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REVIEW ARTICLE
Tidsskr Nor Legeforen nr. 15, 2013; 133: 1591 – 5
1591
Review article
Treatment of congenital syndactyly
of the fingers
1591 – 5
Hebe Désirée Kvernmo
hebe.kvernmo@gmail.com
Section for Upper Extremity- and Microsurgery
Department of Orthopaedics
Oslo University Hospital
Jan-Ragnar Haugstvedt
Department of Orthopaedics
Østfold Hospital, Moss
MAIN POINTS
Syndactyly should be assessed during the
examination of the newborn baby and noted
on the birth report which is sent to the Medi-
cal Birth Registry
The child must be referred to a department
with expertise in hand surgery as well as to
the paediatric department and for genetic
testing in case of associated conditions
and anomalies
Proper attention paid to the parents and
thorough information about the treatment
are necessary to ensure a good result
Treatment of syndactyly is a reconstructive
procedure, but safe separation should be
expected with proper independent function-
ing of the fingers
BACKGROUND Syndactyly or webbed fingers is one of the most common congenital mal-
formations of the upper extremities, but it comprises few new cases annually. The purpose
of treatment is to enhance hand function.
METHOD The article is based on current text books and literature searches in PubMed as
well as the authors’ clinical experience within this field.
RESULTS The purpose of surgical treatment is to separate the fingers and reconstruct a
webspace. It is difficult to indicate exact treatment results because of large variations in the
extent of the deformity. For syndactyly involving only soft tissue (simple syndactyly), a good
functional result is achieved with a less than 10 % risk of complications. Syndactyly where
also the bones have fused (complex syndactyly) or where there is additional bone formation
between two digital rays (complicated syndactyly), gives a poorer functional outcome and
a higher risk of complications. Gradual stretching of the tissue using a distraction device
enables separation of fingers one was previously reluctant to separate.
INTERPRETATION It should be possible to expect safe separation with a good and indepen-
dent function of the fingers with surgical treatment. The parents should be informed that the
surgical treatment is a reconstructive procedure that may require secondary corrections.
The term syndactyly derives from the Greek
syn (together), and daktylos (finger), and
refers to the clinical appearance of fingers
which have not undergone a normal process
of separation in intrauterine life. There is a
large degree of heterogeneity in the extent of
the malformation, which may have functional,
developmental and cosmetic implications (1,
2). In this article we wish to give an overview
of the condition and how to deal with it.
Method
This article is based on current text books,
participation at international conferences, the
authors’ clinical experience within this field
as well as articles found through a selective
literature search in PubMed using the MESH
terms (syndactyly/surgery* OR syndactyly/
methods*). The selection was restricted to
long-term results of surgical treatment pub-
lished in English-language journals in the
period from 2000 until the search date 18.12.
2012. The articles dealing with results of sur-
gery were all based on simple case series
without randomisation or blinding.
Epidemiology
The Danish registry of congenital malforma-
tions showed an incidence of malformations
of the upper extremities for the period
1984 – 93 of 14.6 per 10 000 live births (3).
The incidence of syndactyly was 2.8 per
10 000. Data from England and Wales, by
comparison, show that syndactyly occurs in
one in every 2 400 live births (4). The condi-
tion represents approximately 20 % of all mal-
formations of the hand (3, 5) and occurs twice
as frequently in boys. 50 % of syndactylies are
bilateral, and bilateral, simple syndactyly
between the long finger and ring finger is most
frequent. Involvement of the thumb and index
finger, or the index finger and long finger is
least frequent (6, 7), except when related to a
syndrome (6). Figure 1 illustrates which
webspace is involved (8). Complex syndac-
tyly represents only 16.5 % of the cases (5).
Classification
The classification of syndactyly is shown in
Figure 2. The term simple syndactyly is used
if only the soft tissues are involved, and
complex syndactyly if the bones of adjacent
fingers are fused (synostosis) (1). The term
incomplete syndactyly is used to describe a
fusion that is proximal to the distal phalanx
and complete if the syndactyly continues up
to the distal phalanx. The term complicated
syndactyly describes syndactyly with bone
formation between two digital rays (hidden
polydactyly), and acrosyndactyly describes
syndactyly involving the distal phalanges,
however with a proximal webspace.
Classification and aetiology
The development of the hand starts on day 27
of intrauterine life (9, 10). The fingers are
normally separated between day 44 – 46.
