Long-term kinematic analysis of cervical spine after single-level implantation of Bryan cervical disc prosthesis

Background contextCervical arthroplasty theoretically reduces the risk of adjacent level disc degeneration and segmental instability that may be seen after a cervical fusion. An essential argument in confirming the utility of cervical arthroplasty is long-term confirmation that cervical disc replacements can maintain physiological kinematics at the index and adjacent levels.PurposeThe purpose of this in vivo prospective study was to characterize the long-term segmental kinematic outcomes after cervical arthroplasty.Study design/settingProspective cohort study.Patient sampleTwenty patients with a 5-year clinical follow-up who underwent anterior cervical discectomy with insertion of the Bryan cervical disc.Outcome measuresPhysiological measures (kinematic analysis of lateral neutral, flexion, and extension radiographic imaging).MethodsTwenty consecutive patients with degenerative disc disease were followed with regular radiographic imaging after implantation of the Bryan cervical disc prosthesis. Lateral neutral, flexion, and extension radiographs (n=240) were analyzed using Quantitative Motion Analysis software (Medical Metrics, Inc., Houston, TX, USA) to measure the biomechanical profile at the index level and adjacent levels up to 5 years after surgery. Parameters collected included range of motion (ROM), functional spinal unit (FSU) angle, anterior and posterior disc heights, sagittal translation, and center of rotation (COR).ResultsBiomechanics of the implanted artificial cervical disc was maintained up to 5 years with no significant changes in ROM, FSU angle, disc height, sagittal translation, and COR values when compared with early postoperative performance. Artificial discs were able to adequately restore and maintain preoperative kinematics. Early differences seen in disc height and FSU angle did not change during the duration of follow-up. No significant kyphotic changes or decrease in ROM were seen at the adjacent spinal levels.ConclusionsThe Bryan cervical disc prosthesis provides for a durable solution for functional spinal motion at the operated level and maintained the preoperative kinematics at adjacent levels at the 5-year follow-up.     

单节段Bryan人工颈椎间盘置换术后异位骨化的发生率和疗效观察

目的评估单节段Bryan人工颈椎间盘置换术后异位骨化发生情况,分析异位骨化对术后疗效影响。方法回顾分析2005年10月-2007年10月48例行单节段Bryan人工颈椎间盘置换术患者临床资料。男27例,女21例;年龄33～51岁,平均40.5岁。脊髓型颈椎病8例,神经根型颈椎病27例,混合型颈椎病13例。病程2～14个月,平均10.3个月。病变节段:C3、43例,C4、56例,C5、630例,C6、79例。术后采用疼痛视觉模拟评分(VAS)、颈椎功能障碍指数(NDI)、置换节段活动度评价疗效;并将患者按术后是否发生异位骨化分为两组,比较术后1、2、3、4年以上各指标差异。结果患者术中及术后均无严重并发症发生。48例均获随访,随访时间48～72个月,平均56.6个月。术后各时间点VAS评分及NDI均较术前显著改善(P<0.05);除术后3 d,其余各时间点置换节段活动度与术前比较差异均无统计学意义(P>0.05)。术后4年共13例(27.08%)发生异位骨化,其中1级8例,2级3例,3级2例。异位骨化组和无异位骨化组患者术后各时间点置换节段活动度及VAS评分、NDI比较,差异均无统计学意义(P>0.05)。结论单节段Bryan人工颈椎间盘置换术后异位骨化发生率相对较高,异位骨化对人工颈椎间盘置换节段活动度影响较小,对术后疗效无明显影响。     

