1、 Anatomy Definition Biomechanics Embryology and development Manifestations Diagnosis and Treatment Prognosis 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。Atlanto-Axial Dislocation
2、 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 枕颈区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。The wide range of movements possible at this region makes it vulnerable to
3、injuryand instability.The complex embryological development of this region also makes it susceptible to a myriad of osseous and soft tissue anomalies.韧带：十字韧带功能不全 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。胚胎早期，由中胚叶
4、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，颅底骨（含上项线以下的枕骨）由软骨内化骨。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
5、 寰椎侧块及后弓上部齿状突：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。枕骨枕骨-寰椎先天性融合：寰椎先天性融合：颅底凹陷：颅底凹陷：齿状突发育异常：齿状突发育异常：kilpper-Feil综合征：综合征：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。颅底凹陷
6、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。齿状突游离小骨齿状突发育不良齿状突缺如又称短颈畸形，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。pyramidal signs(weakness and spasticity)appearence short neck,low hairline,facial asymmetry neck movement restriction and torticollis The history of transient unconsciousness or sud
7、den neurological deterioration following minor traumaMRI helps to assess soft tissue anomalies,syringomyelia,the extent of cervicomedullary compression and cord changes.3D-CT assessment of the bony configuration of the craniovertebral junction extends between the posterior pole of the hard palate an
8、d the opisthion(posterior margin of the foramen magnum)a line along the clivus and extrapolatingit inferiorly into the upper cervical spinalcanalVentral spinal cord compression may occur when the angle is less than 150 distance between the anterior arch of the atlas and the odontoid is greater than
9、3 mm in adults and 4.5 mm in children.Traumatic AADSpontaneous 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线侧位片寰椎前脱位（ADI间隙5mm），而齿状突完整。3.齿状突骨折。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。Preoperative managem
10、ent Anesthetic considerations Anterior decompression Posterior stabilization techniques 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。During intubation,any sudden movements of the neck,
11、especially flexion,should be strictly avoided.cervical collar protected Initially the patient is anesthetised using a short acting anesthetic.recovery of the respiratory functions determines that no cord injury has occurred during these procedures.If the deformity is irreducible,with or without basi
12、lar invagination,posterior fusion is preceded by ventral decompression.transpalatal,transpharyngeal route the anterior arch of the atlas and the lower portion of clivus,the odontoid and the C2 body-exposing the duraTransoccipitocervical posterolasteral approachapproach An adequate vertical decompres
13、sion during the transoral decompression is ensured by excising the part of C2 above the Wackenheims clival canal line projected into the cervical canal.Atlantoaxial fusion Occipitocervical fusionAtlantoaxial fusion（C1-C2 fusion）Transarticular screw fixationC1 lateral mass fixationmodified Brooks type fusionautologous rib grafts(a)C2 pars interarticularis screw(b)C2 pedicle screw fixation(c)C2 Translaminar Screw FixationOccipitocervical fusion（C1-C2 fusion or fusion extended C3-C4）Occipitocervical rib graftsRod and wire(contoured loop)fixationRod and screw fixationLateral radiograph
