Musculoskeletal ultrasonographic evaluation of perineural injection therapy versus therapeutic ultrasound in chronic lateral epicondylitis

Lateral epicondylitis (LE) is a common disorder causing pain and functional limitations especially in athletes and manual workers. There is a growing interest in regenerative injection therapies in chronic LE. One of those suggested is perineural injection (PNI) therapy. The present study aims to find out the efficacy of PNI therapy in the treatment of chronic LE as compared to therapeutic ultrasound (TUS) and to detect if any changes have happened after treatment to the common extensor tendon (CEO) as detected by diagnostic ultrasound (US) examination. Statistical analysis between the 2 groups at the start of the study as regards age, sex, and clinical parameters including visual analog scale (VAS), tenderness grading scale, and Patient-Rated Tennis Elbow Evaluation (PRTEE) Questionnaire revealed a non-significant difference between both groups (p > 0.05). After 12 weeks, within-group analysis showed significant improvement in all clinical outcome measures in both groups compared to the initial assessment. Between-group analysis after 12 weeks showed that the tenderness grading scale and PRTEE score had more significant improvement in the PNI therapy group. However, the two groups were comparable regarding VAS. Within-group US evaluation at the 12th week post-treatment showed a highly significant decrease in hypoechoic areas (p < 0.001) and a decrease in distributed fibrillar pattern in PNI group, while the TUS group demonstrated a significant decrease in hypoechoic areas and tendon thickness (p < 0.005). Between-group US evaluation after 12 weeks showed no significant difference in all assessed US parameters. No complications were observed in both groups. A short-term follow-up regimen of 1 session/week of PNI therapy is significantly more effective than 3 sessions/week of TUS regarding the improvement of pain and functional status. Yet both therapeutic modalities were able to produce significantly positive structural changes in the CEO. The current study highlights the neurogenic inflammation as the primary pain generator in chronic LE and the advantage of its treatment with PNI therapy in chronic and refractory cases.