A 62-year-old man complains of shoulder pain for 2 years. He has had 1 course of intra-articular sodium hyaluronate and 6 weeks of physical therapy with little relief. Examination reveals diminished arm flexion and abduction secondary to pain. Radiographs of his shoulder are shown in Figures A and B. According to the American Academy of Orthopaedic Surgeons Clinical Practice Guidelines, what is the next best step?