下颈椎前路椎弓根螺钉固定系统的设计与运用

目的：研究下颈椎前路椎弓根螺钉钢板系统运用的可行性,为临床使用提供依据。方法：对16具颈椎标本随机分割获得C3．4,C4加C5．6,C6,7各8个运动单元（functionalspinalunit,FSu）,共32个FSU。运用下颈椎前路椎弓根螺钉钢板系统模拟植入重建FSU稳定性。测量钢板螺钉与椎体之间的适应性,运用X线摄片及CT扫描及重建评估下颈椎前路椎弓根螺钉植入的准确性,对于穿破椎弓根的标本,解剖明确其累及周围组织的情况。结果：32个FSU共计植入下颈椎前路椎弓根螺钉64枚,所有螺钉均顺利植入,无术中植入困难者。螺钉植入后与钢板螺钉孔之间的匹配程度好,未见难以锁紧的情况。钢板与椎体之间适应性良好。X线片提示所有64枚下颈椎前路椎弓根螺钉植入位置满意,螺钉长短合适。CT横断位像提示共有6枚螺钉在下颈椎椎弓根穿出,2枚内侧皮质1度穿破,4枚1度外侧缘皮质穿破累及横突孔内侧缘,未见螺钉≥2度穿破椎弓根。2枚下颈椎前路椎弓根内侧皮质1度穿破的患者,解剖发现仅有椎管内椎弓根内侧的静脉丛累及,未见硬膜囊受压,未见神经根受累。4枚1度外侧缘穿破的患者有1枚横突孔内椎静脉的累及,未见椎动脉穿破累及的情况,但其中1枚螺钉紧换椎动脉而行。结论：下颈椎前路椎弓根螺钉钢板系统适应下颈椎前路椎弓根螺钉固定重建,有临床运用价值。     

数字骨科技术在儿童上颈椎手术中的应用

目的:探讨数字骨科技术在儿童上颈椎手术中的应用价值。方法:我院2009年3月～2011年3月共收治7例上颈椎疾患患儿。其中,先天性游离齿状突伴寰枢椎脱位4例,枢椎肿瘤伴寰枢椎脱位1例,顽固性寰枢椎旋转脱位1例,颅底凹陷症合并寰枕脱位1例。术前均行薄层CT扫描,将数据输入Mimic,Simpleware软件后,建立三维仿真模型,用于手术模拟和术中辅助,并根据需要设计寰枢椎椎弓根导航模板。在数字骨科技术支持下共实施后路手术4例,前路手术2例,前后联合手术1例。术后CT钉道扫描观察寰枢椎螺钉的置入情况,并采用日本矫形外科协会JOA评分系统对脊髓功能进行术前、术后评分。结果:7例患者,均顺利实施手术,手术时间3～6h,平均3.5±0.6h;手术出血300～400ml。实施后路寰椎椎弓根钉棒固定5例,实施前路TARP手术2例。共置入后路寰椎椎弓根螺钉10枚,枢椎椎弓根螺钉10枚,寰椎前路侧块螺钉2枚,枕骨髁前路螺钉2枚,枢椎逆行椎弓根螺钉2枚,枢椎椎体钉2枚。术后CT扫描显示,所有螺钉位置良好,未出现螺钉偏入椎管或椎动脉孔的现象。术后患者肢体麻木症状减轻或消失,四肢肌力明显改善,JOA评分由术前的8.6±1.5分,提高到15±1.8分(P<0.05)。结论:采用数字骨科技术辅助手术,可以有效提高儿童上颈椎手术的成功率,降低手术风险。     

Anterior cervical plate fixation with the titanium hollow screw plate system. A preliminary report

Morscher, of Switzerland, has developed an anterior cervical spine plate system (THSP) that does not require screw purchase of the posterior cortex. This design eliminates potential neurologic complications usually associated with the anterior plate system, but maintains the mechanical advantages of internal fixation. The authors reviewed 13 consecutive patients in whom the THSP system was applied. Indications for the use of this device included acute trauma in three patients, trauma of more than 6 weeks' duration in five patients, and spondylosis in five patients. Fifteen plates and 58 screws were placed, with no screws purchasing the posterior cortex. Postoperative immobilization varied from no immobilization to four-poster brace. With a mean follow-up of 13 months, all 13 patients went on to fusion. One patient had screws placed in the disc rather than in bone and went on to malunion. In all other patients, radiographs did not demonstrate screw migration, screw-bone lucency, graft dislodgement, or malunion. No patient suffered neurologic injury as a result of this device. The THSP system facilitates reliable fusion with minimal complications. Its use should be considered in multilevel anterior spine defects, posttraumatic cervical kyphosis, and cervical fractures with posterior disruption requiring anterior fusion.     

