Keywords
retrograde lateral supramalleolar flap - foot and ankle reconstruction - soft-tissue
defects - reconstructive surgical procedures
Introduction
The injury of the foot can lead to the exposure of critical structures such as tendons,
bones, nerves, and vessels. In those cases, the wound should be covered to protect
structures and a suitable flap is necessary for proper reconstruction.[1] Local flaps are often inadequate for covering medium to large wounds. The free flaps
have been proposed as a solution to cover the wound in this region. However, the use
of free flaps has some disadvantages, including needing expert surgeons proficient
in microsurgery, high-quality instrumentation, and extended operative durations.[1] Another option is the sural flap, a popular choice for foot reconstruction. However,
Jaiswal et al demonstrated the superiority of the lateral supramalleolar (LSM) flap
over the reverse sural flap in covering soft-tissue defects on the dorsum of the foot.[2] Additionally, the pivot point of the sural flap, located in the lower back calf,
may adversely impact the aesthetic outcome of the ankle.[3]
[4]
[5]
The retrograde LSM flap, first introduced by Masquelet et al in 1988 to cover soft-tissue
defects of the ankle and foot,[6] is a promising alternative. Valenti et al refined the technique by elevating the
subcutaneous pedicle.[7] Many authors have reported successful outcomes in using this flap. They used the
mixed-blood supply pattern to reconstruct ankle and foot defects.[8]
[9]
[10] Some studies have also reported a high success rate in using the adipofascial LSM
flap in limited sample sizes.[11]
[12] Anatomically, the LSM flap receives antegrade blood flow from the peroneal artery
(sometimes from the anterior tibial artery) and retrograde blood flow via anastomosis
from the anterolateral malleolar artery to the descending branch of the perforating
branch of the peroneal artery. Most of the reports were about the antegrade LSM flap,
but there was only one report that demonstrated excellent outcomes in using the retrograde
LSM flap in covering soft-tissue defects in the foot and ankle.[9] In this study, the results and clinical experiences in using the retrograde LSM
flap to cover larger soft-tissue defects are presented.
Materials and Methods
Study Settings
This study was prospective cross-sectional observational study performed from December
2017 to December 2022. The follow-up time was 6 to 30 months.
Participants
Forty-five patients with 46 retrograde LSM flaps (one patient underwent bilateral
foot treatment) were in the study. All the patients had foot and ankle structure exposure,
including bones, vessels, tendons, or nerves, within subunits such as the medial malleolus,
midfoot, dorsum of the forefoot, and Achilles' tendon. The exclusion criteria consisted
of exhibiting clinically significant previous injury in the lateral lower calf and
peripheral vascular disease.
Sampling
After the wounds were free from necrotic tissues and local infection, the flap was
used. In some challenging cases, debridement was performed, and a vacuum-assisted
closure system was applied, with a 5-day interval preceding the application of retrograde
LSM flaps ([Fig. 1]).
Fig. 1 Algorithmic approach for use of retrograde lateral supramalleolar (LSM) flap.
Measurement
The age, gender, injury etiology, associated injuries, and injury site were recorded
preoperatively. The flap and pedicle settings were collected intraoperatively. The
technical parameters such as total flap length (measured from the pivot point to the
flap's distal edge), flap surface dimensions, wound size, and operation duration were
recorded intraoperatively. Surgical complications, encompassing venous congestion,
flap failure, and postoperative interventions, were observed within 1 to 7 days postsurgery.
Outcome Assessment
Consistent with previous research, successful outcomes were defined as instances where
retrograde LSM flaps survived or exhibited minor complications, not necessitating
major surgery repetition. This category included flaps with minor distal edge necrosis
necessitating minor surgical interventions such as debridement and secondary suturing,
excluding skin graft techniques typically performed in significant operations. Failure
outcomes comprised flaps exhibiting partial necrosis necessitating repeat major surgery
to ensure optimal outcomes.
Operation Technique
The flap's axis aligns with the leg's central line, positioning the anterior border
of the flap at the tibia crest line, while ensuring the posterior limit does not extend
beyond the hind of the fibular frontier. The pivotal landmark is identified at the
intersection of the line connecting the malleoli and the axis of the fourth metatarsal
bone ([Fig. 2]). Measurements of the distance from the wound's proximal edge to the pivot point,
along with wound dimensions, aid in estimating the pedicle length. A preliminary flap
design is delineated on the lateral aspect of the leg, with the flap's axis serving
as a midline parallel to the anterior tibial crest and the posterior margin of the
fibula. To facilitate a tension-free inset and pivot arch, 0.5-cm dimensions are added
to the flap size and 2 cm to the pedicle length. The flap's dimensions are consistently
slightly larger than the wound size to ensure optimal management of complex-shaped
defects.
