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Laser Doppler imaging of axial and random pattern flaps in the maxillo-facial area. A preliminary report
.lnurnnl n f (~ranio-Mn~cilla-Faeiat Sure, Pry 11994] 22 301 306
Laser Doppler imaging of axial and random pattern flaps in the maxillo-facial area. A preliminary report Wolfgang Eichhorn 1, Thorsten Auer 2, Ernst-Dieter Voy 1, Klaus Hoffmann2
1Department Maxillofacial Surgery, (Head." Pr@ Dr Dr E.-D. Voy), EvangeIisches Krankenhaus Hattingen, Bredenscheiderstrafle 54, 45525 Hattingen. 2Dermatological Clinic, (Head: Prof. Dr P. AItmeyer), Ruhr-Universitiit Bochum, Germany
SUMMARY. Objective, non-invasive examination, techniques in addition to clinical parameters, are required to follow-up the wound healing of flaps. With the new laser Doppler Scanner (LDI DIM 1.0 Lisca Development AB, Sweden) it is possible, for the first time, to measure and image the microcirculation continuously, non-invasively and without contact with the wound, in an area of 12 cm square maximum. We performed measurements and simultaneous two-dimensional imaging of the microcirculation 24, 48, 72 h and 5 and 14 days postoperatively in 20 patients, who had had reconstruction procedures performed using random or axial pattern flaps. The perfusion diagrams were correlated to the clinical appearance. Necrotic areas, venous stasis and normal course of wound healing can be clearly visualized and differentiated from one another. The new laser Doppler imaging system seems to be an excellent aid for following up and planning of flaps in plastic and reconstructive surgery. INTRODUCTION
measuring depth of 300 to 500 micrometres we find the papillae of the dermis and the upper horizontal plexus underneath the epidermis, with a thickness of 100 micrometres. The laser beam is guided in a random pattern over a defined area with the help of a reflecting system controlled by two stepping motors. The size of the test area is defined by the distance of the scanner from the skin surface and by the variable density of the sites measured. The test distance between the scanner probe and the skin surface was 15 to 20 cm. The perfusion image recorded by the laser Doppler imaging (LDI) is made up of 4096 measurement points. The laser signal reflected from a moving red blood cell is registered by a photo detector. The intensity of the light signal is transformed into an electrical signal in volts and transmitted to a signal processor (Fig. 1). During the taking of measurements, irregularities of the skin surface being examined can lead to a change in the distance of the skin from the detector and in the detector-to-laser angle. The resulting positional signal deviation is compensated for with the aid of a correctional algorithm. Image processing occurs concomitantly with the measurements so that an evaluation can be performed immediately. Perfusion values are coded on a six colour scale from blue, meaning low flow, through green and yellow to red, indicating a high flow.
Objective and non-invasive examination techniques, in addition to clinical parameters, are required to study the course of wound healing of flaps. Laser Doppler ftowmetry constitutes a relatively new method for microcirculatory blood flow studies in human skin and in other tissues, e.g. bone, muscle (Stern, 1975; Nilsson et al., 1980; Shepard et al., 1987, 1990; Tenland et al., 1993). A two-dimensional imaging system, as it effects an entire area, has only recently become available. The aim of the following study is to evaluate the possibilities and limits of this new twodimensional imaging system. MATERIALS AND METHODS The course of wound healing was studied in 20 patients who had had reconstruction procedures performed. In 7 cases it was an axial pattern and in 13 cases a random pattern flap. The period of study was chosen to be 14 days. Their ages ranged between 16 and 88 years (mean age 59 years). For diagnosis, size and type of flap, see the Table. All measurements were performed in the dark to avoid interference by visible light, after the patient was acclimatized to this situation for half an hour, in a prone position. Measurements were performed at 24, 48, 72 h and 5 and 14 day postoperatively. The laser Doppler Perfusion Imager, PIM 1.0 (Lisca Development Link6ping Inc., Sweden), was used for laser Doppler scanning, utilizing the Doppler shift of the laser light as the information carrier. The heliumneon laser beam has a wavelength of 632.8 nm with a measuring depth of 300 to 500 micrometres. At a
RESULTS The value of the two-dimensional laser Doppler system for imaging the microcirculation of flaps is demonstrated, for example, by the following clinical case.