Cervical kinematics after fusion and bryan disc arthroplasty

INTRODUCTION: Disc arthroplasty has been shown to provide short-term clinical results that are comparable with those attained with traditional anterior cervical discectomy and fusion. One proposed benefit of arthroplasty is the ability to prevent or delay adjacent level operations by retaining motion at the target level and eliminating abnormal adjacent activity. This paper compares motion parameters for single-level anterior cervical discectomy and fusion and disc replacement patients at the index level and adjacent segments. METHODS: Radiographic data from patients enrolled in a prospective, randomized clinical trial were selected for kinematic assessment of cervical motion. All patients received either a single-level fusion with allograft and anterior cervical plate (Atlantis anterior cervical plate, n=13) or a single-level artificial cervical disc (Bryan Cervical Disc prosthesis, n=9) at either C5/C6 or C6/C7. Flexion, extension, and neutral lateral radiographs were obtained preoperatively, immediately postoperatively, and at regular intervals up to 24-month time points. Cervical vertebral bodies were tracked on the digital radiographs using quantitative motion analysis software (QMA, Medical Metrics) to calculate the functional spinal unit motion parameters including range of motion (ROM), translation, and center of rotation. If visible, the functional spinal unit parameters were obtained at the operative level, and also the level above and the level below. RESULTS: As expected, significantly (P<0.006 at 3, 6, 12, and 24 mo) more flexion/extension motion was retained in the disc replacement group than the plated group at the index level. The disc replacement group retained an average of 6.7 degrees at 24 months. In contrast, the average ROM in the fusion group was 2.0 degrees at the 3-month follow-up and gradually decreased to 0.6 degrees at 24 months. The flexion/extension ROM both above and below the operative level was not statistically different for the disc-replaced and fusion patients, however, mobility increased for both groups over time. The anterior/posterior translation that occurs with flexion/extension motion remained unchanged for the disc replacement group at the level above the target disc preoperatively and postoperatively. In contrast, the translation increased for the level above the fusion. At the 6-month follow-up, the increase in translation was significantly greater for patients that were fused (P<0.02) than for patients that received a disc replacement. This change was not significant at 12 months. DISCUSSION: Previous studies have shown the Bryan disc to maintain mobility at the level of the prosthesis. The long-term clinical benefit of maintenance of motion is postulated to be the ability to delay or avoid adjacent level operations. This study reveals that there is no difference in flexion/extension ROM at the level above and below either a fusion or Bryan arthroplasty. There is, however, an increase in anterior/posterior translation at the cephalad adjacent level in patients with arthrodesis while the Bryan arthroplasty retains normal translation for the same amount of flexion/extension at the adjacent level. CONCLUSION: The Bryan disc may delay adjacent level degeneration by preserving preoperative kinematics at adjacent levels.     

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.     

人工椎间盘置换术治疗跳跃型多节段颈椎病的中期疗效

 目的 评价 Bryan 人工间盘置换术治疗跳跃型多节段颈椎病的疗效。方法 回顾性分析 2002 年 2 月至 2012 年 5 月接受 Bryan 间盘置换术（Bryan 组）或颈前路减压植骨融合术（ACDF 组）治疗的跳跃型多节段颈椎病患者相关资料。临床功能评估采用日本矫形外科协会（Japanese orthopaedic association,JOA）评分、颈椎功能障碍指数（neck disability index,NDI）、疼痛视觉模拟评分（visual analoguc scale,VAS）,影像学评估采用颈椎矢状位曲度、颈椎整体活动度及中间节段活动度,并于末次随访时评估邻近节段退变情况。结果 49 例患者随访超过 24 个月,Bryan 组 18 例,ACDF 组 31 例。两组患者性别、年龄、疾病类型等人口学资料的差异无统计学意义。两组患者术后 JOA、NDI、VAS 评分均较术前有明显改善。两组间各时间节点比较仅末次随访时 VAS 评分的差异有统计学意义。Bryan 组术后轴性症状发生率、颈椎活动度和未手术节段活动度分别为 11.1%、35.5°±5.9°和 7.3°±1.4°,ACDF 组分别为 45.2%、24.5°±6.2°、10.1°±1.6°,差异均有统计学意义。Bryan 组患者邻近节段无明显退变,ACDF 组 2 例出现退变,但无需再次手术。结论 应用 Bryan 间盘置换术治疗跳跃型多节段颈椎病,可有效改善神经功能,保留颈椎整体活动度,减少未手术节段活动度的代偿性增加,从而降低邻近节段退变及轴性症状发生率。     