Most syndactylies appear in this period and
can be attributed to errors in programmed
cell death (apoptosis), which normally invo-
lutes the embryonic interdigital tissue and
enables the formation of separate fingers (1,
10). This tissue normally involutes from dis-
tal to proximal and explains the phenomenon
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Tidsskr Nor Legeforen nr. 15, 2013; 133
REVIEW ARTICLE
of simple incomplete syndactyly. The excep-
tion to the rule is acrosyndactyly, where the
most common form is associated with amni-
otic band syndrome, which causes fingers to
fuse after the separation process is completed
(1). Differentiation of other organ systems
proceeds in parallel with that of the hand,
which explains associated anomalies in a
number of syndactylies (2, 10). In 1976 the
International Federation of Societies for Sur-
gery of the Hand introduced a classification
system according to which congenital mal-
formations of the upper extremities are clas-
sified into seven categories (11). Syndactyly
is placed in group II together with other fai-
lures in differentiation.
The majority of syndactylies occur isola-
ted and with unknown cause. Factors that
may have affected the intrauterine environ-
ment, such as exposure to teratogenic agents,
virus infections or other diseases in early
pregnancy, are postulated as possible causal
hypotheses (2). 10 – 40 % of the cases have a
positive family history (1, 2, 12). When syn-
dactyly occurs isolated and there is a positive
family history, the syndactyly has always an
autosomal dominant inheritance (1). It is
often both complex and complicated. How-
ever, the dominant gene shows reduced
penetrance and variable expressivity, so that
the condition varies greatly from one gener-
ation to the next (1). Syndactyly is moreover
a feature of at least 28 syndromes. The most
common are Apert syndrome, Poland syn-
drome, amniotic band syndrome and multi-
ple craniofacial syndromes (1). Only 5 % of
all malformations of the upper extremities
are part of a defined syndrome (2).
General examination of newborns
When a child with syndactyly is seen, it
must be remembered that other simul-
taneous malformations can occur due to
chronological proximity to the intrauterine
development of the hand (2, 10). The simple
syndactylies are not, however, associated
with other congenital malformations (2) and
do not require further investigation than the
normal assessment during the examination
of the newborn baby. If it is the complex
form and it is not inherited, discretion is
exercised. In most cases fusion of the bones
of two adjacent fingers will not entail further
investigation apart from carrying out a clin-
ical examination of the upper extremities,
feet, head /face and thorax. If associated
conditions are suspected, or the syndactyly
is related to a syndrome, the child is referred
to a paediatric department and to geneticists
who assist in further investigation.
It is important to remember that all con-
genital malformations that are discovered at
the maternity or neonatal unit are notifiable
to the Medical Birth Registry. Mandatory
Figure 1 Schematic representation of involved web spaces (8)
Figure 2 Classification of syndactyly. Syndactyly between long and ring finger. a) Simple incomplete syndactyly
b) Simple complete syndactyly c) Complex complete syndactyly d) Complicated syndactyly
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1593
notification also applies to the less extensive
conditions, such as simple incomplete syn-
dactyly. When the diagnosis is unclear and
the child is referred for further investigation,
it is important to note this on the birth report.
This enables the Medical Birth Registry to
follow up on the diagnosis, resulting in as
correct registry data as possible. Registry
data based on an accurate medical history
may also potentially help to reveal causal
factors for a number of syndactylies.
The child should have an early referral to
a department with expertise in hand surgery,
out of regard for the parents’ need for infor-
mation, and planning and possible need for
coordination of the further treatment.
The assessment for hand surgery
Clinical examination provides an overview
of the extent of involved fingers. Closer
clinical examination will make it possible to
distinguish between simple, complex and
complicated syndactyly. The presence of an
active range of motion in the interphalangeal
joints with well-defined flexion and exten-
sion creases indicates normal joint anatomy
and simple syndactyly. If there are no fle-
xion and extension creases and the joints are
not mobile, complex or complicated syndac-
tyly must be suspected. Lack of movement
between the distal phalanges of two digital
rays and fused nails indicate synostosis. In
syndactyly associated with other clinical
syndromes such as Poland syndrome, Apert
syndrome or amniotic band syndrome, clin-
ical examination of the upper extremities,
feet, head/face and thorax is needed.
Plain X-ray examination of the affected
hand should always be included in the pri-
mary assessment to reveal any synostoses,
hidden polydactylies or other skeletal defor-
mities, and is particularly important in com-
plex syndactylies.
