Keywords propeller flap - perfusion - lower extremity
Soft tissue defects of the lower extremity are often classified as complex wounds.
Exposed structures such as tendons, neurovascular bundles, bones, and osteosynthesis
material require technical complex methods, often with the need for tissue transfer.
Perforator flaps represent a good option for mid-size defects. Although, especially
in adipose patients, a free perforator flap may be too bulky to allow for normal footwear
postoperatively.
The perforator-based propeller flap is a good alternative as a local flap. Due to
its structural similarity to the surrounding tissue, the lack of microvascular anastomosis,
and low donor site morbidity, it is particularly well suited for the distal lower
extremity and ankle. Perforators are found along the main vessels of the lower extremity.[1 ]
[2 ]
[3 ]
[4 ]
[5 ]
[6 ]
[7 ] Furthermore, the donor site may be placed over muscle, which shifts the original
complex defect over graftable tissue ([Fig. 1 ]).[2 ]
[8 ]
Fig. 1 (A ) Soft tissue defect lateral ankle left leg; (B ) 4 days postoperatively after propeller flap using a perforator of the fibular artery;
(C ) 7 days postoperatively.
Complication rates of propeller flaps are reported in up to 12 to 40% of cases.[2 ]
[9 ]
[10 ]
[11 ]
[12 ]
[13 ] Thus, a postoperative, objective perfusion monitoring is advantageous as perfusion
areas of perforators can vary individually[2 ]
[14 ] and rotation of the pedicle brings a higher risk of vascular complications.
The laser-Doppler-spectrophotometry (LDSP) is a useful tool to monitor microperfusion
of flaps. It detects tissue oxygenation, relative hemoglobin content, and flow rate
of deep dermal and subdermal layers. These parameters not only measure general perfusion,
but also allow a differentiation between inflow and outflow changes. Thereby, perfusion
changes can be detected faster and more precise than clinical evaluation alone.
Since partial flap necrosis equals a complete flap loss, understanding microcirculation
after pedicle rotation is fundamental to assess post rotation flap perfusion. In this
study, perioperative perfusion data of propeller flaps were analyzed to elucidate
microcirculatory changes.
Methods
A retrospective data analysis of patient treated between 2017 and 2021 was performed.
All data were gathered at the department of plastic and aesthetic surgery at the clinic
of trauma, hand, plastic and reconstructive surgery at the university hospital in
Würzburg, Germany. Only patients with soft tissue defect of the lower extremity were
included. Seven patients treated with propeller flaps and monitored peri- and postoperative
by a LDSP system were included. Patient data like gender, age, defect cause, and location
as well as comorbidities were evaluated. Additionally, perioperative data and complications
were evaluated.
Monitoring of propeller flap was performed with the LDSP system (O2C) of LEA Medizintechnik
GmbH (Gießen, Germany) was used. Two monitoring points were defined: perforator and
farthest point from perforator (distal). Measurements were made preoperative at the
planed and marked flap area, intraoperative after incision, rotation, 1 hour after
rotation, as well as postoperatively that same day and on the first, third, fifth,
and seventh day postoperatively. At every monitoring time point, three consecutive
measurements were used to calculate the mean.
The LDSP is a noninvasive diagnostic system that uses an external probe to apply two
measurement methods. The spectrophotometry system detects reflected light that was
emitted by the probe (830 nm at 30 mW and 500–800 nm at 20 W) and calculates the relative
hemoglobin content (rHb in AU) as well as tissue oxygenation (SO2 in percent). Because
emitted light is absorbed completely by vessels with a diameter larger than 100 µm,
light detected is reflected by the arterioles and venules of the dermal und subdermal
plexus. Additionally, the laser-Doppler method is used to detect the velocity of erythrocytes,
which is used to calculate the relative flow rate (flow in AU).
