Atlantoaxial joint distraction for treatment of basilar invagination secondary to rheumatoid arthritis

We present our experience of treating two cases of rheumatoid arthritis involving the craniovertebral junction and having marked basilar invagination by an alternative treatment method. In both the cases, the facets were osteoporotic and were not suitable for screw implantation. The patients were 66 and 72 years of age and both patients were females. Both the patients presented with complaints of progressively increasing spastic quadriparesis. Surgery involved attempts to reduce the basilar invagination and restore the height of the 'collapsed' lateral mass by manual distraction of the facets of the atlas and axis and forced impaction of titanium spacers in the joint in addition to bone graft harvested from the iliac crest. The procedure also provided stabilization of the region. No other fixation procedure involving wires, screws, plate and rods was carried out simultaneously. Following surgery both the patients showed symptomatic improvement and partial restoration of craniovertebral alignments. Follow-up is of 2 and 24 months. Distraction of the facets of atlas and axis and impaction of metal implant and bone graft in the facet joint can assist in reduction of basilar invagination and fixation of the region in selected cases of rheumatoid arthritis involving the craniovertebral junction.     

Rigid variety occiput/C1–C2–C3 internal fixation in pediatric population

Purpose

The purpose of this study was to review our experience of rigid internal fixation of craniovertebral junction in pediatric population. A new technique of reduction of basilar invagination with atlantoaxial dislocation is described. To the best of our knowledge and available scientific literature, this technique has not yet been described in younger patients.

Methods

We have managed 27 children by rigid variety of occiput/C1–C2–C3 internal fixation of various craniovertebral junction pathologies. All patients were subjected to thin cuts of computed tomography with 3D reconstruction for selecting appropriate rigid construct. Eight children had occiput-C2, 3 had occiput-C2–C3, and 16 had C1-C2 hardware constuct. One patient of C1–C2-plate fixation had section of C2 nerve root ganglia. Basilar invagination with atlantoaxial dislocation was reduced by new distraction/compression techniques.

Results

Improvement in clinical features and correction of deformity with solid hardware construct were seen in all patients. Follow-up period ranged from 5–72 months. One patient was lost to follow-up, and one case died of compression of vertebral artery at C1 lateral mass. Patients of myelopathy had recovery rate of 90.9 %. Hardware failure was seen in one patient, and wound infection was observed in two cases.

Conclusions

Rigid variety of occiput/C1–C2 internal fixation is a safe and effective method in the management of variety of craniovertebral pathologies in pediatric population. This new technique of reduction of basilar invagination with atlantoaxilal dislocation from posterior approach may alleviate the need of high morbity associated with surgical procedure like transoral odontoidectomy in younger patients.     

寰枕融合畸形患者寰枢侧块关节形态变化与寰枢椎脱位的三维特征

目的 分析寰枕融合畸形伴寰枢椎脱位时侧块关节的形态学变化与脱位的三维特征. 方法 寰枕融合畸形伴寰枢椎脱位患者36例行螺旋CT扫描后.数据以DICOM格式传送至三维可视化工作站.重建颅颈交界区三维模型,按照骨性畸形、寰齿关节、侧块关节的次序观察骨性畸形及寰枢椎脱位的三维特征. 结果 寰枢侧块关节呈关节滑脱者57侧(79%)、关节整体变形前倾者61侧(85%)和关节面分离者11侧(15%).对照两侧对称或不对称侧块关节的形态变化与脱位时寰椎与枢椎的三维位置关系,本组寰枢椎脱位的三维分型可归纳为三种:对称N(14/36例,39%),为两侧寰枢椎侧块关节呈大致对称的关节滑脱和关节整体变形前倾;旋转型(13/36例,36%),为两侧寰枢侧块关节呈显著不对称的关节滑脱和关节整体变形前倾;分离型(9/36例,25%),为至少一侧侧块关节出现关节面的完全分离. 结论 寰枕融合畸形时先天性的关节发育异常、继发的关节变形以及韧带的疲劳拉伸等多种因素及其相互作用是寰枢椎脱位发生的根本原冈.采用三维可视化方法直观地观察和分析寰枢椎脱位及寰枢侧块关节形态,对于手术决策和内固定方案选择等具有重要价值.     

Odontoid compression of the brainstem without basilar impression-- "odontoid invagination".

