Surgical Treatment of Transversal Overcurvature of the Nail Plate ("Pincer Nail")
Tuesday, December 05, 2006
The transverse overcurvature of the plate is the widening of the
ungual plate across the finger. The increased ungual plate
curvature can be slight or round, or even a 360º turn. Looking at
the finger from the front, the pincer-shaped nail can be observed.
Additionally, the ungual plate may be flat at the center and then
abruptly curved at the lateral folds so that a 90º angle is
Names such as incurved,1 reverse,2
endonychia constrictiva,2 tile,3
omega,3 trumpet,3 and plicated nails (90º on
the sides)3 all refer to the overcurvatures of ungual
beds as proposed by Samman.4
The term "pincer nail" was proposed by Cornelius and
Shelley.5 They studied three cases whose common elements
were the front aspect of the ungual plate pinching the bed, severe
pain, and bone changes. The angle measurement, based on which a
given nail is regarded as overcurved, is subjective. Our experience
has been that the angle has never been less than 40º in any
Hereditary6 and acquired cases have been disclosed.
We have found no logical explanation for the appearance in the
acquired cases, such as arteriovenous fistulas,7
medications,8 and Kawasaki disease.9 In such
cases, the shape of the ungual plate returns to normal whenever the
The hereditary group represents almost all cases. The most
consistent explanation for these cases is the bone change in the
distal phalanx3 with reabsorption of the surrounding
tissues. The most severe overcurvature cases show ungual plates
that were virtually flat and then became convex, curving inward and
creating a depression beside the lateral ungual folds. Ungual
plates adhere more on the sides than at the center due to
ligament-like structures.10 These structures become
weaker and then tend to increase the ungual plate curvature in
these regions. In some cases, ungual plates may detach from their
beds, resulting in overcurvatures such as those found in
onychomycosis,11 psoriasis,3 and
Many clinical and surgical treatments have been proposed. Among
the clinical ones, ortheses14 and occlusive uric
acid15 are not permanent as they do not correct the
Surgical treatments can be divided, for didactic purposes, into
- Conservative, without bone
These treatments include avulsion of the ungual plate,5
total destruction of the matrix,16,17 unilateral or
bilateral matricectomy,17 dermal grafting,16
and CO2 laser use20,21
- Aggressive, with bone correction:
These treatments can be associated with other procedures
with no healing by second intention:
- Ungual bed detached from the bone, bone correction, and
re-placement of the bed with grafting, if
- Ungual bed detached from the bone, bone correction with
grafting if necessary,22,24 and the widening of the bed
through the removal of the skin from the finger's lateral and front
faces through the Dubois procedure
Such corrections may be aligned with unilateral or bilateral
- Highly aggressive: These treatments, proposed
by us,26,27 include bone correction, bed widening
through the removal of a large amount of wide "U"-shaped skin from
the digit's lateral and front faces, with healing by second
intention, including the portion removed from the bed
During this procedure, in addition to the removal of a wide
strip of "U"-shaped skin, the distal portion of the ungual bed is
removed, preserving the proximal portion, which goes 2 mm beyond
the lunula. The bone correction of the distal phalanx is carried
out with a Joseph knife. The distal phalanx bone becomes exposed
and hemostasis is conducted by separate stitches on the free skin
border and pressure dressing. The healing by second intention takes
about 40 days for lateral folds and 2-3 months for the bed.
Figure 1. 360º turn (trumpet
Figure 2. Same patient featured in
Figure 3. Same patient, after highly
Figure 4. Same patient, after
Pros and Cons of Treatment Options
All procedures have their own pros and cons. For cases that are
diagnosed early, less aggressive treatments may be successful. For
more severe cases with large angle changes, however, more
aggressive treatments are appropriate.
Among the less aggressive treatments, dermal
grafting18 underneath the bed is very useful - except in
the most acute cases, which require a more aggressive
All the surgical procedures mentioned are appropriate for
Several procedures are intended to widen the ungual bed by
removing the skin from the digit's front and lateral faces under
the Dubois procedure, in which the formed defect is sutured. In our
opinion, the widening of the ungual bed resulting from such a
procedure is smaller28 than that with the healing by
second intention, as the suture causes the skin of the plantar
region to rise. Our procedure does not produce a large bed
Grafts are used whenever one does not want the corrected bone to
be exposed, yet their results are unpredictable. The most common
complication is the non-adherence of the ungual plate to the
hyponychium region. The question is whether the distal phalanx
healed by second intention will allow the bed to advance or not.
The answer is yes. We noticed the bed moves forward adhered to the
ungual plate and will move forward over the healed tissue if no
dystrophy occurs in the bed-generating matrix. Our observation is
that the ungual plate adhered to the bed fails to move beyond the
grafted region in some cases, particularly in the distal third.
With our method, the healing by second intention allows the ungual
plate to move forward adhered to the totality of the bed. This
tissue healed by second intention does not induce adherence to the
bone as firmly as grafts.
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