A novel computer-assisted drill guide template for placement of C2 laminar screws

The present method of C2 laminar screw placement relies on anatomical landmarks for screw placement. Placement of C2 laminar screws using drill template has not been described in the literature. The authors reported on their experience with placement of C2 laminar screws using a novel computer-assisted drill guide template in nine patients undergoing posterior occipito-cervical fusion. CT scan of C2 vertebrae was performed. 3D model of C2 vertebrae was reconstructed by software MIMICS 10.01. The 3D vertebral model was then exported in STL format, and opened in a workstation running software UG imageware12.0 for determining the optimal laminar screw size and orientation. A virtual navigational template was established according to the laminar anatomic trait. The physical vertebrae and navigational template were manufactured using rapid prototyping. The navigational template was sterilized and used intraoperative to assist the placement of laminar screw. Overall, 19 C2 laminar screws were placed and the accuracy of screw placement was confirmed with postoperative X-ray and CT scanning. There were not complications of related screws insertion. Average follow-up was 9 months (range 4–13 months), 77.8% of the patients exhibited improvement in their myelopathic symptoms; in 22.2% the symptoms were unchanged. Postoperative computed tomographic (CT) scanning was available for allowing the evaluation of placement of thirteen C2 laminar screws, all of which were in good position with no spinal canal violation. This study shows a patient-specific template technique that is easy to use, can simplify the surgical act and generates highly accurate C2 laminar screw placement. Advantages of this technology over traditional techniques include planning of the screw trajectory is done completely in the presurgical period as well as the ability to size the screw to the patient’s anatomy.     

快速成形个体化导航模板辅助枢椎椎板螺钉的植入

目的 观察快速成形(rapid prototyping,RP)个体化导航模板在C2椎板螺钉植入中的初步临床应用.方法 对患者行上颈椎CT连续扫描,三维重建软件Amira 3.1建立C2三维模型,以STL格式导出模型.在UG Imageware 12.0平台打开三维重建模型.利用逆向工程(reverse engineering,RE)原理寻找C2椎板螺钉的最佳进钉钉道.提取椎板的表面解剖学形态,建立与椎体后部解剖学形态一致的模板.拟合模板和椎板孔道成定位模板,将椎体和定位模板通过激光RP技术生产出实物模板,手术时利用实物导航模板与椎体的后部结构相吻合,通过导航孔进行C2椎板螺钉的定位,植入椎板螺钉.术后根据X线片和CT扫描评价椎板螺钉的位置.结果 采用RP导航模板为5例患者植入C2椎板螺钉,术后CT扫描显示椎板螺钉的位置准确,未出现相关C2椎板螺钉植入的并发症.结论 利用RE原理和RP技术生产出的导航模板具有较好的准确性,为C:椎板螺钉的置钉提供了一种新的方法 ,具有较大的应用前景.     

Laminar screw fixation of the axis

OBJECT: Laminar fixation of the axis with crossing bilateral screws has been shown to provide rigid fixation with a theoretically decreased risk of vertebral artery damage compared with C1-2 transarticular screw fixation and C-2 pedicle screw fixation. Some studies, however, have shown restricted rigidity of such screws compared with C-2 pedicle screws, and others note that anatomical variability exists within the posterior elements of the axis that may have an impact on successful placement. To elucidate the clinical impact of such screws, the authors report their experience in placing C-2 laminar screws in adult patients over a 2-year period, with emphasis on clinical outcome and technical placement. METHODS: Sixteen adult patients with cervical instability underwent posterior cervical and cervicothoracic fusion procedures at our institution with constructs involving C-2 laminar screws. Eleven patients were men and 5 were women, and they ranged in age from 28 to 84 years (mean 57 years). The reasons for fusion were degenerative disease (9 patients) and treatment of trauma (7 patients). In 14 patients (87.5%) standard translaminar screws were placed, and in 2 (12.5%) an ipsilateral trajectory was used. All patients underwent preoperative radiological evaluation of the cervical spine, including computed tomography scanning with multiplanar reconstruction to assess the posterior anatomy of C-2. Anatomical restrictions for placement of standard translaminar screws included a deeply furrowed spinous process and/or an underdeveloped midline posterior ring of the axis. In these cases, screws were placed into the corresponding lamina from the ipsilateral side, allowing bilateral screws to be oriented in a more parallel, as opposed to perpendicular, plane. All patients were followed for >2 years to record rates of fusion, instrumentation failure, and other complications. RESULTS: Thirty-two screws were placed without neurological or vascular complications. The mean follow-up duration was 27.3 months. Complications included 2 revisions, one for pseudarthrosis and the other for screw pullout, and 3 postoperative infections. CONCLUSIONS: Placement of laminar screws into the axis from the standard crossing approach or via an ipsilateral trajectory may allow a safe, effective, and durable means of including the axis in posterior cervical and cervicothoracic fusion procedures.     

