Objective To observe the initial stability between prosthetic endplate and adjacent vertebrae after Bryan cervical artificial disc replacement .Methods Using 6 fresh human cadaver cervical specimens , from C2 to T2 .The C4 and C5 motion segments were operated with the procedure of Bryan cervical artificial disc replacement .All the specimens were tested on MTS bionix 858 servo-hydraulic material tester .Radiostereometric analysis ( RSA ) technique was used to dectect the inducible displacement and maximum total point motion ( MTPM) between the Bryan disc and adjacent verte-brae during hyperflexion and hyperextension .Results The 95%CI ( confidence interval ) of inducible displacement be-tween the cranial or caudal vertebrae and adjacent endplate during hyperflexion were 0.07-0.15 and 0.07-0.19 mm.The 95%CI of inducible displacement between the cranial or caudal vertebrae and adjacent endplate during hyperextension were 0.06-0.16 and 0.05-0.18 mm.The displacement in anterior-posterior, lateral movements and segregation and the maxi-mum total point motion between the prosthesis endplate and adjacent vertebral were less than 0.2 mm at both hyperflexion and hyperextension .The inducible displacement between the vertebrae and adjacent endplate during hyperflexion were (-0.03 ±0.04) mm on anterior-posterior, (-0.02 ±0.07) mm on segregation and (0 ±0.10) mm on lateral movement (all P>0.05).The inducible displacement between the vertebrae and adjacent endplate during hyperflexion were (0.02 ± 0.04) mm on anterior-posterior, (0.01 ±0.08) mm on segregation and (0 ±0.11) mm on lateral movement (P>0.05).There was no statistical difference of the inducible displacement of the Bryan disc and adjacent vertebrae between hyperflex -ion and hyperextension movements which were (-0.004 ±0.040) mm on anterior-posterior, (-0.006 ±0.080) mm on segregation and (-0.002 ±0.100) mm on lateral movement (P>0.05).Conclusion The inducible displacement be-tween the Bryan disc and adjacent vertebrae is in an acceptable range and Bryan cervical disc has a good initial stability .%目的：观察Bryan人工颈椎间盘置换术后假体终板与邻近椎体间的即刻稳定性。方法采集6具青年男性新鲜尸体的颈椎标本，截取C2～T2节段，于C4、C5节段行Bryan人工颈椎间盘置换术。将标本置于MTS-858 Bionix生物力学试验机上，采用放射立体照相测量分析（ RSA）技术分别测量颈椎标本过屈、过伸运动时假体终板与邻近椎体间的相对移位程度及最大移位程度（ MTPM）。结果过屈运动时假体终板与上、下方椎体相对移位程度95％CI分别为0．07～0．15、0．07～0．19 mm，过伸运动时分别为0．06～0．18、0．05～0．18 mm，假体终板与邻近椎体间在前后方、分离和侧方的相对移位程度及MTPM均为±0．2 mm。过屈运动时假体终板与邻近椎体间前后方、分离和侧方分别移位（－0．03±0．04）、（－0．02±0．07）、（0±0．10）mm，过伸运动时分别为（0．02±0．04）、（0．01±0．08）、（0±0．11）mm；各方向移位程度比较，P均＞0．05。过屈、过伸两种运动方式下，假体终板与邻近椎体间前后方、分离和侧方分别移位（－0．004±0．040）、（－0．006±0．080）、（－0．002±0．100） mm， P 均＞0．05。结论 Bryan人工颈椎间盘置换术后即刻行过屈、过伸活动时，假体终板与邻近椎体间的移位程度较小、稳定性高。
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