A prospective,randomised, controlled multicentre study comparing cervical disc replacement with anterior cervical decompression and fusion

Purpose

Total cervical artificial disc replacement (TDR) simulates normal disc structure, thus avoiding the drawbacks of anterior cervical decompression and fusion (ACDF). This prospective, randomized, controlled and multicentre study aimed to evaluate clinical and radiographic outcomes by comparing cervical disc replacement using Mobi-C disc prostheses with ACDF.

Methods

This prospective, randomized, controlled and multicentre study consisted of 111 patients undergoing single-level Mobi-C disc prosthesis replacement (TDR group, n?=?55) or ACDF (n?=?56) from February 2008 to November 2009 at 11 medical centres across China. Patients were assessed before surgery, at seven days postoperation and one, three, six, 12, 24, 36 and 48 months postoperation. Clinical and neurological outcome was determined by measuring the Japanese Orthopaedic Association (JOA) scores, visual analogue scale (VAS) and Neck Disability Index (NDI). Static and dynamic radiographs were obtained of the cervical curvature, the functional spinal unit (FSU) angle and range of motion (ROM) of the cervical spine, FSU angle and treated and adjacent segments.

Results

A total of 111 patients were included and randomly assigned to either Mobi-C disc prosthesis replacement or ACDF. JOA, VAS and NDI showed statistically significant improvements 48 months after surgery (P?p?>?0.05). ROM in the ACDF group was significantly reduced at one month and remained so throughout the follow-up. By 48-months, more ACDF patients required secondary surgery (four of 56 patients).

Conclusions

Although ACDF may increase the risk of additional surgery, clinical outcomes indicated that both Mobi-C artificial cervical disc replacement and ACDF were reliable. Radiographic data showed that ROM of the cervical spine, FSU angle and treated and adjacent segments were relatively better reconstructed and maintained in the Mobi-C group compared with those in the ACDF group.     

Cervical arthroplasty with Discover prosthesis: clinical outcomes and analysis of factors that may influence postoperative range of motion

Purpose

The aim of this current study was to analyze the clinical outcomes after Discover cervical disc replacement and its effects on maintaining cervical lordosis and range of motion (ROM). The possible factors influencing postoperative ROM were analyzed.

Method

27 men and 28 women with a mean age of 46.4 ± 8.7 years were prospectively followed up for 2 years. Clinical outcomes were assessed using Japanese Orthopedic Association (JOA), Neck Disability Index (NDI), visual analog scale (VAS) and Odom’s criteria. Radiographic information including segment and overall alignment, functional spinal unit (FSU) and overall ROM, and disc heights were prospectively collected during the follow-up. The correlations between the postoperative FSU ROM at last follow-up and influencing factors were analyzed.

Results

Mean NDI, JOA and VAS scores showed statistical improvements at last follow-up. Anterior migration of the prosthesis was detected in six cases. Heterotopic ossification was observed in ten patients. Mean FSU angle, endplate angle of the treated level and mean overall cervical alignment were all improved significantly at last follow-up (P < 0.001). However, mean FSU ROM of the treated segment significantly decreased postoperatively (P = 0.008), while mean overall ROM showed no significant differences. A significant correlation was found between preoperative FSU ROM and postoperative FSU ROM by the Pearson correlation coefficient (r = 0.325, P = 0.034). Multiple linear regression analysis confirmed that preoperative FSU ROM contributed independently to a model with a coefficient of determination of 0.37 (P = 0.034).

Conclusions

In the 2 years follow-up, the Discover cervical disc arthroplasty has provided satisfactory clinical outcomes. It was able to substantially restore segment and overall cervical alignment while partially maintaining segment and overall cervical ROM. Additionally, we found that postoperative FSU ROM positively correlated with preoperative FSU ROM.     

Clinical and radiological results of total disc replacement in the cervical spine with preoperative reducible kyphosis

Purpose

To investigate the clinical and radiological results of total disc replacement (TDR) in the cervical spine with preoperative reducible kyphosis, and discuss when TDR is indicated for the patients with preoperative kyphosis.

Methods

Fifty-two patients who underwent single-level cervical TDR from June 2008 to May 2010 were included in this study. TDR was indicated for patients with preoperative lordosis or reducible kyphosis, and the patients were divided into a lordotic group (preoperative global angle of ≥0°) and kyphotic group (preoperative global angle of <0°). Clinical results were evaluated using the Japanese Orthopaedic Association (JOA) score, visual analog scale (VAS) score and Neck Disablity Index (NDI). For radiological evaluation, the global and functional spinal unit (FSU) angles and the global and FSU range of motion were measured preoperatively and postoperatively.

