Tissue Behavior, Injury, Healing, and Treatment Flashcards
What is stress used to describe?
The type of force applied
Stress is ____ related to the magnitude of force and _____ related to the unit area
directly
inversely
What is strain?
the change in length of a material due to an imposed load divided by the original length
What are the 2 types of strain?
- Linear
- Shear
Linear strain causes what?
a change in the length of a structure
Shear strain causes what?
a change in the angular relationships within a structure
What is responsible for influencing the mechanical properties of the tissue?
the concentration of proteoglycans in solution
What are the 4 regions of the load-deformation (stress-strain) curve?
- Toe
- Elastic
- Plastic
- Failure
Describe the toe region on the stress-strain curve
This is the region in which the “slack” is taken up
Describe the elastic deformation region on the stress-strain curve
This region represents the linear geometric deformation that occurs in the structure with increasingly load
In the elastic region, the stiffer the tissue, the _____ the slope
steeper
What occurs in the plastic deformation region on the stress-strain curve?
Progressive failure and microscopic tearing of the collagen fibers in the tissue results with an increasing level of stress
When tissue reaches the plastic deformation region permanent changes in the tissue result from what?
From the breaking of bonds and their subsequent inability to contribute to the recovery of the tissue
Biological tissues are anisotropic, what does this mean?
they can demonstrate differing mechanical behavior as a function of test direction
What are the 6 protective mechanisms that tissues possess?
- Crimp
- Viscoelasticity
- Creep
- Stress Relaxation
- Plastic Deformation
- Stress Response
What is crimp?
A protective mechanism of tissues in which the fibers line up in the direction of an applied force as they uncramp
In what types of tissues is crimp seen?
ligaments, tendons, and joint capsules
What is viscoelasticity?
the ability to stretch or shorten over time, and return to its original shape when a force is removed
What is creep?
the gradual rearrangement of collagen fibers, proteoglycans, and water that occurs because of a constantly applied force after the initial lengthening caused by crimp has ceased
Can tissues return to their original length once creep occurs?
They have difficulty
Describe the phenomenon of stress relaxation
Stress in a deformed structure decreases with time, while the deformation is held constant
Why does stress decrease in a structure with time, while the deformation is held constant?
Microfailures/microfractures result which decreases the stress on the structure
What is plastic deformation?
A phenomenon in which tissues remain deformed after the force is removed and they will not return to their pre-stress length
Collagen fibers can sustain _% increase in elongation before microscopic damage occurs
3
Due to the stress response improved strength in muscles, tendons, and ligaments due to exercise results from what?
An increase in the proteoglycan content and collagen cross-links
The physiological capacity of tissue is dependent on what 5 factors?
- Health of the tissue
- Age
- Proteoglycan and collagen content of the tissue
- Ability of the tissue to undergo adaptive change
- The speed at which the adaptive change occurs
Intrinsic vs. Extrinsic factors for microtraumatic injuries
- Intrinsic factors are physical characteristics that predispose an individual to microtrauma (muscle imbalance)
- Extrinsic are external conditions under which the activity is performed (training errors)
What are the 3 phases of healing and how long do they last?
- acute: 7-10 days
- subacute: 5-10 days
- chronic: 26-34 days
What are the 3 stages of tissue healing?
1) Coagulation and Inflammation Stage
2) Migratory and Proliferative Stage
3) Remodeling Stage
What occurs during the coagulation and inflammation stage?
- blood and lymph enter the wound
- there is insufficient blood flow to the area due to the capillary blood flow being disrupted
During the coagulation and inflammation stage is there vasoconstriction or vasodilation? Explain
There is first vasoconstriction for 5-10 minutes which prompts a period of vasodilation and the release of blood elements, such as platelets
What is the function of platelets during the coagulation and inflammation stage?
They secrete macrophages and fibroblasts which form a clot to prevent bleeding and infection, clean dead tissue, and nourish white cells.
The coagulation and inflammation stage is characterized by what 5 things?
- swelling
- redness
- heat
- impairment of function
- pain at rest or with AROM, or when a stress is applied to the tissue
The inflammation present during the coagulation and inflammation stage attracts what 2 WBC types?
neutrophils and monocytes
What are neutrophils?
WBCs that are filled with phagocytes which bind to and kill harmful bacteria and dead cells
What are monocytes?
WBCs that migrate into tissues and develop into macrophages which phagocytose harmful bacteria and dead cells
Edema during the and inflammation stage is due to what?
An increase in the permeability of the venules, plasma proteins, and leukocytes which leak into the site of injury causing edema
New stroma begins to invade the wound space approximately _ days after injury
4
The migratory and proliferative stage includes what 4 things?
- Capillary growth
- Granulation tissue formation
- Collagen synthesis
- Increased macrophage and mast cell activity
Which stage of tissue healing is responsible for the development of wound tensile strength?
Migratory and Proliferative Stage
The proliferation of collagen results from the action of what type of cells?
fibroblasts
Describe the process a wound takes to close
- Fibrinogen is produce first, followed by fibrin, which forms a wound matrix and walls off the wound.
