Keywords
Free tissue flap - Soft tissue injury - Finger injury - Reconstructive surgery
INTRODUCTION
Patients who present with degloving injuries to the hands or amputation of two or
more digits are rare. Replantation is ideal but often impossible or unsuccessful.
Without proper vascular tissue transplantation, necrosis of the amputated or denuded
area is imminent [1]
[2]
[3]
[4]. The advent of microsurgery has led to the introduction of fascial free flaps, innervated
fasciocutaneous flaps, and arterialized venous flaps for reconstruction [5]
[6]
[7]
[8]. These options are ideal for the reconstruction of soft tissue defects in the hand
according to the size, shape, and site of each defect. Single free flaps are a reconstructive
method commonly used in our institution to address the challenges encountered in degloved
or amputated stumps of multiple digits. Various free flap types have been performed
using various donor regions, from the upper extremities to the lower extremities.
However, this procedure requires secondary division and setting.
Despite evidence that sufficient neovascularization to sustain the flap develops before
3 weeks, reconstructive surgeons have been advised to wait 3 weeks before attempting
flap division [9]. Although we also planned flap division after 3 weeks, there were cases in which
flap division was performed later due to concerns about necrosis. The timing of flap
division after 3 weeks is common practice, but we had questions about whether this
should be applied equally to various types of flaps. Division at 3 weeks is more difficult
for large and thick flaps than for small flaps. The aim of this study was to analyze
flap divisions of various types and to determine the relationship between the size
of the flap, the timing of separation surgery, and the degree of necrosis.
METHODS
Patients
This was a retrospective review of patients who underwent simultaneous free flap reconstruction
of multiple soft tissue defects in the hand between 2011 and 2020 at our institution.
The need for patient consent was waived due to the retrospective nature of the study,
and the study design was approved by the institutional review board (IRB No. KIRB-2021-N-002).
Cases of single free flaps performed across multiple digits for soft tissue reconstruction
between 2011 and 2020 were investigated, including both primary and secondary operations.
Various types of flaps from the upper extremity to the lower extremity were performed
based on the location and the number of digits with tissue defects. The flap option
was chosen after sufficient discussion with the patient about donor site mobility
and cosmetics.
Flap types and operative techniques
Lateral arm free flap (fasciocutaneous or fascial type)
This flap contains the posterior radial collateral artery and is elevated with one
dominant perforator artery and one or two venae comitantes on the lateral aspect of
the upper arm. This flap may include the posterior brachial cutaneous nerve for sensation
and is anastomosed to the digital artery, nerve, and subcutaneous veins.
Venous forearm free flap
This flap is harvested from the anterior portion of the ipsilateral forearm, which
contains three to four veins. The flap was elevated with one afferent vein and several
efferent veins. The afferent vein of the flap was anastomosed to the digital artery
and the draining veins were anastomosed to the dorsal veins. The flap is arterialized
with arterial inflow and venous outflow (A-V-V type).
Thenar free flap
This flap is designed from the thenar crease to the wrist crease, centering on the
scaphoid tubercle. The flap is elevated with the superficial palmar branch of the
radial artery to the skin and is elevated with one perforator and one or two venae
comitantes. The perforator artery is anastomosed to the digital artery and the draining
vein is sutured to the subcutaneous vein.
Hypothenar free flap
This flap is designed from the hypothenar eminence to ulnar and dorsal skin. The flap
is elevated with one perforator artery that arises from the fourth common palmar digital
artery and one subcutaneous vein, and is anastomosed to the digital artery and recipient
subcutaneous vein. If complete coverage of the defect by the flap is unfeasible, a
skin graft near the flap donor site at the hypothenar eminence is harvested [10].
Anterolateral thigh free flap (fasciocutaneous or fascial type)
This flap contains the descending branch of the lateral femoral circumflex artery
and is elevated with one dominant perforator artery and one or two venae comitantes.
In addition, the lateral femoral cutaneous nerve is included in the flap. The flap
is anastomosed to the digital artery, nerve, and subcutaneous veins.
Medial plantar free flap
This flap is designed on the medial aspect of the ipsilateral plantar arch flap. It
is harvested with the medial plantar perforator artery and nerve and is anastomosed
to the digital artery and nerve. Several subcutaneous veins of the flap are sutured
to the subcutaneous veins of the digits.