301
302
Journal of Cranio-Maxillo-Facial Surgery
Table - Number of patients, diagnosis, localization, type and size of flap Site
Type of flap
Nose
Axial
12 x 6
Front
Axial
12 x 8
Front
Axial
10 x 6
Front
Random
3x5
Nose
Axial
1x 4
Nose
Random
3x3
Nose
Random
2.5x3
Front
Axial
4x7
Nose
Random
5x3
Cheek Upper lid
Random Random
5x 2 3x 1
M. Bowen
Neck
Basal cell carcinoma Spinalioma Trauma Cleft lip Basal cell carcinoma Basal cell carcinoma
Nose
Random Random
3x2 4x2
Neck
Random Axial Axial Random
1x 1x 2x 2x
Cheek
Random
2x6
Random
3x2
Random
4x8
Name
Age
Diagnosis
P.C.
51
K.I.
48
U.F.
64
S.W.
88
C.B.
63
G.K.
66
P.B.
72
G.H.
56
O.P.
76
H.G. E.F.
55 45
Lentigo maligna Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Spinalioma Basal cell carcinoma
H.B. B.W.
71 75
T.W. L.B. F.M. R.C.
68 21 16 84
G.R.
55
H.A.
52
M.B.
62
Upper lid Upper lip Upper lip
Upper lip carcinoma FibrosarNeck coma Ba~al cell
Size of flap (cm)
3 3 1 3
(Fig. 2A). Immediately after tumour resection we implanted a skin expander underneath the frontalis muscles to expand the skin of the forehead (Fig. 2B). On the first postoperative day, LDI showed a wide hypercirculatory area at the recipient site and a small hyperperfused zone on the flap edges. The small light blue zone represents an artefactual area, indicating that no laser Doppler shift of an erythrocyte could be recorded. This can be due to exudation from the wound that had dried on the skin and is a barrier to the laser light, or that there is no microcirculation in this section of the flap. We focus on the fact that the most distant point of the flap has the best perfusion (Fig. 3). On the second day we see a smaller hypercirculatory area at the recipient site. At one point there seems to be a bridging as a sign of commencing neogenesis of vessels. On the fifth day the hyperaemic Zone at the recipient site is again smaller and we detect multiple green points located from the border to the middle of the flap as a sign of perfusion changing from the axial artery to nutrition from the margins (Fig. 4). We encouraged the neogenesis of vessels by controlled interruptions of blood circulation. LDI during interruption reveals that the furthest point to be perfused is now close to the eyelid. We see a gradient of perfusion with a maximum at the former border and a minimum close to the clamp, which produces an artefactual zone due to pressure (Fig. 5). On the twelfth day we cut the frontal flap and remodel the forehead and nose. The hyperaemic area in the right upper corner on the LDI corresponds to the left eye. We can see a small artificial zone at the lower eyelid. The flap is perfused in toto. The LDI and the clinical appearance are in accordance (Fig. 6).
CASE REPORT Tlais 63-year-old woman suffered from a lentigo maligna of the nose, nasolabial fold and lower eyelid
He-Ne Laser
Scanner.Head: -Mirror-System .Step-Motors -Preamplifier
~ Photodetector
1
Processor A-D-Board
[ Plotter .,~J
t[ Data.Analysis]
Fig. 1 - Diagram of the laser Doppler scanner for laser Doppler imaging.
LDI of axial and random pattern flaps in the maxillo-facial area
A
303
B
Fig. 2 - (A) This 63-year-old woman suffered from a lentigo maligna of the nose, nasolabial fold and lower eyelid. (B) The frontal flap is partly elevated with the skin expander lying underneath the frontalis muscles.
A
B
Fig. 3 (A) On the first postoperative day a light blue elliptic zone in the right lower corner representing the nostril can be observed. The dark blue area is the surface of the wound. A wide hypercirculatory red area can be seen on the flaps edge and at the recipient site. (B) The frontal flap is raised and transposed into the nasal defect.
