IX. Cavitation Flashcards
Definition of cavitation
Formation of vapor and gas bubbles within fluid through the local reduction of pressure
What is the cracking sound?
Liquid is stretched, pressure inside the liquid drops below the vapor pressure. Bubble formation and subsequent collapse occur and a cracking sound is heard
True or false: Z joints with recorded cavitation showed greater gapping than those that did not have recorded cavitations
True
What causes the crack?
The collapse of the vapour bubble causes the crack, not its formation
What does cavitation do to a ship’s propellers?
Cavitation “… is responsible for the erosion of ship’s propellers and the blades of hydraulic turbines, and cavitation damage in many forms of hydraulic machinery and bearings.”
What happens when cavities or vapor-filled bubbles move into higher pressure areas?
Instant collapse with high energy release and extremely large stresses (think ship’s propellers)
Over 80% of cavitation of cavitation is
Carbon dioxide
Cavitation is _______ while _______ is the sound:
Bubbles; we don’t know!
Joint cracking is related to ____________ rather than bubble collapse
Cavity formation
What are 4 observable physical effects of cavitation?
Temporary transitory increase in passive ROM
Temporary increase in the joint space
“Refractory period” where no further cracking can be
Radiolucency with subsequent joint separation
What is the refractory period?
20-45 minutes
What is the capsular ligament “snap-back”
When the capsular ligament reaches its elastic limits and snaps away from the synovial fluid, producing cavitation at the capsular-synovial interface.
Can slow forces produce cavitation?
Yes: “slow forces also produce cavitations that are similar to those produced during HVLA”
More motion means
More cavitation
True or false: the cavitation sound did appear to be associated with the magnitude or rate of the applied P-to-A forces
FALSE: the cavitation sound did NOT appear to be associated…
What is the difference between joints that cavitate and joints that don’t cavitate?
Joints that cavitate already have a greater ROM than those that don’t cavitate
In cervical rotary adjustments, what side does the cavitation occur on?
The cavitation occurs on the side opposite the adjustive contact
Where do cavitation sounds come from?
“Sounds obtained are just as frequently produced by non targeted joints in the area”
Can practitioners accurately palpate where cavitation occurs?
No: “the practitioner cannot accurately palpate where the cavitation occurs”
How many cavitation(s) occur during a single manipulative procedure when a doc aims for one specific part?
“…more than one cavitation occurs during a single manipulative procedure, suggesting that lumbar spinal manipulation is not specific.”
Can knuckle cracking cause osteoarthritis?
No coorelation
Some joints are less likely to cavitate like:
SI joint
Some joint motions are more likely to cavitation like:
Supine thoracic resisted contacts and lumbar rotation
In lumbar rotation, where is greater gapping of the Z joints found?
More gapping on the up-side than Z joints on the down-side
Some joint motions are LESS likely to cause cavitation like:
Motions which approximate joint surfaces (do NOT decrease synovial fluid pressure)
Motions which glide or slide joint surfaces (do NOT decrease synovial fluid pressure unless significant capsular stretching occurs)
What are motions which approximate joint surfaces? (3)
SI extension - sacral apex contact
Cervical extension
Cervical rotation not the side of the posterior pillar contact
What are motions which glide or slide joint surfaces? (2)
Lumbar flexion
Supine thoracic assisted flexion, lateral flexion
__ % of patients believe that popping sound was caused by vertebra returning to its normal position
49%
___% patients believed that the popping sound was caused by vertebrae rubbing against each other
23%
___% believe that the popping sound was created by gas bubbles forming in the joint
Only 9%!
___% believed that the popping sound was created by various other mechanisms
19%
How might misconceptions about cavitation sounds be harmful?
Patients assume that vertebrae are not in their normal position suggesting that 1) they believe their back is fragile 2) professional help is needed to restore normal alignment
Essentially, patients may avoid behavior that they believe may hurt their “fragile” back ie. Exercise
Why might it be harmful for practitioners to have misconceptions about cavitations / specificity / accuracy / relevancy?
Practitioners gravitate toward joints and procedures that reward us with cavitation, even if it is not what the patient needs.
Ie. #1 Patient may need cervical flexion (instead of C0-1 rotation…) which doesn’t often produce cavitations
Ie. #2 Si extension with lumbar rotation is more likely to cavitate the L5-S1 joint… presence of cavitation may deceive the underinformed practitioner into thinking successful SI adjustment was performed, even if it wasn’t.
Should the pop be the focus of the clinician or the patient during spinal manipulation?
Of course not
Manipulation versus mobilization?
They are equally effective with less risk of adverse effects with mobilization rather than manipulation.
“…cervical spine mobilization is as effective as manipulation in reducing neck pain and related disability among chiropractic patients”
Summarize notes about cavitations:
Cavitations are not reliable signs of successful adjustments
Cavitations are not accurate, not specific.
What should the goal of an adjustment be?
To promote appropriate joint function, not a noise
Does the therapeutic success of an adjustment depend on whether or not a cavitation occurs?
No
What is chiropractogenic neurosis?
Addiction to pop
“The fact that a joint pops does not mean that anything was out of place.
…Patients who believe that their vertebrae keep slipping in and out of place can become psychologically addicted to spinal manipulation and may be dissatisfied if they do not hear a pop during manipulation.”
What might be a good patient education saying?
“When I perform this adjustment, there may or may not be a popping sound.
“It doesn’t matter.
“Our goal is to normalize joint function and/or stretch the tissue around the joint and that can happen without a pop.”
