How Low Should You Go: Novel Device for NailTrephination

DAVID CIOCON, MD,� TR GOWRISHANKAR, PHD,y TERRY HERNDON, BS,y AND

ALEXA B. KIMBALL, MD, MPH�

BACKGROUND The most commonly used treatment for subungual hematomas is nailtrephination, a technique that is not standardized and that poorly controls for trephinationdepth.

OBJECTIVE The objective was to test the safety and tolerance of a new device for nailtrephination that uses innovative ‘‘mesoscission’’ or microcutting technology to createholes of specific depths in the nail plate without penetrating the nail bed.

MATERIALS AND METHODS Fourteen adult subjects with healthy toenails had five holesdrilled in a random single-blind fashion at different test settings into their right greattoenail with this device and were assessed for pain and pressure tolerance as well asperioperative and postoperative complications.

RESULTS Nail trephination with this device in this small pilot study was controlled andwell tolerated.

LIMITATIONS The study population was small (n = 14) and the follow-up evaluation reliedon patient self-report, which is not always reliable. The follow-up period was only 1 weekand did not allow for evaluation of permanent nail plate deformity.

CONCLUSION Mesoscission may be a controlled and practical alternative to traditionalnail trephining methods.

Path Scientific, LLC (Carlisle, MA) provided the equipment and 100% of the funding for thisstudy. Dr. Ciocon and Dr. Kimball are affiliated with the Department of Dermatology, Brighamand Women’s Hospital (Boston, MA). Neither has any financial relationship with Path Scientific.Dr. Gowrishankar is an employee of Path Scientific but has no financial interests in the com-pany. Terry Herndon is President of Path Scientific, LLC, and provides 100% of funding for itscosts. He is the owner and inventor of the PathFormer device.

Until the late 1990s, most cli-

nicians had advocated nail

plate removal and formal repair

of the nail bed for subungual

hematomas involving greater than

25% of the nail bed. Recent

studies have demonstrated, how-

ever, that uncomplicated sub-

ungual hematomas, regardless of

size, can be treated with simple

nail trephination, or drilling a

hole in the nail plate to drain the

blood with a preheated hole-

making device.1,2 Despite its

widespread acceptance, nail

trephination remains unstandard-

ized. Clinicians have not reached

a consensus about what depth

should be reached or what in-

strument should be used in creat-

ing the holes. While some

advocate the use of a heated paper

clip, others advocate using an

electrocautery device or a prester-

ilized needle.3,4 In none of the re-

ports describing these methods

has the issue of hole depth been

considered. For most treating

physicians, the endpoint of such a

procedure is the evacuation of

subungual blood, regardless of

whether the trephination instru-

ment penetrates the underlying nail

bed. Potential hazards of nail bed

penetration include pain, infection,

permanent onychodystrophy, and

& 2006 by the American Society for Dermatologic Surgery, Inc. � Published by Blackwell Publishing �ISSN: 1076-0512 � Dermatol Surg 2006;32:828–833 � DOI: 10.1111/j.1524-4725.2006.32168.x

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�Clinical Unit for Research Trials in Skin, Brigham and Women’s Hospital and Massachusetts GeneralHospital, Boston, Massachusetts; yPath Scientific, LLC, Carlisle, Massachusctts

the creation of open fractures in

cases where subungual hema-

tomas are associated with closed

fractures.5,6 In this report, we in-

troduce the PathFormer, a stand-

ardized device that can create

holes in the nail plate in a con-

trolled hygienic manner without

penetrating the nail bed.

The device, manufactured by Path

Scientific (Carlisle, MA, USA),

uses innovative ‘‘mesoscission’’ or

microcutting technology to gener-

ate microconduits in human nails.

The nail plate is scissioned (cut)

with a 400 mm diameter tissue

cutter in a hand-held device con-

taining two small electric motors.

