Variations in Neuromuscular Functions After Platelet-Rich Plasma and Dextrose Injections in Chronic Lateral Epicondylitis

Background: Lateral epicondylitis is caused by overuse and manifests as pain, weakness, and difficulty with object manipulation. Platelet-rich plasma (PRP) and dextrose injections have shown promise in reducing pain and improving function. Hypothesis: PRP is more effective for force precision control of the extensor carpi radialis brevis (ECRB) muscle than dextrose injection for patients with chronic lateral epicondylitis (CLE). Study Design: Randomized, double-blinded clinical trial. Level of Evidence: Level 1. Methods: A total of 62 participants (25 healthy subjects and 37 CLE patients) were assigned randomly to either PRP (19) or dextrose (18) groups. Assessments included maximal voluntary contraction (MVC), wrist extension force, questionnaires, sonography, and electromyography assessments. Results: PRP and dextrose had similar effects on clinical questionnaire scores. Compared with pre-test values, only PRP demonstrated a significant increase in MVC (PRP, 75.3 ± 107.7%; P < 0.01; dextrose, 34.0 ± 66.1%; P = 0.08), and greater reduction in force fluctuations (PRP, –27.4 ± 13.3%; P < 0.01; dextrose, –5.4 ± 33.2%; P = 0.22) during post-test wrist extension. After treatment, the PRP group experienced a roughly 41.7% increase in motor units (MUs) with recruitment thresholds (Rec_TH) (pre-test, 3.67 ± 6.15% MVC; post-test, 5.20 ± 8.02% MVC; P < 0.01). The dextrose group showed no significant change (–3.74%) in MU Rec_THs (pre-test, 3.48 ± 6.80% MVC; post-test, 3.35 ± 6.62% MVC; P = 0.75). PRP increased the MU discharge rate with Rec_THs at <30% MVC, whereas dextrose administration elevated MU discharge rate with Rec_THs >20% MVC. Conclusion: PRP may be more effective than dextrose in improving neuromuscular control of the ECRB muscle, particularly for enhancing the scaling of force during wrist extension, attributed to distinct MU activation strategies. Clinical Relevance: Detailed comparison and head-to-head analysis of PRP and dextrose injections offers more options for patients considering injections.