ANATOMY  OF  BONE  AND  FRACTURE  HEALING  

MODERATOR  :DR.PRAMOD  B  ITAGI  PROFESSOR  &  UNIT  HEAD  

DEPARTMENT  OF  ORTHOPAEDICS    

PRESENTER  :DR.RAMACHANDRA  Dr.  SREE  KRISHNA  PATURI.  

ANATOMY  OF  BONE    

•  INTRODUCTION  •  GENERAL  FEATURES  OF  BONE  •  CLASSIFICATION  OF  BONE  •  MACROSCOPIC  ANATOMY  OF  BONE  •  MICROSCOPIC  STRUCTURE  OF  BONE  •  COMPOSITION  OF  BONE  •  HISTIOGENESIS  OF  BONE  

INTRODUCTION  •  The  basic  unit  of  human  skeleton  is  BONE.  •  Human  body  contains  206  bones.  •  Bone  is  essenIally  a  highly  vascular,living  constantly  changing  mineralized  connecIve  Issue.  

•  It  is  remarkable  for  its  hardeness,  resilience  &  regeneraIve  Issue.  

•  Bone  matrix  composed  of  organic  materials,mainly  collagen  fibres  &  inorganic  salts  rich  in  calcium  &  phosphate.  

GENERAL  FEATURES  OF  BONE    •  Typical  long  bone  has    

•  DIAPHYSIS  

•  EPIPHYSIS  

•  METAPHYSIS  

:

DIAPHYSIS:  •  The  porIon  of  long  bone  between  two  carIlaginous  ends  is  known  as  DIAPHYSIS.  

•  It  ossifies  from  primary  centre  of  ossificaIon  which  develops  first  in  early  foetal  life  in  hyaline  carIlage  model  of  future  bone.  

•  Primary  centre  &  process  of  bone  formaIon  extends  towards  two  ends.  

EPIPHYSIS:  •  The  two  carIlaginous  ends  of  a  growing  long  bone  are  known  as  EPIPHYSIS.  

•  Epiphyseal  carIlage:It  is  plate-­‐like,thin  layer  of  carIlage  which  seperates  growing  diaphysis  from  epiphysis.  

•  It  is  responsible  for  growth  in  large  bone.  •  The  cells  in  this  conInuously  proliferate  unIl  growth  completed.  

•  Epiphyseal  line:  The  peripheral  margin  of  epiphyseal  carIlage.  

METAPHYSIS:  •  The  part  of  diaphysis  immediately  adjacent  to  epiphyseal  carIlage  is  known  as    METAPHYSIS.  

•  It  is  the  site  advancing  ossifcaIon.  

Importance:  •  Most  vascular  part  of  a  long  bone  because  of  large  anastomosis  of  vessels.    

•  Growth  acIviIes  are  most  marked  in  this  zone.  

•  It  is  site  of  inserIon  of  muscles,  thus  it  is  liable  to  be  injured  due  to  muscular  strain.  

•  SomeImes  metaphysis  lies  within  capsular  ligament.So  infecIon  from  diaphysis  may  spread  to  the  joint.  

PARTS OF BONE

CLASSIFICATION  OF  BONE:  •  A)According  to  PosiIon:            Axial:Bones  forming  axis  of  body.                                Ex:skull,ribs,sternum,vertebrae.            Appendicular  Bones:  forming  skeleton  of  limbs.    •  B)According  to  Size&  Shape:              Long  bones:Present  in  upper  &  lower                                                          limbs.  Ex.Femur,radius                    Act    as  levers  for  movements  &  locomoIon.                                                            

 •  Short  bones:Polyhedral  &  cuboidal  in  shape.      Ex:Carpal  &  tarsal  bone.  

•  Flat  bones:Exapanded  &  plate  like.  •                                     Ex:scapula,sternum,ribs.  •  Irregular  bones:Ex:vertebrae  •  PneumaIc  bones:Flat  or  irregular  bones  possessing  a  hollow  space  within  their  body  containing  air.  Ex:ethmoid,mastoid  bones....  

   

•  Sesamoid  bones:They  are  nodules  of  bones  which  develop  in  certain  tendons.  

•  Do  not  possess  periosteum  &  haversian  system.  •  Ossify  aZer  birth.  •  Ex:pisiform,patella.  

