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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_2821_Библиотеки_им_академика_М_И_Перельмана
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ChiricoE,PialouxV.Roleofoxidativestressinthepathogenesisofsicklecelldisease.IUMBLife.2012;64(1):72–80.
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S
pinecomplaintsareextremelycommon:symptomaticlumbardiskherniation,forexample,
hasa2%lifetimeprevalence;upto10%ofpatientsolderthan60maymeettheclinical
andradiographiccriteriaforlumbarstenosis.1Inbothcases,legpaincanoftenbeseenasa
primarymanifestationofthedisease.Practitionerswhoseepatientswithlowerextremitypain
in practice (e.g., foot and ankle surgeons, hip and knee surgeons) are almost certain to
encounterpatientswithspinepathologyintheirclinics.Thesecasescanfrequentlybedifficult
to manage as spine pathology and lower extremity pathology may overlap (e.g., hip
osteoarthritisandspinalstenosis),leavingconsiderabledoubtabouttheprincipalcauseofthe
patients’complaints.2Successfully identifyingthesepatientsandproviding them appropriate
care requires that providers consider spine problems in their differential diagnoses when
evaluating patients. In order to facilitate this differential, it is important to have a basic
understandingofspinalanatomy,pathoanatomy,andcommonspinalcomplaintsthatmaycause
patientstopresenttoalowerextremityclinic.
This chapterreviews basic spinalanatomyand neuroanatomyasitapplies tothe lower
extremity.This reviewoftheanatomy is then applied tothree commonconditions(cervical
myelopathy,lumbarstenosis,andlumbarradiculopathy)thatmightcausepatientstopresentto
a lower extremity clinic. The pathophysiology, diagnosis, and management of each disease
processarebrieflydiscussed.
SPINEANATOMY
VertebralAnatomy
Thespineconsistsofatotalof33vertebrae(7cervical,12thoracic,5lumbar,5sacral,and4
coccygeal)(Fig.21-1A).Althoughvertebraeinthesacrumandcoccyxarefused,vertebraein
the cervical, thoracic, and lumbar spine articulate through a series of diarthrodial (i.e.,
synovial) joints that are stabilized by several ligaments and muscular attachments. The
vertebraservesasa“buildingblock”forthespine,andthe24presacralvertebraeconsistofa
seriesoffunctionalspinalunitsconsistingoftwovertebralbodies,thefacetjointthatformsthe
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articulationbetweenthetwovertebraeandtheintervertebraldisk.Mostvertebraeinthespine
share a similar anatomy. Every vertebra consists of a vertebral body, pedicles, articular
processes, pars interarticularis,transverseprocesses, lamina,andspinousprocess(Fig. 21-
1B).
Thevertebralbodyisacylindricalmassoftrabecular,cancellousbonethatisfoundinthe
anterioraspectofthevertebralbody.Vertebralbodiesvaryinsize,generallyincreasinginsize
when moving more caudal in the spine. In the thoracic spine, the vertebral bodies have
articulations for the ribs. Inthe cervical spine, vertebral bodies articulate with each other
throughsaddle-shapedjointsreferredtoasthe“jointsofLuschka”oruncovertebraljoints.The
intervertebraldiskliesbetweenthevertebralbodiesoftwoadjacentvertebrae.
Justposteriortothevertebral bodyis thedorsalarch.In contrasttothe vertebral body,
whose anatomy is relatively simple, the dorsal arch consists of a series of processes that
enclose the spinal canal, allow for articulation with the neighboring vertebral bodies, and
provide attachment sites for ligaments and muscles. The dorsal arch of the vertebra is
connectedtothevertebralbodybyapairoftwostoutpillarsreferredtoasthepedicles.The
dorsal“arch”iscomposedofapairofflatsurfacescalledthelamina.Theseformtheroofof
thespinalcanal.Wherethelaminameetinthemidline,alargeprocessprojectsdorsally.This
iscalledthespinousprocess.
