A 58-year-old male farmer sustains a laceration to his forearm from a rusty farm tool while working in a field. He presents to the emergency department 18 hours later with a wound that is now swollen, erythematous, and purulent. Culture grows Clostridium tetani. The wound edges are irregular and contaminated with soil. Which of the following factors is MOST critical in determining the risk of impaired wound healing and infection in this patient?