Pull-out strength of Caspar cervical screws.

Anterior cervical instrumentation as an adjunct to bone fusion has an important role in cervical spine surgery. Posterior vertebral body cortex purchase is strongly recommended in the use of the Caspar system, although few biomechanical data exist to validate this requirement. In this study, Caspar screws were placed in 43 human cadaveric cervical vertebral bodies, either putting them into the posterior vertebral cortex as identified radiographically or penetrating it by 2 mm as recommended in the literature. Pull-out tests were conducted with tension applied to a connected plate at 0.25 mm/s, and force-deformation data were obtained. Failure typically occurred with clean pull-out; in most instances, cancellous bone remained attached to screw threads. Mean load without posterior cortical purchase was 375 +/- 53 N; with penetration it was 411 +/- 70 N. These differences were nonsignificant. Average deformation to failure was 1.41 +/- 0.10 mm in the group without posterior cortical penetration. In the posterior penetration group, mean deformation was 1.56 +/- 0.16 mm. Again, differences were not significant. Posterior cortical penetration does not improve the pull-out strength of Caspar screws in an isolated vertebral body model, but other biomechanical studies need to be done before insertion methods are altered.     

Biomechanical evaluation of a newly developed monocortical expansion screw for use in anterior internal fixation of the cervical spine. In vitro comparison with two established internal fixation systems

STUDY DESIGN: The primary biomechanical stability of anterior internal fixation of the cervical spine obtained with a new monocortical expansion screw in vitro was evaluated. OBJECTIVES: To determine whether the anterior internal fixation of the spine obtained with the new monocortical expansion screw provides biomechanical stability comparable with that obtained with bicortical fixation. SUMMARY OF BACKGROUND DATA: The anterior plate instrumentation used with bicortical screw fixation in the cervical spine provides a primary stability superior to that associated with monocortical screw fixation. However, bicortical screws have the potential to perforate the posterior cortex. Therefore, monocortical instrumentation systems were developed, but without the biomechanical stability associated with bicortical systems. A new expansion screw for monocortical fixation was developed to improve biomechanical stability of monocortical systems. METHODS: Three different internal fixation systems were compared in this study: 1) H-plate with AO 3.5-mm bicortical screws, 2) cervical spine locking plate with monocortical screws, and 3) H-plate with the new monocortical expansion screws. Eight fresh human cadaver spine segments from C4 to C7 were tested in flexion-extension, axial rotation, and lateral bending using pure moments of +/- 2.5 Nm without axial preload. Five conditions were investigated consecutively: 1) intact spine; 2) uninstrumented spine with the segment C5-C6 destabilized; 3-5) instrumentation of the segment C5-C6 with the three implants mentioned above after removal of the disc and insertion of an interbody spacer. RESULTS: Between bicortical and monocortical expansion screw H-plate fixation, no significant differences were observed in all load cases concerning range of motion and neutral zone. The neutral zone and range of motion were significantly larger for the cervical spine locking plate than for bicortical and monocortical expansion screw fixation in all load cases, except neutral zone for axial rotation versus bicortical screw fixation. The instrumented cases only had a significantly lower range of motion and neutral zone than the intact cases in extension-flexion, whereas for lateral bending and axial rotation no significant differences could be observed. Because the experimental design precluded any cyclic testing, the data represent only the primary stability of the implants. CONCLUSIONS: In anterior instrumentation of the cervical spine using a H-plate, the new monocortical expansion screw provides the same biomechanical stability as the bicortical 3.5-mm AO screw and a significantly better biomechanical stability than the cervical spine locking plate. Therefore, the expansion screw may be an alternative to the bicortical fixation and does not involve the risk of penetration of the posterior vertebral body cortex.     

