Lecture 2: Bone And Ligament Flashcards
3 basic functions of bone
- mechanical
- metabolic
- blood production
Mechanical functions of bone
- protect body’s vital organs (trunk, pelvis, head)
- muscle ligament, organ attachment
- means of movement with muscle contractions
Metabolic bone functions
-maintains precise ca2+ and phosphorus levels (mineral homeostasis)
Blood production bone function
- RBC for oxygen delivery
- WBC for infection control
- platelets (megakaryocytes for blood clotting)
*this mostly occurs in the long bones, not much from flat bones
What type of tissue is bone
Highly specialized connective tissue
Basic elements of bone
- osteopenia cells: osteoblasts, osteoclasts, osteocytes
- collagen fibers
- ground substance: HA, glycoprotein, calcium phosphate
Two basic types of bones
Long bones and flat bones (some are irregular)
The engineering properties of bone
Strength/Stiffness
-Pound for pound, a tube is the best design for optimizing strength, resilience, and weight
-resists bending as well as steel (has some give but wont break)
Flexibility: prevents fracture with most stress
Fatigue resistant: average hip joint will sustain 1.8mil cyclical loads per year
Compact bone
Cortical bone, arranged in concentric ovals (lamellae)
Periosteum
the sheath outside your bones that supplies them with blood, nerves and the cells that help them grow and heal
- outer fibrous layer
- inner layer: osteogenic cells
- highly vascular
- highly innervated (free nerve endings= pain transmission)
Spongy bone
Cancellous bone, trabecular bone, thin intersecting plates, spicules of bone
Osteocytes
Living element of bone tissue, derived from osteoblasts
Osteoblasts
New bone formation within cellular matrix
Osteoclasts
Cells designed to resorb old bone, or damaged bone
Endosteum
The lining membrane of spongy bone. Mainly osteogenic cells
Bone formation via osteoblasts (two steps)
- Ossification
- formation of osteoid (pre bone)
- osteoblasts synthesize collagen and other proteins to make osteoid tissue - Calcification
- deposition of calcium salts in the osteoid tissue
- osteoblasts secrete the enzyme alkaline phosphates, especially following fracture
Haversian canal
The network of tubes in the bone that house nerves, arteries, veins, and lymphatic vessels
What factors impact bone remodeling
- Mechanical stress
- Level of calcium and phosphate
- hormone levels: parathyroid, calcitonin, vitamin D, cortisol, growth hormones, thyroid hormone, sex hormones
- primary cell type: osteoclasts
How does Growth during development work
It is thought that osteoblast activity is actually controls osteoclast activity and the balance is tipped toward bone formation
parathyroid hormones role in bone formation
- maintains serum levels of ionized ca2+
- increases release of ca2+ and Ph from bone
- conservation of ca2+ and elimination of ph by kidney
- intestinal reabsorption of ca2+ through vitamin D
- increases number and amplification of osteoclasts, breaks down bone, increases plasma calcium
Calcitonin role in regulation of bone formation
- inhibits release of ca2+ from bone
- increases renal elimination of ca2+ and ph which lowers serum ca2+ levels
- reduces osteoclasts activity
- inhibits calcium released from the bone and tells osteoclasts to quiet down, builds bone, decreases plasma calcium
Vitamin Ds role in regulation of bone formation
- functions as a hormone in regulating calcium
- it increases absorption of ca2+ from intestine and promotes the actions of PTH on bone
- regulates calcium; increases calcium absorption from the gut; increases PTH activity
Wolff’s law
Bone remodels in response to the mechanical stresses it experiences
-to produce an anatomical structure best able to resist the applied stress
- increase demands= hypertorphy (tuberosity, osteophytes (bone spurs)
- decrease demand=atrophy (disuse osteoporosis)
Bone stress on the proximal femur (wards triangle)
- an area of bone that breaks frequently
- it is near the femoral neck
How are bones able to support high stress
- muscles allow us to absorb more stress
- when we are tired/muscles fatigued, you are more likely to get a stress reaction or a break in the bone (there is loss of energy and an altered gait pattern)
- when muscles are weak this leads to an abnormally high bone load and then breakage
Abnormal conditions of the bone