Fig. 2 Flap designing and dissecting. (A) Mapping the provisional flap. (B) First, explore the pedicle vessels. (C) Completely elevating the flap. (D) Suturing the flap to the recipience site.
The subcutaneous pedicle, 3 cm in width with 1 cm of skin in the middle serving as
a roof, resembles a tent structure. An exploratory incision is initiated at the anterior
border of the pedicle, extending up to the subfascial plane, revealing the perforating
branch of the peroneal artery on the surface of the interosseous membrane. The descending
branch is isolated up to the pivot point, encompassing superficial veins within the
pedicle to enhance venous outflow. Following confirmation of the pivot point, the
emergence perforator branch of the peroneal artery is meticulously tied and separated
under loupe magnification to prevent inadvertent vessel damage. After that, the flap
is raised, the superficial peroneal nerve is separated at the distal edge, and the
nerve stump is deeply buried under the muscle belly. The flap is then transferred
to the recipient site through an incised skin tunnel, with the subcutaneous pedicle
spread out to minimize thickening. At the middle of the pedicle, 1 cm of skin was
sutured to the tunnel to form a tent roof, so the skin grafting was not used and there
was no dog-ear. The flap was sutured loosely to prevent postoperative swelling. The
thin skin graft was applied to the donor site. Finally, a careful inspection was made
to be sure the pedicle was not under traction. A cast was used to stabilize the ankle
to protect the flaps from stress.
Postoperative Follow-Up
Within 8 hours after surgery, the flap color, temperature, and capillary refill were
evaluated carefully. Patients and their relatives were instructed to keep the affected
limb in an appropriate position to avoid pressure on the pivot point, flap pedicle
inset, and recipient site.
After 5 days, the gauze covering the skin graft at the donor site was removed. An
additional closure was made, if necessary, with a minor surgery. In this way, the
patient was often discharged on the seventh day. In case necrotic flaps are unrecoverable
through minor surgical interventions, necrotic tissue is debrided, followed by a skin
graft.
Statistical Method
Stata version 14.0 was used for data analysis. Qualitative variables such as causative
injury, flap outcome, associated injuries, and leg site were shown by frequency and
percentages. Quantitative variables including flap dimension, wound size, patients'
age, and surgery time were subjected to analysis using mean or median, as deemed appropriate.
Results
The follow-up time ranged from 6 to 30 months, with a mean of 15.2 months. Forty-six
retrograde LSM flaps were used on 45 patients (35 males and 10 females), with an average
age of 41.17 years (range: 15–73 years). The mean size of wounds was 37.61 cm2, while the mean flap dimension was 48.43 cm2. The average flap length, measured from the pivot point to the distal edge was 17.47 cm
(10–24 cm). The mean operative time was 90.98 minutes ([Table 1]).
Table 1
Quantitative data
|
Variables
|
Mean
|
Minimum
|
Maximum
|
|
Age of patient (y)
|
40.17
|
15
|
73
|
|
Wound size (cm2)
Flap dimension (cm2)
Total length of flap (cm)
Operation time (min)
|
37.61
48.43
17.47
90.98
|
9
12
10
60
|
80
104
24
200
|
In this study, two-thirds of soft-tissue defects occurred in the forefoot, accounting
for 33 of 46 flaps (71.74%; [Table 2]). Four flaps had partial necrosis, necessitating secondary skin graft procedures.
The first case was a 61-year-old patient with a 6 × 11 cm wound in the midfoot, covered
by a flap 7 × 12 cm in dimension and 19 cm in total length. Postoperative venous congestion
caused partial flap necrosis. The second case was a 29-year-old patient with a 3 × 4 cm
forefoot wound. The flap was 4 × 5 cm and 19 cm in total length. Subsequent venous
congestion resulted in partial flap necrosis, requiring a secondary skin graft procedure.
Similarly, in the third case, a 50-year-old patient experienced venous congestion
and partial flap necrosis following the use of a 6 × 11 cm flap to cover a 6 × 12 cm
forefoot defect ([Fig. 3]). The last case was a 51-year-old patient with a 5 × 11 cm forefoot wound. The flap
was 5.5 × 12 cm. A secondary skin graft was used to cover the wound due to venous
congestion and partial flap necrosis.
