Skeletal System
What are the 4 types of bone cells?
Osteoprogenitor; involved in bone growth development and remodeling (undifferentiated cells that specialize into osteoblasts).
Osteoblasts; Bone building, synthesize and secrete organic matrix of bone, and synthesize collagen and protein to develop bone tissue.
Osteocytes; Mature bone cells, they maintain bone matrix and release calcium into the blood.
Osteoclasts; Bone chewing, responsible for the resorption of bone matrix and the release of calcium and phosphate from bone. (the PTH increases the function of osteoclasts, calcitonin and estrogen decrease the function)
Soft Tissue Injuries
Contusion: Results from direct trauma, striking a body part against a hard object.
Laceration: Skin is torn (a cut)
Hematoma: Large area of local hemorrhage
Sprain: Excessive movement of a joint, causing ligaments to tear, makes a popping sound
Strain: Stretching or tearing injury to a muscle or tendon
Compartment Syndrome
*MEDICAL EMERGENCY*
Condition of increased pressure within a limited space that compromises the circulation and function of tissues in the space.
PROCESS:
decreased blood flow -> dilation of blood vessels -> edema+increased pressure -> ischemia -> death of nerve+muscle=permanent loss of function
Clinical Manifestations:
Severe pain, diminished reflexes, loss of motor function, absent pulses
Osteoporosis:
- Age >60
- higher risk in women
- Post-menopausal women and men with low testosterone
- Caucasian and asian women
- Thin, lean, build, and low body weight
- Insufficient calcium and vitamin D intake
- Excess caffeine consumption
Osteoarthritis:
- Affects most adults by age 40
- more common in caucasians
- menopause and post-menopausal women
- obesity
Pathophysiology
Lateral deviation of spinal column
Function of Hormones and Bone Formation
Parathyroid hormone (PTH): regulates calcium and phosphate levels in the blood. Enhances intestinal absorption of calcium by activating vitamin D.
increased calcium = decreased PTH
decreased calcium = increased PTH
Calcitonin: Secreted by the thyroid gland. lowers serum calcium and reduces osteoclast activity.
Vitamin D: a steroid hormone, 2 different forms-
1) Ergocalciferol
2) Cholecalciferol
sources of vitamin D: fish, milk, UV radiation
Clinical Manifestations of Fractures
- Pain & tenderness at the site of bone disruption
- Inability to bare weight
- Swelling
- Crepitus
- Deformity (3 different types)
1) Angulation - fracture fragments tent skin
2) Rotation - fragments rotate out of normal axis
3) Shortening - Fragments slide and override each other
Thromboembolism
Occurs secondary to DVT and PE
Most symptomatic at two months after discharge
Clinical Manifestations: leg pain, edema, unexplained SOB, chest pain worse with deep breathing
Clinical Manifestations
Osteoporosis:
- silent disease
- decrease in height
- kyphosis
- weakness
Osteoarthritis:
- gradual onset
- affects joint unilaterally
- pain is aching, difficult to localize
- stiffness that resolves in 30 minutes (worse in the morning)
- 2 specific deformities:
1) Heberden's Node
2) Bouchard Node
Two Types
1) Structural
- More severe
3 Subtypes:
- Idiopathic (occurs during pre-adolescent growth spurt)
- Congenital
- Neuromuscular
2) Non-Structural
- Occurs as the spine bends to compensate for poor posture, difference in leg length, presence of tumors, or adaptation to pain.
Bone Remodeling
An ongoing process to maintain the skeleton, once growth is complete.
A sequence of bone resorption, followed by bone formation.
1st phase = resorption (osteoclasts break down bone)
2nd phase = Formation (occurs after osteoclast activity is over. Osteoblasts deposit organic matrix on the wall of the osteon canal.
(Osteons = functional unit of bone)
Classifications of Fractures
Classified by location, type, direction, and pattern.
Location: specific to long bones
3 types ->proximal, midshaft, distal
Type:
Communication with external environment
- Open/compound -> when bone fragments break through the skin
- Closed -> does not break through skin
Degree of break in continuity
- Partial/incomplete -> more common in children. EX: greenstick
- Complete -> separated into two or more pieces
Character of fracture pieces
- Comminuted -> greater than two pieces
- Compression -> two bones squeezed or crushed together.
- Impacted -> fractured fragments are wedged together.
