Lecture 30 - Bone Flashcards
T or F: Bone is the hardest of all connective tissue
T
Bone is a _______ (what is depositited in the ECM?)
connective, dynamic tissue in which the ECM is hardened by deposition of calcium
Bone can mean what 2 things:
- Osseous tissue only
- Organ composed of blood, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue
What are the 5 functions of bone
- Structural Support
- Permit movement
- Protect vital organs
- Hematopoiesis
- Mineral homeostasis
What are the 3 types of cells found in bones and their function
- Osteoblasts: Bone forming cells that are found in the endosteum and periosteum that synthesize bone
- Osteocytes: Mature bone cells that act as mechanosensory receptors to regulate bone response to stress and mechanical load and communicate to osteoblasts and osteoclasts
- Osteoclasts: Found on bone surface and derived from bone marrow that is responsible for bone resorption
Osteoblasts turn into
Osteocytes
What are the 2 components that make up the ECM of bone
- Organic Component: Made of type 1 collagen, glycosaminoglycans and proteoglycans that gives bone flexibility
- Inorganic Component: Deposits crystals of calcium and phosphate that enables bone to support weight of body without sagging
T or F: Bone is a composite (combined of 2 or more materials without dissolving into each other)
T
What are the 2 layers of bone
- Outer layer: compact or cortical bone
- Inner layer: Cancellous, trabecular or spongy bone
What 2 architectures of bone are formed from collagen
- Woven bone: Disorganized network of collagen fibers that make up young bone and is mechanically weak
- Lamellar Bone: Organized collage that forms mature bone and is mechanically strong
Bone Marrow
Soft tissue that occupies the medullary cavity of a long bone and spaces in spongy bone
What are 2 types of bone marrow and their function
- Red Marrow: Found in skull, pelvis, spine, ribs and ends of long bones that perform hemopoiesis and remove old blood cells from circulation
- Yellow Marrow: Found in spongy bones and shafts of long bone that are now inactive to red blood cell formation and mainly made of fat
T or F: Yellow marrow turns into red marrow
F, red marrow turns into yellow marrow as it gets older
Label the missing parts of the long bone (wont be tested but good to know)
Skeleton before birth consists of
cartilage and fibrous structures shaped like bones
Ossification
Formation of bone
What are the 2 methods of ossification
- Intramembranous: Mandible, clavicle, skull
- Endochondral: Rest of skeleton
Bone Modeling
Process where bones change their overall shape in response to physiologic influences or mechanical forces
Wolff’s Law in regards to bone modeling
Long bones change shape to accommodate stresses placed on them
T or F: formation and resorption between osteoblasts and osteoclasts, respectively are not tightly linked in bone modeling
T
Bone remodeling
Renewal of bone by continuous removal of packets of bone by replacing it with proteinaceous matrix and mineralization to maintain bone strength that occurs in cortical and cancellous bone to prevent bone micro-damage
T or F: In bone remodeling, osteoclasts and osteoblasts are tightly linked for bone formation and resorption
T
What are the 4 steps of bone remodeling
- Activation: Osteoclasts
- Resorption: 2-4 weeks
- Reversal: Change from resorption to bone formation
- Formation: 4-6 months to complete
Fracture
Loss of continuity of the bone
What are 3 classification of fractures
- Pattern
- Cause -> traumatic or pathologic
- Body part
Difference between open verses closed fractures
Open/Compound Fractures: Skin is broken and bone protrudes outwards
Closed: Skin is not broken
Difference between displaced versus non-displaced for fractures
Displaced: Bone moved so there is a gap around the fracture
Non-displaced: Bone did not move
What are 2 patterns of bone fractures
- Single straight-line break: Oblique (diagonal to long axis of bone) or transverse (perpendicular to long axis of bone)
- More than a single straight line: Greenstick, comminuted, spiral
Colles vs Smith Fracture
3 factors that determine adequacy of X-Ray
- 2 views @ 90 degrees to each
- Needs to have 2 joints that are above or below area of interest or should subluxation/dislocation
- Needs to have adequate penetration to should bone and soft tissue
How to read an X-Ray for a fracture
- Observe entire length of the bone looking for fracture lines or distortions in the contours
- Describe the fracture based on
-Anatomical location (left or right; bone involved; exact location (proximal, diaphyseal, distal); intra or extraarticular)