Second partial toe pulp free flap
This flap is designed on the medial side of the ipsilateral second toe pulp area.
The plantar digital artery and paired nerve are elevated with several venae comitantes.
The flap is anastomosed to the recipient digital artery and nerve of the injured digit.
The draining veins of the flap are sutured to the subcutaneous veins of the digit.
Division of the flap
After free flap surgery, the circulation of the flap was closely monitored by measuring
the capillary refill time and flap surface temperature, and the patency of the anastomosed
artery was checked using a hand-held Doppler. The color change and necrosis of the
flap margins were evaluated. As anticoagulant therapy, 12,000 U of heparin was administered
along with 10 μg of prostaglandin E1 for 1 week. In cases of syndactyly due to the
flap, active and passive joint exercises of the metacarpophalangeal or proximal interphalangeal
joint were started at the first postoperative week.
Flap division was planned after at least 3 weeks, which is the standard time used
by many surgeons to safely allow neovascularization [9]. During flap monitoring, a capillary refill test was performed and changes in the
flap end were measured to determine the timing of flap division surgery. For some
small and thin flaps, the timing of flap division was decided by using clamping to
check the blood circulation of the flap. Immediately after division of the flap during
surgery, the capillary refill time of the divided flap was checked. If additional
skin coverage was required during flap division surgery, such as in the web space
or joint space, then a skin graft or local flap was performed using Z-plasty to prevent
contracture. After surgery, the color change and necrosis of the flap margins were
evaluated. In some cases that involved three or more digits, flap division was performed
in two steps and the second step flap division operation was performed at least 2
weeks after the first division operation.
The patients’ demographics, flap type, diameter of the flap, number of anastomosed
vessels, frequency of complications (e.g., infection, hematoma, and emergent re-exploration),
timing of flap division surgery, and degree of flap necrosis were retrospectively
investigated by evaluating their medical records and photographs. The continuous variables
between the two groups in this study (the large flap group and the medium or small
flap group) were compared using the t-test. In the interpretation of results, P-values
< 0.05 were considered to indicate statistical significance. All statistical analyses
were performed using SPSS version 28.0 (IBM Corp., Armonk, NY, USA).
RESULTS
In total, 75 patients were included in the analysis ([Table 1]). The success rate was approximately 97% (73/75), and only two cases of flap failure
occurred. These two patients underwent a secondary groin flap and skin graft. The
incidence of partial flap necrosis was 15% (11/75) and did not involve more than 30%
of the total area in any patient. Re-exploration was performed in 7% of patients (5/75).
The mean age was 42.9 years (range, 19–64 years), and 68 patients were men and seven
patients were women. Industrial accidents accounted for 91% of cases (68/75). In total,
4% of cases (3/75) were from a degloving injury due to a traffic accident, 4% of cases
(3/75) were from necrosis due to thermal burns, and one case of skin cancer was included.
Primary reconstruction was performed in 61.3% of cases (46/75), and secondary reconstruction
due to necrosis after replantation of amputated fingers or composite grafting of degloving
soft tissue accounted for 28.7% of cases.
Table 1.
Incidence of complications by flap type
|
Type of free flap
|
No.
|
Partial loss, No. (%)
|
Flap failure, No. (%)
|
Re-exploration, No. (%)
|
|
Lateral arm free flap (fasciocutaneous type)
|
4
|
0
|
0
|
0
|
|
Lateral arm free flap (fascial type)
|
4
|
0
|
0
|
0
|
|
Venous forearm free flap
|
2
|
0
|
0
|
0
|
|
Thenar free flap
|
15
|
1 (7)
|
0
|
1 (7)
|
|
Hypothenar free flap
|
3
|
1 (33)
|
0
|
0
|
|
Anterolateral thigh free flap (fasciocutaneous type)
|
37
|
7 (19)
|
2 (5)
|
4 (11)
|
|
Anterolateral thigh free flap (fascial type)
|
7
|
1 (14)
|
0
|
0
|
|
Medial plantar free flap
|
1
|
1 (100)
|
0
|
0
|
|
Partial second toe pulp free flap
|
1
|
0
|
0
|
0
|
|
Total
|
75
|
11 (15)
|
2 (3)
|
5 (7)
|
The injury location was classified as the amputation stump, dorsum of the digit, and
volar aspect of the digit ([Table 2]). There were 35 cases of resurfacing two digits and 38 cases of soft tissue defects
in three or more digits. An anterolateral thigh free flap was used in 12 cases of
resurfacing two digits and in 30 cases of injury to three or more digits ([Fig. 1]). In three patients, this flap was used for all five amputation stumps. A lateral
arm free flap was used in five cases of resurfacing two amputation stumps and the
dorsal sides of two digits and in three cases of injury with three amputation stumps.
