The old term used to be compound fractures but open fractures refer to any fracture that has associated break in the skin. The simplest way to classify open fractures, and the most common is that described by Drs. Gustilo and Anderson. There are others including that by Tscherne et al and that promulgated by the Arbeitsgemeinschaft fur Osteoysnthesefragen (AO).
Grade I: Fracture with a break in the skin of less than one centimeter with minimal soft tissue disruption.
Grade II: Fracture with a break or laceration of the skin from one to ten centimeters in length, typically low energy.
Grade III: Fracture with a break or laceration of the skin greater than ten centimeters in length usually high energy and extensive soft tissue injury, segmental fractures.
The AP student should keep in mind that the place and mechanism of injury are important. For example a fall in the kitchen resulting in a grade I fracture of the distal radius is not the same as a grade I fracture of the distal radius suffered in the barnyard.
Knowing the fracture grade (and place and mechanism of injury is important because this in turn informs the AP of the type of antibiotic(s) to be given to decrease the chance of infection. Generally speaking Grades I and II should get a first generation cephalosporin (e.g. cefazolin) while Grade III will additionally require gram negative coverage which can be an aminoglycoside, vancomycin, or piperacillin-tazobactam (Zosyn). Farm injuries will require penicillin to prevent Clostridial infection. Most studies show no additional decrease in infection rates if the antibiotics are given for more than 24 hours after skin closure. Exact dosing requirements for the antibiotics will depend on patient weight, renal status in some cases, and institutional protocols.
Since nothing is ever as simple as 1, 2, 3 the AP student needs to know that Grade III fractures have several subtypes.
Grade IIIA: Standard open wound greater than ten centimeters without significant soft tissue loss (i.e. the wound can be closed primarily)
Grade IIIB: Standard open wound greater than ten centimeters that requires rotational flap or free tissue transfer to provide wound closure.
Grade IIIC: Standard open wound greater than ten centimeters but there is a vascular injury that if not repaired the limb will not be viable.
The AP should not forget to check on tetanus status. If the patient has not been vaccinated in the last five years an booster is appropriate in the presence of an open fracture.
Reference: Garner MR, Sethuraman SA, Schade MA, Boateng H. Antibiotic Prophylaxis in Open Fractures: Evidence, Evolving Issues, and Recommendations. JAAOS: 2020; 28(8) 309-315
Orthopedic Surgery for AP students, an Introduction 