The remainingportions of the dorsal arch(transverse process, articular processes, and
parsinterarticularis)arefoundatthejunctionofthelaminaandthepedicles.Atthispoint,the
transverse processes extend to eitherside of the vertebral arch.In the thoracic spine, these
articulatewiththerib.Thearticularprocessextendssuperiorlyandinferiorlyfromthejunction
ofthe lamina and the pedicles to form thesuperior articular process andinferior articular
process, respectively. The area between the articular processes at the confluence of these
variousprocessesisreferredtoastheparsinterarticularis.Thesuperiorarticularprocessofa
givenvertebraarticulateswiththecomplementaryinferiorarticularprocessofthelevelabove.
Theseprocesseshavecartilageandformadiarthrodialjointcalledthefacetjoint.Avertebra
typically has four facet joints (two with the vertebrae above and two with the vertebrae
below).Typically,thesuperiorarticulatingprocessisdirecteddorsally,whereastheinferior
articularprocessisdirectedventrally(towardthebellybutton).Thespecificorientationofthe
facetjointsvariesbetweenthecervical,thoracic,andlumbarspineandissuitedbothtothe
typesofloadsandtypeofmotionexperiencedbythespecificspinalsegments(e.g.,rotation
andlateralbendinginthecervicalspineandflexion/extensioninthelumbarspine).Thespinal
nerverootexitsthespinalcordfromaspacejustanteriortothelateralaspectofthefacetjoint.
This space, referred to as the intervertebral foramen, is bordered anteriorly by the
intervertebral disk and posteriorly by the lateral aspect of the facet joint and ligamentum
flavum, and the superior and inferior boundaries are formed by the pedicles of the levels
aboveandbelow(Fig.21-1B).
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FIGURE21-1.ImportantAnatomicStructuresintheSpine.A:Imageofthevertebralcolumndepictingits
segmentalnature.B:Photographsofaspinemodeldepictingvariousimportantanatomiclandmarks:(1)vertebral
body,(2)superiorarticularprocess,(3)inferiorarticularprocess,(4)facetjoint;articulationbetweensuperiorand
inferiorarticularprocesses,(5)vertebralforamen,notethestructuresitisboundedby,(6)posteriorlongitudinal
ligament,(7)intervertebraldisk,(8)pedicles,(9)spinousprocess,(10)lamina,(11)transverseprocess.C:Profileof
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thespineillustratingtheposteriorlongitudinalligamentalongthedorsalsurfaceofthevertebralbodyandthe
ligamentumflavumalongtheventralsurfaceofthelamina;hypertrophyorossificationofthesesofttissuestructures
canreducethespaceinthespinalcanal.D:Posteriorviewoftheposteriorlongitudinalligament.Notethatthe
ligamentisthickcentrally,butthelateralaspectofthedisksisuncovered.(A:FromAnatomicalChartCompany,with
permission.CandD:FromHenryVandykeCarter[Publicdomain],viaWikimediaCommons).
Thediscussionabovehighlightsimportantstructuresthatmaycontributetocompressionof
neural elements and lead to lower extremity symptoms. In addition to the bony structures
mentioned earlier, soft tissue structures that might contribute to impingement include the
posteriorlongitudinalligament(PLL)andtheligamentumflavum(Fig.21-1C).ThePLLruns
along the posterior surfaces of the vertebral bodies from the vertebral body of C2 to the
sacrumandventraltothespinalcord.Theligamentumflavumisanelasticstructurethatserves
tohelpthevertebralcolumnmaintainanormalpostureandrunsdorsaltothespinalcord.The
ligamentum flavum is actually a series of small ligaments that serve to connect adjacent
vertebrallamina.
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FIGURE21-2.DepictionofaDermatomeMap.Notethateachregionisassociatedwithaspinallevel,for
example,medialaspectofthefootisinnervatedbytheL4nerveroot.Notethatthedistributionofthespine
segmentsisrelativelysimpleinthetrunkbutmorecomplexintheextremities.(ByGrant,JohnCharlesBoileau.An
atlasofanatomy:byregions1962.Publicdomain,viaWikimediaCommons.)
