Cambios en flujo sanguíneo Le Fort I

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Changes in bone blood flow in segmental LeFort I osteotomies

Winfried Bernhard Kretschmer, MD, DDS,a Grigore Baciut, MD, DDS, PhD,b

Mihaela Baciut, MD, DDS, PhD,c Werner Zoder, MD, DDS,d and

Konrad Wangerin, MD, DDS, PhD,e Stuttgart, Germany, and Cluj-Napoca, RomaniaMARIENHOSPITAL AND UNIVERSITY OF MEDICINE AND PHARMACY IULIU HATIEGANU

Objective. The aim of the present study was to investigate the effect of segmentation and different movements of thesegments in LeFort I osteotomies on the bone blood flow (BBF).Material and methods. The study sample of the prospective cohort study was composed of subjects scheduled toundergo 3-piece LeFort I osteotomies and simultaneous BSSO for correction of developmental skeletal deformities. Theprimary predictor variables were: time (T1, before LeFort I osteotomy; T2, after LeFort I osteotomy; T3, aftersegmentation and fixation of the maxilla) and magnitude of maxillary movement in the sagittal, vertical, and transverseplanes measured in millimeters (mm). The subjects were assigned to 2 risk groups (high/low) depending on the amountof the movement. The primary outcome variable was maxillary bone blood flow measured with a laser Doppler at 4sites: premaxilla, right and left maxillary lateral segments, and the mandible.Results. No significant difference was observed among the 3 maxillary regions. The mean decrease of the maxillaryBBF between T1 and T2 as well as the reduction of BBF between T2 and T3 were statistically significant for all regions

(P .028 to P .005 for T1/T2; P .003 to P .028 for T2/T3). No significant difference could be found betweenthe 2 risk groups of maxillary movements.Conclusions. Multisegmental maxillary osteotomies lead to a significant reduction of BBF. Moderate maxillarymovements have no significant influence on the blood supply. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod2009;108:178-183)

Multisegmental Le Fort I osteotomy is a standard pro-

cedure in orthognathic surgery. The reestablishment of

a blood supply to the dento-osseous segments was

shown by Bell et al.1,2 in animal studies on macaque

monkeys. Yet, a significant reduction in perfusion ofthe dento-osseous segments has been observed during

the first hours after surgery.1-7 Thus, adverse sequelae

can occur, such as pulp changes, nonunion of the bone,

and partial or complete loss of segments. Thirty-six

cases of aseptic necroses were described by Lanigan

and West.8 Expansion of the segmented maxilla and

superior repositioning seem to exhibit the highest risk

for this kind of complication.8,9 Emshoff et al.10,11 have

shown that segmentation leads to a reduction of pulpal

blood flow (PBF) after LeFort I osteotomy. Expansion

or specific movements of the maxilla were not quanti-fied. So far, no study has been performed on the effect

of expansion, advancement, or vertical repositioning on

the bone blood flow in the dento-osseous segments.

Laser Doppler flowmetry has been described to be a

reliable method for continuous measurement of pulpal

or gingival blood flow in orthognathic surgery. Intra-

operative recording of gingival blood flow (GBF) dur-

ing Le Fort I osteotomies was done by Dodson et

al.12-14 Studies on bone blood flow (BBF) with laser

Doppler flowmetry in orthognathic surgery are not

known. The current study was designed to evaluate the

effect of segmentation, intraoperative expansion, ad-vancement, and vertical repositioning on BBF of pre-

maxilla and lateral segments during multisegmental Le

Fort I osteotomies.

