Author: Fred Kahn MD, FRCS (C)
Source: Meditech International Inc.
Today, as individuals age, they maintain an active lifestyle and this frequently presents problems relating to the health of the foot. Up to 80% of individuals over 50 years of age will experience challenges of this nature in their lifetime.1,2 Often the symptoms are ascribed to “tired feet”, particularly after a day of hiking, gardening or playing a vigorous round of golf. The problems that occur may restrict activity levels that are essential to maintaining a normal lifestyle and may reduce the quality of the patient’s existence, secondary to the pain experienced.
Initially there is a mechanical loss of power, along with deterioration of the musculoskeletal tissues as ageing progresses3–5. These changes are coupled with a reduction in arterial perfusion, resulting in a decrease in soft tissue volume. The latter is characterized particularly by the atrophy of the fat pads that cushion the foot6. Collectively, these changes render the foot in an increasingly vulnerable state.
These naturally occurring changes in the foot are further exacerbated by other disease processes including degenerative osteoarthritis, arterial occlusive disease, osteoporosis, diabetes and trauma. These diseases individually may constitute the primary cause of pain or they may be important contributors to the progression of those painful sensations experienced with activities involving the ageing foot.
The treatment options currently available are somewhat limited. They include exercise, orthotics and massage which can alleviate some of the biomechanical factors that may be encountered. Laser Therapy however provides a unique therapeutic option that can target the source of the problem and promote both healing and regeneration of tissue.
The objective of this paper is to discuss our understanding of the pathophysiological changes of the ageing foot and provide insight into currently available and effective therapeutic options.
ANATOMY OF THE FOOT AND ANKLE
The human foot is a complex array of tissues, relatively stable but with a considerable degree of flexibility. Its multiple joints, lined with cartilage, are supported by an intricate network of ligaments, tendons and muscles. It is a well-designed, strong, yet flexible structure which is required to support the weight of the entire body and withstand high-level forces of compression during activities such as walking, running and jumping.
The foot contains 26 bones of varying dimensions and additionally 2 sesamoid bones. It is divided into three distinct sections: the forefoot consisting of 5 metatarals and 14 phalanges, the mid-foot containing the medial, intermediate and lateral cuneiform bones, the cuboid and navicular bones and the posterior portion consisting of the talus and calcaneum. All of the joints contain synovial fluid to minimize friction during movement. A strong matrix of ligaments maintains stability while facilitating effective movement7.
The ankle is a more mobile structure and includes the tibiotalar and the subtalar (talo-calcaneal) joints. The lateral aspect of this joint is represented by the fibula. The joints are stabilized by the extensive deltoid ligament medially and a collection of three other ligaments: the anterior talo-fibular, the posterior talo-fibular and the calcaneo-fibular ligament laterally.
The muscles that enable movement of the foot consist of two groups. The intrinsic group, where both origin and insertion of the muscles are located on the bones of the foot itself (i.e. flexor digitorum brevis, flexor hallucis brevis and the interosseous muscles) and the extrinsic group, where the origin of the muscles is above the level of the tibiotalar junction and the insertion is on a bony prominence of the foot (i.e. tibialis anterior, posterior tibial tendon, gastrocnimeous, peroneous longus and brevis). The plantar aspect of the foot consists of several layers containing the muscles, the plantar fascia, the fibrous-fatty layer which cushions the foot, a thick protective cover known as the dermis and epidermis.
BIOMECHANICS OF THE FOOT
The primary purpose of the foot is to support the body in an upright position and to accommodate movement in various directions. A high level of mobility exists at the tibiotalar and subtalar joints, allowing for motion to occur in three planes (i.e. the sagittal, transverse and frontal planes). The extrinsic muscles are responsible for flexion and extension of the ankle joint, inversion and eversion and also abduction and adduction (Figure 2). The joint, which is of extreme importance in stabilizing the foot while weight bearing, is the transverse tarsal joint. This is made up of the talonavicular and calcaneocuboid joints, also known as ‘The Joint of Chopart’.