Results

The mean NDI in the kyphotic group was significantly higher than that in the lordotic group preoperatively and at six months postoperatively, but the groups showed no significant differences in JOA score, VAS score and NDI at the two year follow-up. The mean global and FSU angles in the kyphotic group were significantly lower than those in the lordotic group preoperatively and at six months postoperatively, but they gradually improved postoperatively. The differences lost significance at the two year follow-up.

Conclusions

Postoperative cervical kyphosis had adverse effects on the NDI after TDR. Artificial discs, symptom relief, and neck functional exercises may contribute to correction of preoperative reducible kyphosis at different stages after cervical TDR. Preoperative reducible kyphosis should not be an independent contraindication for cervical TDR.     

Clinical and radiological follow-up of single-level Prestige LP cervical disc replacement

Objective

To evaluate the clinical outcomes and radiographic results of patients who underwent single-level cervical arthroplasty using the Prestige LP.

Method

Thirty-one patients with single-level cervical disc disease received the Prestige LP disc replacement from June 2008 to December 2009. The neck disability index (NDI), Japanese Orthopedic Association score (JOA) and visual analogue scale (VAS) were used to assessed clinical outcomes pre-operatively and post-operatively at 24 months. The overall cervical alignment (C2–7 Cobb angle), the functional segmental unit (FSU) curvature, the range of motion (ROM) of treated and adjacent levels were measured, and the evidence of heterotopic ossification (HO) was observed from static and dynamic radiographs.

Results

There was a statistically significant improvement in the NDI from 20.2 ± 7.5 to 6.4 ± 3.5 (P < 0.000), JOA from 12.8 ± 2.2 to 16.6 ± 0.6 (P < 0.000), the neck VAS score from 4.1 ± 2.5 to 1.4 ± 1.1 (P < 0.000), the arm VAS score from 4.6 ± 2.5 to 0.7 ± 1.1 (P < 0.000). The post-operative overall cervical alignment (9.3° ± 7.2°), ROM of treated level (7.6°) and adjacent level (upper level 9.4° ± 3.1°, lower level 9.1° ± 3.5°) are well maintained. The FSU were 0.2° ± 5.4° and 1.9° ± 5.5° at pre-operation and final follow-up with statistical significance (P = 0.011). Heterotopic ossification was evidenced in five operated segment (16 %).

Conclusions

The Prestige LP disc arthroplasty maintains favorable clinical outcomes, preserves the overall cervical alignment, FSU curvature, ROM of treated level and adjacent levels.     

颈椎动态稳定器治疗颈椎病的短期疗效观察

目的：探讨颈椎动态稳定器（dynamic cervical implant, DCI）植入术治疗因颈椎间盘病变引起的颈椎病的安全性及有效性。方法回顾性分析2012年2月至2014年12月于我院行颈椎DCI植入术的23例患者（男15例,女8例）的临床资料和早期随访情况。应用疼痛视觉模拟量表（visual analogue scale, VAS）评分、日本骨科协会（Japanese Orthopaedic Association, JOA）17分评分法、颈椎功能障碍指数（neck disability index, NDI）评分和术后Odom评级评价患者的临床症状缓解情况。影像学检查测量各时间点手术节段椎间隙高度（disc height,DH）、手术节段的活动度（range of motion, ROM）、手术节段脊柱功能单位（functional spinal unit, FSU）的角度（Cobb’s角）和颈椎整体角度（C2~7 Cobb’s角）。结果 DCI手术时间,单节段为（70.55±13.43）min,双节段为（153.45±12.66）min;术中失血量,单节段为（109.20±16.22） ml,双节段为（166.75±15.30）ml。患者术后及各随访时间段JOA评分较术前均显著增加;术后及各随访时间段NDI评分、VAS评分与术前相比均显著降低。DCI植入节段的ROM、DH和FSU Cobb’s角术后随访时与术前比较均显著增加。以上差异均具有统计学意义（均P＜0.05）。C2~7 Cobb’s角随访时与术前相比稍有增加,但差异无统计学意义（P＞0.05）。结论 DCI植入术治疗颈椎病既保留了手术节段的活动度,又降低了异位骨化率,并且DCI假体可以遏制因过度运动造成的小关节退变加速。患者症状缓解明显,短期临床疗效令人满意。其中远期疗效亟待进一步的研究。     

Clinical and radiographic reports following cervical arthroplasty: a 24-month follow-up

