Douglas H Richie Jr, DPM reviews the current knowledge of the cause of plantar heel pain, focusing on plantar fasciopathy as the primary pathology. Dr Richie also reviews the role of foot orthotic therapy, summarizing recent results of randomized prospective trials.
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Douglas Richie, DPM
Clinical Associate Professor, Department of Biomechanics
at the California School of Podiatric Medicine
Clinical Associate Professor of Podiatric Medicine and Surgery
Western University of Health Sciences
Past President, American Academy of Podiatric Sports Medicine
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Dr. Doug Richie: Hello, I'm Dr. Doug Richie. I’m going to present a lecture focusing on the role of foot orthoses in treating plantar heel pain. In part one we will evaluate previous published research which has given insight into the pathomechanics of plantar heel pain as well as clinical outcomes of treatment using functional foot orthoses and prefabricated foot orthoses to treat plantar heel pain.
Plantar heel pain is probably the most common musculoskeletal condition treated by podiatric physicians in this country. Recently we have had some evidence published in the literature documenting the frequency of this condition where up to 2 million Americans are affected with plantar heel pain at any one time. The lifetime risk for any individual suffering from plantar heel pain has been estimated in the vicinity of 10%.
Personally I would say these figures grossly underestimate the true frequency of plantar heel pain, because they are based upon data taken from insurance carriers and documenting actual treatment by physicians for plantar heel pain. The majority of patients who suffer plantar heel pain probably do not seek medical care.
Recently we have also learned of the economic burden of plantar fasciitis, again based upon insurance estimates rather than the overall cost affecting people who do not seek care rendered by a physician, but rather remedies purchased on the Internet or in pharmacies. But the cost at least in this study ranged anywhere from $192 million to $376 million per year.
What is more important is the impact the planner heel pain has on the quality of life of individuals who suffer from this condition. This has been long overdue. In looking at the effect of plantar heel pain and causing patients to stop exercising, perhaps not going to work every day, and basically slowing down their normal activities to a point that they're less productive and less happy. And this was a very important study published in the Journal of American podiatric medical Association which validated something that podiatric physicians have long noted in their own practice.
When we look at the causative factors of plantar heel pain, it's quite interesting because many different factors have been speculated to contribute to plantar heel pain, but when actual studies have been scrutinized we find that things like age and gender and time spent on your feet are not necessarily predictable causative factors. But one factor that always surfaces as a leading indicator or leading risk factor for heel pain is increased body mass index. We will discuss this further.
Before proceeding, it is always interesting and always important for people in practice to know the proper coding for patients being treated for plantar fasciitis, and so we’re happy to provide this insight that the proper ICD 10 code for plantar fasciitis, the diagnosis code, is quite simple – M72.2.
There is no need to designate the encounter whether it's initial or follow-up or right versus left. When patients present in a clinical setting complaining of pain in this part of their foot, it is actually speculative as to what is actually causing the pain and what anatomic structures are involved.
This slide demonstrate some of the confusion about the diagnosis and description of patients presenting with plantar heel pain. For example, in this drawing taken from the textbook, a patient who presents with pain at location number two would be thought to have an entrapment of the first branch of the lateral plantar nerve. And patients diagnosed with plantar fasciitis would actually present with pain in the brown ovoid section of the foot marked by number 1 which would certainly be in a different location than many practitioners would attribute to plantar fasciitis.
This is why practitioners will debate which structures can actually be involved in the causation of plantar heel pain. It may include any of the structure shown in the slide including bursitis, neuritis, and actual plantar fascia. This also explains partially why there is such conflicting evidence explaining the mechanical etiology of plantar heel pain and the relationship to conflicting foot types varying from pes planus to pes cavus, and the role of pronation causing plantar heel pain, and the misconception whether shock absorption even comes into play as a causative factor.