Translaminar screws of the axis—an alternative technique for rigid screw fixation in upper cervical spine instability

C2 pedicle screws or transarticular atlantoaxial screws are technically demanding and carry an increased risk of vertebral artery injury. In up to 20% of cases, pedicle and transarticular screw placement is not possible due to a high-riding vertebral artery or very small C2 pedicles in addition to other anatomical variations. Translaminar screws have been reported to rigidly capture posterior elements of C2 and therefore appear to be a suitable alternative. We present our first experiences and clinical results with this new method in two neurosurgical spine centers. Twenty-seven adult patients were treated between 2007 and 2010 in two neurosurgical spine departments with C2 translaminar screw fixation for upper cervical spine instability of various origins (e.g., trauma, tumor, dens pseudarthrosis). Eight patients were men and 19 were women. Mean age was 68.9 years. In most cases, translaminar screws were used because of contraindications for pedicle or transarticular screws as a salvage technique. All patients were clinically assessed and had CT scans postoperatively to verify correct screw placement. Follow-up was performed with reexamination on an ambulatory basis. Mean follow-up was 7.6 months for all patients. In 27 patients, 52 translaminar screws were placed. There were no intraoperative complications. Postoperatively, we identified four screw malpositions using a new accuracy grading scale. One screw had to be revised because of violation of the spinal canal >4 mm. None of the patients had additional neurological deficits postoperatively, and all showed stable cervical conditions at follow-up. Two patients died due to causes not associated with the stabilization technique. The fusion rate for patients with C1/C2 fixation is 92.9%. Translaminar screws can be used at least as an additional technique for cases of upper cervical spine instability when pedicle screw placement is contraindicated or not possible. The current data suggest comparable biomechanical stability and fusion rates of translaminar screws to other well-known posterior fixation procedures. In addition, translaminar screw placement is technically less demanding and reduces the risk of vertebral artery injury.     

Clinical and radiologic outcome of laminar screw at C2 and C7 for posterior instrumentation—review of 25 cases and comparison of C2 and C7 intralaminar screw fixation

BackgroundThe aim of this study is 2-fold: to analyze a clinical case series in which we used laminar screws for cervical posterior instrumentation and to describe the difference between C2 and C7 laminar screws in terms of technique and anatomy.MethodsData were obtained from 25 patients who underwent cervical posterior fixation with intralaminar screws at C2 or C7. C2 intralaminar screw instrumentation was used for 7 patients requiring occipitocervical fixation (basilar invagination [3 patients], C1 unstable bursting fracture [1 patient], C1-C2 instability with occipital assimilation [2 patients], and dystopic os odontoideum [1 patient]), 13 patients with C1-C2 instability, 1 patient with C2-C3 subluxation, and 4 patients undergoing C7 fixation due to pseudoarthrosis or cervical instability after trauma. A total of 34 laminar screws were placed including 1 thoracic laminar screw, and the patients were assessed both clinically and radiographically.ResultsThere were no instances where a screw violated the spinal canal nor any hardware fractures noted during the follow-up period. As for perioperative complications, there were 2 cases of postoperative wound infection, 1 case of dural laceration during dissection, and 2 cases of partial dorsal laminar breach. However, there was no neurologic compromise in any of the cases. The fusion success rate was 100%.ConclusionThese preliminary results support the use of intralaminar screws for posterior instrumentation at C2 and C7.     

