ABSTRACT
<p><b>OBJECTIVE</b>To evaluate stress changes of intervertebral space and adjacent intervertebral space after artificial disc replacement with angles.</p><p><b>METHODS</b>Artificial disc replacement with angles were designed according to existing data. Axial pressure, flexion/extension, lateral bending and torsion loading were applied on finite element models of normal cervical discs on C4,5 segments, C4,5 segments with 0 degrees artificial cervical discs and C4,5 segments with 10 degrees artificial cervical discs, then stress changes of C4,5 space was observed. The same loadings were applied on finite element models of normal cervical discs on C4-C6 segments, C4,5 segments with 0 degrees, C4,5 segments with 10 degrees, then stress changes of replaced segments space and adjacent segment space were observed.</p><p><b>RESULTS</b>For C4,5 segments, 80 MPa/0 degrees artificial discs and 80 MPa/10 degrees artificial discs had the similar equivalent shear stress (Se), and were both larger than that of normal discs, when lateral bending were performed, 80 MPa/0 degrees artificial discs were closed to normal discs when axial pressure and flexion/extension were carried out, while 80 MPa/10 degrees artificial discs had a larger Se than that of normal ones,when torsion loading were applied, Szx/Szy stress of 80 MPa/0 degrees and 80 MPa/10 degrees artificial discs were closed to normal ones. For C4-C6 segments, the axial pressure, flexion/extension and lateral bending of C5,6 were all lower than normal discs after C4,5 discs were replaced by 80 MPa/10 degrees artificial discs, while Szx/Szy of torsion loading were closed to normal ones.</p><p><b>CONCLUSION</b>Artificial discs with 10 degrees have less influences on stress of adjacent intervertebral space and closer to mechanical property after being implanted into intervertebral space.</p>
Subject(s)
Humans , Cervical Vertebrae , General Surgery , Stress, Mechanical , Total Disc Replacement , MethodsABSTRACT
<p><b>OBJECTIVE</b>To observe the effect of the estrogen on the mRNA expression of osteoprotegerin (OPG), osteoclast differentiation factor (ODF) and macrophage colony stimulating factor (M-CSF) in bone tissue of ovariectomized rats, and investigate the possible pathway of estrogen in preventing and treating postmenopausal osteoporosis. METHODS; Thirty healthy adult SD rats were randomly divided into sham operation group, ovariectomized group and estrogen-treated group. All rats were ovariectomized except those in the sham operation group. Bone density of the L3-L6 vertebra was detected 12 weeks after the operation. The total RNA were extracted from the femur to examine mRNA expression of OPG, ODF and M-CSF by real-time PCR.</p><p><b>RESULTS</b>Estrogen increased the bone density of the ovariectomized rat lumbar vertebra and up-regulated the expression of OPG, whereas down-regulated the expression of M-CSF and lowered ODF:OPG ratio.</p><p><b>CONCLUSION</b>The effect of estrogen in treating postmenopausal osteoporosis is closely correlated with the regulation of OPG and M-CSF expressions and ODF:OPG ratio.</p>