A Guide To Pathology Specific Orthoses For RA

By Cherri S. Choate, DPM

As the population ages, the impact of chronic disease is challenging the world of medicine. Rheumatoid arthritis (RA) is a chronic disease that affects more than 2.1 million Americans and, unlike osteoarthritis, the impact of RA typically starts much earlier in life.1 There is a wide range of pathology in the musculoskeletal system that may occur as RA progresses and in more advanced disease, more than 85 percent of patients have foot involvement.2 As RA progresses or in severe cases, deformity occurs earlier and patients struggle with disabling pain and functional limitation. Recently, a group of medical experts acknowledged the need for evaluation and treatment of foot problems in RA, and established clinical practice guidelines for the non-pharmacological treatment of RA. The group reviewed 565 publications and used 198 of these publications in the final analysis. The multispecialty panel established five recommendations, one of which addressed foot problems in RA. The panel suggested that “… in patients with early RA, metatarsal pain and/or foot alignment abnormalities should be looked at regularly, and appropriate insoles should be prescribed if needed.”3 Since clinical studies have shown that the foot is the initial site of involvement in up to 36 percent of patients with RA, effective orthotic intervention many help alleviate some of the foot pain and functional limitation that plagues patients with RA. However, it is prudent that we first determine the lower extremity problems specific to RA and assess the available research findings in order to apply appropriate and successful orthotic therapy. Understanding The Lower Extremity Pathology Of RA Lower extremity pathology RA is complex. Too often, the patients are pigeonholed with the diagnosis of metatarsalgia and clinicians see them routinely for radiographs to see how the metatarsalgia has progressed. We are continuing to learn more about the relationship of joint inflammation, joint destruction, gait changes and lifestyle modification in patients as their RA progresses. It is becoming more important to recognize the mechanical etiology of the symptoms and treat them accordingly. Current technology has allowed researchers to study gait mechanics, pressure, loading rates and resultant pain/disability more objectively. In regard to recent clinical studies that reveal the complex mechanics of RA, a 1979 study by Sharma compared the peak forces under the metatarsal heads of patients with and without RA. The results showed that patients with RA exerted considerably less force under the toes and first metatarsal head, and more force under the third, fourth and fifth metatarsal heads.4 These findings are certainly consistent with the common diagnosis of metatarsalgia. Another group headed by Hass published a paper in 1999 that evaluated the progression on plain radiographs of the typical joint pathologies of RA: rearfoot valgus, flattening of the arch, splayfoot and lesser digit deformities. Fifty-seven patients participated with an average duration of disease of 19.2 years. The five-year study found that the most frequent joint to change, for 57 percent of the patients, was the first metatarsophalangeal joint (MPJ). Overall, 97 percent of patients had a radiological progression of arthritic changes.5 In 2000, Sokka evaluated the difference between radiological changes and patient symptoms. In the group of 141 patients, with an average duration of disease of 11.8 years, functional capacity scores correlated at higher levels with pain scores than with radiographic scores of the small joints.6 What The Studies Reveal About The Impact Of RA On Gait Beyond radiographic findings alone, a 2004 study by Tuna, et. al., focused on the plantar pressure alterations in RA. Using pedobarography, the group assessed radiographic joint erosions in 50 patients with RA and 50 without RA. Most dynamic pedobarographic parameters were significantly different between the two groups. Researchers found higher static pressure and contact areas in the forefoot among the patients with RA. Patients with higher erosion scores also had higher static and dynamic peak pressure values.7 This study suggests that joint erosion may lead to gait changes (increased pressures during dynamic studies) due to pain and deformity. Woodburn published a 2004 study that was even more gait specific and addressed specific joint motion in patients with RA.8 The study evaluated 11 people with RA and five without RA using a six-camera, video-based motion analysis system. In comparison to the healthy people in the study, the RA patients had reduced range of motion across all segments and in all planes of motion. During gait, the RA patients, on average, had more eversion motion of the rearfoot, reduced forefoot motion in all planes, lower navicular height during contact phase and less extension of the hallux during propulsion. To date, this is the only multi-segmental foot motion study focused on patients with RA. The results reveal the presence of abnormal motion at multiple joint segments, the frequency of rearfoot instability, the abnormally lowered position of the navicular (arch height) and the abnormal motion at the first metatarsophalangeal joint.8 In 2006, a study by Bal and colleagues focused on determining