How To Address Pronation-Related Pathology
Everyone pronates and everyone supinates. It is a matter of how much and when each occurs that determines whether lower extremity problems will occur. Shoe companies have marketed their products based on the words “pronation” and “supination.” They have done such a good job at this that people come into our offices thinking they are either pronators or supinators. As we know, high arched feet can pronate too much just as low arched feet may not pronate enough. Now more than ever before, there is more awareness of orthotic devices as a result of foot-related products becoming available over-the-counter in specialty stores or via the Internet. Indeed, people often try to help themselves before they even get to our offices. For some conditions, simple over-the-counter devices may be sufficient in alleviating symptoms. However, if people have problems that are a bit more complicated or there is asymmetry between lower extremities, custom-made devices are the best option. What makes custom devices the best option is the attention to casting as well as the fabrication. These factors separate custom devices from over-the-counter products. There are many specialties that have become familiar with making foot orthoses. Podiatry, physical therapy, chiropractors and certified pedorthists are a few that exist within this marketplace. It is hard to know the percentage of podiatry’s market share and whether it is going up or down. Our main job is to remain the experts in biomechanical knowledge as well as fabrication. With the trend of decreasing reimbursements for surgery, the possibility exists that we may see a greater interest and emphasis from practitioners on conservative care, including shoes, shoe modifications and orthotic devices. Interestingly, typing “pronation” into Google reveals several similar definitions concerning the heel and foot rolling in along with the arch flattening. None of the top 10 sites returned in this search even mentioned the word “podiatry” or were written by a podiatrist. Typing in “orthotic” into Google first leads to an orthopedic Web site. If one were trying to research the words pronation or orthotic using Google, one might think shoe stores and orthopedists were the experts in this area. However, no specialists look at the foot with as much attention to detail as we do. It is this detailed observation and assessment that will reveal pronation-related pathology. A simple example of this is a leg length discrepancy. This may present with one foot exhibiting more pronatory motion than the other. This clue not only helps determine where one should focus the examination but also affects how the clinician will prescribe the devices and how he or she will have them fabricated. First ray function also factors into pronation-related pathology. The amount of pronation within the subtalar and midtarsal joints directly impacts first ray function. Hallux limitus, bunion deformities and metatarsus primus elevatus are all conditions that affect the first ray and can be directly influenced by pronation. Unfortunately, the subtleties that occur during gait and contribute to these problems are often overlooked. Accommodations, modifications and different designs of orthotic devices are necessary to address these pathomechanical issues. Why Focusing On The Shoe Is Vital When it comes to writing prescriptions for pronation-related pathology, clinicians must start by focusing on the shoe. The shoe is the foundation. It is our interface with the ground. Our foundation directly impacts our function. In fact, the shoe serves as the ultimate orthotic device. Without a proper shoe, no matter how good the orthotic device is, function will be impacted. The shoe must have certain characteristics for it to allow the orthotic devices to function the way they were intended. The midsole. The midsole should not be too soft or too thin. In general, the midsole should exhibit a heel height of at least 1/4 inch. The necessary height can vary between individuals. Running shoe companies have tried to use the midsole as a way to control pronation. They have tried to accomplish this by offering dual density material by having a softer material laterally and the more dense material medially within the midsole. The thinking is the foot will not “roll in” as much if there is denser material medially. The problem with this approach is that the shoe compresses more easily at heel strike with a softer material laterally. The more the shoe compresses, the more likely the midsole will function as a lateral wedge. As a result, the foot lands in an even more inverted position, causing the foot to pronate more than it normally would just to get down to the ground during midstance. Some shoe manufacturers have even taken this a step further and beveled the posterior lateral aspect of the heel. Brooks running shoes are an example of this approach. It seems their thinking is that if the heel lands in a more inverted position, one can reduce the pronation that occurs during gait. Unfortunately, this is not the case for some individuals. In people who exhibit tibial varum, genu valgum or an uncompensated rearfoot varus, the foot lands more inverted and stays inverted throughout heel strike. The foot then overpronates into midstance. With too much inversion at heel strike, the person may have the sensation that the shoe is wearing laterally too much and too quickly. Then the problem becomes accentuated with a little bit of wear in the shoe. The softer density material laterally breaks down, contributing to even more inversion at