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Effect of multilevel lumbar disc arthroplasty on the operative- and adjacent-level kinematics and intradiscal pressures: an in vitro human cadaveric assessment

2008; Elsevier BV; Volume: 8; Issue: 6 Linguagem: Inglês

10.1016/j.spinee.2007.10.034

1878-1632

Anton E. Dmitriev, Norman W. Gill, Timothy R. Kuklo, Michael K. Rosner,

Spinal Fractures and Fixation Techniques

With lumbar arthroplasty gaining popularity, limited data are available highlighting changes in adjacent-level mechanics after multilevel procedures.Compare operative- and adjacent-segment range of motion (ROM) and intradiscal pressures (IDPs) after two-level arthroplasty versus circumferential arthrodesis.Cadaveric biomechanical study.Ten human cadaveric lumbar spines were used in this investigation. Biomechanical testing was performed according to a hybrid testing protocol using an unconstrained spine simulator under axial rotation (AR), flexion extension (FE), and lateral-bending (LB) loading. Specimens were tested in the following order: 1) Intact, 2) L3-L5 total disc replacement (TDR), 3) L3-L5 anterior interbody cages+pedicle screws. IDP was recorded at proximal and distal adjacent levels and normalized to controls (%intact). Full ROM was monitored at the operative and adjacent levels and reported in degrees.Kinematics assessment revealed L3-L5 ROM reduction after both reconstructions versus intact controls (p < .05). However, global quality of segmental motion distributed over L2-S1 was preserved in the arthroplasty group but was significantly altered after circumferential fixation. Furthermore, adjacent-level ROM was increased for the arthrodesis group under LB at both segments and during AR at L2-L3 relative to controls (p < .05). FE did not reveal any intergroup statistical differences. Nonetheless, after arthrodesis IDPs were increased proximally under all three loading modalities, whereas distally a significant IDP rise was noted during AR and LB (p < .05). No statistical differences in either biomechanical parameter were recorded at the adjacent levels between intact control and TDR groups.Our results indicate no significant adjacent-level biomechanical changes between arthroplasty and control groups. In contrast, significant alterations in ROM and IDP were recorded both proximally (ROM=LB & AR; IDP=AR, FE, LB) and distally (ROM=LB; IDP=AR & LB) after circumferential arthrodesis. Therefore, two-level lumbar arthroplasty maintains a more favorable biomechanical environment at the adjacent segments compared with the conventional transpedicular fixation technique. This, in turn, may have a positive effect on the rate of the transition syndrome postoperatively.