Hydrogels for nucleus replacement : facing a biomechanical challenge

• Author(s): Reitmaier, S. ; Wolfram, U. ; Ignatius, A. ; Wilke, H. - J. ; Gloria, A. ; Martín-Martínez, José M. ; Correia, Joana Silva ; Oliveira, Joaquim M. ; Reis, R. L. ; Schmidt, H.
• Date: 2012
• Persistent ID: http://hdl.handle.net/1822/23132
• Origin: RepositóriUM - Universidade do Minho
• Subject(s): Compression test; Disc regeneration; Hydrogels; In vitro; In vivo; intervertebral disc; Nucleus replacement
• Document Type: Article
• Language: English

Description

Hydrogelsareconsideredpromisingfordiscregenerationstrategies.However,itiscurrently unknownwhetherthedestructionofthenaturalinterfacebetweennucleusandsurrounding structurescausedbynucleotomyandaninadequateannulusclosurediminishesthemechan- ical competenceofthedisc.This in vitro studyaimedtoclarifythesemechanismsandto evaluatewhetherhydrogelsareabletorestorethebiomechanicalbehaviourofthedisc. Nucleuspressureinanovineintervertebraldiscwasmeasured in vivo during dayandnightandadaptedtoan in vitro axial compressivediurnal(15min)andnight(30min) load. Effectsofdifferentdefectsondischeight andnucleuspressureweresubsequently measured in vitro using 30ovinemotionsegments.Followingcaseswereconsidered:intact; annulusincisionrepairedbysutureandglue;annulusincisionwithremovalandre-implanta- tion ofnucleustissue;andtwodifferenthydrogelsrepairedbysutureandglue. Theintradiscalpressure in vivo was0.75MPaduringdayand0.5MPaduringnight correspondingtoan in vitro axial compressiveforceof130and58N,respectively.The compressiontestshowedthatneithertheimplantation ofhydrogelsnorthere-implantation of thenaturalnucleus,assumedasbeingtheidealimplant,wasabletorestorethemechanical functionalityofanintactdisc. Resultsindicatetheimportanceofthenaturalanchorageofthenucleuswithitssurround- ingstructuresandtherelevanceofanappropriateannulusclosure.Therefore,hydrogelsthat areabletomimicthemechanicalbehaviourofthenativenucleusmayfailinrestoringthe mechanicalbehaviourofthedisc.