Neuroanatomy
Similar to the spine, the spinal cord is an anatomically segmented structure. There are 31
segmentsinthespinalcord:8cervical,12thoracic,5lumbar,5sacral,and1coccygeal.Each
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segment of the spinal cord innervates a single somite during development;this translatesto
eachspinalnerveretainingitsrelationshipwiththecharacteristicareasofskin andmuscles.
Theareaofskininnervatedbyasinglespinalsegmentisreferredtoasadermatome.Although
therelationshipbetweenspinalsegmentanddermatomeinthetrunkisquitesimpleandreflects
thesegmentalnatureofthespine,therelationshipinthelimbsismorecomplexbecauseofthe
outgrowthofthelimbbudsduringdevelopment.3TheseareillustratedinFigure21-2.
FIGURE21-3.Cross-SectionalViewoftheSpine.Informationinthespineiscarriedincharacteristicareas.The
redregionsrepresentdescendingtracts.Thepyramidaltracts(lateral)carrymotorinformationfromthemotor
cortextotheαmotorneuroncells.Theαmotorneuroncellsarelocatedintheanterolateralregionofthe“H”-shaped
centralgraymatteralsoseenintheimage.Thedorsalcordcontainsascendingafferentpathwayandcarries
sensoryinputresponsibleforproprioception.(ByPolarlysandMikaelHäggström[CCBY-SA3.0,
http://creativecommons.org/licenses/by-sa/3.0orGFDL,http://www.gnu.org/copyleft/fdl.html],viaWikimedia
Commons.)
Giventhesegmentalnatureofthecord,itistypicallydescribedincrosssection.Thecord
consists of a roughly H-shaped area of graymatter that is surroundedby myelinated white
matter.Eachlimbofthe“H”shapeofthegraymattercanbedividedintohorns(posteriorand
anterior),whereasthewhitemattersurroundingitisdescribedasfuniculi.Afferentfibers(i.e.,
sensoryinputsfromthelimb)enterthecordviathedorsalrootsandendontheipsilateralside.
Here,theseinputssynapseonneuronsintheipsilateralgraymatterintheposterolateralhorn
andfeedintoacomplexsystemofsensoryinputs.Aportionoftheseinputsgivesrise tothe
sensorypathwaysthatascendinthedorsalportionofthecord,whereasothersfeedintolocal
reflexcircuits.αmotor neuronsthatinnervateskeletalmuscles canbe foundintheanterior
horns.Therearecharacteristicenlargementsoftheanterior hornsinthecervical andlumbar
regions(moreαmotorneurons)toaccount formotorinnervation oftheextremities.Anterior
horncellsarearrangedincigar-shapedcolumnssuchthatmultiplelevelsmaycontributetothe
function of a given muscle (i.e., the quadriceps is innervated by anterior horn cells
correspondingtotheL2andL3segments).3Outputfromtheαmotorneuronsleavesthecord
viatheventralroots.Theremainderofthespinalcordhasafairlycharacteristicorganization;
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fibersaregenerallyorganizedbythetypeofinformationtheycarry.Acompleteunderstanding
ofthisschemaisbeyondthescopeofthischapter,butcanbefoundinFigure21-3.
Themotorneuroncellsintheanteriorhornaremodulatedbyacomplexsystemofinputs
fromthecorticospinaltractsthatdescendfromthecerebralcortexaswellasbrainstemand
diencephalicnuclei. The anteriorhorncellsare involved inthereflexresponse.A reflexis
definedasaninvoluntaryresponsetoasensoryinputwithcircuitrythatiscontainedentirely
within the spinal cord. The deep tendon reflexes commonly tested in the clinical setting
representanexampleofasimplereflexloop(Fig.21-4).3Thereflexattheknee,forexample,
involvestappingthe patellartendon,whichcauses asmall stretchofthe quadriceps muscle.