颈椎人工椎间盘置换术患者选择与异位骨化形成的相关性分析

 目的 分析颈椎人工椎间盘置换术患者选择与术后异位骨化形成的相关性。方法 回顾性分析2003年12月至2008年12月,48例接受Bryan人工颈椎间盘置换术且随访时间超过5年的患者资料,男21例,女27例;年龄20~53岁,平均42岁;脊髓型颈椎病34例,神经根型颈椎病14例;单节段置换术38例,包括C_3-4 3例、C_4-5 5例、C_5-6 28例、C_6-7 2例;双节段置换术9例,包括C_4-5、C_5-6 4例、C_5-6、C_6-7 5例;三节段置换术1例（C_3-4、C_4-5、C_5-6）;共59个手术节段。在术后颈椎侧位X线片上使用McAfee分级法评价异位骨化形成。使用Logistic回归分析患者性别、术前手术节段活动度、置换节段脊柱功能单位曲度、置换节段与相邻节段椎间隙高度比值等因素与术后异位骨化形成的关系。对阳性结果及其选择阈值采用接受者操作特征（receiver operating characteristic, ROC）曲线及曲线下面积（area under the ROC curve, AUC）进行检验和量化分析。结果 48例患者术后均获得5年以上随访,随访时间60~120个月,平均70.3个月。术后59个节段中,20个出现异位骨化,发生率为33.9%（20/59）。患者性别、节段活动度、置换节段脊柱功能单位曲度和术前置换节段椎间隙高度这四方面因素中,仅术前置换节段与相邻节段椎间隙高度比值与术后异位骨化的形成具有显著相关性。通过ROC曲线分析该因素的AUC为0.813,95%置信区间为0.666~0.959,据此计算出病变节段与相邻节段椎间隙高度比值的临床最佳判断阈值为0.9。结论 患者选择相关临床因素中的术前置换节段椎间隙高度与术后异位骨化形成具有相关性;针对可变旋转中心的Bryan颈椎人工椎间盘假体,术前病变节段椎间隙高度较相邻节段丢失超过10%者不适合行人工椎间盘置换术。     

单节段Bryan人工椎间盘置换术后异位骨化形成对置换节段活动度的影响

目的探讨单节段Bryan人工椎间盘置换术后异位骨化（heterotopic ossification,HO）形成及其对置换节段活动度（range of motion,ROM）的影响。方法回顾分析2003年12月～2009年8月期间接受单节段前路减压及Bryan人工椎间盘置换术的患者40例。患者平均随访38.8个月。应用医学影像存储与传输系统观察随访时的HO形成情况并测量手术前后置换节段ROM。利用独立样本t检验分析HO形成与否以及不同HO分级与置换节段ROM间的关系。结果本组研究中单节段Bryan人工椎间盘置换术后HO的发生率为37.5%,对发生HO的患者采用McAfee分级：Ⅰ级2例,Ⅱ级3例,Ⅲ级8例,Ⅳ级2例。所有患者术前颈椎ROM平均为8.82°,随访时为8.52°。其中未发生HO的患者随访时ROM平均为9.77°,发生HO的患者随访时ROM平均为6.43°,差异有统计学意义（P〈0.05）。Ⅰ级和Ⅱ级的HO患者随访时ROM平均为8.76°,Ⅲ级和Ⅳ级的患者为5.26°,差异有统计学意义（P〈0.05）。结论 Bryan人工椎间盘置换术后形成HO会导致置换节段ROM的减少,McAfee分级Ⅲ、Ⅳ级的HO患者较之Ⅰ、Ⅱ级更加明显。     

Local and global subaxial cervical spine biomechanics after single-level fusion or cervical arthroplasty

