There is always debate about which lacerations can be closed, but not a lot of literature to back it up. Here are some good rules to follow:

• In general, close all face and scalp lacerations. They almost never get infected. Complicated ones may need extra care, debridement, or involvement of a plastic surgeon. 
• Closing lacerations that are more than 24 hours old is risky (except for the face). They tend to be colonized with skin flora and become infected much more frequently.
• Most other lacerations can be closed primarily within 24 hours. For the most part, it doesn’t matter what the cutting instrument was. One exception is an object that is heavily contaminated (e.g. freshly used pitchfork). Most knives don’t fall into this category. They are clean, but not sterile and the risk of infection is low.

All wounds should be inspected for foreign bodies. On occasion, this may require an xray. But remember that many foreign objects (wood, glass) are not radiopaque and will be invisible. Next, the wound should be copiously irrigated with sterile saline to flush out any small particles and reduce bacterial counts. Finally, if the edges are ragged the wound should be sharply debrided.

Antibiotics are not usually needed, since the few bacteria left will be rapidly taken care of by the patient’s immune system. If there are worries about contamination or the patient is immunocompromised, a very brief course of antibiotic is recommended. Tetanus toxoid should be given if indicated.

The most important issue is patient education. The signs and symptoms of early wound infection should be explained, and a phone number or location for followup should be clearly listed.

Bottom line: All lacerations can be safely closed within 24 hours, with a few exceptions.