Bionate Lumbar Disc Nucleus Prosthesis: Biomechanical Studies in Cadaveric Human Spines

Amparo Vanaclocha; Vicente Vanaclocha; Carlos M Atienza; Pablo Clavel; Pablo Jordá-Gómez; Carlos Barrios; Nieves Saiz-Sapena; Leyre Vanaclocha

doi:10.1021/acsomega.2c05294

Bionate Lumbar Disc Nucleus Prosthesis: Biomechanical Studies in Cadaveric Human Spines

ACS Omega. 2022 Dec 6;7(50):46501-46514. doi: 10.1021/acsomega.2c05294. eCollection 2022 Dec 20.

Authors

Amparo Vanaclocha¹, Vicente Vanaclocha², Carlos M Atienza¹, Pablo Clavel³, Pablo Jordá-Gómez⁴, Carlos Barrios⁵, Nieves Saiz-Sapena⁶, Leyre Vanaclocha⁷

Affiliations

¹ Biomechanical Engineer, Biomechanics Institute of Valencia, Valencia 46022, Spain.
² University of Valencia, Valencia 46010, Spain.
³ Instituto Clavel, Hospital Quironsalud Barcelona, Barcelona 08023, Spain.
⁴ Hospital General Universitario de Castellón, Castellón de la Plana 12004, Spain.
⁵ Catholic University of Valencia, Saint Vincent Martyr, Valencia 46001, Spain.
⁶ Hospital General Universitario de Valencia, Valencia 46014, Spain.
⁷ Medius Klinik, Ostfildern-Ruit Klinik für Urologie, Hedelfinger Strasse 166, Ostfildern 73760, Germany.

Abstract

Design: cadaveric spine nucleus replacement study.

Objective: determining Bionate 80A nucleus replacement biomechanics in cadaveric spines.

Methods: in cold preserved spines, with ligaments and discs intact, and no muscles, L₃-L₄, L₄-L₅, and L₅-S₁ nucleus implantation was done. Differences between customized and overdimensioned implants were compared. Flexion, extension, lateral bending, and torsion were measured in the intact spine, nucleotomy, and nucleus implantation specimens. Increasing load or bending moment was applied four times at 2, 4, 6, and 8 Nm, twice in increasing mode and twice in decreasing mode. Spine motion was recorded using stereophotogrammetry. Expulsion tests: cyclic compression of 50-550 N for 50,000 cycles, increasing the load until there was extreme flexion, implant extrusion, or anatomical structure collapse. Subsidence tests were done by increasing the compression to 6000 N load.

Results: nucleotomy increased the disc mobility, which remained unchanged for the adjacent upper level but increased for the lower adjacent one, particularly in lateral bending and torsion. Nucleus implantation, compared to nucleotomy, reduced disc mobility except in flexion-extension and torsion, but intact mobility was no longer recovered, with no effect on upper or lower adjacent segments. The overdimensioned implant, compared to the customized implant, provided equal or sometimes higher mobility. Lamina, facet joint, and annulus removal during nucleotomy caused more damaged than that restored by nucleus implantation. No implant extrusion was observed under compression loads of 925-1068 N as anatomical structures collapsed before. No subsidence or vertebral body fractures were observed under compression loads of 6697.8-6812.3 N.

Conclusions: nucleotomized disc and L₁-S₁ mobility increased moderately after cadaveric spine nucleus implantation compared to the intact status, partly due to operative anatomical damage. Our implant had shallow expulsion and subsidence risks.