IX. Cavitation

Question 1

Definition of cavitation

Answer 1

Formation of vapor and gas bubbles within fluid through the local reduction of pressure

Question 2

What is the cracking sound?

Answer 2

Liquid is stretched, pressure inside the liquid drops below the vapor pressure. Bubble formation and subsequent collapse occur and a cracking sound is heard

Question 3

True or false: Z joints with recorded cavitation showed greater gapping than those that did not have recorded cavitations

Answer 3

True

Question 4

What causes the crack?

Answer 4

The collapse of the vapour bubble causes the crack, not its formation

Question 5

What does cavitation do to a ship’s propellers?

Answer 5

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.”

Question 6

What happens when cavities or vapor-filled bubbles move into higher pressure areas?

Answer 6

Instant collapse with high energy release and extremely large stresses (think ship’s propellers)

Question 7

Over 80% of cavitation of cavitation is

Answer 7

Carbon dioxide

Question 8

Cavitation is _______ while _______ is the sound:

Answer 8

Bubbles; we don’t know!

Question 9

Joint cracking is related to ____________ rather than bubble collapse

Answer 9

Cavity formation

Question 10

What are 4 observable physical effects of cavitation?

Answer 10

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

Question 11

What is the refractory period?

Answer 11

20-45 minutes

Question 12

What is the capsular ligament “snap-back”

Answer 12

When the capsular ligament reaches its elastic limits and snaps away from the synovial fluid, producing cavitation at the capsular-synovial interface.

Question 13

Can slow forces produce cavitation?

Answer 13

Yes: “slow forces also produce cavitations that are similar to those produced during HVLA”

Question 14

More motion means

Answer 14

More cavitation

Question 15

True or false: the cavitation sound did appear to be associated with the magnitude or rate of the applied P-to-A forces

Answer 15

FALSE: the cavitation sound did NOT appear to be associated…

Question 16

What is the difference between joints that cavitate and joints that don’t cavitate?

Answer 16

Joints that cavitate already have a greater ROM than those that don’t cavitate

Question 17

In cervical rotary adjustments, what side does the cavitation occur on?

Answer 17

The cavitation occurs on the side opposite the adjustive contact

Question 18

Where do cavitation sounds come from?

Answer 18

“Sounds obtained are just as frequently produced by non targeted joints in the area”

Question 19

Can practitioners accurately palpate where cavitation occurs?

Answer 19

No: “the practitioner cannot accurately palpate where the cavitation occurs”

Question 20

How many cavitation(s) occur during a single manipulative procedure when a doc aims for one specific part?

Answer 20

“…more than one cavitation occurs during a single manipulative procedure, suggesting that lumbar spinal manipulation is not specific.”

Question 21

Can knuckle cracking cause osteoarthritis?

Answer 21

No coorelation

Question 22

Some joints are less likely to cavitate like:

Answer 22

SI joint

Question 23

Some joint motions are more likely to cavitation like:

Answer 23

Supine thoracic resisted contacts and lumbar rotation

Question 24

In lumbar rotation, where is greater gapping of the Z joints found?

Answer 24

More gapping on the up-side than Z joints on the down-side

Question 25

Some joint motions are LESS likely to cause cavitation like:

Answer 25

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)

Question 26

What are motions which approximate joint surfaces? (3)

Answer 26

SI extension - sacral apex contact

Cervical extension

Cervical rotation not the side of the posterior pillar contact

Question 27

What are motions which glide or slide joint surfaces? (2)

Answer 27

Lumbar flexion

Supine thoracic assisted flexion, lateral flexion

Question 28

__ % of patients believe that popping sound was caused by vertebra returning to its normal position

Answer 28

49%

Question 29

___% patients believed that the popping sound was caused by vertebrae rubbing against each other

Answer 29

23%

Question 30

___% believe that the popping sound was created by gas bubbles forming in the joint

Answer 30

Only 9%!

Question 31

___% believed that the popping sound was created by various other mechanisms

Answer 31

19%

Question 32

How might misconceptions about cavitation sounds be harmful?

Answer 32

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

Question 33

Why might it be harmful for practitioners to have misconceptions about cavitations / specificity / accuracy / relevancy?

Answer 33

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.

Question 34

Should the pop be the focus of the clinician or the patient during spinal manipulation?

Answer 34

Of course not

Question 35

Manipulation versus mobilization?

Answer 35

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”

Question 36

Summarize notes about cavitations:

Answer 36

Cavitations are not reliable signs of successful adjustments

Cavitations are not accurate, not specific.

Question 37

What should the goal of an adjustment be?

Answer 37

To promote appropriate joint function, not a noise

Question 38

Does the therapeutic success of an adjustment depend on whether or not a cavitation occurs?

Answer 38

No

Question 39

What is chiropractogenic neurosis?

Answer 39

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.”

Question 40

What might be a good patient education saying?

Answer 40

“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.”