We reviewed patients with cervical disc prosthesis replacement for single-level cervical disc disease to evaluate its clinical effect and maintenance of cervical spine motion. Fifteen patients underwent Bryan artificial cervical disc replacement and were followed-up for at least 24 months. No neurological or vascular complications were observed during or after operation. JOA, VAS, and NDI scores showed statistical significant improvement in our follow-up. The procedure achieved an 87% (13/15) satisfactory rate at 24-month evaluations according to Odom's criteria. The range of motion (ROM) of the cervical spine, treated segment, adjacent segment, and functional spinal unit (FSU) decreased at early follow-up, but they recovered to the preoperative level at 12- and 24-month follow-up. Also, preoperative lordosis of the cervical spine and FSU were not only maintained but also even improved during the 24-month follow-up. No obvious degeneration of adjacent discs were found at MRI. There were no cases of prosthesis subsidence or extrusion. The cervical disc prosthesis showed a good clinical outcome; it also restored ROM of the cervical spine and reestablished cervical curvature in our 24-month follow-up. But to be sure of its long term effect, a longer follow-up is needed.     

Biomechanical effects of cervical arthroplasty with U-shaped disc implant on segmental range of motion and loading of surrounding soft tissue

Purpose

Various design concepts have been adopted in cervical disc prostheses, including sliding articulation and standalone configuration. This study aimed to evaluate the biomechanical effects of the standalone U-shaped configuration on the cervical spine.

Methods

Based on an intact finite element model of C3–C7, a standalone U-shaped implant (DCI) was installed at C5–C6 and compared with a sliding articulation design (Prodisc-C) and an anterior fusion system. The range of motion (ROM), adjacent intradiscal pressure (IDP) and capsular ligament strain were calculated under different spinal motions.

Results

Compared to the intact configuration, the ROM at C5–C6 was reduced by 90 % after fusion, but increased by 70 % in the Prodisc-C model, while the maximum percentage change in the DCI model was 30 % decrease. At the adjacent segments, up to 32 % increase in ROM happened after fusion, while up to 34 % decrease occurred in Prodisc-C model and 17 % decrease in DCI model. The IDP increased by 11.6 % after fusion, but decreased by 5.6 and 6.3 % in the DCI and Prodisc-C model, respectively. The capsular ligament strain increased by 147 % in Prodisc-C and by 13 % in the DCI model. The DCI implant exhibited a high stress distribution.

Conclusions

Spinal fusion resulted in compensatory increase of ROM at the adjacent sites, thereby elevating the IDP. Prodisc-C resulted in hyper-mobility at the operative site that led to an increase of ligament force and strain. The U-shaped implant could maintain the spinal kinematics and impose minimum influence on the adjacent soft tissues, despite the standalone configuration encountering the disadvantages of high stress distribution.     

单节段Prestige LP人工颈椎椎间盘置换术在骨量减少颈椎病患者中的应用

目的 探讨骨量减少的颈椎病患者行单节段Prestige LP人工颈椎椎间盘置换术的安全性和有效性.方法 回顾性分析2012年2月—2017年6月本院采用Prestige LP人工颈椎椎间盘单节段置换术治疗的22例骨量减少的颈椎病患者临床资料.在术前,术后3 d、3个月、6个月、12个月及末次随访时采用日本骨科学会(JOA)评分评价患者神经功能,采用疼痛视觉模拟量表(VAS)评分及颈椎功能障碍指数(NDI)评估患者颈肩部疼痛及颈椎功能情况.在术前,术后3 d、3个月、6个月、12个月及末次随访时测量患者颈椎整体曲度、颈椎整体活动度(C2～7 ROM)、置换节段椎间角度、置换节段ROM(rROM)、置换节段椎间隙高度、置换节段脊柱功能单位(FSU)高度、邻近节段ROM(aROM)及邻近节段椎间隙高度等.观察并记录假体下沉、移位情况.结果 所有手术顺利完成.所有患者随访26～78个月,平均38.2个月.末次随访时所有患者JOA评分、VAS评分及NDI均较术前显著改善,差异有统计学意义(P<0.05).末次随访时置换节段椎间隙高度及FSU高度与术前相比显著增加,差异均有统计学意义(P<0.05).末次随访时颈椎整体曲度、C2～7 ROM、置换节段椎间角度、rROM、aROM及邻近节段椎间隙高度等与术前相比,差异均无统计学意义(P>0.05).至末次随访时,发生假体下沉3例,移位2例.结论 采用单节段Prestige LP人工颈椎椎间盘置换术治疗骨量减少的颈椎病患者安全有效,可维持满意的椎间隙高度和ROM,但需警惕假体下沉和移位等并发症.     

