MSK Mod 1A Flashcards
Classification of bone types (4)
- Long bones
a. ex: humerus, femur, tibia, etc.. - Short bones
a. Tend to be equal in both dimension…cuboidal shape
b. ex: carpals of wrist, tarsals of foot - Flat bones
a. protective function
b. ex: skull - Irregular bones
a. ex: vertebrae, facial bones
Characteristics of Long Bone (4)
A. Diaphysis 1. primary ossification center 2. body of bone B. Metaphysis 1. flattened portion of the diaphysis C. Epiphysis 1. secondary ossification center (develop after birth) D. Epiphyseal Plate 1. cartilagenous growth plate between diaphysis and epiphysis
2 Types of Bone
compact (cortical) and spongy (cancellous, trabecular)
Cortical – “compact” bone
- Forms 80% of the human skeleton
- Slow turn over rate
- Dense, tightly packed osteons with haversian canal system
- Haversian system (aka Osteon)
a. Haversian canal (central canal) – each canal contains blood vessel and nerve that communicate with perisoteum
b. Concentric layers of bone surround the canal – lamelle
c. Osteocytes found within concentric layers
d. Volkman’s canal – “horizontal” canal system connecting to periosteum
Cancellous bone – trabecular or spongy bone
- 20% of skeletal mass
- Less dense but “large” surface area
- Higher turnover rate
- Undergoes remodeling according to line of stress
- Wolff’s Law = increased mechanical stress will increase bone density
Periosteum
A. Thin, double-layered, tough fibrous membrane that surrounds the bone
B. Surrounds all of bone except at ligament or tendon insertion sites
Periosteum Outer and Inner Layer
C. Outer layer contains…
1. Capillaries and nerves
D. Inner layer contains…
- Sharpey’s fibers anchor periosteum (as well as tendons and ligaments) to the cortical bone
- Difficult to separate the periosteum from the bone
- If active bone formation then:
a. inner layer contains osteoblasts - If inactive bone formation then:
a. the inner layer contains fibroblasts that can become osteoblasts if new growth needed
Bone Marrow Consists of? (6)
- Blood vessels
- Nerves
- Mononuclear phagocytes
- Stem cells
- Blood cells in various stages of differentiation
- Fatty tissue
2 Types of Bone Marrow in adults
- Red (active) bone marrow
a. Not all bones have active marrow
b. Pelvic bones, vertebrae, cranium and mandible, sternum and ribs, proximal femur and humerus
c. Found in trabecular or spongy bone regions - Yellow (inactive) bone marrow
a. Yellow represents more of fatty cells
b. Found in medullary cavity of long bone
Blood Supply to Bone
A. Nutrient arteries are primary source of blood
1. Usually enter middle of diaphysis
B. Epiphysiseal and metaphyseal arteries
C. Periosteal capillaries
D. Clinical: Blood supply is critical for fracture repair and to maintain bone health
Bone Remodeling
A. General healthy remodeling occurs in both cortical and cancellous bone
B. Occurs throughout life
C. Balance between osteoblasts and osteoclasts
D. osteoporosis = osteoblast activity < osteoclastic activty
5 Phases of Remodeling
- Activation
- Resorption
- Reversal:
- Formation
- Quiescence:
Phase 1 of Bone Remodeling
- Activation
a. Stimulus: hormone, drug, or physical stimulus
b. Action: stimulus activate resting osteoblasts to signal activation of osteoclastic activity
Phase 2 of Bone Remodeling
- Resorption
a. 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
Phase 3 of Bone Remodeling
Reversal
a. Action: macrophages “clean-up” the site and prepare it for laying down new bone
Phase 4 of Bone Remodeling
Formation
a. Action: osteoblasts lay down new bone in resorption cavity
b. Compact bone:
• Bone is laid down in concentric layers until small canal is formed (haversian’s canal)
• Haversion systems are constantly broken down with new ones being formed
c. Cancellous bone:
• Trabeculae are broken down and new ones formed
Phase 5 of Bone Remodeling
- Quiescence:
a. Action: osteoblasts “rest” and are now “bone lining cells” on the newly formed bone surface
Three basic etiological classifications of fractures
a. Sudden traumatic fracture • Single episode of excessive force b. Stress or fatigue fracture • Repetitive episodes of “normal” force c. Pathological fracture • “Normal” force on abnormal bone
Condition of the Soft Tissue with Fractures (2)
a. Closed fracture
• fx not exposed to the external environment
b. Open fracture
• fx exposed to the external environment
Deformities of the Fracture
a. Displacement (translation) - describes the position of the distal fragment
• Ant/post, medial/lateral
b. Rotation – IR/ER with observation
c. Shortening of the fracture – ends of the fx overlap
d. Angulation – direction in which the distal fragment “points”
• Ex: lateral/medial “angulation”
Fracture classifications…many “systems” of description
Anatomical Location of the Bone Region of the Bone Direction of the Fracture Line Condition of the bone Condition of the Soft Tissue Deformities of the Fracture
Condition of the Bone
a. Comminuted – fx with 3 or more fragments
b. Pathological – fx in area of pre-existing bone disease
c. Incomplete – fx does not span entire cross section of bone, bone is not broken into separate segments
d. Segmental – fx middle fragment of bone surrounded by proximal and distal segments
e. Butterfly segment – similar to segmental except fx doesn’t span the entire cross section of bone
f. Stress fracture – small fx caused by repetitive loading of bone
g. Avulsion fracture
Avulsion Fx
portion of bone is separated from bone, caused from pulling of tendon or ligament at the insertion site
3 Phases of Bone Healing
Inflammatory Phase
Reparative Phase
Remodeling Phase