One motor rotates the cutter, and

the second moves the cutting mo-

tor tip up and down. The motors

are powered by a portable 9 V

power supply. The cutting motor

is connected to an electronic con-

trol that measures the electrical

resistance between the rotating

cutter and a pair of electrocardi-

ogram electrodes on the patient’s

skin. This control can be cali-

brated to reverse the cutting mo-

tor at the detection of a preset

electrical resistance. Because the

nail plate is highly keratinized, it

normally has a high electrical re-

sistance, approximately 5 MO, as

calculated in preliminary manu-

facturer experiments. In contrast,

the normal resistance of the nail

bed is much lower, in the 10 to

20 kiloOhms (k) range, largely

because of the higher water con-

tent of nail bed tissue. During the

drilling process, the removal of

each successive layer of the nail

plate results in a reduction in

electrical resistance at the site of

the hole. When the measured

electrical resistance has decreased

to the trigger resistance, the cut-

ting tool instantaneously and au-

tomatically pulls away from the

nail plate (Figure 1). The trigger

set point can be increased or de-

creased depending on the depth of

nail plate to be reached. The pur-

pose of this study is to assess

safety and pain tolerance in a

group of healthy adult subjects

treated with this device.

Materials and Methods

Study Population

The protocol was reviewed and

approved by the Institutional Re-

view Board of Brigham and

Women’s Hospital and the Mas-

sachusetts General Hospital.

Written informed consent was

obtained from each subject. Adult

subjects from the greater Boston

area with clinically healthy toe-

nails and a toenail width greater

than 2 cm were enrolled after re-

sponding to an internet advertise-

ment for the research trial.

Exclusion criteria included a his-

tory of diabetes, a history of on-

ychomycosis or onychodystrophy,

a history of peripheral neuropa-

thy, and current use of daily pain

medication. Relevant past medical

history and all current medica-

tions were documented.

Study Design

Five holes of varying depth, using

trigger resistance settings of 90,

45, 35, 25 k, and control (minimal

penetration of the nail plate sur-

face), were drilled in a single-blind

random order into the subject’s

right great toenail using the Path-

Former.

Preliminary manufacturer experi-

ments determined that a trigger

setting of 25 k was low enough to

allow complete drilling through

the nail plate without penetration

of the nail bed, as indicated by

sharp pain or bleeding. We chose

test settings of 90, 45, 35, and

25 k to allow for partial to com-

plete drilling through the nail

plate without nail bed penetra-

tion. For each subject undergoing

toenail mesoscissioning, a pair of

disposable ECG electrodes was

first placed on top of the right

foot of the subject. The device was

checked for proper electrode con-

tact with the skin. After the toe-

nail plate was cleaned with 70%

isopropyl alcohol, the nosepiece

of the device was placed flush

with the surface of the right great

toenail. Individual microconduits

were created using the above set-

tings. For the control hole, the

cutter was lowered to the surface

of the nail; the drill was then

started and quickly withdrawn

with minimal penetration of the

nail plate. After each use, the

nosepiece and individual cutter

tips were removed, cleaned with

Manu Klenz ultra-disinfecting so-

lution, and autoclaved to 2531F

for 30 min.

The holes were evenly spaced

0.5 cm distal to the lunula of the

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nail. After each hole was created,

the subject was asked to rate both

the pressure and pain felt during

the procedure according to a vis-

ual analog scale ranging from 1 to

10, 1 being no pain or pressure

and 10 being severe excruciating

pain or pressure. The subject was

given a bandage to place over the

nail plate overnight. One week

later, the subject was contacted by

telephone to inquire about the

presence of postoperative ery-

thema and purulence, pain, and

any evidence of bleeding or

bruising. Subjects were also asked

whether they would undergo

treatment with this device again

on the basis of their initial expe-

rience.

Statistical Analysis

The study was powered to detect

a two-point difference on the pain

and pressure scales, with a power

of 0.80 and an a level of 0.05,

which required the participation

of at least 10 subjects. Statistical

analysis of pain and pressure rat-

ings was performed using the

Wilcoxon matched-pairs signed

rank test.

Results

Fourteen subjects were screened,

all of whom met criteria for en-

rolment. The study population

consisted of nine women and five

men. The mean ages for all sub-

jects, male subjects, and female

subjects were 37, 42, and 34,

respectively.

During the drilling process, no

bleeding events were reported,

indicating no nail bed penetra-

tion. One patient retracted her

foot during one of the drilling

trials because of reported

Figure 1. Before and after photographs of the mesoscissionprocess (A and B) and the mesoscission device (C).

D E R M AT O L O G I C S U R G E RY8 3 0

H O W L O W S H O U L D Y O U G O

‘‘anxiety’’ and not pain (pain rat-

ing was 3 on the 1–10 scale). All

14 subjects completed the indi-

vidual drilling trials and the fol-

low-up interview at 1 week.

