1. Field of the Invention
The present invention relates to a device for reconstructing cervical vertebrae after subtotal resection of cervical vertebrae body, and particularly to an artificial cervical vertebrae composite joint. The artificial cervical vertebrae composite joint is achieved by means of bionics of physiological reconstruction in three aspects of anatomy, stability and motion of cervical vertebrae by simulating normal cervical vertebrae.
2. Description of the Related Art
Clinically, subtotal resection of cervical vertebrae body mostly needs to be performed for infection, tumor, and degenerative disease of cervical vertebrae and then the resected segment of the cervical vertebrae needs to be reconstructed. Currently, reconstruction methods clinically commonly used mainly comprise two methods, that is, segmental bone graft fusion and replacement of artificial vertebral body. A method of bone graft fusion as a current standard method of clinically reconstructing cervical vertebrae after subtotal resection of cervical vertebrae body is to fill a defect segment with autograft bone issue or xenoma bone issue while adding internal fixation to reconstruct stability of the cervical vertebrae. The method achieves reconstruction of stability of the cervical vertebrae by bone fusion between the grafted bone and upper and lower cervical vertebrae bodies to eliminate pain. However, the reconstruction method is not ideal anatomical reconstruction and causes the reconstructed segment to lose movability completely and thus affects entire movement function of the cervical vertebrae. In addition, the method also results in degradation of intervertebral disk of adjacent segments due to stress concentration in the long term. There are various designs of artificial vertebral body so far, but in all of the designs, stability of cervical vertebrae is reconstructed by means of bone graft fusion, self fixation or additional internal fixation and there are the problems that movability of the segment is lost and intervertebral disk of adjacent segments degrades in the long term. Therefore, the reconstruction of the various designs is not real physiological reconstruction. All of few artificial vertebral bodies designed in consideration of motion reconstruction finally fail due to their motion mode different from physiological motion mode or bad stability. Currently, clinical non-fusion reconstruction has become development trend. Based on the reconstruction, products such as artificial hip, knee, ankle, and elbow joints and artificial intervertebral disk are produced, and are clinically largely applied to achieve quick cure, good effect, and stable clinical long-term effect. Generation of the artificial intervertebral disk undoubtedly has epochal significance for vertebral column surgery. Currently, the artificial intervertebral disk has gadually matured. Non-fusion reconstruction of a single segment of cervical vertebrae generates excellent products such as Bryandisc and Prestige. However, currently, there has not yet been a good method to solve the problem of non-fusion reconstructing after subtotal resection of cervical vertebrae. Therefore, the present applicant designed an artificial cervical vertebrae composite joint in prophase. It is manifested by primary biomechanical to research that a ball-and-socket joint of the artificial cervical vertebrae composite joint retains movability of the cervical vertebrae to a certain degree and that a new concept is provided in the way of the non-fusion reconstruction. Based on the design, the present applicant further researches normal motion mode of cervical vertebrae and concludes by synthesizing past research that motion of the cervical vertebrae is not simple rotation, but is a coupling motion of rotation and translation. The rotation is coupled with relative displacement between adjacent cervical vertebrae bodies while the adjacent cervical vertebrae bodies rotate, and the upper cervical vertebrae body has a variable center of rotation relative to the lower cervical vertebrae body. Therefore, the primary design of the artificial cervical vertebrae composite joint, that is, the ball-and-socket joint, has a fixed center of rotation, and the motion mode of the joint is a simple rotation, and greatly different from the motion mode of normal cervical vertebra.
According to document retrieval made by the present applicant, so far there is not a method capable of designing the joint in consideration of stability, movability, and particular coupling motion mode of cervical vertebrae to really achieve physiological reconstruction. Only if a particular artificial joint is designed to simulate the motion mode of the normal cervical vertebra, bionics of the reconstruction of the cervical vertebrae is really achieved.