The in vitro study was to quantitively determine the movements of each of the cervical intervertebral joints(C2-C6) of normal structure and those following expansive open-door laminoplasty(EODL).Seven fresh young cadaveric specimens of whole cervical spine(Occipital bone to C7) were used in the determination of the movements in flexion,extension,left and right lateral bending.Pure moments with a maximum of 1.5 N.m were incrementally applied and the movements of bones were recorded by photography.Each moment was applied individually in three load/unload cycles.Parameters of neutral zone.elastic zone and range of motion were computed The difference in segmental motions were of no significant(P>0.05) when the motions of each segment from C2 to C6 in the intact cervical spine were compared with those of the same segment following EODL at C3-5 or C2-5.Worsened instability was unlikely to be seen in the middle/lower cervical spine following EODL.