Keywords
cross-leg - end-to-side anastomoses - free latissimus dorsi flap - single-vessel leg
- mutilating leg injuries
Introduction
Reconstruction of defects in the middle and lower thirds of the leg is challenging
and requires innovative solutions. Microsurgical reconstruction with free tissue transfer
has been considered the gold standard option for treating such defects, and this necessitates
the presence of adequate recipient leg vessels.[1]
[2] Reconstruction is more complex if the patient has preexisting vascular compromise
in the lower limb or when there is concomitant vascular injury.[3]
If there are no reliable recipient blood vessels, the use of the contralateral leg
vasculature is a potential option to supply the transferred tissues. Using cross-leg
bridge free tissue transfer was first described by Taylor et al in 1979, and the principal
concept of this technique is to anastomose the flap to intact vessels in the contralateral
noninjured leg. This temporary vascular anastomosis supports the flap until it forms
sufficient vascular connections with its edges and bed in the injured leg, then separation
is performed.[4]
A number of studies have reported successful reconstruction of leg defects with cross-leg
free tissue transfer, utilizing muscle/musculocutaneous flaps such as latissimus dorsi,
rectus abdominis, gracilis, and vastus lateralis muscles[5]
[6]
[7]
[8]
[9]
[10]
[11]; cutaneous flaps such as anterolateral thigh and deep inferior epigastric perforator
flaps[7]; or osteocutaneous flaps such as deep circumflex iliac artery (DCIA) and fibular
flaps.[7]
[11]
[12]
Most of these previous studies used end-to-end anastomoses to the recipient vessel
in the contralateral uninjured leg. The major drawback of end-to-end anastomoses is
scarifying one of the main blood vessels of the uninjured limb. Therefore, several
new reconstructive techniques have been introduced in order to maintain and preserve
the integrity of the recipient arterial system of the uninjured leg. These techniques
include redirecting the artery of the flap to the distal end of the recipient vessel
after pedicle division[13]
[14] or preparing the arterial blood supply of the flap in a Y- or T-shape fashion and suturing it to the recipient vessel in a flow-through anastomosis
fashion.[15]
[16]
Although there are many studies which demonstrated the use of free tissue transfer
with end-to-side anastomoses to recipient vessels in the same injured leg with the
aim of preserving distal perfusion in patients with impaired vasculature,[17]
[18]
[19] there are no studies that reported the use of an end-to-side anastomosis for cross-leg
free flaps as a method to maintain the integrity of the recipient vessel.
The purpose of this study is to present the outcomes of the use of cross-leg free
latissimus dorsi muscle flap for reconstruction of defects in single-vessel legs,
using end-to-side microvascular anastomosis to recipient vessels in the contralateral
leg without sacrificing any of its vessels.
Methods
We retrospectively reviewed 22 consecutive patients with traumatic soft tissue defects,
in legs with a single artery as documented by CT angiography, who underwent cross-leg
free latissimus dorsi muscle flap with end-to-side microvascular anastomosis to the
posterior tibial artery of the contralateral leg. After the ethical approval of the
study protocol, patients' data were collected from the patients' registry. The patients'
demographic and clinical data included sex, age, type of injury, location of the injury,
defect size, vascular status of injured legs, associated comorbidities, and time of
flap separation, postoperative complications, and revision procedures.
Surgical Technique
Under general anesthesia, sharp debridement is performed removing all necrotic or
scarred tissues until reaching a healthy bleeding tissue bed. In the contralateral
noninjured leg, the posterior tibial artery and one of its venae comitantes are dissected
and prepared as recipient vessels. An inferiorly based skin flap, approximately 4 cm
in width and length, is elevated to form the base of the bridge and protect the vascular
anastomosis.
With the patient in the lateral position, latissimus dorsi muscle flap is harvested
with the dominant thoracodorsal pedicle. A small skin island is included with the
muscle to facilitate flap monitoring. The muscle is then sutured to the healthy edges
of the defect in the injured leg allowing maximal interface between the flap and the
recipient site. The inferiorly based skin flap previously raised on the uninjured
limb is turned and sutured to the opposing edge of the muscle flap to form the bridge
([Fig. 1]).
Fig. 1 Intraoperative appearance of cross-leg bridge latissimus dorsi muscle flap with a
skin paddle. The muscle is sutured to the edges of the defect in the injured leg allowing
maximal interface between the flap and the recipient site. The two legs are fixed
together using an external fixator.