We report five patients with odontoid invagination, in which the odontoid process bulges upward into the foramen magnum and compresses the brainstem without deformity of the occipital bone. Two patients had a craniovertebral abnormality associated with Chiari malformation without instability of the craniovertebral junction (stable odontoid invagination). The other three patients had dislocation of the craniovertebral junction due to iatrogenic destruction of the occipital condyle, rheumatoid arthritis or an anomaly of C2 (unstable odontoid invagination). Patients with stable odontoid invagination underwent a transoral odontoidectomy followed by occipitocervical fixation. Those with unstable odontoid invagination underwent cervical traction followed by posterior fixation in reducible cases, while in irreducible cases odontoidectomy with subsequent occipitocervical fixation was performed. Decompression of the neuraxis together with symptomatic improvement was achieved in all patients and none became unstable or developed new symptoms during follow-up ranging from 3 to 15 years.     

Atlantoaxial joint distraction as a treatment for basilar invagination: a report of an experience with 11 cases

Objective: A novel method of treatment of basilar invagination that involves distraction of the atlantoaxial joint using specially designed spiked spacers is described. Bone graft that is additionally placed within the appropriately prepared atlantoaxial joint and posterior to the arch of atlas and lamina of C2 provides bony fusion. Materials and Methods: Between December 2002 and April 2007, 11 patients underwent the discussed method of fixation at the Department of Neurosurgery, King Edward Memorial Hospital in Mumbai, India. All 11 patients had "congenital" basilar invagination and the symptoms were progressive in nature. Results: The mean follow-up period was 21 months (range 8-40 months). Neurological improvement and successful distraction with atlantoaxial stabilization and ultimate bone fusion was achieved in all the patients and was documented with dynamic radiography. There were no neurological, vascular, or infective complications. Conclusions: We conclude that the described method of atlantoaxial joint distraction and fixation provides an alternative treatment strategy for cases with basilar invagination. "Joint distraction" as a stand-alone method could provide reduction of basilar invagination and firm stabilization in such cases.     

Vertical atlantoaxial dislocation as a cause of failure of midline fixation

We report an 11-year-old girl who had previously undergone an operation for basilar invagination involving a foramen magnum decompression and midline wire fixation. After improving initially, her neurological condition worsened again. Repeated investigations showed a firm midline craniovertebral fixation and bone fusion. However, she was found to have a vertical mobile and reducible atlantoaxial dislocation. Treatment of the vertical dislocation by lateral mass fixation resulted in lasting relief from her symptoms. Vertical instability at the atlantoaxial joints needs to be identified and appropriately treated as it may be a cause of failure of midline fixation.     

合并寰枢椎脱位的复杂颅颈交界区畸形后路减压复位内固定术疗效初步观察

目的 总结合并寰枢椎脱位的复杂颅颈交界区畸形经后路减压复位内固定术的临床经验.方法 回顾分析18 例合并寰枢椎脱位的复杂颅颈交界区畸形患者(先天性寰枢椎脱位15 例、经口腔入路齿状突磨除术后症状加重致枕颈失稳1 例、外伤所致2 例)的临床资料.施行经后路减压复位钉棒内固定术,术中行体感诱发电位及肌电图监测,根据日本骨科协会(JOA)17 分评分系统和影像学改善程度评价手术疗效.结果 术后影像学检查显示,18 例中16 例钉棒内固定系统和寰枢椎复位良好,1 例复位不良;骨性融合良好16 例,欠佳1 例.术后临床表现均不同程度好转,1 例突发呼吸骤停死亡.术后平均随访6.62 个月(3 ~ 28 个月),JOA 平均评分为11.62 ± 3.23,与手术前评分(7.51 ± 3.82)相比,差异具有统计学意义(t = - 5.476,P = 0.004).结论 经后路减压、复位、钉棒内固定术治疗合并寰枢椎脱位的颅颈交界区畸形临床疗效良好,能够减少患者痛苦、避免再次手术,值得临床推广应用.     