An experimental in vitro biomechanical study was conducted on human cadaveric spines to evaluate the motion segment (C4–C5) and global subaxial cervical spine motion after placement of a cervical arthroplasty device (Altia TDI™,Amedica, Salt Lake City, UT) as compared to both the intact spine and a single-level fusion. Six specimens (C2–C7) were tested in flexion/extension, lateral bending, and axial rotation under a ± 1.5 Nm moment with a 100 N axial follower load. Following the intact spine was tested; the cervical arthroplasty device was implanted at C4–C5 and tested. Then, a fusion using lateral mass fixation and an anterior plate was simulated and tested. Stiffness and range of motion (ROM) data were calculated. The ROM of the C4–C5 motion segment with the arthroplasty device was similar to that of the intact spine in flexion/extension and slightly less in lateral bending and rotation, while the fusion construct allowed significantly less motion in all directions. The fusion construct caused broader effects of increasing motion in the remaining segments of the subaxial cervical spine, whereas the TDI did not alter the adjacent and remote motion segments. The fusion construct was also far stiffer in all motion planes than the intact motion segment and the TDI, while the artificial disc treated level was slightly stiffer than the intact segment. The Altia TDI allows for a magnitude of motion similar to that of the intact spine at the treated and adjacent levels in the in vitro setting.     

颈椎前路分节段减压融合术三维有限元分析

目的应用三维有限元模型分析颈椎前路分节段减压融合术的生物力学特点。方法建立C2～7三维有限元模型,在此基础上根据临床实际建立手术模型,观察不同手术方式的颈椎活动范围和邻近节段椎间盘应力。结果建立的颈椎三维有限元模型有效,分节段减压融合术比传统椎体次全切除术术后邻近节段椎间盘应力小,二者颈椎活动范围相同。结论颈椎前路分节段减压融合术比传统椎体次全切除术更符合人体生物力学要求。     

Comparison of radiographic changes after ACDF versus Bryan disc arthroplasty in single and bi-level cases

The object of this study is to compare radiographic outcomes of anterior cervical decompression and fusion (ACDF) versus cervical disc replacement using the Bryan Cervical Disc Prosthesis (Medtronic Sofamor Danek, Memphis, TN) in terms of range of motion (ROM), Functional spinal unit (FSU), overall sagittal alignment (C2–C7), anterior intervertebral height (AIH), posterior intervertebral height (PIH) and radiographic changes at the implanted and adjacent levels. The study consisted of 105 patients. A total of 63 Bryan disc were placed in 51 patients. A single level procedure was performed in 39 patients and a two-level procedure in the other 12. Fifty-four patients underwent ACDF, 26 single level cases and 28 double level cases. The Bryan group had a mean follow-up 19 months (12–38). Mean follow-up for the ACDF group was 20 months (12–40 months). All patients were evaluated using static and dynamic cervical spine radiographs as well as MR imaging. All patients underwent anterior cervical discectomy followed by autogenous bone graft with plate (or implantation of a cage) or the Bryan artificial disc prosthesis. Clinical evaluation included the visual analogue scale (VAS), and neck disability index (NDI). Radiographic evaluation included static and dynamic flexion-extension radiographs using the computer software (Infinitt PiviewSTAR 5051) program. ROM, disc space angle, intervertebral height were measured at the operative site and adjacent levels. FSU and overall sagittal alignment (C2–C7) were also measured pre-operatively, postoperatively and at final follow-up. Radiological change was analyzed using χ ² test (95% confidence interval). Other data were analyzed using the mixed model (SAS enterprises guide 4.1 versions). There was clinical improvement within each group in terms of VAS and NDI scores from pre-op to final follow-up but not significantly between the two groups for both single (VAS p = 0.8371, NDI p = 0.2872) and double (VAS p = 0.2938, NDI p = 0.6753) level surgeries. Overall, ROM and intervertebral height was relatively well maintained during the follow-up in the Bryan group compared to ACDF. Regardless of the number of levels operated on, significant differences were noted for overall ROM of the cervical spine (p < 0.0001) and all other levels except at the upper adjacent level for single level surgeries (p = 0.2872). Statistically significant (p < 0.0001 and p = 0.0172) differences in the trend of intervertebral height measurements between the two groups were noted at all levels except for the AIH of single level surgeries at the upper (p = 0.1264) and lower (p = 0.7598) adjacent levels as well as PIH for double level surgeries at the upper (p = 0.8363) adjacent level. Radiological change was 3.5 times more observed for the ACDF group. Clinical status of both groups, regardless of the number of levels, showed improvement. Although clinical outcomes between the two groups were not significantly different at final follow-up, radiographic parameters, namely ROM and intervertebral heights at the operated site, some adjacent levels as well as FSU and overall sagittal alignment of the cervical spine were relatively well maintained in Bryan group compared to ACDF group. We surmise that to a certain degree, the maintenance of these parameters could contribute to reduce development of adjacent level change. Noteworthy is that radiographic change was 3.5 times more observed for ACDF surgeries. A longer period of evaluation is needed, to see if all these radiographic changes will translate to symptomatic adjacent level disease.     