Irreducible dislocations of the cervical spine with a prolapsed disc: preliminary results from a treatment technique

STUDY DESIGN: The preliminary results from a treatment technique for irreducible dislocations of the cervical spine with prolapsed disk are reported. OBJECTIVE: To report the success of a technique for grafting and instrumentation of the anterior cervical spine before reduction. This technique is useful in cervical fracture-dislocations irreducible through the anterior approach that must be approached first from the front because of a prolapsed disc. SUMMARY OF BACKGROUND DATA: In the treatment of cervical facet dislocations, a third anterior procedure often is necessary to accomplish the anterior instrumentation and fusion. The reported technique describes a method that eliminates this third procedure by using a cervical buttress plate. METHODS: Between August of 1996 and October 1998, four patients had dislocation of the cervical spine with a prolapsed disc that could not be reduced using the anterior approach. After discectomy and endplate preparation, a tricortical bone graft was harvested from the iliac crest, placed in the interspace, and held with a buttress plate screwed in two places into the superior vertebral body. The anterior wound then was closed. The posterior elements were exposed and the facets reduced by flexing the neck and posteriorly translating the superior segment. Fluoroscopy was used during the reduction to ensure that the graft was pulled into the interspace, that the screws in the buttress plate did not pull out of the superior vertebral body, and that the reduced graft did not impinge on the spinal cord. A posterior fusion was performed and the posterior wound closed. RESULTS: All the patients had consolidation of both anterior and posterior fusions. No cases of instrument failure occurred, either anteriorly or posteriorly. No cases of neurologic deterioration occurred, and no complications were attributable to the use of this technique. CONCLUSION: The reported technique was used successfully in the treatment of four patients with irreducible dislocations of the cervical spine.     

A simplified technique for anterior cervical discectomy and fusion using a screw-plate implanted over the Caspar distractor pins

The author presents a simplified technique for midline screw-plate fixation in fusion procedures after anterior cervical discectomy, in which the plate is introduced over the Caspar distractor pins. The Uniplate system used, with a single screw in each vertebral body, minimizes bone damage to the vertebral body as the screws can be fixed in the holes previously used for the Caspar distractor pins. This simplified version of the classical anterior cervical fusion technique saves surgical time, facilitates screw insertion, and obviates the need for manipulations to stabilize the plate before the screws are inserted. It provides immediate stability comparable to other plate systems. To the author's knowledge, this is the first report on cervical fusion with the Uniplate system with the plate being introduced over the Caspar distractor pins.     

Anterior interbody fusion using the cervical spine locking plate

Surgical Principles The Cervical Spine Locking Plate system (CSLP) is designed to perform anterior fusions of the cervical and upper thoracic spine. The screws are locked in the H shaped plate providing intrinsic angle stability. Early osseous integration is enhanced by titanium plasma spray coating and by the hollow and perforated design of the screws. These features enhance the primary and secondary stability of the fixation. Therefore the penetration of the posterior cortex of the vertebra with the screws is not necessary, which is a decisive asset compared to conventional plate systems. This essentially diminishes the intraoperative risks. The primary stability is superior to that of conventional plate systems as the screws are tightly locked into the plate in convergence.     

Complications of transpedicular screw fixation in the cervical spine

Today, posterior stabilization of the cervical spine is most frequently performed by lateral mass screws or spinous process wiring. These techniques do not always provide sufficient stability, and anterior fusion procedures are added secondarily. Recently, transpedicular screw fixation of the cervical spine has been introduced to provide a one-stage stable posterior fixation. The aim of the present prospective study is to examine if cervical pedicle screw fixation can be done by low risk and to identify potential risk factors associated with this technique. All patients stabilized by cervical transpedicular screw fixation between 1999 and 2002 were included. Cervical disorders included multisegmental degenerative instability with cervical myelopathy in 16 patients, segmental instability caused by rheumatoid arthritis in three, trauma in five and instability caused by infection in two patients. In most cases additional decompression of the spinal cord and bone graft placement were performed. Pre-operative and post-operative CT-scans (2-mm cuts) and plain X-rays served to determine changes in alignment and the position of the screws. Clinical outcome was assessed in all cases. Ninety-four cervical pedicle screws were implanted in 26 patients, most frequently at the C3 (26 screws) and C4 levels (19 screws). Radiologically 66 screws (70%) were placed correctly (maximal breach 1 mm) whereas 20 screws (21%) were misplaced with reduction of mechanical strength, slight narrowing of the vertebral artery canal (<25%) or the lateral recess without compression of neural structures. However, these misplacements were asymptomatic in all cases. Another eight screws (9%) had a critical breach. Four of them showed a narrowing of the vertebral artery canal of more then 25%, in all cases without vascular problems. Three screws passed through the intervertebral foramen, causing temporary paresis in one case and a new sensory loss in another. In the latter patient revision surgery was performed. The screw was loosened and had to be corrected. The only statistically significant risk factor was the level of surgery: all critical breaches were seen from C3 to C5. Percutaneous application of the screws reduced the risk for misplacement, although this finding was not statistically significant. There was also a remarkable learning curve. Instrumentation with cervical transpedicular screws results in very stable fixation. However, with the use of new techniques like percutaneous screw application or computerized image guidance there remains a risk for damaging nerve roots or the vertebral artery. This technique should be reserved for highly selected patients with clear indications and to highly experienced spine surgeons.     

