Background The majority of rheumatoid arthritis (RA) patients develop symptoms related to their foot or ankle.1 Extraarticular manifestations occur in 10–20% of patients. Symptoms of neuropathy may be overlooked or overestimated in case of severe joint disease, restriction, pain and deformities.2
Objectives This study aimed to evaluate neuropathic foot and ankle pain in RA patients using electrophysiology and musculoskeletal ultrasound (MSUS) to address the association between these findings and disease activity.
Methods Fifty patients fulfilling the 2010 ACR/EULAR classification criteria and having neuropathic foot and/or ankle pain, were recruited. According to DAS28 system, patients were divided into two equal groups (25 patients each); active and remission. Twenty five healthy subjects were included as controls. Routine tibial and peroneal nerve conduction studies, as well as electromyography of tibialis anterior and abductor hallucis muscles, were performed.3,4 MSUS assessment of the ankle joint and extra-articular portion of the foot was also performed.5
Results Thirty nine (78%) patients showed the electrophysiological findings of foot neuropathy, irrespective of the disease activity level. In total, 48% of the patients had demyelinating mononeuropathies (entrapment neuropathies), whereas the other 30% had symmetrical axonal neuropathies (Table 1).
Ultrasound diagnosis of posterior tibial entrapment at the ankle was encountered in 20 (40%) patients. In addition, a positive power Doppler (PD) signal and erosions of the ankle joint were prevalent among the active group in comparison with patients in remission (p≤0.001), as shown in figure (1).
Conclusions Peripheral nerve affection is common in the rheumatoid foot, irrespective of the disease activity level. The most common foot neuropathies are; posterior tibial entrapment at the ankle, peroneal entrapment at the fibular neck and pure sensory axonal neuropathy. MSUS is valuable for diagnosis of posterior tibial entrapment at the ankle. In addition, a positive PD signal and erosions of the ankle joint are associated with disease activity.
Loveday DT, Jackson GE, Geary NP. The rheumatoid foot and ankle:current evidence. Foot Ankle Surg 2012; 18:94–102.
Ibrahim I, Medani S, El-Hameed M, Imam M, Shaaban M. Tarsal tunnel syndrome in patients with rheumatoid arthritis, electrophysiological and ultrasound study. Alexandria J Med 2013; 49:95–104.
Preston D, Shapiro B. Routine lower extremity nerve conduction. In:Preston D, Shapiro B, editors. Electromyography and neuromuscular disorders. 3rd ed. Philadelphia: Elsevier; 2013.115–124.
Preston D, Shapiro B. Anatomy for needle electromyography. In:Preston D, Shapiro B, editors. Electromyography and neuromuscular disorders. 3rd ed. Philadelphia: Elsevier; 2013. 174–190.
Riente L, Delle Sedie A, Iagnocco A, Filippucci E, Meenagh G, Valesini G et al. Ultrasound imaging for the rheumatologist V. ultrasonography of the ankle and foot. Clin Exp Rheumatol 2006; 24:493–498.
Disclosure of Interest None declared