Why Podiatric Surgery? – Part Two

The importance of biomechanics and pathomechanics in understanding disorders of the foot.

Podiatrists and podiatric surgeons receive considerable academic and clinical training in understanding the normal and abnormal function of the foot. The foot is a complex structure and is anatomically unique for a number of reasons. As such, it requires a lot of detailed study to understand it properly. If you require a podiatrist in Canberra, please contact us here at ACT Podiatry for your consultation today.

The ‘normal’ foot

How we classify normal? A foot which is pain free and functionally stable without significant deformity could be classified as normal. However, there is no easy criteria for defining the normal foot, because there are a number of parameters to consider. From a functional perspective, Dr Kevin Kirby DPM has stated… ‘a normal foot at relaxed stance is one which pronates (rolls in) halfway between the neutral position of the foot and the point of maximal pronation’. This makes a lot of sense. Feet should roll in a little during relaxed stance, but not too much. There should also be approximately equal amounts of pronation movement (rolling in) and supination (rolling out) during the stance phase of gait. This is the time each foot is bearing weight whilst walking (Kirby, K.A. Biomechanics of the normal and abnormal foot, J Am Podiatric Med Assoc 90(1): 30-34, 2000). 

A foot which is without pathology can also be considered to be normal. However, a foot may be pain free in the presence of these conditions, because it depends upon the degree or extent of the disease and what a person does on his/her feet. There may be other factors to consider. For example, a type 2 diabetic with peripheral neuropathy resulting in neuropathic feet (ie- loss of feeling) may not feel pain associated with an infection. But an infection is not normal, whether there is pain or not. Such a scenario is very dangerous to the patient, so pain alone cannot be relied upon to separate an abnormal foot from a normal foot. Usually a minor deviation in foot structure and/or function is not associated with pain. Such feet may be considered as lying within a normal range. However, a foot with significant structural deformity can’t be considered to be normal,  nor can one which pronates or supinates excessively (ie- exhibits abnormal function). In such cases, a patient may not be symptomatic; it may be that they have restricted their walking or activity levels to adapt to their deformity or abnormal function. This of course is not good; such an adaptation should be considered abnormal.

Therefore, there is no easy answer to what constitutes a normal foot. The nuances of this usually become apparent when a person consults with a health professional, with knowledge of the foot and lower extremity. Podiatrists and podiatric surgeons are well placed to discuss what is normal in regards to foot function and structure, in the context of each patient, as they spend a significant amount of time studying foot function, structure and the disease/conditions, which affect the feet. As Dr Kirby states…’Therefore, those health practitioners with the greatest knowledge of the intricate biomechanics of the foot and lower extremity will be the most successful in treating the multitude of mechanically related foot and lower-extremity pathologies that can occur.’

The ‘abnormal’ foot

In this section I will focus on disorders and conditions which are clearly not normal. They impact our heath, either through disability, pain and have a negative impact on quality of life. Excessively flat feet, for example can be strongly linked to a large variety of conditions affecting the foot, ankle, lower limb and lower extremity. Flat feet can be correlated with conditions such as plantar fasciopathy, Achilles tendinopathy, patello-femoral pain and many other disorders of the lower limb. Flat feet are strongly correlated with a disorder called tibialis posterior tendinopathy, which tends to be a progressive condition and at its worst is very serious and debilitating. People with this disorder progressively develop a worsening flat foot on the affected side. In early to middle stages, foot orthoses, worn in deep stable footwear can be effective treatment. Sometimes an ankle support is of additional use. These measures can be augmented by strengthening the tibialis posterior muscle, but as this disorder progresses, patients may need to trial walking boots and if necessary, require surgical intervention. I see little value in the use of corticosteroid injection into a chronically diseased tendon and so do not recommend this type of treatment. Oral anti-inflammatories have a role to play during intense episodes of pain or as an interim measure, but again, they have no place in terms of providing a definitive solution. 