Anatomical study of position of the rib head for placing anterior vertebral body screws in a chinese population

In this study, the variability of rib head position in a Chinese population in terms of the spinal canal and vertebral body was analyzed using computed tomography (CT). Images from transverse CT scan of the T4 to T12 vertebral bodies of 30 normal individuals were 3-dimensionally reconstructed, and analyzed for measurement of parameters that define the relative anatomic position of the rib head. We have found that the distance between the anterior border of the rib head and the posterior margin of the vertebral body, posterior safe angle, and the distance between the most inferior border of the rib head and inferior end plate in the sagittal plane gradually decrease. However, the distance between the anterior boarder of the rib head and the anterior margin of the vertebral body, transverse dimension, anterior safe angle, and the distance between the most inferior border of the rib head and superior end plate in the sagittal plane gradually increase from T4 to T12. This indicates that the position of the rib head is oriented from a more anterior position to a more posterior position and from a more superior position to a more inferior position as the number of the vertebra increases, which is different from what has been reported from western populations. Our study has identified useful parameters to define the position of the rib head, and provides a comprehensive reference guide for accurate and safe instrumentation of vertebral body screws in treating related spine diseases.     

下颈椎关节突关节与椎体后缘关系的影像学研究

目的：研究探讨下颈椎关节突关节前缘与椎体后缘的位置关系，为临床行下颈椎经关节螺钉植入时评价进钉深度提供参考。方法：选取无明显下颈椎畸形的标准颈椎侧位X线片100张，下颈椎标准CT平扫片50张，测量下颈椎关节突关节顶点、中部、基底部前缘与椎体后缘的距离（分别记为HS，HM，HI），椎体后缘之前为负、之后为正。并对测量数据行统计学分析。结果：所有关节突关节前缘距离、椎体后缘的距离从顶点到基底部逐渐减小（HS〉HM〉HI）。C。关节突关节前缘大多位于椎体后缘之前（HS，HM，HI均为负值）；C4.5C5.6关节突关节前缘逐渐后移；Co，，关节突关节前缘均位于椎体后缘之后（HS，HM，HI均为正值）。下颈椎关节突关节顶点前缘与椎体后缘的距离HS从C。到C6，7逐渐增大，C3．4为（0±0．25）mm，C4．5为（2．03±0．47）mm，C5．6为（2．45±0．56）mm，C6．7为（2．91±1．05）mm；下颈椎关节突关节中部前缘与椎体后缘的距离HM从C3.4到C6.7逐渐增大，C3.4为（-1．57±0.53）mm,C4.5为（O．50±0．26）mm，C5．6为（0．56±0．36）mm，C6．7为（1．54±0．39）mm；下颈椎关节突关节基底部前缘与椎体后缘的距离HI从C3.4到C6.7逐渐增大，C3.4为（-2．03±0．40）mm，C4．5为（0±0．30）mm，C5，6为（0．50±0．44）mm，C6．7为（1．08±0．70）mm。结论：在行下颈椎经关节螺钉固定时，螺钉的头部在C3.4应位于相应榷体后缘前方0～2mm，C4.5应位于相应椎体后缘之后0-2mm，C5.6应位于相应椎体后缘之后0．5-2．5him，C6.7应位于相应椎体后缘之后1～3mm。下颈椎关节突关节前缘与椎体后缘关系的确立，可为临床工作中下颈椎经关节螺钉植入时判断进钉深度提供参考。     

A biomechanical comparison of modern anterior and posterior plate fixation of the cervical spine