枢椎椎板螺钉在上颈椎后路固定术中的应用

目的探讨枢椎椎板螺钉固定术应用于上颈椎后路融合内固定术中的可行性。方法回顾性分析本院2012年1月—2014年12月在上颈椎后路融合固定术中采用枢椎椎板螺钉固定的19例患者资料,术中根据枢椎椎弓根是否存在缺如、细小等情况,选择置入双侧枢椎椎板螺钉或单侧枢椎椎板螺钉并对侧椎弓根螺钉,联合枕骨板螺钉和/或寰椎侧块螺钉。15例上颈椎畸形患者均有不同程度脊髓功能损害表现,日本骨科学会(JOA)评分为5~15分,平均11.5分。4例外伤性寰枢椎骨折患者有后颈部疼痛及活动障碍,疼痛视觉模拟量表(VAS)评分为2~7分,平均4.5分。术后复查患者影像学资料,观察内固定位置及植骨融合情况。结果所有手术顺利完成,未发生椎动脉、脊髓等损伤。术后复查CT,显示所有枢椎椎板螺钉位置良好,均未突破内侧皮质骨。随访时X线、CT示螺钉位置良好,无松动及断钉。所有患者术后12个月植骨均融合,上颈椎畸形患者神经功能均有不同程度改善,JOA评分为13~17分,平均15.3分。外伤性寰枢椎骨折患者颈部疼痛及活动障碍明显改善,VAS评分为0~2分,平均1.0分。结论枢椎椎板螺钉固定在上颈椎后路固定手术中方法简单安全、效果良好,对于无法行枢椎椎弓根螺钉固定的患者,枢椎椎板螺钉固定是一种安全有效的替代方法。     

Clinical application of C2 laminar screw technique

C2 laminar screws have become an increasingly used alternative method to C2 pedicle screw fixation. However, the outcome of this technique has not been thoroughly investigated. A total of 35 cases with upper cervical spinal instability undergoing C2 laminar screw fixation were reviewed. All cases had symptoms of atlantoaxial instability, such as craniocervical junction pain, and were fixed with the Vertex cervical internal fixation system. A total of 68 screws were placed and hybrid constructs (a C2 translaminar screw combined with a C2 pars screw) were incorporated in two patients. In this series, there were no intraoperative complications and no cases of neurological worsening or vascular injury from hardware placement. Computed tomographic scans demonstrated a partial dorsal laminar breach in ten patients. None of these resulted in neurological symptoms. None of the patients was found to have a breach of the ventral laminar cortex. All the C2 laminar screws fixations were performed successfully. There was no instability seen on the films with no evidence of hardware failure or screw loosening during the follow-up period in all patients. In conclusion, C2 laminar screw technique is straightforward and easily adopted; it can efficiently and reliably restore upper cervical stability. It is an alternative method to C2 pedicle screw fixation, especially in patients with unilateral occlusion of vertebral artery and pedicle deformity of C2.     

寰枢椎脱位后路螺钉固定方法的临床选择

目的 探讨寰枢椎脱位后路钉棒固定术中寰椎螺钉和枢椎螺钉固定方法 的临床选择.方法 对2002 年11 月至2011 年12 月广州军区广州总医院收治的228 例可复性和23 例难复性寰枢椎脱位患者,术前进行置钉可行性和复位可能性评估,针对性地选择寰椎和枢椎的后路螺钉固定方法,进行寰枢椎后路钉棒固定治疗.结果 251 例患者均行钉棒固定并获得满意复位.寰椎螺钉固定采用椎弓根螺钉403 枚、部分经椎弓根螺钉77 枚、侧块螺钉22 枚;枢椎螺钉固定采用椎弓根螺钉437 枚、椎板螺钉56 枚、侧块螺钉9 枚.术中未发生椎动脉、脊髓损伤.237 例患者获得随访,随访时间4～38 个月,平均随访时间13 个月.230 例患者获骨性融合;6例为纤维愈合,动力位片（均随访2 年以上）未见复发脱位;另1 例为假关节未融合并双侧枢椎椎弓根螺钉松动,行后路翻修手术治愈.结论 根据寰枢椎脱位的复位难易程度和个体解剖特点灵活选择寰椎和枢椎不同的后路螺钉固定方法,扩大了寰枢椎后路钉棒固定技术的适用范围,提高了手术安全性和成功率.     