-Pattern: Position of the fracture line relative to long axis
-Number of fragments: Simple or comminuted
-Alignment of fractur fragements: distal fragments
What are 3 types of fracture repairs
- Casting: Closed reduction
- Open reduction and internal fixation: Involves surgery where you get hardware such as metal rods, screws or plates for fractures that cannot be reduced or realigned by casting alone
- Open-reduction and external fixation: Involves surgery to repair the fracture and placement of an external fixation device that supports the bone to hold it in the correct position
Bone fracture healing (technically tissue regeneration)
Process of fracture healing that recapitulates bone development
What are the 5 stages of bone fracture healing
- Induction: Occurrence of fracture that breaks blood vessels in bone and periosteum forming a hematoma
- Inflammation: Lasts 1 week and is where hematoma coagulates around fracture, angiogenesis (development of granulation tissue), and differentiation of osteoblasts take place
- Soft callus formation: Fibroblasts deposit collagen and osteogenic cells become chondroblasts, endochondral formation occurs at fracture ends and external to periosteum to form cartilaginous (soft callus) tissue to stabilize fracture structure
- Hard callus formation: Osteogenic cells also become osteoblasts and form a bony collar to turn the soft callus to a hard callus to provide the fracture with a semi-rigid structure to allow for weight-bearing. Cartilage becomes replaced with woven bone from calcification.
- Bone remodeling: Second resorptive phase initiates to remodel hard callus into lamellar bone structure with central medullary cavity. Osteoclasts (Resorption of hard callus) and osteoblasts are balanced (deposition of lamellar bone)
For the process of bone remodeling to be successful an adequate [blank] and increase in [blank] are required
blood supply and increase in mechanical stability
What are 4 factors that affect bone healing
- Injury - Severity, open fracture, damage to blood supply, mobility at fracture site
- Patient - Comorbidity
- Tissue - bone disease (osteoporosis)
- Treatment
Complications of fractures can arise from what 4 things and cause what 16 effects (dont remember all just some)
What is slow union and its treatment
Fracture takes longer than usual to unite
Treatment: Patience
What is delayed union and its treatment
Union of fracture fails to occur in the expected time frame most likely due to inadequate fixation (gap at fracture ends)
Treatment: Need to differentiate between slowed and delayed union as both are similar, if delayed then continue immobilization and reassess
What is a non-union fracture
Fracture that failed to unite and will never unite unless change in treatment (diagnose 6 months down the line)
What are 2 types of non-union fractures
- Hyper-trophic
- Atrophic
Hyper-trophic non-union fractures and problem with healing
Sclerosis around bone ends and medullary canals are sealed off, fracture line is visible, bone ends joined by fibrous and cartilaginous tissue which can develop pseudoarthrosis
Problem: Unstable fixation with adequate blood supply
Atrophic non-union fractures and problem with healing
No evidence of cellular activity at fracture (no callus formation and bone ends are narrow, rounded and osteoporotic (avascular)
Problem: Inadequate blood supply and lack of gradual increase in mechanical stability
Mal-union fracture and treatment
Fracture healed in position of persistent angulation or rotation which is of a degree that gives the limb a displeasing appearance or affects its function
Treatment:
If detected before union is complete: Wedge in of plaster or manipulation under anesthesia
If detected after union is complete: Osteotomy if severe deformity
Long bone shortening
Consequence of mal-union that is usually seen with transverse and spiral fractures
Traumatic epiphyseal arrest
When the epiphyseal plate is damaged in trauma resulting in an immature skeleton:
-> if the whole plate is affected then growth will be altered at that limb level (shortening)
-> if plate is incompletely affected then get irregular growth
Describe the ilizarov procedure and what it is used to treat
Circle of pins above and below fracture in healthy bone that move the healing fracture apart until optimal distance to prevent bone shortening
Treatment: For complex/open fractures or limb lengthening
Joint stiffness in regards to fractures (3 causes)
Common consequence of immobilization of a fracture to ensure healing due to:
1. Intra-articular
2. Close to the joint