- This matrix functions as a glue to hold the wound together and helps it resist infection
- Due to lack of tensile strength this matrix is replaced by a collagen matrix which facilitates angiogenesis
What happens once the collagen matrix is formed?
The fibroblasts stop producing collagen and the granulation tissue is replaced by an acellular scar, marking the end of the proliferation stage
The process of developing an acellular scar can take anywhere from - days up to __ weeks
5-10 days
10 weeks
The remodeling phase involves what?
A conversion of the initial healing tissue to scar tissue
How long can the remodeling phase last?
Up to 1 year
After the fibroblasts deposit granulation tissue what happens?
The fibroblasts are transformed into myofibroblasts, which congregate at the wound margins and start pulling the edges inward, reducing the size of the wound
What collagen types are responsible for wound contraction and visible scar formation?
collagen types I and III
The production of the new epidermis is toughened by what protein?
keratin
What causes hypertrophic scars to form?
Imbalances in collagen synthesis & degradation
What does scar contraction result from?
cross-linking of the collagen fibers
*important that adhesions do not form between the collagen and surrounding tissues
3 factors that can impact tissue and examples of each
- Intrinsic: extent of injury, edema, separation of tissue, and scarring
- Extrinsic: medications, temperature, modalities, and exercise
- Systemic: age, obesity, malnutrition, and infection
What are the 3 important factors that can impact muscle performance?
- Age
- Temperature
- Immobilization
What are the 2 primary causes of muscle injury?
excessive strain and contusion
What are 4 contributors to muscle strain?
- Inadequate flexibility and/or strength
- Dyssynergistic muscle contraction
- Insufficient warm-up
- Inadequate rehab from previous injury
A muscle contusion typically results in what?
a hematoma
Describe the 3 degrees of muscle strains
- 1st degree: There is minimal structural damage, minimal hemorrhage, and early resolution
- 2nd degree: There is a partial tear of the muscle, considered a large spectrum injury, and there is significant early los of function
3rd degree: There is a complete muscle tear which may require aspiration and/or surgery
What are the 3 phases in the healing process of an injured muscle?
- Destruction phase
- Repair phase
- Remodeling phase
Guiding principles that should guide the PT when rehabbing a muscle injury
- prevention is easier than treatment
- intervention depends on the stage of healing
- controlled mobility and activity are best
- medications and modalities are important
- use pain as a guiding factor
Is the toe region smaller in ligaments or tendons and why?
In tendons because they have more parallel collagen fibers and less realignment occurs during initial loading
How do most tendon injuries occur?
From sudden overload, repetitive loading or rapid unloading
Tendon injuries are classified as either ____ or ____.
acute or chronic
Acute tendon injuries include what types of pathologies?
- tendon ruptures
- partial tendon tears
- tendinitis
What is tendinitis?
Microscopic tearing and inflammation of the tendon tissue, commonly resulting from tissue fatigue rather than direct trauma
What are the 5 grades of tendinitis from least severe to most? Describe each
- Grade I – includes pain after activity, but does not interfere with performance
- Grade II – there is minimal pain with activity and localized tenderness
- Grade III – pain interferes with activity, but usually disappears between sessions
- Grade IV – pain does not disappear between sessions and seriously interferes with activity
- Grade V – pain interferes with ADLs, symptoms often chronic and there is altered muscle function
What are the 3 chronic tendon injuries?
- Paratenonitis
- Tenosynovitis
- Tendinosis
What is Paratenonitis?
an inflammation of the outermost layer of the tendon
What is Tenosynovitis?
a pathology in which the outermost layer of a tendon and the tendon sheath are inflamed
What is tendinosis?
An intratendinous degenerative lesion without an inflammatory component
What are the 3 phases in the healing process of an injured tendon?
- Inflammation
- Repair
- Remodeling
What is the most important thing to enforce during the treatment of a tendon?
Judicious application of force must be used to encourage the new collagen fibrils to align in the direction of the force application
What is the major difference between the treatment of tendinitis and tendinosis?
Controlling inflammation is the focus of tendinitis, whereas loading based rehab is the focus of tendinosis
During the rehabilitation of a tendon you should do ____ repetition, ____ load exercises
high rep
low load
Damage to a ligament results in what?
A loss of normal kinematic relationships between the connected bones
With external loads, the ligaments that are ____ at the time of impact will most-likely be injured
taut
3 Characteristics of Ligament Injuries
- history of trauma
- point tenderness
- joint effusion
How can you tell the differences between grade II and III ligament injuries?
With grade III injuries there is significant joint gapping with the application of the stress test
Do intra- or extra-articular ligaments heal slower and why?
intra-articular ligaments do not heal as well secondary to decreased blood supply and synovial fluid
What are the 4 phases in the healing process of an injured ligament?
- Hemorrhagic
- Inflammatory
- Proliferation
- Remodeling and Maturation
Ligament repair can take up to how many years to repair?
3 years
What are 2 important rehab considerations to keep in mind when treating ligament injuries?
- Force must be applied to the ligament to help develop strength in the force direction
- Immobilization should be minimized
What are the 3 distinct areas or zones present with joint mobility?
