Long term effects of intra-articular botulinum toxin a for refractory joint pain

Abstract

The purpose of this case series review is to describe our 12 month clinical experience with intra-articular injections of Botulinum toxin Type A (BoNT/A) for refractory joint pain. Eleven patients with chronic arthritis who had failed treatment with oral and/or intra-articular medications and were not surgical candidates were referred to us for management of moderate to severe refractory joint pain in 15 joints. The use of BoNT/A to treat joint pain is a non-FDA approved "off label" treatment with potential side effects. After a detailed explanation of the joint injection procedure, signed informed consent was obtained for the procedure. Fifteen joints were injected with BoNT/A (Allergan, Inc): six lower extremity joints (3 knees, 3 ankles) with 25-50 units and nine shoulders with 50-100 units. Patients were followed for one year or longer. Maximum relief of pain was measured by comparing baseline pain on a numeric rating scale (0-10) to pain at the time of maximum relief (paired t-test). Maximum improvement in function was assessed using paired t-tests for improvement in active flexion and abduction for the shoulder joint, and by the time to perform sit to stand ten times (the timed stands test, TST) for the lower extremity joints. Two patients were female and nine were male, aged 42-82 years. Five had osteoarthritis (OA), five had rheumatoid arthritis (RA) and one had psoriatic arthritis. All patients were on analgesic and/or anti-inflammatory medications and all joints had previous intra-articular steroid or viscosupplement injections with inadequate or unsatisfactory benefit. A clinically and statistically significant improvement was noted after IA-BoNT/A injections. The mean maximum decrease in lower extremity joint pain was 55% (p =0.02) and the 36% (p =0.044) improvement in the Timed Stands Test was noted at four to ten weeks after injection. There was a 71% mean maximum reduction in shoulder pain severity from 8.2 +/- 1.1 to 2.4 +/- 1.9 (p <0.001). Active range of motion increased 67% in flexion (from 67.8 +/- 27.6 to 113.3 +/- 46.6 degrees, p =0.001) and 42% in abduction (from 50 +/- 18.5 degrees to 71.1 +/- 23.1 degrees p =0.01). No immediate or delayed adverse effects related to BoNT/A were noted after the injection. Duration of pain relief was variable and ranged from 3 to 12 months. Five joints were re-injected with IA-Bont/A and had a similar decrease in joint pain that lasted 3 to 12 months. This is the first report of the long term effects of intra-articular BoNT/A injections to treat chronic joint pain and the efficacy of repeated injections. Although this study was small, and uncontrolled the results suggest that IA-BoNT/A injections are an effective and safe treatment for chronic joint pain disorders.