Results
From 2017 to 2021, soft tissue coverage was performed in seven patients using propeller
flaps. Of these, six were male and one was female with a median age of 62 years. All
flaps were performed by the same surgeon. The cause of defect was posttraumatic in
five patients, of which three patients had a primary posttraumatic defect and two
a wound healing disorder after osteosynthetic treatment. One patient had a vascular
and one a tumor-related defect genesis.
All defects were located at the lower extremity. Six patients had wound contamination.
Staphylococcus aureus was the most commonly detected pathogen. All patients underwent regular debridements
and wound conditioning using low-pressure wound therapy (vacuum-assisted closure)
prior to coverage. Furthermore, all patients received perioperative pathogen-specific
intravenous antibiotics. Four of the seven patients had comorbidities, of which arterial
hypertension, diabetes mellitus, and arterial occlusive disease were the most common.
Particularly, in the case of defects caused by trauma, there was a clear difference
in the time to defect coverage. Primary posttraumatic defects were covered after an
average of 15.3 days. In contrast, in wound healing disorder after osteosynthetic
treatment, it took an average of 76.5 days until coverage ([Table 1 ]).
Table 1
Patient data
Patients
7
Male
6
Female
1
Median age (y)
62
Diagnosis
Trauma
Posttrauma soft tissue defect
3
Postoperative wound break down
2
Tumor
1
Vascular genesis
Arterial
1
Location of defect
Thigh
2
Lower leg
1
Ankle
3
Foot
1
Perforator
Medial of anterior tibialis posterior
3
Lateral of anterior fibularis
2
Medial thigh
2
Mean incision/suture time (h)
02:00
Debridement before reconstruction
3
Days to reconstruction
Trauma
Post-trauma
15.3
Postoperative wound break down
76.5
Microbial contamination
Positive
6
Staphylococcus epidermidis
5
Bacillus species
1
Negative
1
Intravenous-antibiotics
Cefazolin
3
Clindamycin
2
Ampicillin/Sulbactam
1
Trimethoprim/Sulfamethoxazole
1
Amoxicillin
1
Ciprofloxacin
1
Combination
2
Complications
Over all patients
4
Early
Epidermolysis
2
Wound break down
3
Partial flap necrosis
1
Late
Partial flap necrosis due to infection pseudarthrosis
1
Revision surgery
Over all patients
2
Comorbidities
Over all patients
4
Hypertension
3
Diabetes mellitus
2
Artery occlusive disease
1
Nicotine abuse
Over all patients
1
Four patients experienced early complications (57%), two epidermolysis of the distal
flap areas (29%), three wound healing disorders (43%), and one partial flap necrosis
(14%). Among these, partial flap necrosis was the only early complication requiring
surgery. In the course of an infectious pseudarthrosis, one patient had a late complication
(14%) with a partial flap necrosis in the critical distal flap area also requiring
surgical revision.
Intraoperative perfusion monitoring showed a decline of blood flow after incision
of the flap up to 1 hour after rotation, especially at distal flap site. In contrast,
rHb and SO2 increased after incision. Subsequently, SO2 fell and recovered relative
with a slight delay to the restauration of the blood flow, especially at distal flap
site. The data also showed a prolonged increase in rHb and a slow normalization over
the observation period of 7 days ([Fig. 2 ]).
Fig. 2 Means of laser-Doppler-spectrophotometry (LDSP) data of all cases at perforator and
distal flap site; measurement quantities: relative flow (in AU), tissue oxygenation
(SO2 in %), relative hemoglobin content (rHb in AU); monitoring points of time: d
–1: preoperative, d0 PI: during surgery after incision, d0 PD: during surgery after
rotation, d0 1h: 1 hour after rotation, d0: postoperative during day of surgery, d1:
first day postoperative, d3: third day postoperative, d5: fifth day postoperative,
d7: seventh day postoperative.
In order to see differences between the cases with complications and complication-free
cases, data were analyzed groupwise.
In the complication-free cases, a decrease in blood flow, particularly at the distal
flap site, was observed up to 1 hour after rotation, which normalized within the initial
postoperative hours. There was also an increase of blood flow and a hyperemic period
on the first postoperative day. All measurement parameters normalized during the first
postoperative week ([Fig. 3 ]).
