Key Insights On Intractable Plantar Keratoses

Author(s): 
William Fishco, DPM, FACFAS

Due to their unique presentation, intractable plantar keratoses can be challenging to treat and can be particularly painful. This author reviews the biomechanical causes of intractable plantar keratoses, offers pearls on making a diagnosis and provides a guide to surgical techniques for various iterations of the condition.

Metatarsalgia is one of the more common conditions we treat on a daily basis. Corns and calluses are hyperkeratotic lesions located over bony prominences. In the sub-metatarsal region, one may develop an intractable plantar keratosis, which clinically appears as if there is a corn within a callus.

   These hyperkeratotic lesions can be exquisitely painful and, as the name suggests, can be difficult to eradicate. Initial treatment for these often includes: debridement of the hyperkeratotic lesion; the use of topical keratolytic agents; and the use of accommodative padding and/or accommodative orthotic devices.

   I will generally use felt accommodative padding to offload the corresponding metatarsal head to resolve pain. If this technique is beneficial, the patient may do well with an accommodative orthotic device with a metatarsal pad and appropriate sub-metatarsal accommodation. I will recommend a stiff-soled shoe, which in my experience reduces sub-metatarsal pressures. If there is a significant equinus deformity of the Achilles tendon complex, then aggressive stretching and the use of night splinting may be beneficial to reduce sub-metatarsal pressures.

   When conservative treatments are ineffective in managing pain associated with these lesions, then one may consider surgery. Since these skin lesions are secondary to pressure points, the entire goal of any treatment including surgery is to reduce pressure from the underlying bone.

   Before considering surgery, it is paramount that you are certain of the diagnosis of intractable plantar keratosis. Other circumscribed skin hyperplasias that may mimic the intractable plantar keratosis include tyloma (biomechanical callus), verruca plantaris and porokeratoses.

   Warts have a characteristic appearance, which will include black dots in the lesion, a lack of normal skin lines and pinpoint bleeding upon debridement. Porokeratoses can sometimes have the appearance of verruca and intractable plantar keratosis. When you are uncertain, a biopsy can confirm the diagnosis. Certainly, we manage verruca and porokeratoses differently than the osseous surgical procedures for intractable plantar keratosis.

   After making a diagnosis of intractable plantar keratosis and excluding infectious skin conditions such as warts and other benign skin lesions such as porokeratoses, one can formulate a surgical plan. Assuming that the conservative treatments have been ineffective, surgery can be another treatment option.

   We have all learned that the main surgical procedures of the metatarsals, if you will, for intractable plantar keratosis include either shortening of the metatarsal, raising a metatarsal or a condylectomy. Certainly, excision of the intractable plantar keratosis alone will be ineffective. We all tell our patients something to the effect that “calluses are not skin problems but rather bone problems that show up in the skin.” At times, one may excise the skin lesion in addition to bone surgery.

A Guide To The Physical Exam And Precipitating Biomechanical Factors

When examining the foot with an intractable plantar keratosis, the first thing I do is look at the foot type. I make a mental note as to whether it is a high arch or a low arch.

   The second thing I look for is the length pattern of the toes. I want to know if there is a long second toe, which would be suggestive of a Morton’s foot type.

Comments

Nice review Dr. Fishco. I have come to all the same conclusions and have a similar toolbox of procedures. The one thing I do with a Weil now is take a wedge of bone out to shorten and slightly elevate. There is some evidence that a pure Weil plantarflexes the capital fragment somewhat. In the U.K., we call this a Schweil – a Weil-Schwartz combo!

Best wishes

I do take a dorsal wedge as well if I am going to shorten the metatarsal more than 3 mm.

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