Design & Theory
The design and theory of an orthosis must
take into account the intended outcome. Based upon triplanar
control of forces acting on the body, skeletal alignment
must be restored and support must be applied where it is
needed. Stability and balance need to be established as a
prerequisite for efficient walking
The complexity of design and theory will vary according to individual needs and requirements. In order for the design and theory to be effective, the materials selected must meet the demands of the design.
An orthosis is required when there are mechanical deficiencies that affect normal human biomechanics. Each bone has an established anatomical position. The anatomic position usually describes a specific static position of a human. All deviations from this position are either compared, measured, related to within normal and abnormal parameters by the three cardinal planes.
Human movement can be broken down by its movement of individual body segments. Each body segment has normal ranges of motion (ROM) in one, two or all three planes. The combination of all the body segments and positions they can obtain are infinite. The normal range of motion has its limits based on anatomical design.
Pathomechanics is the study of biomechanics gone wrong. Prolonged abnormal forces tend to stretch ligaments and tendons as well as, abnormally compress one side of joint surfaces and open up and unload the other aspects of the joints. This will lead to premature wearing of joint surfaces. Joint surfaces normally are designed to tolerate equal loading when they are congruent. These joints will last a lifetime with normal usage. Pathomechanics once it starts will continue to worsen unless all the structures are properly supported. The Range of Motion of joints often go beyond normal limits under pathological conditions. This is compounded by abnormal positions of these segments which magnifies pathomechanics.
There is a complex relationship of balance between bones, muscles and nerves all working in unison to maintain the anatomic position. The anatomic position usually describes a static position of a human. There are also dynamic anatomical positions. Each activity or action defines the relationship of human structures in three dimensions all the way through the movement cycle.
Defined by human design, there are efficient and inefficient movement strategies for each action. Athletics is an example of defining the most efficient human movement strategies for specific activities.
Any alteration to the skeletal or neuromuscular systems impacts efficiency. There is nothing simple about any individual system and especially as they relate to each other. The cause and effect of something construed as simple to the skeletal or neuromuscular systems are complex as the body compensates for the deficiency. This compounds with multiple deficiencies and the longer they are not recognized and solved.
Proper design and theory of an orthosis must solve as much, if not all the deficient human mechanics. The design must incorporate triplanar control techniques since all joints within the foot are triplanar in nature. All the deficits affect the three dimensions of human locomotion. Solutions designed for each deficit must be visualized and rectified in each of the three cardinal planes.
Triplanar control techniques and designs maximize or reestablishes structural alignment of the kinetic chain, balance and muscle efficiency are improved. The human body has narrow parameters for efficient and secure ambulation. Every attempt should be made to realign each bony segment in each of the three planes and controlled under load bearing applications, such as ambulation.
Triplanar control when applied properly will also decrease anxiety of standing and walking by reestablishing balance and muscle efficiency. Compensations will be minimized or eliminated. Anxiety seems to exacerbate tone for those with upper motor neuron issues and compensations. This tends to limit motivation and desire to walk.
The design and theory behind conventional bracing does not support that Triplanar control exists. All the measurements, angulations and compensations of people wearing conventional designs show there are design elements lacking to restore human locomotion to the most efficient capability. In many cases, conventional braces have made things worse compared to the bare foot baseline.
Function can only be maximized once structural alignment of all bony segments in the three cardinal planes is achieved. Orthoses should accomplish what prostheses accomplish. An orthoses must solve mechanics of the stance phase for a person to learn to trust the device. Function will improve with better understanding. The science of mechanics can be measured, we must quantify our outcomes. We must prove our designs and theories work.
It is our belief, that as a profession, we make too many swing phase control orthoses and not enough stance phase control orthoses. We believe we do not make enough triplanar control orthoses and fit too many single plane devices on three dimensional problems. We believe the mechanics that govern prosthetics also govern orthotics.
We believe thermoplastics (Polypropylene and co-poly) are not strong enough to withstand floor reaction forces required for triplanar control under load bearing applications, such as human locomotion. The materials deflect too easily and in unpredictable directions. Studies has shown as the materials deflects when it should be solid and secure, that they will make compensations for balance and security.
We ask, why are there no polypro prosthetic feet? Why are there no "free dorsiflexion" prosthetic feet?
We believe Polypro deflects too much and in an uncontrolled direction. Yes, we can influence these factors by design and thickness. But, we can not control the true line of progression and it's controlled resistance. The material becomes more and more flexible with repetitive cycles of dorsiflexion. This directly affects the trust factor in the stance phase. Efficiency is always lost when humans are forced to solve their security issues with compensations.
From the article:
"Design Changes in Ankle-Foot Orthosis Intended to Alter Stiffness Also Alter Orthosis Kinematics"
- In contrast, the stiffness decreased with increasing dorsiflexion. This appeared to be because of buckling of the medial and lateral edges of the orthosis as they were compressed during dorsiflexion. This was the only orthosis that showed this substantial (50%) decrease in stiffness with increased dorsiflexion. This might be important for patient acceptance as decreasing stiffness in dorsiflexion may result in a feeling that the orthosis was collapsing or "giving way" and may result in altered gait to avoid putting the foot into dorsiflexion.
Design and Theory to reestablish efficient human locomotion is more complex than what is currently taught and accepted in all the medical disciplines that relate to developing solutions for people with physical limitations. Specialized medicine is a godsend for most applications and sometimes too focused to assess the whole picture. Each medical specialty developing their own body of knowledge and terminology to explain it, often creates communication problems between them. Treatments are developed sometimes for the resultant effect of a deficiency, with no respect to the underlying cause. People have had multiple back surgeries, hip or knee replacements, patella subluxations and an assortment of foot ailments and procedures that could have been solved with solutions that restored ones biomechanics from the ground up.
Solutions are developed by assessing the cause and effect of the global problems in space and by looking much deeper within the structures for the answers. The Solutions integrate mechanical and movement strategies to reinforce security and efficiency.
Outcomes based on our new bracing technologies have been proven to work best with gait training techniques similar to those utilized by some 25-30 years ago. Integrating the right technologies and techniques is key to success. Understanding of the new technologies and techniques and how and why they were developed plus how and why they work together is paramount to the professionals and person in need. Reinforcing the same terminology and techniques by the medical team will help the person and family reach their goals.
In the purest state, the rehab of an individual is when all forces are working for the betterment of the individual to restore function that has been lost. Any entity that detracts from this cause should be eliminated or redirected in a positive direction. Failure to recognize the wrong device, the wrong professional, the wrong treatment, the wrong advice, or the wrong solution will undermine the potential of restoring lost function. Even the individual may undermine themselves for various reasons.
Our solution development works in a similar fashion, we look for any deviations in the wrong direction at the wrong time and in what plane. All deviations detract from the net force of moving forward in an efficient and secure manner. All deviations must be assessed for the cause and effect and how they relate to the cause and effect of other structures.
For each individual we look for the mechanical components and the motion components that must work together. This is why like-minded clinicians from the medical disciplines are being licensed to enhance an individual's chances of restoring function.