by Dean J. Bender and Albert Fliss, PhD
Aim: A review of the misconceptions regarding the use of compression therapy on the feet, the current knowledge on the subject and further research needed to better understand this critical issue.
Misconception: The compression level required for the foot is equal to or greater than that of the ankle.
Discussion: Over the years, working with a variety of healthcare professionals from around the world, one of the largest misconceptions regarding the use of compression therapy is with regards to the compression applied to the feet. A general misconception exists that the compression level applied to the foot must be equal to or greater than the compression level at the ankle, otherwise a swollen foot will result.
For the most part, this misconception has developed from a combination of several factors. First, logic would dictate us to think that compressing only part of a limb will result in a constriction point (tourniquet), and fluid distal to this point will be prevented from flowing up the leg resulting in swelling. Second, we are taught that compression must be applied in a gradient fashion to promote fluid flow from distal to proximal, that stockings are designed to be gradient and used with proper bandaging techniques to achieve the preferred gradient. And third, we have a lack of knowledge of the specific design parameters for “gradient compression stockings,” due to a limited description of the product from the manufacturers. Typically, stocking manufacturers provide the following information on their label
- Average compression level at the ankle (i.e. 20-30 mmHg)
- Whether the garment is gradient or not
- Stocking size
Unfortunately, the description does not provide information regarding the compression applied aside from the ankle zone. What is the compression level in the calf or thigh? And, more specifically, what is the average compression applied to the feet?
As such, over the years we have made our own conclusions as to how the stocking is actually designed. So the issue-becomes our understanding, or perhaps more accurately, the lack of understanding as to what “gradient” means in regards to a compression stocking or bandage system.
In regards to compression stockings, existing design standards such as the RA L and ASQUAL dictate that a gradient is required and is defined as a decrease in compression level from the ankle to the calf and further to the thigh. Our understanding is that the proximal pressure should always be lower than the distal pressure. These specifications even provide the percentage decrease required at each level as we move up the leg. For example, a Class II RA L compression stocking gradient profile is:
The current standards are quite explicit in most regards, with the exception of any requirement for the compression level for the foot. There is not even a comment that any level of compression is even required for the foot.
And so what has transpired over the years is the general misconception that a compression stocking provides a greater or equal pressure level on the foot versus the ankle in order to maintain the gradient throughout the stocking.
When we think of alternates to stockings, such as compression bandaging, we find that proper application requires the ability to provide consistent tension in the bandage as we apply it to the limb. And we understand that the compression level will decrease as we move proximally from the ankle due to the increasing limb circumference (LaPlace’s Law). However, we tend to overlook the fact that when we are bandaging the foot we are typically encountering a radius of curvature greater to that of the ankle across the top of the foot. Thus further perpetuating a belief that a gradient is from the foot upwards!
This is what we currently know and don’t know regarding compression applied to the feet:
- We cannot readily tell the level of compression that is actually applied to the feet.
- We do not know where in the foot compression is important. What about compression of the heel area?
- We do not know a defined point for measuring compression in the foot. Should it be the top of the foot? Under the arch?
- We do know that what we currently apply in regards to compression stockings, bandages or adjustable wraps seems to be effective.
- We also know most clinicians can share experiences where swelling of the foot occurred in a patient with excessive edema when the leg is compressed and the foot is not. This swelling is often seen when edema is associated with surgery or trauma of the leg.
The Facts: A review of designs from the major compression stocking manufacturers around the world revealed that the compression levels currently provided in the foot portion of a stocking is lower than the ankle pressure. While the manufacturers would not provide specific compression design parameters for the foot, across the board the design objective is to provide the same general level of compression as is provided in the calf, which is 50- 80% of the ankle pressure.
Additionally, Professor H. Partsch measured compression levels under a RA L Class II elastic stocking revealing that the pressures at the dorsal and ventral measuring points of the foot (x position in chart below) are indeed in the same range as the calf measurements. Also of note is that the lateral and medial measurements are significantly higher, an effect of the smaller radius’ associated with the side of the foot. This does bring our attention to the potential for too high of a compression level in these areas of the foot and possible detrimental consequences.
Thus, applying the RA L gradient profile for a typical gradient compression stocking with an average ankle compression of 25 mmHg, we see that the expected compression levels are from the foot to the thigh are:
We have learned over the years from practical experience and observation that the typical compression “gradient” profile achieved with stockings, compression bandages and adjustable wraps is more than adequate to deal with edema in the foot even though a true gradient is not achieved.
Now that we have a clearer understanding of what we are achieving when we compress the leg with stockings, we are now presented with the question: Do we always need to compress the feet?