This is why this quote from back in an Orthopedic Journal in 1972 is still true today. When Snook and Chrisman were talking about insight into plantar heel pain, they said it is reasonably certain that a condition which has so many different theories of etiology and treatment does not have valid proof of any one cause. This is why today a patient anywhere in the United States presenting to a podiatric physician or to any other specialist for that matter, who complains of plantar heel pain will probably emerge from the initial treatment session with a different explanation and a different treatment varying from practice to practice, simply because there is not universal agreement on what works best and predictably to treat plantar heel pain.
This also explains partly why the Cochrane database review looking at plantar heel pain back in the year 2000 failed to come up with any evidence that there is a single treatment that predictably works for treating plantar heel pain. And even when it comes to the topic of this lecture focusing on foot orthoses, this Cochrane database review at least at that time 15 years ago, said that there is limited evidence for custom foot orthoses and that they should be used cautiously particularly in those patients who stand for long periods of time.
When patients complain of pain in this section of the foot which happens to be the most common location, upon palpation for eliciting the primary point of pain with plantar fasciitis, it is interesting to look at the mechanics of this part of the foot and understand that most likely indeed it is the plantar fascia that is involved in pain in this location of the foot, and we will focus on the plantar fascia as the etiology of heel pain in the majority of our patients; and this will be the thrust of this lecture.
The question is how does plantar how does the plantar fascia become inflamed and set up this condition known as plantar fasciitis. What is so important to understand here is that we've had significant evidence in the last 10 years starting with Harvey Lamont's paper published in the Journal of American Podiatric Medical Association which cautions against using the term plantar fasciitis simply because histopathologic specimens taken of patients undergoing surgery for plantar fasciitis or heel spur syndrome do not show evidence of true inflammation, but rather they show evidence of intrasubstance degeneration which is the result of mechanical overload.
This has led to a further insight and understanding the plantar heel pain secondary to plantar fascia strain is the result of mechanical failure within the plantar fascia, and that there are changes within the plantar fascia that are predictable and documented with study and with histopathologic specimens, showing progressive intrasubstance tearing and break down; and subsequent hypertrophy of the plantar fascia as the condition progresses. And so other terms such as plantar fasciosis similar to tendinosis have been proposed to replace the term plantar fasciitis.
This paper published in the International Journal of Sports Medicine in 2006 shows again that histologic evidence does not support the concept of inflammation attributed to plantar fasciitis, and they further say that despite the fact that anecdotally we attribute this to a arch failure mechanism, we have not really come up with valid studies linking arch mechanical failure and plantar heel pain. The term plantar fasciopathy is probably most appropriate when looking at patients who present with plantar heel pain and describing the condition.
Again, this has been validated in numerous papers, and should probably be the more appropriate term. But this raises the question: what causes these histopathologic changes; is it altered loading of the plantar fascia, or increased tensile strain because of abnormal arch mechanics. And this is critical in formulating treatment plans and foot orthotic strategy.
In Australia, Warin [Phonetic] [0:11:46] and coworkers have looked at the microscopic and histopathologic appearance of heel spurs, and rather than finding evidence that heel spurs formed from traction of the plantar fascia or the planner aponeurosis; it appears that spurs really form as a result of other stresses applied to the inferior surface of the heel, particularly bending or shear stresses. They also suggested ischemia at the insertion of the planner aponeurosis on the heel may cause spurs to form.
They point out that gait studies looking at kinetics which are forces and kinematics which is motion of the skeletal parts, have failed to come up with consistent findings about why or how the plantar fascia is strained in certain individuals who suffer from heel pain. And these researchers point out the plantar fasciopathy may not be entirely due to a failure of arch mechanics leading to excessive traction, which is the common mechanism accepted by most practitioners. Instead they suggested looking at bending forces, compression forces, and shearing forces should be considered.
This is important because it may explain the conflicting results of studies of foot orthotic therapy when we treat patients with plantar heel pain. Researchers definitely need to determine what role tensile stress and uniform and nonuniform loading of the plantar fascia has in the development of heel pain; because in so doing we need to formulate better strategies to offload or mitigate these stresses.
We have often attributed certain foot types particularly medium to high arched feet in developing plantar heel pain. But it's interesting that these long accepted notions that either high arched feet or pronated feet were likely to develop heel pain, have certainly not been validated in various studies cited here in this slide.
