Ensuring Orthotic Efficacy For Adults And Children
In addition to sharing their perspectives on rearfoot posting, these expert panelists discuss their approaches to assessing the effectiveness of their orthotic prescriptions and when it is time to replace orthoses.
How do you determine the type and amount of rearfoot posting you prescribe?
Russell Volpe, DPM, prefers extrinsic rearfoot posting. He says it provides stability to the device along with the desired frontal plane correction. Dr. Volpe only switches to intrinsic rearfoot posting if there is a low volume in the counter of the intended shoe.
“By using intrinsic rearfoot posting, you reduce the bulk of the device in the shoe but you do sacrifice some of the stabilizing effect of the post,” says Dr. Volpe.
Dr. Volpe has several ways to determine the amount of rearfoot posting on a device. Most commonly, he works from the degree of rearfoot (subtalar and tibial) varus he identifies during the biomechanical exam. Typically, Dr. Volpe says half the measured deformity is a good starting point to determine the amount of posting. He often increases that amount in pediatric flatfeet and in lax foot types.
Most of the time, Ronald Valmassy, DPM, attempts to provide an inversion or supinating force to the orthotic device. Using the Root technique, he will typically invert the device anywhere from a vertical position to 5 to 10 degrees of inversion, depending on the degree of calcaneal eversion in the resting calcaneal stance position (RCSP). For example, if the patient is 5 degrees everted, Dr. Valmassy will normally invert the device by approximately 8 to 10 degrees. If he is utilizing the Blake inverted casting technique, he will typically multiply the degree of eversion by five.
In addition, Dr. Valmassy customarily adds a medial calcaneal Kirby skive in lengths from 2 to 6 mm. If the heel is everted 1 or 2 degrees, he uses a 2 mm skive and for a heel everted up to 5 degrees, he typically utilizes a 4 mm skive. Dr. Valmassy notes that anything beyond 5 to 6 degrees of eversion will typically require a 6 mm medial skive.
If the patient is supinated and everted in RCSP due to a forefoot valgus deformity and exhibits marked lateral instability, Dr. Valmassy will balance the rearfoot to a perpendicular position and typically adds a 2 mm, 4 mm or 6 mm lateral calcaneal skive. For patients who are laterally unstable but maximally pronated and still inverted, he will attempt to iatrogenically introduce a forefoot valgus correction into the casts while taking a neutral position cast.
Similarly, Dr. Volpe sometimes uses a tissue stress model and prescribes medial skive modifications to the heel cup to shift the orthotic reaction force more medially on the subtalar joint. He notes this results in applying a greater supinatory moment to the subtalar joint. Sometimes, Dr. Volpe combines these two techniques for added effect. He also makes adjustments to the post for different clinical scenarios such as extending the post medially, omitting undercut (medial or lateral) and grinding the post into the shell for bulk reduction.
As Paul Jordan, DPM, notes, a separate rearfoot post is rarely required for young children. He suggests considering the consistency of mature heel contact as well since the ability to achieve a consistent heel contact with weight acceptance is not evident until ages 6 to 8.
In children ages 6 to 8, Dr. Jordan says there may be sufficient frontal plane malalignment of the lower limb-rearfoot complex to initiate an excessive and prolonged pronatory moment from initial heel contact to midstance. For these children, he says the degree of rearfoot posting should be the amount required to retain the subtalar joint around its age-appropriate neutral position.
Dr. Jordan has had excellent outcomes by assessing the total varus of the lower limb and foot, and providing the total posting needed to align the lower limb above the weightbearing foot. He notes medium density post material, which may be incorporated as a filler beneath a thin thermoplastic shell, is more resistant to pathological compensation than acrylic while being forgiving where mobility is desirable.
Some practitioners develop consistently high successful outcomes with a particular type of orthosis. Is there a “signature” device you frequently prescribe that yields these type of results?