Clinical Insights: When we consider the need to compress the feet, we need to first understand what we know about the anatomy and physiology of venous system of the foot. In 1996, Dr. John White1 reported on the mechanisms for venous outflows from the foot as measured using phlebograms; “The plantar venous plexus was composed of one to four large veins (mean, 2.7 veins) within the plantar aspect of the foot. The diameter of these veins was 4.0 +/- 1.2 mm. The veins coursed diagonally from a lateral position in the forefoot to a medial position at the level of the ankle, spanning 75% of the foot arch. Prominent valves were recognized within the plantar veins in 22 of 50 patients. The plexus coalesced into an outflow tract of one to four veins (mean, 2.5 veins) that flowed exclusively into the posterior tibial venous system. Small accessory veins that drained the plantar surface of the forefoot flowed into either the posterior tibial or peroneal veins.” Additionally, he demonstrated that mechanical compression of the plantar venous plexus produced a mean peak velocity in the posterior tibial veins of 123 +/- 71 cm/sec, as measured using duplex ultrasonographic scan.
In The Venous System in Health and Disease 3rd Ed., Gardner & Fox described the mechanism for venous pump action in the foot as the result of flattening of the plantar arch. Furthermore, in 2007 Elsner demonstrated through cadaver studies that venous drainage of the plantar venous sinus is fibrotically bound to the first metatarsophalageal (MT P) joint capsule and that mobilization of the MT P joint led to compression and emptying of the veins.2 Compression of the vein results from the vein being stretched longitudinally during ambulation or dorsal flexion, not by the squeezing the vein between the foot and ground when walking. Additionally the cadaver research confirmed that functional venous valves are present distally in the foot.
Thus, we can see that the foot and, more specifically, the plantar venous plexus plays the integral role in driving venous return in the deep system by initiating the venous return with each extension of the foot through dorsal flexion or ambulation.
Effect of Compression on the Foot: Unfortunately, when it comes to understanding the effect of compression on the foot, we have a limited understanding based on very limited clinical data.
Clinical research is available in regards to compression of the foot demonstrating that dynamic compression (IPC, Electrical Stimulation) generates an increase in venous blood flow velocity,3, 4, 5 concluding dynamic compression results in risk reduction for developing a DVT .
Additionally, there are several studies that demonstrate that dynamic compression (IPC) can be effective for reduction of posttraumatic edema associated with ankle injury or surgery.6, 7, 8, 9, 10, 11 However, the few studies found that evaluated the effectiveness of compression bandaging showed little to no improvement in edema reduction of the leg and foot related to ankle injury.12, 13
The majority of all other studies that evaluate the effect of static compression (stockings, bandages, compression wraps) are non-specific in regards to the effect on the feet. As such, what we have developed over the years is a pragmatic yet anecdotal understanding that we must always compress the foot.
Still, many questions remain:
- Why compress the feet at all? Is it necessary from a hemodynamic perspective?
- When should we compress the feet? When edema is present only? Does acute edema or chronic edema matter?
- How much compression needs to be applied to the feet? Where in the foot is compression needed, what about the heel and Achilles tendon?
- Why should we not compress the feet?
If we think about the question, why should we not compress the feet?, we need to first determine if there is any benefit in not compressing the feet. We all would agree that the most significant impediment to successful treatment is the low patient compliance or concordance (utilization) of compression therapy. So what if we could provide a compression system that only required compression of the calf leaving the foot open?
- Would compliance be improved with an easier to apply garment and allowing for patient preferenceregarding use of shoes?
- Would the calf compression effectively counter venous hypertension or reduce lower limb edema (lower leg and foot) associated with venous disease simply by improving the venous hemodynamics during ambulation?
- Does allowing for improved mobility of the ankle joint further improve the venous hemodynamics?
- Or would not compressing the foot lead to swelling in the foot?
These are all very valid questions that need to be considered in future research.
Research Proposal: It is recommended that new research will be needed to adequately understand if a benefit may or may not be associated with calf-only compression. As such, we propose the following studies be considered along with factors for consideration:
- Comparison of Calf Only compression to Traditional Compression system for entire lower leg
- Elastic versus Inelastic compression?
- Appropriate compression level for comparison? Could/should the calf only compression be higher or equal to the equivalent full leg compression system?
- Patient CEAP classification? Perhaps we start with the C3 patient (CVI with Edema) in order to determine if compression of the calf alone will reduce edema throughout the leg.
- What about the ulcer patient? Does the actual ulcer need to be compressed? Or will improved hemodynamics of compressing the calf alone result in healing?
- What if we only compressed the ulcer and not the remainder of the leg?
Ultimately, the key parameter for any study design will be the impact on potential patient compliance/concordance. The question really is, can alternative design approaches encourage increased use of compression therapy while still remaining effective in treating the underlying disease?
These are just some of the many critical questions that need to be addressed by future clinical research studies in order to determine the role, if any, for compression of the feet.