According  to  Gross  structure:  

•  Compact(Lamellar)bone:  Outer  corIcal  part  of  long  bones,which  is  hard  &  homogeneous  appearence.  

   

•  Spongy(Cancellous)  bone:The  inner  part  of  long  bones,less  hard  &  presents  a  spongy  appearance.  

•  Diploic  bone:Consists  of  inner  &  outer  tables  of  compact  bone  &  in  between  a  porous  layer.  Ex:  cranial  bones.  

•  According  to  Development:  

•  Memranous  bones.  •  CarIlaginous  bones.  

MACROSCOPIC  ANATOMY  OF  BONE  

Living  bone  is  white.    

Its  texture  is  either  dense  like  ivory(compact  bone)  or  honeycombed  by  large  

caviIes(trabecular,cancellous  or  spongy  ),where  bone  elements  reduced  to  a  la\cework  of  bars  

and  plates.    

COMPACT  BONE:  

•  It  is  limited  to  corIces  of  mature  bones(corIcal  bone)  and  is  of  great  importance  in  providing  their  strength  .  

•  Its  thickness  vary  for  different  bones,according  to  their  overall  shape,posiIon  and  funcIonal  roles.  

COMPACT BONE

CANCELLOUS  BONE    

•  It  is  usually  internal,  giving  addiIonal  strength  to  corIces  and  supporIng  the  bone  marrow.  

•  Bone  forms  a  reservoir  of  metabolic  calcium(99%  of  calcium  is  in  the  bony  skeleton)  and  phosphate  which  is  under  hormonal  and  cytokine  control.  

CANCELLOUS BONE CANCELLOUS BONE

•  In  general  parts  of  bone  terminology:  

•   Depression                              -­‐                Fossa    •   Lengthy  depression    -­‐            Groove/Sulci  •  Notch                                                  -­‐              Incisura    •  Actual  gap                                    -­‐              Hiatus  •  Elongated  pointed                            projecIon                      -­‐          Spine          •  Rounded  projecIon        -­‐    Tuberosity/                                                                                  Trochanter    •  Long  projecIons                -­‐    Crests    

•  ProjecIon  close  to  condyle    -­‐  Epicondyle  •  Expanded  proximal  ends          -­‐  Head/caput  •  Hole  in  bone                                                  -­‐  Foramen    •  Plate  of  bone                                                -­‐  Laminae  •  A  large  Laminae                                      -­‐  Squamae  

MICROSCOPIC  STRUCTURE  OF  BONE:  

•  The  basic  structural  unit  of  compact  bone  is  Haversian  system  or  Osteon,named  aZer  Clopton  Havers(1691).  

•  It  contains  following  structures:  •  Haversian  canal  •  Lamellae  •  Lacunae  •  Canaliculi  •  Volkamann's  canal  

Haversian  Canal:      •  It  is  present  in  the  centre  of  each  Haversian  system  approximately  20micrometer  in  diameter.    

•  It  runs  parallel  to  the  long  axis  of  bone.  •  Each  canal  consists  of  small  artery,vein,lymphaIcs,thin  fibers  and  supporIng  delicate  areolar  Issue.  

Lamellae:  •  a)Concentric  Lamellae:Thin  plates  of  bony  Issue  consisIng  of  ground  substance  or  matrix  with  collagen  fibres  lying  in  a  calcified  material.  

•  Arranged  concentrically  around  the  Haversian  canal.  

•  Adjacent  lamellae  are  held  together  by  interchange  of  fibres.  

•  b)IntersIIal  Lamellae:Lie  in  the  interval  between  typical  haversian  system.    

•  c)CircumferenIal  Lamellae:Found  at  outer  and  inner  periphery  of  the  cortex.  

Lacunae:Small  spaces  between  lamellae,each  containing  a  bone  cell(Osteocyte).  

Canaliculi:Are  fine  radiaIng  channels  which  connect  lacunae  with  each  other    and  central  Haversian  canal.    

•  The  canaliculi  are  occupied  by  proplasmic  processes  of  bone  cells.  

Volkamann's  Canal:    •  Are  oblique  canals  running  at  right  angles  to  the  long  axis  of  bone.  

