Rise fall and rise of the custom orthosis

By Andrew Horwood MSK Podiatrist M.Pod.A, D.Pod.M.

The Rise of the Custom Orthosis

The history of foot orthoses is an interesting and an unexpectedly long one, going back to the late 19th century. However, these early devices were felt to be merely arch supports by the likes of Otto Schuster. Please note that Schuster believed that foot supports were a precursor to exercises (Schuster, 1939, pp183‐190). He felt only two corrective devices were available, the Whitman Brace, plus its modifications, and the Roberts brace (Schuster, 1939 p.174‐182). Both were developed in the early 20th century and utilized plaster of Paris (p‐o‐p) molds of the foot and both were made of steel.

The Whitman brace was still advocated as a corrective device by Charlesworth, and it appears in the 2nd edition of his book published after his death (Gibbard, 1968 p.162‐164). By now there were multiple insole designs and manufacture techniques, and Charlesworth’s Chiropodial Orthopaedics, dedicates 5 chapters to them. There are even separate chapters on “surgical inlays” for the American technique and the British technique. Certainly there was no consistent approach, and the term foot orthosis was largely absent until the arrival of the Root technique.

The Whitman Brace. There were many modifications to this design and in its later form was often combined with the Robert Brace design to form the Whitman Robert Brace.

 

 

Until Root developed the Root functional foot orthoses, podiatrists had used a variety of devices designed by podiatrists and orthopaedists generally around static arch height (Lee, 2001). In fact a common system was to classify feet into first, second and third‐degree flat feet, although as early as 1919 this classification had detractors (Lee, 2001). Length of metatarsals also effected prescription criteria. In the light of its recent validity questions in relation to gait, it is interesting to note that Helbing’s sign was also considered abnormal, and taken as a measure of pedal pronation (Lee, 2001).

Because Root’s theory of foot classification was based on subtalar neutral, it is hardly surprising that his prescription technique evolved around a device balancing orthoses around this subtalar neutral position. However it is important to note that Root stated his device was based on the premise that a foot moves abnormally only when subjected to abnormal forces, those of compression and tension (Lee, 2001). He therefore wanted to design an orthoses to redirect these forces into the foot. He therefore based the design the already popular Levy mold, a technique developed from taking a plaster of Paris cast of the foot (Lee, 2001). The Levy mold was made from a semi‐weight bearing cast resulting in a full length insole balanced within the forefoot with even the toe crests being molded into the device, apparently to aid toe flexion.

Root chose to use a non‐weight bearing technique, as that is what he had been taught at the California College of Chiropody. To capture any forefoot malalignments Root postulated that the midtarsal joint must be fully pronated around its axis, while by casting non‐weight bearing meant the shape of the heel would not be lost by the flattening that occurs on a weight bearing cast. The main difference in the Root device over the Levy mold was the anterior edge of the resultant orthosis terminated just proximal to the metatarsal parabola (Lee, 2001).

Roots early devices, like Levy molds were made of latex and the sanding from oakwood floors, which the cast was pressed into heel vertical. Any forefoot misalignment was then captured. Root noted success and failure, prompting him to add a medial heel wedge, without much further success. He then tried a triplanar wedge medially, and a lateral wedge to counter‐balance the lateral slide of the heel that often resulted. He felt his modifications were blocking subtalar joint pronation (Lee, 2001).

Root tried a number of other materials before coming on to Rohadur, and using dental acrylic to make his triplanar heel wedges. He experienced patients developing back pain and felt this was a result of immobilizing the subtalar joint, so came up with the method of tilting the shell while the acrylic was during, which he felt would allow the necessary subtalar motion. This was later changed to a biplanar grind. Root now referred to the heel addition as the rearfoot post. Other cast adjustments were made to accommodate the rigid material to the foot comfortably, such as the medial addition, and the balance platform (Lee, 2001). The arrival of the Root orthosis during the late 1960’s corresponded with a rapid rise in amateur sports, especially running. This was producing a new clientele for podiatrists, while the Root model gave a nice theoretical solution. Text books followed in measuring and establishing the neutral position in 1971, casting techniques and finally in1977 Normal and Abnormal function of the Foot: volume II. The plan was for this book to be out dated in five years and replaced by a further volume, but due to Root’s health issues, a problem since 1958, it was a project never completed. However, the Root functional foot orthosis was to gather pace.