Fig. 3 Laser-Doppler-spectrophotometry (LDSP) data of complication-free cases at perforator
and distal flap site; measurement quantities: relative flow (in AU), tissue oxygenation
(SO2 in %), relative hemoglobin content (rHb in AU); monitoring points of time: d
–1: preoperative, d0 PI: during surgery after incision, d0 PD: during surgery after
rotation, d0 1h: 1 hour after rotation, d0: postoperative during day of surgery, d1:
first day postoperative, d3: third day postoperative, d5: fifth day postoperative,
d7: seventh day postoperative.
With regard to the cases with complications, there was a clear prolonged drop in blood
flow at distal flap site up to the first postoperative day. This was reflected in
the SO2 with a slight time lag ([Fig. 4 ]).
Fig. 4 Laser-Doppler-spectrophotometry (LDSP) data of complicative cases at perforator and
distal flap site; measurement quantities: relative flow (in AU), tissue oxygenation
(SO2 in %), relative hemoglobin content (rHb in AU); monitoring points of time: d
–1: preoperative, d0 PI: during surgery after incision, d0 PD: during surgery after
rotation, d0 1h: 1 hour after rotation, d0: postoperative during day of surgery, d1:
first day postoperative, d3: third day postoperative, d5: fifth day postoperative,
d7: seventh day postoperative.
An increase in rHb was found in complication-free as well as cases with complications
with the highest values at distal flap site of the cases with complications ([Figs. 3 ] and [4 ]).
Discussion
Covering soft tissue defects with propeller flaps is beneficial in many ways, especially
at the distal lower extremity. In particular, morphology of this local flap is key
for postoperative rehabilitation, function, and aesthetics. However, the design of
the flap entails adaptation and alteration of the microcirculation, which can lead
to serious complications, especially in the critical distal flap area. Moreover, the
perfusion of the critical areas cannot always be clearly foreseen and assessed intraoperatively.
In this regard, the present study can provide a better understanding of perioperative
perfusion changes.
A decrease of the relative blood flow (flow) was seen after flap rotation. Compared
to the perforator site, there was a greater drop in relative blood flow and a prolonged
adjustment period to the preoperative level at the distal flap site ([Figs. 2 ] and [3 ]). Furthermore, SO2 showed a decline as well a slight delay to the restauration of
the blood flow. Torqueing of the perforator possibly causes temporary constriction
of the vessel, leading to a reduction of flap perfusion and oxygen reserve. The initial
SO2 increase after flap incision is most likely due to preoxygenation during anesthesia
and a possible temporary congestion after interruption of venous outflow via the subdermal
plexus. As a result, a higher postcapillary oxygenation is registered based on a temporary
higher erythrocyte count and a relatively lower oxygen exploitation of the capillary
system. This correlates with the increase in rHb above 90 AU after flap incision,
which approaches the preoperative level slower than the flow and SO2. These perfusion
changes were even more distinct in the group of the cases with complications.