颈人工椎间盘置换术治疗颈椎病的临床研究

目的 探讨Bryan颈人工椎间盘假体置换术治疗颈椎病的临床疗效,同时与颈前路减压植骨融合术相比较,观察两种术式的近期临床疗效.方法 脊髓型和神经根型颈椎病患者共48例,21例（22个节段）行颈前路颈人工椎间盘假体置换术（置换组）,27例（32个节段）采用颈前路减压植骨融合术（融合组）.两组患者分别在术前,术后,术后3、6、12、18个月观察以下指标：JOA评分;摄颈椎前屈后伸位、左右侧屈位X线片,观察置换组的假体稳定性和植入节段及上下临近节段的活动度,观察融合组融合节段的上下临近节段的关节活动度;MRI或CT扫描检查颈人工椎间盘假体位置及有无异位骨化现象.结果 两组术后临床症状缓解,脊髓功能改善,均无并发症.两组JOA评分比较：术后各时间段较术前明显提高（P＜0.01）,两组术后各时间段之间的评分比较无显著差异.术后各时间段随访摄X线片显示：置换组置换节段较术前保留了部分关节活动度,上下临近关节活动度未显著增加,未发现假体偏移或下沉;而融合组临近节段活动度显著高于置换组（P＜0.01）.术后CT或MRI扫描显示：置换组假体位于临近上、下终板骨的中央,未见假体周围异位骨化现象;融合组出现1例下临近节段退变压迫脊髓.结论 与颈前路减压植骨融合术比较,颈人工椎间盘置换术既能良好地达到前路减压目的,又能保持颈椎病变节段的部分活动度和稳定性,且未显著增加上下临近节段活动度,取得了较好的近期临床疗效.     

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.     

椎间盘置换联合邻近节段cage融合治疗双节段颈椎间盘突出症的近期疗效

目的:探讨椎问盘置换联合邻近节段cage融合治疗双节段颈椎问盘突出症的近期疗效.方法:2006年5月～2008年11月手术治疗双节段颈椎间盘突出症患者13例,男8例,女5例,年龄35～60岁,平均47岁:以脊髓受压表现为主者6例,神经根性症状为主者7例;病变节段C4/5、C5/6 8例,C5/6、C6/7 3例,C4/5、C6/7 2例.均一期行单节段Bryan人工椎间盘置换和邻近节段cage融合,置换节段和融合节段为相邻间隙11例.非相邻间隙2例.术前、术后进行JOA评分(17分法)和颈椎残障功能量表(neck disability index,NDl)评定,术后进行Odom标准评定,随访观察椎间盘似体稳定性、假体活动度、cage融合状态及cage位移情况等.结果:手术时间90～160min,平均130min;术中m血量50～400ml,平均130ml.术中、术后无并发症发生.随访6个月～3年,平均19个月,末次随访时,JOA评分由术前9.2±3.2分增加至13.5±1.8分(P<0.01),NDI评分由术前40.8±4.7分降至28.5±5.4分(P<0.01),Odom评定结果优6例,良3例,尚可2例,差2例.人工椎间盘稳定,置换节段平均活动度为9.5°,cage植骨全部融合,无cage松动和沉陷.结论:颈椎间盘置换加邻近节段cage融合为双节段颈椎间盘突出症的治疗提供了新的选择方式,兼顾了颈椎的稳定和运动功能,近期临床效果良好.     