3. Remote from the joint
5 methods to reduce joint stiffness with a fracture
- Accurate reduction of fracture
- Splint minimum number of joints
- Splint for the shortest time compatible with relief of pain and fracture healing
- Mobilization of unsplinted joints
- Elevation of injured part during the initial stages to reduce edema
Complex Regional Pain Syndrome
Distal extremity fracture that is not usually noticed until cast is removed and has a heightened sympathetic response (pronounced swelling, shiny glazed skin and increased pain)
What does complex regional pain syndrome look like radiographically
- United fracture
- Diffuse osteoporosis
Avascular necrosis
Death of bone due to interference with blood supply that causes affected bone to become soft and distorted leading to pain, stiffness, and osteoarthritis
Where does avascular necrosis commonly occur
- Comminuted fractures
- Intra-capsular fractures of femur
- Dislocation of the hip
- Scaphoid fractures
What is unique radiographically about avascular necrosis
May be slow to develop radiographically (6-18 months)
Myositis Ossificans
Calcified mass of tissue forms near a joint leading to limited ROM because hematoma formation in soft tissue undergoes same process as a fracture hematoma so fibroblasts are converted into osteoblasts
What are some common sites of myositis ossificans
- Joints -> elbow, hip, shoulder, knee
- Muscles -> Quadriceps, brachialis, deltoid
3 treatment for myositis ossificans
- Rest the area during initial inflammatory response
- Indomethacin (NSAID) to block production of prostaglandins
- Reduction of bone tissue spontaneously with resorption over time (surgical removal is rare)
Osteomyelitis
Bone infection that is very resistant to treatment and associated with compound fractures or surgery and can lead to limb amputation
Acute arterial arrest
Arterial blood flow (kinking of artery from fracture, rupture of blood vessel from fracture, or compound fractures) distal to fracture is interrupted causing coldness of limb, paresthesia, and muscle paralysis
Neurological disturbance
Rare, but occurs right after a fracture that is a result of a nerve being stretch over a bone edge in a displaced fracture that interrupts nerve conduction
What are common sites for neurological disturbance
Shaft of humerus (radial nerve) or fracture at elbow or colles fracture (median nerve palsy)
Fat embolism
Occurs most frequently in fracture of the femoral shaft and pelvis and is when micro-particles of marrow fat escape into circulation from region of fracture causing a pulmonary embolism
Osteoporosis
Loss of bone mass, quality of bone, organic matrix and minerals causing the bones to become brittle and increased risk of fractures
What 3 groups should get bone mineral density testing by a DEXA Scan machine
1) All women and men over 65 years of age
2) Postmenopausal women and men 50-54 with risks of fractures
3) Young men or women (under 50) with a disease or condition associated with lone bone mass or loss
How are bone mineral density tests read
T-score (Standard Deviation) is calculated that describes your bone density and tells you how strong your bones are compared to average population
Below Normal: (-) sign
- Below 2.5 SD is osteoporosis
-Between 1-2.5 is osteopenia (low bone density)
- Normal bone density is no lower than 1 SD below average
What are 8 ways to prevent osteoporosis
1) diet
2) Calcium Intake
3) Vitamin D
4) Reduce alcohol consumption
5) Exercise
6) Stop smoking
7) Avoid falls
8) Medication review (eg. glucocorticoids)
What are treatments for osteoporosis
1) Diet
2) Calcium intake
3) Vitamin D
4) Reduce alcohol consumption
5) Exercise
6) Stop smoking
7) Avoid falls
8) Medication review
9) Take medications like bisphosphonates
10) Calcitonin (hormone to regulate calcium levels)
Osteogenesis Imperfecta
Congenital bone disorder that causes brittle bones (excess fractures with minimal trauma) and produces too little of Type 1 collagen
What are clinical features of osteogenesis imperfecta
Short stature (lack of bone growth in length), dental and hearing problems, scoliosis, ligamentous laxity
Rickets
Defective mineralization of calcification of bones before epiphyseal closure because of deficiency in vitamin D resulting in softening of bone and risk of deformity (mainly infants and young children)
Osteomalacia
Softening of bones in adults due to defective bone mineralization
Paget’s Disease
Increased activity of osteoclasts with resorption of bone and osteoblasts attempt to compensate (usually confined to 1-2 bones)
Osteosarcoma
Aggressive malignant cancer of the bone
