A Comparison of The Effects of Lidocaine and Saline Injection on Pain, Disability, and Shear-Wave Elastography Findings in Patients with Myofascial Trigger Points

BACKGROUND/AIMS To compare the effects of lidocaine injection (LI) and saline injection (SI) on the myofascial trigger points (MTrPs) in the trapezius muscle on pain, disability, and shear-wave elastography (SWE) in patients with myofascial pain syndrome (MPS). The secondary aim was to evaluate the correlations between SWE and pain with disability scores. MATERIAL and METHODS This prospective study included 45 patients with MTrPs due to MPS. The patients were evaluated using the visual analog scale (VAS), Neck Disability Index (NDI), and SWE immediately before and 15 days after the injections. The patients were randomly assigned to an LI (n=20, 30 MTrPs) or an SI (n=25, 32 MTrPs) group. The LI group was treated with lidocaine, and the SI group was treated with SI. RESULTS Visual analog scale and NDI scores improved significantly in both groups after injection (p <= 0.05). In addition, 16 MTrPs in the LI group and 3 MTrPs in the SI group were completely resolved. Maximum shear-wave velocity (V(s)max) and mean shear-wave velocity significantly decreased in the SI group after injection (p=0.025). The size of MTrPs decreased in the LI group (p=0.02). Pre-injection V(s)max and resting VAS were weakly correlated (r=0.309). No significant correlation was found on other SWE measurements with VAS and NDI scores (r<0.3). CONCLUSION Lidocaine injection and SI effectively improved the disability and pain in patients with MPS. LI is more effective than SI in reducing the size of the trigger points and resolving MTrPs. SWE findings may not completely reflect the severity of pain and correlate with disability.