DISCUSSION P o s t o p e r a t i v e l y , w e o b s e r v e d a h y p e r a e m i c z o n e at t h e r e c i p i e n t site a n d a s m a l l e r h y p e r c i r c u l a t o r y a r e a o n t h e flap e d g e s t h a t is r e g r e s s i n g o v e r a t w o w e e k
p e r i o d . W e i n t e r p r e t this as a g o o d sign in t h e sense o f a n a d e q u a t e r e a c t i o n to t h e t r a u m a o f t h e o p e r a t i o n (Jones a n d Mayou, 1982). T h e a r t e f a c t u a l z o n e r e c o r d e d as a light b l u e a r e a in t h e L D I c a n be e i t h e r d u e to w o u n d e x u d a t i o n t h a t
304 Journal of Cranio-Maxillo-Facial Surgery
A
B
Fig. 4 - (A) On the second postoperative day a decreasing hypercirculatory zone can be seen at the recipient site of the flap. (B) On the fifth day multiple green points can be seen passing from the border to the middle of the flap.
A
B
Fig. 5 - (A) During interruption of the blood circulation on the eighth postoperative day, LDI reveals a gradient of perfusion with a maximum at the former border and a minimum close to the clamp producing an artefactual zone. (B) The controlled interruption is performed with a silicone tube.
has dried o n the skin a n d represents a barrier to laser s c a n n i n g or it is due to lack of microcirculation in this part of the flap, e.g. caused by the pressure of sutures o n the tissue. This c a n easily be differentiated by carefully cleaning the w o u n d . I n
Doppler
Figure 4A the artificial zone is p r o d u c e d by a littlesecretion a n d in Figure 6A it is p r o d u c e d by the lack of perfusion, as we c a n see in the clinical appearance. The advanta~ge of laser Doppler flowmetry in m e a s u r i n g the m i c r o c i r c u l a t i o n was tested in various
LDI of axial and random pattern flaps in the maxillo-facial area
305
A B Fig. 6 - (A) The red hypercirculatory area represents the eye (arrows) on the second day after remodelling the forehead and nose. LDI shows total flap perfusion. The light blue zone close to the eyelid (arrows) is due to a lack of microcirculation and resulted in a small area of necrosis. (B) The clinical appearance of the flap indicates a good blood supply.
animal experiments (Fischer et al., 1985; Pietilii et al., 1985; Svenson et al., 1985a). Laser Doppler ftowmetry .is an objective method giving relative values for monitoring the microcirculation of flaps (Jones et al., 1982; Heden et al., 1985; Sloan et al., 1985; Svenson et al., 1985b; Liu et al., 1986; Bruce-Chatt, 1986; Jenkins, et al., 1987; Hovius et al., 1989; Hellner and Schmelze, 1993). It is regarded as a valuable tool in the hands of the surgeon, for flap monitoring. The unidimensional Doppler has certain limitations. This system only mirrors the flow pattern in a minor volume of the flap and is not necessarily representative of the whole tissue volume. As a point-generated measurement method it cannot record the high spatial variability of skin perfusion (Shepard et al., 1987; Tenland et al., 1993). Salerud and Nilson (1986) therefore suggested early on that multifibre optic probes be used. The unidimensional laser Doppler has the problem of positioning and fixing the probe. Since a measurement is only possible while the probe is in direct contact with the wound, the results can be falsified by the probe-induced pressure, and temperature changes in the skin, although these are minor errors (Sacks et al., 1988). The mode of skin contact of the conventional flowmeter limits the application of this apparatus to fields such as the postoperative follow-up of wounds, due to the risk of wound-healing impairment caused by transmission of organisms. Laser Doppler scanning and the imaging of the microcirculation as a new monitoring system enables the surgeon to measure the microcirculation without physical contact with the wound, in an area of a