High cervical C3-4 'disc' compression associated with basilar invagination

A 20-year-old male had torticollis and short neck since birth. He presented with symptom of progressive quadriparesis over a two-year period. Investigations revealed basilar invagination with marked rotation in the craniovertebral region and relatively large C3-4 region osteophytes. Serial MRI over two years showed persistent signal opposite C3-4 disc space suggestive of cord compression. Although the cord was humped over the odontoid process, there was no clear radiological evidence that the cord was compromised at this level. During surgery, instability was identified only at the craniovertebral region and not at the level of C3-4. Distraction of the lateral masses of atlas and axis and fixation using interarticular spacers and bone graft and direct screw implantation in the lateral mass of the atlas and pars of the axis resulted in reduction of the basilar invagination and of atlantoaxial dislocation. The patient had marked clinical recovery, despite the fact that no direct procedure was done for C3-4 disc decompression. The case suggests that C3-4 disc changes could be secondary to primary instability at the craniovertebral junction.     

寰枢关节脱位后路复位及螺钉-钛棒(板)内固定技术

目的探讨寰枢关节脱位后路复位及螺钉-钛棒(板)内固定技术的临床疗效。方法回顾性分析6例寰枢关节脱位病人的临床资料,其中先天性寰枢关节脱位5例,类风湿性关节炎所致1例;术前日本整形外科协会(JOA)评分平均(8.5±4.1)分。均行后路复位及螺钉-钛棒(板)内固定术,并根据术后JOA评分和影像学改善程度,评价手术疗效。结果术后影像学检查示:固定系统和寰枢关节复位良好5例,复位不良1例;骨性融合良好4例,欠佳2例。术后临床表现均不同程度好转,未出现严重并发症。随访1～14个月,平均2.4个月,JOA评分平均(11.8±3.5)分,与手术前比较,差异具有统计学意义(t=-5.976,P0.01)。结论后路复位及螺钉-钛棒(板)内固定技术临床疗效良好,且减少病人的痛苦和费用,有广阔应用前景。     

应用C1-2螺钉棒系统行后路复位、固定和融合治疗合并寰-枢椎脱位的颅底凹陷症

目的探讨应用C1-2螺钉棒内固定系统行后路复位、固定和融合治疗寰枢椎脱位的手术疗效。方法 2013年4月至2013年10月,对30例我科收治的合并寰枢椎脱位的颅底凹陷症患者采用寰椎侧块螺钉和枢椎椎弓根峡部螺钉(或下关节突螺钉、颈3椎弓根螺钉)棒内固定系统进行复位、固定并取髂后上嵴松质骨植骨融合。通过术后3D-CT评判复位程度,JOA评分评判临床疗效,并探讨影响手术效果的因素。结果 30例患者中26例达到完全复位,4例为部分复位。其中25例完成了3个月以上随访,CT显示植骨愈合良好,未出现植骨的吸收及内固定的松动。结论 C1-2椎弓根钉棒内固定系统对治疗合并寰枢椎脱位的颅颈交界区畸形可以获得满意的疗效,安全可行。     

Atlantoaxial dislocation in a child with generalized primary dystonia

We describe a 10-year-old boy with generalized dystonia who developed spastic quadriparesis within 1 month of dystonia onset. On neuroimaging, a craniovertebral junction anomaly with atlantoaxial dislocation and compressive myelopathy was present. We postulate that dystonia involving the neck led to atlantoaxial dislocation in this child with a craniovertebral junction anomaly.     

显微镜下经口腔复位内固定术治疗颅底凹陷合并寰枢椎脱位

目的 探讨经口腔入路松解、复位内固定术在颅底凹陷合并寰枢椎脱位治疗中的应用价值,并评价其有效性及安全性.方法 对3 例不可复性寰枢椎脱位患者实施显微镜辅助下经口腔入路松解、复位内固定术,术中以经口腔复位内固定钛板作为前方固定,自体颗粒骨植骨.采用日本骨科协会(JOA)17 分评分系统进行手术前后颈脊髓神经功能评价,MRI 及X 线判断术后寰枢间距及延髓颈髓角改善程度.结果 3 例患者手术平均时间为130 min(110、130 和150 min);平均出血量为150 ml(100、200 和150 ml).术后CT 检查显示,3 例患者内固定钛板及12 枚椎弓根钛钉固定理想、无松动迹象,颅底凹陷及寰枢关节脱位得到不同程度纠正;颈脊髓神经功能明显改善,JOA评分改善率分别为75.00%、40.00%和56.25%,平均改善率为57.08%,平均JOA 评分改善率评级为良好.其中1 例患者术后并发颅内感染,经对症治疗痊愈.结论 显微镜辅助下经口腔入路松解、复位内固定术治疗颅底凹陷合并寰枢椎脱位具有一定临床应用价值.     