A venous forearm free flap was used in two cases of a degloving injury to the dorsal
side of two digits. Thenar free flaps were used in 10 cases of resurfacing two amputation
stumps and in three cases of injury with three amputation stumps. Three cases involved
resurfacing the volar and dorsal sides of two digits. A hypothenar free flap was used
in two degloving injury cases for the dorsal side of two digits and, in one case,
three digits. A medial plantar free flap and second partial toe pulp free flap were
used in one case of injury to the amputation stumps of three digits and in one case
of injury to the pulp of two digits.
Table 2.
Indication of flap types according to recipient site
|
Recipient sites
|
Flap types (No.)
|
Anterolateral thigh free flapa)
|
Lateral arm free flapb)
|
Venous forearm free flap
|
Thenar free flap
|
Medial plantar free flap
|
Hypo-thenar free flap
|
Partial second toe pulp free flap
|
|
Y, indicates that a flap was used; N, indicates that a flap was not used.
a) Anterolateral thigh free flap included both fasciocutaneous type and fascial type;
b) Lateral arm free flap included both fasciocutaneous type and fascial type.
|
|
Two digits (n = 35)
|
|
|
|
|
|
|
|
|
|
Amputation stumps
|
Y (6)
|
Y (4)
|
N
|
Y (10)
|
N
|
N
|
N
|
|
Dorsal side
|
Y (3)
|
Y (1)
|
Y (2)
|
Y (1)
|
N
|
Y (2)
|
N
|
|
Volar side
|
Y (3)
|
N
|
N
|
Y (2)
|
N
|
N
|
Y (1)
|
|
Three or more digits (n = 38)
|
|
|
|
|
|
|
|
|
Amputation stumps
|
Y (25)
|
Y (3)
|
N
|
Y (3)
|
Y (1)
|
N
|
N
|
|
Dorsal side
|
Y (4)
|
N
|
N
|
N
|
N
|
Y (1)
|
N
|
|
Volar side
|
Y (1)
|
N
|
N
|
N
|
N
|
N
|
N
|
Fig. 1. Case of anterolateral thigh free flap. (A) A 27-year-old male patient has injured
in a car accident with degloving injuries of adjacent three digits. After debridement
of contaminated tissue, the digits were amputated at the proximal interphalangeal
joint. (B) A 15×7 cm fasciocutaneous flap, which contained one perforator artery,
two venae comitantes, and one cutaneous nerve, was harvested. Each artery and nerve
were anastomosed to the ulnar digital arteries and nerve of the long finger. The draining
veins were sutured to the dorsal vein of the long finger and volar vein of the small
fingers. (C) A single flap division was performed 24 days after the first surgery.
(D) At the 15-month follow-up, the divided flaps survived completely without the need
for additional surgery.
Based on the flap size, patients were classified into two groups: a large flap group
and a medium and small flap group ([Table 3]). The anterolateral thigh free flap (fasciocutaneous or fascial type) was considered
a large flap with a long axis mean diameter of > 10 cm. Flaps with a mean diameter
of > 6 cm were considered medium-sized flaps, including lateral arm free flaps, venous
forearm free flaps, thenar free flaps, and medial plantar free flaps. Flaps with a
mean diameter of < 6 cm were considered small flaps, including hypothenar free flaps
and second toe pulp free flaps. The mean numbers of anastomosed arteries and veins
in the large flap group were 1.09 and 1.81 (P = 0.265), respectively, and 1.03 and
1.55 (P = 0.166) in the medium and small flap group, respectively ([Table 4]).
Table 3.
