Benign Evolution of Complex Regional Pain Syndrome (CRPS) Type 1 in Patients Treated with Intravenous Neridronate: A Single-Center Real-Life Experience.

Objective: To investigate the long-term effects of intravenous neridronate treatment in patients with complex regional pain syndrome type 1 (CRPS) in a real-life setting.

Methods: We conducted a retrospective study on consecutive CRPS patients treated at our hospital from February 2018 to July 2023. All were treated within three months of the onset of CRPS symptoms. The Patient-Reported Outcomes Measurement Information System 29-Item Health Profile (PROMIS-29) version 2.1 was administered. The main outcome of interest was the evolution of the PROMIS-29 scores from baseline to the last follow-up visit. Patients were categorized as "complete responders" or "non-complete responders". The association of clinical and demographic variables with a complete response was analyzed using chi-square tests and univariate logistic regression.

Results: Thirty-six patients were included, with a median follow-up time of 4.8 years. A significant improvement was noted in the mean numerical pain rating scale (from 6.4 ± 1.9 to 3.1 ± 2.4, p < 0.001), as well as across all PROMIS-29 domains. Physical function improved from 34.2 ± 4.9 to 49.2 ± 9.9, p < 0.001; anxiety from 58.0 ± 6.7 to 49.6 ± 6.9, p < 0.001; depression from 55.3 ± 6.3 to 47.7 ± 6.6, p < 0.001; fatigue from 55.7 ± 7.7 to 50.9 ± 8.7, p < 0.001; sleep disturbance from 53.8 ± 6.8 to 51.3 ± 6.6, p = 0.034; social roles and activities from 41.8 ± 5.2 to 51.8 ± 8.9, p < 0.001; and pain interference from 64.1 ± 5.9 to 52.4 ± 9.9, p < 0.001. The likelihood of achieving a complete response was associated with the male sex, foot or ankle injuries (compared to hand and wrist injuries), and a younger age. No association was found with the type of inciting event or with the body mass index.

Conclusions: Our real-life data indicate that early treatment with neridronate leads to substantial benefits in patients affected by CRPS type 1. The strongest responses are seen in young patients, males, and those with lower limb involvement.