- local death: necrosis due to fracture or disease
- increased deposition
- decreased deposition
- increased resorption
- decreased resorption
- common: increased deposition and decreased resorption
Reasons for increased deposition in bone
- work hypertrophy- Wolff’s law (increase stress leads to increase in bone deposition)
- degenerative joint disease- subchondral bone takes increase pressure and reacts by increasing bone deposition
- healing fracture: callus formation
- infections
- some bone tumors
Reasons for decreased bone deposition
- rickets (children) and osteomalacia (adults) = vitamin D deficiency
- disuse osteoporosis- Wolff’s law (immobilization post fracture, paraplegia, quadriplegia, weightlessness (astronauts))
Abnormal conditions that increase resorption (increase osteoclasts activity)
- infection within bone
- most bone tumors
Abnormal conditions that decrease resorption (decrease osteoclasts activity)
-osteopetrosis (marble bones): inherited bone disorder, decrease resorption therefore increase bone density which makes bones brittle and fracture more readily
Conditions causing an increase in deposition or an increase/decrease resorption (combo)
- systemic osteoporosis: rehab with low impact weight bearing in invoke wolfs law (happens often to neck of femur, vertebral bodies, and wrist), post menopausal women who have a decrease in estrogen and therefore a decrease in absorption of ca2+ through the gut
- rheumatoid arthritis: periarticular inflammation to which bone reacts by decreasing deposition and increasing resorption (rehab implication: do not stimulate further inflammation)
Osteopenia
- Loss in bone mineral density that is 1-2.5 standard deviations from the mean of the norm of the peak BMD of the reference young adult
- at the spine and hips, a 1 st dev decrease in bone mass is associated with 2x increase fracture risk
Osteoporosis general definition and definition of type 1 and 2
-when osteopenia reaches 2.5 SD from reference, then it is classified as osteoporosis
Type 1: post menopausal/decreased estrogen, increased osteoclastogenesis. Biggest impact is on trabecular bone
Type 2: senile- in both men and women equally. Decreased osteoblasts activity, decrease calcium absorption
Osteogenesis imperfecta
Brittle bones (very fragile), Humpty Dumpty
Paget’s disease
- long bone bending and flat bone thickening
- too much bone resorption and reformation
Fracture definition
- structural break in bone
- always associated with some degree of soft tissue injury (muscle, connective tissue, brain/spinal cord, vascular, lymphatic, nerve tissue)
The job of PTs when it comes to fractures
Minimize deterrents to healing (can’t actually speed up healing)
Fracture sites
- proximal, middle, distal third
- diaphyseal, metaphyseal, epiphyseal (only in kids)
- Intra articular
- fracture-dislocation
Types of incomplete fractures
Greenstick, buckle, torus, non displaced (impacted)
Types of complete fractures
Transverse, oblique, spiral, segmental, displaced, comminuted
Classification of fractures by severity: uncomplicated
No other serious injury or serious reaction associated with the fracture
Classification of fractures by severity: complicated
Other significant injury or serious reaction to the fracture
Ex. Pneumothorax, kidney puncture, spleen injury
Slater Harris fracture prognosis based on type
- Type I: excellent, provided blood flow in intact (separation of entire epiphysis)
- type II: Excellent, provided blood flow is intact
- Type III: ORIF usually necessary, prognosis good, so long as blood flow not disrupted
- type IV: bad, unless perfect reduction is both obtained and maintained
- type V- decidedly poor because premature cessation of bone growth almost inevitable
Clinical presentations of fractures
- bone pain
- loss of motion
- unable to bear weight (lower extremity)
- obvious deformity
- amount of discoloration
- amount of discoloration
- amount of swelling
Normal bone healing stages
- hematoma formation
- fibrocartilaginous callus formation (soft callus)
- bony callus formation (hard callus, can see on x ray)
- remodeling
Hematoma stage of bone healing (inflammation)
- hematoma facilitates formation of fibrin mesh work
- this serves as the framework for inflammatory cells, fibroblasts, and capillary buds
- time frame: begins during first 1-2 days (can be within hours)
- periosteum is key!
