Anatomical And Biomechanical Study For Design Of Artificial Atlanto-Odontoid Joint

Dislocation and instablility of atlanto-axial joint is common in spinal surgery. The present purpose of surgical therapy are decompression of the spinal cord and reposition and stabilization of the spine. Accordingly the modus of operation can be distributed to two groups such as decompression and fusiOn. Simple decompression cannot correct or exacerbate the instablility of atlanto-axial joint. Fusion can provide stabilization for atlanto-axial joint, but it restricts the movement between atlas and axis and induces degeneration and instablility of unfused cervical spine. Present study intends to design artificial atlanto-odontoid joint, and it is expected to apply to treat dislocation and instablility of atlanto-axial joint in order to restore stability as well as reserve the function of movement of atlanto-axial joint. Part I Anatomical study for design and installation of artificial atlanto-odontoid joint (1)Anatomical measurement of atlas and axis Eighty sets of adult dry atlas and axis spencemens and seventy sets of adult plain film of cervical spine were measured. The results manifested that the design of artificial atlanto-odontoid joint is feasible on morphology and the parameters of its components are in certain ranges. (2)Applied anatomy of ventrolateral approach of cervical spine Six (twelve sides) embalmed cadavers and four (eight sides) fresh cadavers were dissected through ventrolateral approach of cervical spine, and structures of various layers were surveied for ascertainment the exposed range of operation and quantitative positional relationship among some important structures. The results manifested that through ventrolateral approach the artificial odontoid could be installed hut anterior decompression should be difficult and artificial anterior arch of atlas could not be installed. (3)Applied anatomy of trans oral approach to the upper cervical spine -3- Five fresh specimens of cadaver cephalo-cervix were operated through transoral approach, and the exposed range of operation and some damageable structures were surveied. The results manifested that through transoral approach anterior decompression could be operated and the artificial anterior arch of atlas could be installed, meanwhile specialized instruments and conditions must be provided. Part II The structure design and manufacture of artificial atlanto-odontoid joint The demand in design of artificial atlanto-odontoid joint refered to other artificial joints and the configuration imitated to the atlanto-odontoid joint of normal person. All the components were made of titanium alloy and it belong to metal-to-metal artificial joint. A set of artificial atlanto-odontoid joint consisted of an artificial odontoid which was fixed in the axial centrum and an artificial anterior arch of atlas which was fixed on the two lateromassa of the atlas. The two components articulated each other. Part III The biomechanics of the replacement with artificial atlanto-odontoid joint Eighteen fresh occipital-cervix specimens (C0-C3) were obtained from young male cadavers died in acute hematorrhea. Twelve specimens (C0-C3) were used in measurement of three-dimensional motion. Six specimens (Cl -C2) were used in measurement of stiffness. Each specimen was...