OBJECTIVE: The long-term results of cervical disc arthroplasty (CDA) for noncontiguous cervical degenerative disc disease (CDDD) are still uncertain. Moreover, it is unclear whether CDA delays or avoids the degeneration of the intermediate segment (IS), leading to controversy in the field. Therefore, this study aimed to investigate the mid- to long-term clinical and radiographic outcomes of CDA in treating noncontiguous CDDD and to explore whether the IS degenerated faster after CDA than other non-surgically treated adjacent segments.
METHODS: We retrospectively analyzed patients with noncontiguous CDDD who underwent CDA in our department between January 2008 and July 2018. The patients were divided into the CDA and hybrid surgery (HS) groups, and clinical and radiographic outcomes were evaluated at routine postoperative intervals. Clinical outcomes were assessed using the Japanese Orthopaedic Association (JOA), neck disability index (NDI), and visual analogue scale (VAS), while radiographic outcomes included cervical lordosis (CL), C2-C7 range of motion (ROM), segmental ROM, and disc angle (DA) at the arthroplasty level. Complications were also evaluated.Pre- and postoperative values were compared using paired t-tests or Wilcoxon rank-sum tests. Independent Student t-tests or Mann-Whitney U tests analyzed continuous data between CDA and HS groups, while chi-square or Fisher exact tests assessed categorical data.
RESULTS: Sixty-four patients with noncontiguous CDDD, with 31 in the CDA group and 33 in the HS group, were evaluated. The mean follow-up time was over 70 months. The most frequently involved levels were C4/5 and C5/6. Both groups showed significant improvements in JOA, NDI, and VAS values after surgery. Although CL was maintained, the CL in the CDA group was consistently lower than that in the HS group (p < 0.05). There was a significant decrease in C2-C7 ROM (p < 0.05), but at the last follow-up, the C2-C7 ROM in the CDA group was greater than that in the HS group (p < 0.05). At the last follow-up, 44.3% of arthroplasty levels had developed heterotopic ossification (HO), and 48.45% had developed anterior bone loss (ABL). In addition, adjacent segment degeneration (ASDeg) was observed in the IS (22.7%), superior adjacent segment (20.6%)and inferior adjacent segment (21.9%).
CONCLUSIONS: CDA or CDA combined with fusion are viable treatments for noncontiguous CDDD, with satisfactory outcomes after mid-to-long-term follow-up. ASDeg is similar in non-surgical segments after 70 months of follow-up. ROM of the IS issimilar to preoperative levels, indicating CDA does not increase the risk of IS degeneration.

BACKGROUND: Posterior internal fixation (PIF) is commonly used in the treatment of thoracolumbar fracture (TLF), but there is still no standard for the number of fixed segments. The objective of this meta-analysis was to evaluate the efficacy and safety of short segment (SS), intermediate segment (IS) and long segment (LS) in the fixation of TLF.
METHODS: Two authors independently searched through PubMed, Embase, Cochrane Library and Web of Science for studies of thoracolumbar fracture treated by posterior internal fixation, which were published until the end of April 2021. The Aggregate Data Drug Information System (ADDIS) software was used for data evaluation according to the Markov chain Monte Carlo (MCMC) method based on the Bayesian theorem.
RESULTS: Nineteen trials evaluating a total of 970 patients were enrolled in these studies, of which 340 in the SS group, 429 in the IS group and 201 in the LS group. For anterior vertebral height ratio (AVHR), IS had the highest AVHR, LS had the second highest AVHR. IS also ranked first in reducing visual analogue scale (VAS), SS ranked second. For sagittal Cobb\'s angle (SCA), LS had the lowest SCA and IS had the second lowest SCA. In terms of adverse events, IS had the lowest implant failure rate and LS had the second lowest implant failure rate.
CONCLUSIONS: IS may be the most desirable treatment option for TLF in reducing SCA, implant failure rate, VAS, and improving AVHR. However, more randomized controlled trials are needed to verify these results.