后路复位内固定并颅后窝小骨窗减压治疗合并颅底凹陷、寰枢椎脱位和脊髓空洞症的ChiariⅠ型畸形

研究背景ChiariⅠ型畸形为颅颈交界区软组织畸形,可合并其他复杂骨性畸形如寰枢椎脱位、颅底凹陷、扁平颅底及寰枕融合等.对这些复杂畸形,目前尚无成熟的治疗方法.本文探讨颅后窝小骨窗减压并Ⅰ期经后路复位内固定术治疗合并颅底凹陷、寰枢椎脱位和脊髓空洞症的ChiariⅠ型畸形的临床疗效.方法 回顾分析2004 年7 月-2011 年9 月治疗的寰枢椎脱位和颅底凹陷患者临床资料,分别采用日本骨科协会(JOA)17 分评分系统和MRI 影像学数据评价颈脊髓功能和脊髓空洞改善程度.结果 根据纳入标准,共筛选14 例符合入组条件的患者,男性4 例,女性10 例;平均年龄为(31.86 ±11.36)岁.术前JOA 评分平均为13.07 ± 1.59,术后增加至15.57 ± 1.02,二者比较差异具有统计学意义(t = 9.946,P = 0.000);术前脊髓空洞大小平均为(7.05 ± 1.98)mm,术后缩小至(2.21 ± 1.91)mm,手术前后比较差异亦有统计学意义(t = 7.271,P = 0.000).手术后无一例发生并发症或死亡.结论 经后路复位内固定联合颅后窝小骨窗减压术治疗合并脊髓空洞症、寰枢椎脱位及颅底凹陷的ChiariⅠ型畸形能够显著改善患者预后、缩小脊髓空洞.     

后路复位内固定并颅后窝小骨窗减压治疗合并颅底凹陷、寰枢椎脱位和脊髓空洞症的ChiariI型畸形

研究背景ChiariI型畸形为颅颈交界区软组织畸形,可合并其他复杂骨性畸形如寰枢椎脱位、颅底凹陷、扁平颅底及寰枕融合等。对这些复杂畸形,目前尚无成熟的治疗方法。本文探讨颅后窝小骨窗减压并I期经后路复位内固定术治疗合并颅底凹陷、寰枢椎脱位和脊髓空洞症的ChiariI型畸形的临床疗效。方法回顾分析2004年7月-2011年9月治疗的寰枢椎脱位和颅底凹陷患者临床资料,分别采用日本骨科协会（JOA）17分评分系统和MRI影像学数据评价颈脊髓功能和脊髓空洞改善程度。结果根据纳入标准,共筛选14例符合入组条件的患者,男性4例,女性10例;平均年龄为（31．86±11．36）岁。术前JOA评分平均为13．07±1．59,术后增加至15．57±1．02,二者比较差异具有统计学意义（t=9．946,P=0．000）;术前脊髓空洞大小平均为（7．05±1．98）mm,术后缩小至（2．21±1．91）mm,手术前后比较差异亦有统计学意义（t=7．271,P=0．000）。手术后无一例发生并发症或死亡。结论经后路复位内固定联合颅后窝小骨窗减压术治疗合并脊髓空洞症、寰枢椎脱位及颅底凹陷的ChiariI型畸形能够显著改善患者预后、缩小脊髓空洞。     