组合枢椎椎板螺钉及经枢椎椎板关节突螺钉固定技术的临床应用

目的探讨组合枢椎椎板螺钉及经枢椎椎板关节突螺钉(TLFS)固定技术治疗颈椎损伤的可行性和应用价值。方法自2005年10月～2008年10月,采用枢椎椎板螺钉及经枢椎TLFS固定技术治疗颈椎损伤36例。结果本组获随访13~32个月,平均18个月。30例行自体髂骨植骨,6例行异体骨植骨,获得了良好的骨性愈合。术后CT示枢椎椎板螺钉及经枢椎TLFS位置良好,未侵犯椎管和脊髓。结论枢椎椎板螺钉及经枢椎TLFS固定技术不受C2横突孔中椎动脉的位置和C2椎弓根大小限制,避免了螺钉置入过程中损伤椎动脉的风险,所以该方法可作为传统枢椎后路螺钉固定技术的补充。     

枢椎棘突椎板螺钉固定技术及其解剖学研究

目的 明确枢椎后路棘突椎板螺钉固定的可行性和技术参数,为临床应用提供参考.方法 选取20具枢椎标本,仔细解剖以清楚地暴露椎板和棘突.以棘突基底部为进钉点,双侧平行置入棘突椎板螺钉,通过CT重建测量棘突的宽度、螺钉在横断面上的前倾角度、钉道长度及钉尖与脊髓、椎动脉距离.结果 所有螺钉均成功置入,未发现螺钉侵犯椎管、横突孔情况发生.重建CT测量发现棘突椎板螺钉在横断面的前倾角度为76.8°±10.6°;螺钉钉道平均长度为(23.1±3.2)mm,其中上位螺钉钉道长度[(22.9±3.3)mm]稍短于下位螺钉钉道长度[(23.3±3.1)mm],但差异无统计学意义(P＞0.05);螺钉钉尖与脊髓和椎动脉的距离分别为(5.3±1.6)mm和(17.4±3.7)mm.上下位螺钉前倾角度、与椎动脉和脊髓的距离数据略有不同,但差异均无统计学意义(P＞0.05).结论 枢椎棘突椎板螺钉固定具有解剖学可行性,也许可以作为枢椎后路固定的一种补充内固定方法.

Abstract：

Objectives To explore the feasibility and the technical parameters in posterior C2 spinous process laminar screw fixation, and discuss the clinic significance of C2 spinous process laminar screws. Methods Twenty cervical cadaveric spines of C2 were dissected, with care taken to expose the lamina and spinous process. After the entrance point of spinous process screw were determined, posterior C2 spinous process laminar screw implantation was performed under visual control. On the morphologic CT scan,the angle and length of the spinous process laminar screw trajectory and the distance between the tip of the screw and the spinal cord and the vertebral artery were measured. Results The C2 spinous process laminar screws were successfully placed, without impingement of the spinal cord and the vertebral artery. There were little differences between superior and inferior screws in the angle, trajectory length and the distance between the tip of the screw and the spinal cord and the vertebral artery, but without significance (P＞0.05). The placed angles of the screws were 76. 8°± 10. 6° in the axial plane. The distance between the tip of the screw and the spinal cord and the vertebral artery was (5.3+1.6) mm and (17.4 ± 3.7) mm respectively. The trajectory length was (23.1±3.2) mm. Conclusions Posterior C2 spinous process laminar screw fixation is feasible. C2 spinous process laminar screw fixation affords an alternative to standard screw placement for plate fixation and cervical stabilization.     

Bilateral atlas laminar hook combined with transarticular screw fixation for an unstable bursting atlantal fracture

Introduction  The unstable atlas burst fracture (“Jefferson fracture”) is a fracture of the anterior and posterior atlantal arch with rupture of the transverse atlantal ligament and an incongruence of the atlanto-occipital and the atlanto-axial joint facets. The posterior atlantoaxial fusion is frequently used to reconstruct the stability of atlantoaxial joint. Conventional posterior atlantoaxial fixations are associated with high rates of pseudoarthrosis and chronic atlantoaxial instability. As a modified three-point fixation the bilateral C1-2 transarticular screws combined with C1 laminar hook and bone grafts can provide best biomechanical stability, but no standard protocol has been reported for the use of this fusion technique. A retrospective review of clinical series should be conducted to evaluate the clinical outcome of bilateral atlas laminar hook combined with transarticular screw fixation for unstable bursting atlantal fracture. Materials and methods  From March 2002 to March 2006, there were total 12 cases of unstable atlantal bursting fractures, 10 males and 2 females, age ranging 18–54, with mean of 36 years old. All patients were operated on posterior atlantoaxial fusion using bilateral atlas laminar hook combined with transarticular screw fixation after atlantoaxial joint were reduced and followed up for 12–24 months. The medical records and radiographs of the 12 patients were reviewed. Each patient underwent a complete cervical radiograph series including lateral flexion-extension view and a computed topographic scan. The Frankel grades and ASIA scores were applied to assess the neurologic status. Results  In all patients, a good bony fusion of the atlanto-axial segment was achieved. All patients showed significant improvement of the neurologic defect and no instability on their follow-up plain radiographs and computerized tomography in follow-up interval. Conclusions  For the patients who suffer from the unstable bursting atlantal fracture, the nonoperative methods could carry some clinical complications including infection, nerve injury, etc. and is frequently failure, Posterior atlantoaxial fusion using bilateral atlas laminar hook combined with transarticular screw fixation is an effective treatment. Xiang Guo and Bin Ni contributed equally to the article.     