maximum of 12 cm square, so that the problems mentioned above cannot occur. It is now, for the first time, possible to display a two-dimensional image of flap perfusion. CONCLUSIONS The two-dimensional LDI system is a simple and noninvasive method for continuous measurement of the microcirculation. Because there is no contact with the wound sterility is maintained. The measuring procedure is always reproducible and the images can be stored in a personal computer for comparison with previous measurements. We see the main advantage as the possibility of obtaining a representative, real time image of flap microcirculation for comparison with the surrounding area. References Bruce-Chatt, A.J. : Free flap monitoring using a microcomputer linked to a laser Doppler flowmeter. Br. J. Plast. Surg. 39 (1986) 229-238. Fischer, J. C., P. M. Parker, W. W. Shaw: Laser Doppler flowmeter measurements of skin perfusion changes associated with arterial and venous compromise in the cutaneous island flap. Microsurgery 6 (1985) 238-243. Heden, P. G., R. Hamilton, G. Arnander, G. Jurell: Laser Doppler surveillance of circulation of free flaps and replanted digits. Microsurgery 6 (1985) 11-19. Hellner, D., R. Schmelzle: Laser Doppler monitoring of free microvascular flaps in maxillofacial surgery. J. Craniomaxillofacial Surg. 21 (1993) 25-29. Hovius, S. E. R., L. N. A. Adrichem, H. D. Van Mulder, J. C. Van der Meulen: Postoperative monitoring in microvascular
306 Journal of Cranio-Maxillo-Facial Surgery surgery, presented at the First European Congress on Hand Surgery, Taranto 1989. Jenkins, S. D., R. S. Sepka, W. J. Barwick, D. Serafin, B. Klitzman: Routine clinical use of laser Doppler flowmeter
to monitor free tissue transfer: preliminary results. J. Reconstr. Microsurg. 3 (1987) 281-283. Jones, B. M., B. J. Mayou : The laser Doppler flowmeter for microvaseular monitoring: a preliminary report. Br. J. Plast Surg. Res. 43 (1982) 147-150. Liu, A. J., C. W. Cummings, R. E. Trachy : Venous outflow obstruction in myocutaneous flaps: changes in microcirculation detected by the perfusion flowmeter and laser Doppler. Otolaryngol. Head Neck Surg. 94 (1986) 164-168. Nilson, G. E., T. Tenland, P. A. Oberg : A new instrument for continuous measurement of tissue blood flow. IEEE TransBME 27 (1980a) 1-8. Nilson, G. E., T. Tenland, P. A. Oberg : Evaluation of a laser Doppler flowmeter for measurement of tissue blood flow. TEEE Trans BME 27 (1980b) 597-604. Pietilii, J., K. V. Smitten, B. Sundell: The effect of perfusion on post operative viability in the replanted rabbit ear: measured by laser Doppler flowmetry and skin temperature. Scan& J. Plast. Reconstr. Surg. (1985) 251-254. Sacks, A. H., G. Ksander, H. O'Neill, L Perkash: Difficulties in laser Doppler measurement of skin blood flow under applied external pressure. J. Rehabil. Res. Dev. 25 (1988) 19-23. Salerud, E. G., G. E. Nilsson: Integrating probe for tissue laser Doppler flowmeters. Med. Biol. Eng. Comput 24 (1986) 415-423.
Shepard, A. P., P. A. Oberg." Laser doppler blood flowmetry.
Kluwers Academic Publ. 1990. Shepard, A. P., G. L. Riedel, J. W. Kile, D. J. Haumschild, L. C. Maxwell: Evaluation of an infrared laser Doppler flowmeter.
Am. J. Physio. 1252 (1987) 832-839. Sloan, G. M., G. H. Sasaki." Noninvasive monitoring of tissue
viability. Clin. Plast. Surg. 12 (1985) 185-195. Svenson, H., H. Pettersson, P. Svedman: Laser Doppler
flowmetry and laser photometry for monitoring free faps. Scand. J. Plast. Reconstrl Surg. 19 (1985a) 245-249. Svensson, H., P. Svedman, J. Holmberg, S. Jaeobson . Detecting arterial and venous obstruction in flaps. Ann. Plast. Surg. 14 (1985b) 20-23. Stern, M. D. : In vivo evaluation of microcircu!ation by coherent light scattering. Nature 254 (1975) 56. Tenland, T., G. Salerud, G. E. Nilson: Spatial and temporal variation in human skin blood flow. Int. J, Microcir. Clin. Exp. 2 (1993) 81-90.
