Condyle secondary cartilage-a misnomer

Condyle- secondaryCondyle- secondary
cartilage-a misnomercartilage-a misnomer
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CartilageCartilage
It’s a type of connective tissue found onIt’s a type of connective tissue found on
the ends of bones, which protects andthe ends of bones, which protects and
cushions them, and absorbs the forcsescushions them, and absorbs the forcses
transmitted throughout the body;a livingtransmitted throughout the body;a living
tissue without a direct blood supply.tissue without a direct blood supply.

Facts about cartilageFacts about cartilage
Mesenchymal in originMesenchymal in origin
Consists of cartilage cells called chondrocytesConsists of cartilage cells called chondrocytes
and a ground substanceand a ground substance
Rigid and firm, but not hardRigid and firm, but not hard
Matrix is noncalcified and avascularMatrix is noncalcified and avascular
Can grow both interstitially and appositionallyCan grow both interstitially and appositionally
Is covered by perichondrium but can existIs covered by perichondrium but can exist
without one.without one.
Uniquely Pressure tolerant.Uniquely Pressure tolerant.

Types of Cartilage and theirTypes of Cartilage and their
DistributionDistribution
Hyaline cartilage - 1. Costochondral JunctionsHyaline cartilage - 1. Costochondral Junctions
2. Articular surfaces of most2. Articular surfaces of most
jointsjoints
3. Some laryngeal cartilages3. Some laryngeal cartilages
4. Walls of Trachea and large4. Walls of Trachea and large
bronchibronchi
5. Epiphyseal plate of long bones5. Epiphyseal plate of long bones

Fibrocartilage – 1. Secondary cartilaginous joints or symphysisFibrocartilage – 1. Secondary cartilaginous joints or symphysis
2. Articular discs of Synovial joints2. Articular discs of Synovial joints
3. Shoulder and hip joints3. Shoulder and hip joints
Elastic cartilage – 1. AuricleElastic cartilage – 1. Auricle
2. Medial part of auditory tube2. Medial part of auditory tube
3. Epiglottis3. Epiglottis

Methods of OssificationMethods of Ossification
Endochondral OssificationEndochondral Ossification
Intramembranous OssificationIntramembranous Ossification

Steps in Endochondral OssificationSteps in Endochondral Ossification
Mesenchymal condesation atMesenchymal condesation at
site of bone formationsite of bone formation
Differentiation of mesenchymalDifferentiation of mesenchymal
cells to form chondroblasts.cells to form chondroblasts.
Those on the surface formThose on the surface form
perichondriumperichondrium
Calcification of intercellularCalcification of intercellular
substancesubstance
Formation ofFormation of PRIMARYPRIMARY
AREOLAEAREOLAE
Invasion of calcifiedInvasion of calcified
cartilaginous matrix by thecartilaginous matrix by the
PERIOSTEAL BUDPERIOSTEAL BUD

Formation ofFormation of SECONDARYSECONDARY
AREOLAEAREOLAE
Differentiation of osteogenicDifferentiation of osteogenic
cells to osteoblastscells to osteoblasts
Formation of Osteoid and it’sFormation of Osteoid and it’s
subsequent calcificationsubsequent calcification

Primary Vs Secondary CartilagePrimary Vs Secondary Cartilage
According to Stutzmann (1976)According to Stutzmann (1976)
Primary CartilagePrimary Cartilage – exists in the axial skeleton,– exists in the axial skeleton,
skull base and limbs; the dividing cells , theskull base and limbs; the dividing cells , the
differentiated chondroblasts are surrounded by adifferentiated chondroblasts are surrounded by a
cartilaginous matrix that isolates them from localcartilaginous matrix that isolates them from local
factors able to restrain or stimulate cartilaginousfactors able to restrain or stimulate cartilaginous
growthgrowth

Secondary Cartilages – exist in the condylar and
coronoid processes and sometimes in sutures;the
dividing cells ,prechondroblasts, are not
surrounded by a cartilaginous matrix and thus are
not isolated from local growth modifications

Origin of the term “SecondaryOrigin of the term “Secondary
CartilageCartilage
A common theory of the 18A common theory of the 18thth
and 19and 19thth
century – that cartilage always precededcentury – that cartilage always preceded
and turned into bone.and turned into bone.
That most bone was not transformedThat most bone was not transformed
cartilage but formed by an independentcartilage but formed by an independent
process ( intramembranous ossification) –process ( intramembranous ossification) –
gave forth the revolutionary idea ofgave forth the revolutionary idea of
“Secondary Cartilages “.“Secondary Cartilages “.

