| Anterior cervical discectomy (ACD) and arthrodesis procedures is the major surgical intervention at present that is commonly performed for radiculopathy and spondylotic myelopathy. But the incidence of adjacent level intervertebral disc pathology secondary to anterior cervical fusion with allograft (ACF), by changing the pressures on zygapophyseal joints and the motional mechanics between segments, has been well documented in clinical and laboratory settings. Recent developments in the technology of artificial disc replacements (ADR) preserving normal physiological operative segment motion should, in theory, decrease the incidence of pathology at the "transition zones" by preserving the adjacent segment kinematics and intradiscal pressures. However, further clinical and laboratory research is needed to prove its mechanical property.The zygapophyseal joints bear different types of loads such as compression, traction, shearing and torsion. The bilateral zygapophyseal joints and the cervical disc contribute jointly the stability to cervical spine. The adjacent level degeneration is closely related to its biomechanical property and is one of the most important values used in evaluating the outcomes of cervical surgical interventions. Therefore, biomechanical research on zygapophyseal joints has great significance. So far, only a few reports can be seen which indicate cervical biomechanical change caused by ADR, and no experiment and clinical study have been undertaken on the affects versus ACF on inferior segment zygapophyseal joints.The current study was undertaken to investigate inferior cervical zygapophyseal joints from the following three aspects: (1) observing and measuring the range reference of inclination angles (angulations in the transverse plane) of zygapophyseal joints and the changes in line with different ages; (2) exploring the affect arising from ACD, ACF and ADR at C5～C6 cadaveric cervical specimens under various loadings on...
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