Reduction in range of cervical motion on serial long-term follow-up in patients undergoing oblique corpectomy for cervical spondylotic myelopathy

Purpose

To determine whether motion preservation following oblique cervical corpectomy (OCC) for cervical spondylotic myelopathy (CSM) persists with serial follow-up.

Methods

We included 28 patients with preoperative and at least two serial follow-up neutral and dynamic cervical spine radiographs who underwent OCC for CSM. Patients with an ossified posterior longitudinal ligament (OPLL) were excluded. Changes in sagittal curvature, segmental and whole spine range of motion (ROM) were measured. Nathan’s system graded anterior osteophyte formation. Neurological function was measured by Nurick’s grade and modified Japanese Orthopedic Association (JOA) scores.

Results

The majority (23 patients) had a single or 2-level corpectomy. The average duration of follow-up was 45 months. The Nurick’s grade and the JOA scores showed statistically significant improvements after surgery (p < 0.001). 17 % of patients with preoperative lordotic spines had a loss of lordosis at last follow-up, but with no clinical worsening. 77 % of the whole spine ROM and 62 % of segmental ROM was preserved at last follow-up. The whole spine and segmental ROM decreased by 11.2° and 10.9°, respectively (p ≤ 0.001). Patients with a greater range of segmental movement preoperatively had a statistically greater range of movement at follow-up. The analysis of serial radiographs indicated that the range of movement of the whole spine and the range of movement at the segmental spine levels significantly reduced during the follow-up period. Nathan’s grade showed increase in osteophytosis in more than two-thirds of the patients (p ≤ 0.01). The whole spine range of movement at follow-up significantly correlated with Nathan’s grade.

Conclusions

Although the OCC preserves segmental and whole spine ROM, serial measurements show a progressive decrease in ROM albeit without clinical worsening. The reduction in this ROM is probably related to degenerative ossification of spinal ligaments.     

Analysis of factors that may influence range of motion after cervical disc arthroplasty

Background contextCervical artificial disc replacement is increasingly becoming popular among spine surgeons. Cervical disc arthroplasty aims to afford spinal stability and then balance this with flexibility. One of the fundamental benefits from performing cervical arthroplasty instead of fusion is preservation of motion in both the functional spinal unit (FSU) and the overall cervical spine. Eventually, preservation of segmental motion is believed to prevent the development of adjacent segment degeneration. But to justify its use, disc replacement prosthesis must demonstrate actual motion in vivo and preserve range of motion (ROM) after surgery as long as it allows. Without preservation of motion, disc prosthesis becomes just a functional arthrodesis equivalent.PurposeThe purpose of this study was to analyze the possible factors affecting cervical spine ROM after single-level cervical disc arthroplasty.Study design/settingThis is a retrospective radiological study of patients with symptomatic single-level cervical disc disorder who received the cervical disc prosthesis (Bryan Cervical Disc Prosthesis; Medtronic Sofamor Danek, Memphis, TN, USA).Patient sampleProcedure was performed in 39 patients.Outcome measuresThe outcome measures were statistical correlation of possible factors and ROM.MethodsWe investigated possible factors that could affect cervical ROM after surgical intervention using cervical disc replacement. For this, we focused on two main components, namely, patient factors and technical factors. First, we examined patient factors, such as age, sex, preoperative FSU ROM, and preoperative overall cervical spine (whole cervical spine) ROM. Second, we then investigated technical factors, such as the amount of bone resection, disc insertion angle, and disc insertion depth. Then, our study searched if there was any statistical correlation between these factors and the postoperative cervical ROM.ResultsSignificant correlation was found between the postoperative overall cervical spine ROM and preoperative overall cervical spine ROM (p<.0001, R²=0.9062). Postoperative FSU ROM is closely correlated to both the preoperative FSU ROM (p<.0001) and the disc insertion angle (p=.0097). However, no significant correlation was noted between age, sex, disc insertion angle, and disc insertion depth.ConclusionSignificant correlation was found between the postoperative overall cervical spine ROM and preoperative overall cervical spine ROM. Postoperative FSU ROM is closely correlated to both the preoperative FSU ROM and the disc insertion angle. Careful preoperative evaluation of the patient's radiographs and meticulous surgical technique during the surgical procedure could aid in achieving the goals and benefits of cervical disc arthroplasty.     

