MSK Mod 1 Flashcards
describe short bones
examples of short bones
tend to be equal in both dimension - cuboidal shape
carpals of wrist, tarsals of foot
function of flat bones and example
protective
skull
examples of irregular bones
vertebrae, facial bones
characteristics of long bone
- diaphysis
- metaphysis
- epiphysis
- epiphyseal plate
what is the diaphysis
primary ossification center
body of bone
what is the metaphysis
flattened portion of the diaphysis
what is the epiphysis
secondary ossification center (develop after birth)
what is the epiphyseal plate
cartilagenous growth plate bw diaphysis and epiphysis
two types of bone tissue
compact (cortical) and spongey (cancellous, trabecular)
cortical bone
how much of skeleton does it make up
turn over rate
forms 80% of human skeleton
slow turn over rate
dense, tightly pack osteons with Haversian canal system
what is the haversian system
- haversian canal - each canal contains blood vessel and nerve that communicate with periosteum
- concentric layers of bone surround the canal - lamelle
- osteocytes found within concentric layers
what is the canal system connecting to periosteum
Volkman’s canal - horizontal canal system
cancellous bone
20% of skeletal mass
less dense but large surface area
higher turnover rate
undergoes remodeling according to line of stress
what is Wolff’s law
increased mechanical stress will increase bone density
applies to cancellous bone
what is periosteum
thin, double layered, tough fibrous membrane that surrounds the bone
surrounds all of bone except at ligament or tendon insertion sites
-difficult to separate the periosteum from the bone
2 layers of periosteum
- outer
2. inner
what does the outer layer of periosteum contain
contains capillaries and nerves
what does inner layer of periosteum contain
-Sharpey’s fibers anchor periosteum (as well as tendons and ligaments) to the cortical bone
if there is active bone formation then the inner layer of periosteum contains
osteoblasts
if there is inactive bone formation then the inner layer contains
fibroblasts that can become osteoblasts if new growth is needed
what is the bone marrow
confined to cavities bw osseous component of bone
aka myeloid tissue
bone marrow consists of
blood vessels nerves mononuclear phagocytes stem cells blood cells in various stages of differentiation fatty tissue
function of bone marrow
formation of blood cells
two types of marrow in adults
- red
2. yellow
what is red bone marrow
active marrow
not all bones have active marrow
-pelvic bones, vertebrae, cranium and mandible, sternum and ribs, proximal femur, and humerus
-found in trabecular or spongy bone regions
what is yellow bone marrow
inactive marrow
yellow represents more of fatty cells
found in medullary cavity of long bone
3 examples of blood supply to bone
- nutrient arteries
- epiphyseal and metaphyseal arteries
- periosteal capillaries
what is the primary source of blood to the bone
nutrient arteries - enter middle of diaphysis
blood supply to the bone is critical for what
fracture repair and to maintain bone health
general healthy remodeling occurs in both
cortical and cancellous bone
bone remodeling happens when in life
throughout life
osteoporosis and relationship of osteoblast activity vs osteoclast acitivity
osteoblast activity
phases of bone remodeling
- activation
- resorption
- reversal
- formation
- quiescence
activation phase of bone remodeling
stimulus - hormone, drug, physical stimulus
action - stimulus activate resting osteoblasts to signal activation of osteoclastic activity
resorption phase of bone remodeling
action - osteoclasts break down bone, create a resorption cavity
- compact bone - resorption cavity follows longitudinal axis of Haversian’s canals
- cancellous bone - resorption cavity follow surface of trabeculae
reversal phase of bone remodeling
action - macrophages clean up the site and prepare it for laying down new bone
formation phase of bone remodeling-action
action - osteoblasts lay down new bone in resorption cavity
formation phase of bone remodeling - compact bone vs cancellous bone
compact bone - bone is laid down in concentric layers until small canal is formed (haversian’s canal); Haversian systems are constantly broken down with new ones being formed
cancellous bone - trabeculae are broken down and new ones formed
quiescence phase of bone remodeling
action - osteoblasts rest and are now bone lining cells on the newly formed bone surface
define a bone fracture
any defect in the continuity of a bone
3 basic etiological classifications of fractures
- sudden traumatic fracture - single episode of excessive force
- stress or fatigue fracture - repetitive episodes of normal force
- pathological fracture - normal force on abnormal bone
fracture classifications (3 parts)
- anatomical location of fracture (name the bone)
- region of the bone (diaphysis, metaphysis, physis, epiphysis)
- direction of fracture line (transverse, oblique, spiral)
define comminuted fx
fx with 3 or more fragments
pathological fracture
fx in area of preexisting bone dz
define incomplete fx
fx does not span entire cross section of bone, bone is not broken into separate segments
define segmental fx
fx middle fragment of bone surround by proximal and distal segements
define butterfly segment fx
similar to segmental except fx doesn’t span the entire cross section of bone
define stress fx
small fx caused by repetitive loading of bone
define avulsion fx
portion of bone is separated from bone caused from pulling of tendon or ligament at the insertion site
what is a closed fx
fx not exposed to the external environment
what is an open fx
fx exposed to the external environment
deformities of fx - displacement
aka translation
describes the position of the distal fragment (ant/post, medial/lateral)
deformities of fx - rotation
IR/ER with observation
deformities of fx - shortening of fx
ends of fx overlap
deformities of fx - angulation
direction in which the distal fragment points
ex. lateral/medial angulation
bone healing with inital fx
periosteum and blood vessels in the cortex and marrow are ruptured
3 phases of bone healing
- inflammatory phase
- reparative phase
- remodeling phase
inflammatory phase of bone healing
- what happens during
- xray shows?
increased blood flow into area after acute response to fx
hematoma forms
osteoclastic activity removes damaged bone
growth factors stimulate fibroblasts, osteoblasts at site
xray - fx line becomes more visible as necrotic tissue is removed
reparative phase of bone healing
- whats happening?