Dr Dr Wolfgang Eiehhorn Mund-Kiefer-Gesichtschirurg Plastische Operationen Bahnhofstrasse 26 72336 Balingen Germany
Paper received 18 August 1993 Accepted 19 April 1994
Laser Doppler imaging of axial and random pattern flaps in the maxillo-facial area. A preliminary report Wolfgang Eichhorn 1, Thorsten Auer 2, Ernst-Dieter Voy 1, Klaus Hoffmann2
1Department Maxillofacial Surgery, (Head." Pr@ Dr Dr E.-D. Voy), EvangeIisches Krankenhaus Hattingen, Bredenscheiderstrafle 54, 45525 Hattingen. 2Dermatological Clinic, (Head: Prof. Dr P. AItmeyer), Ruhr-Universitiit Bochum, Germany
SUMMARY. Objective, non-invasive examination, techniques in addition to clinical parameters, are required to follow-up the wound healing of flaps. With the new laser Doppler Scanner (LDI DIM 1.0 Lisca Development AB, Sweden) it is possible, for the first time, to measure and image the microcirculation continuously, non-invasively and without contact with the wound, in an area of 12 cm square maximum. We performed measurements and simultaneous two-dimensional imaging of the microcirculation 24, 48, 72 h and 5 and 14 days postoperatively in 20 patients, who had had reconstruction procedures performed using random or axial pattern flaps. The perfusion diagrams were correlated to the clinical appearance. Necrotic areas, venous stasis and normal course of wound healing can be clearly visualized and differentiated from one another. The new laser Doppler imaging system seems to be an excellent aid for following up and planning of flaps in plastic and reconstructive surgery. INTRODUCTION
measuring depth of 300 to 500 micrometres we find the papillae of the dermis and the upper horizontal plexus underneath the epidermis, with a thickness of 100 micrometres. The laser beam is guided in a random pattern over a defined area with the help of a reflecting system controlled by two stepping motors. The size of the test area is defined by the distance of the scanner from the skin surface and by the variable density of the sites measured. The test distance between the scanner probe and the skin surface was 15 to 20 cm. The perfusion image recorded by the laser Doppler imaging (LDI) is made up of 4096 measurement points. The laser signal reflected from a moving red blood cell is registered by a photo detector. The intensity of the light signal is transformed into an electrical signal in volts and transmitted to a signal processor (Fig. 1). During the taking of measurements, irregularities of the skin surface being examined can lead to a change in the distance of the skin from the detector and in the detector-to-laser angle. The resulting positional signal deviation is compensated for with the aid of a correctional algorithm. Image processing occurs concomitantly with the measurements so that an evaluation can be performed immediately. Perfusion values are coded on a six colour scale from blue, meaning low flow, through green and yellow to red, indicating a high flow.
Objective and non-invasive examination techniques, in addition to clinical parameters, are required to study the course of wound healing of flaps. Laser Doppler ftowmetry constitutes a relatively new method for microcirculatory blood flow studies in human skin and in other tissues, e.g. bone, muscle (Stern, 1975; Nilsson et al., 1980; Shepard et al., 1987, 1990; Tenland et al., 1993). A two-dimensional imaging system, as it effects an entire area, has only recently become available. The aim of the following study is to evaluate the possibilities and limits of this new twodimensional imaging system. MATERIALS AND METHODS The course of wound healing was studied in 20 patients who had had reconstruction procedures performed. In 7 cases it was an axial pattern and in 13 cases a random pattern flap. The period of study was chosen to be 14 days. Their ages ranged between 16 and 88 years (mean age 59 years). For diagnosis, size and type of flap, see the Table. All measurements were performed in the dark to avoid interference by visible light, after the patient was acclimatized to this situation for half an hour, in a prone position. Measurements were performed at 24, 48, 72 h and 5 and 14 day postoperatively. The laser Doppler Perfusion Imager, PIM 1.0 (Lisca Development Link6ping Inc., Sweden), was used for laser Doppler scanning, utilizing the Doppler shift of the laser light as the information carrier. The heliumneon laser beam has a wavelength of 632.8 nm with a measuring depth of 300 to 500 micrometres. At a
RESULTS The value of the two-dimensional laser Doppler system for imaging the microcirculation of flaps is demonstrated, for example, by the following clinical case.
