MSK Module 1A Flashcards
Diaphysis of long bone
Primary ossification center
Body of bone
Metaphysis of long bone
Flattened portion of diaphysis
Epiphysis of long bone
Secondary ossification center (develop after birth)
Epiphyseal plate of long bone
Cartilagenous growth plate between diaphysis and epiphysis
Two types of bone tissue
- Cortical
- Cancellous (spongy/trabecular)
Describe cortical bone
- Compact bone
- 80% of skeleton
- Slow turnover rate
- Dense tightly packed osteons with Haversian canal system
- Volkman’s canal
Describe the Haversian system (osteon)
- Structure of cortical bone
- Consists of: Haversian (central) canal, lamelle (concentric layers of bone), osteocytes within lamelle
What is Volkman’s canal?
- Cortical bone
- Horizontal canal system connecting to periosteum
What are lamelle?
- Cortical bone
- Concentric layers of bone surrounding Haversian canal
Describe cancellous bone
- Trabecular/spongy
- 20% of skeleton
- Less dense but large SA
- Higher turnover rate
Cancellous bone undergoes remodeling according to:
Line of stress
What is Wolff’s Law?
Increased mechanical stress will increase bone density
What is the periosteum?
- Thin double layered fibrous membrane that surrounds bone
- EXCEPT at ligament or tendon insertion sites
What does the outer layer of periosteum contain?
Capillaries and nerves
What does the inner layer of periosteum contain?
- Sharpey’s fibers (anchors periosteum to cortical bone)
- Osteoblasts (if active bone formation)
- Fibroblasts (if inactive formation, can become osteoblasts if new growth needed)
What is the function of bone marrow and what are the types?
- Formation of blood cells
- Red (active, spongy bone)
- Yellow (inactive, medullary cavity of long bone)
What is the blood supply of bone?
- Nutrient arteries
- Epiphyseal/metaphyseal arteries
- Periosteal capillaries
What are the phases of bone remodeling?
- Activation
- Resorption
- Reversal
- Formation
- Quiescence (resting)
What stimulates activation of bone remodeling? What is the action of activation?
- Hormone, drug, physical
- Resting osteoblasts signal activation of osteoclasts
Describe the phase of resorption in bone remodeling
- Osteoclasts break down bone
- Create a resorption cavity
Where is the resorption cavity in compact bone?
Follows longitudinal axis of Haversian canals
Where is the resorption cavity of cancellous bone?
Follows surface of trabeculae
Describe the reversal phase of bone remodeling
Macrophages clean up and prepare resorption cavity for laying down new bone
Describe the formation phase of bone remodeling
- Osteoblasts lay down new bone in resorption cavity
- Compact: concentric layers until canal is formed
- Cancellous: trabeculae broken down and new ones formed
Describe quiescence phase of bone remodeling
Osteoblasts “rest” and are now bone lining cells on newly formed bone surface
Etiological classifications of fractures
- Sudden traumatic (single episode of excessive force)
- Stress/fatigue (repetitive episodes of normal force)
- Pathological (normal force on abnormal bone)
Systems of classifying fractures
- Anatomical location
- Region of bone (e.g. diaphysis)
- Direction of fracture line (transverse, oblique, spiral)
- Condition of bone (e.g. comminuted, incomplete)
- Condition of soft tissue (open, closed)
- Deformities of the fracture
Define comminuted fracture
3+ fragments
Define segmental fracture
Middle fragment of bone is fractured surrounded by proximal and distal segments
Define butterfly segment fracture
Similar to segmental except it doesn’t span entire cross section of bone
Define avulsion fracture
- Portion of bone is separated from bone
- Caused from pulling of tendon or ligament at insertion site
Displacement (translation) fracture
Position of distal fragment (anterior/posterior, medial/lateral)
Define shortening of the fracture
Ends of the fracture overlap
Define angulation of the fracture
Direction in which distal fragment points
What is primary bone healing?
- Bone stabilization very rigid
- NO callus formation
- Longer time until stable
What is secondary bone healing?
- Bone stabilization less rigid
- Callus formation
- Callus provides earlier stability
Phases of bone healing
- Inflammatory
- Reparative
- Remodeling
Inflammatory phase of bone healing
- Days to 1-2 wks
- Increased bloodflow into area
- Hematoma forms
- Osteoclasts remove damaged bone
- GFs stimulate fibroblasts, osteoblasts
When does fracture line become more visible on x-ray?
During inflammatory phase of healing as necrotic tissue is “removed”
Reparative phase of bone healing
- Up to several months
- Soft fibrous callus forms initially, followed by hard callus (caused by osteoblasts)
- Hard callus is considered immature bone (stable but weak)
When does fracture line on x-ray begin to disappear?
During reparative phase of bone healing (months)
Remodeling phase of bone healing
- Months to years
- Immature bone is replaced with mature bone
- Fracture line disappears
- Process begins during reparative phase
Goals of fracture management
- Achieve anatomic reduction
- Restore stability
- Promote joint ROM
- Pre injury function
How is a fracture determined healed?
- Clinical judgment
- Radiographic appearance
- Anatomical location of fracture and device
Methods of immobilization of fractures
- Cast
- Intramedullary rods/nails
- Pins, wires, screws
- Compression plate
- External fixator
Which immobilization methods are primary vs. secondary bone healing?
Primary = compression plate (and external fixator in certain cases) Secondary = everything else
Define closed reduction and internal fixation (CRIF)
- Manual manipulation of the extremity to align the fracture fragments
- Should be done ASAP
Define open reduction and internal fixation (ORIF)
Surgical reduction of extremity to align fracture fragments
Fracture healing complications
- Delayed or non-union
- Avascular necrosis
- Infection
What is nonunion of fracture?
Localized pain and tenderness to fracture that persists longer than expected healing time
Salter Harris (pediatric) fracture types
1: Disruption of growth plate
2: Fracture line through growth plate and metaphysis
3: Through growth plate and epiphysis
4: Through metaphysis, growth plate, and epiphysis
5: Compression injury of growth plate
Intramembranous growth of bone
- Formation of flat bones
- Occurs w/o a cartilage model
- Undifferentiated mesenchymal cells differentiate into osteoblasts
Endochondral ossification growth of bone
- Cartilage model
- Bone replaces cartilage
Stages of intramembranous ossification
- Cluster of osteoblasts
- Bone matrix is secreted
- Formation of trabeculae
- Bone collar of compact bone forms and red marrow appears
Two cartilagenous growth zones in immature long bone:
- Spherical zone (around end of epiphysis, allows for growth)
- Physis (epiphyseal plate, “growth plate”, allows for longitudinal growth)
Layers of the physis (epiphyseal plate)
- Reserve zone - early stages of cartilage cell
- Proliferative zone - mature cartilage cell
- Hypertrophic zone - cartilage cell accumulates Ca and then dies, osteoblasts then enter and form new bone
When do epiphyseal plates typically fuse?
Between ages 14-21
*Occurs earlier in females d/t earlier puberty
80% of full spine growth has occurred by age:
8
Extremities grow at a ____ rate throughout childhood than axial skeleton
Faster