Assessment for surgical treatment
Surgery is recommended for most children
(1, 8, 12 – 14). The purpose of treatment is to
enhance the functional level. Emphasis is
placed on the cosmetic aspect and the child’s
natural ability to adapt to the malformation.
Separation of fingers is contraindicated if it
can be seen that this could reduce existing
functional level, for example if components
of the fused fingers are missing, which
makes it impossible to create independent,
stable and mobile fingers (13). Medical con-
ditions may likewise be a contraindication
for surgery. Mild, incomplete syndactyly
without functional limitations is only a rela-
tive indication for surgery.
Timing of surgery
While there are few controversies with
regard to the indication for surgery, the
timing of surgery is to some extent discre-
tionary. The question to be asked is not how
early the procedure can be carried out, but
rather how long it can be postponed based on
the functional needs of the hand. (1). The
timing is assessed for individual cases and
depends on which fingers are involved, as
well as the extent and complexity. Likewise
there may be other malformations which
must be dealt with before the surgical treat-
ment of the hand. When several procedures
are required, these should be carried out
before the child reaches school age.
Generally it can be said that simple syn-
dactyly of the web between second and third
fingers can safely be separated at the age of
1 – 2 years (1, 8, 12). Surgery on a larger
hand reduces the risk of scar contracture and
development of web creep, where the web-
bing creeps distally as the hand grows.
For syndactylies of the first and fourth
interdigital webs and syndactylies with
fusions of several fingers, surgery is recom-
mended at the age of 4 – 9 months (1, 8, 12,
15). The ability to locate the hand in space
and perform grip and pinch manoeuvres are
cortical functions that develop before the
age of one year. Coordination continues to
develop until the age of three years (16).
Early surgery thus provides optimal assu-
rance of a normal grip development. In
addition, optimal normal development of the
skeleton and muscles is ensured.
Information to the parents
It is important to establish a relationship of
trust with the parents. This requires time and
qualified answers to their questions and con-
cerns about what can be achieved through sur-
gery, as well as an exact account of the entire
course of treatment. It is important to highlight
the fact that it is not always possible to create a
normal-looking hand, and that the main pur-
pose of surgery is to raise the child’s functional
Figure 3 Example of a plasty for separation of syndactyly between the long and ring finger. a) Planning sketch
from the volar and dorsal aspect, where a dorsal rectangular flap for the web spaces and transposition flaps
extending to the fingers are sketched. b) Planning sketch of distal phalanges with transverse pulp flaps and
drawing in which these are sutured in place
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REVIEW ARTICLE
level. The parents should be informed that sev-
eral operations may be necessary to separate
several fused fingers. The parents may have
problems in understanding that the operation is
not a simple separation of two fingers, but a
reconstructive procedure which also involves
the need for skin grafting. Children should be
monitored until they have ceased to grow so
that the development of web creep and scar
contracture extending to the finger can be cor-
rected before the child develops deformities.
Several of our university clinics have
cross-disciplinary «dysmelia teams» consis-
ting of a hand surgeon, an occupational
therapist and an orthopaedic engineer to deal
with the more complex conditions. The
teams take care to provide information, and
moreover parents and children can meet
other children with the same or similar con-
ditions, as well as their parents. In this way
the coping aspect is also safeguarded.
Surgery
Each stage of the surgical procedure is
designed to minimise the risk of complica-
tions. Surgery is performed under general
anaesthetic with bloodless field and use of
magnifying loupes, and microsurgical instru-
ments must be available. If the condition is
bilateral, the procedure is often carried out
on both hands simultaneously. The various
techniques for separation of fused fingers
are largely based on the same principles.
Both sides of a finger should not be operated
in one procedure, as this can compromise
circulation (1, 2, 12). An example of separa-
tion of a syndactyly is shown in Figure 3a.
The bloodless field is released after the flaps
are raised, and haemostasis is achieved
before the flaps are inserted into place with
absorbable sutures. Skin defects are covered
with full-thickness skin grafts, often harve-
sted from the groin. Use of split-thickness
skin grafts is avoided, since these can shrink
up to 50 % and thereby entail scar contrac-
tures (13). In syndactyly extending to the
distal phalanges, the lateral nailfold is recon-
structed with transverse fingerpulp flaps
(Figure 3b) (14, 17).
If all the fingers are fused, the thumb and
index finger, and the long and ring finger are
separated during the first operation. During
the second operation, normally 4 – 6 months
later, the index finger and long finger, and
the ring finger and small finger are separated
(12, 15).
