C1-C2 intra-articular screw fixation for atlantoaxial posterior stabilization

STUDY DESIGN: A trial of a new posterior stabilization technique for atlantoaxial instability and a report of preliminary results. OBJECTIVES: To describe a new posterior stabilization technique for atlantoxial instability. SUMMARY OF BACKGROUND DATA: Magerl's transarticular screw fixation is an accepted technique for rigid atlantoaxial stabilization, which reportedly has yielded many good clinical results. However, the technique is technically demanding and poses a risk of injury to the nerves and veins. METHODS: Eleven patients who had been treated with intra-articular screw fixation in combination with Halifax interlaminar clamp (OSTEONICS, Allendale, NJ) for atlantoaxial instability were observed. Results of their clinical examinations and biomechanical studies using resinous bones of a cervical spine model were reviewed. RESULTS: In all patients, occipital pain, neck pain, and neural deficit improved, and bony fusion with no correction loss was shown on radiography. To date, no vascular or neural complications have been found, and no instrumentation failures have occurred. In the biomechanical study, the Halifax with transarticular screw fixation had significantly greater flexion stiffness than the Halifax only or the Halifax with intra-articular screw fixation, but the torsion stiffness of the Halifax with intra-articular screw fixation was significantly greater than that of the other Halifax combinations. CONCLUSION: The preliminary results showed that this technique was effective in strengthening the rotational stability of the atlantoaxial fixation and was considered useful for atlantoaxial posterior stabilization.     

寰枢椎后路椎弓根螺钉固定的生物力学评价

目的：评价寰枢椎后路椎弓根螺钉固定的生物力学稳定性。方法：6具新鲜颈椎标本，按随机顺序，对每一标本先后行C1-C2椎弓根螺钉、Magerl螺钉、Brooks钢丝以及螺钉联合钢丝固定，在脊柱三维运动实验机上测量其三维运动范围。结果：Magerl螺钉或C1-C2椎弓根螺钉联合Brooks钢丝组成的固定系统的三维运动范围最小。C1-C2椎弓根螺钉固定的前后屈伸运动范围与Brooks钢丝固定无差异，但大于Magerl螺钉；其左右侧屈运动范围小于Brooks钢丝固定，大于Magerl螺钉；其轴向旋转角度明显小于Brooks钢丝固定，但与Magerl螺钉无统计学差异。结论：C1-C2椎弓根螺钉的三维稳定性与Magerl螺钉相当，联合Brooks钢丝固定可进一步提高其稳定性。     

Meniscus-like synovial fold in the atlantoaxial (C1-C2) joint.

Some of the synovial joints in the human body have a fibrocartilaginous disc interposed between the joint surfaces to absorb or evenly distribute loads. Examples of fibrocartilagenous discs include the intervertebral disc, knee joint meniscus, and triangular fibrocartilages in the distal radioulnar joint and the acromioclavicular joints. The joint capsule and the surrounding tissue from nine cervical spines (18 C1-C2 joints) were dissected and prepared for gross examination and histology. We found meniscus-like synovial folds in 13 of the 18 atlantoaxial joints. These folds were located at the anteromedial and posteromedial aspect of the joint. Each synovial fold was of semilunar shape, with a thickened outer edge and thin inner edge giving a wedge-shape cross section. In one case, the synovial fold was grossly similar in appearance to a knee joint meniscus, and on histological examination there was evidence of cartilagenous metaplasia in part of the fold. The findings are compared with the limited data reported in the literature.     