枢椎椎板螺钉治疗上颈椎不稳的临床研究

目的探讨枢椎椎板螺钉技术的临床应用和适应证。方法2004年10月至2008年12月,采用后路枢椎椎板螺钉技术治疗上颈椎不稳35例,男19例,女16例;年龄23～73岁,平均45岁。AndersonⅡ型和Ⅲ型齿突骨折19例,寰椎横韧带断裂1例,先天性游离齿突并寰枢椎不稳2例,寰椎骨折合并寰枢椎不稳7例,不典型Hangman骨折并C2-3不稳1例,C2-3创伤性不稳5例。患者均采用颈椎后路Vertex钉棒系统固定。结果35例患者共置入枢椎椎板螺钉68枚,术中无一例发生脊髓和椎动脉损伤。患者均获得随访,随访时间6个月～4年,平均25.5个月。随访时X线片均未见明显颈椎不稳、内固定失败及螺钉松动退出。11例患者螺钉穿出椎板背侧,但无症状出现。结论枢椎后路经椎板螺钉技术固定牢固,操作简单,相对安全,特别适用于C2椎弓根发育异常或骨折不能采用椎弓跟固定的患者。     

下颈椎椎弓根螺钉内固定技术在临床中的应用

目的 :探讨下颈椎椎弓根螺钉内固定技术的临床应用。方法 :对2011年9月至2013年7月行下颈椎椎弓根螺钉内固定的32例患者进行回顾性分析,男20例,女12例;年龄21~78岁,平均56.4岁。其中10例为创伤性颈髓损伤,9例为颈椎管内肿瘤,7例颈椎后纵韧带骨化症,6例多节段颈椎病。所有患者术前行X线、CT、MRI及椎动脉MRA等影像学检查,术后及随访时行X线片及CT平扫明确螺钉的位置情况。根据Lee等4级分类法评价置钉的准确性,创伤性患者行ASIA分级评价脊髓功能变化,非创伤性患者采用JOA评分评价神经功能改善情况。结果:32例患者成功置入144枚下颈椎椎弓根螺钉,术后CT显示,0级132枚,1级5枚,2级5枚,3级2枚。有12枚螺钉穿破椎弓根,其中8枚螺钉穿破椎弓根外侧皮质,2枚螺钉穿破椎弓根下侧皮质,穿破椎弓根内侧、上侧皮质螺钉各1枚。术后随访12~33个月,平均(21.0±1.5)个月,6例完全性颈髓损伤患者术后神经功能虽无恢复,但截瘫平面下降1~3个脊髓节段。4例不完全性颈髓损伤患者术后按ASIA损伤分级提高1~2级。22例非创伤性患者术后6个月JOA评分平均(15.9±0.6)分,较术前(11.5±0.8)分明显提高(P<0.01)。所有患者未发现钉棒系统松动、断裂情况。结论:下颈椎椎弓根螺钉固定能提供优秀的三维稳定性。合理选择适应证,术前充分准备以及根据椎弓根形态个体化置钉可以最大限度的降低手术风险及手术并发症,值得临床应用推广。     

下颈椎经关节螺钉联合侧块或椎弓根螺钉固定的效果

目的 探讨在下颈椎经颈后正中入路应用经关节螺钉联合侧块螺钉或椎弓根螺钉行内固定治疗的固定效果.方法 2003年2月至2007年10月,对22例患者通过后路应用经关节螺钉联合侧块螺钉或椎弓根螺钉行内固定治疗,男14例,女8例;年龄24～73岁,平均43岁.其中下颈椎创伤性骨折脱位13例,颈椎后纵韧带骨化症4例,颈椎管狭窄伴Ⅱ型齿突骨折1例,颈椎间盘突出伴椎管狭窄4例.结果 共置入经关节螺钉45枚,其中C4,5 2枚,C5,639枚,C6,74枚;共置入侧块螺钉12枚,C3、C4各6枚;共置入椎弓根螺钉41枚,其中C24枚,C32枚,C46枚,C721枚,T18枚.术中所有螺钉均成功置入,未出现椎动脉、神经根和脊髓损伤等置钉相关并发症.22例患者均获随访,随访时间10个月～3年8个月,平均17个月.植骨融合时间3～5个月,平均3.5个月.术后发现1例患者的2枚经关节螺钉松动,部分脱出.经加强颈托制动,术后4个月获得融合.结论 通过后路固定下颈椎时,采用经关节螺钉联合侧块螺钉或椎弓根螺钉固定,均可取得较好的固定效果.     