•  Contain  the  neurovascular  bundle  and  connect  Haversian  canals  with  the  medullary  cavity  and  surface  of  bone.  

•  These  canals  are  not  surrounded  by  concentric  lamellae  of  bone.  

Periosteum:  •  As  a  rule  external  surface  of  any  bone  covered  by  a  membrane  called  periosteum.  

•  Except  that  are  covered  with  ar3cular  car3lage.  

•  The  periosteum,  consisIng  of  two  layers:  

Ø An  outer  FIBROUS  LAYER  and    

Ø An  inner  more  cellular  and  vascular  CAMBIUM  LAYER”.  

•  The  thicker,  more  cellular  periosteum  of  infants  and  children  has  a  more  extensive  vascular  supply  than  that  of  adults.    

•  Perhaps  because  of  these  differences,  the  periosteum  of  children  is  more  acIve  in  healing  many  fractures.  

•  Young  bones  the  cellular  layer  consists  of  numerous  osteoblast    (osteoprogenIc  layer),  whereas  in  the  adult  osteoblast  are  not  conspicuous,  but  osteoprogenitor  here  can  form  osteoblast  when  need  arises  

Endosteum:    It  lines  the  walls  of  bone  caviIes  including  the  marrow  spaces  forming  inner  limiIng  membrane.  

COMPOSITION  OF  BONE:                                          a)  Organic  matrix(25%)                                          b)Inorganic  elements(65%)                                          c)Water(10%)  

Organic matrix

bone cells 4%

Intercellular matrix 20%

• Collagens • Protein peptides • Proteoglycans • Lipids

• Osteocyte • Osteoblast Bone lining cells • Osteoclast

Mesenchymal precursor cells

Osteoprogenator stromal cells

Osteoprogenator  stromal  cells:  

•  From  pleuripotent  stromal  stem  cells  form  bone  marrow  and  connecIve  Issue.  

•  It  resemble  fibroblast(mesenchlmal  origin)  •  DifferenIate  into  osteoblasts.  •  Based  on  nature  of  inducIon  these  may  defferenIate  into:  fibroblasts,myoblasts,pericytes,adipocytes,and  chondroblasts.  

Osteoblast:  

•  15-­‐30micrometer,basophilic  cuboidal  mononuclear  cells.  

•  Found  in  surfaces  of  growing  or  remodelling  bone  forming  a  monolayer.  

•  Responsible  for  synthesis,deposiIon  and  mineralisaIon  of  bone  matrix.  

•  Its  surface  rich  in  alkaline  phosphatase  acIvity  located  at  plasma  membrane.  

•  It  synthesises:  

•  Type  1  and  type  5  collagen  •  Gamma  carboxylglutamic  acid(GLA)  containing  osteocalcin  and  GIA  protein.  

•  OsteonecIn  •  Proteases  and  growth  factor  •  It  bears  receptors  for  Vit.D3,PTH  and  1,25,(OH)2  VitD3.  

Osteocyte:  •  Major  cell  type  of  mature  bone.  •  Derived  from  osteoblasts  which  have  reduced  or  caesed  matrix  formaIon.  

•  Numerous  fine  process  emerge  from  cell  body  and  interconnect  with  each  other.  

•  Each  osteocyte  is  in  a  lacunae.  •  Average  life  span  25yrs.  •  When  dead,they  retract  their  processes  and  becoming  metabolically  inacIve.  

•  Inhibits  resorpIon  or  addiIon  of  matrix  at  surface.  

Bone  lining  cells:  •  Are  flajened  epithelium  like  cells  parIcularly  evident  in  adult  skeleton  found  on  resIng  surface  of  bone  i,e.those  not  undergoing  deposiIon/resorpIon.  

•  It  lines      -­‐Endosteal  surface  of  marrow  cavity                                    -­‐Periosteal  surface                                    -­‐vascular  canal  within  osteons.  •  Plays  role  in  regulaIng  differenIaIon  of  osteoprogenator  cells.  

•  Control  ares  of  osteoclasts  on  bone  surface  and  regulate  mineral  homeostasis.                                                      

Osteoclasts:  •  Large  polymorphous  cell  15-­‐20  or  more  nuclei.  •  Lie  where  acIve  removal  of  bone  is  occuring  on  surface.  