Table 2
Patient characteristics
|
Variables
|
Total (n = 46)
|
Defect location
|
|
Forefoot (n = 33)
|
Midfoot (n = 8)
|
Heel (n = 3)
|
Medial malleolus (n = 2)
|
|
Gender
|
|
Male
Female
|
36
10
|
26
7
|
6
2
|
3
0
|
1
1
|
|
Leg site
|
|
Right
Left
|
30
16
|
22
11
|
5
3
|
2
1
|
1
1
|
|
Cause of injury
|
|
Traffic
Labor
Ulcer
Burn
|
39
1
3
3
|
29
1
3
0
|
7
0
0
1
|
2
0
0
1
|
1
0
0
1
|
|
Pedicle inset
|
|
Tunneled
Incised ceiling skin tunnel
|
12
34
|
7
26
|
3
5
|
0
3
|
2
0
|
|
Flap setting
|
|
Primary close suture
Loosely inset
|
6
40
|
5
28
|
1
7
|
0
3
|
0
2
|
|
Venous congestion
|
|
Yes
None
|
9
37
|
5
28
|
2
6
|
2
1
|
0
2
|
|
Flap outcomes
|
|
Survival
Distal edge necrosis
Partial necrosis
|
38
4
4
|
28
2
3
|
6
1
1
|
2
1
0
|
2
0
0
|
|
Post-op intervention
|
|
Skin graft
None
Minor surgery
|
4
38
4
|
3
28
2
|
1
6
1
|
0
2
1
|
0
2
0
|
|
Associated injuries
|
|
Phalange amputation
Medial malleolus fracture
Tarsal fracture
None
Extend skin loss
|
3
1
13
26
3
|
3
0
10
19
1
|
0
0
3
4
1
|
0
0
0
2
1
|
0
1
0
1
0
|
Fig. 3 Third failure case with partial flap necrosis. (A) Wound before surgery. (B) First operative day. (C) Severe venous congestion led to partial flap necrosis. (D) Result after the second skin graft procedure.
The overall successful outcome of this study was 91.3% (42 of 46 flaps). Donor site
healing proceeded uneventfully following the skin graft procedure, with no evidence
of tendon adhesion in any case.
Discussion
The standard approach to foot reconstruction should optimize recipient site benefits
and minimize donor site morbidity. In cases of severe foot trauma, the choice flap
is the flap that can be used to cover the tissue defect, while bone fracture and tendon
rupture can be managed simultaneously. Until now, there has been no optimal method
for reconstructing foot areas although some techniques were proposed and performed.[1]
[5]
[13] Despite its popularity, the sural flap remains cumbersome for midfoot and forefoot
coverage due to its pivot point situated behind the ankle, approximately 2 cm above
the lateral malleolus.[3]
[4] The dorsal metatarsal artery perforator flap has been recently introduced, but it
was used predominantly for forefoot reconstruction.[14] While free flaps offer a viable option for foot reconstruction, they necessitate
specialized expertise in microvascular techniques. As an alternative approach, in
this study, the retrograde LSM technique was used, and it provided good coverage to
soft-tissue defects. The mean wound size and flap dimension were 37.60 and 48.43 cm2, respectively. This technique effectively covers soft-tissue defects in various foot
subunits, including the forefoot, midfoot, medial malleolar, and heel. Because the
retrograde LSM flap starts anterior to the ankle, the distance from it to the regions
of the dorsal foot was short. This study had a mean total flap length of 17.46 cm
(ranging from 10 to 24 cm); these lengths were chosen so that they were suitable for
the wound. In this study, for all cases of the wound settled in the forefoot, the
length of the flap reached the wound easily. The surgical procedure took a reasonable
time, averaging about 90.98 minutes.
The identification of the surface landmark of the pivot point was very important in
flap design and anticipation of flap viability.[1] In this study, the pivot point was at the intersection of the fourth metatarsal
bone's axis and the line connecting the two malleoli. This placement, approximately
2 cm higher than the sinus tarsi point as suggested by previous authors, facilitates
the preservation of the inferior extensor retinaculum during flap pedicle dissection.[6]
[10] Preservation of this retinaculum is crucial for maintaining normal extensor tendon
function and preventing the bowstring phenomenon, which may compromise foot function
and postoperative aesthetic outcomes. Following the pivot point, the flap lengths
can be up to 24 cm, enabling enough coverage of various foot subunits, including the
distal margin of the dorsal forefoot.
