Laser-Doppler Examination of the BloodSupply in Pericranial Flaps
Brett Miles, DDS, MD,* Scott Davis, PhD,†
Craig Crandall, PhD,‡ and Edward Ellis III, DDS, MS§
Purpose: The purpose of this investigation was to determine if there is evidence suggestive of bloodflow within pericranial flaps.
Patients and Methods: An index of blood flow using laser-Doppler blood flowmetry was obtained inpericranial flaps from 10 patients who were undergoing a coronal flap for reconstructive procedures. Thedata were analyzed using fast Fourier transformation to indicate the presence or absence of blood flow.
Results: All but 1 pericranial flap showed evidence of blood flow within. Most flaps had blood floweven several centimeters distal to the origin of the flaps’ pedicles.
he pericranial or galeopericranial flap is arguably theost versatile flap available for reconstruction of the
raniofacial skeleton and face. Reconstructive surger-es using the pericranial flap have revolutionized an-erior skull base reconstruction. The use of pericranialaps in a variety of skull base defects was initiallyescribed in the late 1970s.1-4 The pericranial flaprovides an excellent means to obtain the primaryoals of skull base reconstruction including the pre-ention of brain herniation, intracranial infections,erebrospinal fluid leakage, and pneumocephalus.hile advances have occurred, the technique re-ains a standard when reconstructing the anterior
kull base for a variety of defects.4-18
*Clinical Fellow, Head and Neck Oncology, Department of Oto-
aryngology Head and Neck Surgery, University of Toronto Health
etwork, Toronto, Ontario, Canada.
†Assistant Professor, Neurology, University of Texas Southwest-
rn Medical Center, Dallas, TX.
‡Institute for Exercise and Environmental Medicine, Presbyterian
ospital of Dallas, Dallas, TX.
§Formerly, Professor, Oral and Maxillofacial Surgery, Univer-
ity of Texas Southwestern Medical Center, Dallas, TX; and
urrently, Chair, Department of Oral and Maxillofacial Surgery,
niversity of Texas Health Science Center at San Antonio, San
ntonio, TX.
Address correspondence to Dr Ellis: University of Texas Health
cience Center at San Antonio, 7703 Floyd Curl Drive, MC 7908, San
2010 American Association of Oral and Maxillofacial Surgeons
278-2391/10/6808-0005$36.00/0
soi:10.1016/j.joms.2009.12.024
1740
Reconstruction of the skull base, although the mostommon application, is not the only application ofericranial flap reconstructions. Frontal sinus obliter-tion for traumatic injuries to the frontal sinus andeconstruction after frontal sinus cranialization areommon applications of the pericranial flap and haveeen shown to be reliable in long-term series withelatively few complications.19-23 The use of pericra-ial flaps has been described after endoscopic neuro-urgical procedures, such as ventriculostomy, provid-ng an excellent option to control cerebral spinal fluideakage.5 Flaps have also been shown to be invaluablen nasal reconstructive procedures including repair ofasal septal perforation and nasal reconstruction androviding internal lining to augment other reconstruc-ive procedures.24-26 The pericranial flap has alsoeen reported to provide a vascular reconstructionor medial orbital and upper lateral nasal fistula afterurgery and radiotherapy for malignant lesions.27 Ad-itionally, the pericranium has been used for multipleeriorbital defects, including eyelid reconstruction,edial orbital reconstruction, and orbital reconstruc-
ion.28-30 Multiple other applications for this versatileap exist including a reliable means for mastoid oblit-ration after radical temporal bone surgery for cho-esteatoma,31 augmentation of soft tissue defects,32
nd repair of congenital defects.33
Despite the widespread use of the pericranial flapn reconstructive surgery of the craniofacial skeletonnd face, little is known regarding the reliability of thelood supply of this flap. Most of the literature regard-
ng the blood supply of the pericranial is ex vivo,nvolving vascular injection studies with cadaveric
eliability of the blood supply of the pericranium is anmportant clinical consideration because the pericra-ium may be used as a free graft or a pedicled flapepending on the reconstructive application or the sur-eon preference. If the flap is vascularized, it could beuggested that pericranial flaps should be designed as aedicled flap whenever possible to preserve the bloodupply to this versatile tissue during reconstructiverocedures. The purpose of this study is to examinehe blood supply of pericranial flaps with real-time, inivo, laser Doppler flowmetry during reconstructiveurgery and, additionally, to attempt to determine thepproximate length of flap, which maintains its vas-ular supply after surgical dissection during recon-tructive procedures.
