Review Question - QID 219122

A 36-year-old avocado field worker presents to the clinic four years after having his left forearm fixed surgically in Mexico. He states that roughly two years ago a "pimple" erupted over the ulnar border of his forearm and drained for a few weeks but eventually closed up on its own. Since then, he has had difficulty with numerous similar lesions that intermittently open and close along his scar, as shown in Figure A. His current radiographs are shown in Figures B and C. Lab studies demonstrate a c-reactive protein (CRP) of 6.4 mg/L (normal < 4.9 mg/L) and an erythrocyte sedimentation rate (ESR) of 24 mm/hr (normal < 22 mm/hr). Which of the following represents the next best step in the management of this patient's condition?