Biomechanical analysis of a novel hook-screw technique for C1-2 stabilization

The Food and Drug Administration has not cleared the following medical devices for the use described in this study. The following medical devices are being discussed for an off-label use: cervical lateral mass screws. Object As an alternative for cases in which the anatomy and spatial relationship between C-2 and a vertebral artery precludes insertion of C-2 pedicle/pars or C1-2 transarticular screws, a technique that includes opposing laminar hooks (claw) at C-2 combined with C-1 lateral mass screws may be used. The biomechanical stability of this alternate technique was compared with that of a standard screw-rod technique in vitro. Methods Flexibility tests were performed in 7 specimens (occiput to C-3) in the following 6 different conditions: 1) intact; 2) after creating instability and attaching a posterior cable/graft at C1-2; 3) after removing the graft and attaching a construct comprising C-1 lateral mass screws and C-2 laminar claws; 4) after reattaching the posterior cable-graft at C1-2 (posterior hardware still in place); 5) after removing the posterior cable-graft and laminar hooks and placing C-2 pedicle screws interconnected to C-1 lateral mass screws via rod; and 6) after reattaching the posterior cable-graft at C1-2 (screw-rod construct still in place). Results All types of stabilization significantly reduced the range of motion, lax zone, and stiff zone compared with the intact condition. There was no significant biomechanical difference in terms of range of motion or lax zone between the screw-rod construct and the screw-claw-rod construct in any direction of loading. Conclusions The screw-claw-rod technique restricts motion much like the standard Harms technique, making it an acceptable alternative technique when aberrant arterial anatomy precludes the placement of C-2 pars/pedicle screws or C1-2 transarticular screws.     

寰枢椎椎弓根螺钉固定融合技术治疗寰枢椎不稳

目的 探讨应用寰枢椎椎弓根螺钉固定技术治疗寰枢椎不稳的疗效.方法 对2003年6月至2009年3月收治的21例寰枢椎不稳患者应用寰枢椎椎弓根螺钉技术治疗,男14例,女7例;年龄28～66岁,平均42.5岁.齿状突骨折10例,先天性游离齿状突4例,Jefferson骨折合并齿状突骨折3例,类风湿关节炎致寰枢椎不稳4例.所有患者均伴有寰枢椎半脱位或失稳.患者术前JOA评分4～14分,平均9.1分.结果 21例患者共置入寰枢椎螺钉84枚,无一例患者发生脊髓、神经根和椎动脉损伤.术中均未发生椎动脉和脊髓损伤,有5例出现静脉丛出血.所有患者均获随访,时间6～48个月,平均16个月.术后JOA评分11～17分,平均15.9分,平均改善率为85.1%.骨折的齿状突均完全愈合,植骨块全部融化,无内固定断裂和松动.结论 寰枢椎椎弓根螺钉固定技术是治疗寰枢椎失稳的有效方法,具有固定牢靠、短节段固定,操作相对安全方便、融合率高等优点.     

寰枢椎椎弓根螺钉固定融合技术治疗寰枢椎不稳

目的 探讨应用寰枢椎椎弓根螺钉固定技术治疗寰枢椎不稳的疗效.方法 对2003年6月至2009年3月收治的21例寰枢椎不稳患者应用寰枢椎椎弓根螺钉技术治疗,男14例,女7例;年龄28～66岁,平均42.5岁.齿状突骨折10例,先天性游离齿状突4例,Jefferson骨折合并齿状突骨折3例,类风湿关节炎致寰枢椎不稳4例.所有患者均伴有寰枢椎半脱位或失稳.患者术前JOA评分4～14分,平均9.1分.结果 21例患者共置入寰枢椎螺钉84枚,无一例患者发生脊髓、神经根和椎动脉损伤.术中均未发生椎动脉和脊髓损伤,有5例出现静脉丛出血.所有患者均获随访,时间6～48个月,平均16个月.术后JOA评分11～17分,平均15.9分,平均改善率为85.1%.骨折的齿状突均完全愈合,植骨块全部融化,无内固定断裂和松动.结论 寰枢椎椎弓根螺钉固定技术是治疗寰枢椎失稳的有效方法,具有固定牢靠、短节段固定,操作相对安全方便、融合率高等优点.     