the frequency of specific foot deformities and their relationship to the foot function index (FFI). They performed clinical and radiographic assessments of 78 patients with RA. Pes planus was the most frequent deformity they found on radiograph. Researchers found pes planus in 80.8 percent of the patients. The two most common deformities to increase with disease duration were hallux rigidus and clawtoe. The presence of hallux ridigus and calcaneal valgus had the most impact on FFI. In this study, certain foot deformities had a greater effect on the patient’s functional ability. The authors of the study suggested that one should consider orthoses when foot pathology or disability is present in patients with RA.9 A group led by Laroche conducted another study evaluating gait. Their goal was to evaluate the loss of metatarsophalangeal joint range of motion on the kinematics of gait. By using a video-based gait evaluation system, the researchers found a slower walking velocity and shorter stride length among the patients with RA. The data also showed a strong negative relationship between the maximal flexion of the knees and hips during walking and underlying dorsal flexion range of motion of the MPJ. Perhaps this suggests an impact on kinematics at a higher level when there is deformity in the foot.10 In 2006, Turner, et. al., surveyed 12 female patients who had RA for less than two years and all had foot pain. Researchers utilized 3-D gait analysis to measure foot function. Even though the patients were in the early stages of RA, researchers found a number of gait abnormalities including increased double-support phase, lower medial arch height, greater peak eversion during stance, reduced lesser toe contact, elevated forefoot pressure and a larger midfoot contact area.11 Given this information from the medical literature, perhaps we can now treat the patient with RA more objectively, earlier in the disease process and provide treatment that is more specific to their pathology. Assessing The Literature On Orthotic Use In Managing RA The previous research studies have proven that foot pain, functional limitation, foot deformity and gait abnormalities occur in patients with RA, even those in the early stages of the disease.12 As practitioners, we have often treated these patients, at all stages, with typical plastazote insoles with a metatarsal pad and rocker shoes. Does recent clinical evidence support this or is there more we can do for these patients? Accordingly, let us take a closer look at conclusions from studies that evaluated orthotic use in patients with RA. Hodge, et. al., attempted to determine if prefab orthotics, custom orthotics with a metatarsal pad or custom orthotics with a metatarsal bar relieved more pain under the second metatarsophalangeal joint. The study concluded that a semi-rigid device with a metatarsal pad (dome) was most effective for decreasing pain and pressure.13 Li and colleagues studied the impact of using custom orthotics in patients with RA versus healthy patients. Researchers concluded that a custom multilayer polyethylene foam device with a metatarsal pad produced more pressure relief, lowered loading forces and increased weight distribution.14 Chalmers and colleagues compared the effect of semi-rigid orthotics, soft orthotics and shoes alone when it comes to relieving metatarsal pain among patients with RA. Semi-rigid orthotics worn in supportive shoes were much more effective than soft orthotics or shoes alone at relieving metatarsal pain, according to the study.15 Woodburn, et. al., sought to determine the effect of early intervention with a semi-rigid orthotic in addressing painful rearfoot valgus among patients with RA. The study found that using custom semi-rigid orthoses over 30 months decreased foot pain, foot disability and functional limitation.16 Magalhaes and colleagues studied the effect on the functional foot index when they employed a custom EVA device with accommodations. They found that orthotic use significantly reduced pain, disability and activity limitation.17 Woodburn and colleagues also looked at ankle and STJ motion among patients with RA to determine if semi-rigid graphite orthotics can effectively control the abnormal eversion of STJ and improve rearfoot instability. The study found that patients maintained abnormal eversion and then improved.18 Powell, et. al., studied the effect of a custom-semi-rigid device, an OTC device and shoes alone on improving function and reducing pain among patients with juvenile RA. They found that custom semi-rigid devices were the most effective in facilitating pain relief and speed of ambulation.19 The aforementioned studies show that medical research has reached far beyond the expected metatarsal pad on a soft insole when it comes to managing RA pain in the lower extremity. The studies addressed pressure peaks, loading forces, materials, gait parameters, pain and the functional foot index. After evaluating these studies, it is imperative that we reevaluate our habits regarding orthotics for the patient with RA.20 Key Insights On Orthotic Solutions For Common RA-Related Problems Now that we have all this documentation about the effectiveness of orthoses in managing RA in the lower extremity, how do we apply this knowledge on a day-to-day basis in our office and clinics? First of all, we should