Effects of a cervical disc prosthesis on maintaining sagittal alignment of the functional spinal unit and overall sagittal balance of the cervical spine

The object of this study is to review the early clinical results and radiographic outcomes following insertion of the Bryan Cervical Disc Prosthesis (Medtronic Sofamor Danek, Memphis, TN), together with its effect on maintaining sagittal alignment of the functional spinal unit (FSU) and overall sagittal balance of the cervical spine for the treatment of single-level or two-level symptomatic disc disease. Forty-seven patients with symptomatic single or two-level cervical disc disease who received the Bryan Cervical Artificial Disc were reviewed prospectively. A total of 55 Bryan disc were placed in 47 patients. A single-level procedure was performed in 39 patients and a two-level procedure in the other eight. Radiographic and clinical assessments were made preoperatively and at 1.5, 3, 6, 9, 12, and 18 and up to 33 months postoperatively. Mean follow-up duration was 24 months, ranging from 13 to 33 months. Periods were categorized as early follow up (1.5–3 months) and late follow up (6–33 months). The visual analogue scale (VAS), neck disability index(NDI), Odom’s criteria were used to assess pain and clinical outcomes. Static and dynamic radiographs were measured by hand and computer to determine the range of motion (ROM), the angle of the functional segmental unit (FSU), and the overall cervical alignment (C2–7 Cobb angle). With all of these data, we evaluated the change of the preoperative lordosis (or kyphosis) of the FSU and Overall sagittal balance of the cervical spine during the follow-up period. There was a statistically significant improvement in the VAS score from 7.0 ± 2.6 to 2.0 ± 1.5 (paired-t test, P = 0.000), and in the NDI from 21.5 ± 5.5 to 4.5 ± 3.9 (paired-t test P = 0.000). All of the patients were satisfied with the surgical results by Odom’s criteria. The postoperative ROM of the implanted level was preserved without significant difference from preoperative ROM of the operated level. Only 36% of patients with a preoperative lordotic sagittal orientation of the FSU were able to maintain lordosis following surgery. However, the overall sagittal alignment of the cervical spine was preserved in 86% of cases at the final follow up. Interestingly, preoperatively kyphotic FSU resulted in lordotic FSU in 13% of patients during the late follow-up, and preoperatively kyphotic overall cervical alignment resulted in lordosis in 33% of the patients postoperatively. Clinical results are encouraging, with significant improvement seen in the Bryan Cervical Artificial disc. The Bryan disc preserves motion of the FSU. Although the preoperative lordosis (or kyphosis) of the FSU could not always be maintained during the follow-up period, the overall sagittal balance of the cervical spine was usually preserved.     

Evaluation of a new type of titanium mesh cage versus the traditional titanium mesh cage for single-level, anterior cervical corpectomy and fusion

Study design

A retrospective review of prospectively collected data in an academic institution.

Objective

To evaluate the safety and efficacy of a new type of titanium mesh cage (TMC) in single-level, anterior cervical corpectomy and fusion (ACCF).

Methods

Fifty-eight patients consecutive with cervical spondylotic myelopathy (CSM) from cervical degenerative spondylosis and isolated ossification of the posterior longitudinal ligament were treated with a single-level ACCF using either a new type of TMC (28 patients, group A) or the traditional TMC (30 patients, group B). We evaluated the patients for TMC subsidence, cervical lordosis (C2–C7 Cobb and Cobb of fused segments) and fusion status for a minimum of 30 months postoperatively based on spine radiographs. In addition, neurologic outcomes were evaluated using the Japanese Orthopedic Association (JOA) scores. Neck pain was evaluated using a 10-point visual analog scale (VAS).

Results

The loss of height of the fused segments was less for group A than for group B (0.8 ± 0.3 vs. 2.8 ± 0.4 mm) (p < 0.01); also, there was a lower rate of severe subsidence (≥3 mm) in group A (4 %, 1/28) than in group B (17 %, 5/30) (p < 0.01). There were no differences in the C2–C7 Cobb and Cobb of fused segments between the groups preoperatively or at final follow-up (p > 0.05), but the Cobb of fused segments immediately postoperative were significantly less for group B than for group A (p < 0.01). All patients, however, had successful fusion (100 %, each). Both groups had marked improvement in the JOA score after operation (p < 0.01), with no significant differences in the JOA recovery ratio (p > 0.05). The postoperative VAS neck pain scores for group A were significantly less than that for group B (p < 0.05); severe subsidence was correlated with neck pain.

Conclusions

The new type of TMC provides comparable clinical results and fusion rates with the traditional TMC for patients undergoing single-level corpectomy. The new design TMC decreases postoperative subsidence (compared to the traditional TMC); the unique design of the new type of TMC matches the vertebral endplate morphology which appears to decrease the severity of subsidence-related neck pain in follow-up.     