Stability in the foot is achieved by the arches formed by a number of anatomical structures. The longitudinal arch is subdivided into the medial and lateral aspects. The medial arch is higher and is characterized by its elasticity and a number of small joints constituting its components. The arch is additionally supported by the plantar aponeurosis, the small muscles in the sole of the foot, the tendons of the tibialis anterior and posterior, and the ligaments of all the small articulations involved. Because of the elastic properties and the architectural design of the longitudinal arch, contact forces can be spread over the arch. This characteristic can reduce the risk of musculoskeletal wear or damage. The ligaments also absorb and store the energy of the impact forces, converting them at the next step and thereby reducing the expenditure of energy during motion. Essential structural ligaments such as the calcaneonavicular (spring) ligament support the weight of the body as it is downloaded onto the foot. Interestingly, 1.5 times the body weight moves onto the forefoot while walking and 3 times the body weight during running8. As such, stability and strength in these structures are fundamental to good foot health.
The medial arch is smaller, lower and more rigid. It is made up of strong ligaments and muscles to preserve its integrity. A series of transverse arches run from the heads of the metatarsals to the calcaneum and again are supported by the numerous ligaments, tendons and muscles of the foot.
The Phases of Gait
Heel strike is the first contact with the ground wherein the anterior compartment muscles keep the foot dorsiflexed. The main shock absorption occurs during the early flat foot period. At this point, the anterior compartment muscles have slowly lowered the forefoot. During late flat foot the tibia moves past the body’s centre of gravity. The posterior compartment muscles are in eccentric contraction and the foot becomes a rigid lever to propel the body forward. At early heel raise the posterior compartment muscles are now actively contracting. The foot then leaves the ground at push off and the majority of the weight is now on the opposite foot. The joint of Chopart provides the necessary rigidity to the foot during the early heel raise portion of the gait and at push off. During the swing phase the anterior compartment muscles keep the forefoot dorsiflexed and the joint is in a relatively relaxed state until heel strike. The relaxed state of the swing phase and the ensuing heel strike are important points of vulnerability as one cycles through the phases of the gait.
PATHOPHYSIOLOGICAL CHANGES IN THE AGEING FOOT
The foot is subjected to considerable “wear and tear” over decades of use. While rarely considered, it encounters the innate challenges of ageing similar to the rest of the body. Specifically, the foot is subject to circulatory, structural and dermal problems that can result in severe pain and disability in older populations.
The cellular components of the various tissues of the foot include osteoblasts, osteoclasts, myocytes, neurons and fibroblasts, undergo functional changes during the ageing process. All cells of the body exhibit decreased telomere length with continued replication that can limit the lifespan of the cell and therefore limit its functional capacity9. These cellular changes can have a number of important consequences.
It has been proposed that there is a reduction in the number of osteoblast precursors as well as the lifespan of the osteoblast3,10. As such, the balance of bone turnover and the stability of the trabecular network are disrupted with age contributing to significant loss of structural integrity and overall bone mass3.
Neuromuscular alterations, in particular diminished motorneuron activity, have been proposed to underlie subsequent apoptotic loss of muscle cells4. Decreased levels of growth factors and atrophy of muscle fibres can contribute to sarcopenia, involving both intrinsic and extrinsic muscles. There is a cumulative loss of type I fibres as well as an even more significant loss of type II fibers with increasing age11. These changes can account for a characteristic 20-40% loss of muscle strength during the ageing process11,12.
Additionally, there is an increase in the latency of nerve conduction in both motor and sensory pathways which may result in weakness, numbness and tingling13. Collectively, these changes can contribute to a decreased range of motion, stiffness and pain. In spite of these naturally occurring losses in muscle mass and strength, the capacity to enlarge a muscle with resistance training is retained, even in older individuals4. This supports the notion that appropriate exercises can help strengthen the muscles of the foot.