•  Responsible  for  removal  of  bone,they  cause  demineralisaIon  by  protein  release  and  also  by  lysosomal  and  non  lysosomal  enzymes.  

•  Arise  from  mononuclear  lineage.  •  Survival  Ime  appr.7wks.  •  SImulators  are:PTH,Factors  from  osteoblasts,macrophages/lymphocytes,decreased  intracellular  calcium.  

Bone  Matrix:    •  It  is  the  extracellular  mineralized  material  of  bone  and  consists  of  a  ground  substance  in  which  are  embeded  numerous  collagen  fibres.  

•  In  early  stages  of  bone  formaIon,before  mineralizaIon,the  matrix  is  Osteiod.  

•  In  adult  bone  amount  of  osteiod  is  very  small,reflecIng  local  remodelling  of  bone  in  which  mineralizaIon  follows  deposiIon  of  organic  matrix.  

Collagen:  •  Bone  contains  type  1  and  type  5  which  is  thought  to  regulate  fibrillogenesis.  

•  It  is  synthesized  from  osteoblasts.  •  Other  organic  components  of  matrix  like  OsteonecIn  is  phosphorylated  glycoprotein  secreated  by  osteoblasts  and  bound  mainly  to  minerals.  

•  Osteocalcin  :Glycoprotein  synthesized  by  osteoblasts.it  is  bound  to  mineral  and  is  used  as  a  marker  of  bone  formaIon.  

Inorganic  elements  

Hydroxyapatite

Crystalline Amorphous Calcium Phosphate

• Trapped Ions •  • Citrate • Fluride • Sodium • Magnesium • Potassium

Blood  Supply:  •  One  or  two  main  diaphyseal  nutrient  arteries  enter  shaZ  obliquely  through  nutrient  foramina  leading  into  nutrient  canals.  

•  Entry  is  directed  away  from  dominant  growing  epiphysis.  

•  Nutrient  arteries  divided  into  ascending  and  descending  branches  in  medullary  cavity.  

•  Near  epiphysis  these  vessels  joined  by  terminals  of  numerous  metaphyseal  and  epiphyseal  arteries.  

•  Medullary  arteries  of  shaZ  give  of:  •  Centripetal  branches    •  CorIcal  branches    

•  Large  irregular  bones  recieve  a  periosteal  supply  and  large  nutrient  arteries  penetraIng  directly  into  cancellous  bone.  

•  Short  bones  recieve  numerous  fine  vessels  from  periosteum  at  non  arIcular  surfaces.  

•  Arteries  enter  vertebrae  close  to  transverse  processes;their  medulla  drains  to  two  large  basivertebral  veins  converging  to  a  foramen  on  posterior  surface  of  vertebral  body.  

•  LymphaIc  vessels  accoumpany  periosteal  plexuses.  

Nerve  Supply:  •  These  are  most  numerous  in  arIcular  extremiIes  of  longbones,vertebrae  and  larger  flat  bones.  

•  Nerves  occur  widely  in  periosteum,  fine  myelinated  and  non-­‐myelinated  fibres  accoumpany  nutrient  vessels  into  bone  marrow  and  lie  in  perivascular  spaces  of  Haversian  canals.  

HISTIOGENESIS  OF  BONE:  

•  Bone  first  appears  aZer  7th  embryonic  week.    •  They  develop  from  embyonic  mesenchymal  Issue.  

•  The  process  of  gradual  bone  formaIon  is  called  OssificaIon.  

•  These  are  of  two  types:  •  1)Endochondral  OssificaIon  •  2)Membranous  OssificaIon  

•  1)Endochondral  OssificaIon:  •  In  embryonic  life  most  of  skeleton  is  composed  of  carIlage,  which  is  absorbed  &  replaced  by  bone.  

•  This  process  known  as  Endochondral  OssificaIon.  

•  It  begins  prenatally  &  conInous  throughout  postnatal  period  unIl  growth  is  complete.  

•  2)Membranous  OssificaIon:  •  When  bone  is  formed  directly  from  a  loose  form  of  connecIve  Issue  without  intervening  stages  of  carIlage  formaIon,  calcificaIon  and  resorpIon  and  process  is  known  as  Membranous  OssificaIon.  