The two legs are fixed together using an external fixator. End-to-side microvascular
anastomosis is then performed between the thoracodorsal vessels and the posterior
tibial artery and one of its venae comitantes on the contralateral uninjured leg.
Patients are maintained on low-molecular weight heparin from the time of surgery till
the patient is completely mobilized to protect against deep venous thrombosis. All
patients stayed hospitalized until flap separation for monitoring of the flap and
adequate wound care. The muscle is covered by a split-thickness skin graft either
before the time of flap separation or during the flap separation procedure.
After 3 weeks postoperatively, the free flap pedicle was occluded with noncrushing
clamps at the bedside and the flap vascularity status was assessed clinically using
a needle prick test. If there is bright red blood bleeding in the distal part of the
flap and no signs of insufficient flap circulation noted, we then conduct the second
stage of flap separation and divide it from the recipient extremity. If flap circulation
seems insufficient, we wait further 4 or 5 days and repeat that. After the removal
of the external fixator and separation of the two legs, physiotherapy is started immediately
to prevent joint stiffness.
Results
The mean age at surgery was 21 years with a range from 12 to 31 years. Of the 22 patients,
19 were males and 3 were females. All defects were located in the leg. The defect
was on the right leg in 14 patients and the left leg in 8 patients. The defect size
ranged from 35 to 280 cm2 (mean 86 cm2). Follow-up ranged from 12 to 18 months, with an average of 15 months. The patients'
demographic, clinical data, and vascular status of each patient are summarized in
[Table 1]. There were no associated comorbidities in our patients.
Table 1
Patients' data
|
Patient no.
|
Age (y)
|
Sex
|
Side
|
Etiology
|
Location of Injury
|
Vascular status (injured vessels)
|
Defect dimensions (cm2)
|
Follow-up period
|
Complications
|
|
1
|
12
|
M
|
Right
|
RTA
|
Lower third
|
ATA, PTA
|
8 × 5
|
16 mo
|
Partial skin graft loss
|
|
2
|
18
|
M
|
Left
|
RTA
|
Middle third
|
ATA, PTA
|
10 × 6
|
12 mo
|
Recipient site infection
|
|
3
|
27
|
M
|
Right
|
RTA
|
Middle third
|
PA, ATA
|
7 × 5
|
18 mo
|
–
|
|
4
|
16
|
M
|
Right
|
RTA
|
Middle and lower third
|
PA, PTA
|
12 × 6
|
15 mo
|
Total flap ischemia
|
|
5
|
31
|
M
|
Right
|
RTA
|
Lower third
|
ATA, PTA
|
8 × 6
|
12 mo
|
–
|
|
6
|
24
|
M
|
Left
|
RTA
|
Upper and middle third
|
ATA, PTA
|
13 × 6
|
14 mo
|
Partial skin graft loss
|
|
7
|
18
|
F
|
Right
|
RTA
|
Lower third
|
ATA, PTA
|
9 × 5
|
18 mo
|
–
|
|
8
|
19
|
M
|
Left
|
Train accident
|
Upper and middle third
|
ATA, PTA
|
15 × 7
|
14 mo
|
Distal flap ischemia
Recipient site infection
|
|
9
|
15
|
M
|
Right
|
RTA
|
Middle third
|
PA, PTA
|
11 × 6
|
15 mo
|
–
|
|
10
|
19
|
M
|
Left
|
RTA
|
Middle third
|
ATA, PTA
|
12 × 5
|
12 mo
|
–
|
|
11
|
13
|
F
|
Left
|
RTA
|
Upper and middle third
|
ATA, PTA
|
18 × 11
|
18 mo
|
Partial skin graft loss
|
|
12
|
14
|
M
|
Right
|
RTA
|
Lower third
|
ATA, PTA
|
10 × 6
|
12 mo
|
|
|
13
|
16
|
M
|
Right
|
RTA
|
Upper and middle third
|
PA, ATA
|
20 × 14
|
14 mo
|
Seroma
Partial skin graft loss
|
|
14
|
27
|
M
|
Right
|
RTA
|
Middle and lower third
|
ATA, PTA
|
14 × 8
|
15 mo
|
–
|
|
15
|
29
|
M
|
Left
|
RTA
|
Upper third
|
PA, PTA
|
8 × 5
|
12 mo
|
–
|
|
16
|
19
|
M
|
Right
|
RTA
|
Middle and lower third
|
ATA, PTA
|
15 × 7
|
14 mo
|
Partial skin graft loss
|
|
17
|
25
|
M
|
Left
|
RTA
|
Middle third
|
PA, PTA
|
12 × 6
|
16 mo
|
–
|
|
18
|
20
|
F
|
Right
|
RTA
|
Middle third
|
ATA, PTA
|
13 × 7
|
12 mo
|
Recipient site infection
|
|
19
|
28
|
M
|
Right
|
RTA
|
Lower third
|
ATA, PTA
|
11 × 6
|
14 mo
|
–
|
|
20
|
22
|
M
|
Right
|
Firearm injury
|
Upper third
|
PA, PTA
|
8 × 7
|
18 mo
|
–
|
|
21
|
30
|
M
|
Left
|
RTA
|
Upper and middle third
|
PA, PTA
|
16 × 6
|
16 mo
|
Seroma
|
|
22
|
18
|
M
|
Right
|
RTA
|
Middle third
|
PA, ATA
|
14 × 7
|
14 mo
|
–
|
Abbreviations: ATA, anterior tibial artery; PA, peroneal artery; PTA, posterior tibial
artery; RTA, road traffic accident.
