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Assessment of the Presence
or Absence of Palmaris Longus and the Fifth
Superficial Flexor Tendon in the Iranian Population:
Are these tendons evolutionary?
Afshin Ahmadzadeh Heshmati (1)
Ali Karbalaeikhani (2)
Alireza Saied (3)
Mohsen Rouhani (4)
Mahsa Aboei (4)
Farzad Abroud (4
)Elahe Havoshk (4)
(1) Assistant Professor of orthopaedics, Kerman
Neuroscience research centre, Dr Bahonar Hospital,
Kerman University of Medical Sciences, Kerman,
Iran
(2) Assistant Professor of hand surgery, hand
surgeon, AJA University of Medical Sciences,
Emam reza hospital, Tehran, Iran
(3) Associate Professor of Orthopedics, Medical
Informatics Research Centre, Kerman University
of Medical Sciences, Kerman, Iran
(4) Student of Medicine, Students Research Committee,
Kerman University of Medical Sciences, Kerman,
Iran
Correspondence:
Saied A.R. M.D., Orthopedics department,
Dr. Bahonar hospital, Kerman neuroscience research
center,
Tel: +983412114375, +989133410521, telefax:
+983412448546,
Email: arsaied@kmu.ac.ir
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Abstract
Introduction: The
lack of a Palmaris longus tendon and the
absence of a fifth superficial flexor
function are normal variations found in
the human wrist and hand. The purpose
of our study was to assess the incidence
of both of these variations and also to
answer the question of whether they are
evolutionarily conserved muscles.
Methods: The
study population was volunteers (or informed
consent from parents) from preschools,
grammar schools, high schools and universities,
offices, and nursing homes who were examined
for the presence of the Palmaris longus
tendon and for variations of the fifth
superficial flexor.
Results:
By the end of the study, 1180 individuals
were enrolled and their data were recorded.
Of the total 2,360 hands studied, 1,688
had a Palmaris longus tendon (71.4%) and
1,284 had a functional fifth superficial
flexor (54.4%). In 886 hands fourth flexor-dependent
function was found (37.5%) and ultimately
in 190 (8%) the function was absent.
Presence, dependent
function, or absence of fifth flexor or
Palmaris was not related to age, hand
side or dominance. Fifth flexor variations
were not related to sex, but unilateral
absence of Palmaris longus was 1.5 times
more common in women. No difference was
found between the sexes regarding variations
of the superficial flexor. No correlation
was found among the variations between
one tendon and the other within one hand
and/or that individual’s other hand.
Conclusion:
The findings of the present study
are similar to those found in some other
similar reports related to variations
in these tendons. It seems that Palmaris
longus and the fifth superficial flexor
function are not evolutionarily determined,
at least in the studied population.
Key words:
Palmaris longus, fifth superficial flexor,
variation, evolution.
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The Palmaris longus is one of the most variable
muscles of the body and may be absent in some
individuals (1). The fifth superficial flexor
of fifth finger is also among the variations
of the human body, and in some individuals it
is not detectable or not present. This claim
is controversial: some studies have concluded
that this tendon is absent in certain individuals
(2, 3) while others have concluded that the
absence is functional rather than anatomical
(4). Both of these tendons have been considered
to have evolved (5). In the present study our
main purpose was to assess the frequency of
these variations in relation to an Iranian sample
population and to answer the question of whether
they are evolutionarily determined.
This prospective study was performed on a
population comprised of volunteers from preschools,
primary schools, high schools, universities,
offices and nursing homes in the city of Kerman,
Kerman province, Iran. Institutional ethics
committee permission was granted. In each case,
if informed consent was given by the individual,
s/he was examined by an examiner trained for
that purpose. At first the classic test for
the presence of Palmaris was performed, in which
the individual would place his or her fifth
and first fingers in opposition to each other
while flexing the wrist. If the Palmaris longus
tendon was visually detected and palpated, the
individual was assumed to possess the tendon
(6). If this visual examination and palpation
test was negative, then the other tests were
performed to confirm the absence of the tendon,
and if the results were negative for all tests,
the individual was assumed to be without the
tendon. Contradictory or suspicious cases were
excluded from the study.
