Toe and foot ulcers from hammertoes, bunions and bony prominences

Why a bent toe or bony bump becomes an ulcer

Nerve damage takes away protective feeling in around half of all people with diabetes. Repeated pressure and rubbing on a foot that can’t feel it is the most common cause of a diabetic foot ulcer, and nerve damage can also reshape the foot so the pressure concentrates.⁠^[2] Callus builds over the high spots, and on a numb foot it can break down into an open sore.⁠^[2,4]

Clawed toes also pull the cushioning fat pad away from the ball of the foot: in a small MRI study of people with diabetic nerve damage, it averaged 2.5 mm thick under the metatarsal heads with clawed or hammertoes, against 6.0 mm without.⁠^[5]

Where these ulcers form

Swipe sideways to see the whole drawing.

• Hammertoes, claw toes and mallet toes, among the most common deformities of the forefoot.⁠^[6] Ulcers appear on the tip of the toe, on top of the bent joint where the shoe rubs, and between toes that press together.⁠^[2]
• Bunions and the big toe. A bunion rubs against a tight shoe; a stiff big-toe joint, a different problem, can cause an ulcer under the big toe.⁠^[4,2]
• The ball of the foot. The metatarsal heads can carry too much load, especially with clawed toes or a tight calf that drives the forefoot down; an ulcer can form under any of them, including the fifth, at the base of the little toe.⁠^[5,2,7]
• A collapsed arch. Charcot foot may start as a red, warm, swollen foot; later, bones of the foot can shift or break, leaving a “rocker-bottom” shape.⁠^[4] See Charcot foot and a red, hot, swollen foot.

Shoes, callus and early warning signs

Pointed or high-heeled shoes crowd the toes; a bunion or hammertoe may need an extra-wide or extra-deep shoe, or an insert.⁠^[4] Because a numb foot can’t judge fit, have shoes checked by a trained professional while you stand.⁠^[3]

Thick callus (especially with a dark or bloody spot inside), a blister, a crack, or a red or warm spot over the bump can come before an ulcer; have it treated, not watched.⁠^[3,4] Don’t cut calluses yourself or use corn removers;⁠^[4] we trim them safely at your visits (see corns and calluses (external site)).

How the foot is evaluated

We check which toes are bent and whether they straighten by hand, how the big-toe joint and ankle move, where callus builds, and the foot’s feeling and pulses.⁠^[3] X-rays at the practice show the bones beneath.

If a probe through an ulcer under the ball of the foot reaches bone, or MRI shows bone infection there, the guideline advises considering removing that metatarsal head or reshaping the joint.⁠^[2] We arrange MRI at an outside imaging center and perform bone biopsies when needed; see bone infection in the foot. Infected bone doesn’t automatically mean amputation: options include removing only the infected bone, with antibiotics, or, for some forefoot infections, antibiotics alone.⁠^[8] Told you need an amputation, and it isn’t an emergency? Consider a second opinion before amputation.

Surgery to relieve pressure is not done when blood flow is severely reduced.⁠^[2] Feeling for pulses can’t rule out poor circulation, so the guideline calls for circulation testing for every diabetic foot ulcer.⁠^[9] We do this noninvasive testing at our practice, before any surgery is planned, and arrange a vascular specialist’s opinion when needed; see circulation tests for foot wounds.

Healing the ulcer: offloading and wound care

For a nerve-related ulcer on the sole of the forefoot or midfoot, the guideline’s first choice is a non-removable knee-high device: a total contact cast or a walker that can’t be taken off.⁠^[2] When there’s no significant infection or circulation problem, we fit one at your visit and show you how to get around safely; otherwise a removable device is used, and a severe problem is treated first.⁠^[2] See total contact casting. Ulcers on the top or side of the foot are offloaded with a removable device, shoe changes, toe spacers, orthoses or a toe tendon release, chosen by location.⁠^[2]

At visits, usually every week or two, we clear callus and dead tissue and measure the ulcer; see wound debridement.

How surgery fixes the cause

A device protects the ulcer only while you wear it; surgery changes the foot’s structure, so the relief lasts. For an ulcer under the ball of the foot or the big toe, the guideline supports surgery once non-surgical offloading has not healed it; for an ulcer on the tip or underside of a flexible bent smaller toe, it recommends a toe tendon release as a first-line treatment.⁠^[2]

• A flexible hammertoe or claw toe (second to fifth toes). Releasing the flexor tendon that curls the toe lets it lie flatter. The guideline strongly recommends this small procedure as a first-line treatment for ulcers on the tip or underside of these toes; in the uncontrolled studies it reviewed, about 97% of ulcers healed, in an average of 29.5 days.⁠^[2] It can also be considered to help prevent an ulcer when a flexible hammertoe has thick callus, nail changes or a pre-ulcer spot near its tip.⁠^[3] A rigid toe needs a different operation;⁠^[6] our Center for Lower Extremity Surgery explains hammertoe surgery (external site).
• An ulcer under the big toe. When a stiff big-toe joint is the cause, reshaping that joint (resection arthroplasty) is an option.⁠^[2] In a small study of 41 people with diabetes and this ulcer, those who had the operation healed in 24 days on average, versus 67 days with non-surgical care, and 4.8% versus 35.0% ulcerated again.⁠^[10] When the guideline pooled the studies, the gain in healing was smaller and less certain.⁠^[2]
• An ulcer under the ball of the foot. Options include removing the metatarsal head under the ulcer, an osteotomy that repositions one of the smaller metatarsals, or lengthening the Achilles tendon when a tight calf drives the forefoot down.⁠^[2] In a study of 40 people with diabetes and an uninfected ulcer under the fifth metatarsal head, those who had the head removed healed in 5.8 weeks on average, versus 8.7 weeks with non-surgical care, and 4.5% versus 27.8% ulcerated again.⁠^[7] See removing bony prominences and surgery that takes pressure off ulcers.

Dr. Efe Ozturk, a Foot and Ankle Surgeon who is also board certified in wound care (FAPWH), performs flexor tendon releases, hammertoe correction, metatarsal head resection, exostectomy and Achilles or calf lengthening himself, so the doctor treating your wound is also your surgeon. If your ulcer won’t heal or keeps reopening, we explain which procedure fits your foot and what recovery involves.

Risks and limits

• Pressure can move. Relieving one high spot can create a new one nearby (a transfer lesion), reported after both metatarsal head removal and flexor tenotomy.⁠^[2]
• Heel ulcers. In the trials the guideline reviewed, Achilles tendon lengthening plus a cast was followed by more new heel ulcers than a cast alone.⁠^[2]
• Infection. In one series of 1,465 foot and ankle operations, wound infection followed 9.5% in people with diabetes and 2.4% in others.⁠^[11]
• The evidence. Few of the studies are controlled trials and their quality is generally low, so the guideline’s support for most of these operations is conditional.⁠^[2]

After the ulcer heals

Surgery lowers the pressure, but the foot still can’t feel. After an ulcer on the sole heals, the guideline advises prescribed footwear shown to lower pressure on the sole while walking, worn both indoors and outdoors.⁠^[3] We provide therapeutic shoes, custom inserts and risk-based check-ups. See diabetic foot care (external site), keeping your foot in remission and diabetic foot ulcers.

When to seek care

See us within a day or two for any foot wound that isn’t healing, especially if you have diabetes. Pain is a poor guide: a numb foot may not hurt, even as an ulcer worsens.⁠^[4]