Clinical Results and Complications of Shoulder Manipulation under Ultrasound-Guided Cervical Nerve Root Block for Frozen Shoulder: A Retrospective Observational Study

INTRODUCTION: Manipulation under ultrasound-guided fifth and sixth cervical nerve root block (MUC) is a recognized form of treatment for patients with persistent frozen shoulder (FS). This study aimed to investigate the confirmatory hypothesis testing that the MUC has a significant clinical effect on FS refractory to conservative treatments and to assess its adverse events. METHODS: This is a retrospective observational study on patients with FS treated in the past 8 years. Although 77 patients were eligible for this study, only 68 were enrolled. The patients were evaluated immediately before the MUC and at 1, 3, and 6 months after with the use of the Japanese Orthopaedic Association shoulder score. Simultaneously, ranges of motion of the affected shoulder were measured in two directions: forward flexion and external rotation. A paired t test or a Wilcoxon signed-rank test was used to compare differences in outcomes between before and 6 months after MUC. We also assessed any adverse events during and after the MUC. RESULTS: Regarding the primary outcome, confirmatory testing showed statistically significant improvements in every outcome value at 6 months after MUC (p < 0.001). In terms of adverse events, two patients (2.9%) had vasovagal reflex, one (1.5%) had a panic attack during the block procedure, and a 72-year-old female patient (1.2%) had an avulsion fracture of the inferior glenoid during the manipulation procedure, although all of them recovered spontaneously without any residual functional impairment. CONCLUSION: The results showed that significant clinical effects of the MUC on FS were observed through a confirmatory analysis with a sufficient sample size. However, several complications that could occur during the block and manipulation procedures should be considered.