Fibroblasts which are responsible for maintaining connective tissues including collagen, elastin, proteoglycans, fibronectin, tenascin and laminin of the body also undergo functional changes during ageing14,15. Typically, they act on three growth factor signalling pathways: the MAP kinase pathway, the PI 3 kinase pathway and the Smad pathway16. When the fibroblast exists in an aged state, there is decreased activity in the PDGF and Smad pathways leading to decreased ERK and Akt expression as well as decreased TGFß type II receptor expression16. During ageing there is also an increased JNK level16. The fibroblast cells lose their connections to collagen fibres and the dissociated fibres become more susceptible to fragmentation and breakdown by metalloproteinases15. This is of particular relevance since collagen provides the matrix for the skeleton, the soft tissues and muscles, all of which support the body’s internal organs. The decline in collagen levels is significant with ageing, amounting to 1% per annum after the age of 20 years17. Coupled with these changes there is a reduction in elastin gene expression, increased levels of elastin peptides, matrix metalloproteinase-2 and consequent elastin degeneration18,19. Collagen and elastin are necessary to maintain the elasticity, moisture content and firmness of the skin. This loss of structural integrity of the collagen matrix underlies the appearance of human aged skin and the development of wrinkles.
The skin itself can become dry (Xerosis) and vulnerable to ulceration as a consequence of a reduced blood supply1. Edema increases, along with venous pooling, secondary to incompetent valves in the perforators. In patients with concomitant medical conditions, such as diabetes and neuropathies, deterioration accelerates1. As arterial perfusion diminishes, the ability of tissues to recover and regenerate new cells is significantly reduced.
Finally, atrophy of the fibrous fatty pockets underlying the distal heads of the metatarsals and the calcaneum contribute to diminished cushioning of the feet1. Consequently, the underlying skeletal structures receive less protection and are more vulnerable to trauma and repetitive use injuries.
CONDITIONS CAUSING PAIN IN THE FOOT
There are many problems that contribute to the pain experienced in the ageing foot. These can be categorized into a number of groups:
- Plantar Fasciitis: This is characterized by inflammation in the plantar fascial ligament, located in the heel. Pain may extend to the arch and is often more severe in the morning. Pes planus, low back pain, footwear that is inappropriate and obesity are all factors contributing to this condition.
- Osteoarthritis: Increasing age, along with activity, erodes cartilage in the joints resulting in inflammation of the tissues characterized by pain, edema and deformities.
- Gout: This is an inflammatory condition in which crystals of uric acid are deposited in the joints and soft tissues, causing severe pain and edema. The 1st toe is most frequently affected by this disease.
- Rheumatoid Arthritis: This is considered to be an autoimmune disease characterized by inflammation of the soft tissues and joints with extensive damage to the latter. Joints in all areas of the body may be affected by this disease process.
- Athlete’s Foot: This is a fungal infection of the feet, resulting in dry, flaking, erythematous, and irritated skin. Daily washing and keeping the feet dry can prevent this problem, along with suitable topical applications.
- Infection of the Diabetic Foot: Individuals with diabetes are vulnerable to infections, which are often more severe than preliminary examination might suggest. Diabetics should examine their feet daily with regard to any injury and signs of developing infections, including erythema, edema and pain.
Plantar Warts: A viral infection over the plantar aspect of the foot that can form a callus which may be acutely painful.
- Fungal Infection of the Nails: This type of infection creates discoloration, generally yellowish in nature, produces irregularity and physical deterioration of the nails of both the digits and toes.
- Bunions (Hallux Valgus): This presents as a bony prominence generally over the medial aspect of the MP joint of the 1st toe. This deformity exists with lateral gravitation of the toe. It is often accompanied by hammertoe deformity of the 2nd toe. These may have a hereditary basis but more frequently are the result of inappropriate footwear.
- Achilles Tendon Injuries: These are often secondary to athletic injuries and restrict the ability to be ambulatory. The condition can be sudden in onset and relatively acute or chronic in nature. Lower body injuries may also be a causative factor.
- Calluses/Corns: A buildup of keratin over an area subject to friction or pressure on the foot, most frequently noted over the 1st metatarsal head or the heel. This diagnosis is often overlooked in numerous cases. Osteoporosis can be a contributing factor.
- Fracture: The metatarsal bones are the most frequently fractured bones in the feet, either from injury or repetitive use. Pain, swelling, erythema, and hematoma formation may be signs of a fracture.