301
302
Journal of Cranio-Maxillo-Facial Surgery
Table - Number of patients, diagnosis, localization, type and size of flap Site
Type of flap
Nose
Axial
12 x 6
Front
Axial
12 x 8
Front
Axial
10 x 6
Front
Random
3x5
Nose
Axial
1x 4
Nose
Random
3x3
Nose
Random
2.5x3
Front
Axial
4x7
Nose
Random
5x3
Cheek Upper lid
Random Random
5x 2 3x 1
M. Bowen
Neck
Basal cell carcinoma Spinalioma Trauma Cleft lip Basal cell carcinoma Basal cell carcinoma
Nose
Random Random
3x2 4x2
Neck
Random Axial Axial Random
1x 1x 2x 2x
Cheek
Random
2x6
Random
3x2
Random
4x8
Name
Age
Diagnosis
P.C.
51
K.I.
48
U.F.
64
S.W.
88
C.B.
63
G.K.
66
P.B.
72
G.H.
56
O.P.
76
H.G. E.F.
55 45
Lentigo maligna Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma Spinalioma Basal cell carcinoma
H.B. B.W.
71 75
T.W. L.B. F.M. R.C.
68 21 16 84
G.R.
55
H.A.
52
M.B.
62
Upper lid Upper lip Upper lip
Upper lip carcinoma FibrosarNeck coma Ba~al cell
Size of flap (cm)
3 3 1 3
(Fig. 2A). Immediately after tumour resection we implanted a skin expander underneath the frontalis muscles to expand the skin of the forehead (Fig. 2B). On the first postoperative day, LDI showed a wide hypercirculatory area at the recipient site and a small hyperperfused zone on the flap edges. The small light blue zone represents an artefactual area, indicating that no laser Doppler shift of an erythrocyte could be recorded. This can be due to exudation from the wound that had dried on the skin and is a barrier to the laser light, or that there is no microcirculation in this section of the flap. We focus on the fact that the most distant point of the flap has the best perfusion (Fig. 3). On the second day we see a smaller hypercirculatory area at the recipient site. At one point there seems to be a bridging as a sign of commencing neogenesis of vessels. On the fifth day the hyperaemic Zone at the recipient site is again smaller and we detect multiple green points located from the border to the middle of the flap as a sign of perfusion changing from the axial artery to nutrition from the margins (Fig. 4). We encouraged the neogenesis of vessels by controlled interruptions of blood circulation. LDI during interruption reveals that the furthest point to be perfused is now close to the eyelid. We see a gradient of perfusion with a maximum at the former border and a minimum close to the clamp, which produces an artefactual zone due to pressure (Fig. 5). On the twelfth day we cut the frontal flap and remodel the forehead and nose. The hyperaemic area in the right upper corner on the LDI corresponds to the left eye. We can see a small artificial zone at the lower eyelid. The flap is perfused in toto. The LDI and the clinical appearance are in accordance (Fig. 6).
CASE REPORT Tlais 63-year-old woman suffered from a lentigo maligna of the nose, nasolabial fold and lower eyelid
He-Ne Laser
Scanner.Head: -Mirror-System .Step-Motors -Preamplifier
~ Photodetector
1
Processor A-D-Board
[ Plotter .,~J
t[ Data.Analysis]
Fig. 1 - Diagram of the laser Doppler scanner for laser Doppler imaging.
LDI of axial and random pattern flaps in the maxillo-facial area
A
303
B
Fig. 2 - (A) This 63-year-old woman suffered from a lentigo maligna of the nose, nasolabial fold and lower eyelid. (B) The frontal flap is partly elevated with the skin expander lying underneath the frontalis muscles.
A
B
Fig. 3 (A) On the first postoperative day a light blue elliptic zone in the right lower corner representing the nostril can be observed. The dark blue area is the surface of the wound. A wide hypercirculatory red area can be seen on the flaps edge and at the recipient site. (B) The frontal flap is raised and transposed into the nasal defect.
