This patient population will be recruited from the cohort presenting to Women and Children's Hospital for percutaneous fixation of pediatric supracondylar humerus fractures. Participants will be asked to assent to take part in the study and their parents or guardian will be asked to sign an informed consent. Patients will be randomized to a treatment group that receives one dose of pre-operative antibiotics or one that does not. Patients randomized to preoperative antibiotics will receive 25mg/kg cefazolin IV up to 1g or clindamycin 10mg/kg up to 600mg IV in cases of documented allergy to cefazolin. Patients randomized to the no-antibiotic group will receive a saline placebo. The resident, anesthesiologist, circulating nurse and other operating room staff will be instructed to not reveal the patient's randomization to the attending physician so as not to interfere with blinding.