The science of orthoses

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The science of orthoses

 

At the Chelsea clinic, we are currently studying for our PhD in material science.

This makes us appreciate and differentiate why material selection from the shell itself to the top, mid and bottom layers of bespoke orthoses are specifically chosen for each and every individual client’s pair of feet walking through our door.  We then believe the best way to capture your foot is by using plaster of Paris mould. This allows us to place your foot into an optimal stabilizing position.

Once the casts are ready and marked accordingly we then decide upon device type, postings, dressing modifications, accommodations and additions specific for you.  The art of prescribing orthoses is a creative endeavour but based on the latest emerging science and principles.  Perhaps some similarity to the role of an Architect designing the best house foundations in order to achieve a long-standing, strong and stable base able to withstand even the severest of environmental challenges.

Materials and magic? 

The science of material selection for the parts that comprise a prescriptive orthosis it is important that your suitably qualified clinician considers just some material phenomena such as friction or force, shear direction, yield, creep deformation or fatigue, optimal stress zones, stress concentration zones, torque over a cross-section, weight of your client, footwear, activities undertaken, activities desired to be undertaken as just a few examples.

By ensuring joints and soft tissues are adequately offloaded, providing a foot, (or ankle pair of orthoses), that can introduce moments of force in order to change the way muscle activity operates will not only allow the foot to function more energy efficiently but it can positively affect and delay the onset of wear and tear due to reducing pressure at painful, (even non-painful areas), allowing your foot and ankle muscles the chance to activate optimally and for the long term.  This is not to say orthoses that you had prescribed 5 years ago will be working as well today as your feet will have changed.  However, in the instance of injury, it may even be that you now no longer require orthoses.

Conversely, you may have arrived at a stage never having had to have any intervention but the time has come that your foot cannot adapt by itself any longer and conservative intervention such as a pair of orthoses is now necessary.

How do we walk? 

As bipedal mammals mother nature has not been too kind to us.  We would have benefitted from being quadrupedal as with the vast majority of other mammals suffering less so from the vagaries of wear and tear found in our musculoskeletal joints, especially the weight-bearing joints such as the 5th lumbar vertebra articulating with the sacrum also known as the lumbosacral joint, our hips, knees and feet.  (National Institute of Aging, 2022).

During the stance phase of the gait cycle simply presented we perform a heel strike where one of our heels at the beginning of one gait cycle makes contact with the floor.  We then move into a foot flat where the same foot is in full contact with the ground and finally we toe-off where the last contact made is at the 1st toe of the same foot to ‘push off’ away from the ground.

These three described phases all take place in the stance phase.  The stance phase can be further subdivided and we have not mentioned the remaining 40% of the swing phase where our foot is now in a non-weight bearing.  (Nester et al., 2021).

Bipedal gait can present many challenges and can be excessively energy-demanding, especially in instances where excessive load occurs at certain joints and where other joints may be conversely underworking.  The body can adapt in some instances for long periods of time, however, usually when you are beginning to experience pain the body has already been adapting for long periods of time.

What can make walking comfortable? 

As a bipedal locomotor system, we want to ensure that we keep our centre of mass as close to the mid-point over the pubis as possible.  Avoidance of excessive pelvic tilting with our weight equally distributed through both limbs equally.

In addition, Kirby, (2017) states one of these engineering marvels of the human foot is the longitudinal arch and its unique and elegant load-sharing system, passive tissues aid to increase the stiffness of the longitudinal arch by increasing the pulley system namely the Achilles tendon tension and increasing plantar forefoot loads.

Moreover, the active elements allow the central nervous and the longitudinal arch load-sharing system to modify its stiffness and plantar locations, adapting to the magnitudes of ground reaction forces acting at the plantar aspect (sole) of the foot.  This unique anatomy facilitates an effective and also metabolically efficient design to cope with the force placed upon it with each and every step we take.  McNamee, (2016), cites that for an ankle that has a reduced range of motion, (namely a stiffer ankle), for every 1-degree loss of movement your risk of heel pain can increase by 15%.

It is now then recognized that foot orthoses exert their therapeutic benefit by modifying kinetic parameters (Dickinson, 2022).  Orthoses change the ankle and also foot eccentric muscle function.  By affecting muscle activity decreasing certain contact areas of pain and increasing other areas of contact where indicated can assist to reduce or increase peak pressures where needed.