寰枢椎椎弓根螺钉固定融合技术治疗寰枢椎不稳

目的 探讨应用寰枢椎椎弓根螺钉固定技术治疗寰枢椎不稳的疗效.方法 对2003年6月至2009年3月收治的21例寰枢椎不稳患者应用寰枢椎椎弓根螺钉技术治疗,男14例,女7例;年龄28～66岁,平均42.5岁.齿状突骨折10例,先天性游离齿状突4例,Jefferson骨折合并齿状突骨折3例,类风湿关节炎致寰枢椎不稳4例.所有患者均伴有寰枢椎半脱位或失稳.患者术前JOA评分4～14分,平均9.1分.结果 21例患者共置入寰枢椎螺钉84枚,无一例患者发生脊髓、神经根和椎动脉损伤.术中均未发生椎动脉和脊髓损伤,有5例出现静脉丛出血.所有患者均获随访,时间6～48个月,平均16个月.术后JOA评分11～17分,平均15.9分,平均改善率为85.1%.骨折的齿状突均完全愈合,植骨块全部融化,无内固定断裂和松动.结论 寰枢椎椎弓根螺钉固定技术是治疗寰枢椎失稳的有效方法,具有固定牢靠、短节段固定,操作相对安全方便、融合率高等优点.     

The C1 claw device: a new instrument for C1-C2 fusion

A new fixation device for C1-C2 fusion is presented. It consists of a claw construct for the C1 arch that is rigidly attached to C1-C2 transarticular screws to form an instrument that combines anterior and posterior fixation in the same construct. The new device was successfully applied in a case with failed C1-C2 fusion that was initially stabilized with transarticular screws alone, where the usual posterior wiring was omitted due to a defect of the posterior C1 arch.     

Synovial cyst at the C1-C2 junction in a patient with atlantoaxial subluxation

Synovial cysts of the cervical spine causing myelopathy are rare. The pathogenesis of these cysts is often attributed to degenerative changes of the facet joints or microtrauma. The authors report a synovial cyst at the C1-C2 junction in a patient with atlantoaxial subluxation without a congenital anomaly or inflammatory conditions. A 72-year-old man presented with a progressive right-sided myelopathy attributed to a C1-C2 synovial cyst accompanied by atlantoaxial subluxation and C3-C6 spondylosis. Magnetic resonance imaging of the cervical spine showed a large cystic mass compressing the spinal cord located at the C1-C2 junction. A C1 hemilaminectomy, complete evacuation of the cyst contents, and posterior atlantoaxial fusion were performed, and a double-door laminoplasty was also done at C3-C6. The patient showed significant improvement of paresthesia and motor weakness of the right upper and lower extremities immediately after the operation. Synovial cysts should be considered in the differential diagnosis of an extradural mass of the upper cervical spine. Posterior fusion combined with direct excision of the cyst may be the optimum treatment of a synovial cyst at the C1-C2 junction in a patient with atlantoaxial subluxation.     

Traumatic posterior atlantoaxial dislocation without related fractures of C1-C2

Posterior dislocation without any associated fracture of odontoid is exceedingly rare and only 11 cases have been reported so far. A 32 year old male presented with pain, stiffness in neck, difficulty in breathing, associated lacerations on face and deformity of mandible and inability to open mouth. His plain radiographs, CT scan, MRI demonstrated a posterior dislocation of the atlas with respect of axis and a flake of bone from odontoid process on CT scan. He was successfully managed by closed reduction, C1C2 lateral mars pedicular screw stabilization and inter facetal fusion with synthetic bone graft substitute. At 10 months followup he had lost only 30° cervical rotation. The case is reported in view of rarity and to discuss the treatment rationale.     

C1-C2 transarticular screw fixation for atlantoaxial instability: a 6-year experience.

OBJECTIVE: We review a 6-year, single-center experience using the technique of C1-C2 transarticular screw fixation for atlantoaxial instability in 75 consecutive operations. METHODS: The study group was composed of 43 men and 32 women, with a mean age of 44 years (range, 8-76 yr). Each patient had documented atlantoaxial instability. In 28 patients (37%), atlantoaxial instability was a result of trauma; in 22 patients, (29%), it was a result of rheumatoid arthritis; in 16 patients (21%), it was a result of prior surgery; and in 9 patients (12%), it was a result of congenital abnormalities. All patients underwent stabilization with C1-C2 transfacetal screws and a posterior interspinous construct. Nine patients had unilateral screws placed. Postoperatively, the patients were maintained in a rigid cervical orthosis for a mean of 11 weeks (range, 8-15 wk); five patients were immobilized with halo fixation for a mean of 13 weeks (range, 10-16 wk). The mean follow-up period was 2.4 years (range, 1-5.5 yr). RESULTS: Osseous fusion was documented in 72 patients (96%). There were no hardware failures; however, three patients developed pseudarthrosis. Two superficial wound infections (one at the graft site and one at the cervical incision site) required antibiotic therapy. Four patients had transient suboccipital hypesthesia. No instances of an errant screw, dural laceration, or injury to the vertebral artery, spinal cord, or hypoglossal nerve were noted. CONCLUSION: C1-C2 transarticular screw fixation supplemented with an interspinous construct yielded a 96% fusion rate, with a low incidence of complications. We attribute our successful outcomes to careful preoperative assessment and meticulous surgical technique.     