With effectively no rival model, the neutral cast foot orthosis was gradually introduced to the Schools of podiatry in the USA, and by the mid 1980’s was even arriving in the UK chiropody Schools. A generation of podiatrists was brought up on the technique and this generation firmly established foot orthoses as a ‘fundamental’ part of the podiatry scene. It could be argued that in the UK foot orthoses and foot surgery turned chiropody into podiatry.

Other types of prescriptions, such as the Blake Inverted (Blake & Ferguson, 1993) or Lundeen’s triaxial posting (Lundeen,1988) have been added to the neutral framework, by modifying the neutral cast, and other foot function models have come with their own prescription additions to the Root model, but the concept that the foot develops pathology from intrinsic osseous dysfunction has never gone away. What I will call bottom up models, with only McPoil & Hunt’s model trying to come away from these ideas (McPoil & Hunt 1995).

Drawing of the cast modifications from a medial view, of the traditional Root medial addition top, and the Blake inverted technique, bottom.

There have been multiple additions to the positive cast over the years, from medial heel skive to my own distal shell extension, and most recently the medial oblique shell inclination. Despite being reported as new, such additions can be found in the literature going back to the 1960’s and beyond. Although new socalled “theories” have changed to under pin the prescription, and new materials have arrived, the principles of the end product hasn’t really changed in 100 years. Today’s “theory” of the moment is the “orthotic prescription protocol for the unified theory”. It is a little sad that for 200 years people have never understood the difference between paradigm and theory when used in the scientific concelpt. I’m sure it would help!

The Fall of the Custom Orthoses

The custom foot orthosis reigned supreme until the late 1990’s. However, things started to change when inconvenient research results started to ask awkward questions, and from the early 1990’s the perform foot orthosis market started to grow.

No one can deny that custom foot orthoses are time consuming to prescribe, time consuming to make, and expensive to supply. Neither can anyone deny that they can work really well. But when they don’t work, they are an expensive failure that either the patient or the taxpayer isn’t going to love you for.

Of course for a long time the way orthoses were prescribed by podiatrists was based on a recipe developed by Merton Root and those who inspired him. We would measure relaxed calcaneal and neutral calcaneal positions in stance, and the subtalar range of motion, inversion, eversion and ankle dorsiflexion nonweight bearing. Then finally we’d measure the forefoot to rearfoot alignment.

Then we’d cast the foot in neutral, although how repeatable that position was is debatable (Chuter, et al, 2003). Being a true believer I’d then check the cast corresponded with the clinical measurements, and write out a detailed prescription along the lines advised by Ray Anthony (1991, pp109‐151). I was to find out later that at one of the most prescription conscious orthotic laboratories during this time, had only three practitioners who wrote full prescriptions for the lab to follow, and one of those was Steve Bloor! Everyone else just ticked the “at the labs discretion” box. More worryingly most podiatrists didn’t even bother to tell the laboratory what the diagnosis was! Effectively, devices were being made to a cast, without a prescription, by people who had never seen the patient, and therefore didn’t know what was required. They didn’t even know what the orthoses were for!

During the 80’s and 90’s the dominant foot shape capture technique was the plaster of Paris (p‐o‐p) bandage, which is still my preferred technique. Foam boxes and laser scanners are also now used, but no evidence supports one technique over the other to result in better orthoses (Trotter & Pierrynowski, 2008a) . Laser scanners and foam boxes are certainly less messy! Despite this I suspect p‐o‐p is still the main technique used by custom laboratories.