What are your choices? 

At the Chelsea clinic, we cannot stress enough that therapeutic intervention for foot and ankle pain with orthoses should always be the first choice over for example a corticosteroid as there is much literature about the long term efficacy of steroid injections cited as poor further with more joint damage possible. Nichols, (2005), Scott & Khan (2010).  Further surgery should the vast majority of cases?  Be our very last choice.  Once surgery has taken place you cannot escalate any further this only leads to more surgery.  However, it must be elucidated that there are instances where surgery is the first choice in the presence of unstable fractures, severe pathology/collapse and notable in Lisfranc injuries for example.

At the Chelsea chiropody and podiatry clinic, we are able to access one of the only labs left in England that actually manufactures bespoke orthotics with a selected and extremely talented hand-picked team members all of whom have individual expertise to collaborate as part of a team producing hand made devices as oppose using laser machinery or other robotic manufacturing.  Although these alternative manufacturing processes are excellent they are not quite as precise for our standards.  This then allows us to be confident to create the exact designs for you.

At the same time forming very close relationships with the orthotists and technicians to check in at each stage of the process, sharing thoughts, rationale and discourse with the latest based evidence to ensure our desired outcomes are reflected within your finished pair of bespoke devices.

How to nudge the foot in the right direction? 

Given the choice of additions, accommodations, extrinsic or intrinsic posting, open-cell or closed-cell materials, shore density values, top layers, mid-layers, bottom layers and any combination of just some of the above-presented variations the well-versed podiatrist / orthotist knows how to affect muscle activity at the various stance phases of the gait cycle thereby allowing the painful foot/ankle complex opportunity to function by very simply put? Nudging the foot in the right direction.  (O’Connell, 2021, Munderderman et al., 2003, Yung-Hui et al., 2005,  Moisan et al., 2016 and Williams et al., 2003)

References

Dickinson, S.  (2022).  Biomechanics Course Lecture.

Firefly Gold, (2021). Sarah O’Connell: Playing a part in the treatment of plantar fasciopathy in Elite Athletes.  [online video] Available at: https://www.youtube.com/watch?v=4IddMBVTJjQ [Accessed 12/01/2022]

Kirby, K.A.  (2017).  Longitudinal arch load-sharing system of the foot

Rev Esp Podol. Vol.  28 no.1 :e18-26.

McNamee, M.J.  (2016).  Analysis of Plantar Fasciitis Risk Factors Among Intercollegiate and Recreational Runners:  A Matched Case-Control Study.  Texas State University.

Moisan, G and Cantin, V.  (2016).  Effects of two types of foot orthoses on lower limb muscle activity before and after a one-month period of wear.  Gait & Posture.  Vol 46 pp75-80

Mündermann, A, Nigg, B.M, Humble, R.N, Stefanyshyn, D.J.  (2003).  Foot orthotics affect lower extremity kinematics and kinetics during running.  Clinical Biomechanics.  Vol 18 No. 3.  pp.254-263.

The National Institue of Aging.  Osteoarthritis [online]  Available at: https://www.nia.nih.gov/health/osteoarthritis#:~:text=Osteoarthritis%20most%20commonly%20affects%20the,knees%2C%20hips%2C%20and%20feet.  [Accessed 23 January 2022].

Williams, Dorsey, S.III, McClay Davis, I, Baitch, S.P.  (2003).  Effect of Inverted Orthoses on Lower Extremity Mechanics in Runners.  Medicine & Science in Sports & Exercise.  Vol 35 No. 12.  Pp2060-2068.

Yung-Hui, L and Wei-Hsien, Hong.  (2005).  Effects of shoe inserts and heel height on foot pressure, impact force and perceived comfort during walking.  Applied Ergonomics.  Vol 36, no. 3.  Pp.355-362

 

Read our article about custom-made orthotics here https://www.thechelseaclinic.uk/custom-made-orthotics/

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Paola Ash at the Chelsea Clinic

At The Chelsea clinic we have a very specific skill set with regards the foot and ankle. Pleased to offer a bespoke service which is tailored to the individual. With over 20 years experience in the Fitness and Healthcare industry we are registered and qualified with the Health Care Professions Council, the College of Podiatry and the General Osteopathic Council.