Schaffer’s Definition of SecondarySchaffer’s Definition of Secondary
cartilagescartilages
Schaffer defined as secondary or accessory anySchaffer defined as secondary or accessory any
cartilage forming after and separate from thecartilage forming after and separate from the
primary cartilaginous skeleton.primary cartilaginous skeleton.
Examples – mandibular symphysis, condyle,Examples – mandibular symphysis, condyle,
coronoid process , ends of clavicle,on severalcoronoid process , ends of clavicle,on several
bones of the cranial vault, cartilage participatingbones of the cranial vault, cartilage participating
temporarily in callus formation.temporarily in callus formation.
Heterotrophic cartilage – secondary cartilagesHeterotrophic cartilage – secondary cartilages
that are occasional abnormal malformations notthat are occasional abnormal malformations not
typical of the site and species – eg.cartilage intypical of the site and species – eg.cartilage in
human arterial walls.human arterial walls.

Apart from differing times of firstApart from differing times of first
formation can one otherwiseformation can one otherwise
justify a separation of secondaryjustify a separation of secondary
cartilage from primary?cartilage from primary?

Fuch’s refutation of SecondaryFuch’s refutation of Secondary
cartilagecartilage
Argued that the relation between secondaryArgued that the relation between secondary
cartilages and pressure / mechanical stimulationcartilages and pressure / mechanical stimulation
was inconsistent.was inconsistent.
Noted that the mechanical action of the condyleNoted that the mechanical action of the condyle
played no role in the formation of cartilage.played no role in the formation of cartilage.
That no criterion – whether of timing, histology orThat no criterion – whether of timing, histology or
etiology precisely seperated the two categories.etiology precisely seperated the two categories.
Contended that he had positive evidence thatContended that he had positive evidence that
secondary cartilages were in fact primary.secondary cartilages were in fact primary.
Claimed to have recognized aClaimed to have recognized a
CHONDROBLASTEM at sites of futuresCHONDROBLASTEM at sites of futures
secondary cartilage.secondary cartilage.

Key points of FuchKey points of Fuch
Mechanical forces cannot be seen to play a roleMechanical forces cannot be seen to play a role
in the origin of all secondary cartilages.in the origin of all secondary cartilages.
There is overlap between the first appearance ofThere is overlap between the first appearance of
primary and secondary cartilages.primary and secondary cartilages.
The secondary cartilages vary greatly in theirThe secondary cartilages vary greatly in their
histologic appearance.histologic appearance.
He called to attention the secondary nature ofHe called to attention the secondary nature of
structures not included by Schaffer -structures not included by Schaffer -

If the boundaries of Schaffer’sIf the boundaries of Schaffer’s
class of secondary cartilages soclass of secondary cartilages so
vulnerable, has the concept anyvulnerable, has the concept any
value?value?

Differences between condylarDifferences between condylar
and epiphyseal cartilagesand epiphyseal cartilages
Biologic criteriaBiologic criteria Epiphyseal growthEpiphyseal growth
platesplates
CondyleCondyle
OriginOrigin Derivative ofDerivative of
primordial cartilageprimordial cartilage
Secondary cartilageSecondary cartilage
formation on originalformation on original
membrane bonemembrane bone
GrowthGrowth InterstitialInterstitial Peripheral inPeripheral in
FibrocartilageFibrocartilage
covering; proliferatingcovering; proliferating
cells are not cartilagecells are not cartilage
cells butcells but
undifferentiatedundifferentiated
mesenchymal cells.mesenchymal cells.
Mechanical StimuliMechanical Stimuli UnresponsiveUnresponsive ResponsiveResponsive

