A 28-year-old professional tennis player presents with chronic lateral elbow pain that worsens with backhand strokes and gripping. Physical examination reveals tenderness over the lateral epicondyle, pain with resisted wrist extension, and a positive Cozen's test. MRI shows partial thickness tear of the extensor carpi radialis brevis (ECRB) tendon with associated lateral epicondylitis. The patient has failed 6 weeks of conservative management including NSAIDs, physiotherapy, and corticosteroid injection. Which of the following is the most appropriate next step in management?