Bryan人工颈椎间盘置换术的中期随访结果分析

目的 观察Bryan人工颈椎间盘置换术后临床和影像学结果以及相邻节段退变的情况.方法 回顾性分析术后随访时间超过2年的26例单节段置换患者的临床资料,临床效果采用JOA和Odom评分进行评定.采用x线片观察手术节段活动度和椎旁骨化.采用X线片和MRI观察对比相邻节段退变情况.术前X线片示置换节段的活动度为2°～12°,平均为6.9°.结果 (1)临床结果:18例脊髓型颈椎病患者随访时JOA评分平均16分,平均改善率84%,8例神经根型颈椎病患者随访时临床症状全部消失.Odom分级:优秀15例,良好7例,一般4例.(2)X线片:术后置换节段的活动度为1°～14°,平均7.8°;7例出现假体周围异位骨化,仅1例假体运动消失,其余6例平均活动度为5.3°.相邻节段椎间隙高度术后无明显变化.(3)MRI T2加权像:根据Pfirrmann椎间盘退变分级方法,相邻节段椎间盘的分级术后无明显加重表现;相邻节段黄韧带肥厚对椎管的侵占率术后无明显加重;但是上下相邻椎间盘侵占率均略有增加.结论 Bryan人工颈椎间盘置换术保留了置换节段的运动性,避免了相邻节段的加速退变,2年以上随访效果优良.     

Anterior bone loss after cervical Bryan disc arthroplasty: insight into the biomechanics following total disc replacement

BACKGROUND CONTEXTCervical disc arthroplasty (CDA) is an innovative procedure launched in the early 2000s. Compared with anterior cervical discectomy and fusion, many studies show that CDA offers equivalent clinical outcomes while reducing secondary procedures and total cost.PURPOSEWe sought to determine the incidence of anterior bone loss after CDA and the related biomechanical effects.STUDY DESIGN/ SETTINGRetrospective chart review.PATIENT SAMPLEPatients who underwent CDA with one level Bryan Disc (Medtronic SofamorDanek, Memphis, TN, USA) at one institution.OUTCOME MEASURESRadiological measurements, including the extent of anterior bone loss, global alignment angle, shell angle, lordotic angle, mean degree of angle of the endplate with the horizontal line, global range of motion (ROM) and ROM of the index level were recorded. The grading of anterior bone loss of the index level was defined as Grade 0, no remodeling; Grade 1, spur disappearance or mild change in body contour; Grade 2, obvious bone regression with Bryan Disc exposure.METHODSAnatomical measures and ROM were compared by grade of bone loss.RESULTSOf the 121 patients included in the study, anterior bone loss was found in 53 (43.8%) on the upper adjacent level and 54 (44.6%) on the lower adjacent level. Twenty-nine patients (23.9%) had anterior bone loss in both levels. The majority of cases had Grade 1 anterior bone loss. Grade 2 bone loss was noted in the upper adjacent vertebra in only 5 patients and in 4 patients in the lower adjacent vertebra. Age, sex, operative level, and hybrid surgery had no effect on anterior bone loss. Most radiological assessments, including global alignment angle, lordotic angle, mean degree of angle of the endplate with the horizontal line, global ROM, and ROM of the index level, showed no correlation to anterior bone loss. Shell angle was found to be different in groups with or without remodeling in the upper adjacent level: 5.0 degreesin the Grade 0 group and 7.0 degrees in the Grade 1-2 group, p<.05.CONCLUSIONSMany more patients than predicted had anterior bone loss. Increasing the shell angle of the artificial disc may increase the incidence of anterior bone loss after CDA. Further study of the biomechanics following CDA should help clarify the mechanisms at work.     

