Background Complex Regional Pain Syndrome type I (CRPS-I) is a painful condition which can lead to potential disability. The efficacy of Bisphosphonates (BPS) treatment in this syndrome has been demonstrated in trials in which different types and dosages of BPS were investigated1,2.
Objectives Aim of the study was to identify variables predictive of a clinical response to BPS treatment in a large cohort of subjects with CRPS-I.
Methods A retrospective analysis of patients with CRPS-I referred to our Unit in the last 5 years for a treatment with intravenous BPS (Neridronate 100 mg for 4 infusions, Pamidronate 60 mg for 4 infusions or Clodronate 300 mg for 10 infusions) was performed. Patients with a clinical diagnosis of CRPS-I according to Budapest criteria3 were included when follow up data were available. Baseline variables (demographic characteristics, CRPS-I site, predisposing event, duration of symptoms before BPS treatment, type of BPS used, associated clinical manifestations, imaging) and outcome measures (pain values) were collected. A clinical response to the treatment was defined as a reduction in pain on a Visuo-Analogic Scale (VAS) higher than 50% compared to baseline at 45-60 days from the beginning of the treatment4.
Results A total of 172 patients were included in the study, with a mean (SD) age of 56.7 (13.8) years. Among them, 116 (67.4%) were treated with Neridronate, 47 (27.3%) with Pamidronate and 9 (5.2%) with Clodronate. A clinical response to the treatment was observed in 123 (71.5%) patients. Subjects responding to the treatment had a shorter duration of symptoms [median (IQR): 3 (2,5) vs 5 (2,7); p=0.000] and showed more frequently inflammatory signs (92.7% vs 69.8%; p=0.000). A fracture as predisposing event was more likely to be found in responders (53.7% vs 30.6%, p=0.006). The treatment with amino-BPS was associated with a higher frequency of response than Clodronate treatment (73% vs 44.4%; p=0.065). At multivariate analysis a “warm” inflammatory phase of the disease [OR (95%CI): 4.57 (1.59, 13.15)] and a fracture as predisposing event [OR (95%CI): 3 (1.20, 7.52)] were associated with increased odds of response to the treatment.
Conclusions The treatment of CRPS-I with intravenous BPS is more likely to be effective when established in an early “warm” phase of the disease. Subjects with a previous fracture may represent a subset of patients with a higher chance to benefit from BPS treatment.
Brunner F, Schmid A, Kissling R, Held U, Bachmann LM. Biphosphonates for the therapy of complex regional pain syndrome I - systematic review. Eur J Pain. 2009;13:17-21.
Varenna M, Adami S, Rossini M, Gatti D, Idolazzi L, Zucchi F, Malavolta N, Sinigaglia L. Treatment of complex regional pain syndrome type I with neridronate: a randomized, double-blind, placebo-controlled study. Rheumatology 2013;52:534-42.
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Forouzanfar T, Weber WE, Kemler M, van Kleef M.What is a meaningful pain reduction in patients with complex regional pain syndrome type 1? Clin J Pain 2003;19:281-5.
Disclosure of Interest None declared
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