Clinical and radiographic results of Bryan cervical total disc replacement: 4-year outcomes in a prospective study

Introduction

Early results have indicated that the Bryan cervical total disc replacement (TDR) favorably compares to anterior cervical decompression and fusion, while it is associated with fewer complications and higher levels of satisfaction. In this study, we sought to prospectively report the midterm outcomes of the Bryan TDR.

Patients and methods

A total of 20 patients had performed their 4-year follow-up visit and had been assessed clinically and radiologically. Clinical outcomes (JOA, VAS, NDI, SF-36) and ROM measurements were investigated preoperatively and at 1 and 6 months, and 1, 2 and 4 years after operation. Complications were also investigated. Occurrences of heterotopic ossifications (HOs) and adjacent-level degeneration (ALD) radiographic changes were detected from 4-year follow-up X-rays.

Results

The mean JOA score, VAS score for arm and neck, NDI score and SF-36 score for PCS and MCS were reduced significantly at each postoperative time point when compared with the preoperative condition. The range of movement of the cervical spine, functional spinal unit, treated segment and the adjacent segment temporarily decreased at the early assessment, but all recovered to preoperative levels over a 6-month to 4-year time period. HO was evident in 6 of the 23 operated segments, which did not restrict the movement of the prosthesis. No obvious ALD was found on MRI. There were no cases of prosthesis migration, subsidence, loosening or wear.

Conclusion

The midterm outcomes demonstrated that the Bryan TDR maintains favorable clinical and radiological results, with preservation of movement and satisfactory clinical outcome. There were no serious complications or cases of prosthetic wear or failure. The long-term benefits are yet to be examined.     

Design and preliminary biomechanical analysis of artificial cervical joint complex

Objective

To design an artificial cervical joint complex (ACJC) prosthesis for non-fusion reconstruction after cervical subtotal corpectomy, and to evaluate the biomechanical stability, preservation of segment movements and influence on adjacent inter-vertebral movements of this prosthesis.

Methods

The prosthesis was composed of three parts: the upper/lower joint head and the middle artificial vertebrae made of Cobalt–Chromium–Molybdenum (Co–Cr–Mo) alloy and polyethylene with a ball-and-socket joint design resembling the multi-axial movement in normal inter-vertebral spaces. Biomechanical tests of intact spine (control), Orion locking plate system and ACJC prosthesis were performed on formalin-fixed cervical spine specimens from 21 healthy cadavers to compare stability, range of motion (ROM) of the surgical segment and ROM of adjacent inter-vertebral spaces.

Results

As for stability of the whole lower cervical spine, there was no significant difference of flexion, extension, lateral bending and torsion between intact spine group and ACJC prosthesis group. As for segment movements, difference in flexion, lateral bending or torsion between ACJC prosthesis group and control group was not statistically significant, while ACJC prosthesis group showed an increase in extension (P < 0.05) compared to that of the control group. In addition, ACJC prosthesis group demonstrated better flexion, extension and lateral bending compared to those of Orion plating system group (P < 0.05). Difference in adjacent inter-vertebral ROM of the ACJC prosthesis group was not statistically significant compared to that of the control group.

Conclusion

After cervical subtotal corpectomy, reconstruction with ACJC prosthesis not only obtained instant stability, but also reserved segment motions effectively, without abnormal gain of mobility at adjacent inter-vertebral spaces.     

In vivo analysis of cervical kinematics after implantation of a minimally constrained cervical artificial disc replacement

Introduction

To better understand cervical kinematics following cervical disc replacement (CDR), the in vivo behavior of a minimally constrained CDR was assessed.

Methods

Radiographic analysis of 19 patients undergoing a 1-level CDR from C4–5 to C6–7 (DISCOVER, Depuy-Spine, USA) was performed. Neutral–lateral and flexion–extension radiographs obtained at preop, postop and late follow-up were analyzed for segmental angle and global angle (GA C2–7). Flexion–extension range of motion was analyzed using validated quantitative motion analysis software (QMA®, Medical Metrics, USA). The FSU motion parameters measured at the index and adjacent levels were angular range of motion (ROM), translation and center of rotation (COR). Translation and COR were normalized to the AP dimension of the inferior endplate of the caudal vertebra. All motion parameters, including COR, were compared with normative reference data.

