Intervention: Oral N-acetylcysteine capsules, 600 mg twice daily.

Timing/Duration: Begin the evening before surgery (≤24 h pre-op) and continue through Post-op Day 14 (total 15 days; bottle overfilled to cover missed doses).

Administration: Self-administered at home; counseling at baseline dispense; pill diary + pill counts.

Concomitant care: All peri-operative care per standard of care (SoC), including multimodal analgesia; no high-dose antioxidant supplements; nitrates excluded.

Objective: Test whether peri-operative NAC improves early pain, function, and recovery via redox-immune modulation.

Intervention: Matched inert capsules (e.g., microcrystalline cellulose), identical in size/appearance/labeling to NAC.

Timing/Duration: 600 mg-equivalent capsule count, twice daily, evening before surgery through Post-op Day 14.

Administration: Same counseling, diary, and adherence checks as NAC arm.

Concomitant care: Identical SoC allowances/restrictions as NAC arm.

Intervention: Oral N-acetylcysteine capsules, 600 mg twice daily.

Timing/Duration: Begin the evening before surgery (≤24 h pre-op) and continue through Post-op Day 14 (total 15 days; bottle overfilled to cover missed doses).

Administration: Self-administered at home; counseling at baseline dispense; pill diary + pill counts.

Concomitant care: All peri-operative care per standard of care (SoC), including multimodal analgesia; no high-dose antioxidant supplements; nitrates excluded.

Objective: Test whether peri-operative NAC improves early pain, function, and recovery via redox-immune modulation.

Patient-Reported Outcomes Measurement Information System - Pain Interference T-score metric: mean = 50, SD = 10 Higher scores = worse outcome (greater pain interference with daily activities, social, cognitive, emotional, and physical functioning)

Patient-Reported Outcomes Measurement Information System Physical Function T-score metric: mean = 50, SD = 10 Higher scores = better outcome (greater ability to carry out physical activities such as mobility, self-care, and instrumental activities)