Ultrasound-guided metacarpophalangeal joint hydrodistension in complex regional pain syndrome: Clinical and technical features

Complex regional pain syndrome (CRPS) frequently causes persistent capsular tightness and pain in the small joints of the hand, particularly the metacarpophalangeal (MCP) joints, with limited response to conservative management. Ultrasound-guided hydrodistension has been used in the management of adhesive capsulitis of the shoulder, although the supporting evidence is mixed, and it offers a plausible but under-explored approach for CRPS-related MCP stiffness. This technical note describes the anatomical, technical, and clinical rationale for ultrasound-guided hydrodistension of the fifth MCP joint in CRPS, illustrated through the real clinical course of a single patient treated by the authors. The technique allows direct ultrasound visualization of the capsule and adjacent neurovascular and tendinous structures, potentially improving safety and accuracy relative to blind injection. Evidence supporting its use in CRPS is currently limited to extrapolation from the adhesive capsulitis literature, and no dedicated controlled trials exist for small-joint disease in CRPS; a clear distinction must therefore be drawn between evidence for technical feasibility, which is described here, and evidence for clinical efficacy, which remains to be established. In the illustrative case, active MCP flexion increased after the procedure, but the patient was also receiving concurrent splinting and supervised rehabilitation, so this improvement cannot be attributed to the injection alone. Ultrasound-guided hydrodistension of the MCP joint is technically feasible and may represent a useful adjunct within a broader, multidisciplinary approach to CRPS-related hand stiffness; controlled studies are needed before any conclusions about efficacy can be drawn.