Classification of flap types according to size
|
Flap type
|
No. of cases
|
Mean diameter (cm)
|
Range (cm)
|
|
Large
|
|
|
|
|
Anterolateral thigh (fasciocutaneous)
|
35
|
14.6 × 6.5
|
8 × 4–20 × 10
|
|
Anteriolateral thigh (fascial)
|
7
|
11.6 × 4.4
|
7 × 4–18 × 5
|
|
Medium and small
|
|
|
|
|
Lateral arm (fasciocutaneous)
|
4
|
7.5 × 3.3
|
7 × 2.5–8 × 4
|
|
Lateral arm (fascial)
|
4
|
6.3 × 3.3
|
4 × 3–10 × 4
|
|
Venous forearm
|
2
|
6.5 × 3.0
|
5 × 3–8 × 3
|
|
Thenar
|
15
|
6.2 × 2.2
|
5 × 1.5–11 × 3
|
|
Medial plantar
|
2
|
6.5 × 3.0
|
6 × 3–7 × 3
|
|
Hypothenar
|
3
|
3.5 × 2.0
|
2.5 × 1–4 × 3
|
|
Second toe pulp
|
1
|
3.0 × 1.0
|
3.0 × 1.0
|
Table 4.
Comparison of flap type and the number of anastomosed vessels
|
Flap size
|
No. of anastomosed vessels, mean ± SD
|
|
Arterya)
|
Veinb)
|
|
a) P=0.265 and b)P=0.166 as calculated using the t-test.
|
|
Large flap (n = 42)
|
1.09 ± 0.30
|
1.81 ± 0.80
|
|
Medium & small flap (n = 31)
|
1.03 ± 1.80
|
1.55 ± 0.77
|
In total, 73 patients underwent flap division surgery, which was performed at an average
of 47.17 days after initial flap surgery (range, 17–243 days) in the large flap group
and 42.81 days (range, 20–130 days) in the medium and small flap group ([Fig. 2]). This difference between the groups was not statistically significant (P = 0.596)
([Table 5]). The divided flaps had partial necrosis in 9.6% of cases (7/73), but most cases
were successfully divided after at least 17 days. The mean area of flap necrosis was
2.38% in the large flap group and 2.58% in the medium and small flap group (P = 0.935)
([Table 6]). Severe necrosis with an area of more than 50% of the divided flap developed in
one case of large flap division at 34 weeks and in one case of medium flap division
at 6 weeks.
Table 5.
Comparison of flap type and division timing
|
Flap size
|
Days after free flap
|
|
Mean ± SDa)
|
Range
|
|
a) P=0.596 as calculated using the t-test.
|
|
Large (n = 42)
|
47.16 ± 38.74
|
17–243
|
|
Medium & small (n = 31)
|
42.81 ± 27.92
|
20–130
|
Table 6.
Comparison of flap type and the mean necrosis area of the divided flaps
|
Flap size
|
Partial necrosis of divided flap (No.)
|
Area of necrosis (%), mean ± SDa)
|
|
Mild (< 10%)
|
Moderate (11%–50%)
|
Severe (> 51%)
|
|
a) P=0.935 as calculated using the t-test.
|
|
Large (n = 42)
|
2
|
1
|
1
|
2.38 ± 9.83
|
|
Medium & small (n = 31)
|
2
|
0
|
1
|
2.58 ± 10.94
|
Fig. 2. Comparison of the timing of flap division between the large and small or medium flap
groups.
DISCUSSION
In cases of degloving injuries to the hand, ischemia and necrosis of the denuded area
may be imminent without proper vascular tissue transplantation [1]
[2]
[3]
[4]. Importantly, the soft tissue envelope is necessary for blood supply to the distal
region. In cases involving amputation of two or more digits, replantation is ideal
but often impossible or unsuccessful. The reconstruction goals, in situations where
simultaneous coverage of multiple soft tissue defects in the hand is required, are
preservation of length, improvement of appearance, and restoration of function. Notably,
to achieve these results, adequate soft tissue coverage must be established, and distant
pedicled flaps from the groin and abdomen have been the preferred approach since the
1970s [5]. However, the advent of microsurgery has led to the introduction of fascial free
flaps, innervated fasciocutaneous flaps, and arterialized venous flaps as novel options
for reconstruction [6]
[7]
[8]
[9]. A single bridged free flap is a reconstructive method commonly used in our institution
to address the challenges encountered in cases of degloved or amputated stumps of
multiple digits. Importantly, it only requires the sacrifice of a single pedicle,
thereby generally minimizing operation time. In addition, circulation monitoring for
the flap is relatively simple and their harvest results in minimal single-donor site
morbidity.
