LAUSR

STUDY DESIGN A Biomechanical in vitro Investigation. OBJECTIVE To evaluate the function and stability of self-designed biomimetic artificial atlanto-odontoid joint(BAAOJ) replacement on the atlantoaxial joint. SUMMARY OF BACKGROUND DATA Upper cervical fusion surgery is a common treatment for various atlantoaxial disorders, and favorable clinical outcome has been achieved. However, the fusion surgery results in loss of atlantoaxial motion as well as adjacent segments degeneration, reducing the quality of life of patients and might produce severe neurological symptoms. Non-fusion technology is expected to solve the above problems, but various designed devices have certain defects and are still in the exploratory phase. METHODS Biomechanical tests were conducted on 10 fresh human cadaveric craniocervical specimens in the following sequence:(1) intact condition, (2) after the BAAOJ arthroplasty, (3) after BAAOJ fatigue test, (4) after odontoidectomy, and (5) after anterior rigid plate fixation. Three-dimensional movements of the C1-C2 segment were evaluated to investigate the function and stability of BAAOJ arthroplasty compared with the intact condition after the BAAOJ fatigue test, odontoidectomy, and rigid plate fixation. RESULTS Comparing the BAAOJ implantation to the intact state, the ROM and neutral zone (NZ) were slightly reduced in all directions (P>0.05). Compared with the rigid plate fixation, the BAAOJ implantation significantly increased the ROM and NZ in all directions, especially in the axial rotation (P<0.05). CONCLUSION We designed a BAAOJ for correcting atlantoaxial disorders arising from atlantoaxial instability. As a non-fusion device, the most critical feature of BAAOJ replacement is the retention of flexion-extension, lateral bending, and axial rotation range of motion similar to the normal state. It can also stabilize the atlantoaxial complex, and the BAAOJ itself has a good initial stability.Level of Evidence: 4.