TY - JOUR
T1 - Comparison of cervical spine biomechanics after fixed- and mobile-core artificial sisc replacement
T2 - A finite element analysis
AU - Lee, Sang Hun
AU - Im, Yang Jin
AU - Kim, Ki Tack
AU - Kim, Yoon Hyuk
AU - Park, Won Man
AU - Kim, Kyungsoo
PY - 2011/4/20
Y1 - 2011/4/20
N2 - Study Design.: A biomechanical comparison between the intact C2-C7 segments and the C5-C6 segments implanted with two different constrained types (fixed and mobile core) of artificial disc replacement (ADR) using a three-dimensional nonlinear finite element (FE) model. OBJECTIVE.: To analyze the biomechanical changes in subaxial cervical spine after ADR and the differences between fixed- and mobile-core prostheses. Summary of Background Data.: Few studies have investigated the changes in kinematics after cervical ADR, particularly in relation to the influence of constrain types. Methods.: A FE model of intact C2-C7 segments was developed and validated. Fixed-core (Prodisc-C, Synthes) and mobile-core (Mobi-C, LDR Spine) artificial disc prostheses were integrated at the C5-C6 segment into the validated FE model. All models were subjected to a follower load of 50 N and a moment of 1 Nm in flexion-extension, lateral bending, and axial torsion. The range of segmental motion (ROM), facet joint force, tension on major ligaments, and stress on the polyethylene (PE) cores were analyzed. Results.: The ROM in the intact segments after ADR was not significantly different from those of the normal cervical spine model. The ROM in the implanted segment (C5-C6) increased during flexion (19% for fixed and 33% for mobile core), extension (48% for fixed and 56% for mobile core), lateral bending (28% for fixed and 35% for mobile core) and axial torsion (45% for fixed and 105% for mobile core). The facet joint force increased by 210% in both fixed and mobile core models during extension and the tension increased (range, 66%-166%) in all ligaments during flexion. The peak stress on a PE core was greater than the yield stress (51 MPa for fixed and 36 MPa for mobile core). Conclusion.: The results of our study presented an increase in ROM, facet joint force, and ligament tension at the ADR segments. The mobile-core model showed a higher increase in segmental motion, facet force, and ligament tension, but lower stress on the PE core than the fixed-core model.
AB - Study Design.: A biomechanical comparison between the intact C2-C7 segments and the C5-C6 segments implanted with two different constrained types (fixed and mobile core) of artificial disc replacement (ADR) using a three-dimensional nonlinear finite element (FE) model. OBJECTIVE.: To analyze the biomechanical changes in subaxial cervical spine after ADR and the differences between fixed- and mobile-core prostheses. Summary of Background Data.: Few studies have investigated the changes in kinematics after cervical ADR, particularly in relation to the influence of constrain types. Methods.: A FE model of intact C2-C7 segments was developed and validated. Fixed-core (Prodisc-C, Synthes) and mobile-core (Mobi-C, LDR Spine) artificial disc prostheses were integrated at the C5-C6 segment into the validated FE model. All models were subjected to a follower load of 50 N and a moment of 1 Nm in flexion-extension, lateral bending, and axial torsion. The range of segmental motion (ROM), facet joint force, tension on major ligaments, and stress on the polyethylene (PE) cores were analyzed. Results.: The ROM in the intact segments after ADR was not significantly different from those of the normal cervical spine model. The ROM in the implanted segment (C5-C6) increased during flexion (19% for fixed and 33% for mobile core), extension (48% for fixed and 56% for mobile core), lateral bending (28% for fixed and 35% for mobile core) and axial torsion (45% for fixed and 105% for mobile core). The facet joint force increased by 210% in both fixed and mobile core models during extension and the tension increased (range, 66%-166%) in all ligaments during flexion. The peak stress on a PE core was greater than the yield stress (51 MPa for fixed and 36 MPa for mobile core). Conclusion.: The results of our study presented an increase in ROM, facet joint force, and ligament tension at the ADR segments. The mobile-core model showed a higher increase in segmental motion, facet force, and ligament tension, but lower stress on the PE core than the fixed-core model.
KW - biomechanics
KW - cervical artificial disc replacement
KW - finite element analysis
KW - fixed core
KW - mobile core
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U2 - 10.1097/BRS.0b013e3181f5cb87
DO - 10.1097/BRS.0b013e3181f5cb87
M3 - Article
C2 - 21245792
AN - SCOPUS:79955056994
SN - 0362-2436
VL - 36
SP - 700
EP - 708
JO - Spine
JF - Spine
IS - 9
ER -