On the provided visual analog

scale, the mean pain ratings

among all subjects for the control,

90, 45, 35, and 25 k holes were

1.1, 1.4, 1.0, 1.1, and 1.6, re-

spectively. As shown in Figure 2,

these pain ratings showed a slight

depth-dependent increase, partic-

ularly when comparing the mean

pain rating for the deepest hole

with control. However, as the

study was powered to detect a

two-point difference on the pain

scale, a clinically meaningful dif-

ference, the difference between

the deepest hole and control was

not statistically significant (Table

1, p = .06).

The mean pressure scores for the

control, 90, 45, 35, and 25 k holes

were 1.2, 1.6, 1.6, 2.0, and 2.5,

respectively, indicating a modest

depth-dependent increase for

pressure. Using a 95% confidence

level, we detected a statistically

significant difference in pressure

scores of the 35 and 25 k holes

relative to control (Table 1,

p = .016 and .012, respectively).

However, the mean pressure rat-

ings for both holes were still less

than 3, which corresponded to ‘‘I

feel a little bit of pressure’’ on the

1 to 10 visual analog scale.

Therefore, despite the statistically

significant quantitative increase,

the qualitative difference in pres-

sure relative to control remained

minimal.

A gender subgroup analysis

showed no significant difference

in pain and pressure scores be-

tween male and female subjects.

We also found that pain and

pressure ratings for different

holes were not affected by the

sequence in which the holes

were drilled.

All 14 subjects had their toenail

photographed. A representative

image is shown in Figure 3. None

objected to the cosmetic appear-

ance of their toenail after the

drilling trial. At 1-week follow-

up, none of the 14 subjects re-

ported any complications. When

asked whether they would under-

go the drilling procedure again if

needed, all 14 subjects stated that

they would.

TABLE 1. Mean Pain and Pressure Ratings for Different Trigger Re-

sistance Settings Relative to Control

Hole Setting Mean Pain Rating p value, mean versus control

Pain (K)

90 1.4 0.50

45 1.0 1.0

35 1.1 1.0

25 1.6 0.063

Control 1.1 1.0

Pressure (K)

90 1.6 0.25

45 1.6 0.13

35 2.0 0.016

25 2.5 0.012

Control 1.2 1.0

K, kiloOhms.

1.0

3.0

5.0

7.0

9.0

Control 90K 45K 35K 25K

PainPressure

Figure 2. Mean pain and pressure ratings (with SD) as a functionof decreasing trigger resistance settings. The lower the triggerresistance setting, the deeper the hole through the nail plate.

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Discussion

Subungual hematomas are accu-

mulations of blood that collect in

the space between the nail plate

and nail bed. They can result from

an acute crush injury, such as a

direct blow to the nail, or from

repeated minor trauma, such as

running in undersized shoes. The

pressure generated from the ac-

cumulated blood can cause in-

tense pain and possibly permanent

nail apparatus damage and often

requires decompression. Nail

trephination has been used as a

treatment for subungual hem-

atomas for decades.7,8 Despite its

proven efficacy, its clinical use

was limited to hematomas in-

volving less than 25% of the vis-

ible portion of the nail. The

advantages of nail trephination

are threefold. It prevents addi-

tional pain and trauma to the

nail bed from surgical manipula-

tion. It decreases the risk of per-

manent nail plate deformity as

the nail matrix is left intact,

and it avoids the cost and incon-

venience of an extended surgical

procedure that includes nail plate

removal.2

Early reports suggested that pa-

tients with larger hematomas

were likely to have associated nail

bed lacerations in need of primary

repair. Failure to repair such lac-

erations, they argued, increased

the risk for permanent cosmetic

and functional abnormalities,

such as nail streaks and depres-

sions, abnormal nail plate re-

growth, or nail splits.9 Subsequent

studies have demonstrated, how-

ever, that trephination alone

should suffice for the treatment of

uncomplicated subungual hem-

atomas, regardless of size.1,2,10,11

The procedure is quick, cost-

effective, and poses minimal

structural or infectious risk as

long the nail bed is not violated.