Biologic CriteriaBiologic Criteria EpiphysealEpiphyseal
Growth PlatesGrowth Plates
CondylesCondyles
MaturationMaturation Secondary ossificationSecondary ossification
centers,final fusion andcenters,final fusion and
disappearance of alldisappearance of all
cartilagecartilage
Conversion fromConversion from
hypertrophic to nonhypertrophic to non
hypertrophic state buthypertrophic state but
not complete conversionnot complete conversion
to boneto bone
HistologyHistology Only the degenrativeOnly the degenrative
zone is mineralizingzone is mineralizing
Whole hypertrophic areaWhole hypertrophic area
is in state ofis in state of
mineralization, structuralmineralization, structural
organization is lackingorganization is lacking
Hormonal controlHormonal control Marked response toMarked response to
thyroxine deficiency,afterthyroxine deficiency,after
final fusion no furtherfinal fusion no further
response to growthresponse to growth
hormonehormone
Minimal response toMinimal response to
thyroxinethyroxine
deficiency.Maturedeficiency.Mature
condyle can becondyle can be
reawakened by growthreawakened by growth
hormonehormone

Growth of MandibleGrowth of Mandible

Effects of Orthodontic forces on theEffects of Orthodontic forces on the
MandibleMandible
It is fair to say that controlling excessive mandibular growth is anIt is fair to say that controlling excessive mandibular growth is an
important unsolved problem in orthodontics.important unsolved problem in orthodontics.
If growth stimulation is defined as producing a larger mandible at theIf growth stimulation is defined as producing a larger mandible at the
end of total growth period than would have existed withoutend of total growth period than would have existed without
treatment; it is much harder to demonstrate a positive effect.treatment; it is much harder to demonstrate a positive effect.
The ultimate size of mandible in treated and untreated patients isThe ultimate size of mandible in treated and untreated patients is
remarkably similar.remarkably similar.
Muscle activity is not necessary to obtain growth modification.Muscle activity is not necessary to obtain growth modification.
When the mandible is protruded or restrained, changes occur on theWhen the mandible is protruded or restrained, changes occur on the
temporal as well as the mandibular side of the TMJ.temporal as well as the mandibular side of the TMJ.
The Herbst appliance is potentially the most effective of functionalThe Herbst appliance is potentially the most effective of functional
appliances in altering jaw growth probably because of its full timeappliances in altering jaw growth probably because of its full time
action, but is also rather unpredictable in terms of the amount ofaction, but is also rather unpredictable in terms of the amount of
skeletal versus dental changes likely to be produced.skeletal versus dental changes likely to be produced.

Acceleration of mandibularAcceleration of mandibular
growth often occurs but a longgrowth often occurs but a long
term increase in size is difficultterm increase in size is difficult
to demonstrate and,if it existsto demonstrate and,if it exists
at all, is so small to beat all, is so small to be
clinically significant.clinically significant.
Functional appliances that areFunctional appliances that are
aimed at stimulatingaimed at stimulating
mandibular growth produce amandibular growth produce a
highly variable response,buthighly variable response,but
the growth acceleration thatthe growth acceleration that
sometimes occurs can besometimes occurs can be
usefuluseful

Tentative interpretation of theTentative interpretation of the
method of operation of functionalmethod of operation of functional
appliancesappliances
Functional Appliance
Increased contractile
activity of the LPM
Intensification of
repetitive activity of
the retrodiscal pad
Increase in growth stimulating
factors

Increase in growth stimulating factors
.Change in condylar trabecular orientation
.Additional Growth of condylar cartilage
.Additional subperiosteal ossification of the posterior border of
The mandible
Supplementary lengthening of the
mandible

