Surgery for diabetic foot infection: drainage and debridement

How surgery stops a foot infection

The foot has connected compartments with tendons running through them, so infection from a small sore can spread up the foot. Swelling can also raise pressure inside a compartment until blood can’t reach the tissue and it dies.⁠^[1] So pus under pressure, or pus mixed with dead tissue, needs prompt drainage, usually within 24 hours.⁠^[1]

Unlike office debridement, which trims dead tissue and callus from an ulcer, diabetic foot infection surgery takes place in an operating room. It follows the infection as deep as it has gone, into tendons, joints or bone.⁠^[1] Dr. Efe Ozturk, a Foot and Ankle Surgeon who is board certified in wound care (FAPWH), performs each step. He drains the infection, removes dead tissue and infected bone, and closes the wound. Once the infection has cleared, he can also correct the foot shape that let the sore form. Clearing the infection is often the first step in limb salvage surgery.

When surgery is considered

Infections are graded mild, moderate or severe (see diabetic foot infections).⁠^[1] The guideline says surgery should always at least be considered for a severe infection, and whenever antibiotics alone are likely to fail.⁠^[1] It advises an urgent surgical opinion for any severe infection, and for a moderate one with:

• extensive gangrene (dead, darkened or black tissue)
• a fast-spreading necrotizing infection
• signs of an abscess beneath the fascia, the tough layer over the muscles
• compartment syndrome, a dangerous rise in pressure inside the foot
• severely reduced blood flow to the leg⁠^[1]

With narrowed arteries, a surgeon and a vascular specialist decide together whether and when to drain the infection and to restore circulation. Severely reduced blood flow should be restored, before or after the infected tissue is removed.⁠^[1] We check circulation with noninvasive testing at our practice (see circulation tests) and coordinate with vascular specialists, who perform revascularization.

Why timing matters

Studies of past hospital records have looked at people with severe, deep infections. Surgery within about 72 hours of arrival was linked with fewer major (above-the-ankle) amputations and more healed wounds than surgery 3–6 days after admission.⁠^[1]

In one study of 106 people with diabetes and a deep foot abscess, none of the 43 operated on right away needed an amputation above the ankle. Of the 63 who first waited about six days in other hospitals, 5 did, and amputation levels were higher overall.⁠^[2]

What happens during the operation

• Opening and draining. An incision over the infected area opens the involved spaces, so pus drains and pressure is released.⁠^[1]
• Debridement. Tissue that has died or is infected is cut away.⁠^[1]
• Bone. When infection has reached bone, the guideline favors removing only as much as needed and avoiding amputation where possible.⁠^[1] See surgery for bone infection.
• Samples. Deep tissue and bone go to the lab for culture and microscope examination,⁠^[5] and tissue identifies the germs more accurately than a surface swab.⁠^[1]
• Open at first. The wound is usually closed later, once the infection is gone, not at the first operation.⁠^[3]

Why a second operation is common

In two trials of moderate and severe foot infections, going back to the operating room within 48–72 hours for repeat drainage was standard, with more returns while infection remained.⁠^[3,5] A planned second look is a normal step, not a sign of failure.

Closing the wound

The wound is closed once the soft-tissue infection is gone and enough healthy tissue remains: with stitches, a local flap of nearby tissue, a thin skin graft or a bioengineered tissue layer.⁠^[3]

A wound that can’t be closed yet may get negative-pressure wound therapy, a sealed dressing on gentle suction that draws fluid away.⁠^[6] The wound-healing guideline gives it conditional support for wounds left after surgery,⁠^[7] but the infection guideline suggests not using it to treat the infection itself.⁠^[1] Dr. Ozturk uses negative-pressure therapy, skin grafts and local flaps when a wound needs them.

Hyperbaric oxygen is not advised just to treat an infection.⁠^[1] It may be considered later for some ulcers with reduced blood flow that good standard care has not healed.⁠^[7] We refer you when it fits; see hyperbaric oxygen therapy.

Sometimes clearing the infection means removing a toe or a ray (a toe with part of its long bone).⁠^[2,8] Researchers commonly count keeping the rest of the foot this way as limb salvage.⁠^[8] Dr. Ozturk removes only what the infection requires (see partial foot amputation). Told you need an amputation? A second opinion can help you weigh the options.

Results

• Most legs are saved. Among 100 people hospitalized with a diabetic foot infection, the leg was kept, with at most part of the foot removed, in 94% of moderate and 80% of severe infections. About half needed some amputation, most often of a toe or part of the foot.⁠^[8]
• Healing takes time. In two trials, 47% to 63% of wounds in the different treatment groups had healed within 12–16 weeks. In the larger trial, about one in five people had the infection return.⁠^[3,4]

Recovery after surgery

Antibiotics continue after surgery, matched to the cultures. Typical guideline courses are 1–2 weeks after a soft-tissue infection is cleaned out and 2–5 days when all infected bone is removed. They run up to 3 weeks if tests on the edge of the remaining bone still show infection, and 6 weeks if infected bone is left in place.⁠^[1]

In the trials, casts, removable boots or healing sandals kept weight off the foot.⁠^[5] We fit offloading boots and, when a wound needs one, a total contact cast, and show you how to get around safely. We usually see you every week or two to clean and measure the wound (see recovery after limb salvage surgery). The Center for Lower Extremity Surgery explains how smoking and diabetes slow healing after foot surgery (external site).

After a diabetic foot infection, most people stay at high risk of new foot problems, so lifelong regular foot checks are advised.⁠^[1] See keeping your foot in remission.

Risks and limits

• Closed wounds don’t always hold. In two pooled trials, about three in four closed surgical wounds were still draining or not fully skinned over when the stitches came out. These took far longer to heal (a median of 114 days versus 28) and more often led to another infection or an amputation within a year. Low toe pressure compared with arm pressure was more common in wounds that broke down,⁠^[5] one reason circulation is checked from the start.
• The evidence has limits. The guideline rates its support for early surgery as conditional, based on low-certainty evidence from reviews of past records.⁠^[1]
• More surgery may be needed, including removing part of a toe or the foot.⁠^[3,8] In one hospital series, about 1 in 5 people with a severe infection needed a below-knee amputation,⁠^[8] which a vascular or orthopedic surgeon performs.

Questions to ask your surgeon

• Does this infection need drainage now, or can antibiotics and wound care come first?
• Is a second operation planned, and how will the wound be closed?
• Is my blood flow good enough to heal?
• How long will I need antibiotics and offloading?

When to seek care

See us within a day or two for any foot wound that isn’t healing, especially if you have diabetes. Call the same day (908-215-5953) if your foot or a wound becomes red, hot, swollen or painful, or if a surgical wound opens or drains more. With diabetes or poor circulation, call the same day, too, for new foot pain at rest or at night.