MATERIAL AND METHODS

Study design and sampleA prospective cohort study was designed to investi-

gate the effect of segmentation and magnitude of max-

illary movement in the sagittal, vertical and transverse

planes on BBF of the maxilla. The study sample was

composed of subjects scheduled to undergo 3-piece

aSenior Registrar, Department of Oral and Maxillofacial Surgery,

Marienhospital, Stuttgart, Germany; PhD Student, University of

Medicine and Pharmacy Iuliu Hatieganu, Cluj-Napoca, Romania.bProfessor and Chair, Clinic of Cranio-Maxillofacial Surgery, Uni-

versity of Medicine and Pharmacy Iuliu Hatieganu, Cluj-Napoca,Romania.cAssociate Professor, Clinic of Cranio-Maxillofacial Surgery, Uni-

versity of Medicine and Pharmacy Iuliu Hatieganu, Cluj-Napoca,

Romania.dSenior Registrar, Department of Oral and Maxillofacial Surgery,

Marienhospital, Stuttgart, Germany.eProfessor and Head of the Department, Department of Oral and

Maxillofacial Surgery, Marienhospital, Stuttgart, Germany.

Received for publication Feb 23, 2009; returned for revision Apr 4,

2009; accepted for publication Apr 16, 2009.

1079-2104/$ - see front matter

2009 Published by Mosby, Inc.

doi:10.1016/j.tripleo.2009.04.029

178


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LeFort I osteotomies and simultaneous bilateral sagittal

split osteotomy (BSSO) for correction of developmen-

tal skeletal deformities. Inclusion criteria were the fol-

lowing: fixed orthodontic appliances, availability of a

sterilized probe (the laser probes had to be sent outside

the hospital for gamma sterilization), a sufficient bone

thickness of the measurement areas, and a clinicalpostoperative follow-up of at least 6 weeks. Patients

with previous surgery in the maxilla (e.g., cleft palate,

rapid maxillary expansion) or general diseases (non

class I according to the American Society of Anesthe-

siology) were excluded. The protocol was reviewed and

approved by the institutional review board. Each sub-

ject has given a written informed consent.

Study variablesThe predictor variables were time, direction, and

magnitude of maxillary movement and location of

blood flow measurement. BBF (outcome variable) was

measured after incision of the upper and lower vesti-

bule and soft tissue dissection (T1), after Le Fort I

osteotomy and mobilization of the maxilla (T2) and

after segmentation and fixation of the maxilla (T3).

Direction and magnitude of maxillary movement were

planned with the Onyxceph software 2.7.15 (Image

Instruments GmbH, Jena, Germany). The following

landmarks were used for the study: upper incision (hor-

izontal movement) and mesial cusp of the first molar

(vertical movement). The movements are given in re-

lation to the Frankfurt horizontal plane. Widening of

the maxillary dental arch was measured for the first

molar on the dental casts before and after model sur-

gery. The subjects were assigned to 2 risk groups.

Advancement, superior repositioning, and widening of

2 mm and more were considered a risk. The high-risk

group included subjects with 2 or 3 movements at risk,

whereas the low-risk group included subjects with only

1 or no movement at risk. The locations of BBF mea-

surement were premaxilla, right and left lateral segment

of the maxilla, and mandible (control measurement).

Other collected variables included age and gender.

Anesthesia and surgical techniqueAll patients received hypotensive anesthesia. Stan-

dardized Le Fort I and sagittal split osteotomies with

rigid fixation were performed according to Bell and

Proffit15 and Hunsuck.16 Tissue perfusion was opti-

mized by administration of 500 mL of hydroxyethyl

starch 6%/200/0.5 before segmentation of the maxilla;

this bolus infusion was repeated after 8 and 20 hours.

Segmentation of the maxilla was done between the

lateral incisor and the canine on both sides with appro-

priate burrs. The maxilla was operated on first in all

cases. The maxillary segments were stabilized with

2.0-mm miniplates and an interocclusal splint.

Blood flow measurementA laser Doppler flowmeter (Periflux PF 5001, Per-

imed, Jrflla, Sweden) was used to assess the BBF in

the maxilla and the mandible. Light with a wavelength

of 632.8 nm is produced by a 1-mW He-Ne laser.