经后路椎板内固定术治疗颅颈交界区畸形合并寰枢椎脱位

目的观察经后路椎板内固定术治疗颅颈交界区畸形合并寰枢椎脱位的临床疗效。方法对2010年4月-2011年11月诊断明确的颅颈交界区畸形合并寰枢椎脱位的12例患者进行经后路减压复位螺钉钛棒(板)系统内固定术。应用CT薄层扫描及三维CT重建术测量手术前后寰齿间距(ADI)、硬腭枕骨大孔线(CL)和斜坡枕骨大孔线(ML)上方距离,通过延髓脊髓角(CMA)评价脊髓受压程度,以日本骨科协会(JOA)17分评分系统评价颈脊髓神经功能改善程度;神经电生理学方法监测神经传导功能,同时分析经后路减压复位螺钉钛棒(板)系统内固定术治疗颅颈交界区畸形合并寰枢椎脱位的可行性。结果共随访4~20个月(平均13个月)。与手术前ADI[(4.42±2.91)mm]、CL[(10.31±3.80)mm]、ML[(3.24±2.92)mm]、CMA[(127.83±8.75)°]及JOA评分(9.75±2.59)相比,手术后ADI[(2.96±2.08)mm]、CL[(7.16±3.19)mm]、ML[(0.29±2.36)mm]减小,CMA[(134.10±8.38)°]及JOA评分(14.83±2.94)增加,治疗前后比较差异具有统计学意义(P<0.05或P<0.01)。其中,手术前神经电生理学监测波形异常的10例患者中7例术后完全恢复正常形态。术后MRI检查显示,颅颈交界区减压充分,无一例出现内固定松动或断裂;随访期间植骨获得骨性融合,未出现并发症。结论经后路椎板内固定术治疗颅颈交界区畸形合并寰枢椎脱位临床疗效满意,手术安全、可行。     

Transoral decompression for craniovertebral osseous anomalies: perioperative management dilemmas.

The surgical outcome of 74 patients, who underwent transoral decompression (TOD) for ventral irreducible craniovertebral junction anomalies between January 1989 to September 1997, was studied to evaluate the perioperative complications and problems encountered. The indications for TOD included irreducible atlantoaxial dislocation (n=24), basilar invagination (n=16), and a combination of both (n=35). Following TOD, occipitocervical stabilization using Jain's technique was carried out in 50 (67.5%) and atlantoaxial fusion using Brooks' construct in 18 (24.3%) patients. The pre- and postoperative radiology was compared to assess the adequacy of decompression and stability. The major morbidity included pharyngeal wound sepsis leading to dehiscence (20.3%) and haemorrhage (4%), valopharyngeal insufficiency (8.1%), CSF leak (6.7%) and inadequate decompression (6.7%). Neurological deterioration occurred transiently in 17 (22.9%) and was sustained in 7 (9.4%) patients. The mortality in six cases was due to operative trauma, exanguination from pharyngeal wound (one each), postoperative instability and inability to be weaned off from the ventilator (two each). Of the 47 (63.5%) patients available at follow up ranging from 3 months to 2 years, 26 (55.3%) showed improvement from their preoperative status while 14 (29.8%) demonstrated stabilization of their neurological deficits. Seven (14.9%) of them deteriorated. Though TOD is logical and effective in relieving ventral compression due to craniovertebral junction anomalies, it carries the formidable risks of instability, incomplete decompression, neurological deterioration, CSF leak, infection and palatopharyngeal dysfunction.     

Somatosensory and brainstem auditory evoked potential in congenital craniovertebral anomaly; effect of surgical management.

Clinical features and evoked potential recordings were analysed in 32 patients with congenital atlantoaxial dislocation before and after surgery. Seven patients (group 1) had atlantoaxial dislocation, while 22 patients had associated basilar invagination (group 2). In both groups, pyramidal tract signs, posterior column signs, wasting of the upper limbs, and abnormality of somatosensory evoked potentials (SSEP) were similar. Conversely, lower cranial nerve involvement and abnormal brainstem auditory evoked potentials (BAEP) were significantly more in patients with basilar invagination (p less than 0.05). All seven patients in group 1 and 17 patients in group 2 were operated upon. Clinical and electrophysiological deterioration were significant in patients with basilar invagination (group 2), following posterior fixation compared with group 1. Among the patients in group 2, who clinically deteriorated following posterior fixation, seven had transoral excision of odontoid and six of them improved both clinically and electrophysiologically. Two patients in group 2 had odontoid excision before posterior fixation, and in both the evoked potentials improved postoperatively. In group 1 the patient's BAEP remained unaffected following posterior fixation, however, in group 2, eight patients over 53% showed improvement in brainstem function following posterior fixation. This study shows the value of evoked potentials in congenital atlantoaxial dislocation, and rationalizes the surgical procedure in these patients. In patients with basilar invagination, odontoid excision is the preferred first stage procedure.     