In this study, various donor sites were used based on the size, shape, location, and
number of digits of the defect. Nine different types of flaps were used, which were
obtained from various regions, ranging from the upper extremities to the lower extremities.
Among them, the anterolateral thigh free flap (fasciocutaneous or fascial type) was
the most frequently utilized flap (59% of cases) because it can be used to cover two
to five digits of various sizes and was used for all dorsal, volar, and amputation-stump
defects. Compared to the other options, it provides adequate gliding of the underlying
tendon through stable and healthy soft tissue and can be used in a thin form [11]
[12]. The lateral arm free flap, which was also applied as the fasciocutaneous or the
fascial type, was primarily used to reconstruct the dorsal side, along with the venous
forearm free flap and hypothenar free flap. Importantly, the thenar free flap was
the most common medium-sized flap. A partial second toe pulp free flap was used to
treat a pulp defect in two fingertips. In addition to the upper and lower extremities,
other areas of the body can be used for hand reconstruction. For example, free tissue
options such as the latissimus dorsi can cover large areas, while the serratus flap
is effective for smaller defects. Furthermore, the temporal parietal flap is classically
used to cover the dorsal side of the hand due to its pliability, dependability, and
amenability to tendon excursion [13].
Notably, a single free flap performed over multiple digits requires secondary surgery
for flap division. However, in 1933, German et al. [14] found that flaps in dogs had matured sufficiently within 7 days to sustain pedicle
division. They examined the blood flow of the flaps and gained insight into the early
neovascularization that develops in transplanted tissue. They successfully divided
tubed flaps in patients at 10 days. In 1943, Douglas and Buchholz [15] further improved neovascularization of the distal portions of pedicle flaps, finding
that flap division was possible at 9–11 days in most instances. In a series of studies,
Hynes [16]
[17] reported success with extremity flaps as early as 9 days. In 1966, Klingenstrom
and Nylen [18] successfully transferred tubed skin flaps from the arm to the chest with successful
division in only 7 days. Notably, this experience enabled them to routinely divide
clinical flaps after intervals of 7–14 days. Another study using two cross-leg flaps
found that they were successfully divided after 11 days [9]. A study by Mandelbaum et al. [19] reported successful cross-leg flap division after 4 weeks. Other studies using a
pedicled anterolateral thigh and groin flap found that they could be successfully
divided at 3–4 weeks [11]
[20]
[21]. Trovato et al. [22] successfully divided a syndactylizing venous free flap on dorsal digital defects
at 3 weeks. Nevertheless, despite evidence that sufficient neovascularization develops
earlier than the traditional 3 weeks, many surgeons are content with the success assured
at 3 weeks, rather than tempting fate by performing flap division a few days earlier.
We also planned flap division after at least 3 weeks. Flap division was attempted
after observing flap capillary refill and any color change at the distal margin. Based
on the results of these tests, if revascularization of the flap was considered unclear
just before the separation operation, the flap division was delayed. Additionally,
in cases of large flaps, such as the anterolateral thigh free flap, most surgeons
feel that 3 weeks is too soon to attempt flap division. Based on our experience with
different types and sizes of flap divisions, we investigated whether there was a difference
in the actual timing of flap division between the two flap size groups. We classified
nine types of flaps into a large flap group and a medium and small flap group. In
both groups, flap division was successfully achieved after 3 weeks. Although there
were cases in which separation surgery was delayed more than 3 weeks, there was no
significant difference between the groups. Free flaps were typically used to anastomose
one perforator artery, without a significant difference between the two groups. Importantly,
we expected that large, thick flaps would have delayed flap division due to insufficient
blood flow compared to small flaps. However, this was not the case. These findings
suggest that if blood flow to the flap is sufficiently maintained for the time required
for revascularization, flap division may be attempted regardless of flap size. In
fact, in one case, an anterolateral thigh free flap that was applied over two digits
was successfully divided on the 17th day. Therefore, we believe that division of a
large flap is possible within 3 weeks.