All injured extremities were reconstructed with latissimus dorsi cross-leg free flaps
as described in the surgical technique section. End-to-side anastomosis was performed
to the contralateral posterior tibial artery in all cases to maintain distal blood
flow. The second stage procedures were performed between 3 and 6 weeks. [Figs. 2] and [3] show pre- and postoperative photographs.
Fig. 2 (A) Preoperative appearance showing extensive soft tissue loss on the anterior and medial
aspect of the right leg with exposed tibia and bone loss. (B) Radiograph showing fracture both bones of the leg. (C) Appearance 6 weeks after cross-leg bridge free latissimus dorsi muscle flap anastomosed
to the posterior tibial vessels of the left leg. (D) Appearance 5 weeks after flap separation and split-thickness skin grafting. The
flap is completely healed. There are small areas of skin graft loss which needed regrafting.
Fig. 3 (A) Preoperative appearance showing chronic unstable scar on the anterior aspect of
the right leg and extensive scarring of the surrounding area, with a history of traumatic
soft tissue loss due to road traffic accident and previous two skin grafting procedures.
(B) Appearance 3 weeks after excision of the scarred tissues and coverage of the defect
by cross-leg bridge free latissimus dorsi muscle flap anastomosed to the posterior
tibial vessels of the left leg. Skin grafts are completely taken. (C) Appearance 16 months after flap separation showing complete healing and stable soft
tissue coverage of the tibia.
Complete flap survival was reported in 20 cases (91%). One patient had total flap
ischemia which was managed by debridement and negative pressure wound therapy for
3 weeks until the wound was clean with healthy granulation tissue, then a split-thickness
skin graft was applied. Another patient had distal marginal flap ischemia that was
managed by debridement, antibiotics, and wound care until healing by secondary intention
occurred. Infection in the recipient site occurred in three patients and was treated
conservatively by antibiotics and repeated wound dressings. Mild seroma in the flap
donor site occurred in two patients and was managed by syringe aspiration for one
time with no recurrence. All wounds in the contralateral leg healed uneventfully without
complications apart from the anticipated scarring. Five patients needed regrafting
of residual small exposed parts of the muscle flap due to partial skin graft loss
([Fig. 2D]). Although revision touch-up procedures were offered during follow-up, none of the
patients requested further refinements.
Discussion
Transposition of local tissue flaps (fasciocutaneous or muscle), if available, is
the first choice to reconstruct defects of the leg. When there are no available local
tissues for transposition, distant flaps and free flaps play a major role in these
occasions.[2]
[20]
Pedicled cross-leg flaps have been widely used for the reconstruction of leg and foot
defects since 1854.[21] There has been no exact universal design for cross-leg flaps in the literature.
