Corns come in all shapes, sizes and locations, and one of the most unusual
corns is a Lister corn. The term corn is used to describe a callus that builds
up on a toe (vs. a callus that is the same process but usually on the bottom of
the foot). Lister corns are found on the inside and outside of the nail bed, typically on
the 5th toe. Many patients describe a Lister corn by saying that they've
always had a second toe nail on that toe. The second toe nail is actually
hard callus that resembles nail.
Corns form by direct pressure against the skin. The reaction of the skin is to protect
itself by forming more skin. Initially this protective layer of skin is helpful,
but as it thickens this protective layer of skin will increase the pressure applied to the bone and become
bone of the toe is partly responsible for the formation of a Lister corn. The
bone in the tip of the toe is called the terminal phalanx and is shaped a little
like a Mexican sombrero with the tip of the hat pointing to the tip of the toe
and the brim of the hat flaring out at the base of the toe nail. The brim of the
hat can be prominent. And when the brim is prominent, we call it a bone spur.
When direct pressure is applied to the outside of the toe (lateral aspect) by
the shoe, we'll develop a Lister corn on the outside of the toe. When
direct pressure is applied to the inside (medial aspect) of the toe by the
adjacent toe, we'll develop a Lister on the inside of the toe.
Lister corns are unique in that they can also form in the absence of shoe
pressure. Many of us have toes that roll to the side so that the nail doesn't face up, but
rather out to the outside of the foot. This digital position is called varus
rotation of the toe. Varus rotation of the toe rolls the bone in the tip of
the toe so that the brim of the hat is out of the way of the shoe, but now the
brim is in direct and constant contact with the floor. Also, in cases of varus
rotation of the 5th toe, the 4th toe will tend to rest on top of the 5th toe
resulting a medial Lister corn. In cases of fixed varus rotation of the
5th toe, it's not unusual to see a Lister corn on both the outside (lateral
aspect) and inside (medial aspect) of the toe.
Treatment of Lister Corns
Lister corns can be prevented in many cases by wearing shoes with a wide,
round toe box. A wide toe box will decrease direct pressure to the bone spur on
the terminal phalanx.
Periodic trimming of the callus is helpful to relieve pain.
Callus cream is
helpful to soften the corn prior to trimming.
Padding of a Lister corn can be accomplished in a number of different ways.
corns of the medial aspect of the toe can be treated surgically by filing the
spur on the medial aspect of the terminal phalanx. This procedure is
called a condylectomy. The incision for a condylectomy is very small and
often does not require a suture closure. A condylectomy can be performed
in an office or hospital setting. The procedure can be completed in a
matter of minutes and requires only mild sedation and the use of a local
anesthetic. Following a condylectomy, most patients are able to return to
showers and regular shoes within a matter of days.
Lateral Lister corns do not respond as well to a condylectomy. To
surgically correct a lateral Lister corn, a terminal Symes procedure is
recommended. A terminal Symes procedure involves complete resection of the
terminal phalanx and nail. Suture closure is required. A terminal
Symes procedure is performed in a hospital or surgery center with sedation and a
local anesthetic. Patients are ambulatory immediately following a terminal
Symes procedure and may return to regular shoes in 2-3 weeks.