In addition, we expected that necrosis at the distal end would be more severe in the
large flap group because the distance from the anastomosis site was greater. However,
there was no significant difference between the two groups, although severe partial
necrosis did develop in two cases ([Fig. 3]). The first case was a medium flap division surgery performed at 6 weeks. A thenar
free flap was applied on fingertip volar oblique pulp defects across the index and
long fingers. The flap was anastomosed to the perforator artery and the vena comitans
was anastomosed to the ulnar digital artery and volar vein of the long finger. Division
of the flap at the 3rd week was planned, but when clamping in the middle of the flap,
the capillary refill time in the distal area was observed to be slow, so surgery was
delayed. Division of the flap was performed 6 weeks after the first surgery, but discoloration
developed on the ulnar side of the divided flap on the index finger. Eventually, about
60% necrosis developed, but this was debrided and the flap healed without additional
surgery. Importantly, due to the difference in length between the long finger and
the index finger, an empty space was created between the bridged flap applied between
the two fingertips and the ulnar side of the short index finger. Therefore, the necrosis
was thought to be due to a flap design that did not sufficiently adhere to the recipient
site. Another case of severe necrosis was similar. An anterolateral thigh free flap
was performed on the amputation stump of the fingertip across the index and long fingers.
The perforator artery and nerve harvested with the flap were anastomosed to the radial
digital artery and nerve of the index finger. One vena comitans anastomosed to the
volar vein of the index finger. The flap was anastomosed to a pair of perforator arteries,
the vena comitans and nerve to the radial digital artery and the nerve and volar vein
of the index finger. For the same reason, division could not be performed at the 3rd
week, and was performed at the 34th week. About 60% of the divided flap on the radial
side of the long finger developed necrosis and was treated with additional skin grafting.
This suggests that if the flap and the recipient area are not in sufficient contact,
neovascularization will not progress at that site no matter how long it takes, as
it likely undergoes scarring or epithelialization. Therefore, to prevent necrosis,
one should check whether the flap is in sufficient contact and add additional fixation
sutures as needed.
Fig. 3. Case of partial necrosis. (A) A 61-year-old man suffered amputation of his right
index and long fingers. A volar oblique pulp defect and bone exposure of the fingers
were observed. (B) We harvested a flap with a single pair of perforator artery and
vena comitans from the ipsilateral thenar area and anastomosed it to the ulnar digital
artery and volar vein of the long finger. (C) Division of the flap was performed 6
weeks after the first surgery. About 60% of the necrosis that developed was on the
ulnar side of the divided flap of the index finger. (D) Three months later, the divided
flap had healed without the need for additional surgery.
In some patients, the interval of the flap division was prolonged as a result of the
surgeon’s limited operation schedule, the patient’s general condition, or personal
reasons. Notably, the majority of patient injuries in this study were caused by industrial
accidents. In the case of industrial accidents, patients discharged before the second
operation were required to obtain approval from their employer before flap division
surgery could be performed. In general, flap division was planned 3 weeks after the
free flap operation, but if the flap was considered unstable due to poor circulation,
surgery was postponed for a week. The aforementioned reasons resulted in a wide distribution
in the timing of flap division surgery among the cases.
In summary, our findings demonstrate that delays in flap division were not related
to the size of the flap. If the blood flow to the flap has been stable for more than
3 weeks, flap division can be attempted regardless of the flap size.
NOTES
Ethical approval
The study was approved by the Institutional Review Board of Gwangmyeong Sungae General
Hospital (IRB No. KIRB-2021-N-002) and performed in accordance with the principles
of the Declaration of Helsinki. The informed consent was waived because this study
design is a retrospective chart review.
Patient consent
The patients provided written informed consent for the publication and the use of
their images.
Author contribution
Conceptualization: JS Kim, SY Roh, CH Song, SH Koh, DC Lee, KJ Lee. Data curation:
JS Kim, SY Roh, CH Song. Formal analysis: JS Kim, CH Song. Methodology: JS Kim, SY
Roh, CH Song, SH Koh, DC Lee. Project administration: JS Kim, SY Roh, CH Song, SH
Koh. Writing - original draft: JS Kim, SY Roh, CH Song. Writing - review & editing:
JS Kim, SY Roh, CH Song, SH Koh, DC Lee, KJ Lee.