Surgery for cervical degenerative disc disorder (CDDD) at two noncontiguous segments is infrequent. Few studies have explored the biomechanical effects on the intermediate adjacent segment of anterior cervical discectomy and fusion (ACDF) or cervical disc arthroplasty (CDA) in this situation. No study has examined biomechanical differences between ACDF and hybrid surgery (HS) constructs for noncontiguous CDDD. Differences in the biomechanical changes between the intermediate and adjacent segments are unknown.
This study was conducted to compare the biomechanical changes resulting from noncontiguous ACDFs and HS.
A finite element analysis study.
A finite element model of a healthy cervical spine (C2-C7) was constructed. Three surgical models were developed: (1) ACDF at C3/4 and C5/6 (FF), (2) ACDF at C3/4 and CDA at C5/6 (FA) and (3) CDA at C3/4 and ACDF at C5/6 (AF). A 75-N follower load with 1.0 N·m moments was applied to the top of the C2 vertebra in the intact model to simulate flexion, extension, lateral bending, and axial rotation. Surgical models achieved identical motion angles of the intact model in each direction following the displacement-control protocols.
The FF model required much higher moments than did the AF and FA models to achieve the same amount of motion. In the FF model, the motion contributions of the unfused segments were unevenly increased. The magnitude of the increased motion in the intermediate segment was larger than those in the supra- or infra-adjacent segments. The facet contact force (FCF) and intradiscal pressure (IDP) at the intermediate segment were also more susceptible to impact. In the FA and AF models, the motion contributions of the untreated levels were evenly changed, and the intermediate segment did not experience additive motion, FCF, or IDP. The segment adjacent to the level of ACDF had greater FCF and IDP than did the segment adjacent to the level of CDA in the two HS constructs.
HS constructs resulted in less altered biomechanics and kinematics of the untreated levels and showed no additive biomechanical effects on the intermediate segments compared with ACDF at noncontiguous levels. However, the effects were associated with the relative location of the ACDF and CDA levels.
This study provides a biomechanical rationale for the use of HS to treat patients with noncontiguous CDDD.

The application of stand-alone anchored spacer (SAAS) in anterior cervical discectomy and fusion (ACDF) has been proven to be safe and effective to treat cervical spondylosis. Skip-level ACDF with SAAS, fusing only the involved levels without anterior plates, may be the optimal treatment. The aim of the study was to compare the clinical outcomes, radiologic results of SAAS, and plate-cage construct in the treatment of 2 noncontiguous levels of cervical spondylosis.
A total of 65 patients with 2 noncontiguous levels of cervical spondylosis were included in the retrospective review of prospective collected data. The clinical and radiologic outcomes were assessed with the Japanese Orthopaedic Association score, Neck Disability Index, cervical alignment, and range of motion and disc height of intermediate segment, respectively. All the aforementioned parameters were compared before and after surgery in the respective group, which also were compared between the 2 groups. Complications also were recorded, and correlations between the surgical outcome and various factors were analyzed.
No significant differences existed in clinical results between the 2 groups (P > 0.05). In addition, no statistical significance was observed in fusion rate, cervical alignment, and range of motion and disc height of intermediate segment, dysphagia, and hoarseness (P > 0.05). Preoperative Japanese Orthopaedic Association score and high-intensity signal in T2-weighted images were important predictors for surgical outcome.
Skip-level ACDF with SAAS is a safe and effective treatment of 2 noncontiguous levels of cervical spondylosis without obvious contraindications, which can keep the IS intact, and have a low impact on the IS.

The purpose of this study was to describe the clinical features of noncontiguous cervical degenerative disc disease (cDDD), investigate the efficacy and complications of a stand-alone anchored spacer (SAAS) for patients with noncontiguous cDDD, and present radiologic analysis of the intermediate segment (IS) after skip-level fusion. Nineteen consecutive patients with noncontiguous cDDD who underwent skip-level anterior cervical discectomy and fusion (ACDF) with SAAS from January 2010 to December 2012 were enrolled in this study. Clinical outcomes were assessed preoperatively and at 24 months postoperatively using the Japanese Orthopaedic Association score, Neck Disability Index, and Visual Analog Scale. Overall cervical alignment (OCA) of the cervical spine, and the range of motion (ROM), intervertebral disc height (IDH), disc signal intensity and disc protrusion of IS were measured and compared before and after surgery. Clinical outcomes significantly improved compared to preoperative scores. The OCA was corrected and maintained at 24 months postoperatively compared with preoperative values (p<0.05). There were no significant differences in the ROM and IDH of the IS at each follow-up (p>0.05). However, decreased signal intensity on T2-weighted MRI was evidenced in three mobile IS at final follow-up (20.0%). Skip-level ACDF with SAAS may be an efficacious option for the treatment of noncontiguous cDDD.