Proximally based and transverse or oblique laterally based cross-leg flaps have been
described.[21]
[22] With a better understanding of the anatomy of leg perforators, distally based and
perforator-based flaps became more frequent.[23]
[24]
The continuous improvement of the outcomes of microsurgical interventions has made
free flap reconstruction a routine option in lower extremity reconstructive surgery.[19] Successful free flap reconstruction of leg defects requires optimal flap choice,
in addition to selecting appropriate recipient vessels in the leg.[7] However, the lack of recipient vessels or the presence of single artery in the injured
leg makes the free flap transfer a challenging and unsafe procedure. Many authors
found that the rate of free flap failure increased when patent vessel numbers is decreased
on the injured lower extremity.[25]
[26] Also, Khouri and Shaw demonstrated that the rate of anastomotic thrombosis doubled
in single-vessel legs.[27] Although successful microvascular reconstruction of lower extremity defects using
an end-to-side anastomosis has gained attention, especially in patients with mutilating
limb injuries or impaired vasculature as it does not compromise distal perfusion,[19]
[28] an end-to-side anastomosis to the single dominant vessel, which supplies the ipsilateral
limb, carries the risk of losing both the flap and foot.[29]
Haddock et al described using the perforator-to-perforator anastomoses as another
solution to avoid scarifying of the ipsilateral limb recipient vessel.[29] However, we believe that perforator-to-perforator anastomosis is technically demanding
and is very difficult to apply in a limb with a wide zone of injury.
Therefore, it is necessary to use alternative options when there are no adjacent vessels
available near the soft tissue limb defect and to perform the microvascular anastomosis
outside the zone of injury. These include the use of vein grafts[30] as solutions to perfuse free flaps through anastomosis with a healthy proximal remaining
blood vessel which is used as a recipient vessel on the ipsilateral extremity outside
the zone of injury. Vein grafting requires another donor site, carries a risk of vein
kinking, and increases the number of vascular anastomoses which subsequently raises
the risk of thrombosis and free flap failure especially when using long vein grafts.[27]
[30]
[31]
[32]
[33] One study reported a fivefold increase in the incidence of anastomotic thrombosis
when using vein grafts.[27]
The use of cross-leg bridge free flaps is a relatively old surgical technique, firstly
described by Taylor et al in 1979 to solve the problem of lack of vessels in the recipient
leg using cross-leg free DCIA flap to reconstruct bony and soft tissue defect in the
leg.[4] The technique is simply based on performing temporary anastomosis (end-to-end) between
the vascular pedicle of the flap and an intact vessel of the contralateral leg that
is transected then anastomosed to the flap and later divided as soon as adequate vascularization
of the flap occurs from its edges and bed.[4] The cross-leg free flap is indicated when there is only a single nutrient artery
supplying the extremity, when the neighboring vessels are damaged or not available
and the use of vein grafting is not feasible or risky, and when the adjacent vessels
were used in former free flap operation.[2]
Cross-leg free flaps allow the transfer of the needed tissues including skin and muscle
with or without bone using microvascular anastomoses performed away from the zone
of injury to reconstruct challenging tissue defects with healthy vascularized tissue.[4]
[7] Since 1979, several studies have been published reporting successful reconstruction
of leg defects using cross-leg free tissue transfer with end-to-end anastomosis. Some
studies described using large muscle flaps such as latissimus dorsi which helped in
the successful salvage of complicated leg defects[6]
[8]
[10] and in treatment of osteomyelitis.[5]
Yamada et al applied the same technique in six patients using free rectus abdominis
muscle flap anastomosed to vessels of the contralateral noninjured leg with a good
outcome.[9] Townsend successfully used cross-leg free DCIA osteo-cutaneous flap in 10 cases
to reconstruct leg defects with bone loss 6 to 12 cm.[12] Yu et al published a large series of 85 patients who underwent cross-leg free flap
reconstruction utilizing a variety of flaps including latissimus dorsi myocutaneous,
free fibula, free fibular osteocutaneous, and free iliac osteocutaneous flaps and
showed an overall success rate of 95%.[11] Ozkan applied the same principle in 27 patients using different skin and muscle
flaps including anterolateral thigh, latissimus dorsi muscle, gracilis muscle, vastus
lateralis musculocutaneous, tensor fascia latae, and deep inferior epigastric perforator
flaps, with 93% success rate.[7]
Latissimus dorsi flap has many advantages as a cross-leg free flap in the reconstruction
of complex leg defects as it can provide a sizable flap with a long pedicle and good
vessel caliber.[31] Its large muscle component allows durable closure of complex wide defects.[6]
The use of the posterior tibial vessels as cross-leg bridge recipient vessels has
often been described in the literature as an end-to-end anastomosis as this allows
easy positioning and safe anastomosis.[3]
[7]
[10]
[11]
[12]
[30] However, this entails sacrificing these vessels by transecting them at the time
of anastomosis.
