The Short Answer

Sole Supports are the only custom orthotics available today based on a completely new paradigm (MASS position) that was developed to actually change foot posture and function during weight-bearing activities. The corrected (MASS) position of the foot is captured by a unique casting technique that utilizes a certain density of foam and a sequence of semi-weight-bearing impressions that emulate healthy stance-phase gait (gait-referenced casting). The lab positives made from this cast are never "cast-corrected" to arbitrarily lower arch height as is common in the industry. The resulting shell fits the shape of the foot like a glove and is machine calibrated to have the right properties of flex and rigidity based on the patient's weight, foot flexibility and activity level. The goal is to significantly limit pronation, facilitate supination and yet flex just enough for comfort. This custom level of rigidity/flex makes us unique in the industry and uniquely effective at improving foot function.

The Long Answer

The best way to understand the different paradigm that Sole Supports has created in the custom foot orthotics industry is to review the history. The history of corrective foot appliances is surprisingly short but interesting. For most of civilized history, the only thing available was probably some sort of felt comprised of compressed animal hair -no doubt because it offered some form of a cushion in the shoe. The industrial age brought some new attention and materials. Flat feet, also called then "weak foot",were an obvious point of intervention, so we tried to elevate the arch with steel plate, solid wood or glued mounds of leather. They were uncomfortable by design and relied on muscles to try to elevate the arch away from the device out of pain. Due to the horrendous discomfort from such unyielding materials, it seems the entire concept of direct and full arch support became largely rejected or avoided. The functionally useless but comfortable cushion remained popular.

In 1941, Manter described the axes of the subtalar, midtarsal joints and the 1st and 5th rays. Hicks further describes them in 1953.

1948: Schrieber and Weinerman propose that alignment of forefoot to rearfoot is important, and that inverted and everted forefoot positions are abnormal and require ‘balancing’. Later incorporated by Root et al.
1950: Ben Levy’s ‘rubber butter’ to balance forefoot (the basis became the functional foot orthosis).
1949: Hiss’ Functional Foot Disorders describes a rational foot classification system Arch height/flexibility. Elftman presented the concept of midtarsal joint locking, influenced by the subtalar joint, in 1960. In 1956, Wright et al describe the motion of the rearfoot during gait. No one had yet tried to put these academic explorations into a coherent clinical program for foot management.

In the fifties, experimentation with devices to control the extreme over-pronation in pediatric cases lead to the development of the UCB orthosis. While effective for this population, the severe control imposed by this and other subsequent devices (Schaeffer Plate) did not make them practical for widespread use in the management of common adult foot conditions. There was also little focus on biomechanical analysis of normal and abnormal foot function, so the origins of many common foot conditions were not well understood. The rationale for developing corrective custom orthoses for the masses was missing.

In the 1970s, a group of pioneering podiatrists in the academic community of the California College, started the first comprehensive study of foot biomechanics and their clinical implications for treatment. The group included Merton Root, Bill Orien, Tom Sgarlatto and John Weed. A series of volumes, including the famous Normal and Abnormal Biomechanics of the Foot, were published and became the model for the new, modern science of foot correction. Interest in and prescription of functional custom foot orthotics began to spread rapidly into not just podiatry, but all fields engaged in orthopedic management of the foot and lower kinetic chain. Root, Orien and Weed became the textbooks for new graduating classes of professionals.

That much is understood by most practitioners trained in this mainstream model of biomechanical evaluation and orthotic intervention. What does not seem to be well understood or remembered is the historical and teleological context in which Root developed his ideas. For an excellent review of this see the article by William Lee in Clinics In Podiatric Medicine and Surgery (October 2001). In brief, Root was determined to be the Linnaeus of functional podiatric anatomy (Linnaeus was the famous swedish taxonomist who gave the science of biology its first universal classification system). He was frustrated by the lack of common terminolgy when discussing foot structure and function and felt that Podiatry could not be considered a serious science without it. He was devoted primarily to developing a uniform terminology that could then be used to define "normal" foot structure and classify the many varieties of deviation from the norm. So the focus was classification rather than achieving optimal functional correction of the foot on the ground.

