Extracorporeal Shock-wave Flashcards
What is ESWT
The application of pressure mechanical waves outside the body (extracorporeal) that violently impact (shock) biologic tissues for therapeutic purposes
(NOTE: mechanical energy is absorbed by soft tissues and leads to physiologic and therapeutic effects).
What is shock wave
Low to large amplitude wave formed by the sudden mechanical compression of the medium
What is a mechanical wave
A wave that is an oscillation of matter and therefore transfers energy through a medium
What are the two types of shock waves devices
Focused shock waves (f-ESWT)
Unfocused/ Radial shock waves (r-ESWT)
(NOTE: some devices have both)
What different methods produce f-ESWT
Electrohydraulic : force of liquid pressure
Electromagnetic : electric and magnetic fields come in contact
Piezoelectric : using crystals to convert mechanical energy ➡️ electrical energy
What method is used to produce r-ESWT
Pneumatically (ballistic) : compressed air
Delivery of f-ESWT VS r-ESWT
F-ESWT : small and precise locations
R-ESWT: unfocused larger locations
(NOTE: this is due to how they were produced)
(Ex: R-ESWT produced pneumatically)
(Ex: look at picture for f-ESWT production)
Which device delivers high energy / low energy?
F-ESWT: high energy
R-ESWT: low energy
Discuss the rationale for ESWT usage
Provide examples
ESWT is:
- safer
- noninvasive
- good alternative to surgical interventions
Example:
- lithotripsy (f-ESWT)
- orthotripsy (f-ESWT & r-ESWT)
What is lithotripsy used for?
What type of shock wave is involved ?
To break kidney and ureteral stones
F-ESWT
What is orthotripsy used for?
What type of shock wave is involved ?
Stimulates healing process of tendons and bones for chronic and recalcitrant tendinopathies and delayed or nonunion fractures
F-ESWT & R-ESWT
Penetration depth of f-ESWT and r-ESWT
F-ESWT : deep (more than 5 cm)
R-ESWT : superficial (less than 5 cm)
Localization method of f-ESWT and r-ESWT
F-ESWT: image guiding systems (ultrasound, fluoroscopy, X-rays)
R-ESWT (palpation/ manual localization using pistol-like applicator)
Waveforms are characterized by two phases . What are they ?
Compressive phase
Tensile phase
Compressive and Tensile phases and Time courses
in F-ESWT vs R-ESWT
F-ESWT :
- HIGHER compressive and tensile pressures
- SHORTER time courses
R-ESWT:
- LOWER compressive and tensile pressures
- LONGER time courses
Reading compressive vs tensile pressure on graph
Compressive pressure:
- Positive pressure (P+): pressure during positive compressive phase
- Positive peak pressure (Pp+): maximum +ve peak pressure
Tensile pressure:
- Negative pressure (P-): pressure during negative tensile phase
- Negative peak pressure (Pp-): maximum -ve peak pressure
Units for compressive and tensile pressures
Megapascal (Mpa) or Bar
10 bar = 1 Mpa
Describe the amplitudes of P+ and P-
Amplitude of P- = 10% of amplitude of P+
Compare compressive pressures for f-ESWT and r-ESWT
F-ESWT can reach compressive pressure 120x larger than r-ESWT
What is rise time?
What is pulse duration ?
Compare the rise time and pulse duration for f-ESWT and r-ESWT
Rise time (RT):
- Time interval during which P+ rises from baseline to peak value
Pulse duration (PD):
- Time interval between the beginning and ending of the compressive phase
F-ESWT PD: <0.5 μs
R-ESWT PD: <500 μs
The mechanical/acoustic energy contained in a shock wave is expressed in what unit?
Millijoules (mJ)
What is energy flux density EFD
How is it calculated
What is the unit of EFD
Classification of EFD levels
- A measure of shock wave energy concentration or density
- The amount of mechanical acoustic energy per unit area per shock
EFD = Energy / Area
Unit: mJ/mm²
Can be classified as: low, medium, high
Compare EFDs between f-ESWT and r-ESWT
F-ESWT have larger EFDs than r-ESWT because:
- they contain more energy (E ⬆️ )
- distributed over smaller area (A ⬇️ )
Calculations of EFDs is suitable for ___________ and do not accurately represent _________
F-ESWT
R-ESWT
(NOTE: more accurate representation of r-ESWT is to report pressure level in bar or Mpa)
Range of number of shocks per treatment
Generally may range between 1000 to 4000
Range of shock frequency
Between 4-5 Hz ( use lower if painful)
Or
15-20 Hz when using radial
Number of treatments
Between 1 and 4
Difference between applicators for f-ESWT and r-ESWT
F-ESWT applicators:
- larger and more difficult to manipulate
R-ESWT applicators:
- smaller and easier to manipulate
Why do we need coupling media
What are the coupling media for f-ESWT and r-ESWT
A coupling medium is required for mechanical energy, created by the shockwaves, to be transmitted and absorbed by soft tissue
(Maximizes acoustic transmission)
F-ESWT :
- Adjustable dome membranes that are filled with either gas, water, gel
- local analgesics to minimize pain during therapy but may reduce therapeutic effectiveness
R-ESWT :
Standard aqua-sonic gel
Compare the propagation of f-ESWT and r-ESWT
F-ESWT : focused (convergent) - smaller, deeper areas
R-ESWT: radial (divergent) - larger, superficial areas
Therapeutic effects
Indication of ESWT
Shoulder, elbow, Achilles, and patellar tendinopathies
Shoulder calcific tendinitis
Plantar fasciopathy
Chronic heel pain
Nonunion and delayed-union bone fracture
Osteonecrosis
Contraindications of ESWT (hint: 7)
Gas-filled tissues i.e lung & intestines (severe tissue damage)
Uterus (disrupts fetal development)
Electronic implant (interference)
Blood coagulation therapy (bleeding)
Acute injury (increases inflammation)
Large vessel and nerve (damage sensitive tissue)
Epiphyseal plate (alters normal bone growth)
Risks of ESWT and why?
Pain
Swelling
Discoloration
Bruising
Repetitive pressure impacts cause local tissue microvascular damages that may trigger these risks.