Custom-made probe holders (Perimed) were fixed in

the premaxilla, both canine regions and the mandible

(anterior to the planned sagittal split) through 1.9-mm

burr holes in the cortical bone (Fig. 1). The measure-

ment in the mandible served as a control. A custom-made probe (PF 415-310, Perimed) (Fig. 2) was used to

conduct the light to the measurement site in the can-

cellous bone and to return the backscattered light to the

flowmeter. The probe had a diameter of 1 mm. The

optical fiber had a diameter of 125 m; the fiber-to-

fiber distance was 500 m. According to the Doppler

effect, the amount of backscattered light is recorded by

the flowmeter. The voltage of the produced output

signal has a linear relation to the flow of the red blood

cells (number of cells average velocity). The perfu-

sion units (PU) shown by the laser Doppler are a

relative measurement of the blood flow in the respec-tive tissue. The data were collected on a wide band

setting. A computer was connected to the RS-232 port

of the laser Doppler for storage of the date and later

analysis with the specific software (PeriSoft for Win-

dows, Perimed). Reproducibility of the measurements

was ensured with the fixed probeholder. Calibration of

the probes was done before each sterilization process

with a plastic block for zero voltage and a motility

standard for 250 PU (Perimed). For each site the data

were registered continuously until at least 2 minutes of

stable values were seen on the screen.

Fig. 1. Probe holder fixed into the maxillary bone (premaxilla

and lateral segments) intraoperatively.

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Volume 108, Number 2 Kretschmer et al. 179


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Data analysisFor the analysis of the recordings, the PeriSoft for

Windows software was used. The mean perfusion was

calculated for each session during the phase of stablevalues. Peaks attributable to movement artefacts were

excluded. Further data analysis was done with the Sta-

tistica 8.0 software (StatSoft Inc., Tulsa, OK). Perfu-

sion changes of the mandible, the premaxilla, and the

lateral segments between the respective sessions were

investigated with the Wilcoxon matched pairs test. The

Friedman analysis of variance (ANOVA) was used to

detect differences among the 3 maxillary regions within

every session. To compare the results with those of other

studies, the percentage of BBF reduction was calculated

for the 3 maxillary regions. Differences between the 2 risk

groups at T2 and T3 were analyzed with the Kruskal-Wallis ANOVA by ranks. A probability ofP less than .05

was considered significant.

RESULTSTwelve patients undergoing bimaxillary osteotomies

with 3-piece maxilla from April 2008 to February 2009

were included in the study. Two patients were excluded

from the study, because maxillary blood flow measure-

ment was not possible in the lateral segments because

of extremely thin bone. Mean, standard deviation, and

range of the study variables are given in Table I. Seven

patients were included in the high-risk group, whereas

5 patients were assigned to the low-risk group (Table

II). No anesthetic or surgical complications were ob-

served during surgery. The descending palatine artery

was preserved in all cases. Means, standard deviations,

and ranges of all measurement sites and time points are

shown in Table III. The mandibular perfusion showed

no significant differences between the recording ses-

sions T1/T2 (P .071) and T2/T3 (P .875). No

significant differences could be found between premax-

illa, right and left lateral segment at T1 (P .338), T2

(P .920), and T3 (P .368). A significant reductionof BBF was observed between T1 to T2 in the right

lateral segment (P .028), the premaxilla (P .028),

and the left lateral segment (P .005). Between T2 and

T3 a further significant decrease of perfusion was seen

in the right lateral segment (P .028), the premaxilla

(P .003), and the left lateral segment (P .008)

(Table III). The mean percentage of BBF reduction at

the end of the maxillary procedure (T1/T3) was 63.3%

(SD 18.54) in the premaxilla, 45.5% (SD 44.27) in the

right lateral segment, and 60.7% (SD 18.63) in the left

lateral segment. No significant differences could be

Table I. Study variables (n 12; 7 male, 5 female)

Variable Mean SD Range

Age 22.5 4.25 16 to 31

Maxillary advancement, mm 1.6 1.16 0 to 3

Vertical movement first molar, mm 2.4 3.02 7 to 2

Expansion first molars, mm 1.5 1.90 1 to 4.5

Table II. Risk groups for decrease of bone blood flowin segmental LeFort I osteotomies: high (n 7) and

low (n 5)

Patient Advancement Vertical movement Expansion Risk group

1 2 2.5 4 High

2 3 7 0 High

3 1 1 3 Low

4 1 2 1 Low

5 1 1 0 Low

6 3 4 3 High7 0 4 2 High

8 1 6 0 Low

9 3 1 3 High

10 0 2 0 Low

11 3 3 0 High

12 1 5 4.5 High

Advancement, superior repositioning, and expansion of 2 mm or

more were considered a risk.