atients and Methods
PATIENTS
Ten patients requiring coronal exposure to treatraniofacial/midfacial fractures were offered the op-ortunity to participate in this Institutional Reviewoard-approved study. Patients had to be 18 years ofge and in good general health, with no prior historyf diabetes, hypertension, or other vascular diseases.moking was not an exclusionary criterion. The skinf the forehead and scalp had to be intact without
aceration or contusion.
PROCEDURE
The proposed line of the coronal incision was markedith a surgical pen. A small amount of vasoconstrictor
1:100,000 epinephrine) was injected subdermallylong the proposed incision line. No vasoconstrictoras used subgaleally. The coronal incision was carried
hrough the skin, subcutaneous tissue, and galea. Su-raperiosteal (subgaleal) dissection in the loose sub-aleal areolar tissue to the supraorbital rims was per-ormed with a No. 10 blade taking care to not injurehe pericranium. Incisions through the pericraniumere then made just medial to the superior temporal
ines, extending from the supraorbital rims bilaterallyo the posterior extent of the coronal incision. Aoronal incision through the pericranium was thenade at the posterior extent of the exposure from 1
uperior temporal line to the other, creating an ante-iorly pedicled flap of pericranium.34 Subpericranialissection of the flap was then performed with peri-steal elevators, taking care to not injure or perforatehe flap.
The flap was then draped over a saline-soaked darklue surgical towel to remove the influence of under-
ying skeletal bone blood flow on laser-Doppler flow-etry measurements in the flap. Pericranial flaps
ere on average 12 to 15 cm in length from the h
upraorbital area to the posterior edge of the flap. Aaser-Doppler flow probe was placed directly on theurface of the flap (Fig 1). Three separate laser-Dop-ler flow measurements were then taken at the prox-
mal (near flap attachment), middle, and distal areas ofhe flap for approximately 2 minutes each to deter-ine the extent of blood flow at these sites. Distanceeasurements from the supraorbital area (origin of
he flap) to the position of the laser-Doppler probeere recorded.
INSTRUMENTATION
Data were continuously acquired at a sampling ratef 50 Hz using a data collection system (Biopac Sys-em, Santa Barbara, CA). Heart rate was obtained fromn electrocardiogram (Datex Ohmeda, Helsinki, Fin-and). Laser-Doppler flux (index of blood flow) fromhe pericranial flap was measured using an integratingaser-Doppler flowmetry probe (MoorLAB laser Dopp-er Perfusion Monitor; Moor Instruments, Wilming-on, DE). This probe continuously measures bloodow over a relatively small area (�0.28 cm2). Laser-oppler flowmetry derives an index of blood flow
rom both the velocity of blood in vessels and aoncentration component, which is a derivation ofhe number of photons that are Doppler shifted. Thentegrating laser-Doppler flow probe continuously
easured blood flow over a small area (�0.28 cm2).
