% and 10.17% (p < 0.05) at 3 months, 58.47% and 42.37% (p < 0.05) at 6 months, 86.44% and 82.20% (1 0.05) at 1 year, and 92.37% and 89.83% (p > 0.05) at the last follow-up. Multivariate logistic regression analysis indicated that the preoperative segmental slope and cranial level were independent risk factors for non-fusion. The adjacent segment degeneration (ASD) and subsidence rates were comparable between the two levels. Conclusion The caudal level had a slower fusion process than the cranial level. A higher preoperative segment slope was a risk factor for fusion. However, the subsidence and ASD rate were comparable between the caudal and cranial levels in the two-level ACDF.

Study design Retrospective study Objectives To explore preoperative segmental slope as a predictor of fusion rate after single-level anterior cervical discectomy and fusion (ACDF). Methods Data of consecutive patients with single-level cervical spondylosis who underwent ACDF between 2011 and January 2019 were retrospectively reviewed. Preoperative parameters including baseline characteristics, segment slope, T1 slope, range of motion, intervertebral disk height, and bone density were evaluated. Data were analyzed using Student’s t-test, Mann–Whitney U test, χ2 test, Fisher’s exact test, multivariate logistic regression analysis, and receiver operating characteristic curve. Results In total, 253 patients were selected. The mean follow-up was 32.1 months (range 24-99 months). Male sex, body mass index, preoperative segment slope, T1 slope, operative levels, and osteoporosis or osteopenia were associated with non-fusion at an early stage after surgery. However, no statistically significant difference was observed at the last follow-up. Multivariate logistic regression analysis revealed that the preoperative segment slope was an independent predictor for non-fusion at 3, 6, and 12 months postoperatively. Osteoporosis or osteopenia was an independent predictor of non-fusion at 6 and 12 months postoperatively. The area under the curve was .874 at 3 months ( P < .001, cutoff value 10.21°), .888 at 6 months ( P < .001, cutoff value 14.56°), and .825 at 12 months ( P < .001, cutoff value 21.08°). Conclusion Preoperative segment slope can be used as a predictor of early fusion rate after single-level ACDF. We determined detailed cutoff values. This study may help surgeons take measures to promote early fusion in advance.

Background:The uncovertebral joint is a potential region for anterior cervical fusion. Currently, we are aware of no clinical trials on human uncovertebral joint fusion (UJF). The purpose of this study was to compare the time it took to achieve osseous union/fusion and the clinical efficacy of UJF to end plate space fusion (ESF)—i.e., traditional anterior cervical discectomy and fusion (ACDF)—in anterior cervical surgery.Methods:Patients with single-level cervical spondylosis were recruited from April 2021 through October 2022 and randomly divided into the UJF and ESF groups, with 40 patients in each group. Autologous iliac bone was used for bone grafting in both groups. The primary outcome was the early fusion rate at 3 months postoperatively. Secondary outcomes included the prevalence of complications and patient-reported outcome measures (PROMs), including the Japanese Orthopaedic Association (JOA) score, Neck Disability Index (NDI), and visual analog scale (VAS) scores for arm and neck pain.Results:A total of 74 patients (92.5%) with an average age of 49.8 years (range, 26 to 65 years) completed the trial and were included in the analysis. There was no significant difference between the 2 groups at baseline. The operative duration and intraoperative blood loss were also comparable between the 2 groups. The fusion rate in the UJF group was significantly higher than that in the ESF group at 3 months (66.7% compared with 13.2%, p < 0.0001) and 6 months (94.1% compared with 66.7%, p = 0.006) after the operation. No significant difference was found in the fusion rate between the 2 groups 12 months postoperatively. Overall, the PROMs significantly improved after surgery in both groups and did not differ significantly between the groups at any follow-up time point. The prevalence of complications was not significantly different between the 2 groups.Conclusions:In our study of anterior cervical fusion surgery, we found that the early fusion rate after UJF was significantly higher than that after ESF.Level of Evidence:Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

ObjectiveAlthough high fusion rates have been reported for anterior cervical decompression and fusion (ACDF) in the medium and long term, the risk of nonfusion in the early period after ACDF remains substantial. This study investigates early risk factors for cage nonfusion in patients undergoing single‐ or multi‐level ACDF.MethodsThis was a retrospective study. From August 2020 to December 2021, 107 patients with ACDF, including 197 segments, were enrolled, with a follow‐up of 3 months. Among the 197 segments, 155 were diagnosed with nonfusion (Nonfusion group), and 42 were diagnosed with fusion (Fusion group) in the early period after ACDF. We assessed the significance of the patient‐specific factors, radiographic indicators, serum factors, and clinical outcomes. The Wilcoxon rank sum test, t‐tests, analysis of variance, and stepwise multivariate logistic regression were used for statistical analysis.ResultsUnivariate analysis showed that smoking, insufficient improvement in the C2‐7 Cobb angle (p = 0.024) and the functional spinal unit Cobb angle (p = 0.022) between preoperative and postoperative stages and lower serum calcium (fusion: 2.34 ± 0.12 mmol/L; nonfusion: 2.28 ± 0.17 mmol/L, p = 0.003) β‐carboxyterminal telopeptide end of type 1 collagen (β‐CTX) (fusion: 0.51 [0.38, 0.71]; nonfusion: 0.43 [0.31, 0.57], p = 0.008), and N‐terminal fragment of osteocalcin (N‐MID‐BGP) (fusion: 18.30 [12.15, 22.60]; nonfusion: 14.45 [11.65, 18.60], p = 0.023) are risk factors for nonfusion in the early period after ACDF. Stepwise logistic regression analysis revealed that poor C2‐7 Cobb angle improvement (odds ratio [OR], 1.107 [1.019–1.204], p = 0.017) and lower serum calcium (OR, 3.700 [1.138–12.032], p = 0.030) are risk factors.ConclusionsPatients with successful fusion after ACDF had higher preoperative serum calcium and improved C2‐7 Cobb angle than nonfusion patients at 3 months. These findings suggest that serum calcium could be used to identify patients at risk of nonfusion following ACDF and that correcting the C2‐7 Cobb angle during surgery could potentially increase fusion in the early period after ACDF.

Letter to the editor concerning ''The Rate of Heterotic Ossification Following Cervical Disc Arthroplasty: A Systematic Review and Comparison of Data'' by Dowell et al W ith great interest, we have read the article by Dowell et al 1 published in Spine.The author pooled heterotic ossification rates and annum rates after cervical total disc replacement. We highly appreciate their contributions to this important topic. However, there is a point that may mislead readers, and some supplementary explanations would be of benefit.In this article, severe heterotic ossification may not be able to protect adjacent segments and may lead to degeneration. However, natural process plays an important role in the occurrence of adjacent segment degeneration (ASD). ASD is indeed a common phenomenon, but it may reflect the natural history of cervical spondylosis 2 . Matsumoto et al 3 found more than 60% of 201 asymptomatic volunteers had cervical degeneration within 10 years, and degeneration rate was comparable between surgical group and control group at C5-6. Park et al 4 found 85% of patients with ASD had degenerative changes in the adjacent segments before surgery, which indicate that preoperative degeneration contributes to the increasing risk of ASD in patients receiving anterior cervical spine surgery. Therefore, natural degeneration should not be ignored when analyzing the causes of ASD. If possible, a subgroup analysis of ASD in this article can give us more clues to reach more comprehensive and rigorous conclusions.Once again, we thank the authors for their contribution in this field and hope readers can benefit from it.