Functional Appliances believed toFunctional Appliances believed to
stimulate growth of condylarstimulate growth of condylar
cartilagecartilage
Class II elastics – believed to stimulate growth rate andClass II elastics – believed to stimulate growth rate and
amount of condylar cartilage; the stimulating actionamount of condylar cartilage; the stimulating action
mediated primarily through the retrodiscal pad.mediated primarily through the retrodiscal pad.
Herren (L.S.U activator) – increase growth of condylarHerren (L.S.U activator) – increase growth of condylar
cartilage if the appliance is worn for 12 – 18 hours.cartilage if the appliance is worn for 12 – 18 hours.
Increased repititive activity of retrodiscal pad producesIncreased repititive activity of retrodiscal pad produces
hypertrophy of condylar chondroblasts.hypertrophy of condylar chondroblasts.
Neither the functional regulator nor the Harvold activatorNeither the functional regulator nor the Harvold activator
are capable of altering the size of the mandible.are capable of altering the size of the mandible.

Condylar Cartilage before and afterCondylar Cartilage before and after
resection of LPM and retrodiscal Padresection of LPM and retrodiscal Pad
Resection of LPM andResection of LPM and
retrodiscal pad produces aretrodiscal pad produces a
significant slowdown ofsignificant slowdown of
condylar cartilage growth ratecondylar cartilage growth rate
Interruption of blood supply toInterruption of blood supply to
the differentiatingthe differentiating
skeletoblasts;originating fromskeletoblasts;originating from
the LPM may be the probablethe LPM may be the probable
cause.cause.

Demise of the Lateral PterygoidDemise of the Lateral Pterygoid
HypothesisHypothesis
Anatomic research hasAnatomic research has
not found significantnot found significant
attachments of the LPMattachments of the LPM
to the condylar head.to the condylar head.
Hyperactivity of the LPMHyperactivity of the LPM
during mandibularduring mandibular
advancement thereapy isadvancement thereapy is
doubtful as the muscledoubtful as the muscle
actually shortens duringactually shortens during
this procedure.this procedure.

New bone formation atNew bone formation at
the condyle wasthe condyle was
associated withassociated with
decreased postural EMGdecreased postural EMG
activity in the LPM,activity in the LPM,
masseter and digastricmasseter and digastric
musclesmuscles
This has led to theThis has led to the
evolution ofevolution of NONNON
MUSCULARMUSCULAR
HYPOTHESISHYPOTHESIS..

Lateral Functional Shift of the mandible –Lateral Functional Shift of the mandible –
effects on condylar cartilage thickness andeffects on condylar cartilage thickness and
proliferationproliferation
Condyle on the side opposite the direction of shift isCondyle on the side opposite the direction of shift is
displaced anteriorly or protruded while the condyle ondisplaced anteriorly or protruded while the condyle on
the side towards the shift is more stable positionally andthe side towards the shift is more stable positionally and
is less likely to be retruded.is less likely to be retruded.
Growth of the Mandibular Condylar Cartilage (MCC)Growth of the Mandibular Condylar Cartilage (MCC)
adapts to its local functional biomechanical environmentadapts to its local functional biomechanical environment
Thus differential changes in the metabolic activity of theThus differential changes in the metabolic activity of the
MCC would be expected on the non protruded andMCC would be expected on the non protruded and
protruded sides.protruded sides.
Increased thickness of the MCC was followed byIncreased thickness of the MCC was followed by
temporary increased proliferation of prechondroblastictemporary increased proliferation of prechondroblastic
cells on the protruded side.cells on the protruded side.

Clinical implicationsClinical implications
Functional appliances which protrude orFunctional appliances which protrude or
retrude the mandible and alter the localretrude the mandible and alter the local
functional-biomechanical environment;functional-biomechanical environment;
can alter the growth of the MCC.can alter the growth of the MCC.

What exactly affects the growth ofWhat exactly affects the growth of
the condylar head?the condylar head?
Genetic theoryGenetic theory -- suggests that condylar growth issuggests that condylar growth is
strongly under the influence of genes.strongly under the influence of genes.
Functional Matrix TheoryFunctional Matrix Theory –– though attractivethough attractive
could not satisfactorily explain how condylar growthcould not satisfactorily explain how condylar growth
would be stimulated by the growth of the soft tissues.would be stimulated by the growth of the soft tissues.
Endow and HansEndow and Hans –– mandibular growth is a composite ofmandibular growth is a composite of
regional forces and functional agents of growth controlregional forces and functional agents of growth control
that interact in response to specific extracoronalthat interact in response to specific extracoronal
activating signalsactivating signals..

