Warm Water Pool Therapy for:

Jeffery Allen PT. OCS
Board Certified Orthopedic Clinical Specialist

Rationale for Use of Water
There is no question that the water offers a therapeutic environment which can be harnessed by a skilled therapist to permit activities for the postoperative patient. This environment is created because of the unique properties of water and it is both difficult and clinically impractical to achieve a similar environment on land. Take a moment to examine these properties one-by-one.

Buoyancy
Archimedes' principle states: "when a body is wholly or partially immersed in a fluid, it experiences an upthrust equal to the weight of fluid displaced."

Basically, this upthrust, or buoyancy can be used to provide either assistance or resistance to movement of the body. It all depends on the position of the patient's body.

The human body has elements which tend to sink (dense muscle) and elements which tend to float (fatty tissue and air-filled lungs). This tendency to float counterbalances gravity and supports the body, resulting in an apparent reduction in weight.

This reduction in weight can provide relief from compressive forces on painful joints. It is therefore possible for the postoperative patient to stand, even walk, with reduced pain without external support or abnormal protective mechanisms in the water.

Thus, the patient can initiate "normal" weight bearing tasks such as gait, transfers, and balance drills immediately after surgery and offset any deconditioning effects of immobility or reduced movement.

Even better? This reduction in compression creates an environment in which weight bearing and joint compression can be applied in a graded or progressive manner by the therapist. Weight bearing may be systematically reduced by increasing the amount of the body submerged.

Static (standing) immersion at the level of the anterior superior iliac spine (ASIS) reduces weight 40%-56% of normal. Be careful though: all bets are off when the patient moves. During slow walking, patients must be immersed to the clavicle to reduce weight bearing to 50%, and during fast walking, patients must be immersed deeper than the xiphosternum in order to reduce weight that much.

In conclusion, buoyancy can be used to create:

Buoyancy can also promote ease of handling of the large or heavy patient and allow access to body parts which would be inaccessible if the patient was positioned on a plinth or chair.

Hydrostatic Pressure
Pascal's Law states that "Fluid pressure is exerted equally on all surfaces of an immersed body at rest at a given depth".

In essence, hydrostatic pressure increases the pressure on the outside of an immersed standing body, resulting in:

This means the postoperative patient can be relieved of some of the potential for swelling and clotting problems associated with surgery.

Viscosity
Viscosity is nothing more than the inherent friction that exists between molecules of a liquid which cause a resistance to flow. Water is more viscous than air , thus, it takes more force to push through water molecules than to push through air molecules.

Additionally, the faster an object is pushed through the water, the more turbulence is created and this creates additional resistance to movement.Keep in mind that the postoperative patient has probably already lost a great deal of proprioception for a number of reasons.

First, his joint has been worn-down, perhaps to bone-on-bone and has lost its normal weight-bearing feedback capacity.

Second, the joint is further traumatized by surgical intervention (perhaps even sacrificing additional Golgi tendon organs and muscle spindles to the surgeon's blade). It seems likely that movement in water can offer patients exaggerated input from the environment -- perhaps resulting in enhanced proprioception.

Flow
When an object moves through a fluid, there is an increase in the pressure in the front of an object combined with a reduction in pressure in the back. This results in the water wanting to move from an area of high pressure to an area of lower pressure.

The area of "negative pressure" is known as the wake. Eddy currents form in this wake and "drag" the object back. The negative pressure (or drag) behind a moving object (the wake) is responsible for 90% of the impedance of movement. Surprisingly, the bow wave (the positive pressure in front of the object) is only responsible for 10% of the impedance.

The principle of flow can be used therapeutically to increase (or decrease) the force necessary to push through the water. This property can be used to create a progressive resistive exercise program that is three-dimensional, velocity-specific, and safe to perform.

Refraction
Refraction is the prism effect that is evident when looking from an air medium to a water medium. Light bends when its rays move from a more dense to a less dense substance.

Most of the "therapeutic" effects of refraction are negative. Refraction decreases depth perception and makes the pool seems shallower. It alters visual cues for both patient and provider. Patient's limbs seem distorted (bent away), and items seem high and to the right, thus making visual feedback and monitoring is more difficult.

For the postoperative patient, it is possible to use refraction therapeutically. For instance, while immersed, a patient with a habitual visual method of joint placement (e.g. someone who looks at his feet to walk) may be forced to use his proprioceptive system instead.

Thermal Shifts
At temperatures above "thermoneutral" (approximately 93° Fahrenheit at rest), body temperature increases due to the reduced ability of the body to dissipate heat through the skin. Thermal energy (heat) is exchanged between water and the body and between air and the body.

Energy exchange between a submerged body and the water occurs through both convection and conduction. Thermal energy is also exchanged between the body and the air through radiation and evaporation -- methods which become more critical if the total body is immersed and the water temperature prevents heat dissipation from occurring during aquatic exercise. 

Immersion in water warmer than the skin will result in a rise in superficial tissue temperature which creates a palliative effect like that experienced during the therapeutic use of paraffin, Fluidotherapy® and moist heat.

Immersion in thermoneutral water will produce a generalized relaxation effect similar to that experienced with swaddling or bundling of a body part.

Special Considerations for the Patient who has Undergone Hip Surgery
Even though the water is an ideal environment to tackle many problems inherent in the postoperative population, there are still considerations of which must be considered.  We always take a moment to examine the following to ensure you will have the best care with your aqua therapy program.

Precautions and Contraindications
There are many potential precautions to consider for the s/p hip surgery patient. Here are several things to consider when taking this population into the pool:

Techniques and Specifics for Designing Programs
Therapists must treat the patient who has just undergone hip surgery carefully. There are many considerations when designing an aquatic therapy program for this population. For example:

Goals for Aquatic Therapy
The therapist who is not familiar with working with patients who are s/p hip surgery may set unrealistic goals. It is important to realize that exercise in water can be a powerful tool for the rehabilitation of hip dysfunction.

Goals that would be appropriate for hip patients:

Benefits of Aquatic Therapy
Therapists cannot choose to place patients in the water simply because they believe in the "power of the pool". It is important for therapist to demonstrate through documentation that they have a solid rationale for placing the s/p surgical patient in the water. Typical benefits are:

Conclusion
 Therapists who combine excellent manual therapy skill with work in the water, have the best of both worlds to offer patients with hip dysfunction. You see the possibilities inherent in gravity, yes; but you delight in the possibilities intrinsic to buoyancy, viscosity, turbulence and pressure. The universe expands: you can offer our patient air and water, an integration of effort and ease.

References:

Allen Physical Therapy
"Hands on Treatment, Every Patient, Every Visit"
248-437-2322
South Lyon, Michigan
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