But there is something very interesting about taking a cast or scan of a patient’s foot. By the time the laboratory is going to press the mold, or the machine to grind out the block for molding, there is very little of the patient’s original foot contour to mold the shell to. Arch fills, medial additions, met domes, lateral additions, balance platforms and dells completely change the foot contour, the very contour that we told the patient was essential to make their orthosis on! Also Root, having made such a fuss about casting a foot in neutral, then added a medial skive to the rearfoot post, effectively allowing the foot to pronate over the shell. This effect is compounded by the medial addition and arch fill.

Drawings of the cast modifications made on a neutral cast before shell molding for a Root functional foot orthosis. Taken from Anthony, R.J., (1991) The Manufacture and Use of the Functional Foot Orthosis. Base,Switzerland, Karger.

CAD‐CAM technology and the emergence of numerous new laboratories have certainly improved the turn around time in more recent times, but back in the early 1990’s most laboratories offered a 4‐6 weeks turn around time. This tended to leave the patient in pain for much longer than acceptable. For myself, the solution was to make up a temporary device on a Frelen insole while we sent the cast to the Lab. Two things became apparent to Steve and Myself. That these simple insoles fitted in the clinic often fully resolved the symptoms just as well as the custom devices. Even more interestingly, often the temporary devices worked better than the custom devices! This was a “Eureka” moment for both of us. As a result our immediate solution was to start ordering our custom devices partially completed, so we could make final adjustments in the clinic. What we discovered is that subtle prescription change was more important than method of manufacture. Material choice affected the durability of the orthoses, but prescription choice of material and direction of force vectors created by the orthoses affected the outcome. Manufacture technique only affected the materials you could use!

Despite this, custom foot orthoses have ridden a wave of majestic mystic. “They are not arch supports! They are orthotics!” So the story to the general public became with these special orthotics you will have a device that makes your foot, work “correctly”, and your pains will all go away and you’ll never be injured again. For such a fantastic piece of technology you will have to pay out some serious money. I have come across prices over £600 for the provision of “orthotics”, although it has sometimes been unclear if that also included the casting and the examination called biomechanical examination, which may or may not include biomechanics.

With such costs, and the unhappy patients that frequent failures caused, two opposite events happened. The first was some practitioners decided that such devices were a con. The leaders of this movement were certain orthopaedic surgeons, who often referred the patient on to an orthotist for insoles, because insoles rather than “orthotics” were ok. The other group was some physiotherapists, who (probably quite rightly) were concerned that no other aspect other than foot morphology was being taken into account. At the opposite end were many professionals in private practice that saw “orthotics” as a sack of extra cash, which just the podiatrists were picking up.

The problem for this new group was that Rootian provision for orthoses looked, and was complex. Courses did develop for osteopaths and chiropractors among others, but casting never really took off. However around this time perform orthoses certainly did, with AOL (now Vasyli) leading the way. Physiotherapists, osteopaths and chiropractors could now prescribe “orthotics”, although supply would be a better description. The advent of single step pressure platforms linked to a range of preformed orthosis shells have been particularly successful at offering professions a “no need to know” solution, so convincing that that even podiatrists are now using them. Sadly these devices are referred to as custom and sold as such. Only one source has published how the pressure data is used to choose the shell profile (Dixon & McNally, 2008) and that clearly indicates that such devices are not custom.

Total abuse of the custom foot orthosis has occurred at some clinics, Some of these clinics have been run by recognized professions, others have not. One term used by some is Biomechanical Consultant, which although sounding grand is not a regulated or recognized profession. With little if any educational standards required prescribing or selling foot orthoses, the orthosis remains vulnerable to abuse from the well meaning but ignorant to the greedy and self‐deluding. The functional foot orthosis, custom made to the patient’s needs promised so much, yet became abused by over selling and practitioner ignorance and greed. It is hardly surprising then that the patients have taken the middleman out of the equation, and looked to purchase the orthoses directly from shops. Preform devices are now everywhere from the supermarket to the running shop. It has to be said if orthoses are given to patients unadjusted by practitioners, well why not just go to a shop and buy a pair! And lets face it, for many people what they buy will do the job nicely, particularly if they are using a device to over come a minor injury.

