Peripheral Nerve Injections for the Treatment of Upper Extremity Complex Regional Pain Syndrome: A Feasibility Study for a Proposed Randomized Design

Background Complex regional pain syndrome (CRPS) is characterized by intense pain, loss of function, and associated with motor, trophic, sudomotor, and/or vasomotor changes of the affected extremity. Upper extremity CRPS is seen frequently in electrodiagnostic, neurology, and musculoskeletal clinics and occurs in up to one-third of patients who have undergone common surgical procedures (i.e. carpal tunnel surgery). To date, there is a limited understanding of the underlying pathophysiology of CRPS. As a consequence, few effective treatment options are available.

Peripheral nerve blocks have proven to be successful in reducing pain for several musculoskeletal and neurologic conditions. Similarly, this procedure could be used to block somatic and autonomic sensory fibers which are thought to contribute to CRPS. In a small exploratory study, investigators found peripheral nerve blocks in the upper extremity (suprascapular and median nerves) were well-tolerated in patients with CRPS and resulted in a 56% and 37% pain reduction in the shoulder and hand 2 weeks after injection, respectively. While this is highly encouraging, large randomized placebo-controlled trials (RCTs) are necessary to demonstrate effectiveness and safety of nerve blocks for this population before it is accepted into clinical practice. This proposal is a phase II feasibility study that will test the critical elements necessary for performing such a RCT.

Methods The investigators will recruit participants (≥18 years old) from The Ottawa Hospital, Bruyère Continuing Care (Elisabeth Bruyère Hospital, St-Vincent Hospital), and Providence Care Hospital (Kingston, ON), meeting the well-established clinical Budapest criteria for upper extremity CRPS and having a visual analog scale (VAS) pain score of at least 40 mm (to avoid flooring effect). Participants will be block-randomized by the Ottawa Methods Centre to receive injections of either A) intervention (suprascapular, median, and ulnar nerves) with bupivacaine and triamcinolone acetonide, or B) placebo (saline). All participants will receive standard care for CRPS.

Primary outcomes will focus on crucial methodologic aspects for the future RCT, including: (1) level of recruitment, (2) rate of acceptance from eligible patients to the randomization procedure, (3) blinding efficacy, (4) degree of patient retention, (5) rate of data completion, and (6) rate of adverse events for both the placebo and intervention groups.