Exostectomy: removing bony prominences under diabetic foot ulcers

What an exostectomy is

The most common cause of a diabetic foot ulcer is repeated high pressure on a foot that has lost protective feeling, and nerve damage can reshape the foot so the pressure climbs.⁠^[1] Where a bone sticks out, such as the low point of a collapsed arch, the skin over it carries the peak load.⁠^[4]

An exostectomy (sometimes called a partial ostectomy) takes away the prominent part of the bone and leaves the rest in place. It doesn’t realign or fuse the foot, so it is a smaller operation than a fusion.⁠^[7,4] Because it changes the foot’s structure, the relief lasts longer and doesn’t rely only on a cast or boot.⁠^[1] A review argued that such surgery also has a place in preventing ulcers and keeping healed feet in remission.⁠^[8]

Where the bump is decides the operation

• Under a collapsed Charcot arch. The midfoot can settle into a “rocker-bottom” shape whose lowest point becomes a bony prominence on the sole. Planing it flat lets the ulcer heal, or keeps one from forming, when casts and braces haven’t been enough.⁠^[4] See Charcot foot.
• Under the ball of the foot. For an ulcer here that non-surgical offloading hasn’t healed, guidelines suggest considering, with an offloading device, removing that metatarsal head, lengthening the Achilles tendon (favored when the calf is tight) or, under the second to fifth heads, cutting and repositioning the bone (osteotomy). Removing the head or part of the joint should be considered when infection has reached that bone or joint.⁠^[1] See surgery that takes pressure off ulcers and surgery for bone infection.
• On the outer edge of the foot. The bump at the base of the little toe (a tailor’s bunion) can ulcerate on the side or underneath. In a series of 10 feet whose ulcers hadn’t healed with offloading, removing the bump and shifting the fifth metatarsal through small incisions healed them in an average of 9.8 weeks, with one infection after surgery.⁠^[9] Our Center for Lower Extremity Surgery explains the tailor’s bunion (external site).
• Over a bunion. For correcting a bunion in general, shaving the bump alone is rarely used: it leaves the joint out of line, and the bunion often returns.⁠^[10] The Center covers bunions (external site).
• On a bent toe or a stiff big toe. For these, the guideline points instead to a tendon release for a flexible bent smaller toe, or to considering reshaping a stiff big-toe joint (arthroplasty).⁠^[1] See ulcers caused by foot deformity.

Who is a good candidate

An exostectomy may suit you when:

• the ulcer sits over the bump and has stayed open despite a proper trial of offloading and wound care⁠^[1,2]
• the foot is stable and, with Charcot foot, the active (warm, swollen) phase has settled; an unstable Charcot midfoot needs an operation that also stabilizes it, such as Charcot reconstruction⁠^[4]
• blood flow is adequate, since guidelines advise against surgical offloading when circulation is severely reduced⁠^[1]
• infection is under control, or the infected bone can be removed in the same operation⁠^[1]

We start with noninvasive circulation testing at our practice, plus a vascular specialist’s opinion when needed; see circulation tests for foot wounds. X-rays at the practice show the bone, and MRI is arranged at an outside imaging center if infection is suspected. A tight Achilles tendon can be lengthened in the same operation.⁠^[4]

How the operation is done

The bone is reached either through the ulcer, which is cut out before the skin is closed, or through an incision beside it.⁠^[4,11] When the wound is large, a flap of nearby skin can be rotated to close it.⁠^[11,4] See skin grafts and flaps.

A simple exostectomy needs no internal hardware and usually means less time immobilized than a reconstruction.⁠^[4] In the randomized trial, surgery was done safely in an outpatient setting.⁠^[3]

Dr. Efe Ozturk, a Foot and Ankle Surgeon who is board certified in wound care (FAPWH), performs exostectomy and metatarsal head resection for the wounds that need them, and follows you from the operation through healing.

What the results show

• A randomized trial. Beyond faster healing, surgery in 42 people with diabetes and uninfected nerve-related ulcers meant fewer infections, fewer relapses over the next six months (3 versus 8) and more satisfied patients.⁠^[3]
• Metatarsal head resection. Pooled guideline data suggest that removing the metatarsal head plus an offloading device may heal more ulcers, and keep more healed, than a device alone (low certainty).⁠^[1]
• The Charcot midfoot. In the Charcot review, average healing times ranged from 2 to about 21 weeks where reported.⁠^[4] In one series of 27 procedures, 20 wounds healed (74%), and six of the seven failures were under the outer (lateral) column; the authors called it a reasonable option for ulcers on the inner (medial) side.⁠^[2] Under the outer column, another team saved 29 of 32 feet as working limbs, although 8 needed further surgery.⁠^[11]

Recovery

Guidelines pair surgical offloading with an offloading device while the ulcer heals.⁠^[1] When that is a knee-high device, we fit it and show you how to get around safely; see total contact casting and non-removable offloading. We usually check and measure the wound every week or two; see wound care visits.

Once an ulcer on the sole has healed, the prevention guideline advises footwear shown to lower pressure on the sole while you walk, worn indoors and outdoors.⁠^[6] We provide therapeutic shoes and custom inserts; see offloading boots and protective footwear and keeping your foot in remission.

Risks and limits

• Pressure can shift. Among people with diabetes who had at least one metatarsal head removed, 41% developed a new ulcer under another metatarsal head over a median of about 13 months. The risk was highest after removing the big-toe metatarsal head and lowest after the fifth.⁠^[5]
• The outer side of a Charcot foot is harder. Exostectomy under the lateral column appears to bring more complications, including new ulcers, repeat surgery and occasionally amputation, and it can worsen the foot’s alignment.⁠^[4] Charcot surgery in general has high complication rates, so the benefit is weighed against the risk for each foot.⁠^[7]
• Wound infection. In 1,465 foot and ankle operations by one surgeon, the wound infection rate was 9.5% in people with diabetes and 2.4% in people without; nerve damage was the strongest link, and smoking added to the risk.⁠^[12]
• The evidence. Most studies are small: the Charcot review’s 11 studies were all retrospective case series, and the guideline’s support for bone procedures such as metatarsal head resection is conditional.⁠^[4,1]

Questions to ask before deciding

• Is my foot stable enough for an exostectomy, or would reconstruction suit it better?
• Is the bone infected, and is my circulation good enough to heal the incision?
• Where could pressure move afterward, and what footwear will I need?
• Would lengthening my calf help at the same time?

Told you need an amputation? A limb salvage second opinion can help you see whether a smaller operation could save the foot.

When to seek care

If you have diabetes or numb feet and one foot turns red, warm or swollen, call us the same day, even if it doesn’t hurt, and keep weight off it until you’re seen. With unbroken skin, this may be active Charcot (infection can look similar), and guidelines advise knee-high offloading right away while tests are done.⁠^[7] See a red, hot, swollen foot. Foot pain at rest can be a sign of severely reduced blood flow;⁠^[13] see foot pain at night. See us within a day or two for any foot wound that isn’t healing, especially if you have diabetes.