Fibrocartilaginous callus formation stage of bone healing (proliferation stage)
-hematoma -> granulation tissue (pro callus)
- fibroblasts proliferate and invade the pro- callus
-peaks at 2-3 weeks
-not strong enough for weight bearing
(Piezo electric effect)
Bony callus formation stage of bone healing
- consolidation of fraction fragments
- conversion of the fibrocartilaginous cartilage to bony callus
- osteoblasts are key
- begins 3-4 weeks after injury and continues for months
- weight bearing, resistance tolerated
- visible on x-ray
Remodeling stage of bone healing
- complete consolidation of fracture fragments
- osteoclasts are key
- compact bone replaces spongy bone
- thickened bone often remains in perpetuity
- may continue for years (often kids bones go back to looking normal quickly)
Two main pathways for bone healing
Intramembranous and endochondral ossification
Types of fracture imaging
Standard x rays, CT scan, MRI, bone scan
Treatments for fractures
Fracture reduction, immobilization, casting, ORIF, external fixation, bone stimulator, bone graft
General casting principle
One joint above and one joint below the break
Complications of fractures
- death from diffuse fat embolism
- avascular necrosis
- fracture blisters
- compartment syndrome (can lose a limb)
- nerve injury, neurogenic inflammation
- permanent bony deformation
- Complex regional pain syndrome (CRPS)
- DJD, stiff joint
Volkmann’s ischemic contracture
Etiology: upper extremity- supracondylar fracture, lower extremity: femur fracture
Signs/symptoms: exquisite pain with passive flex ion and extension of fingers, loss of color, parenthesis, pulslessness, paralysis, muscle necrosis/nerve injury
Myositis ossificans
Etiology: supracondylar numeral fractures (brachial is muscle), posterior elbow dislocations, trauma leads to excessive osteoblast activity
Complications following a fracture
- delayed union
- mail union (not angled right)
- non union (can lead to pseudo arthrosis, creation of joint)
Treatment: patience, bone stimulator, bone graft
Contributors to abnormal healing
- Severe damage to periostea sleeve
- loss of blood flow to fracture fragments
- too much shear during healing
- not enough time for mobilization
- too much traction during reduction
- infection in soft tissue
- infection in bone
- bone disease
- massive soft tissue damage in area
PT treatment while bone is healing
- muscle co contraction (pumping action) to avoid edema accumulation
- pendulum exercises for upper extremity
- if ORIF, ROM, gait training
- work on areas not injured to prepare for things like crutch walking (think ahead)
PT treatment once bone has reached clinical union
- PROM, AAROM, AROM
- gentle joint mobilization
- modality use: high amplitude E stim, ultrasound, TENS
- Strength development
- endurance work
- coordination, proprioception work
Bone forming tumors
- woven bone formed by neoplasticism cells
- in general, 1degree bone tumors are rare
- osteoid osteopathic and osteoblastoma: most common benign bone tumors
- osteosarcoma: most common malignant tumor of bone
Osteosarcoma
- a malignant mesenchymal tumor, most commonly is intramedullary in the long bones
- most occur in adolescence, most occur around the knee
- increased risk in older adults
- spread through medullary canal
- painful and results in necrotic bone
Osteoid osteosarcoma/ osteoblastoma
-Benign bone tumors
-similar histologically but vary in size, location, and clarity of margins
-can become malignant if given enough stimulation
-
Ligament sprain grades
- Grade 1: no loss of ligamentous integrity
- Grade 2: many fibers torn, significant c/o pain, clinical evidence of instability
- Grade 3: complete disruption, instability
- Grade 4: same as grade 3 but with a upsilon of bone
Treatment of ligament injuries
- ligaments embedded in capsule: heal well
- 1st and second degree: RICE, ROM exercise, PREs, protection from instability
-3rd and 4th degree: prolonged immobilization of surgical correction
Effects of immobilization on ligament
- decreases numbers and organizations of collagen fibers
- decreases water content of ground substance
- weakening of bone and ligament at insertion site