Prolonged ischemia of several hours can lead to ischemic tissue damage such as epidermolysis
or partial flap necrosis. With a rate of 10 to 11%, partial flap necrosis is the most
common complication of the propeller flap.[4 ]
[9 ]
[13 ]
[15 ] Complete flap loss as well as epidermolysis are reported up to 3 to 3.5% of cases.[9 ]
[13 ] Torqueing of the perforator is assumed to be one possible cause of temporarily decreased
arterial inflow. After a technical simulation, Wong et al recommended, in addition
to a rotation angle of less than 180 degrees and a diameter of more than 1 mm, the
preparation of the perforator of at least 3 cm length to distribute the torqueing
over the distance.[2 ]
[16 ] This addresses the inversely proportional relationship between rotation arc and
pedicle length.[15 ]
[16 ]
[17 ]
[18 ] In addition, the accompanying vein comitans, due to their low intravascular pressure
and wall thickness, are particularly susceptible to collapse during torqueing.[2 ]
[15 ]
[16 ]
[17 ]
[18 ] This leads not only to consecutive outflow obstruction with congestion in the flap,
but also may lead to thrombosis of the draining vessels. In the present study, transient
congestion was also observed due to the increased rHb and decreased flow. The rHB
increased after incision of the flap and decreased during the initial postoperative
period without reaching preoperative level, especially at distal flap site. Transient
venous congestion of 3 to 3.5% has been reported in the literature as well.[9 ] However, not only torqueing of the perforator but also interruption of the linking
vessels to adjacent angiosomes, leading to centralization of outflow after incision
and contributing to transient congestion. Especially at the lower extremity, the majority
of venous outflow occurs via subdermal plexus.[19 ]
Skeletonization of the perforator with the accompanying veins was reported to improve
outflow. Especially at fascial level, adherences may compromise blood flow of the
fragile and small venae comitans.[2 ] A meta-analysis of Bekara et al shows that most surgeons prefer skeletonization
of the perforator.[9 ] Additionally, intraoperative evaluation of perforator quality seems necessary. Jakubietz
et al pointed out risk factors, such as small diameter (< 1 mm), fibrous adherences,
arterial plaques, or macroscopic changes of vessel morphology.[11 ]
Another influencing factor discussed in literature is the proximity of the perforator
to the trauma area. The closer the perforator is located to the defect, the smaller
the flap needs to be. This has a positive impact on perfusion at the distal flap site.[20 ] In case of trauma-related defects, however, traumatization of the surrounding tissue
and thus possible posttraumatic perfusion impairment cannot be ruled out.[8 ] Jakubietz et al therefore recommend a distance between perforator and defect of
at least 3 cm,[11 ] despite there is no evidence of a correlation between trauma and complications so
far.[9 ]
In addition to the previously mentioned technical influencing factors, if intraoperative
clinical assessment of perfusion after rotation is difficult, intraoperative angiography
with indocyanine green is possible. This allows the perfusion of the entire flap to
be visualized in real time.[21 ]
[22 ] Cho et al further use color Doppler ultrasonography (CDS) intra- and postoperatively
to select and monitor the perforator based on flow velocity.[23 ]
Of the four patients experiencing early complications three had arterial hypertension.
The patient with partial necrosis had arterial hypertension, diabetes mellitus, and
nicotine abuse as comorbidities. However, because of the small study size, these data
are not statistically relevant. Nevertheless, similar observations suggesting a correlation
between comorbidities affecting microcirculation and vascular-related complications
are already described in the literature.[10 ]
Despite the limitations of the study such as the low number of patients and the punctual
measurements of LDSP, microcirculatory changes could be seen peri- and postoperatively.
With some experience, the LDSP can provide evidence of a vascular complication even
before the visual clinical signs of inflow or outflow obstruction.[24 ]
[25 ]
[26 ] However, for intraoperative and postoperative perfusion monitoring of flaps, indocyanine
green angiography as well as CDS are more suitable in clinical practice, as they directly
visualize blood flow in the perforator as well as in the peripheral vascular plexus.
LDSP uses indirect imaging via perfusion parameters and is more suitable for physiological
and pathophysiological study purposes.
Despite the previously mentioned recommendations for perforator selection and preparation,
disruption of the linking vessels and consecutive centralization of outflow requires
a longer adjustment. To minimize the risk of overcharging the flap, postoperative
mobilization should be adapted to the free-flap protocol for the lower extremity.
Conclusion
Torqueing the perforator by rotating the flap can cause an impairment in inflow and
outflow. If the impairment is prolonged, perfusion-associated complications are possible.
The identification of a viable perforator is particularly important. In addition,
a conservative postoperative mobilization is necessary to compensate for the impaired
and adapting outflow. The propeller flap is a viable option to cover lower extremity
soft tissue defects. If the perforator meets the selection criteria as well as preparation
recommendations and a postoperative adjustment period is given, the propeller flap
can be superior to free flap coverage in selected cases.