DATA ANALYSIS
Fast Fourier transformation was performed on theaser-Doppler flux to convert this index of blood flown its frequency components (AcqKnowledge; Biopacystem). Given that blood flow detected by laser-oppler flowmeter exhibits cardiac rhythmicity, theresence of blood flow at a particular site was iden-ified by the observation of a peak in the laser-Dopplerignal that occurred at the same frequency as theeart rate signal obtained from the electrocardiogra-hy (Fig 2). The presence of blood flow at a given siteas confirmed if the peak of the spectrum at the
orresponding heart rate frequency was a minimumf 5 times the size of the “noise” (ie, 5:1 signal-to-oise ratio) occurring at a frequency outside the typ-
cal heart rate (ie, 2.0 to 3.0 Hz).
esults
The demographics of the 10 patients enrolled arehown in Table 1. During surgery, it was noted thathere was great variability in the thickness of the flapsmong patients. Some patients’ pericranial flaps werextremely thin, seemingly devoid of any blood sup-ly, and one was so transparent that newsprint coulde read through it. Others were thicker and seemingly
ad more blood supply. The results of the fast Fourier
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1742 LASER-DOPPLER EXAMINATION OF BLOOD FLOW
ransformation of the laser-Doppler data are summa-ized in Table 2. Blood flow was detected in the flapsn all but 1 patient (patient 10). This patient had a veryhin pericranial flap. It is interesting to note that iflood flow was identified near the flap attachmentproximal site), with the exception of 1 patient (pa-ient 6), it was also identified at all distal locations ofhe flap.
iscussion
The success of the pericranial flap in reconstruc-ion has been attributed to its “reliable” or “robust”lood supply in the literature. However, studies in-estigating this blood supply are relatively rare in theiterature, especially given the extensive literature re-orting the various uses of the flap in reconstruction.ost studies that have looked at the vascular supply
o this area have looked at the tissues before dissec-ion, or for the pericranial flap, before dissection ofhe galea and elevation from the skull. This study hashown that the pericranium, when elevated as a pedi-
IGURE 2. Recording of patient’s electrocardiograph (above) andaser-Doppler signal in the pericranial flap (below). Note that the 2re temporally related.
iles et al. Laser-Doppler Examination of Blood Flow. J Oralaxillofac Surg 2010.
IGURE 1. Laser-Doppler probes in A and B. C, Intraoperativehotograph showing probe resting on pericranial flap. Note the 2ilk sutures used to stabilize the probe.
led flap, is in fact vascularized. The origin of the
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lood supply was not evaluated in this study, but thelood supply to the nondetached pericranium arisesrom terminal branches of the internal and externalarotid arteries, namely the supraorbital and supratroch-ear vessels arising from the ophthalmic (internal), as
ell as branches from the superficial temporal vesselsaterally (external). These terminal branches form a vas-ular network that supplies the galeopericranial tis-ues.17,35,36 The finding of a blood supply to the ele-ated pericranium may explain why reconstructiverocedures involving use of the pericranium have beenxtremely successful; this flap has found widespread usen the literature.7,12-14,16,28,35
Habal and Maniscalco harvested fresh pericraniumuring craniofacial procedures and examined the ul-rastructure of the pericranium using light and elec-ron microscopy.37 Examination showed an outer
Table 1. SUBJECT CHARACTERISTICS
Patient Gender Age Race
1 Male 53 Caucasian2 Male 23 Caucasian3 Female 39 African American4 Male 27 Hispanic5 Female 29 Caucasian6 Female 20 Caucasian7 Male 29 African American8 Male 39 Caucasian9 Male 54 African American
10 Female 33 Hispanic
bbreviations: MVC, motor vehicle collision; GSW, gun sho
iles et al. Laser-Doppler Examination of Blood Flow. J Oral Ma
An indication of flow could not be determined for the middignal and frequency spectrum.An indication of flow could not be determined for the midap that occurred during dissection from the skull.
iles et al. Laser-Doppler Examination of Blood Flow. J Oral Maxillofa
oose fibrillar layer composed of flat spindle-shapedells, and a dense vascular inner layer adjacent to theeriosteum containing the osteoblasts of the pericra-ium. It is within this inner layer that a network ofessels was observed, and the authors felt this vascu-ar layer accounted “for the ability of the pericranialayer to be used as a flap based on a narrow pedicle.”