establish goals for treatment based on the information regarding RA pathology. By creating a list of typical biomechanical problems, we can subsequently determine options within an orthotic prescription that would address each problem. Rearfoot instability. By increasing rearfoot stability of the ankle and subtalar joint, the patient will have more stability in all joints distal to the rearfoot. There are a variety of choices when it comes to using orthotics to achieve this goal. One may opt for a semi-rigid plate with a flat rearfoot post. A more advanced but very effective technique is to order an intrinsic addition of the Kirby skive within the heel cup. In theory, the Kirby skive (2 mm to 6 mm) “flattens” the medial internal heel cup, thereby increasing the force of the supinatory moment arm and resisting pronation of the rearfoot.21Midfoot collapse. Midfoot collapse, which has been documented in the studies as a lower position of the navicular during stance, is often overlooked in the treatment of the rheumatoid foot.8 The navicular prominence can become very painful and lead to an antalgic gait pattern. By using a semi-rigid plate with a navicular sweet spot, one can achieve both control and cushioning simultaneously. Limited first MPJ motion. Although the lesser metatarsals have often received the majority of attention in the foot with RA, multiple studies have shown the increased erosion and decreased motion of the first MPJ over the course of the disease.5,8,9 Utilizing a reverse Morton’s extension earlier in the disease process will increase the available motion in this joint. In later, more painful stages of limited motion, a Morton’s extension will help decrease pain during propulsion. Lesser metatarsalgia. Many of the studies on orthotic therapy were focused on pain in the lesser metatarsal heads. One study found that the metatarsal pad was superior to the metatarsal bar in facilitating pain and pressure relief.12 Although both of these techniques are appropriate, clinicians may need to focus more attention on the construction of the plate itself. If the plate contours more of the surface area of the plantar foot via minimal arch cast correction, then the lesser metatarsal heads will bear less weight. High peak pressures in stance. Only the most recent studies are beginning to reveal gait patterns in patients with RA. Painful joints will lead to antalgic gait and eventually an imbalance in muscle use during each gait cycle. Redistribution of weight via arch contact and appropriate shock-absorbing top covers and extensions should help decrease peak pressures and equalize loading forces. Abnormal propulsion. Destruction of joint surfaces begins with chronic synovitis and affects many segments involved in the lower extremity gait.8 Future studies are likely to shed more light on the exact steps that lead to limited motion of the MPJs and the resultant poor propulsive power as the disease progresses. A small heel lift should extrinsically increase the propulsion and, in concert with pain relief in the metatarsal heads, gait should improve. In Conclusion Just as in any chronic disease, individuals cannot escape the inevitable deterioration of disease specific body systems. Studies have shown that plantar pressures are significantly different in patients with RA, even in early stages. It is likely that joint erosions lead to gait patterns that are specific for patients with RA. Leading researchers have established that there are multisegment changes of joint motion in the foot and ankle. These limitations in motion lead to deformities such as calcaneal valgus, lowered arch height and hallux limitus. In turn, these deformities lead to increased pain, functional limitation and a decreased quality of life. Multiple research groups have studied orthotic intervention at a variety of levels within this lower extremity cascade of events associated with RA. Use of the metatarsal pad was the most effective accommodation to decrease pain and gait limitation in the forefoot. What may have been surprising was the overall success of the semi-rigid device. After recognizing the impact of motion changes in the rearfoot and midfoot, it certainly makes sense that a semi-rigid device would impact the motion of the foot in gait better than the soft device that clinicians have used so predominately in the past. As a well-informed clinician, you can combine your clinical experience with the findings of global research teams to create orthotic therapy that can decrease pain and improve daily function in the lives of patients with RA. The medical profession often looks to podiatry to solve the foot problems of patients with rheumatoid arthritis. It is our obligation to know the literature and be able to apply it effectively to facilitate optimal outcomes in this patient population. Dr. Choate is an Adjunct Assistant Professor in the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt College. She is a consultant for ProLab/USA and is in private practice in Berkeley, Calif. For related artricles, see “Lower Extremity RA: Can Orthoses Have An Impact?” in the February 2006 issue of Podiatry Today or “Treating Severe Deformity In Young Patients With Rheumatoid Arthritis” in the September 2003 issue. Also check out the archives at www.podiatrytoday.com.



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