Excessively high arched feet are correlated with lateral ankle instability (including inversion sprain of the ankle), peroneal tendinopathy (overuse to the tendons which run to the outside of the leg, ankle and foot) and tend to be poor shock absorbers. 

Abnormal function and structure of the forefoot can also cause secondary effects. A bunion (hallux valgus deformity) for example, can cause overload to the bottom of the 2nd metatarsophalangeal joint. Over time, this can cause pain to this joint and the progressive formation of a 2nd hammertoe deformity. Callous (hard skin) can then develop on the bottom of this joint, on the hammertoe and on the tip of the 2nd toe. This can cause pain and issues with fitting shoes comfortably. Overload the 2nd and 3rd metatarsophalangeal joints and cause jamming to the base of the 2nd and 3rd metatarsals at the level of the cuneiform joints, causing osteoarthritic change at this level. Therefore, the patho-mechanics of a bunion can not only affect the bunion itself (or the 1st metatarsophalangeal joint) but also other joints as well. It is for these reasons that a bunion is a serious foot complaint. Bunions have great potential to affect quality of life through pain, difficulties with footwear fitting and by reducing a person’s mobility (and even balance). 

Other conditions of the forefoot can affect the mechanics of the foot. Arthritis in the big toe joint can cause a person to supinate their foot (roll it to the outside), which upsets the normal load patterns of the forefoot (ball of foot) and may overload the outer edge of the foot, causing lateral ankle instability.

Summary – Normal vs abnormal

I have discussed a few examples on how it is important to understand what constitutes a normal foot, in terms of structure and function, what constitutes an abnormal foot and how this can vary from patient to patient. It is important to have a detailed understanding of these parameters, if one is to perform surgery on the foot. A great deal of foot surgery is about restoring the structure and function of the foot to within the boundaries of normal.

A podiatric surgeon will explain to you why you require your surgery and the objectives of the intervention. Potential complications associated with surgery should always be discussed.

Non-surgical interventions vs surgery

In most instances, your surgeon will need to be convinced you have explored non-surgical intervention before they will consider placing you ‘under the knife’. This is good practice. In some instances, surgery is likely to be the best option, if it is clear non-surgical intervention will be ineffective. For example, I see little value in non-surgical methods of treatment in symptomatic end stage hallux valgus deformity (ie – large bunions) and hallux limitus/rigidus (osteoarthritis affecting the big toe joint) in the setting where it is clearly affecting a patient’s mobility and quality of life. The same can be said for a foot deformity which is clearly placing someone with diabetes at risk of a foot complication.

Surgery isn’t always the best method of treatment in the first instance. For example, plantar fasciopathy, a common cause of heel pain, almost always responds well to non-surgical interventions. However, there are a small number of people who don’t respond to such treatments. It is at this point when surgery should be seriously considered. An instep fasciotomy may be what is required to treat these patients.

Summary

1) Many disorders of the foot respond well to surgical intervention. However, non-surgical treatment should in most instances be trialled first, before progressing to any invasive treatment.

2) The foot and ankle surgeon should have a detailed understanding of his/her patient. This includes their general medical history and a detailed overview of what the complaint is and how it has been managed thus far. The surgeon should be prepared to inform the patient of the rationale behind the surgery, explain the risks involved and what will be required during the healing and recovery stages. Other treatment interventions, if relevant, should also be considered and discussed.

3) Podiatric surgeons are highly skilled specialists, recognised by APHRA (in Australia) and have introduced many innovations to patient care and management.

4) The specialty of podiatric surgery should be integrated into the public health sector in Australia (equivalent to the USA and UK models), improving health outcomes for patients, because they will have greater access to the services of podiatric surgeons.

Reference: (PDF) Biomechanics of the normal and abnormal foot. Available from: https://www.researchgate.net/publication/12654398_Biomechanics_of_the_normal_and_abnormal_foot [accessed Aug 16 2018].

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