ultiple cadaver studies have confirmed that the ter-inal branches of the supratrochlear and supraorbital
essels separated into a superficial system, which sup-lies the galea, frontalis muscle, and skin, and a deepystem supplying the pericranium.12,13,32,33 Horowitzt al studied cadavers via latex vascular studies thathowed the blood supply to the pericranium as aich vascular network from deep peripheral axialessels as well as perforating vessels from the over-ying galea.17
tion of patient 5 due to excessive noise in the laser-Doppler
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1744 LASER-DOPPLER EXAMINATION OF BLOOD FLOW
Although the blood supply to the galeopericraniumas been shown to predominate in an axial pattern,he distance of reliable blood supply from the aboveoted terminal branches remains unknown. In fact,he reliability of the blood supply of the distal peri-ranium has been questioned in the literature. Severalnvestigations have shown that the predominant sup-ly to the forehead region is the supratrochlear arteryather than the supraorbital artery. More importantly,oth the supratrochlear and the supraorbital arteriesave been shown to pierce the frontalis muscle at the
evel of the brow and travel distally within the subcu-aneous tissue. Therefore, the pericranial flap, whichies deep to the galea, does not contain significantxial branches of these vessels.16,25,38
Several investigations have attempted to examinehe length of the vascularized portion of the pericra-ial flap. Potparic et al noted in a cadaveric study thatue to the small size of the distal axial vessels andheir poorly developed internal anastomosis, the por-ion of the pericranial flap distal to approximately 4m from the base of flap should be considered non-ascularized.35 These authors noted that use of moreistal portions of these flaps should be undertakenith caution. They also observed that moderate in-
rease in bulk and vascularity may be achieved if aap is harvested as a composite galeal-frontalis-peri-ranial flap. They concluded that “due to the vascularnd volume limitations of galeopericranial flaps, con-ideration should be given to the use of microvascularree tissue transfers in instances where large soft tis-ue defects or large dead space occur.” Fukuta et alerformed a cadaveric investigation to study the
ength limit of the pericranial flap by injecting latexye in the vascular system of the pericranium, and theuthors showed no significant reliable axial supply tohe pericranium beyond 4 cm from the margin of therbital rim.38 This was because deep branches of theupratrochlear and supraorbital arteries showed anxial distribution on the periosteum only for a shortistance. The authors noted that by dissecting in anrtificial subcutaneous plane, preserving the galea inontinuity with the pericranium, the axial supply ofhe pericranium may be preserved to approximately 8o 12 cm from the orbital rims. This finding wasonfirmed by Yoshioka et al in 2 cadaver studiesxamining the vascular supply of the anteriorly basedericranial flap.12,39 The microscopic evaluation ofhe microvascular supply to the pericranium showedhat approximately 30% of the arterial supply, andpproximately 40% of the venous drainage, would beevered by separating the pericranium from the galea-rontalis muscle layer. The authors reported that sep-ration of the galeafrontalis muscle layer from theericranium should not be performed beyond 10 mm
bove the supraorbital rim to preserve the arterial and
enous pedicle of the pericranial flap. The results ofur study clearly show indications of blood supplyven distally. However, quantification of blood flowie, in mL/min) is not possible with the methodologysed.It should be pointed out that laser-Doppler record-
ngs performed in this study were performed underdeal circumstances without tension on the flap dur-ng the recordings. The flap was not folded or kinkednd was simply laid out flat in its original orientation.his is not the case when pericranial flaps are usedlinically, as they are often folded, passed through aony opening, wrapped around a bone graft, etc. It iseasonable to assume that such manipulations wouldause a decrease in the flow of blood through theelicate vasculature with these flaps. The presence oflood in the distal portions of such flaps is thereforeot known. However, given their positive clinicalutcomes, it is probable that some blood supply re-ains. The vascularity provides the basis for the reli-
bility and clinical versatility of the pericranial flap.
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