Orthotics and Prosthetics





KEY FACTS





  • The use of orthotic devices varies in a fairly significant way depending on the training and background of the prescribing practitioner.




    • Various practitioners, including orthopaedic surgeons, podiatrists, physical therapists, and more, prescribe orthotics for various pathologies, and there are widely varying opinions about best practices.



    • With that being said, there are pathologies that unquestionably benefit from orthotics, and there are many themes in terms of types on inserts that are appropriate.




  • In certain pathologies, orthotic devices are an indispensable component of nonoperative treatment.




    • A stiff insert can be beneficial in hallux rigidus as well as midfoot arthritis and in recovery from metatarsal stress fractures.



    • Metatarsalgia ± hammer toes can be treated with a metatarsal pad often with some success. The accompaniment of a Budin splint may impart a greater success rate.



    • An arch support of some description is typically a large part of nonoperative treatment for the symptomatic flatfoot.



    • A cavus foot with a supple hindfoot may be manipulated into a better position with a relief underneath the 1st metatarsal head.




  • Differences of opinion with regard to orthotics largely center over the relative ubiquity of their need, i.e., many practitioners agree that their directed use is appropriate, while promoting them as a panacea for all manner of ills is likely inappropriate.







This picture shows all manner of accomodative orthoses. These inserts are meant to support the foot in its position, as opposed to pushing it into a more desirable position.








An Arizona brace is a solid ankle-foot orthosis that is rigid and accomodative. It is custom made for patients, although it can be bulky and make getting shoes on difficult.








This gel heel pad can provide some relief of pressure in pathologies, such as plantar fasciitis. It is simply a cushion to relatively offload the heel area without providing much structural integrity.








These contoured cushioned insoles are used more for comfort than to directly influence any particular pathology. These inserts are “off the shelf” and can be used for general comfort or in mild pathology.






Introduction





  • Orthosis is an externally applied device used to modify the structural or functional characteristics of the musculoskeletal system, an apparatus used to support, align, prevent, or correct deformities or to improve the function of movable parts of the body.



  • During static stance and ambulation, the lower extremities are subjected to external forces and moments. During normal function, these forces and moments are resisted or controlled by internal structures of the body. When internal structures fail, orthoses can modify external forces and moments to allow the body to function in a “normal” manner.



  • An external device used to support or improve function of the foot and ankle can take many physical forms, from a simple felt pad to a composite brace controlling foot and ankle motions. Orthotics prescribed for lower extremity pathologies include foot orthoses (FOs), ankle-foot orthoses (AFOs), knee orthoses, and knee-ankle-foot orthoses.





Types of Orthoses





  • Various types of orthoses are commonly prescribed for foot and ankle pathologies. The basic subcategories of FOs are prefabricated and custom. There are clear differences between the manufacture and design of orthoses in each category, yet advantages or benefit of one type of device over another has yet to be proven.




    • Prefabricated devices have the distinct benefit of lower cost compared with custom-fabricated foot orthotics. In addition, prefabricated orthoses can be readily stocked for immediate dispensing to the patient. The disadvantage of prefabricated orthotic devices is their difficulty in application to limb and foot shapes that fall outside the “average” range.



    • Custom molding and contouring of an orthotic device to a body segment may be the critical feature necessary for a successful treatment outcome. Yet the mechanism by which foot orthotics actually achieve their treatment effects remains poorly understood, and, thus, claims of superiority of custom vs. prefabricated devices remain speculative.




  • Prefabricated FOs are available for a wide variety of clinical application. In general, these devices are used to offload specific areas of the foot, cushion the foot from impact, support the medial longitudinal arch, and provide mild biomechanical control of hindfoot movements.



  • Custom FOs can be either accommodative or functional.




    • Functional orthoses are most often used with flexible feet, working to alter how foot meets floor.



    • Accommodative orthoses generally are used with more rigid deformities; rather than attempting to alter foot alignment, accommodative orthoses work to relieve pressure under bony prominences.