Results

The average patient age was 43.5 ± 7.3 years. The mean follow-up was 15.3 ± 7.2 months. C2–7 ROM was 35.9° ± 15.7° at preop and 45.4° ± 13.6° at follow-up (?p < .01). Based on the QMA at follow-up, angular ROM at the CDR level measured 9.8° ± 5.9° and translation was 10.1 ± 7.8 %. Individuals with higher ROM at the CDR level had increased translation at that level (p < .001, r = 0.97), increased translation and ROM at the supra-adjacent level (p < .001, r = .8; p = .005, r = .6). There was a strong interrelation between angular ROM and translation at the supra-adjacent level (p < .001, r = .9) and caudal-adjacent level (p < .001, r = .9). The location of the COR at the CDR- and supra-adjacent levels was significantly different for the COR-X (p < .001). Notably, the COR-Y at the CDR level was significantly correlated with the extent of CDR-level translation (p = .02, r = .6). Shell angle, which may be influenced by implant size and positioning had no impact on angular ROM but was correlated with COR-X (p = .05, r = ?.6) and COR-Y (p = .04, r = ?.5).

Conclusion

The COR is an important parameter for assessing the ability of non-constrained CDRs to replicate the normal kinematics of a FSU. CDR size and location, both of which can impact shell angle, may influence the amount of translation by affecting the location of the COR. Future research is needed to show how much translation is beneficial concerning clinical outcomes and facet loading.     

Sagittal geometry of the middle and lower cervical endplates

Purpose

Construct subsidence is a relatively common complication following anterior cervical fusion. Its occurrence has been revealed to be closely related to endplate-implant contact interface. But current literature focusing on the anatomy of cervical endplate is very scarce. The purpose of this morphometric study was to analyse the sagittal geometry, especially the concavity and slope, of vertebral endplates from C3 to C7 by employing data from CT scans.

Methods

Reformatted CT scans of 97 individuals were analyzed and endplate concavity depth, endplate concavity apex location, as well as endplate slope were measured in midsagittal plane. Those specific parameters were compared among different age and gender groups. Meanwhile, comparison between superior and inferior endplate of each vertebra was also performed.

Results

Age and gender did not influence endplate concavity depth, endplate concavity apex location, or endplate slope significantly (P > 0.05). Endplate concavity depths of superior endplates (range 0.9–1.2 mm) were significantly smaller than those of inferior endplates (range 2.1–2.7 mm). Endplate concavity apex was always located in the posterior half of the endplate, with the superior one ranged from 56 to 67 % and the inferior one 52 to 57 %. Average endplate slopes of superior endplates were between 4.5° and 9.0°, and average inferior endplate slopes ranged from 4.5° to 7.5°. Among all measured segments, C5 had the largest endplate slope values, while C7 the least.

Conclusions

Superior endplate is more flat than its inferior counterpart in middle and lower cervical spine, and the concavity apex is always located in the posterior half of the endplate. Endplate slope is correlated with cervical curvature, greater slope implying more significant lordosis. These sagittal endplate geometrical parameters should be taken into consideration when investigating implant subsidence following anterior cervical fusion.     

Usefulness of QuickDASH in patients with cervical laminoplasty

Purpose

Clumsiness and numbness of the upper extremity is one of the most common complaints of patients with cervical myelopathy. However, most previous evaluations after cervical laminoplasty have only been based on physicians’ points of view. We used Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) self-report questionnaire, which was designed to measure physical function and symptoms in people with upper-limb disorders to evaluate functional outcomes after laminoplasty.

Methods

Ninety-four patients who underwent laminoplasty for cervical myelopathy and replied to the questionnaire were included in this study. The average age was 62 years, and mean follow-up period was 61 months. The Japanese Orthopedic Association (JOA) score, Neck Disability Index (NDI), Short-Form Health Questionnaire of 36 questions (physical component score, PCS), upper-extremity pain (Numerical Rating Scale), and QuickDASH (0–100, 0 being least severe) were used to evaluate surgical outcomes. Satisfaction with treatment was also investigated, and internal consistency and criterion-related validity were evaluated. The QuickDASH cutoff value for patient satisfaction was determined by receiver operating characteristic curve (ROC) analysis.

Results

The mean total JOA scores were 10 before and 13 after surgery, and average postoperative QuickDASH score was 30. Cronbach α of the QuickDASH was 0.94. QuickDASH was significantly correlated with JOA score for upper-extremity motor and sensation, NDI, PCS, and pain. Cutoff value of the QuickDASH was 34.0 by ROC analysis. Significantly better QuickDASH scores were found for patients who were satisfied with treatment than for those who were not, whereas JOA score for upper-extremity motor function did not show a significant difference.

Discussion

QuickDASH had significant correlations with disease-specific JOA scores and other generic outcome measures. Moreover, QuickDASH significantly reflected patients’ satisfaction with treatment, whereas the JOA score for upper-extremity motor function did not.

Conclusion

QuickDASH was useful in evaluating upper-extremity functional outcomes after cervical laminoplasty.     

