Key Considerations In Treating Lister’s Corn

I want to dedicate this blog to Perry Horton, DPM, who recently passed away. He was one of my attendings in residency. I have fond memories of Dr. Horton. He had the utmost confidence his Northlake Medical Center residents. Dr. Horton would tell us what he wanted done in surgery and to ask for help if we had any questions or problems. He would generally sit on a stool and tell stories while we performed surgery. He would take an occasional peek in on what we were doing and always knew we would do a great job.

Dr. Horton always brought us straightforward cases like bunions and hammertoes. To that end, I want to talk about something simple yet common in a podiatry practice: Lister’s corn (Durlacher’s corn).

The Lister’s corn is a focal hyperkeratosis juxtaposed to the nail plate on the fifth toe. One may find this corn on the medial side, lateral side or both. Often, patients present with the complaint of an ingrown nail, a split nail, an extra nail or concern of a fungus infection.

There are multiple factors that make one predisposed to having this condition. First and foremost is symphalangism of the middle and distal phalanges. With only two joints in the fifth toe, there is more rigidity of the toe and it is less forgiving, if you will, in a shoe. My experience is that at least 90 percent of all patients who have Lister’s corns have symphalangism. That is a good case in point why we do not do arthrodesis procedures on the fifth toes.

The second most common denominator is varus rotation of the fifth toe. In this case, the lateral side of the toe is getting ground reactive forces and increased pressure.

As you know, even though we tell our patients that they have a “bone spur,” it is normal anatomy causing the problem. The condyle of the base of the distal phalanx is the anatomic area causing the problem. I will explain to my patients there are three bones in the pinky toe. The first bone is the longest and shaped like a rectangle, the middle bone is a square, and the last bone under the nail is shaped like a hat. The brim of the hat can be a pressure point under the skin when one is walking and/or wearing shoes.

About 12 years ago, I co-authored a paper on the topic.1 Despite advances in surgery, nothing has changed as far as how I treat this condition surgically. The photos in this blog illustrate the technique.

Pertinent Insights About The Incision

One would make a double semi-elliptical incision overlying the hyperkeratotic lesion. Remove the skin wedge and visualize the condyle. Use the small end of the Ragnell retractor or double skin hooks to retract the soft tissues. Use a rongeur or bone nipper to remove the exostosis, and then utilize a small bone rasp to make the bone flat.

Close the skin using nylon. It usually takes two to three sutures to close the skin. Sometimes, you will need to suture the skin to the nail. It is easier to start the suture needle in the skin and then pierce through the nail bed and nail plate versus going through the nail plate first.

Now I know a lot of my readers are going to say that such an “extensive” incision is not necessary. They may say that all you need to do is make a stab incision with a chisel blade, burr down the bone with a side-cutting burr and then stick a Steri-Strip on it. If it works great for you, do not change your approach.

I would counter that the “minimal” incision works … most of the time. My opinion is that a rotary burr, whether it is a Shannon 44 or a small round or egg burr, will not make a flat surface. If there is not a flat surface, then you have a greater chance of having a recurring hyperkeratosis.

Final Notes

For the sake of completeness, remember if there is a significant frontal plane deformity of the toe, usually varus, then you will need to address that in addition to the bone work. You may need to do a derotational skin plasty and/or flexor tenotomy.

We are all guilty of looking at these cases as a slam dunk and don’t put much time and effort into surgical planning like we do with other more complicated foot surgeries. It is always a slap in the face when a simple Lister’s corn surgery fails.

Thank you, Dr. Horton. You will be missed.

Reference

1. Alder DC, Fishco WD, Ruch JA. Surgical treatment of Lister’s corn. A case illustration. JAPMA. 1998; 88(1):30-33.



Mark Nellermoe DPMsays: February 24, 2011 at 5:51 pm

I like your idea of the derotational procedure. If the procedure you outlined here is not derotated, have you experienced any scar troubles as it could end up receiving ground reactive forces?

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William D. FIshco, DPMsays: February 24, 2011 at 10:46 pm

Mark:

I have not had any scar problems although I tell my patients that there will be some transient hyperkeratosis while the skin is healing. Normally, the hard layer of skin overlying the incision site will flake off. It is rare that I have to do a derotational skin plasty. If the condyle is flat, more likely than not, the corn goes away. If there is a double corn, PIPJ and Lister's, then I am more likely to do a derotational skin plasty with PIPJ arthroplasty and the condylectomy as outlined above.

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