In order to accomplish his goal, Root needed a universal reference point from which all possible structural deviations of the foot could be defined. One day he had an inspiration while taking a shower: a concept of a "neutral position" defined by certain frontal plane relationships of the foot viewed posteriorly in the open chain. This concept was probably influenced somewhat by the work of Wright et al in the 60's with their description of "relaxed calcaneal stance position" based on the measurements from two subjects. The main point here is that any defined reference position for the foot is naturally arbitrary, so Root's formulation is as good as any. It is useful for classification purposes only, though, and lacks any important relevance to stance phase functional goals for healthy foot behavior. Indeed, Root put his "neutral position" paradigm ahead of any functional considerations and did not feel research was necessary to prove the clinical results of neutral position methodology. In many ways, the clinical intervention strategy he proposed was more of an afterthought -an extension of an arbitrarily preferred ideal.

The model or goal of correction proposed by Root centered around the concept of "neutral position": the proper frontal plane relationship of the rear to the forefoot (1/3 range of total inversion from the positon of full eversion) with "maximal pronation of the oblique midtarsal joint", the foot somewhere between extremes of supination and pronation. Root believed that normal, healthy feet operated primarily about this central posture of the foot, avoiding extremes of both supination and pronation. Clinically, this position is assessed in the open chain in a number of different ways, but primarily by talonavicular joint palpation. Then, since Root's classification system invented the categories of rear and forefoot varus and valgus, he felt it was important to correct them. They were to be corrected by means of posts ( a kind of wedge) under the heel or forefoot, thereby bringing the ground up to the foot and filling in the anomalies of structure.

However, there are some very interesting observations one can make about both the model and how it achieved this sort of preeminence. Consider, for example, that the most common biomechanical fault in the population is over-pronation (aka "weak foot", pes planus, or flexible, flat foot). This condition is characterized by various degrees of arch flattening, medial splay of the midfoot and failure to adequately re-supinate at the end of stance phase -none of which is directly addressed by the Rootian model. Indeed, with the advocation of neutral postion as the ideal posture of the foot, the Rootian model allows about 50% of sustained pronation throughout stance phase and is unconcerned about assisting re-supination, relying primarily on intrinsic supination mechanisms such as the windlass effect of the plantar fascia. If these intrinsic mechanisms were capable of doing this, why is the failure to re-supinate so common?

It is also not at all clear how posting under the heel and/or forefoot can correct midfoot posture, i. e. achieve adequate tarsal supination from a position of over-pronation. A simple mechanical analysis, from an engineering perspective, shows little potential for enough torque or leverage to be exerted to accomplish this, especially through the preponderant soft tissues under the calcaneus. And what good, one might ask, is rectification of rear to forefoot relationships, assessed in the open chain, if midfoot collapse and functional over-pronation still compromise normal foot function in gait? No matter what sort of inclined surface one puts under the heel or forefoot, a structurally loose midfoot is going to collapse.

Assessed against the practical goals of biomechanics (listed below), the Rootian model appears remarkably irrelevant:

1. Sufficient supination at heel strike to buffer against rapid and overly deep pronation

2. Sufficient re-supination of the foot occurs after midstance to stabilize or “lock” the tarsus in the sagittal plane to allow for efficient propulsion.

3. The forefoot contacts the ground without imposed abnormal compensatory motion proximally or in the transverse, sagittal or frontal planes

4. The first metatarsal is stably plantarflexed against the ground during forefoot loading

5. The first metatarsal accepts 60% (or, at least, the majority) of forefoot loading force

6. The first metatarsophalangeal (MTP) joint is free to dorsiflex sufficiently to avoid compensations in foot or lower extremity posture that would otherwise be necessary to allow sufficient dorsiflexion or forward gait progression

If your orthotic control is based largely on rearfoot posting, as the majority today still are, you might wonder what is helping the foot to re-supinate after heel lift?

It is also quite startling to realize that the mass migration to the Rootian model of orthotic intervention happened without any research showing that it worked. Apparently, so little in the way of biomechanical analysis existed previously that everyone was eager to move forward with the first credible attempt. And once what was new becomes the standard of care, the ideas triumph by being taken for granted. It serves as a great reminder that all true sciences evolve, so the value of prevalent theories should always be investigated.