Mesenchyme to bone

MICROSCOPIC  ORGANIZATION  OF  BONE  

Woven  Bone  •  Immature  bone  •  Forms  De  novo,  Healing  bone  

•  Rate  of  deposiIon  &  turnover  is  Rapid.  

•  Collagen  fibrils:  Irregular  Diameter  &  no  consistent  orientaIon.  

•  Lamellar  Bone  •  Mature  bone  •  Forms  only  in  exisIng  bone.  

•  It  is  Slower.  •  Regular  &fibrils  organized  in  response  to  loads.  

•  Woven  Bone  •  Osteocytes:  •  variable  in  size,  mineral  density  &  orientaIon    &  numerous  in  number.  

•  It  is  easily  deformed.  

•  Lamellar  Bone  •  Osteocytes:  •  Regular&  lie  between  lamellae  &  mineral  density.  

•  It  is  sIffer.  

FRACTURE  HEALING  

•  HISTORY  

•  INTRODUCTION  

•  STAGES  OF  FRACTURE  HEALING  

•  VARIABLES  INFLUENCE  IN  #  HEALING    

HISTORY:  •  Bones  have  broken  since  begining  of  humanity  and  have  been  recognised  as  long  as  recorded  history.  

•  John  Hunter,a  pupil  of  Haller  described  morphologic  sequence  of  fracture  healing.  

•  In  1917,Bier  reported  sImulaIon  factor  for  new  bone  formaIon  was  present  in  organized  blood  clot  of  the  fracture  haematoma.  

INTRODUCTION:  •  A  fracture  is  defined  as  a  break  in  conInuity  of  bone.  

•  Fracture  in  man  heal  and  unite  by  two  main  ways:  

•  1)Primary/Osteonal/Direct  Healing:          •       Bone  formaIon  occurs  directly  without  any  callus  formaIon.This  occurs  parIcularly  in  stable,aligned,closely  apposed  fracture.  

2)Secondary/Indirect  Healing:  •  It  is  usual  type  consisIng  of  formaIon  of  callus  either  of  carIlaginous  or  fibrous.  

•  This  callus  is  later  converted  into  lamellar  bone.  

•  When  fracture  is  not  rigidly  fixed  and  movements  occur,in  such  cases  callus  is  replaced  by  bone  healing.  

•  On  x  ray  charecterised  by  abundant  callus  formaIon,temporary  widening  of  fracture  gap  and  slow  disappearance  of  radiolucent  fracture  line  due  to  fibrocarIlage  mineralisaIon.  

STAGES  OF  FRACTURE  HEALING:  •  OsteoinducIon  is  a  first  step  in  bone  healing.  •  It  causes  mesenchymal  cells  to  differenIate  into  various  cells  which  then  proliferate  &  produce  messenger  substances  which  further  sImulate  mesenchymal  cells  to  differenIate.  

•  OsteconducIon  a  scaffold  of  collagenous  network  has  developed  upon  which  reparaIve  cells  produce  callus  &  bone.  

The  various  stages  of  #  Healing  includes:  

•  Stage  of  Haematoma  FormaIon.  •  Stage  of  GranulaIon  Issue.  •  Stage  of  Repair/Callus.  •  Stage  of  ConsolidaIon.  •  Stage  of  Remodelling.  

Stage  of  Haematoma  FormaTon:    •  Begins  immediately  following  injury  and  followed  rapidly  by  repair.  

•  The  Haematoma  provides  3  imp.  factors:  

•  It  immobilizes  #  and  swellings  hydrostaIcally  splints  the  #  and  thus  provides  small  amount  of  mechanically  stability  of  #  site.  

•  It  provides  a  fibrin  scaffold  that  facilitates  migraIon  of  repair  cells.  

 •  Haematoma  brings  the  osteclast  &  chondrocyte  precursors  to  #  site  in  large  numbers  that  begin  to  differenIate  into  osteoblasts  and  chondrocytes  to  begin  producing  matrix.  

•  The  loss  of  haematoma  will  impair  the  #  healing.  

Stage  of  GranulaTon  Tssue:  •  GranulaIon  Issue  replaces  iniIal  haematoma  &  differenIates  into  connecIve  Issue  &  fibrocarIlage.  

