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.

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