Static and Functional Biomechanical Diseases: Hypermobility Syndromes

Functional Biomechanical Disease Module 1

Basic Foot Types

Key Points to Remember. . . Treat the symptom and the cause = Maximize patient care and results.

Anatomy

Functional Biomechanical Specialists tend to break the foot into 4 unique quadrants. Each has a special function.

3D = Transverse - Sagittal (Frontal) - Lateral Body Planes

You must think 3D when you understand or work in the field of Biomechanics. Every plane is affecting the injury or diseased part of the body.

Shock Absorption V Stability

The Foot is a Tri-Plane Motion marvel.

It works in all three body planes simultaneously.
Its function is affected by all body planes
It functions as a Shock Absorber along with the Knee at Heel Contact and when the forefoot approximates the floor, it instantly changes into a Rigid Stabilizer for the absorption and effective transmission of mass into the propulsive phase of the gait cycle.
Understanding Foot Biomechanics is Key to the proper foundational analysis of Cyclic Load Mechanics of the body. If you treat leg, knee, hip, pelvic, or spinal structures, you must include foot biomechanics because body mass, motion, balance, pressure, gait, and symmetry all stem from the body interacting with the floor through the foot. 3DO Imaging simplifies this task through software analysis.

Environmental Factors that can accelerate Disease

Man Made Terrain

The body is not made to interact with Man Made Surfaces, (cement - tile - asphalt). It is a variable terrain adapter designed for uneven surfaces. When the foot is subject to consistent flat hard terrain, abnormal kinetic loads are created leading to structural and or functional diseases.

Extrinsic Musculo-Skeletal Forces

Sedentary lifestyles can influence conditions such as Equinus. Equinus is a very unstable and deforming sets of forces affected by congenital or acquired muscle group shortages.

Lateral Plane (x) = Abnormal Forward Mass Migration from Equinus

Normal Foot Position (Frontal Plane) and Lateral Mass Migration of Body

Footwear

Man made footwear is a another additional set of conditions that adversely affect abnormal static and dynamic cyclic load conditions. From fashion footwear to ill fitting shoes, all contribute to additional forces which can affect all load bearing structures.

Pediatrics - Children

Early detection is the key to successful treatment. Evaluating children starting at the age of 5 to age 22 is critical in providing adequate structural and functional correction. As bones grow, we can affect structural change for the better.

Wolff's Law - Our goal is to minimize these effects

Wolff's law is a theory developed by the German anatomist and surgeon Julius Wolff (1836–1902) in the 19th century that states that bone in a healthy person or animal will adapt to the loads under which it is placed. If loading on a particular bone increases, the bone will remodel itself over time to become stronger to resist that sort of loading. The internal architecture of the trabeculae undergoes adaptive changes, followed by secondary changes to the external cortical portion of the bone, perhaps becoming thicker as a result. The inverse is true as well: if the loading on a bone decreases, the bone will become weaker due to turnover, it is less metabolically costly to maintain and there is no stimulus for continued remodeling that is required to maintain bone mass.

Mechanotransduction

The remodeling of bone in response to loading is achieved via mechanotransduction, a process through which forces or other mechanical signals are converted to biochemical signals in cellular signaling. Mechanotransduction leading to bone remodeling involve the steps of mechanocoupling, biochemical coupling, signal transmission, and cell response. The specific effects on bone structure depends on the duration, magnitude and rate of loading, and it has been found that only cyclic loading can induce bone formation. When loaded, fluid flows away from areas of high compressive loading in the bone matrix. Osteocytes are the most abundant cells in bone and are also the most sensitive to such fluid flow caused by mechanical loading. Upon sensing a load, osteocytes regulate bone remodeling by signaling to other cells with signaling molecules or direct contact. Additionally, osteoprogenitor cells, which may differentiate into osteoblasts or osteoclasts, are also mechanosensors and may differentiate one way or another depending on the loading condition.

Hypermobility Syndromes

Foot Types Involved (2)

Hypermobile Pes Planus (Common Flatfoot)
Hypermobile Pes Cavus (Rare Disorder)

Both of these conditions cause extremely unstable cyclic load conditions affecting the leg, pelvis, and spine.

Pes Planus - Transverse & Frontal Planes

This is a very common orthopedic condition which creates a wide array of pain syndromes in the foot, leg, pelvis and spine. All three body planes are affected with this disorder.

The foot fails to wedge-lock rearfoot (subtalar) joints against midtarsal joints, and leaves the 1st Ray (navicular - medial cuniform - 1st metatarsal - hallux) unstable and hypermobile. This creates a functional forefoot varus condition. As a result, the medial forefoot collapses taking the leg into excessive transverse plane rotation. This offsets patella glide in the knee, it also creates excessive pelvic rotation and resultant lumbar pressure.

Normal Frontal Plane Alignment of Rearfoot to Forefoot

Left = Non Weight Bearing (Forefoot Varus) Right = Forefoot collapse with Rearfoot Valgus

Pes Planus - Lateral Plane
Equinus conditions (discussed above), increases mass displacement and pronatory motion substantially. This accelerated force, increases the kinetic load trauma to the foot and load bearing skeleton structures.