- Heel Spurs: This is an abnormal growth of bone usually located at the posterior aspect of the heel, which may cause severe pain while standing or walking. It is generally secondary to trauma or the result of fascial or ligamentous injury. It is often present in individuals suffering from plantar fasciitis, etc. but more frequently is a radiological finding without symptoms.
- Ingrown Toenails: These are frequently caused by poor hygiene, ill-fitting footwear and improper trimming of the nails.
- Fallen Arches: Also termed flat feet or pes planus. The arches of the feet flatten during standing or walking, or frequently without any activity being involved. These potentially cause secondary foot problems. This condition can be corrected with appropriate footwear and properly structured orthotics, if necessary.
- Mallet/Hammer Toes: The joints in the toes may lose the ability to extend causing the toe to develop flexion contractures.
- Morton’s Neuroma: This consists of a growth comprising digital nerve tissue generally present between the 2nd and 3rd or 3rd and 4th toes. This may be extremely painful on palpation and often improves with a change in footwear.
- Metatarsalgia: This condition is among the most common reported in patients presenting with pain in the feet. It is characterised by pain and inflammation across the plantar aspect of the forefoot or the second, third and fourth metatarsal heads. Metatarsalgia is frequently associated with deformities of the hallux and phalanges, ill-fitting shoes, loss of soft tissue with an increase in age and the repercussions of an abnormal gait.
THERAPEUTIC SOLUTIONS AVAILABLE
- Proper Foot Care
This consists of bathing in warm saline nightly and subsequently massaging with a hydrating lotion or cream. Periodic pedicures can often provide significant benefit, including the proper cutting and maintenance of the toenails and dealing with any other abnormalities as they present.
- Correct Footwear
Wearing properly fitting shoes can prevent most problems of the foot; it is therefore extremely important to have shoes properly fitted prior to purchase. Some considerations that should be observed when purchasing shoes include the following:
- The foot goes through changes in size as the person ages and during the course of the day. As such, an assessment of foot size should be made late in the day
- when edema is present at its maximum extent. Further, this sizing should be re-evaluated intermittently as the individual gets older.
- Feet may be asymmetrical. One foot is generally larger than its opposite by one half to one full size. The choice of shoe size should be determined by the larger foot.
- It is best to select shoes wherein the upper part of the shoe is made of a soft flexible material that conforms to the shape of the foot.
- The shoe should not be too tight and should be of adequate width as the tensile strength of different materials cannot be easily predicted and the damage caused by tight shoes can be severe.
- The sole of the shoes should consist of a thick cushioning-type material that mitigates the impact during activities such as walking or running. The contact area of the sole should provide stable footing and traction.
- It is optimal to choose low heeled shoes which are safer, more comfortable and support a more “natural” anatomical configuration. (Asics, New Balance and Ecco brands are highly recommended)
Orthotics are generally separated into two categories – functional and accommodative. Functional orthotics are designed to support feet demonstrating abnormal biomechanics. They are useful to reduce pronation, ease shock absorption and correct a number of deformities while supporting the rear and mid-foot regions. Accommodative orthotics consist of more elaborate splints, casts and braces to correct the gait when problems arise from neurological conditions, including CVAs. Orthotics can also be used in instances of hallux valgus to prevent the condition from becoming a severe impediment. On the whole, their value depends on the construction and fitting which largely depends on the skill of the individuals designing these corrective devices. Moreover, shoes should be properly sized to accommodate the insertion of orthodics. It should be noted that orthotics often provide limited benefit and their employment may be counterproductive.
There are numerous exercises and physiotherapy programs to prevent or slow atrophy of the muscles in the foot. These, often simple solutions, can be time consuming however can be of some benefit. The majority of the fundamental strengthening exercises include the use of rubber bands for resistance work and the use of small objects to be picked up with the toes, along with some balancing exercises.