In fact, the vast majority of research that has compared the relative effectiveness of Rootian custom orthotics to prefabricated ones, or even to other treatments, has shown no significant difference in outcomes. (See our Theory & Research page for references)

Sole Supports were developed with a completely different model of correction, casting technique and orthotic design. Dr. Edward Glaser was a practicing podiatrist in Middle Tennessee who had never felt comfortable with the biomechanics and orthotic construction training he had received in school. So he experimented with his own theory and designs in the early 1990s. It helped that he was trained in mechanical engineering prior to studying podiatry. The following is a brief summary of what his investigations have evolved into today (for a more detailed account, see the articles in our Theory & Research page).

First the model of correction. Before you can make an effective orthotic, the end result of the orthotic use must be defined. Since lack of supination is the issue in a majority of feet (see goals outlined above), we defined the MASS position as the correction goal. MASS is an acronym that stands for Maximal Arch Subtalar Stabilization. The foot is put into as much supination as can be comfortably attained by an individual foot with the heel and forefoot flush or plantar-grade to the floor. The extent of supination is defined by the relative flexibility of the individual foot which is a reflection of the ligamentous laxity of that foot.

The casting technique used to capture this position has the patient seated for a semi-weightbearing procedure utilizing a foam cast medium. The floor is critical as a frame of reference to insure reliable and repeatable casting results. The patient cannot simply step into and out of the box, as with some lab protocols, since then we would capture the collapsed elements of the foot posture -the very things we want to avoid. The patient's foot is then systematically introduced into the foam in the same pattern of loading as in normal stance phase. This again respects the functional process we wish to control, avoiding arbitrary postioning of the foot for impression, guessing at the best posture of the foot. The foam supplies positive pressure upwards against the foot during the impressions, preserving the optimal arch structure of that foot created by the impression sequence. There are no forefoot varus or valgus deviations left in the cast at the end of the sequence because each part of the foot impressed is taken down to floor level. The casting technque is much easier, faster and more reliable than plaster.

Even so, we insist on good casts prior to processing an orthotic order. We may be the only lab that actually rejects some casts. Because with us, it truly makes a difference. We go to alot of time and expense to train or certify our clients in this technique since so much depends on it.

Once we have a good cast, we ask for more information than is usual. Because in order to make a true custom orthotic we need more custom information. We need to know how much your patient weighs, how flexible the feet, what activity levels are common. Everyone usuallly asks: should an orthotic be rigid or flexible? Wrong question. The right question is: how much downward force form the person does my orthosis to need to counteract: absorb, deform slightly, and then spring back to deliver adequate foot re-supination after heel lift? To answer that we need to know weight, flexibility and activity level. Then we put that into an equation that delivers a target calibration goal when we test the finished orthotic shell. That is the new definition of custom.

We never "cast correct" -a euphamism for arbitrarily flattening the orthotic arch. We realize that an orthotic needs to contact the entire foot surface to impose a corrective force on it. Especially in the crucial arch/midfoot area that wants to move ever closer to the ground. How can we do that and not suffer the fate of the nineteenth century experiments with full arch contact? How can we exert that much control over foot posture comfortably? First we use the right material: the right polyethylene plastic with good shape memory and the right combination of flex and rigidity.

Next we realize that the critical comfort factor is force per unit area of the foot as opposed to total force. The reason the yogi can tolerate lying on a bed of nails is the high density of nails per unit area. He would not survive llying on just a few nails, but with force spread over hundreds of nails, each nail is tolerable. So if we have our orthotic flush against the entire foot, individual areas of pressure are so evenly distributed that it is easily tolerated. Now to do this you must insure you are working off a good cast -one that captures all the relevant morphology of the plantar foot.

Finally, we calibrate the flex/rigidity of the supportive shell based on custom patient information. The result is a true custom device that actually achieves the goals of normal gait biomechanics.

What about high-arched, supinatus or rigid feet? By definition, one cannot change much of the function of a rigid foot, but you can re-distribute plantar pressures with a full contact design. One of the most common complaints of the over-supinated foot is pressure concentration at the heel and/or fifth met head, occasionally the first met head. A healthy layer of cushion foam and full contact goes a long way in helping this kind of foot.

Can Sole Supports help every kind of foot? We can help most feet, but the ones we are probably not going to do much for are certain kinds of traumatically deranged feet, especially where rigidity is a major factor. Also, certain conditions such as Charcot foot or extremely rigid flat feet may not respond well to the kind of control our orthotics impose on the foot. They may benefit, though, from pressure re-distribution which we have found effective for the high-arch, rigid foot as esplained above. For individual cases, consult our Tech Support team.