寰枢椎椎弓根螺钉内固定术治疗儿童寰枢椎脱位的初步报告

目的:探讨寰枢椎椎弓根螺钉内固定手术治疗儿童寰枢椎脱位的可操作性和近期疗效。方法:2005年9月~2011年3月对16例儿童寰枢椎脱位患者采用寰枢椎椎弓根螺钉内固定术治疗,男9例,女7例;年龄5～13岁,平均9.1岁。均有枕颈部疼痛、颈部僵硬;3例有高位颈脊髓病表现,ASIA分级:D级2例,C级1例。术前均行颈椎正侧位及过伸过屈位X线片、CT和MRI检查,均诊断为寰枢椎脱位,其中寰椎横韧带断裂1例,寰枢椎骨折脱位1例,先天性齿状突畸形12例,寰枢椎固定旋转半脱位2例;颈脊髓受压5例。寰椎后弓(椎弓根)高度2.5~3.8mm,平均3.0mm;寰齿前间隙6~14mm,平均9mm。术前常规行牵引1~2周复位,完全复位7例,部分复位5例,不能复位4例。术中采用"寰椎椎弓根显露置钉法",在直视下行C1、C2置钉,复位固定,植骨融合。随访患者症状和神经功能改善情况,定期行颈椎X线片及CT复查,了解内固定及植骨融合情况。结果:16例均行双侧寰枢椎椎弓根螺钉内固定,手术过程顺利,64枚螺钉均成功置入,复位固定满意,无术中、术后神经和血管并发症。术中出血150~650ml,平均300ml;手术时间100~190min,平均130min。12例随访12~72个月,平均28.5个月,术后3~6个月寰枢椎均骨性融合;末次随访时,颈枕症状明显改善,3例术前有脊髓功能损害者均好转,2例术前ASIA分级D级者恢复到E级,1例术前ASIA分级C级者恢复到D级;未发现螺钉松动、断钉和寰枢椎再移位现象,未发现曲轴现象。结论:采用"寰椎椎弓根显露置钉法"行寰椎椎弓根螺钉内固定可操作性强,置钉安全性高;寰枢椎椎弓根螺钉内固定治疗儿童寰枢椎脱位的近期疗效满意。     

Biomechanical analysis of the C2 intralaminar fixation technique using a cross-link and offset connector for an unstable atlantoaxial joint

Background contextC2 intralaminar screws offer the advantage of avoiding the vertebral artery; however, biomechanical studies have demonstrated inferiority of C2 intralaminar screw fixation compared with C2 intrapedicular fixation in the presence of an odontoid fracture. Addition of a transverse cross-link may improve stability afforded by the lamina screws but will require the use of offset connectors to complete the construct.PurposeThe aims of this project were to evaluate whether transverse cross-links can add adequate stability to atlantoaxial constructs using C1 lateral mass and C2 intralaminar screw fixation. The secondary objective was to determine the biomechanical contribution of the C2 offset connectors.Study designIn vitro human cadaveric biomechanical study.MethodsTen cadaveric specimens were obtained and instrumented with C1 lateral mass, C2 pedicle, and C2 intralaminar screws. After intact spine testing, each C1–C2 construct was nondestructively evaluated under axial rotation (AR), flexion extension (FE), and lateral bending (LB). Intralaminar fixation was tested with and without offset connectors, which allowed for cross-link addition to the construct. After normal state evaluation, the odontoid was resected and analyses were repeated.ResultsPostreconstruction range of motion in AR, FE, and LB showed no significant differences between the four fixation constructs in the stable specimens. Transpedicular fixation at C2 proved superior to intralaminar techniques without a cross-link in AR and LB after destabilization with an odontoidectomy. The addition of a cross-link to the intralaminar construct improved segmental AR and LB stability to the level afforded by the transpedicular fixation. Offset connectors appeared to marginally weaken the intralaminar fixation, but the findings were not significant.ConclusionsCoupled with an offset connector and a cross-link, C2 intralaminar screws offer similar segmental stability to intrapedicular fixation in the presence of an unstable dens fracture. Lateral offset connectors at C2 do not significantly compromise stability of C1 lateral mass—C2 intralaminar fixation.     