STUDY DESIGN: A biomechanical study was designed to assess relative rigidity provided by anterior, posterior, or combined cervical fixation using cadaveric cervical spine models for flexion-distraction injury and burst fracture. OBJECTIVES: To compare the construct stability provided by anterior plating with locked fixation screws, posterior plating with lateral mass screws, and combined anterior-posterior fixation in clinically simulated 3-column injury or corpectomy models. SUMMARY OF BACKGROUND DATA: Anterior plating with locked fixation screws is the most recent design and is found to provide better stability than the conventional unlocked anterior plating. However, there are few data on the direct comparison of biomechanical stability provided by anterior plating with locked fixation screws versus posterior plating with lateral mass screws. Biomechanical advantages of using combined anterior-posterior fixation compared with that of using either anterior or posterior fixation alone also have not been well investigated yet. METHODS: Biomechanical flexibility tests were performed using cervical spines (C2-T1) obtained from 10 fresh human cadavers. In group I (5 specimens), one-level, 3-column injury was created at C4-C5 by removing the ligamentum flavum and bilateral facet capsules, the posterior longitudinal ligament, and the posterior half of the intervertebral disc. In group II (5 specimens), complete corpectomy of C5 was performed to simulate burst injury. In each specimen, the intact spine underwent flexibility tests, and the following constructs were tested: (1) posterior lateral mass screw fixation (Axis plate) after injury; (2) polymethylmethacrylate anterior fusion block plus posterior fixation; (3) polymethylmethacrylate block plus anterior (Orion plate) and posterior plate fixation; and (4) polymethylmethacrylate block plus anterior fixation. Rotational angles of the C4-C5 (or C4-C6) segment were measured and normalized by the corresponding angles of the intact specimen to study the overall stabilizing effects. RESULTS: Posterior plating with an interbody graft showed effective stabilization of the unstable cervical segments in all loading modes in all cases. There was no significant stability improvement by the use of combined fixation compared with the posterior fixation with interbody grafting, although combined anterior-posterior fixation tended to provide greater stability than both anterior and posterior fixation alone. Anterior fixation alone was found to fail in stabilizing the cervical spine, particularly in the flexion-distraction injury model in which no contribution of posterior ligaments is available. Anterior plating fixation provided much greater fixation in the corpectomy model than in the flexion-distraction injury model. This finding suggests that preservation of the posterior ligaments may be an important factor in anterior plating fixation. CONCLUSIONS: This study showed that the posterior plating with interbody grafting is biomechanically superior to anterior plating with locked fixation screws for stabilizing the one-level flexion-distraction injury or burst injury. More rigid postoperative external orthoses should be considered if the anterior plating is used alone for the treatment of unstable cervical injuries. It was also found that combined anterior and posterior fixation may not improve the stability significantly as compared with posterior grafting with lateral mass screws and interbody grafting.     

Missing anterior cervical plate and screws: a case report

STUDY DESIGN: A case report of an anterior cervical plate and screws that disappeared completely. OBJECTIVES: To present a case of a missing anterior cervical plate and screws, this being quite a rare complication of a cervical implant. SUMMARY OF BACKGROUND DATA: No mention of this complication was found in the literature. METHODS: Methods in the literature and clinical presentation are reviewed. RESULTS: Dislodgment of an anterior cervical plate occurred in association with an methicillin-resistant Staphylococcus aureus infection. Three months later the implants had disappeared, presumably passing without notice through the gastrointestinal tract. Whole body fluoroscopy could not identify any residual plate or screws. No esophageal fistula could be detected by barium meal swallow study. CONCLUSIONS: The plate and screws became dislodged, eroded through the posterior wall of the esophagus, then traversed the limit of the gastrointestinal tract, passing with feces without significant morbidity. Whether the methicillin-resistant Staphylococcus aureus infection contributed to this unique circumstance or is coincidentally related to it remained a matter of speculation.     

下颈椎经关节螺钉植入深度的侧位X线片评价

目的 运用侧位x线片评价下颈椎经关节螺钉植入深度的安伞性.方法 采用6具新鲜颈椎标本(C1～T1),每具标本均在直视下植入下颈椎经关节螺钉(每侧4枚螺钉:C3,4、C4,5、C5,6、C6,7各1枚),分别在植入螺钉尖端穿出最后一层皮质0、2、4、6 mm时摄标准侧位x线片,将侧位X线片上椎体垂直等分为四部分,定义为1～4区,并定义椎体后缘之后相当宽度的区域为前1区.每次植入时记录螺钉尖端在X线侧位片的位置,以综合评价螺钉植入的安全性.结果 在C3,4和C4,5螺钉尖端穿出最后一层皮质0 mm时,87.5％在1区,穿出2 mm时,54.2％在1区.当螺钉尖端穿出4 mm时,75.O％在2区,穿出6mm时58.3％在3区.在C5,6和C6,7,穿出0mm时75.0％位于前1区,穿出2mm时,54.2％位于前1区;穿出4 mm时83.3％位于1区,穿出6mm时,50.0％位于2区.结论 侧位X线片町用于评价下颈椎经关节螺钉植入深度的安全性.在侧位X线片上,理想的螺钉尖端位置为C3,4和C4,5应位于1区,而在Cs,6和C6.7应位于前1区.     