This problem has led to design several innovative techniques to maintain the integrity
of the recipient arterial system. Akyurek et al described a new technique to restore
the continuity of the recipient artery in cross-leg free latissimus dorsi flap procedure
after end-to-end anastomoses. They reestablished the continuity of the posterior tibial
artery at the time of flap separation by dissecting the thoracodorsal artery till
its bifurcation in the muscle flap, transecting it, and reanastomosed to the distal
ligated end of the posterior tibial artery.[13]
[14] However, this makes the flap separation another microsurgical procedure with prolonged
hospitalization and possibly more complications. The flow-through pedicled free flap
procedure is introduced not only to provide blood supply to the flap but also to preserve
the integrity of the recipient vessel and distal leg circulation.[34] Topalan et al presented a cross-leg latissimus dorsi free flap procedure with the
arterial thoracodorsal pedicle dissected in a Y-shaped for the flow-through continuity
of the recipient artery.[15] Gencel et al executed the cross-leg free latissimus dorsi flap procedure where the
thoracodorsal and circumflex scapular artery (or serratus branch, arterial pedicle)
were fashioned as T-shaped and sutured to the contralateral posterior tibial artery
in a flow-through anastomosis.[16] Although the flow-through free flap procedure is introduced to preserves the blood
circulation in the healthy lower limb, it carries several disadvantages including
the need to perform two anastomotic lines which increase the risk of postoperative
vascular thrombosis. In addition, it is difficult to prepare a segment of Y-shaped
or T-shaped arterial bifurcation during the harvest of free latissimus dorsi flap.[14]
[35]
Yu et al suggested an alternative option to preserve integrity of the recipient vessel
which is an end-to-side anastomoses to the contralateral limb in order to maintain
continuity of the distal blood flow, although they performed the microvascular anastomoses
of their cross-leg bridge free flaps series in an end-to-end fashion.[11] Several previous studies have reported the use of end-to-side anastomosis to recipient
vessels in the same injured leg to preserve the leg vascular flow and reported no
significant difference in the rate of flap complications between the outcome of end-to-end
and end-to-side anastomoses in free flap reconstruction of lower limb defects.[19]
[28] However, to the best of our knowledge, there are no reported studies that described
performing an end-to-side anastomosis in patients indicated for lower limb reconstruction
using cross-leg free flaps as a method to preserve the integrity of the recipient
vessel.
In the present study, we performed an end-to-side anastomosis of the thoracodorsal
vascular pedicle of the free latissimus dorsi flap to the contralateral recipient
posterior tibial artery while preserving the single vessel of the injured leg untouched
and at the same time preserving the recipient vessels of the uninjured limb undisturbed
after separation of the flap. This is the first case series which reported cross-leg
free flap reconstruction using an end-to-side anastomosis to the posterior tibial
vessels of the contralateral leg. We found that the use of this technique in 22 consecutive
cases has resulted in an overall success rate of 91% which is comparable to the results
of other previous studies describing cross-leg free flap using end-to-end or flow-through
anastomosis. Furthermore, we believe that the end-to-side anastomosis technique, described
in this study, have distinct advantages. The most obvious advantage is the prevention
of reduction of the blood flow to the recipient extremity and protecting the continuity
of the posterior tibial vessels of the noninjured leg while maintaining efficient
free flap perfusion. This technique has also obviated the need to use long vein grafts
or to prepare bifurcated thoracodorsal arterial pedicle that cannot be easily available
for flow-through anastomosis. In addition, it seems that end-to-end anastomosis to
a major artery causes problems such as temporary congestion or severe swelling of
the free flaps which are induced by excessive inflow. These may be other advantages
of using end-to-side anastomosis.
These findings suggest that cross-leg free flap using end-to-side anastomosis is an
efficient and safe alternative for reconstruction of mutilating leg injuries with
compromised vasculature, without sacrificing any vessel in the donor leg.
The limitation of this study is its retrospective design and being a case series without
prospective data or a comparison control group using end-to-end or flow-through anastomosis
which preserves the integrity of the contralateral recipient vessel. However, this
series demonstrates that the end-to-side anastomosis to the contralateral recipient
vessel is a viable option in cross-leg free flaps reconstruction supported by the
high rate of flap survival and low complication rate.
In conclusion, cross-leg free latissimus dorsi muscle flap is a reliable and safe
technique for the reconstruction and salvage of complex leg defects in mutilating
leg injuries. It can provide a good reconstructive solution, especially in cases of
leg injuries with a single artery, without increasing the risk of complications. As
far as preservation of the donor limb circulation is concerned, cross-leg end-to-side
anastomoses are a reasonable alternative as it maintains the continuity of the donor
leg vessels for any possible future need.