1、Congenital Atlanto-Axial Dislocation,Anatomy Definition Biomechanics Embryology and development Manifestations Diagnosis and differential diagnosis Treatment Prognosis,Anatomy,Atlanto-Axial instability由于齿状突的完整性缺失，或寰枢椎之间的连接松弛或断裂，当患者曲颈时寰椎便前移，伸颈时寰椎复位或继续后后移，脊髓在寰枢椎间反复受压到刺激出现脊髓病症状。病情较轻的不稳在寰枢椎中立位时解剖结构位置基本正
2、常，在过伸及过屈动力位片上方可表现出来即动态不稳。寰齿前间距：3mm为寰枢椎不稳。,flexion-extension (FE) radiographs,Atlanto-Axial Dislocation当寰椎向前或向后移位后，寰枢椎之间的连接组织在移位后的位置上仍保持相当的强度，使寰椎在移位后的位置上稳定，病人颈椎的伸曲动作不能改变寰枢椎的相对位置。脱位后脊髓往往受到枢椎椎体后上缘的静态压迫。寰齿前间距：5mm为寰枢椎脱位,Definition,枕颈区先天性畸形为主所致的寰枢关节脱位称为先天性畸形脱位，其症状常在少年后或成年发生，并与后天劳损及外伤相关。 枕颈区又称枕椎连接部，指环绕枕骨大孔
3、区域和上二颈椎，此处骨和韧带呈漏斗状，包绕延髓、小脑下部及脊髓起始部。,导致AAD容易发病的两大原因,The wide range of movements possible at this region makes it vulnerable to injury and instability.The complex embryological development of this region also makes it susceptible to a myriad of osseous and soft tissue anomalies.,Biomechanics,韧带：十字韧带功能
4、不全 移位保持在5-6mm十字+翼状韧带功能不全 大于5-6mm脱位横韧带是寰椎最重要的稳定因素，损伤时会导致严重的寰枢椎不稳。超过八岁齿状突前后移位必须在3mm以内肌肉：旋转颈部时，肌肉在体内起夹持作用肌肉运动产生的“互锁加固”保持颈椎旋转过程中的排列。,Embryology and development of CVJ,胚胎早期，由中胚叶分出生骨节，生骨节向中线移动包围脊索形成原始脊椎。约在发育的第5-6周，原始脊椎的生骨节开始再分裂，每一节分裂为头、尾两半，头侧半染色浅，尾侧半染色深。然后各原始脊椎的尾侧半与相邻临下一个头侧半结合形成定型的脊椎，而两分裂处形成椎间盘。颅顶骨由膜内化骨，颅
5、底骨（含上项线以下的枕骨）由软骨内化骨。,Resegmentation of somites to form sclerotomes and changes of sclerotomal primordia to mature vertebral parts,Scl-A:轴向生骨节 Scl-L：侧生骨节 IBM:椎间域边界间质 Ad:轴生骨节致密区（深染） Al：轴生骨节疏松区（淡染） Ld：侧生骨节致密区 Ll：侧生骨节疏松区 P:椎弓根 NR：神经根 NA：神经弓 NC：脊索残留,间椎体 斜坡前结节第四枕生骨节 腹侧 枕骨大孔U行前缘、枕髁及枕髁中线椎弓 （前寰椎） 尾侧 寰椎侧块及后弓上
6、部齿状突：前寰椎、第一、二脊椎生骨节构成,寰椎椎体是第一脊椎生骨节形成，发生分离形成齿状突。寰椎前弓来源于生骨节腹侧的致密间质。寰椎未发育出椎体，其椎体的原基则变成齿状突并与枢椎椎体融合。第一脊椎生骨节的椎弓形成寰椎椎弓的后下部分。齿状突顶端另有一骨化中心，不衡定，来源于前寰椎。可永久与齿状突分离形成游离小骨。,Etiology and pathogenesis,枕骨-寰椎先天性融合：颅底凹陷：齿状突发育异常：kilpper-Feil综合征：,枕骨-寰椎先天性融合,缺乏寰枕关节，致使寰枢关节活动加大，累积性劳损将使寰枢之间的韧带及关节囊松弛，从而发生寰枢关节的不稳，或在轻微外力后进行性加重。,
7、颅底凹陷,颅底凹陷纵然有寰枢关节的存在，但是其活动范围会受到畸形骨质的限制，同时部分患者合并寰椎枕骨化。,齿状突发育不全,齿状突游离小骨,齿状突发育不良,齿状突缺如,Killipper-Feil综合征,又称短颈畸形，系指两个或两个以上的颈椎融合。枢椎和其下相连的几个颈椎发生先天性融合伴有斜颈畸形，寰枢关节负荷增大。,Manifestations,pyramidal signs (weakness and spasticity) appearenceshort neck ,low hairline ,facial asymmetry neck movement restriction and t
8、orticollisThe history of transient unconsciousness orsudden neurological deterioration following minor trauma,Imageology,MRIhelps to assess soft tissue anomalies, syringomyelia, the extent of cervicomedullary compression and cord changes.3D-CTassessment of the bony configuration of the craniovertebr