The retrograde LSM flap, based on this pivot point, had a remarkable versatility.
It can be used to cover soft-tissue defects in multiple foot subunits, encompassing
the forefoot, midfoot, medial malleolus area, and even the heel region.
For the defects in the midfoot and forefoot, the sural flap had been usually used.
However, the sural flap's posteriorly located pivot point necessitates the subcutaneous
pedicle to traverse around the ankle to reach the anterior region, thereby compromising
aesthetic outcomes in forefoot reconstruction. With a mean length of 17.46 cm, retrograde
LSM flaps provide adequate coverage for the midfoot and forefoot without disadvantage.
Similarly, the sural flap is primarily utilized for heel reconstruction, but in the
cases where the heel defects involve injury of the sural flap's perforators, retrograde
LSM flaps serve as reasonable alternative procedures ([Fig. 4]). In this study, such cases had excellent results, contrary to prior reports indicating
challenges with retrograde LSM flap use in heel reconstruction.[8] This study showed the potential efficacy of retrograde LSM flaps in heel reconstruction
and offered valuable insights for future clinical applications.
Fig. 4 Heel reconstruction by retrograde lateral supramalleolar (LSM) flap. (A) Wound before operation. (B) Flap dissection. (C) Flap healing in the recipient site 20 days postoperation. (D) At 14 months postoperation.
Commonly, patients with bone fractures and soft-tissue defects will be repaired with
a flap before bone fixation. In this study, a triple malleolus fracture was fixed
and a soft-tissue defect was covered with a retrograde LSM flap simultaneously on
a patient. The patient was a 37-year-old woman, involved in a traffic accident, and
presented with a triple malleolus fracture and a soft-tissue defect at the medial
malleolus area. The medial malleolus bone fixation was performed, and a retrograde
LSM flap was applied using the same approach utilized for fibular reduction and plate
internal fixation. The flap was then transferred to the recipient site through a skin
tunnel. The bone was healed and the flap was integrated ([Fig. 5]). This case illustrates the feasibility of simultaneously executing the retrograde
LSM flap with bone fixation techniques. It gives an approach for patients with foot
tissue defects associated with bone fractures involving the medial malleolus, metatarsals,
and heel.
Fig. 5 Combined flap dissection with bone fixation in one procedure. (A) Expose medial malleolus fracture. (B) Bone fixation by plate and flap elevation. (C) Closing the wound by retrograde lateral supramalleolar (LSM) flap. (D) X-ray image of bone fixation. (E) Donor site healing by a skin graft. (F) Flap healing.
Although the overall success rate of the study was high (91.3%), there were failed
cases. Two of the failed cases had pedicle tunnel techniques in which long flaps (19 cm
in total length) were passed through a tunnel to the recipient site. This tunnel might
be small and cause pressure on the pedicle, compromising the blood supply to the flaps.
Additionally, maybe the flaps failed because their dimensions were large (66 cm2) and they covered soft-tissue defects far in the forefoot. It was wondered whether
using vasodilators, maintaining a warm temperature around the postoperative flaps,
and local heparin could help prevent venous congestion, rescue these flaps, and enhance
flap survival.
The results of this study show that the LSM flap can be used in retrograde patterns,
while previous authors extensively used it in a mixed pattern and smaller-scale studies
focused on the retrograde pattern. The results also show that the retrograde LSM flap
can be used successfully for forefoot defects.
This study has some limitations. As a cross-sectional observational study, it lacked
a control group for comparative analysis of the method's effectiveness. So it is difficult
to determine whether this method is superior to others in covering soft-tissue defects
in the foot and ankle region or not. The landmark surface of the pivot point used
in the study is subjective. Despite it being exact in every case, it was not linked
to any anatomy report. An anatomy study should be performed to find out the best pivot
point.
Conclusion
The retrograde LSM flap has several advantages, including the capacity for widening
flap dimensions, ease of design and operation, and reduced technical complexity compared
with microsurgery flaps. The flap can be used to cover soft-tissue defects of various
foot subunits such as the heel, medial malleolus, midfoot, and especially the dorsal
forefoot. It has compatibility with simultaneous bone reduction and internal fixation
procedures.