Vertical reduction using atlantoaxial facet spacer in basilar invagination with atlantoaxial instability

Although posterior segmental fixation technique is becoming increasingly popular, surgical treatment of craniovertebral junctional disorders is still challenging because of its complex anatomy and surrounding critical neurovascular structures. Basilar invagination is major pathology of craniovertebral junction that has been a subject of clinical interest because of its various clinical presentations and difficulty of treatment. Most authors recommend a posterior occipitocervical fixation following transoral decompression or posterior decompression and occipitocervical fixation. However, both surgical modalities inadvertently sacrifice C0-1 and C1-2 joint motion. We report two cases of basilar invagination reduced by the vertical distraction between C1-2 facet joint. We reduced the C1-2 joint in an anatomical position and fused the joint with iliac bone graft and C1-2 segmental fixation using the polyaxial screws and rods C-1 lateral mass and the C-2 pedicle.     

后路枕颈固定复位减压术治疗颅底凹陷症的疗效分析

目的 探讨后路枕颈固定复位减压术治疗颅底凹陷症的效果。方法 回顾性分析2015年6月至2020年1月采用单一后路枕颈固定复位减压术治疗的70例颅底凹陷的临床资料。记录病人报告的日本骨科学会（PRO-JOA）评分，用ΔPRO-JOA判断恢复程度，ΔPRO-JOA=（术后PRO-JOA评分-术前PRO-JOA评分）/（17-术前PRO-JOA评分）×100%，其中≥60%为手术效果较好，<60%为手术效果一般。结果 70例中，A型颅底凹陷[有寰枢椎脱位，寰椎齿状突间距（ADI）≥3 mm]28例，B型颅底凹陷症（无寰枢椎脱位，ADI<3 mm）42例。70例顺利完成手术，无手术死亡病例。70例术后随访12~60个月，平均（36.2±10.3）个月。A型末次随访，24例（85.71%）手术效果较好，4例手术效果一般。B型末次随访，33例（78.57%）手术效果较好，9例手术效果一般。结论 后路固定复位减压术治疗颅底凹陷症，A型和B型都可获得良好的疗效。     

Fusions at the craniovertebral junction

INTRODUCTION: The surgical management of craniovertebral junction instability in pediatric patients has unique challenges. While the indications for internal fixation in children are similar to those of adults, the data concerning techniques, complications, and outcomes of spinal instrumentation comes from experience with adult patients. Diminutive osseous and ligamentous structures and anatomical variations associated with syndromic craniovertebral abnormalities frequently complicates the approaches and limits the use of internal fixation in children. Cervical arthrodesis in the pediatric age group has the potential for limiting growth potential and causing secondary deformity. Recent advances in image analysis have enabled preoperative planning which is critical to evaluate the size of instrumentation and its relation to the patient's anatomy. Newer techniques have recently evolved and have been incorporated in the management of pediatric patients with requirement for craniocervical stabilization. MATERIALS AND METHODS: Over 750 craniovertebral junction fusions have been reviewed in children. The indications for atlantoaxial arthrodesis were: (a) absent odontoid process, dystopic os odontoideum, absent posterior arch of C1; (b) Morquio's syndrome, Goldenhar's syndrome, Conradi's syndrome, and spondyloepiphyseal dysplasia. The acquired abnormalities of trauma, postinfectious instability, and Down's syndrome completed the indication in children. The indications for occipitocervical fusion were: (a) anterior and posterior bifid C1 arches with instability, absent occipital condyles; b) severe reducible basilar invagination, unstable dystopic os odontoideum, and unilateral atlas assimilation; (c) acquired phenomenon with traumatic occipitocervical dislocation, complex craniovertebral junction fractures of C1 and C2, after transoral craniovertebral junction decompression, cranial settling in Down's syndrome and inflammatory disease such as Grisel's syndrome. Instability was seen in children with clivus chordoma and osteoblastoma. Atlantoaxial fusions were performed mainly with interlaminar rib graft fusion and more recently with the transarticular screw fixation in the older patient. In the teenager, lateral mass screws at C1 and rod fixation were made; C2 pars interarticular screw fixation and C2 pedicle screw fixation. A C2 translaminar screw fixation is described. Occipitocervical fusions were made utilizing rib grafts below the age of 6. A contoured loop fixation was made in children above the age of 7, and recently, rod and screw fixation was also utilized. RESULTS: Abnormal cervical spine growth was not seen in children who underwent craniocervical stabilization below the age of 5. The authors have reserved rigid instrumentation for children above the age of 10 years and dependent on the anatomy.