heel strike and more pronation into midstance. The sole. The shape of the sole is also an important factor. Some shoes exhibit a tapering in of the region in the midfoot. Looking at the shoe from the bottom, the sole actually narrows in the middle. This happens to be the area where increased support is needed the most. Keeping the shoe as wide as possible in this region will offer more support because there will be more shoe under the foot. More shoe means more support. Additionally, if the shoe is sitting on a flat surface, the entire sole should contact the surface. Some shoes incorporate a rise in the arch region, perhaps with the idea that this will provide more arch support. However, the more contact the shoe has with the ground, the more support it will provide for the foot. The shoe upper. The upper of the shoe needs to be firm, especially in the region of the heel counter. Providing medial support as far distally as possible will help prevent overpronation as well as help the orthotic device to work more efficiently. In addition, the construction of the shoe needs to be done in such a way that both the mid- and outer sole are molded onto the upper. This is another way to provide more support by keeping as much shoe as possible underneath the foot. The opposite of this type of shoe construction is when the upper and the midsole are separate. An example of this is a shoe with a welted sole. In these cases, the foot can easily roll in or roll out, hanging over the midsole. This can be a problem after only a short time with nothing directly under the foot providing support. The insole. The insole should be removable. This will make it very easy to fit a custom orthotic device. The orthotic device needs to fit the foot as well as it fits the shoe. Provided the shoe fits properly, the more room there is inside the shoe, the more effective the orthotic device will be. That is not to say that one cannot make orthotic devices for shoes that have remaining insoles. However, the orthotics generally will not be as effective and have to be compromised because of available width and depth inside the shoe. With some materials, such as Superglass and TL2100, one may make devices for dress shoes. With serious pronation related pathology though, dress shoes and orthotic devices will not be sufficient in controlling motion as effectively. When properly fitted and functioning shoes are insufficient alone in controlling the existing pathomechanics, custom foot orthoses are necessary. The shoe, having met all of the above criteria, will be perfectly set up to accept a successful orthotic device. Keep in mind that orthotic prescriptions are the result of a thorough biomechanical examination. How To Ensure Good Results With Orthotic Casting Casting techniques include plaster, foam, wax and digital scanning. Whichever technique one employs, paying close scrutiny to the fabrication and function of the devices is important in achieving consistent results. One cannot make a good orthotic device from a bad cast. Many labs are available for the fabrication of orthotic devices. However, labs vary when it comes to the quality of the devices they make. From the podiatrist’s perspective, the definition of a successful orthotic may be different than a lab’s definition. The podiatrist wants a good outcome and a happy patient. The lab wants a happy podiatrist and no returned devices. Some labs approach the fabrication process by filling the positive cast. The more fill there is, there is less conformation of the orthotic device to the foot. Although this may keep the orthotic device from being returned for adjustments, it may not provide the necessary support to control the existing pathology. Less fill equals better conformation and more control, and less room for error in the casting process. Better quality labs have strict criteria as to how much fill they will add and where they will add it. Some labs may even provide the prescribing physician with a choice of how much fill to add. Most labs do not return the casts with the orthotic devices. Returning casts can be an expensive proposition if the labs are using plaster. The return shipping costs prohibit the automatic return of the positive casts. Obviously when casts are digitized, returning the casts is not even considered. Checking the cast work of the lab is one way to determine how well the lab is following the DPM’s casting technique and prescription. Another simple way is to hold the orthotic device up to the foot. Holding the device to the foot in the position the foot was cast will show how much fill is being used and how well the lab is performing the job of fabrication. If there is a lot of space between the orthotic device and the foot, there is room for improvement from the lab. Pertinent Pearls For Choosing Effective Orthotic Materials Material selection is also an important factor in controlling pronation. Using a material that is soft and flexible will not only provide inadequate control of the foot, the material may also break down much quicker. Pronatory forces are very strong and can break down or even break devices rapidly. Simply have a person wear a device that is soft and flexible for only a few months. Have the patient return for a follow-up visit and assess the device. One will see a change in the shape of the devices. This indicates the loss of the initially intended support. On the other hand, choosing materials that are too rigid may be intolerable to the patient and prevent him or her from wearing them at all. Pronation is necessary for shock absorption. The foot is our interface with the