Comparison of titanium and polyetheretherketone (PEEK) cages in the surgical treatment of multilevel cervical spondylotic myelopathy: a prospective, randomized, control study with over 7-year follow-up

Purpose

Anterior cervical discectomy and fusion (ACDF) with titanium- or polyetheretherketone (PEEK)-cage reconstruction is widely used in the treatment of cervical spondylotic myelopathy (CSM). This study was to compare outcomes of titanium and PEEK cages in the treatment of multilevel CSM.

Methods

Between November 2002 and December 2004, a total of 80 patients with 3-level CSM were randomized in a 1:1 ratio to titanium group and PEEK group. The overall follow-up period of the patients ranged from 86 to 116 months (average 99.7 months). Clinical and radiological results were compared between titanium group and PEEK group.

Results

At the final follow-up, the clinical outcomes including JOA score, NDI score, and the excellent and good rates of clinical outcomes in the PEEK group were better than those in the titanium group. More loss of the Cobb angles and the intervertebral height was observed in the titanium group, resulting in the radiological parameters in the titanium group becoming inferior to the PEEK group at the final follow-up. Cage subsidence rates were 34.5 and 5.4 % in the titanium and PEEK groups, respectively. Fusion was observed in all patients of two groups at the final follow-up. Two patients presented with cage dislocation without clinical symptoms in the titanium group.

Conclusions

In surgical treatment of multilevel CSM, PEEK cage is superior to titanium cage in maintenance of intervertebral height and cervical lordosis, resulting in better clinical outcomes in the long-term follow-up.     

Bryan人工间盘置换与前路减压融合治疗颈椎退行性疾病的中期随访研究

 目的 评价人工椎间盘置换术治疗颈椎退行性疾病的中期疗效,并探讨其是否可以减少邻近节段退变的发生。方法 前瞻性对比分析接受颈椎人工间盘置换术(置换组,45例)与颈椎前路减压融合术(融合组,48例)治疗的颈椎退行性疾病患者的随访6年临床疗效和影像学资料。临床疗效评价指标为日本骨科协会评分(Japanese Orthopaedic Association Scores,JOA)、颈椎功能残障指数量表(neck disability index,NDI)和Odom评分。影像学评价指标为矢状位曲度、活动度、邻近节段退变。结果28例置换组患者和35例融合组患者完成随访。两组患者末次随访的JOA评分和NDI均较术前有明显改善,组间比较差异无统计学意义。92.9%的置换组患者和97.1%的融合组患者Odom评分获得很好或较好的结果。两组患者颈椎矢状位曲度末次随访较术前均得到保持。颈椎整体活动度置换组末次随访与术前无明显差异,而融合组则是明显降低。置换组置换节段活动度术前为9.5°±3.7°,术后3个月为7.0°±3.0°,末次随访为6.6°±4.1°,末次随访较术后3个月无明显改变。邻近节段退变评估采用侧位X线片和MRI T2加权像,置换组上、下邻近节段退变均明显少于融合组。结论 Bryan人工椎间盘置换术6年的随访结果基本满意,能更好地保留颈椎生理活动及生物力学环境,从而降低邻近节段退变的发生率。     

Effect of Modic changes on spinal canal stenosis and segmental motion in cervical spine

Purpose

Few studies have reported the characteristics of Modic changes (MCs) in the cervical spine in contrast to the lumbar spine. The purpose of this study was to identify the prevalence of MCs in the cervical spine and to elucidate the relationship of MCs with spinal canal stenosis and angular motion.

Methods

437 consecutive, symptomatic patients with neck pain with or without neurogenic symptoms were included in this study. MRI in multiple positions was performed with dynamic motion of the cervical spine in upright, weight-bearing neutral, flexion and extension positions. Type of MC, intervertebral disc degeneration grade, spinal cord compression grade and sagittal angular motion between flexion and extension for each segment from C2–3 to C6–7 were evaluated.

Results

MCs were observed in 84 out of 437 patients (19.2 %) and in 109 out of 2,185 motion segments (5.0 %) with type 2 changes predominating. Disc degeneration grades and spinal cord compression grades of segments with MCs were significantly higher than those without MCs. Sagittal angular motion of segments with MCs were significantly lower than those without MCs. Multiple logistic regression analysis revealed that significantly elevated odds ratios for MCs were observed in segments with severe disc degeneration, severe spinal canal compression and less angular motion.

Conclusion

The cervical segments with MCs were significantly more likely to have disc degeneration and spinal canal stenosis. In addition, the segments with MCs had significantly less angular motion, which suggests MCs may correlate with loss of mobility.