上颈椎损伤合并不连续下颈椎损伤的一期手术治疗

目的 探讨上颈椎损伤合并不连续的下颈椎损伤的临床特点及手术治疗策略.方法 2004年5月至2007年8月,对上颈椎损伤合并不连续的下颈椎损伤9例患者进行一期手术治疗.术前神经功能按Frankel评级:A级2例,C级3例,E级4例.其中上颈椎损伤均采用后路手术,经椎弓根寰枢固定融合8例,枕颈固定1例;下颈椎损伤采用后路手术6例,其中以不连续经椎弓根短节段钉棒固定融合4例,2例采用联合上颈椎经椎弓根连续固定;余3例同期行前路减压钛板固定.结果 所有患者获得6～48个月(平均13.7个月)随访.术中无一例椎动脉损伤.术后无气管切开或拔管延迟情况,无严重肺部感染、呼吸衰竭、应激性溃疡等并发症发生.患者复位及融合满意,1例2枚下颈椎椎弓根断钉.神经功能:除2例Frankel A级的患并无恢复外,余均为E级.结论 上颈椎损伤合并不连续下颈椎损伤导致颈椎极度不稳定,伴有的神经损伤常源于下颈段.一期手术治疗,包括上颈椎后路经椎弓根固定及下颈椎后路经椎弓根或前路减压固定,相对安全且可获得满意疗效.     

脊柱压缩性、爆裂性骨折的X线平片及CT的诊断价值

目的探讨X线平片、CT检查对脊柱压缩性缩性、爆裂性骨折的诊断价值。方法收集我院2005年2月-2008年11月间136例胸腰椎压缩性、爆裂性骨折病例,观察分析X线平片及CT上的脊柱骨性结构、椎管损伤情况。结果X线平片上136例患者127例显示胸腰椎压缩性、爆裂骨折,其中14例椎管内见明确小骨片（10％）;9例未见明确骨折征象。CT上全部病例可见椎体粉碎骨折。40例前柱骨折;22例椎体中柱骨折;25例后柱骨折;脊柱前、中两柱同时骨折23例：前、中、后三柱同时骨折26例。结论CT检查更能显示脊柱压缩性、爆裂性骨折中骨折碎片、脊椎前,中,后柱损伤的详情,临床上要重视X线平片及cT检查的互补作用。     

The effect of locking fixation screws on the stability of anterior cervical plating

STUDY DESIGN: Current anterior cervical plate systems were tested with locked and unlocked fixation screws and with unicortical and bicortical fixation screws to determine fixation rigidity and pull-off strengths. OBJECTIVES: To evaluate the effects of screw-plate locking and screw length on fixation strength and stability of anterior cervical plates. SUMMARY OF BACKGROUND DATA: New plate systems provide for rigid locking of the screw-plate interface, theoretically increasing construct rigidity, allowing unicortical fixation, and preventing screw back-out. There are few data on the effects of locking screws on the stability of anterior cervical plating. METHODS: Eighty fresh lamb vertebrae (C3-T1) were used. Test systems included: Cervical Spine Locking Plate (CSLP; Synthes, Paoli, PA, Orion plate (Sofamor-Danek, Memphis, TN), and Acroplate (AcroMed, Cleveland, OH). The CSLP and Orion plates were tested with fixation screws, locked and unlocked, and the AcroMed plate with unicortical and bicortical screw purchase. Biomechanical testing of the screw-plate constructs was performed to determine the initial bone-plate rigidity and pull-off strength. A 2.5-Nm cyclic bending moment was then applied to additional constructs for 10(5) cycles, and these constructs retested. RESULTS: Locked CSLP and Orion constructs were more rigid than all unlocked unicortical systems initially and after cyclic loading (P < 0.05). After cycling, the rigidity of all unlocked unicortical constructs decreased significantly (P < 0.05). There was no significant difference in pull-off strengths between the CSLP, the Orion, and the unicortical AcroMed plate. However, all had significantly less pull-off strength than the AcroMed plate with bicortical screws. A negative correlation was observed between initial pull-off strength and sagittal vertebral body diameter. CONCLUSIONS: Locking screws significantly increased the rigidity of the tested screw-plate systems initially and after cyclic loading. Because pull-off strength was affected by the vertebral body diameter, use of longer unicortical screws may be clinically beneficial in the patient with larger cervical vertebrae.     