Most often, Dr. Valmassy will prescribe a device fabricated of polypropylene 3/16 inches thick. In stylish shoes, he will utilize a more flexible device such as a 1/8-inch polypropylene orthosis although he notes a more rigid device is appropriate in most instances. Often Dr. Valmassy will invert the rearfoot anywhere from 5 to 8 degrees and utilize a medial calcaneal skive from 2 to 6 degrees. The heel cup will typically be 16 mm, which he often increases to 18 or 20 mm depending on the severity of the problem. Dr. Valmassy frequently considers a 10 to 12 mm heel cup in cases of minimal correction or for a forefoot valgus deformity.
Dr. Valmassy’s signature devices have a flat rearfoot post with no motion. However, if he is trying to reduce shear forces at heel contact and strike, he will utilize a 4-degree post with 4 degrees of motion for a retrocalcaneal exostosis or a retrocalcaneal bursitis.
Noting the multifaceted aspects of growing and developmentally changing children, Dr. Jordan does not have a signature orthosis design, style or material.
“Using such an orthosis would suggest that all kids are essentially the same and their biomechanical issues are very similar in their daily routine of play. They are not,” he says.
Similarly, Dr. Volpe does not have a signature orthosis, noting “the beauty of custom foot orthoses is that they can be tailored exactly to the clinical circumstances of a particular patient.” However, he does like the Dynamic Stabilizing Innersole System (DSIS) and University of California Biomechanics Lab (UCBL) type devices — which have high flanges and deep heel seats — in toddlers and young children with lax body types and high-motion flat feet. Dr. Volpe also uses gait plate extensions frequently to manage the in-toe component that frequently accompanies a pediatric flatfoot.
Dr. Jordan notes that most often, the orthoses in a pediatric practice should address the lateral column along the lateral-plantar aspect of the shell. As he says, one cannot expect a deep heel cup to “control” the calcaneus. Dr. Jordan notes the interface between the plantar fat pad and calcaneus has joint-like qualities where motion will occur regardless of how deeply and tightly the fat pad is squeezed.
“An orthosis design must be individualized with specificity to the primary problem, age group, developmental status and pathomechanics involved,” maintains Dr. Jordan. “An orthosis must be designed to fit the child’s needs rather than demand that the child fit an orthosis that the practitioner feels most comfortable prescribing.”
What is your protocol for assessing orthotic effectiveness?
When assessing the orthosis, Dr. Volpe asks patients how they feel in the device and how any particular complaints respond to the device. Likewise, at the follow-up visit, Dr. Valmassy questions patients on what effect the orthotic devices had on their symptoms.
Dr. Volpe also looks at patients weightbearing without their orthoses and then with their orthoses, and takes measurements to determine the degree of control in the devices. Dr. Volpe retakes those measurements later on to see if some of the control has been “lost.”
In contrast, Dr. Jordan says it is inappropriate simply to have the child stand barefoot and then stand on the orthoses to attempt comparative RCSP. He says one should view the hip-knee-ankle-foot alignment as an expression of how well the orthosis reduces undesired compensation. Whether the pediatric patient is symptomatic with night pains, muscle spasms, dynamic toe walking or has a clinical appearance of “flat feet,” Dr. Jordan says an altered alignment of the hip-knee-foot functional coupling may be a significant reflection of the devices’ efficacy. He cites the example of positive change of the “Q-angle” in athletes as well as in children.
Dr. Valmassy asks patients to bring the shoes they have worn three to four times with the orthotic device in place from the time of dispensing to the time of the two-week follow-up visit. He will evaluate the patient with and without the device in place to determine if the patient is achieving the anticipated result. Dr. Valmassy also looks for reduction of both abnormal pronation and abnormal supination. Finally, he assesses the patient’s overall stature and posture, noting that a functional foot orthosis would generally improve overall posture.
Using digital camera technology and common software, Dr. Jordan says one can embed printed images into the child’s medical report for immediate and later comparison following skeletal growth. He immediately shows comparisons to parents and integrates them in a report to the pediatrician. When Dr. Jordan needs to observe reduced compensations in the more mature, walking child, he uses pocket digital video cameras. Similarly, computer aided objective gait analysis is also very effective at documenting changes in foot function after prescribing an orthosis, notes Dr. Volpe.