- Pharmaceutical options
The current therapeutic options available for the treatment of the majority of painful conditions of the foot consist of pharmaceuticals targeting the inflammatory pathways or to mask pain. These drugs are divided into steroidal (i.e. cortisone injections or oral ingestion) and non-steroidal anti-inflammatory compounds (eg. ibuprofen, acetaminophen, etc.). These vary in dosage and the length of time that they provide relief from symptoms. In all situations it is preferable not to utilize medications over an extended period of time. Most medications exhibit reduced efficacy with prolonged use, carry significant potential to induce adverse effects and can negatively impact the healing of damaged cells.
One in four women has osteoporosis and as a result, pathological fractures continue to be a leading cause of disability and occasionally mortality. Nutrition is an important factor in the prevention of osteoporosis. Specifically, a number of supplements and vitamins have demonstrated efficacy in promoting increased collagen levels. These include magnesium, vitamin D, vitamin K2, vitamin D3 and biotin. Biotin is most easily found in nuts, egg yolk, wheat bran, oats, barley, liver and porous yeast.
- Low Intensity Laser Therapy
Laser Therapy is a non-invasive technology, also known as “Phototherapy”. Photon particles are emitted by superluminous and laser diodes in the 660 to 840 nm range. The light source is placed in contact with the tissues, permitting therapy to both the superficial structures and those at deeper levels, resulting in the restoration of normal morphology and function of the cells.
The wavelength of light utilized is specifically designed to be absorbed by cytochrome c oxidase, one of the main mitochondrial membrane proteins, responsible for cellular energy production. The saturation of these proteins stimulates cellular metabolic processes, enhancing the specific functions of each individual cell.
Laser therapy can increase the production of endogenous opioids, which in turn engenders an analgesic effect. It produces a potent anti-inflammatory effect and promotes the regeneration of new cells including fibroblasts via an increase in the levels of basic fibroblast growth factor (bFGF) 20,21. The heightened proliferation rate of fibroblasts in turn can contribute to greater production of connective tissues, including procollagen type I and III as well as elastin22,23.
Additionally, Laser Therapy can increase angiogenesis, which is the formation of small collateral arteries, arterioles and capillaries resulting in increased arterial perfusion. These physiological activities will increase the blood supply to the foot. In turn, this has the potential to counter some of the secondary effects that occur in the ageing process and accelerate the regenerative process. Additionally, Laser Therapy can offer a myoprotective effect, preventing the apoptosis of myonuclei24. As such, a prolonged course of Laser Therapy directly and positively impacts the majority of the problems of the ageing foot.
ADDRESSING THE CHALLENGES OF THE AGEING FOOT AT MEDITECH
Whereas treatment at our therapeutic centres is preferable, patients can also obtain optimal outcomes using a Home Unit 4-5 times per week without attending a clinical centre. Benefits may be evident after the initial 5-6 treatment sessions and complete healing is accomplished over a period of 1-4 months. Continuing preventative therapy, 1-3 sessions per week utilizing a Home Unit, will prevent recurrence and continue to stimulate the generation of new tissue.
Laser therapy is an effective technology for the treatment of tissues that have been subjected to prolonged wear and tear. It can offer effective treatment to counter atrophy, degeneration, inflammation, biomechanical problems and other conditions that may result in pain, an antalgic gait and impaired function. Healthy connective tissues, including muscles, ligaments and tendons are essential to the normal function of the foot.
CURRENT RESEARCH AND INNOVATIONS
Methods of measuring increases in tissue volume are being developed by our organization to validate the utilization of Laser Therapy in the restoration of tissue mass. Furthermore, we are establishing the efficacy of applying Laser Therapy over a period of time to promote regeneration of the connective tissues in order to provide permanent symptom relief.
A preponderance of the conditions causing pain in the ageing foot require anti-inflammatory and regenerative therapy in order to achieve resolution of the pathologies involved. Pain is invariably associated with inflammation and laser technology is the preferred method of eliminating this problem. As the active inflammatory process subsides, tissue remodeling proceeds, resulting in the return of normal, pain-free function. It is our observation that a prolonged course of Laser Therapy induces the regeneration of tissues, along with a concomitant increase in the volume of the structures involved. The application of Laser Therapy to the conditions discussed in this paper should be considered the solution of choice in the treatment of the painful, ageing foot.
References available upon request