Growth Relativity Hypothesis –Growth Relativity Hypothesis –
John VoudourisJohn Voudouris
Based on three mainBased on three main
foundations –foundations –
Glenoid fossaGlenoid fossa
promotes condylarpromotes condylar
growth with the use ofgrowth with the use of
mandibularmandibular
advancementadvancement
thereapy.thereapy.

Growth Relativity HypothesisGrowth Relativity Hypothesis
Viscoelastic tissuesViscoelastic tissues
anchored betweenanchored between
glenoid fossa and theglenoid fossa and the
condyle insert directly intocondyle insert directly into
condylar fibrocartilagecondylar fibrocartilage
and affect its growth.and affect its growth.
Transduction of forcesTransduction of forces
over the fibrocartilaginousover the fibrocartilaginous
cap of condylar headcap of condylar head
occurs as the viscoelasticoccurs as the viscoelastic
tissues are stretchedtissues are stretched
during mandibularduring mandibular
advancementadvancement

Light Bulb Analogy of CondylarLight Bulb Analogy of Condylar
growth and Retentiongrowth and Retention
The condyle lights upThe condyle lights up
like a LIGHT BULB onlike a LIGHT BULB on
a dimmer switcha dimmer switch
when it iswhen it is
continuouslycontinuously
advanced.advanced.
The reactivatedThe reactivated
muscle activity dimsmuscle activity dims
the light bulb andthe light bulb and
returns it to normalreturns it to normal
growth activity at thegrowth activity at the
end of treatment.end of treatment.www.indiandentalacademy.comwww.indiandentalacademy.com

Conclusions of John VoudourisConclusions of John Voudouris
Propulsive mandibular appliances such as herbst and twinblock causePropulsive mandibular appliances such as herbst and twinblock cause
growth modification of the condyle fossa region that involves–growth modification of the condyle fossa region that involves–
Displacement of mandibleDisplacement of mandible
Viscoelastic tissue extension forces to the condyleViscoelastic tissue extension forces to the condyle
Transduction of forces radiating beneath the fibrocartilage of the condyleTransduction of forces radiating beneath the fibrocartilage of the condyle
and glenoid fossa.and glenoid fossa.
Condylar growth modifications occur relative to the glenoid fossa and notCondylar growth modifications occur relative to the glenoid fossa and not
necessarily as an independent and isolated phenomenon.necessarily as an independent and isolated phenomenon.
New bone formation at the condyle and glenoid fossa is associated withNew bone formation at the condyle and glenoid fossa is associated with
decreased postural EMG activity in the LPM, masseter and anterior digastricdecreased postural EMG activity in the LPM, masseter and anterior digastric
muscles.muscles.
Fixed functional appliances (Herbst) produce consistent and reproducibleFixed functional appliances (Herbst) produce consistent and reproducible
condyle fossa changes compared with inconsistent results reported forcondyle fossa changes compared with inconsistent results reported for
removable functional appliances.removable functional appliances.
Bone formation in the glenoid fossa and condyle was statistically significantBone formation in the glenoid fossa and condyle was statistically significant
compared to controls.compared to controls.
Condylar response appears to be age determined.Condylar response appears to be age determined.

Unique features of the mandibularUnique features of the mandibular
condylecondyle
A major site of growth having considerable clinicalA major site of growth having considerable clinical
significance.significance.
Not a pacesetting “master center” with all other regionalNot a pacesetting “master center” with all other regional
growth fields subordinate to and dependant on it .growth fields subordinate to and dependant on it .
The condylar cartilage has a secondary type of cartilageThe condylar cartilage has a secondary type of cartilage
which developed because of changed functional andwhich developed because of changed functional and
developmental conditions imposed on this part of thedevelopmental conditions imposed on this part of the
mandible.mandible.
The condylar cartilage is not the pacemaker for theThe condylar cartilage is not the pacemaker for the
growth of the mandible. It functions to provide regionalgrowth of the mandible. It functions to provide regional
adaptive growth.adaptive growth.
The condyle performs a dual role –The condyle performs a dual role –
Provides pressure tolerant articular contact.Provides pressure tolerant articular contact.