Injured  Issue  &  platelets  

Vasoactive meditors

New vessels,fibroblasts, intercellular matrix

Granulation tissue

Stage  of  Repair/Callus:    Osteogenesis  

Cartilage cells lay in osteoid tissue

Matrix with type 1 collagen fibrils

Deposition of calcium Hydroxyappetite

Callus / Woven/Immature bone

Stage  of  ConsolidaTon:  •  By  the  acIvityof  osteoblasts  woven  bone  transformed  into  mature  bone.  

Stage  of  Remodelling:    •  The  process  occurs  along  with  deposiIon-­‐resorpIon  phenomenon.  

•  osteoclast  has  important  role  in  this  phase.  

Remodelling  does  four  things:  

•  It  replaces  mineralised  carIlage  with  woven  bone.  

•  Packets  of  new  lamellar  bone.  •  New  secondary  Osteons  made  of  Lamellar  bone.  

•  It  tends  to  remove  any  callus  plugging  marrow  cavity  

FRACTURE  HEALING  IN  CANCELLOUS  BONE:    •  The  extent  of  bone  &  marrow  necrosis  following  cancellous  bone  #  is  much  less  than  in  compact  bone,because  of  good  circulaIon.  

•  Primary  healing  takes  place  in  this,secondary  healing  is  rare  and  endochondral  bone  formaIon  excepIonal.                                

VARIABLES  INFLUENCE  IN  #  HEALING:  •  Cruses  and  Buck  Walter  have  divided  variarles  into  four  groups  

1)INJURY  VARIABLES:  Ø Open  Fractures:Delays  repair  by  soZ  Issue  disrupIon  &disturbed  blood  supply  to  #  site.  

Ø severity  of  injury:Extensive  soZ  Issue  &  •   bone  damage  leads  to  delayed  #  healing.  

Ø IntraarTcular  fracture:  It  requires  reconstrucIon  of  joint  surface,stable  fixaIon  &  early  mobilisaIon.  

Ø Segmental  fracture:It  leads  to  delayed  union/non  union  due  to  disrupted  intramedullary  blood  supply  of  middle  fragments.  

Ø SoX  Tssue  interposiTon:Open  reducIon  to  extricate  interposed  Issue  will  enhance  #  healing  process.  

Ø Damage  to  blood  supply:Delay  #  healing.  

2)PATIENT  VARIABLES:  Ø Age:Extremes  of  age  have  influenes  on  #  healing.  

Ø Nutri3on:Poor  nutriIonal  status  affects  #  healing  &  can  lead  to  mortality  &  surgical  complicaIons.  

Ø Systemic  Hormones:  Steroids,anIcoagulants,anIinflammatory  drugs  inhibit  whereas  GH,insulin  thyroid  hormone  enhance  #  healing.  

Ø Nico3ne    

3)TISSUE  VARIABLES:      Ø Form  of  bone:Cancellous  bone  healing  is  rapid  due  to  larger  surface,rich  in  cells  &  blood  supply.  

Ø Bone  Necrosis  Ø Bone  diseases:Osteoporosis,Primary  malignant  bone  tumours,metastasis,bone  cysts  etc...  all  cause  pathological  bone  #  and  delay  bone  healing.  

Ø Infec3on:It  slows  down/prevents  healing.  

4)TREATMENT    VARIABLES:  Ø Apposi3on  of  #  Fragments:Decreasing  #  gap  decreases  volume  of  repair  Issue  needed  to  heal  #.  

Ø Loading  &  Micrimo3on:Loading  a  #  site  &  induced  micrimoIon  along  bone  #  sites  promotes  healing  but  too  much  moIon  lead  to  non  union.  

Ø Fracture  Stabilisa3on:It  will  prevents  repeated  disrupIon  of  repair  &  enhances  #  callus.  

Ø Rigid  Fixa3on:Stable  fixaIon  allows  early  mobilisaIon  of  joints  &  hence  prevents  sIffness.  

Ø Bone  GraIing:It  is  osteoinducIve  &  osteoconducIve.  

Ø Demineralised  Bone  marrow:The  factors  in  bone  marrow  sImulate  bone  formaIon,by  migraIon  of  undifferenIed  mesenchymal  cells  to  implanted  matrix  &  differenIaIon  into  mesenchymal  cells.  

 

DHANYAVAAD