To date, the largest published se-

ries of uncomplicated subungual

hematomas treated with nail

trephination consisted of 123 pa-

tients who presented to an emer-

gency department, 94 of whom

followed up for 5 to 12 months.12

Although 85% of the followed-up

patients reported an excellent

outcome (i.e., no residual abnor-

mality), 11% of these patients still

developed a significant cosmetic

abnormality. Infection occurred in

five patients, although there was

no correlation between the inci-

dence of infection and either

hematoma size or presence of

fracture. Potential causes of these

complications include severe

damage to the nail matrix

and accidental penetrations of

the nail bed by the trephining

instrument.

Inadvertent penetration of the nail

bed is inherent to current trephi-

nation techniques because they do

not incorporate a standardized

method for controlling the depth

of the holes. For most physicians,

the end point of trephination is

the relief of pressure or expression

of blood, regardless of the depth

reached by the trephining instru-

ment.13 In one report describing

trephination, clinicians are in-

structed to tap rapidly on the nail

plate with an electrocautery or

heated paper clip until ‘‘resistance

from the nail (plate) gives way’’ to

‘‘avoid damaging the nail bed.’’5

In such a case, hole depth is de-

termined subjectively by the

Figure 3. A mesoscissioned toenail with an arrow pointing to thedeepest (25 k) hole.

D E R M AT O L O G I C S U R G E RY8 3 2

H O W L O W S H O U L D Y O U G O

operator without objective con-

trols to prevent nail bed violation.

In this phase I study, we introduce

the PathFormer, a device that can

perform nail trephination in a

controlled, standardized, and

quantitative manner. Using the

measured difference in electrical

resistance between the nail plate

and nail bed, the device creates

holes in the nail plate with mini-

mal discomfort and without pen-

etrating the nail bed. In this small

pilot trial, we found that nail

trephination with the PathFormer

was feasible and well tolerated.

Further studies involving subjects

with uncomplicated subungual

hematomas are needed to deter-

mine the efficacy of this device for

this condition. Use of the device

for the treatment of onycho-

mycosis may be another future

application, as a means of en-

hancing subungual delivery of

topical medications.

References

1. Seaberg DC, Angelos WJ, Paris PM.

Treatment of subungual hematomas

with nail trephination: a prospective

study. Am J Emerg Med 1991;9:209–10.

2. Roser SE, Gellman H. Comparison of

nail bed repair versus nail trephination

for subungual hematomas in children.

J Hand Surg 1999;24:1166–70.

3. Kaya TI, Tursen U, Baz K, Ikizoglu G.

Extra-fine insulin syringe needle: an ex-

cellent instrument for the evacuation of

subungual hematoma. Dermatol Surg

2003;29:1141–3.

4. Pratt LK. Trephining of nails: an overview

of the commonest cause for trephining and

the actual procedure of trephining. Accid

Emerg Nurs 1998;6:167–9.

5. Subungual hematoma: a case report.

National Center for Emergency Medicine

Informatics. Available at: http://

www.ncemi.org/cse/cse1007.htm

6. Kleinert HE, Putch SM, Ashbell TS, et al.

The deformed finger nail, a frequent re-

sult of failure to repair nail bed injuries.

J Trauma 1967;7:177–90.

7. Ranjan A. Subungual hematoma. J Ind

Med Assoc 1979;72:187–8.

8. Melone CP, Grad JB. Primary care of

finger nail injuries. Emer Med Clin North

Am 1985;3:255–61.

9. Simon RR, Wolgin M. Subungual hem-

atoma: association with occult laceration

requiring repair. Am J Emerg Med

1987;5:302–4.

10. Batrick N, Kambiz H, Freij R, Mackay-

Jones K. Treatment of uncomplicated

subungual hematomas. Emerg Med J

2003;20:65.

11. Salazard B, Launay F, Desouches C, Fin-

gertip injuries in children: 81 cases with

at least one year follow-up. Rev Chir

Orthop Reparatrice Appar Mot 2004;90:

621–7.

12. Meek S, White M. Subungual hem-

atomas: is simple trephining enough?

Accid Emerg Med 1998;15:269–71.

13. Abimelec P, Dumontier C. Basic and ad-

vanced nail surgery. In: Scher RK, Daniel

CR., editors. Nails: diagnosis, therapy,

surgery, 3rd ed. Philadelphia: Elsevier/

Saunders, 2005:p. 301.

Address correspondence and reprintrequests to: Alexa B. Kimball, MD,MPH, Department of Dermatology,Brigham and Women’s Hospital,221 Longwood Avenue, Boston,MA 02115, or e-mail:harvardskinstudies@partners.org

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