Prefabricated Foot Orthoses





  • The simplest types of prefabricated FOs are in-shoe pads. Felt forefoot pads are available to relieve metatarsalgia, sesamoiditis, and intractable plantar keratoses. These adjust pressure by offloading adjacent areas and increasing pressure under the pad itself. They are often placed near, but not directly under, the area of pain.



  • Contoured cushioned prefabricated insoles have a wide variety of clinical application for relief of plantar foot pressures, dissipation of impact shock, and enhancement of overall foot comfort. These contoured insoles function as a softer version of a prefabricated arch support.



  • Prefabricated, “biomechanical” semirigid foot orthotics are made from materials commonly used in the fabrication of more expensive custom functional FOs. These devices are contoured to an average shape of a medial and lateral longitudinal arch and generally lack any heel cup. Sometimes, posting is provided in the hindfoot to enhance pronation control.



  • The goal of treatment of these devices is to provide more rigid support and motion control than with softer arch supports.





Custom Foot Orthoses





  • Custom foot orthotic devices require fabrication to some type of model of the patient’s foot. The model on which the orthosis is contoured can be a positive plaster cast, a computer-generated model, or the actual foot of the patient.



  • Equally important to the value of any custom foot orthotic is the selection of material composition, which will be unique to the patient’s clinical condition or biomechanical needs.



  • Accommodative FOs are designed to relieve pressure on certain areas of the foot and to provide support of the foot in its compensated position. The most common use for accommodative foot orthotics is in the management of diabetic foot complications. These devices are also known as total contact orthoses and can disperse plantar pressures to the maximal foot surface area.



  • Functional FOs are designed to control forces that act on the foot during the stance phase of gait. These forces are generally inversion/eversion &/or rotatory forces acting on the subtalar and midtarsal joints.



  • While not part of the definition, functional FOs are often expected to correct alignment of the foot. Yet improvements of alignment with functional FOs are relatively modest, as revealed by numerous kinematic studies of these devices. Kinetic studies of FOs have confirmed that these devices can alter forces or moments acting on the joints of the lower extremity.



  • A predecessor to the functional FO was the University of California Biomechanics Laboratory orthosis (UCBL). This device is still popular today in the treatment of flatfoot conditions. The UCBL is a plastic FO with a deep heel cup and steep medial and lateral flanges. The UCBL is best suited to control transverse plane subluxation of the foot by applying force against the lateral wall of the calcaneus, sustentaculum tali, and lateral aspect of the 5th metatarsal shaft. These devices have fallen out of favor due to difficulty with shoe fit and the need for multiple adjustments for comfort.



  • Functional FOs were developed in the early 1960s. Several principles apply to functional orthotic development. Semirigid to rigid materials are utilized to control significant forces that occur in most foot pathologies. A mold is made of the foot to which posting can be added to address the individual deformity present.





Treatment Effects of Orthotics





  • The majority of studies of treatment effects of FOs have significant deficiencies that must be noted before any conclusions or recommendations can be made. Many studies are simple retrospective “patient satisfaction” surveys, and higher levels of evidence are generally lacking. In most cases, the type of orthosis is not described in detail, and descriptions of the foot types of the subjects are often lacking.



Effects of Foot Orthotics on Plantar Pressures





  • Numerous studies have shown that FOs can significantly reduce vertical force and pressures on various areas of the plantar surface of the foot. Peak pressures can be reduced, at the most, by ~ 20% with an FO. In terms of injury, the significance of this pressure reduction remains speculative.



  • FOs have been shown to decrease plantar callus size in patients with diabetes. Patients with leprosy were noted to have improved healing of plantar ulcers with custom FOs.



  • A semirigid custom foot orthotic was shown to significantly reduce the incidence of femoral and metatarsal stress fractures in military recruits. A prospective 9-week study of military recruits showed that a neoprene insole reduced overuse injuries and tibial stress syndrome from 32% to 23%.



Changes in Foot and Leg Alignment





  • Kinematic studies have primarily focused on the effects of foot orthotics on hindfoot alignment. Most of these studies have been performed on running athletes. These studies have demonstrated relatively modest improvements. Rather than causing noticeable change in foot and leg alignment, FOs may have other effects on kinematics.