Thisstretchisdetectedbysensoryneuronswithinthemuscleandcarriedtothespinebythe
afferentpathway.Thesesensoryneuronssynapseontotheαmotorneuronsintheanteriorhorn
ofthespinalcordaswellasaninhibitoryinterneuron.Theαmotorneuronreceivesapositive
stimulus and acts to initiate quadriceps contraction, whereas the inhibitory interneuron
suppressestheαmotorneuronsoftheantagonistmusclegroup(hamstrings).Thesestimulithen
exit the spinal cord via the ventral nerve roots, traveling via the femoral nerve to the
quadriceps and via the tibial nerve to the hamstrings. Contraction of the quadriceps and
relaxation of the hamstrings lead to knee extension, or the knee-jerk commonly seen on
examination.Fromthisexample,itcanbededucedthatdamagetotheexitingnerveroot(e.g.,
due to compression in the neural foramen) can diminish or eliminate the reflex response.
Because ofthe segmental natureof thespine,reflexesaretypicallytied to a principal cord
segment(inthiscase,L2).Inthisway,reflexesareimportanttoolsbecausetheycanbeeasily
testedandcanbeusedtolocalizelesions.Thereflexesatthebiceps,brachioradialis,triceps,
andankle(Achilles)aregovernedbyasimilarloop;thelocalizationofthesereflexesisshown
inTable21-1.
Intruth,themonosynapticreflexdescribedaboveisasimplification.3Thefiringoftheα
motor neuron is modulated by several inputs from thedescending lateral cortical tracts. In
general,the descendingtractsserve tomodulatethefiring oftheαmotorneuronsandallow
volitionalcontroloftheupperandlowerextremities.Injurytothelateraldescendingtracts,as
canbeseenincertainneurologicdisordersorincompressionofthecervicalspine,canleadto
increasedmuscletone,hyperreflexia,andpathologicreflexes.Itisimportanttounderstandthe
distinction betweenupper and lower motor neuronsymptoms, and these are summarizedin
Table21-2.
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Table21-1.
FIGURE21-4.Exampleofasimplemotorreflexconsistingofanafferentneuron,αmotorneuron,andaninhibitory
interneuron.(ByAmiyaSarkar[Ownwork][CCBY-SA4.0,http://creativecommons.org/licenses/by-sa/4.0],via
WikimediaCommons.)
Finally,itisimportanttonotethatthehumanspinalcordreachesadultsizefasterthanthe
vertebralcolumn.Asaresult,itistypicallyshorterthanthevertebralcolumn,extendingfrom
the cervicalspinetoapproximatelythelevel ofL1/L2.3Below this region,the spinalcanal
containsthespinalnerves forthelumbarvertebral levels, butthesenerverootsareactually
givenoffathigherlevelsandtravelinthecordasastructurecalledthecaudaequina(horse’s
tail)(Fig.21-5).
CommonlyTestedReflexeswithAssociatedSpinalLevel
Reflex Level
Bicepsreflex C5,C6
Brachioradialis C6
Triceps C7,C8
Patellartendon(knee-jerk) L2,L3,L4
Achillestendon(ankle-jerk) S1,S2
SPINEPATHOLOGYWITHLOWEREXTREMITY
FINDINGS
CervicalSpine
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CervicalMyelopathy
Pathophysiology
Thetermmyelopathyreferstocompressionofthespinalcordleadingtouppermotorneuron
dysfunction. This compression encompasses a broad clinical spectrum and can involve
radicular(nerveroot,orlowermotorneuron)symptomsinadditiontocentral(spinalcord,or
uppermotorneuron)symptoms(Table21-2).4Intheradicularsyndrome,compressionofnerve
rootpredominates.Inthissyndrome,patientstypicallycomplainofupperextremitysymptoms,
andlowerextremitysymptomsarerare.Inthemedialsyndrome,patientscomplainoflongtract
signs(see diagnosissection),and lowerextremityinvolvementis common.Inthe combined
syndrome,patientspresentwithboth upperandlower extremitysymptoms—this isthe most
common presentation of cervical spondylotic myelopathy (CSM). There are also vascular
causesofmyelopathythatcanpresentwithamixedpatternofweaknessandupperandlower
extremityinvolvement.4CSMmayalsoaffecttheanteriorhorncellsintheuppercervicalspine
leadingtoupperextremityweaknesswithoutlowerextremityinvolvement.
4
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