For too many practitioners orthoses have become an income generation scheme, with patients not being offered all alternatives, including cheaper alternatives, to custom. Some practitioners are trying to treat with a machine like approach that all lower limb symptoms can be resolved with a cast custom device, with little regard to diagnosis, mechanism of injury or treatment plan including rehabilitation. In the last edition of the sadly dead and little read, International Journal of Podiatric Biomechanics, I wrote the following: “Do podiatrists really want to be expensive insole suppliers, rather than clinicians picking what option is best for their patients? Podiatry has risen with the foot orthosis. It could just as quickly fall with the foot orthosis if it refuses to take the high ground in the matter of prescription. Remember: diagnosis, mechanism of injury, treatment plan and review: not, hello, I’m a podiatrist. Meet my expensive friend ‘orthotic’!”

Foot Orthoses research; deciding on treatment

Exactly how foot orthoses work still remains an unanswered question. It has been suggested that kinematics, kinetics, neural control pathways and gait economy could be altered by orthoses. Fundamentally the research can be split into two types. The first type seeks to see improvement with foot orthoses either in gait parameters or symptoms. The second type tries to prove one type of foot orthosis is superior to another (Dixon & McNally, 2008, Trotter & Pierrynowski, 2008b, 2008c). Surprisingly there appears little effort to try and test different materials or investigate prescription additions. Most concentrate on one type of casting technique over another, custom over perform and pressure plate prescription over traditional podiatry techniques (Dixon & McNally, 2008). The recent papers by Trotter and Pierrynowski (2008b, 2008c) shows the problems we are faced with present research. First they looked at pain relief (Trotter & Pierrynowski, 2008b), then, using the same forty‐two patients, they looked at kinematic vertical excursion of the body’s centre of mass, taking minimum excursion as an improvement in gait (Trotter & Pierrynowski, 2008b)(the study does not acknowledge that some vertical excursion is normal and desirable). The custom insoles were made from foam impression casts to a technique promoted by the custom laboratory supplying the custom orthoses, the maximal arch subtalar stability position. The material for these was polyethylene. The performs were not adjusted, and made from low density, open cell, 4mm foam inserts. The initial effect was both sets of orthoses tended to reduce the vertical excursion of the centre of mass. But the performs stopped being as effective sooner. It seems not to have entered the researchers minds that 4mm of low density, open‐cell would tend to flatten down quicker than polyethylene! They conclude that the custom devices are better than the performs. Trotter actually owns the laboratory that made the custom foot orthoses. I’m sure that didn’t influence his study designs!

Without turning this into a review of FFO research, I will sum up the work out their by saying that treating all musculoskeletal pain with one prescription material, technique or approach makes little sense. Yet despite this the researchers continue to approach the problem in a similar way. This probably holds progress with foot orthoses back. A more reflective approach, which is well worth a read, is the recent one by Davis et al (2008). They cite pain relief success rates between 70‐80%, with 53‐83% of such patients continuing to wear orthoses after symptom resolution. Custom orthoses were considered to be not worth the expense by 11%. The study then looks at kinematics between custom and semi‐custom foot orthoses and found subtle variations between the types. Interestingly the biggest effect was in eversion excursion, with the semi‐custom producing more change in walking, and the custom more change in running! There is so much more work to be done.

The true nature of customisation, what patients need

So should we just take orthoses out of a packet, stick them in the shoes and send the patient away? If that be the case then why not get the patients just to buy devices at the running shop or on‐line? There can be little doubt patients get better doing just that. Orthoses are great passive cures for symptoms. But, if we end up doing that I believe that we are selling orthoses short of their true potential. Orthoses are a fantastic rehab device, yet they seem to be rarely used that way.

