The LM Posterior Root Stabilizes the ACL Deficient Knee

Abstract

This open‐access article is published and distributed under the Creative Commons Attribution ‐ NonCommercial ‐ No Derivatives License (http://creativecommons.org/licenses/by‐nc‐nd/3.0/), which permits the noncommercial use, distribution, and reproduction of the article in any medium, provided . You, transform, or (s) . For and , please ' s : / / www . sagepub . com / journalsPermissions . nav .Objectives:Themeniscihaveanimportantroleinstabilizingthekneejoint.Thebiomechanicaleffectsoflateralmeniscalposteriorroottearswithorwithoutmeniscofemoralligament(MFL)tearsinanteriorcruciateligament(ACL)deficientkneeshavenotbeenstudiedindetail.TheaimofthisstudywastodeterminethebiomechanicaleffectsofdisruptionofthelateralmeniscusposteriorrootattachmentinACL-intactandACL-deficientknees.Itwashypothesizedthatdisruptionoftheposteriorhornlateralmeniscalrootattachmentwouldcauseasignificantincreaseinbothanteriortibialtranslation(ATT)andinternalrotationduringasimulatedpivotshiftandalsoininternalrotationtestsintheACL-deficientknee,bothwithandwithoutintactmeniscofemoralligaments.Methods:Tenpaired(n=20)fresh-frozencadaverickneesweremountedina6degree-of-freedomrobotfortestinganddividedintotwosequentialcuttinggroups.Thesectioningorderforgroup1was(1)ACL,(2)lateralmeniscusposteriorrootand(3)MFL.Thesectioningorderforgroup2was(1)lateralmeniscusposteriorroot,(2)ACL,and(3)MFL.Foreachcuttingstate,displacementsandrotationsofthetibiaweremeasuredandcomparedtotheintactstatefollowingasimulatedpivotshifttest(5Nminternalrotationtorquecombinedwitha10Nmvalgustorque)at0°,20°,30°,60°and90°ofkneeflexion;ananteriortranslationload(88N)at0°,30°,60°and90°ofkneeflexion;andinternalandexternalrotation(5-Nm)at0°,30°,60°,75°and90°ofkneeflexion.Results:CuttingtheLMrootandMFLssignificantlyincreasedATTduringasimulatedpivotshifttestat20°and30°whencomparedtotheACLcutstate(p<0.05)(Figure1).CuttingtheLMrootinACLintactkneessignificantlyincreasedinternalrotationbybetween0.4°±0.4°and1.3°±0.9°(p<0.05),exceptat0°(p=0.136).WhentheACL+LMrootcutstatewascomparedtotheACLcutstate,theincreaseininternalrotationwassignificant(p<0.05)athigherflexionangles(75°and90°)butnotbetween0°-60°.Forananteriortranslationload,cuttingtheLMrootinACLdeficientkneessignificantlyincreasedATTat30°(p<0.05).Conclusion:TheLMposteriorrootwasasignificantprimarystabilizerofthekneeforinternalrotationandanteriortibialtranslationduringpivotingactivitiesatlowerflexionanglesandinternalrotationathigherflexionangles.LateralmeniscalposteriorroottearsshouldberepairedconcurrentlywithACLreconstruction.IncreasedkneeinstabilityduetolateralmeniscalrootdeficiencymaycontributetoincreasedfunctionallimitationsinpatientsandpotentiallytoACLreconstructiongraftfailure.