When we look at all the risk factors and all the mechanical mechanisms that may lead to plantar fascia overload and heel pain, it's interesting to note that systematic reviews or published research at least up until 2006 did not validate the long accepted notion of increased age and decreased ankle joint dorsiflexion, decreased motion of the first MTP as causing plantar heel pain. It was inconclusive whether arch height contributed to heel pain.
Basically all of these notions of increased body weight, heel pain, and arch height are inconclusive and are not predictive if we look at broad studies published in the literature. If we had to come up with any focused risk factor as mentioned earlier, it's increased body mass index; most reviews tend to show this as the number one predisposing risk factor. But other risk factors such as limited ankle joint dorsiflexion, the presence of a spur, diminished heel pad thickness, the relationship of pes planus and pes cavus, an excess pronation, limited range of motion the first MTP, these have all not been validated in the reviews cited below in this slide.
When we only consider high quality studies, increased body mass index in the nonathletic population, and the presence of a calcaneal spur are the only risk factors which have strong evidence for association with plantar heel pain. Studies of abnormal foot motion and abnormal foot posture meaning arch height, have been inconclusive. Again this is probably why looking at interventions for treating plantar heel pain that focus only on arch support or controlling pronation, have not shown consistent predictable favorable outcomes.
But if we look at foot orthotic therapy by itself, it's interesting to see certain trends that can be of value to clinicians in terms of using either prefabricated or custom foot orthoses. And so this segment of the lecture will be of most interest to those clinicians who use foot orthotic therapy or one to use foot orthotic therapy, to treat plantar fasciitis or more appropriately plantar fasciopathy.
And we start with an important systematic review published in 2004 by Landorf and Keenan, and at that time they looked back on all of the published papers on heel pain using foot orthotic therapy, and of those they found only six actual randomized controlled trials that were worthy of further review. And all six of these studies showed significant methodologic flaws according to the authors which included failure to provide allocation concealment, a presence of very high dropout rates, the lack of blinding, and lack of comparison to control groups.
Notwithstanding, the valid criticism of the methodologies which Landorf and Keenan cited, they were able to select six papers which at that time demonstrated the current state of knowledge in the year 2004 relevant to foot orthotic therapy and plantar heel pain. Two of these studies involve flat cushioned insoles with and without magnets. It's interesting to note that both of these studies showed no improvement with magnets. One study showed significant improvement in plantar heel pain with cushioned insoles regardless of whether magnets were included or not.
Only two studies have actually demonstrated a clear superiority of custom compared to prefabricated foot orthoses treating plantar heel pain. These studies are listed at the top of the slide and include Lynch as well as Turlock [Phonetic] [0:18:46]. Other studies have shown disappointing comparisons when looking at custom versus prefabricated orthoses indicating in some cases that a simple heel pad would provide as much or better relief than a custom foot orthoses.
Landorf and Keenan finding so many different types of results from custom and prefab orthotics embarked on what they felt would be a more properly designed prospective study in treating plantar heel pain and evaluating the efficacy of custom versus prefab orthoses. In this study published in Archives of Internal Medicine, a randomized controlled trial was undertaken involving 135 participants who were randomized into three groups: a sham orthoses which was simply a soft foam insert; a prefabricated orthosis which was actually a firm foam insert that was partially heat molded to the patient; and a custom orthosis which was made on traditional podiatric negative and subsequent positive corrected casts to fabricate a true functional foot orthosis.
The patients were followed for 12 months. The prefabricated orthosis was actually a little more than a prefab because it was heat molded to the arch of the patient, and by heat molding this device would actually be considered in my opinion a semi-custom orthosis, and certainly not similar to the prefabricated orthoses many patients purchase in a pharmacy.