The fifth superficial flexor was assessed by
asking the volunteer to flex the Proximal interphalangeal
joint (PIP) at least 90 degrees while the examiner
kept the second, third, and fourth fingers fully
extended. The individual was considered to have
a functional Flexor Digitorum Superficialis
(FDS), if s/he could. If the test result was
negative, then the examiner would release the
fourth finger and repeat the examination. If
this time the PIP was bent to 90 degrees, it
was a dependent tendon, and if not, the individual
had a nonfunctional or completely deficient
fifth FDS (4).
By the end of the study, 1,180 individuals
and thus 2,360 hands were enrolled, comprising
433 males and 747 females. The mean age of the
individuals was 26.64±17.94, with a range
of 5 to 91. 1,132 individuals were right-handed
(95.9%), 414 men and 718 women.
The Palmaris Longus tendon was present bilaterally
in 730 (62%) and absent bilaterally in 222 (19%).
In 228 individuals the tendon was present on
one side, 101 in the right hand and 117 in the
left. Of the total 2,360 hands, the tendon was
present in 1,688 (71.4%) and absent in 672 (28.6%).
Of the male hands studied, 679 (78.4%) possessed
the tendon and in women’s hands, the tendon
was present in 1,005 (67.3%). Of the right hands
studied, 831 (70.5%) possessed the tendon, and
of the left hands, the tendon was found in 853
(72.2%). Of the total dominant hands, 1,624
of 2,264 dominant right hands (71.7%) and 65
of 96 dominant left hands (67.5%) featured the
Palmaris longus tendon. These results are shown
in Table 1.
480 individuals had functional FDS bilaterally
(40.4%); in 273 individuals it was dependent
on the fourth FDS bilaterally (23.2%), and in
32 individuals the fifth FDS was bilaterally
nonfunctional (2.7%). Of the remaining 391 individuals,
in 134 the right hand had a dependent and the
left a functional FDS; in 135, the left side
had a dependent tendon and the right a functional
one; in 33, the right had a functional and the
left a nonfunctional tendon; and ultimately,
in 24 the left was dependent and right was nonfunctional
(Table 2). Of the total 2,360 hands, 1,284 had
functional FDS (54.4%), 886 had dependent FDS
(37.5%) and 190 had nonfunctional FDS (8%).
Table 3 shows FDS incidence in dominant hands.
Twenty-three right and 31 left hands had neither
the Palmaris longus nor fifth flexor tendon.
Twenty-three individuals had absent Palmaris
and nonfunctional flexors bilaterally.
The results were analyzed with a generalized
estimation equation and the conclusion was reached
that the variations in the Palmaris longus and
the fifth superficial flexor tendons’ presence
or absence were not related to age, side, or
dominance. The fifth FDS variations were not
affected by sex, but bilateral lack of Palmaris
longus was 1.8 times more frequent in females,
while there was no difference between the sexes
with regard to the unilateral absence or presence
of Palmaris. Again there were no correlations
among the variations of Palmaris and the fifth
flexor tendon.
Table 1: Palmaris longus situation regarding
side and sex (p>0.05 in all)
Table 2: Palmaris longus situation regarding
bilateral absence or presence
Table 3: Fifth FDS situation regarding side
and sex (p>0.05 in all)
Table 4: Fifth FDS situation regarding dominant
side
In
the
present
study
we
assessed
the
variations
in
the
Palmaris
longus
and
the
fifth
superficial
flexor
in
an
Iranian
population,
and
also
considered
their
presence
or
absence
in
relation
to
age
and
to
each
other;
ultimately
we
found
no
correlations.
The
variations
in
Palmaris
longus
have
been
studied
extensively
in
different
populations
and
very
different
findings
have
been
reported,
from
the
absence
of
the
tendon
in
more
than
50%
(6)
to
its
presence
in
more
than
96%
(7).
In
one
study
of
an
Iranian
population,
the
23%
absence
of
the
Palmaris
longus
tendon
was
the
result
that
is
closest
to
ours
(8).
For
the
fifth
superficial
flexor
we
could
find
only
one
epidemiologic
study
with
results
comparable
to
ours:
about
6%
absolute
deficiency
and
40%
dependency
on
the
fourth
flexor.