新型寰椎钩棒及椎板钩联合枢椎椎弓根螺钉内固定的生物力学

目的 评价自行研制的寰椎后弓环抱钩棒及椎板钩联合枢椎椎弓根螺钉内固定系统的生物力学稳定性,为临床应用提供实验依据. 方法 6具新鲜尸体枕颈部标本,采用脊柱三维运动试验机依次对其齿状突切断后(A组)、寰椎椎板钩联合枢椎椎弓根螺钉内固定(B组)、自制寰椎钩棒及椎板钩联合枢椎椎弓根螺钉内固定(C组)、寰椎椎弓根螺钉联合枢椎椎弓根螺钉内固定(D组)等4种状态进行三维运动范围测试;分析比较新型寰枢椎后路内固定系统的稳定性. 结果 B组后伸平均ROM明显大于C、D组,差异均有统计学意义(P＜0.05);C、D组后伸平均ROM差异无统计学意义(P＞0.05);而B、C、D组间在其他角度ROM(前屈、侧屈、旋转)差异均无统计学意义(P＞0.05).结论 采用自制寰椎后弓钩棒及椎板钩联合枢椎椎弓根螺钉进行内固定,可为失稳的寰枢关节提供良好的即刻和较长期稳定性.     

前路经寰枢关节螺钉内固定术治疗寰枢椎不稳定的生物力学及临床研究

目的 探讨前路经寰枢关节螺钉内固定术的生物力学稳定性及疗效.方法 8具新鲜颈椎标本,对每一标本先后行正常状态、齿状突Ⅱ型骨折、前路经寰枢关节螺钉内固定术、后路Magerl螺钉内固定术4种状态三维运动范围的测定.并对20例创伤性寰枢椎不稳定患者施行前路经寰枢关节螺钉内固定术,在齿状突与寰椎前结节后方置入颗粒状松质骨.结果 前路经寰枢关节螺钉内固定术与后路Magerl螺钉内固定术均明显减少寰枢关节各方向运动范围,经统计学检验差异无统计学意义.20例患者中,1例颈脊髓完全损伤患者,术后1个月死于肺部感染.其余19例病例获得随访,时间7个月～3年,平均18个月,无椎动脉及脊髓损伤,所有病例获得骨性融合.结论 前路经寰枢关节螺钉内固定术,操作简便,固定可靠,损伤脊髓或椎动脉的风险较小.     

后路经侧块关节螺钉内固定技术治疗寰枢椎不稳

目的：评价Magerl法内固定治疗寰枢椎不稳或脱位的临床疗效。方法：寰枢椎不稳14例,男10例,女4例;年龄17～62岁,平均38.6岁。均实施后路复位,Magerl法经关节螺钉内固定和自体髂骨植骨。结果：14例患者共植入经关节螺钉28枚。所有患者获随访,时间9～35个月,平均16个月,术后JOA评分13.8～15.8分,平均（14.50±0.66）分。改善率平均（76.12±4.94）%。术后无椎动脉和脊髓损伤发生,植骨全部融合。结论：Magerl法固定是治疗寰枢椎不稳的良好方法之一,无须加用结构性植骨和辅助内固定,自体颗粒状松质骨植骨即可实现有效的骨性融合。