Subjects with 2 or 3 movements at risk were assigned to the high-risk

group.

Fig. 2. Laser Doppler probe (PF 415-310, Perimed, Jrflla,

Sweden) for measurement of bone blood flow (BBF).

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180 Kretschmer et al. August 2009


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found between the 2 risk groups at T2 and T3 (Table

IV). Postoperatively, no avascular sequelae were seen.

DISCUSSION

Avascular necrosis is a possible sequelae of a com-promised blood supply to the dento-osseous segments

in multisegmental Le Fort I osteotomies.8,9 Lanigan

and West8 reported 36 cases with aseptic necrosis fol-

lowing maxillary osteotomies. Of these 36 cases, 34

were multisegmental osteotomies. Basic research on

the BBF after different osteotomies of the maxilla was

done by Bell et al.,1,2 Nelson et al.,3 and Meyer and

Cavanaugh4 on macaque monkeys. As it is not possible

to use radioactive microspheres for clinical research in

humans, laser Doppler flowmetry has shown to be the

method of choice for blood flow measurements in or-

thognathic surgery.5,10-14,17-24

The work of Firestone etal.,17 Buckley et al.,18 and Hellem et al.25 confirmed its

reproducibility. Emshoff et al.10,11 have shown the de-

crease of pulpal blood flow 3 to 5 days after segmental

maxillary osteotomies. Although it is known that the

highest reduction of maxillary perfusion can be found

during the first hours after Le Fort I osteotomy,1-7 few

data have been published about the intraoperative dy-

namics of maxillary blood flow.12-14 Superior reposi-

tioning and transverse expansion seem to be a potential

risk for vascular impairment.8,9 So far, no research has

been reported on the correlation between different max-

illary movements and the drop of maxillary blood sup-

ply in multisegmental osteotomies.

To investigate the effects of orthognathic surgery on

maxillary blood supply, research has mainly been done

with laser Doppler assessment of pulpal (PBF) and

gingival blood flow (GBF).5,10-14,17,18,22-24 This has

some disadvantages: orthodontic treatment has shownto have an effect on PBF5,17 as well as the distance of

the subapical osteotomy to the apex.24,26 Injuries of the

teeth during surgery will certainly have an influence on

PBF. Furthermore, positioning of the probes with cus-

tom-made wafers, as done by most authors,10,11,19-23 is

difficult intraoperatively, especially in cases with seg-

mentation of the maxilla. Measurement of BBF with

laser Doppler flowmetry has been developed for the

control of free flaps.27-29 Animal studies have shown

the reliability of this method.25,27,30-32

The intraoperative decrease of maxillary perfusion

found in the present study was up to 95% in certainareas of the maxilla. This is comparable to the animal

study of Nelson et al.3 with radioactive microspheres.

They found a decrease of BBF up to 89% when the

descending palatine artery (DPA) was cut. The DPA

was not, however, severed in any case of the present

study. The role of the DPA is not clear. Dodson and

Bays12 did not find a significant difference between 2

groups with and without ligation of the DPA when

measuring gingival blood flow intraoperatively. In con-

trast to this, Ramsay et al.23 reported 2 mild avascular

complications in a sample of 14 patients. Both under-

went a 2-piece Le Fort I osteotomy with expansion andhad 1 descending palatine artery transected. They have

not found significantly lower perfusion values in these

cases measuring 1 to 6 days after surgery. This con-

firms the importance of intraoperative assessment as

proclaimed by Dodson et al.12-14 It is not clear when to

classify a decrease of perfusion as adverse outcome. In

a recent study, Emshoff et al.10 defined a reduction of

PBF of more than 40% as adverse; 64% of their sub-

jects with multisegmental maxillary osteotomy and

32% of those with single-piece Le Fort I osteotomy

showed an adverse outcome 3 to 5 days after surgery.