ground and needs to mitigate the shockwave that occurs with each step. If most or all of the pronation is eliminated, patients may find they have more pain with the orthotic devices than without. This pain can also radiate into the legs or even further proximally. That is why a semi-rigid type of material often works the best. This can be anything from polypropylene to TL2100 to even superglass. The rigidity not only depends upon the thickness but the shape of the orthotic device and the weight of the patient. A cavus foot orthosis made of a thin plastic may actually function more rigidly than a thicker material for a low arched foot because of its shape and ease of material deformation. The shape of the orthotic device is also important. The orthotic devices and the shoes need to work together. The orthotic devices not only need to fit the foot but need to fit the shoes as well. If the devices fit properly, the person will feel as though he or she has a custom shoe providing the needed support. If the orthotic devices are too narrow, the foot will spread over both the medial and lateral sides of the device, either causing discomfort from the edges or leaving the foot with an inadequate amount of support. If the devices are too wide, the upper of the shoe may be spread and the fit of the shoe compromised. This may also lead to the shoe slipping up and down on the heel, an annoying feeling that many people find intolerable. For some patients, all it takes is a minor problem with the orthotic device to give up on them. That is why attention to detail and close follow-up are critical to facilitating good outcomes. What You Should Know About Other Orthotic Modifications Other features that are important in providing control of the foot include the heel post, the length of the orthotic device and the heel cup as well as both the medial and lateral flanges. Heel posts allow motion within the foot during heel strike. We have learned that 4 inches of motion is typically necessary at heel strike. However, it is hard to believe that 1 or 2 inches will have a great impact on how the foot will function. Simply look at some of the shoes our patients are wearing with their orthotic devices. The heel may be worn laterally or the sole may be unevenly worn. A degree here and a degree there will be totally negated by a worn shoe. The main purpose of the heel post is to stabilize the foot at heel contact. With the orthotic device having a rounded heel shape, the heel post provides more stability at heel strike. Heel posts are typically made of crepe, which compresses with wear over time. After only a few months of wear, the number of degrees of motion incorporated into the heel post may no longer be present because of the natural wear. Another option is to use more dense materials or rubber. The problem with harder, denser materials is the limitation of shock absorption. One needs to obtain a comfortable middle ground and focus on the goal, which is stabilizing the foot at heel strike. Using a deep heel cup is another way to control motion within the foot, especially at heel strike. Although this sounds like a good idea, sometimes fitting an orthotic device with a deep heel cup into a shoe can be a problem. However, practitioners should avoid a shallow heel cup. Providing as much contour to the foot as possible will help control the motion within the foot. The deeper the heel cup, the better. Starting out with a deeper heel cup and then grinding down may be the best approach. This way, one has the orthotic device, the shoe and the foot to work with at the same time in providing the best fit. In addition to making a deep heel cup, one can modify the cast to provide more pronatory control. The Kirby skive is one of these modifications. Modifying the heel of the positive cast will provide more support directly under the medial aspect of the heel. One can accomplish this after fabricating the orthotic device by placing layers of thin material under the medial aspect of the heel. This is almost analogous to a medial heel wedge but one can do this in a more efficient manner on the positive cast and incorporate it into the orthotic device. Other modifications include the first ray cutout. This will allow the first ray to plantarflex and provide better propulsion from the first MPJ. If the first ray function is compromised because of hallux limitus or metatarsus primus elevatus, propulsion becomes a problem. Jamming occurs just prior to propulsion, causing the foot to pronate into propulsion and jamming the first MTP joint even further. Allowing the first ray to plantarflex provides more dorsiflexion for the hallux and can prevent pronation at this point during gait. One can enhance this with a dancer’s pad accommodation as well as a reverse Morton's extension. In Conclusion Pronation during gait is a necessity. When an excessive amount occurs during midstance or even into propulsion, problems result and symptoms occur. However, there are a variety of strategies clinicians may employ by emphasizing proper shoes, shoe modifications and orthotic devices. By using these strategies, one can control pathomechanical processes and alleviate or completely resolve symptoms. Attention to detail is the key to good outcomes when prescribing and fabricating orthotic devices. Dr. Levine is in private practice and is also the director and owner of Physician’s Footwear, an accredited pedorthic facility, in Frederick, Md. For further reading, see “A Closer Look At Case Studies In Gait Analysis” in the August 2005 issue of Podiatry Today or check out the archives at www.podiatrytoday.com.