Posterior cervical spine arthrodesis incorporating C2 laminar screw fixation in the treatment of cervical spine injury

Objective: To investigate the clinical application and efficacy of an internal fixation technique incorporating C₂ laminar screws for upper cervical spine injury. Methods: Using a posterior cervical approach, incorporating C₂ laminar screw fixation and bone grafting were performed on 20 patients with cervical spine injury. There were 12 male and 8 female patients, with a mean age of 45.6 years (range, 32–71 years). All patients were evaluated by X‐ray, computed tomography (CT) and magnetic resonance imaging (MRI). Results: The patients were followed up for 11–35 months (mean, 15 months), and bony union was achieved in all patients. There were no spinal cord or vertebral artery injuries during surgery, and only two instances of vein clump injury, in both of which the bleeding was controlled successfully. Postoperative CT scans showed that all the C₂ laminar screws had been placed properly, and were not encroaching on the spinal canal. No spinal instability, evidence of hardware failure or screw loosening was found during the follow‐up period in any patient. Conclusion: Crossing C₂ laminar screw internal fixation technique is simple, and is not limited by the position of the vertebral artery in the body of C₂. The laminar screw method avoids arterial injuries and also can be used as a salvage method after previous misinsertion. As all relevant structures are directly visualized during C₂ laminar screw placement, this kind of technique may be applicable to a large number of patients.     

Transfacet screw placement for posterior fixation of C-7

OBJECT: Lateral mass screws are traditionally used to fixate the subaxial cervical spine, while pedicle screws are used in the thoracic spine. Lateral mass fixation at C-7 is challenging due to thin facets, and placing pedicle screws is difficult due to the narrow pedicles. The authors describe their clinical experience with a novel technique for transfacet screw placement for fixation at C-7. METHODS: A retrospective chart review was undertaken in all patients who underwent transfacet screw placement at C-7. The technique of screw insertion was the same for each patient. Polyaxial screws between 8- and 10-mm-long were used in each case and placed through the facet from a perpendicular orientation. Postoperative radiography and clinical follow-up were analyzed for aberrant screw placement or construct failure. RESULTS: Ten patients underwent C-7 transfacet screw placement between June 2006 and March 2007. In all but 1 patient screws were placed bilaterally, and the construct lengths ranged from C-3 to T-5. One patient with a unilateral screw had a prior facet fracture that precluded bilateral screw placement. There were no intraoperative complications or screw failures in these patients. After an average of 6 months of follow-up there were no hardware failures, and all patients showed excellent alignment. CONCLUSIONS: The authors present the first clinical demonstration of a novel technique of posterior transfacet screw placement at C-7. These results provide evidence that this technique is safe to perform and adds stability to cervicothoracic fixation.     