9、al junction,Chamberlain line,extends between the posterior pole of the hard palate and the opisthion (posterior margin of the foramen magnum),Wackenhein clivus baseline,a line along the clivus and extrapolating it inferiorly into the upper cervical spinal canalVentral spinal cord compression may occ
10、ur when the angle is less than 150,Diagnosis,distance between the anterior arch of the atlas and the odontoid is greater than 3 mm in adults and 4.5 mm in children.,Differential Diagnosis,Traumatic AADSpontaneous AAD,Traumatic AAD 创伤引起的寰枢椎不稳或脱位比较常见，主要有以下几种类型： 1.寰椎椎弓骨折（Jefferson骨折）。 2.寰椎横韧带断裂X线侧位片寰椎前
11、脱位（ADI间隙5mm），而齿状突完整。 3.齿状突骨折。,Spontaneous AAD,非特异性炎症 颈部感染。如扁桃体炎、中耳炎、咽炎等均可致咽后壁淋巴结炎，从而使临近的寰枢关节产生反应性关节炎，引起关节积液、横韧带松弛。,类风湿关节炎 类风湿性关节炎最常见，炎症造成的齿状突周围骨、韧带结构的破坏在寰枢脱位的发生中起很大作用。,Treatment,Preoperative managementAnesthetic considerationsAnterior decompressionPosterior stabilization techniques,Preoperative mana
12、gement,Clinotherapy Cervical collar枕颈区先天性畸形患者发生颈区疼痛，过伸过曲照片提示寰枢关节不稳，均应立刻给予颈托保护。 Skull traction or cervical traction颅骨牵引复位后均应继之以融合手术，以保护脊髓。因为韧带结构的陈旧性损伤不可能完整修复而重建寰枢间的稳定性。,Anesthetic considerations,During intubation, any sudden movements of the neck, especially flexion, should be strictly avoided. cervi
13、cal collar protected Initially the patient is anesthetised using a short acting anesthetic.recovery of the respiratory functionsdetermines that no cord injury has occurred during these procedures.,Anterior decompression,If the deformity is irreducible, with or without basilar invagination, posterior
14、 fusion is preceded by ventral decompression. transpalatal, transpharyngeal routethe anterior arch of the atlas and the lower portion of clivus, the odontoid and the C2 body-exposing the dura,Transoccipitocervical posterolasteral approach,Transoral approach,Extent of excision 齿状突的切除范围,An adequate ve
15、rtical decompression during the transoral decompression is ensured by excising the part of C2 above the Wackenheims clival canal line projected into the cervical canal.,Posterior stabilization techniques,Atlantoaxial fusion,Occipitocervical fusion,Atlantoaxial fusion（C1-C2 fusion）,Transarticular screw fixation,C1 lateral mass fixation,modified Brooks type fusion,autologous rib grafts,Occipitocervical fusion（C1-C2 fusion or fusion extended C3-C4 ）,Occipitocervical rib grafts,Rod and wire (contoured loop) fixation,Rod and screw fixation,Lateral radiograph,术中复位技术 Reduction Technique,