- Neutral Zone: crimp is taken up
- Elastic Zone: from crimp into PROM
- Plastic Zone: deformation of tissue
Define joint hypomobilty
movement of the joint is less than that considered normal or when compared to the uninvolved side
Define joint hypermobility
movement of the joint is more than that considered normal or when compared to the uninvolved side
Joint hypermobility can be generalized or localized. Localized hypermobility usually occurs because of what?
neighboring stiffness
commonly found in adjacent spinal levels
Define an unstable joint
This is a potential or real pathologic state of the joint that involves a disruption of the osseous and ligamentous structures of that joint as the result of some applied external force
Results in pain, weakness, and transitory deformity
What are the 3 types of clinical joint instability?
- Translational
- Anatomical
- Functional
Describe translational joint instability
refers to a loss of control of the small, arthrokinematic joint movements that occur when the patient attempts to stabilize the joint during movement
Describe anatomical joint instability
refers to excessive physiological movement in the joint which leads to abnormal patterns of coupled and translational movements
Describe functional joint instability
occurs when the severity of the instability adversely affects a patient’s function
What are 2 important factors to keep in mind when treating a joint injury?
- First you must ifferentiate between patients with generalized hypermobility vs. localized hypermobility
- Also be sure to address any neighboring hypomobility
How does articular cartilage receive its nutrients?
By way of diffusion from the synovial fluid
Chondrocytes in loaded joints experience what 3 kinds of forces?
- hydrostatic compressive
- tensile
- shear
Which force is believed to maintain healthy cartilage the most?
hydrostatic compressive
Is immobilization healthy for articular cartilage?
No, it results in degenerative changes
Articular cartilage consists of what 2 phases?
- Fluid phase: water
- Solid phase: ECM
5 factors that lead to AC breakdown
- Imbalance between ECM synthesis and degradation
- Stress deprivation (immobilization)
- Developmental etiologies leading to abnormal force transmission (genu valgum/varum)
- Joint surface incongruously and joint instability
- Disease (rheumatoid arthritis)
Describe the 3 types of AC injury
- Type I (superficial): microscopic damage to the chondrocytes and ECM
- Type II (partial thickness): microscopic disruption of the AC surface
Type III (full thickness): disruption of the AC with penetration into the subchondral bones, which produces an inflammatory response
The body’s ability to repair articular cartilage is dependent upon what?
The depth of the lesion. If the injury does not penetrate the subchondral bone, the AC will become necrotic and will not heal
How should you treat an articular cartilage injury?
Frequent exercise to increase chondrocyte size and strength
What are the 3 elements of bone? Which one distinguishes it from other connective tissues?
- organic
- mineral***
- fluid
Bone is strongest in _____ and weakest in _____.
compression
tension
Describe the 5 types of bone fractures
- Avulsion: piece of bone is pulled away
- Transverse: horizontal fracture
- Oblique: angled fracture
- Spiral: due to a twisting type motion
- Comminuted: multiple fragments
What is the major difference between bone healing and the healing of other tissues?
Repair is by the original tissue, not scar tissue in bones
What are the 2 types of fracture healing?
1) primary cortical healing
2) secondary callus healing
Describe primary cortical healing
Involves a direct attempt by the cortex to reestablish itself once it has become interrupted. Bone on one side must unite with bone on the other side
Describe secondary callus healing
Involves responses in the periosteum and external soft tissues with the subsequent formation of a callus
How do the majority of bone fracture heal?
by way of secondary callus healing
What are the 4 phases of bone healing?
1) Hematoma formation
2) Soft callus formation
3) Hard callus formation
4) Remodeling
What is angiogenesis?
The outgrowth of new capillaries from existing vessels which will eventually lead to osteogenesis
According to ____ law bone remodels along lines of stress
Wolff’s
Do hormones and environment have an impact on osteoblastic and osteoclastic activity?
Yes
What types of modalities can be used to accomplish a quicker and more complete healing of fractures?
- Pulsed Electromagnetic Fields (PEMF)
- Ultrasound
- Direct Current Stimulation
- Demineralized Bone Matrix (DBM)
What are the 3 surgical procedures performed to stabilize fractures?
- Percutaneous pinning
- External fixation
- Open reduction and internal fixation (ORIF)
What are a few clinical signs of DVT?
- swelling of the LE
- tenderness
- feeling of cramping
- positive Homan’s Sign (pain with DF)
- vascular prominence
- elevated temperature
- tachycardia
- inflammation
- discoloration of the extremity
What are a few clinical signs of a pulmonary embolus?
- chest pain
- chest wall tenderness
- back pain, shoulder pain
- upper abdominal pain
- syncope
- hemoptysis (coughing up blood)
- shortness of breath
- painful respiration
- wheezing
- any new cardiac arrhythmia
What are the 4 Detrimental Effects of Immobilization?
- Cartilage degeneration
- Decreased mechanical and structural properties of the ligaments
- Decreased bone density
- Weakness or atrophy of muscles
Disuse atrophy begins within _ hours of the start of bed rest
4