- xray shows?
soft fibrous callus forms initially followed by a hard callus
- osteoblasts are responsible for mineralized soft callus causing hard callus to form
- hard callus is considered immature bone - stable compared to soft callus but weak compared to mature bone
- xray - fx line begins to disappear
remodeling phase of bone healing
immature bone is replaced by organized mature bone
fracture line disappears
process begins during reparative phase
length of inflammatory phase of bone healing
days up to 1-2 weeks
length of reparative phase of bone healing
up to several months
length of remodeling phase of bone healing
months to years
goals of fx management
- achieve anatomic reduction
- restore stability
- create environment conducive to fx healing
- return pt to pre-injury function
- achieve acceptable cosmesis
criteria to determine when a fracture has healed
- clinical judgement - pt’s pain
- radiographic appearance - callus formation with disappearance of fx line
- anatomical location of fx and device - different bones heal at different rates
- ex. distal radial fx approx 6-8weeks vs mid diaphyseal fx approx 3 months
avg healing time bw:
kids
adolescents
adults
kids - 4-6 weeks
adolescents - 4-8 weeks
adults - 10-18 weeks
clinical s/s of fx
- trauma, pathological, stress fractures
- localized pain
- general rule of thumb - focused portion of bone regardless of direction of palpation
- pain with wt bearing
- edema, ecchymosis
- loss of function and mobility
examples of long bones
humerus, femur, tibia
examples of how to immobilize a fracture
- cast
- intramedullary rods/nails
- pins,wire,screws
- compression plates
- external fixator
- closed reduction
- open reduction
how does a cast help immobilize a fx
secondary healing with periosteal callus formation
how does intramedullary rods/nails immobilize fx
secondary healing with periosteal callus formation
how does pins, wire, screws immobilize fx
secodnary healing with periosteal callus formation
how does compression plate immobilize fx
primary bone healing, NO periosteal callus formation
-slower thus longer period of non-wt bearing
how does external fixator immobilize fx
either primary or secondary healing will occur
- if less rigid fixation: callus formation, secondary healing
- if very rigid: no callus formation, primary bone healing
how does closed reduction immobilize fx
manual manipulation of the extremity to align the fx fragments
how does open reduction immobilize fx
surgical reduction of extremity to align the fx fragments
-ex. ORIF - open reduction and internal fixation
healing complications of fx’s
- delayed or non-union
- avascular necrosis - femur head & scaphoid are common examples
- infection
potential secondary complications of fx’s
- potential growth impairments in children
- long term disuse can have significant impact on elderly
- cardiopulmonary complications d/t immobilization
- bone - localized osteoporosis
- transient muscle atrophy
what are pediatric fx called?
Salter Harris Fractures
5 types of Salter Harris Fx’s
Type 1: disruption of growth plate - distraction or slip injury
Type 2: fx line thru growth plate and metaphysis
Type 3: fx line thru growth plate and epiphysis
Type 4: fx thru metaphysis, growth plate, epiphysis
Type 5: compression injury of the growth plate
two types of bone formation
- intramembranous ossification
2. endochondral ossification
what is intramembranous bone growth
formation of flat bones; occurs in skull, face, mandible and clavicle
intramembranous growth pathophys
- occurs without a cartilage model
- undifferentiated mesenchymal cells differentiate into osteoblasts which then form the bone
stage one and two of intramembranous ossification
- cluster of osteoblasts form ossification center within fibrous connective tissue membrane
- osteoblast secretes bony matrix in surrounding fibrous membrane
- matrix is then calcified - osteoblast are now osteocytes trapped within matrix
stage three and four of intramembranous ossification
- formation of trabeculae - osteoid from around invaginating blood vessels; periosteum forms from mesenchymal cells
- bone collar of compact bone forms; red marrow is now formed within trabeculae
what is endochondral ossification
- has a cartilage model
- bone replaces cartilage (cartilage NOT converted to bone)
endochondral ossification is responsible for
- longitudinal bone growth during development
2. appositional growth (widening)during early development
what 2 cartilagenous growth zones exists in immature long bone
- spherical zone - around the end of epiphysis, allows for growth of epiphysis
- physis (epiphyseal plate) - between metaphysis and epiphysis; referred to as growth plate; allows for longitudinal growth
3 layers of physis
- reserve zone - early stages of cartilage cell
- proliferative zone - mature cartilage cell
- hypertrophic zone - cartilage cell hypertrophies, accumulate calcium and then dies; osteoblasts then enter and form new bone
epiphyseal plates typically fuse when?
bw 14-21 yo
epiphyseal plates fuse earlier in males or females?
females - d/t earlier puberty of females
how much of your spine is formed by the age of 8
80%
extremities grow at a __________ rate than axial skeletal throughout childhood
faster
-premature closure of lower extremity growth plates will influence ht more than spine