单侧枢椎椎板螺钉在椎动脉变异的上颈椎不稳中的临床应用

目的：探讨后路寰椎侧块螺钉联合单侧枢椎椎板螺钉＋对侧枢椎椎弓根螺钉固定、自体双皮质骨加压植骨融合术治疗上颈椎不稳伴椎动脉变异的临床疗效。方法：2008年6月至2012年12月,行后路寰椎侧块螺钉联合单侧枢椎椎板螺钉＋对侧枢椎椎弓根螺钉固定、自体双皮质骨加压植骨融合术12例,男8例,女4例,年龄16—77岁,平均47．5岁。术前患者枕颈部活动受限伴或不伴疼痛,VAS评分0-7分,平均3．50±2．71;椎动脉造影或颈椎CTA示单侧椎动脉明显狭窄。观察术中有无神经及血管损伤;术后7d内行X线和CT检查,了解内固定位置;术后随访观察有无内固定松动、断裂失败并发症、复位丢失,以及植骨融合率等。结果：12例单侧枢椎椎板螺钉固定,术中未发生神经和椎动脉损伤。患者颈部VAS评分0．92±0．90,较术前明显减轻（P=0．01）。术后x线示12例患者颈椎序列恢复良好,CT示1例枢椎椎板腹侧皮质侵犯,余位置均良好。12例患者均获得随访,时间6个月～3年;未见内固定松动、断裂和复位丢失等并发症;术后6个月12例均骨性融合。结论：后路寰椎侧块螺钉联合单侧枢椎椎板螺钉＋对侧枢椎椎弓根螺钉固定、自体双皮质骨加压植骨融合术,既避免了传统螺钉固定椎动脉损伤的同时,又克服了部分病例双侧枢椎椎板螺钉时植骨床的不足,在保证良好力学稳定的情况下,可以取得良好的骨性融合率。单侧枢椎椎板螺钉可以作为一种安全有效的补充固定措施应用于椎动脉变异的上颈椎不稳患者中。     

Posterior fixation and fusion with atlas pedicle screw system for upper cervical diseases

Objective： To evaluate the feasibility, safety and efficacy of atlas pedicle screws system fixation and fusion for the treatment of upper cervical diseases.
Methods： Twenty-three consecutive patients with upper cervical disorders requiring stabilization, including 19 cases of atlantoaxial dislocation （4 congenital odontoid disconnections, 6 old odontoid fractures, 4 fresh odontoid fractures of Aderson Ⅱ C, 3 ruptures of the C1 transverse ligament, and 2 fractures of C1）, 2 cases of C2 tumor （instability after the resection of the tumors）, and 2 giant neurilemomas of C2-C3（instability after resection of the tumors）, were treated by posterior fixation and fusion with the atlas pedicle screw system, in which the screws were inserted through the posterior arch of C1. The operative time, bleeding volume and complications were reported. All patients were immobilized without external fixation or with rigid cervical collars for 1-3 months. All patients were followed up and evaluated with radiographs and CT.
Results： In the 23 patients, 46 C1 pedicle screws, 42 C2 pedicle screws and 6 lower cervical lateral mass screws and 2 lower cervical pedicle screws were placed. The mean operative time and bleeding volume was 2.7 hours and 490 ml respectively. No intraoperative complications were directly related to surgical technique. No neurological, vascular or infective complications were encountered. All patients were followed up for 3-36 months （average 15 months）. Firm bony fusion was documented in all patients after 3-6 months. One patient with atlas fracture showed anterior occipitocervical fusion. There was no implant failure. Conclusions： Posterior fixation and fusion of the atlas pedicle screw system is feasible and safe for the treatment of upper cervical diseases, and may be applicable to a larger number of patients.     

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.     

Lamina-guided lateral mass screw placement in the sub-axial cervical spine

Lateral mass (LM) screws are commonly used in posterior instrumentation of the cervical spine because of their perceived safety over pedicle screws. A possible complication of cervical LM screw placement is vertebral artery injury or impingement. Several screw trajectories have been described to overcome the risks of neurovascular injury; however, each of these techniques relies on the surgeon’s visual estimation of the trajectory angle. As the reliability hereof is poorly investigated, alignment with a constant anatomical reference plane, such as the cervical lamina, may be advantageous. The aim of this investigation was to determine whether alignment of the LM screw trajectory parallel to the ipsilateral cervical lamina reliably avoids vertebral artery violation in the sub-axial cervical spine. 80 digital cervical spine CT were analysed (40 female, 40 male). Exclusion criteria were severe degeneration, malformations, tumour, vertebral body fractures and an age of less than 18 or greater than 80 years. Mean age of all subjects was 39.5 years (range 18–78); 399 subaxial cervical vertebrae (C3–C7) were included in the study. Measurements were performed on the axial CT view of C3–C7. A virtual screw trajectory with parallel alignment to the ipsilateral lamina was placed through the LM. Potential violation of the transverse foramen was assessed and the LM width available for screw purchase measured. There was no virtual violation of the vertebral artery of C3–C7 with lamina-guided LM screw placement. LM width available for screw purchase using this technique ranged from 5.2 to 7.4 mm. The sub-axial cervical lamina is a safe reference plane for LM screw placement. LM screws placed parallel to the ipsilateral lamina find sufficient LM width and are highly unlikely to injure the vertebral artery, even in bi-cortical placement. Placing LM screws parallel to the lamina appears favourable over conventional techniques.