In this study comparing custom versus prefab, the prefab and custom orthoses both improved pain and function compared to a sham orthosis. Although these improvements were minimal there was no superiority or difference when comparing custom and prefab. And after 12 months there was really no measurable benefit and outcome with either custom or prefab compared to the sham device, in that all three groups improved over a period of 12 months. So the improvement of custom and prefab orthotics compared to a sham orthoses can be expected in the first three months of treatment but not after one year.
This is the actual abstract and statistics from the Landorf and Keenan study which is often cited by insurance companies or other practitioners when pointing out that custom orthoses really have no benefit over prefab orthoses in treating plantar heel pain.
This study by Lee et al. was a meta-analysis of six previous studies determining short, intermediate, and long-term effects of foot orthoses to treat plantar fasciitis. Again, this study included all types of foot orthoses including those with magnets. And it was shown in the magnet study, a significant overall benefit of using these devices for treating plantar heel pain, although subsequent studies on magnets versus sham devices showed no overall benefit.
In 2008 a Cochrane review of 11 randomized controlled trials studying custom orthoses treating all types of foot pain was published. In this review, five of those papers were relevant to treating plantar fasciitis. These include four trials previously cited in this lecture, and compared to other standard treatments for plantar fasciitis, foot orthoses showed no superiority.
Custom foot orthoses were not superior to prefabricated foot orthoses as both provided improvement in pain and function in treating patients with plantar fasciitis. The essence of this Cochrane review is that both custom and prefab orthotics are valuable in treating plantar heel pain. However there is no measurable benefit thus far in 2008 of using custom over prefabricated devices.
After that Cochrane review, other prospective clinical trials have been conducted trying to compare custom versus prefabricated orthoses in treating plantar heel pain, and each of these studies continue to show the same result demonstrated by Landorf and Keenan where there is no benefit measured in the studies of custom over prefabricated devices.
A landmark study funded by the American Podiatric Medical Association again attempted to compare custom versus prefabricated devices in a very well-designed randomized prospective double-blind clinical trial. In this trial, 77 patients were enrolled and followed over a period of one year. Various outcome measures were utilized.
It's important to note that the foot orthoses that were dispensed to the patients in terms of custom functional foot orthoses were provided by a very experienced faculty instructor performing all of the biomechanical evaluation and casting, and that the custom functional foot orthoses was manufactured according to route standard functional foot orthosis device commonly used in the podiatric profession. The custom foot orthosis device was compared to a prefabricated ortho heel device as well as a sham device which was a simple padded full-length insert.
Similar to previous studies, there was no significant benefit of any type of orthosis including sham devices over traditional stretching or icing in terms of reducing morning pain. Both the custom and prefabricated devices did reduce evening campaign compared to the sham device, but again no superiority of custom over prefab. In terms of foot function there is no advantage of custom over prefab.
What was interesting in this study and unique was that the researchers showed a significant improvement of spontaneous physical activity as well as duration of standing and duration of walking when they wore accustomed device compared to prefab. The researchers suggested that objective measures of activity and weight-bearing may actually be more sensitive and specific for measuring clinical outcomes of orthotic treatment.
So in summary as we look at all of these past published papers, these randomized controlled trials that show no advantage of custom over prefabricated orthoses in the treatment of plantar heel pain. Many practitioners will say this totally contradicts their own clinical experience, where patients presenting to clinical practice have already tried a prefabricated device and failed, and once they're placed into a custom foot orthosis their symptoms improve.
We can look at these studies and perhaps come up with an explanation of why the studies are refuted by the clinical experience of many practitioners. Randomized controlled trials study large groups of patients, and the statistics are an average of the results within each group; an average such as the average pain relief of a prefab versus a custom versus a sham orthosis.
The treatment intervention will either work reliably and consistently for the entire group or it won't based on the average score of the entire group. However within each group there are patients who respond to treatment and patients who do not respond. Few studies evaluate the subjects within the treatment groups who do respond and don't respond, and then try to figure out why certain people respond favorably within each group; instead the average score is reported for the entire group.
In our own clinical practice we also see that certain patients will respond favorably to custom foot orthoses while other patients do not. The key question then is how can we predict favorable outcomes with foot orthotic therapy in specific patients.