DISCUSSION P o s t o p e r a t i v e l y , w e o b s e r v e d a h y p e r a e m i c z o n e at t h e r e c i p i e n t site a n d a s m a l l e r h y p e r c i r c u l a t o r y a r e a o n t h e flap e d g e s t h a t is r e g r e s s i n g o v e r a t w o w e e k
p e r i o d . W e i n t e r p r e t this as a g o o d sign in t h e sense o f a n a d e q u a t e r e a c t i o n to t h e t r a u m a o f t h e o p e r a t i o n (Jones a n d Mayou, 1982). T h e a r t e f a c t u a l z o n e r e c o r d e d as a light b l u e a r e a in t h e L D I c a n be e i t h e r d u e to w o u n d e x u d a t i o n t h a t
304 Journal of Cranio-Maxillo-Facial Surgery
A
B
Fig. 4 - (A) On the second postoperative day a decreasing hypercirculatory zone can be seen at the recipient site of the flap. (B) On the fifth day multiple green points can be seen passing from the border to the middle of the flap.
A
B
Fig. 5 - (A) During interruption of the blood circulation on the eighth postoperative day, LDI reveals a gradient of perfusion with a maximum at the former border and a minimum close to the clamp producing an artefactual zone. (B) The controlled interruption is performed with a silicone tube.
has dried o n the skin a n d represents a barrier to laser s c a n n i n g or it is due to lack of microcirculation in this part of the flap, e.g. caused by the pressure of sutures o n the tissue. This c a n easily be differentiated by carefully cleaning the w o u n d . I n
Doppler
Figure 4A the artificial zone is p r o d u c e d by a littlesecretion a n d in Figure 6A it is p r o d u c e d by the lack of perfusion, as we c a n see in the clinical appearance. The advanta~ge of laser Doppler flowmetry in m e a s u r i n g the m i c r o c i r c u l a t i o n was tested in various
LDI of axial and random pattern flaps in the maxillo-facial area
305
A B Fig. 6 - (A) The red hypercirculatory area represents the eye (arrows) on the second day after remodelling the forehead and nose. LDI shows total flap perfusion. The light blue zone close to the eyelid (arrows) is due to a lack of microcirculation and resulted in a small area of necrosis. (B) The clinical appearance of the flap indicates a good blood supply.
animal experiments (Fischer et al., 1985; Pietilii et al., 1985; Svenson et al., 1985a). Laser Doppler ftowmetry .is an objective method giving relative values for monitoring the microcirculation of flaps (Jones et al., 1982; Heden et al., 1985; Sloan et al., 1985; Svenson et al., 1985b; Liu et al., 1986; Bruce-Chatt, 1986; Jenkins, et al., 1987; Hovius et al., 1989; Hellner and Schmelze, 1993). It is regarded as a valuable tool in the hands of the surgeon, for flap monitoring. The unidimensional Doppler has certain limitations. This system only mirrors the flow pattern in a minor volume of the flap and is not necessarily representative of the whole tissue volume. As a point-generated measurement method it cannot record the high spatial variability of skin perfusion (Shepard et al., 1987; Tenland et al., 1993). Salerud and Nilson (1986) therefore suggested early on that multifibre optic probes be used. The unidimensional laser Doppler has the problem of positioning and fixing the probe. Since a measurement is only possible while the probe is in direct contact with the wound, the results can be falsified by the probe-induced pressure, and temperature changes in the skin, although these are minor errors (Sacks et al., 1988). The mode of skin contact of the conventional flowmeter limits the application of this apparatus to fields such as the postoperative follow-up of wounds, due to the risk of wound-healing impairment caused by transmission of organisms. Laser Doppler scanning and the imaging of the microcirculation as a new monitoring system enables the surgeon to measure the microcirculation without physical contact with the wound, in an area of a