Fat Embolism Syndrome
*LIFE THREATENING*
Results from the presence of fat droplets in the small blood vessels of the lungs, kidneys, or brain after a long bone or pelvic fracture.
(Fat emboli = released from bone marrow or adipose tissue at the site of the fracture)
Clinical Manifestations: respiratory failure, cerebral dysfunction -> Initial symptoms include a subtle change in behavior, disorientation, fever, dyspnea
Pathophysiology
Osteoporosis:
Occurs when the rate of bone resorption exceeds the rate of bone formation.
Osteoarthritis:
Cartilage breaks down with aging, becoming rough and worn away, which allows bone to rub against each other
Progressive loss of articular cartilage with synovitis, resulting from inflammation caused when cartilage attempts to repair itself.
Risk Factors
- History of neuromuscular disorders
- May develop during aging due to degenerative changes
Functions of Skeletal System
Protect and maintain soft tissues
provide stability for body
maintains body shape
Causes:
- It can happen with little or no stress
- Due to local cause (Ex: cyst or tumor)
- Systemic (Ex: Osteoporosis, pagent disease, or cancer)
Stages of Bone Healing
1) Hematoma Formation + Inflammation
- When bone breaks blood vessels around bone form clots -> hematoma facilitates formation of fibrin meshwork, which serves as a framework for influx of inflammatory cells -> fibroblast growth, and development of new capillary buds
2) Fibrocartilaginous Callous Formation
- Chondroblasts secrete collagen, which forms fibrocartilage
- Fibroblasts proliferate and invade procallous (granulation tissue).
3) Boney Callous Formation (3-4wks after surgery)
- Osteogenic cells develop into osteoblasts, producing spongy bone.
- Osteoblasts deposit bone on the outer surface of the bone distal from the fracture site.
- Fibrocartilage converts to spongy bone over time, forming bony callus.
4) Remodeling
- Osteoclasts remove dead portions of bone, and compact bone replaces spongy bone. Compact bone is laid down to reconstruct the bone shaft.
Diagnosing
- BMD (bone mineral density) assessment in all women aged 65 or earlier with risk factors
- Dual energy X-ray absorptiometry (DEXA) scan
- Serum Calcium
- Alkaline Phosphate levels
Osteoarthritis:
- X-ray to rule out fracture
- nuclear bone scan
- ESR and WBC might be elevated
Clinical Manifestations
- Spinal Curvature to one side (right side more common)
- Uneven hips and shoulders
- Difference in leg length
- Possible back pain
Bone Mineral Density
*Determinate for osteoporosis*
Determined by:
1) genetic factors
2) estrogen levels
3) exercise
4) calcium intake/absorption
5) environmental factors
Hip Fractures
Risk Factors:
- increased age
- history of osteoporosis, osteopenia
- white women, post-menopausal women
- low BMI, small body build
- use of benzodiazipines
- sedentary lifestyle
- poor nutrition
Clinical Manifestations:
- Pain in hip, upper hip, thigh, groin, lower back
- muscle spasm
- inability to move stand or walk
- leg on affected side is shorter, external rotation
Treatment:
1) Pharmacologic
opioids, ABX, NSAIDS
2) Immobilization
Buck's Traction (weight on opposite end to elevate affected leg)
3) Surgical
ORIF (orthopedic reduction internal fixation), Prosthesis
4) Physical Therapy
patient out of bed on day 1 post-op
BONUS
*primary v. secondary osteoporosis*
Primary Osteoporosis: "porous bone"
- Characterized by loss of mineralized bone mass, causing increased porosity of the skeleton and susceptibility to bone fractures.
Secondary Osteoporosis:
- Occurs with endocrine disorders, malabsorption disorders, malignancies, alcoholism, and certain medications (oral steroids), and antacids.
Treatment
Osteoporosis:
- Calcium
- Regular exercise (weight-bearing exercises are best)
- Bisphosphonates (an inhibitor of osteoclasts mediated bone resorption)
Osteoarthritis:
- Physical therapy
- Use of assistive devices
- Surgery - arthroplasty (only for severe pain)
- Pharmacologic - NSAIDS, muscle relaxants, opioids, steroid injections
Treatment
This depends on the severity of the deformity, the age of presentation, and the likelihood of progression.
Curve 10-20 degrees - wait and see
Curve 30-40 degrees - Milwaukee brace
Curve greater than 40 degrees - surgical treatment