  • Semirigid and soft orthotics have shown a significant effect in reducing the velocity of pronation in both running and walking subjects. More recent studies have shown that medially posted custom FOs can reduce the overall range of pronation, maximum angle of calcaneal eversion, and range of internal tibial rotation associated with pronation.



  • The results of kinematic studies have led most researchers to conclude that these devices do not function to realign the skeleton. These devices can, however, significantly alter kinetics of lower extremity segmental function, as documented by many studies on changes in joint moments with orthotic intervention.



Effect of Foot Orthotics on Joint Moments





  • A key area of understanding of orthotic effects on the lower extremity has focused on joint moments. The term moment describes a force couple that acts at a distance from an axis of rotation of a specific joint in the body.



  • Much of the recent insight into the treatment effects of FOs has been obtained by studies of joint kinetics. Reduced strain of specific anatomical structures (internal joint moments) has been measured with certain orthotic conditions, and this information can be helpful in designing treatment strategies.



  • Wedging of shoe inserts can affect knee joint moments. External varus knee joint moments were reduced by lateral wedged shoe inserts. Also, medial compartment knee joint load was estimated to be reduced with the lateral wedged inserts. Medial arch support shoe inserts were shown to reduce lateral patellofemoral joint load during running gait. However, some studies have shown that the responses of human subjects to various types of wedging of shoe inserts are subject specific and unsystematic.



  • In summary, nearly any type of shoe insert modification that applies medial wedging to the hindfoot or molding of the device to the medial arch will significantly reduce hindfoot inversion moment during the early phase of running gait. This would indicate a reduced strain of the ankle “invertors,” such as the tibialis posterior muscle, and passive structures of the medial ankle, such as the deltoid ligament.



Treatment Effects of Foot Orthoses for Specific Injuries: Heel Pain Syndrome





  • Subcalcaneal pain syndrome has been extensively studied in terms of response to treatment with various forms of FOs. Retrospective studies of large groups of patients receiving semirigid and rigid custom FOs report significant improvement of symptoms and high patient satisfaction.



  • A well-designed prospective study showed that early-onset heel pain responded best to a program of stretching combined with a prefabricated heel pad or arch support, compared with stretching combined with use of a custom semirigid functional FO.



  • However, several retrospective studies of large groups of patients with plantar heel pain have shown disappointing results with the same viscoelastic heel pad used in the aforementioned prospective study.



  • A prospective, randomized study compared the results of 3 types of treatment for long-term, chronic plantar heel pain: Corticosteroid injection and nonsteroidal antiinflammatory drug, viscoelastic heel cup, and functional FOs. A larger number of patients obtained good to excellent results in the custom foot orthotic group compared with the other groups.



Treatment Effects of Foot Orthoses for Specific Injuries: Patellofemoral Pain Syndrome





  • Foot orthotics have been reported to be very successful in the treatment of patellofemoral pain syndrome with a success rate between 70-80%. However, most of these studies were not randomized controlled trials, and other adjunctive treatments were utilized.



  • Two randomized, controlled studies have shown that an exercise program combined with “soft” orthotics can significantly decrease patellofemoral pain syndrome.



Treatment Effects of Foot Orthoses for Specific Injuries: Balance and Postural Control





  • The most consistent objective measure of foot orthotic treatment effects have been found in studies of balance and postural control.



  • At least 4 different studies have shown significant improvement in balance control in patients with chronic ankle instability when FOs are utilized. Custom-molded foot orthotics have been shown to reduce postural sway in patients after acute ankle sprain and have been shown to reduce pain while running in these patients.



  • Custom-molded FOs appear to reduce postural sway better than flat orthoses. Posting of orthoses appears to also enhance postural control, particularly when medial posting is applied or when pronation of the subtalar joint is controlled.


Only gold members can continue reading. Log In or Register to continue

Oct 29, 2019 | Posted by in ORTHOPEDIC | Comments Off on Orthotics and Prosthetics
Premium Wordpress Themes by UFO Themes