Let's get back to Steve and I building up our frelens and modifying custom devices. What we learnt was we could hold off on prescribing foot orthoses and play around with the frelens until we got the results we wanted. Then rather than trying to make the custom orthoses the shape of the patient’s foot, we tried to make the custom devise work like our temporaries. We also found that sometimes with exercises and the temporary devices the problem resolved and the foot posture improved. They didn’t need to move to a custom device. We haven’t been alone in discovering this. In fact I was told by one custom laboratory owning podiatrist, that he was doing what Steve and myself was doing, and rarely prescribed a custom device! A podiatry practice I know of relies on sales of custom devices and has therefore stopped issuing temporary devices. He was getting better results with adjusted preforms. Patients then complained that their custom didn’t work as well. Better financially to have patients feeling a bit better and parting with £400, than those who previously got 80% better with a £30 orthosis, then worsened with the £400 device! There is also a podiatrist who tells patients that the temporary device belongs to him. If they don’t go ahead with the custom, they must hand them back, and makes them sign an agreement to that effect!

What was obviously needed was customizable perform foot orthoses. I won’t bore you or ram home our products down your throat, but Steve and I have worked with Healthystep since 1997 to develop what we feel is needed, though the first product didn’t reach you until 2002. We continue to expand and improve our range. Other companies are also trying to do the same. You can get as good results as with custom with a customized perform, or a semicustom orthosis from a lab, as long as you use similar prescriptions and materials. Interestingly, a new technique of custom device manufacture has developed from the customizable perform. When a perform device works really well, but needs greater durability, the device rather than a cast of the foot, is sent to the lab, or a foam box is used to capture the device profile. The custom laboratory uses this with prescription details to make up a custom device. The only occasional problem is this: the patient sometimes still prefers the customized over the custom, probably because of the change in materials.

Functional Rehabilitation foot orthoses - the future is here

During this conference I hope the following concept has become clear. Foot orthoses are not living to their full potential if they are used in isolation. They are one element in a treatment plan. Yes they are popular with patients, because unlike exercises they don’t need to be worked every day. Patient’s primary complaint is lack of shoe space with orthoses, and restriction of footwear styles. But FFO treatment is not only passive for the patient; it also is a passive treatment for the structures that they off load. That will allow structures injured by over stress to heal, but to achieve reduction in stress, the FFO is often used to make life easier for a muscle, and that won’t strengthen it.

Yes, if a muscle or tendon is permanently damaged then such support is going to be permanently necessary. The injured structure in this situation is unable to deal with the normal stress a healthy structure could. Such cases as Tibialis tendinosis especially grade 2, or chronic Achilles tendinopathies are good examples. Those patients damaged by heamophilia or arthritis is going to need permanent intervention. You are more likely to need orthoses on a permanent basis the older your patient is. But should you really be prescribing a custom carbon fibre device to a 22‐year‐old man who has just taken up running and is complaining of anterior shin pain? Do they really need a device with a lifetime guarantee?

Over time with appropriate manipulation, mobilization, exercises and postural retraining, patients foot posture and body posture will change. As a consequence so will gait. FFO may need to be withdrawn, or control reduced over time. Also humans have accidents, or don’t keep up with exercises, and in time the nature of our body tissues change, and with it our foot posture and gait. FFO’s may come and go and come again into our patients’ lives. A fixed single prescription for a lifetime is quite frankly a ridiculous concept. Like taking a paracetamol for a head ache and being told you’ll need to take it for the rest of your life to stop a headache happening again!

FFO’s must be used as an integral part of a treatment plan. They can be used to stabilize a joint while its supporting tendon recovers from an injury, thereby prevent further pain and damage to these structures. Perhaps as a consequence of the instability a joint keeps over compressing in one position and effectively locking in that position, like a dorsiflexed locked 1st metatarsal cuneiform joint. Capture the foot in the deformed position in a cast will give you a FFO that maintains the deformity. Manipulate first and free the joint, strengthen the plantarflexors, and use the orthosis to stop the foot drifting medially, and in a few months you have reversed the situation. Get the patient in the right shoes to avoid the problem in the future and wean the patient of the orthosis. This is what podiatry treatment should be about. Active planned management, not cutting toe nails every six weeks because they grow.

For this sort of approach you need an orthosis that is cheap enough to throw away at the end of treatment. We need customizable FFO therapy, of many different types, different materials and uses. We need custom FFO’s that are more custom than what we refer to as custom FFO’s. The irony is not lost on me!

References

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