Bryan人工颈椎间盘置换对颈椎功能影响的临床分析

目的 探讨Bryan人工颈椎间盘置换手术对颈椎功能的影响.方法 对2003年12月至2007年8月施行的164例患者200个椎间盘的人工颈椎间盘置换手术进行回顾性分析.164例患者中,男性102例,女性62例,年龄25～70岁,平均47岁;单间隙置换132例,双间隙置换28例,三间隙置换4例.均采用Bryan人工颈椎间盘假体.手术严格按照Bryan人工颈椎间盘假体植入的标准操作程序进行.术后颈托外固定2周.结果 随访时间2～44个月,平均26个月.JOA评分改善率56%.椎间活动度:矢状位术前平均活动度14.4°,术后1周5.7°,末次随访时平均14.7°,与手术前相比差异无统计学意义.邻近间隙矢状位术前平均活动度10.9°,术后1周5.5°,末次随访时平均8.2°,主要是由上邻接间隙的活动度没有达到术前水平所致.患者满意度94%.1例患者术后6个月假体松动,以后稳定;1例患者术后7个月假体发生1 mm下沉,以后稳定;3例后方融合.无前方融合、食管损伤、喉返神经损伤以及再手术病例.手术操作单间隙平均90 min,双间隙平均130 min.结论 人工颈椎间盘置换手术临床疗效良好.     

Biomechanical evaluation of a metal-on-metal cervical intervertebral disc prosthesis

Background contextIn vitro nondestructive flexibility testing of the CerviCore total disc replacement (TDR) was performed. It was hypothesized that TDR would not significantly alter biomechanics relative to intact, whereas rigid fixation would cause significant changes.PurposeTo assess the ability of a cervical metal-on-metal saddle-shaped TDR to replicate normal biomechanics in vitro.Study designHuman cadaveric flexibility experiment.MethodsNine human cadaveric C3–T1 specimens were tested intact, after TDR and after anterior plating. Flexion, extension, lateral bending, and axial rotation were induced by pure moments; flexion-extension was then repeated using a simplified muscle force model with 70-N follower load. Optical markers measured three-dimensional intervertebral motion, and eight points of laminar surface strain were recorded near the left and right C5–C6 facet joints. Biomechanical parameters studied included range of motion (ROM), lax zone (LZ), angular coupling pattern, sagittal instantaneous axis of rotation (IAR), and facet loads normal to the facet joint plane. Mean values of parameters were compared statistically using repeated measures analysis of variance and Holm-Sidak tests.ResultsTotal disc replacement caused significant reduction in ROM during extension (p=.004) and significant reduction in LZ during lateral bending (p=.01). However, plating significantly reduced both ROM and LZ during flexion, extension, and lateral bending (p<.006). Sagittal IAR shifted relative to intact by 3.6 mm after TDR (p>.05) and 6.5 mm after plating (p>.05). Coupled axial rotation/degree lateral bending was 99% of intact after TDR but 76% of intact after plating (p=.15). Coupled lateral bending/degree axial rotation was 95% of intact after TDR but 85% of intact after plating (p=.43). Neither construct altered facet loads from intact.ConclusionsWith regard to ROM, LZ, IAR, and coupling, deviations from intact biomechanics were less substantial after TDR than after plating. Facet load alterations were minimal with either construct. Our results show that this particular TDR permits ROM and maintains some measures of kinematics in a cadaver model.     

Clinical and radiological analysis of Bryan cervical disc arthroplasty: eight-year follow-up results compared with anterior cervical discectomy and fusion

Purpose

Bryan cervical disc arthroplasty has been reported with satisfactory short- and medium-term clinical results. However, the long-term clinical and radiographic outcomes are seldom reported. The purpose of this study was to compare the eight-year follow-up results in patients who underwent Bryan disc arthroplasty with patients received ACDF, and assess the incidence of heterotopic ossification (HO) and its effect on clinical outcome and mobility of the device.

Methods

Thirty-one patients underwent Bryan disc arthroplasty, and 35 patients underwent ACDF were included in the study. The Japanese Orthopedic Association (JOA) scores, neck disability index (NDI), visual analogue scale (VAS) of neck and arm pain, and the radiographs were used to evaluate the outcomes. The heterotopic ossification (HO) was determined by CT scan and was classified into three subgroups to compare the related effect. Adjacent segment degeneration (ASD) was also observed.