Furthermore, Dr. Valmassy assesses the distal margin of the orthotic device. If there is a significant impression in the inner sole of the shoe along the distal medial margin of the orthotic device, he suspects the device is not controlling patients well and they are pronating through the device. Dr. Valmassy assesses the effect of the softness or firmness of the inner sole. If the device does not seem to be controlling the patient well, he will typically add a forefoot varus post to increase the surface area supination.
How do you determine when you need to replace an orthotic?
Replacement of the orthoses may be essential, notes Dr. Jordan, due to outgrowth where the plantar contours no longer match the contours of the child’s own foot. He notes a change in width at the navicular or base of the fifth metatarsal requires modification or adjustment, not replacement. One should assess the youngster every six to eight months regardless of the rate of skeletal growth, suggests Dr. Jordan. Even without significant growth of the foot, he says one generally needs to modify the plantar posting in association with the soft tissue and skeletal changes of a growing, maturing child.
In regard to the pediatric patient, Dr. Valmassy informs the patient’s parents that he typically will replace the device every two to three years or every two to three shoe size changes. He notes the orthotic device is normally effective up to the point where it reaches the midshaft portion of the metatarsal. When the device becomes uncomfortable or blisters occur or where hyperkeratotic areas become more pronounced, he advises replacing the orthotic device.
Dr. Volpe determines replacement by how the device fits. In a growing child, he says one will have to replace the device once it is too small. Dr. Volpe sees all his orthosis patients at maximum intervals of six months to make that assessment. In adults, he notes signs of wear on the device will lead to recommendations for refurbishment or replacement.
If measurements indicate a loss of effectiveness of the device, Dr. Volpe will also recommend either a retooling or a new device. Finally, he says signs that indicate replacement include shell fatigue and any return of symptoms that were previously managed successfully with the device.
Dr. Valmassy normally does not replace the polypropylene device. He notes that a polypropylene rearfoot post typically assists in the longevity of the orthosis. With a softer type or rearfoot post such as cork or EVA, which introduces some heel contact shock absorption, Dr. Valmassy finds that the posts have to be replaced approximately every five years. With a composite orthosis such as a sports device, which is fabricated of polypropylene, Spenco and EVA, he notes it is not uncommon for these devices to compress over a period of from one to three years. At this point, they usually require replacement, according to Dr. Valmassy. When a patient’s symptoms return or increase, he will often consider recasting the patient for a more aggressive type of orthotic device.
“Now that I have been in practice for over three decades, I still see patients that have devices that I prescribed 25 years ago or more, and the devices still contour well with the patient’s foot,” says Dr. Valmassy.
Dr. Jordan is a Past Associate Professor in the Department of Orthopedics and Pediatrics at the New York College of Podiatric Medicine in New York City. He is a Diplomate of the American Academy of Cerebral Palsy and Developmental Medicine, and a Diplomate of the American Board of Podiatric Orthopedics and Primary Podiatric Medicine. Dr. Jordan is in private practice in Smithtown, N.Y.
Dr. Valmassy is a Past Professor and Past Chairman of the Department of Podiatric Biomechanics at the California College of Podiatric Medicine. He is a staff podiatrist at the Center for Sports Medicine at St. Francis Memorial Hospital in San Francisco.
Dr. Volpe is a Professor in the Department of Orthopedics and Pediatrics at the New York College of Podiatric Medicine in New York City. He is in private practice in New York City and Farmingdale, N.Y.
Dr. D’Amico is a Professor and Past Chairman in the Division of Orthopedics at the New York College of Podiatric Medicine. He is a Diplomate of the American Board of Podiatric Orthopedics and Primary Podiatric Medicine, and a Fellow of the American Academy of Foot and Ankle Pediatrics. Dr. D’Amico is in private practice in New York City.