Table III. Regional bone blood flow measurements (n 12) in perfusion units (PU)

Region

T1 T2 T3

Mean (SD) Range Mean (SD) Range Mean (SD) Range

Mandible 59.7 (44.8) 12.9-151.6 40.5 (30.2) 9.1-99.6 44.4 (34.6) 7.9-115.6

Maxilla:

Right lateral segment 77.5 (63.4) 12.7-210.3 46.8 (40.0) 5.1-139.2* 34.7 (41.8) 1.4-145.9*

Left lateral segment 79.6 (30.6) 19.5-112.3 41.1 (20.5) 13.8-75.5* 30.5 (19.4) 4.1-67.0*Premaxilla 70.6 (31.9) 24.8-121.8 47.5 (35.1) 13.0-105.1* 22.8 (15.4) 3.5-52.8*

T1, before LeFort I osteotomy; T2, after LeFort I osteotomy; T3, after segmentation and fixation of the maxilla.

*Significant difference to the previous session (P .05) in the Wilcoxon matched pairs test.

Table IV. Comparison of the maxillary bone bloodflow between the high-risk group (n 7) and the

low-risk group (n 5) at T2 and T3 (P values)

Region T2 T3

Right lateral segment 0.685 0.935

Left lateral segment 0.570 0.935

Premaxilla 0.223 0.168

Kruskal-Wallis analysis of variance by ranks.

T2, after LeFort I osteotomy; T3, after segmentation and fixation of

the maxilla.

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Information about clinically observed avascular se-

quelae was not given. We observed a mean intraoper-

ative BBF reduction in the maxillary regions between

45.5% and 63.3% after segmentation and fixation.

Avascular complications were not seen. Dodson and

Bays,12 Harada et al.,19,20 and Sato et al.21 reported

similar results. The drop of GBF after downfracturewas greater than 70% in both study groups (with and

without DPA ligation) of Dodson and Bays.12 For both

groups, a reduction of over 60% was found at the end

of the procedure. PBF decreased by more than 80% 1

day after surgery in the studies of Harada et al.19,20 and

Sato et al.21 None of these authors reported avascular

sequelae. Segmentation of the maxilla with superior

repositioning and expansion is reported to be one of the

main factors for avasular necrosis.8,9 Epker9 mentioned

a risk of avulsing portions of the palatal pedicle,

when expanding the maxilla more than 3 to 5 mm.

Lanigan and West8

reported maxillary widening up to15 mm in one study about 36 cases exhibiting aseptic

necrosis. In a study of Poswillo33 on Old World mon-

keys with open bite, 10-mm advancement of the pre-

maxilla led to irreversible pulp changes. Animal studies

with not more than 2 mm repositioning of the segments

have not shown permanent effects.1,2,6,24,25,34 No data

can be found concerning the correlation between ver-

tical maxillary movement and decrease of blood sup-

ply. Advancement, vertical repositioning, and expan-

sion of the maxilla did not have a significant influence

on BBF in the present study. The moderate maxillary

movements and the relatively small sample might bereasons for these findings. As the supposed limit of

expansion should not be exceeded in humans for ethical

reasons, further animal studies are needed. Intraopera-

tive measurement of BBF should be continued to in-

vestigate the effect of vertical repositioning, widening,

and advancement with larger samples. Thus, regression

analysis for single factors will be possible. Monitoring

of critical dento-osseous segments, e.g., in patients with

cleft palate and previous surgery, is a possible indica-

tion for routine clinical application of the technique.

We thank Dr. Sorana-Daniela Bolboaca, M.S., M.D., Ph.D.,

Department of Biometry, University of Cluj-Napoca, for

help with the statistical analysis.

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Reprint requests:

Winfried Bernhard Kretschmer, MD, DDS

Department of Oral and Maxillofacial Surgery

Marienhospital Stuttgart

Boeheimstr. 37

70199 Stuttgart, Germany

[email protected]

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mailto:[email protected]:[email protected]

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Cambios en flujo sanguíneo Le Fort I