Results

At final follow-up, there were no significant differences in JOA scores between two groups, but the improvement in NDI and neck or arm VAS were significantly greater in the Bryan disc cohort. The range of motion at the index level was 7.0° in Bryan group, while 100 % bone fusion were achieved in ACDF group. HO was observed in 18 (51.4 %) levels. There were more restricted movement of the prosthesis and slight higher rate of axial pain in patients with severe-HO (grade III and IV). Fourteen (28.6 %) levels developed ASD in Bryan group, which was significantly lower than that (58.6 %) in ACDF group.

Conclusions

At eight year follow-up, the clinical and radiographic outcomes of Bryan cervical disc arthroplasty compared favorably to those of ACDF. It avoided accelerated adjacent segment degeneration by preserving motion. However, severe HO restricted the ROM of the index levels and maybe associated with post-operative axial pain.

     

Use of instrumented pedicle screws to evaluate load sharing in posterior dynamic stabilization systems

Background contextDynamic stabilization is an alternative to fusion intended to eliminate or at least minimize the potential for adjacent level degeneration. Different design approaches are used in pedicle screw-based systems that should have very different effects on the loading of the posterior column and intervertebral disc. If the implant system distributes these loads more evenly, loads in the pedicle screws will be reduced, and screw loosening will be prevented.PurposeThe purpose of this study was to determine how two different design approaches to dynamic stabilization systems, Dynesys System and the Total Posterior Spine (TOPS) System, affect the load carried by the pedicle screws.Study design/settingA controlled laboratory study in which the magnitude of the moments on pedicle screws during flexion–extension and lateral bending were measured after implantation of two posterior dynamic stabilization devices into cadaveric spines.MethodsFive lumbar spines were tested in flexion–extension and lateral bending. Specimens were tested sequentially: first intact, then with the Dynesys system implanted, and finally with the TOPS system implanted. Range of motion (ROM) for each construct was measured with a 210 N and 630 N compressive load. The pedicle screws were instrumented with strain gages, which were calibrated so that the moments on the screws could be determined from the strain measurements.ResultsCompared with intact values, ROM decreased in flexion–extension and lateral bending when the Dynesys System was implanted. With implantation of the TOPS System, ROM returned to values that were not significantly different from the intact values. The moments in the screws with the Dynesys System were significantly higher than with the TOPS System with increases of as much as 56% in flexion–extension and 86% in lateral bending.ConclusionsThe design of the posterior stabilization device influences the amount of load seen by the pedicle screws and therefore the load sharing between spinal implant and bone.     

颈椎间盘置换治疗脊髓型颈椎病的疗效观察

目的探讨颈椎间盘置换治疗脊髓型颈椎病的疗效。方法 2006年10月-2008年10月,采用椎间盘置换治疗20例(26个节段)脊髓型颈椎病患者。男8例,女12例;年龄26～65岁,平均46岁。病程2～18个月,平均7个月。单节段置换14例,双节段置换6例。术后以Odom等标准评价疗效,以疼痛视觉模拟评分(VAS)评价颈、肩部及上肢疼痛情况。X线片测量假体椎间盘间隙角及颈椎过屈、过伸位活动度,观察异位骨化、骨赘形成及假体松动等情况。结果术后切口均Ⅰ期愈合,无严重并发症发生。20例均获随访,随访时间30～48个月,平均34个月。术后28个月按Odom等标准获优17例、良3例,颈、肩部及上肢VAS评分均较术前显著改善(P<0.05)。术后30个月,20个置换节段未融合,假体活动度为(10.6±4.5)°,与上位相邻节段的(10.8±3.7)°和下位相邻节段的(7.5±4.2)°比较差异均无统计学意义(P>0.05)。术后10例13个节段发生异位骨化,1例假体后方移位;其他假体无移位、下沉、松动等并发症发生。结论颈椎间盘置换治疗脊髓型颈椎病能维持颈椎正常活动范围和生理弯曲,但其功能和对邻近节段的影响需进一步随访。