手术治疗严重上颈椎骨折脱位的疗效分析

目的探讨手术治疗严重上颈椎骨折脱位的临床疗效和应用价值。方法采用前后路手术以及颈椎前路钢板和后路钉棒枕颈融合联合复位技术治疗32例严重上颈椎骨折脱位患者。前后路联合手术均在颅骨牵引下经鼻腔气管插管全身麻醉下进行,患者先采用俯卧位,后路植入侧块螺钉、减压、复位,恢复颈椎的序列,植骨融合后拆除颅骨牵引改置仰卧位行前路减压、植骨及自锁钛板固定。术后定期复查X线片观察损伤节段的稳定性和融合率,以Frankel分级判定脊髓神经功能的恢复情况。结果 Frankel分级除6例A级者及3例D级者外,其余患者均有1~2级提高,其中9例达到E级。32例中有3例于术后1个月内死亡,29例获得6~32个月随访。脱位均完全复位,无植骨不融合。损伤节段稳定,颈椎椎间高度及生理曲度都得到良好重建及维持,未出现内固定断裂、松动及脱出,无血管、神经、食道损伤等并发症。结论颈椎前后路联合手术治疗严重上颈椎骨折脱位,能完全恢复颈椎序列,损伤节段术后获得即刻稳定,方便术后护理和功能锻炼,有利于脊髓功能恢复。     

Biomechanical comparison of anterior cervical spine locked and unlocked plate-fixation systems

Three different anterior plate-fixation systems are available for the stabilisation of the cervical spine: (1) the cervical spine locking plate (CSLP), (2) dynamic plates allowing vertical migration of the fixation screws, and (3) various types of plates that are secured with either monocortical or bicortical unlocked screws. Unicortical screw purchase does not involve the risk of posterior cortex penetration and possible injuries to the spinal cord. The development of locking plates with unicortical screw-fixation and intrinsic stability of the screw–plate interface, via an angle-stabilised connection, was an attempt to increase the stability of unicortical screw-fixation systems. The aim of the study was to compare the biomechanical properties of a non-locking, anterior-plate system with 4.5 mm screw fixation and a locking anterior-plate system, in a single destabilised cervical spine-motion segment. Using fresh cadaveric cervical spine specimen C3–C7, multidirectional flexibility was measured at the C4–C5 level in an unconstrained test system, before and after destabilisation and fixation with an anterior plate with either locked or unlocked screw purchase. Direct comparison of the fixed cervical spine segments with unlocked and locked anterior-plate fixation did not demonstrate significant differences. This in vitro study documented that neither locked nor unlocked anterior-plate fixation can increase stability in all modes of testing. H-plate spondylodesis with unlocked screws seems to provide sufficient mechanical integrity in most cases of monosegmental lesions.     

The cervical spine and its relation to anterior plate-screw fixation: a quantitative study

Multilevel discectomy and inter-vertebral body fusion combined with anterior plate-screw fixation is the common procedure in cervical spine surgery. The correct placement of the screws is an important factor for the outcome of these operations. Yet no systematic approach has been undertaken to optimize the geometry of the fixation-plates regarding the position of the screw-perforations. In this study MRI scans of 50 consecutive patients were analyzed regarding the height of each segment (C3–C7), the anterior–posterior diameter of the vertebral body and the distance between the vertebral arteries. Based on this data we developed Standard Spine Models. Using these models we designed two plates each for single and two-level surgery, and three plates each for three- and four-level surgery. These ten plates do fit the cervical spines of all 50 patients examined in this study. With these plates the screw-perforations could be positioned efficiently over the bodies of the concerned vertebrae. This should facilitate the selection of a plate and the positioning of the screws. Thus the surgeons might save time and the screws might be positioned more exactly and entirely in the vertebral bodies, ensuring a secure fixation.