In case of syndactyly in children with
Apert syndrome, it may be beneficial to
cover the first web space with a rotational
flap from the dorsal hand (1, 14, 15). With
extensive syndactylies of this type, tissue
distraction may be performed using an
external distraction device (Cube fix distrac-
tor, developed by Rolf Habenicht at the
Catholic Children’s Hospital Wilhelmstift in
Hamburg) before separating the last two fin-
gers (long and ring fingers) (Figure 4) (18,
19). The device is referred to as the «magic
cube» at Oslo University Hospital, since the
distraction results in «extra» skin that makes
subsequent separation easier.
Results of treatment
It is difficult to provide accurate data on
treatment results, due to the heterogeneity of
the condition, the many surgical techniques
and the few long-term results published.
In simple syndactylies a good functional
and cosmetic result is achieved (12, 20 – 22).
However, a need for secondary procedures
is reported in approximately 10 % of cases
(12). Development of web creep occurred in
two of 26 interdigital web spaces with the
full-skin transplant technique after an 18-
year follow-up period. (21). For the skin
graft-free technique, long-term results after
more than ten years’ follow-up show a
somewhat higher occurrence of the develop-
ment of web creep (22).
Goldfarb et al. (23) demonstrated good
range of motion following the separation of
complex syndactyly between the long and
ring finger or between the ring and small fin-
ger. However, rotational and axial deviation
of the fingers, and nail deformity with inade-
quate lateral nail-folds were found on most
of the fingers. The study is supported by
Vekris et al. (24), who found that complex
and complicated syndactylies, together with
delayed separation, give poorer results. In a
study of Apert syndrome without use of dis-
traction, acceptable functional results were
found (25). All the patients required correc-
tive procedures, but taking into account the
complexity of the condition, the need for
revisions was considered acceptable.
There are good results from using the
«magic cube» to separate the last two fingers
(18, 19). The creation of a «five-fingered»
hand was achieved, with the long and ring
fingers having an appearance corresponding
to the other separated fingers. Of eight syn-
dactyly operations (19) there were two
minor infections which were treated with
antibiotics, and one infection following
completion of distraction, in which the
distraction device had to be removed. In this
instance the surgery for syndactyly was
postponed for three weeks. In one case the
separated synostosis fused together again
during distraction and had to be reoperated.
The most frequent postoperative compli-
cations related to syndactyly surgery are
infection and maceration of the graft or flap
which can result in their loss. Loss of fingers
is rare, but is described in the literature (12).
Final comments
We present an overview of important prin-
ciples in the care of children with syndac-
tyly, where the main indication for surgery is
to improve the functional level of the hand.
Despite the fact that syndactyly is one of the
most common congenital malformations of
the upper extremities, the knowledge base is
limited, since the condition is heterogenous
and affects few patients. We present treat-
ment results based on simple case series
without randomisation. The studies con-
clude that safe separation of the fingers can
be expected, and that these will function
well independently. The treatment result is
optimal for the least extensive conditions.
For children with associated conditions and
anomalies, it is favourable that the place of
treatment should have all the necessary spe-
cialists. It is important that the parents are
thoroughly informed. The parents’ under-
standing of the course of treatment, and
acceptance of what results can be expected,
Figure 4 Tissue expansion using external distrac-
tion device («magic cube») in a patient with complex
syndactyly. Photograph of volar aspect of right hand in
a patient with Apert syndrome who has had separation
of complex syndactyly between all the fingers except
between long and ring finger. a) Photograph following
removal of «magic cube». b) Photograph of volar
aspect after approximately one year following separa-
tion of long and ring finger
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1595
are necessary to enable the child to cope
with the condition.
Hebe Désirée Kvernmo (born 1961)
is a specialist in hand and orthopaedic surgery,
Dr. med. and MHA. She is a senior consultant
and President of the Norwegian Society for
Surgery of the Hand.
The author has completed the ICMJE form
and declares no conflicts of interest.
Jan-Ragnar Haugstvedt (born 1954)
is a specialist in general and orthopaedic sur-
gery, and hand surgery. He completed his PhD
after a research residency at the Mayo Clinic.
He is a senior consultant and board member of
the Norwegian Society for Surgery of the Hand,
and deputy secretary general of the European
Wrist Arthroscopy Society.
The author has completed the ICMJE form
and declares no conflicts of interest.
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Received 1 February 2013, first revision submitted
24 March 2013, approved 13 May 2013. Medical
editor Trine B. Haugen.
