Lumbar and cervical viscoelastic disc replacement: Concepts and current experience

Abstract

The ideal lumbar and cervical discs should provide six degrees of freedom and tri-planar (three-dimensional) motion. Although all artificial discs are intended to achieve the same goals, there is considerable heterogeneity in the design of lumbar and cervical implants. The "second generation total disc replacements" are non-articulating viscoelastic implants aiming at the reconstruction of physiologic levels of shock absorption and flexural stiffness. This review aims to give an overview of the available implants detailing the concepts and the functional results experimentally and clinically. These monobloc prostheses raise new challenges concerning the choice of materials for the constitution of the viscoelastic cushion, the connection between the components of the internal structure and the metal endplates and even the bone anchoring mode. New objectives concerning the quality of movement and mobility control must be defined.

Keywords: Cervical disc replacement; Cervical spine; Disc arthroplasty; Lumbar disc replacement; Lumbar spine; Total disc replacement; Viscoelastic.

Figure 1

Freedom lumbar disc.

Figure 2

M6-L lumbar disc.

Figure 3

LP ESP lumbar disc.

Figure 4

Freedom cervical disc.

Figure 5

M6-C cervical disc.

Figure 6

CP-ESP cervical disc.

Figure 7

Rhine cervical disc.

Figure 8

L4L5 LP ESP lumbar disc migration. Insufficient primary fixation and early anterior migration. Combined L5S1 ALIF. The ESP implant was repositioned by impaction during revision surgery. The surgeon used small screws as an anterior stop to stabilize the implant until effective bone growth and secondary fixation.

Figure 9

M6-L lumbar disc failure. Rupture of the ultrahigh-molecular weight polyethylene fibers construct and the peripheral polymer sheath. Nucleus expulsion and direct endplates contact with local metallosis.