Makes possible a multidimensional growthMakes possible a multidimensional growth
capacity in response to ever changingcapacity in response to ever changing
developmental conditions and variations.developmental conditions and variations.
The condylar cartilage does have someThe condylar cartilage does have some
measure of intrinsic genetic programming.Themeasure of intrinsic genetic programming.The
cartilage cells are coded to divide and divide butcartilage cells are coded to divide and divide but
extracondylar features are needed to sustain thisextracondylar features are needed to sustain this
activity.activity.
Condylar prechondroblasts are randomlyCondylar prechondroblasts are randomly
arranged providing an opportunity for selectedarranged providing an opportunity for selected
multidirectional growth potential in contrast tomultidirectional growth potential in contrast to
long bones.long bones.

ConclusionsConclusions
Secondary cartilages resemble each other in many respects eg-the clavicleSecondary cartilages resemble each other in many respects eg-the clavicle
and mandibular condyle have a similar layering and disorder in their growthand mandibular condyle have a similar layering and disorder in their growth
cartilages.cartilages.
Secondary cartilages alike in many ways differ in others.Secondary cartilages alike in many ways differ in others.
No one secondary cartilage can represent all the properties in it’s class.No one secondary cartilage can represent all the properties in it’s class.
The argument that secondary cartilage can validly be distinguished fromThe argument that secondary cartilage can validly be distinguished from
primary one has hinged not only on morphology and histochemistry but onprimary one has hinged not only on morphology and histochemistry but on
whether a mechanical factor underlies secondary chondrogenesis.whether a mechanical factor underlies secondary chondrogenesis.
Secondary cartilages have no manifest unity being in the first place nonSecondary cartilages have no manifest unity being in the first place non
primary cartilages.They cannot be unified by a known mechanical etiology.primary cartilages.They cannot be unified by a known mechanical etiology.
Condylar cartilage can at best be considered a modified periosteum.Condylar cartilage can at best be considered a modified periosteum.
Condylar cartilage is rather like an epiphysis at the end of a long bone butCondylar cartilage is rather like an epiphysis at the end of a long bone but
unlike the clavicle it has no secondary center of ossification.unlike the clavicle it has no secondary center of ossification.

following people who helped me immensely duringfollowing people who helped me immensely during
the preparation of this seminarthe preparation of this seminar..
Dr.Uma ShankarDr.Uma Shankar
Dr.(Ms.) Uma ShankarDr.(Ms.) Uma Shankar
Dr.VinodDr.Vinod
Dr.Kuber SoodDr.Kuber Sood
Dr.RameshDr.Ramesh
Dr.KartikDr.Kartik
Dr.DivyaDr.Divya
Dr.BalajiDr.Balaji
Thanks for making it all worthwhile

Cartilage matrix production and chondrocyteCartilage matrix production and chondrocyte
enlargement as contributors to mandiularenlargement as contributors to mandiular
growth in Animals ( AJODO Oct.1991)growth in Animals ( AJODO Oct.1991)
Mandibular growth in length at the condyleMandibular growth in length at the condyle
results fromresults from
Perichondral andPerichondral and
Chondral componentsChondral components
Matrix production depends on systemicMatrix production depends on systemic
influences while chondrocyte enlargement mightinfluences while chondrocyte enlargement might
be affected by local factors.be affected by local factors.
One could speculate that chondrocyteOne could speculate that chondrocyte
enlargement rather than matrix productionenlargement rather than matrix production
should be primarily affected by orthopedicshould be primarily affected by orthopedic
appliances aimed at altering condylar growthappliances aimed at altering condylar growth
though this aspect has never been investigated.though this aspect has never been investigated.

Condyle secondary cartilage-a misnomer

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