maximum of 12 cm square, so that the problems mentioned above cannot occur. It is now, for the first time, possible to display a two-dimensional image of flap perfusion. CONCLUSIONS The two-dimensional LDI system is a simple and noninvasive method for continuous measurement of the microcirculation. Because there is no contact with the wound sterility is maintained. The measuring procedure is always reproducible and the images can be stored in a personal computer for comparison with previous measurements. We see the main advantage as the possibility of obtaining a representative, real time image of flap microcirculation for comparison with the surrounding area. References Bruce-Chatt, A.J. : Free flap monitoring using a microcomputer linked to a laser Doppler flowmeter. Br. J. Plast. Surg. 39 (1986) 229-238. Fischer, J. C., P. M. Parker, W. W. Shaw: Laser Doppler flowmeter measurements of skin perfusion changes associated with arterial and venous compromise in the cutaneous island flap. Microsurgery 6 (1985) 238-243. Heden, P. G., R. Hamilton, G. Arnander, G. Jurell: Laser Doppler surveillance of circulation of free flaps and replanted digits. Microsurgery 6 (1985) 11-19. Hellner, D., R. Schmelzle: Laser Doppler monitoring of free microvascular flaps in maxillofacial surgery. J. Craniomaxillofacial Surg. 21 (1993) 25-29. Hovius, S. E. R., L. N. A. Adrichem, H. D. Van Mulder, J. C. Van der Meulen: Postoperative monitoring in microvascular
306 Journal of Cranio-Maxillo-Facial Surgery surgery, presented at the First European Congress on Hand Surgery, Taranto 1989. Jenkins, S. D., R. S. Sepka, W. J. Barwick, D. Serafin, B. Klitzman: Routine clinical use of laser Doppler flowmeter
to monitor free tissue transfer: preliminary results. J. Reconstr. Microsurg. 3 (1987) 281-283. Jones, B. M., B. J. Mayou : The laser Doppler flowmeter for microvaseular monitoring: a preliminary report. Br. J. Plast Surg. Res. 43 (1982) 147-150. Liu, A. J., C. W. Cummings, R. E. Trachy : Venous outflow obstruction in myocutaneous flaps: changes in microcirculation detected by the perfusion flowmeter and laser Doppler. Otolaryngol. Head Neck Surg. 94 (1986) 164-168. Nilson, G. E., T. Tenland, P. A. Oberg : A new instrument for continuous measurement of tissue blood flow. IEEE TransBME 27 (1980a) 1-8. Nilson, G. E., T. Tenland, P. A. Oberg : Evaluation of a laser Doppler flowmeter for measurement of tissue blood flow. TEEE Trans BME 27 (1980b) 597-604. Pietilii, J., K. V. Smitten, B. Sundell: The effect of perfusion on post operative viability in the replanted rabbit ear: measured by laser Doppler flowmetry and skin temperature. Scan& J. Plast. Reconstr. Surg. (1985) 251-254. Sacks, A. H., G. Ksander, H. O'Neill, L Perkash: Difficulties in laser Doppler measurement of skin blood flow under applied external pressure. J. Rehabil. Res. Dev. 25 (1988) 19-23. Salerud, E. G., G. E. Nilsson: Integrating probe for tissue laser Doppler flowmeters. Med. Biol. Eng. Comput 24 (1986) 415-423.
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Kluwers Academic Publ. 1990. Shepard, A. P., G. L. Riedel, J. W. Kile, D. J. Haumschild, L. C. Maxwell: Evaluation of an infrared laser Doppler flowmeter.
Am. J. Physio. 1252 (1987) 832-839. Sloan, G. M., G. H. Sasaki." Noninvasive monitoring of tissue
viability. Clin. Plast. Surg. 12 (1985) 185-195. Svenson, H., H. Pettersson, P. Svedman: Laser Doppler
flowmetry and laser photometry for monitoring free faps. Scand. J. Plast. Reconstrl Surg. 19 (1985a) 245-249. Svensson, H., P. Svedman, J. Holmberg, S. Jaeobson . Detecting arterial and venous obstruction in flaps. Ann. Plast. Surg. 14 (1985b) 20-23. Stern, M. D. : In vivo evaluation of microcircu!ation by coherent light scattering. Nature 254 (1975) 56. Tenland, T., G. Salerud, G. E. Nilson: Spatial and temporal variation in human skin blood flow. Int. J, Microcir. Clin. Exp. 2 (1993) 81-90.
Dr Dr Wolfgang Eiehhorn Mund-Kiefer-Gesichtschirurg Plastische Operationen Bahnhofstrasse 26 72336 Balingen Germany
Paper received 18 August 1993 Accepted 19 April 1994