Another
study
found
an
absence
of
the
tendon
in
33%
of
the
population,
which
is
a
lower
incidence
than
in
our
findings
(10).
As
previously
reported,
Palmaris
and
fifth
FDS
are
commonly
considered
evolutionary
developments,
disappearing
with
time
over
generations.
This
hypothesis
has
been
examined
in
a
study
on
an
African
population
by
assessing
the
difference
of
variations
in
different
age
groups
and
it
was
concluded
that
no
obvious
evolutionary
trend
was
present
(11).
Another
study
with
the
same
method
reached
the
conclusion
that
the
tendon
was
evolutionarily
determined
(12).
Our
study
assessed
variations
in
the
detection
of
these
tendons
with
age,
which
we
think
is
statistically
more
meaningful.
We
could
not
find
any
study
that
assessed
an
evolutionary
trend
for
FDS.
Are
the
variations
affected
by
the
dominance
of
the
hand?
To
the
best
of
our
knowledge
only
one
study
has
tried
to
address
this
topic
directly,
and
only
regarding
Palmaris
longus.
It
concluded
that
the
nondominant
hand
had
a
higher
incidence
of
an
absent
Palmaris
longus
(13).
Another
study
noticed
this
too,
but
not
as
its
primary
conclusion,
and
it
noted
that
Palmaris
was
more
frequently
absent
in
the
left-dominant
hand
(8).
Again,
we
used
the
relation
instead
of
difference
and
did
not
find
a
correlation,
either
for
Palmaris
or
for
the
flexor.
Our
findings
for
flexor
independence
in
relation
to
sex,
age,
and
dominance
are
comparable
to
at
least
one
previous
study
(14).
Another
point
to
be
noted
is
the
correlation
among
variations
in
the
tendons,
as
they
have
a
common
origin
from
the
medial
epicondyle
and
similar
innervations.
So,
it
may
seem
logical
that
variations
are
found
together
or
at
least
that
there
is
a
relationship.
To
our
knowledge,
only
one
study
has
been
performed
to
answer
this
question
and
has
found
no
correlation
(15).
It
considered
the
absence
of
presence
(functional,
non-functional)
of
the
tendon,
in
contrast
to
the
present
study
in
which
dependency
on
the
fourth
flexor
was
considered
too,
though
the
result
was
similar
as
no
correlation
was
found.
Studies
of
Palmaris
longus
variations
and
their
relationship
with
sex
have
reached
different
conclusions.
In
some,
the
absence
of
these
tendons
has
been
reported
more
frequently
in
females
(16,
17,
and
18).
In
others,
no
difference
was
reported
(19
and
20)
and
at
least
one
study
found
more
frequent
absence
of
the
tendons
in
men
(21).
It
is
interesting
to
note
the
finding
of
a
more
frequent
bilateral
absence
in
women,
and
the
equal
incidence
of
a
unilateral
absence
in
men
and
women
(22).
The
last
point
is
the
fact
that
different
statistics
about
variations
in
Palmaris
longus
are
related
to
the
studied
race
and
location,
but
is
it
possible
that
different
observers
have
different
interpretations
of
a
test
on
a
single
person?
To
the
best
of
our
knowledge
no
study
has
noted
the
interobserver
and
interobserver
reliability
of
different
tests
performed
for
assessing
these
variations
and
this
may
be
a
good
topic
for
further
research.
At
least
one
study
observed
that
different
tests
may
give
different
results
in
one
person
(23),
at
least
in
relation
to
this
topic.
The
most
important
limitation
of
the
present
study
is
the
fact
that
due
to
several
considerations
we
included
a
larger
population
of
young
people
than
the
elderly;
the
most
obvious
was
their
availability.
The
very
sensitive
tests
that
we
used
for
statistical
analysis,
would
have
compensated
for
this,
but
of
course
not
completely.
Based
upon
the
findings
of
the
present
study,
it
seems
that
the
tendons
that
are
the
subject
of
this
paper,
at
least
in
the
population
studied,
are
not
evolutionary
and,
in
other
words,
are
not
related
to
age.
Acknowledgement
The
authors
desire
to
declare
their
attitude
towards
the
volunteers
who
made
this
investigation
possible
with
their
cooperation
and
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