Rheumatoid Arthritis - Erosive Changes

A 52-year-old woman with an 8-year history of symmetric polyarthritis of the wrists, MCPs, and PIPs presents with progressive functional loss and inability to grip. Rheumatoid factor is 380 IU/mL, anti-CCP >250 U, ESR 68, and CRP 42. Posteroanterior radiograph of both hands shows symmetric periarticular osteopenia, uniform joint space narrowing at the MCPs and PIPs, and multiple **marginal erosions at the "bare areas"** (marked **A**) of the second and third metacarpal heads and ulnar styloid. Which of the following best explains the pathophysiologic basis for the formation of the erosions marked **A**?