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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_660_Библиотеки_им_академика_М_И_Перельмана
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Facial measurements
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25.0%
25.0%
25.0%
25.0%
A
21.1%
24.3%
26.5%
26.9%
B
Fig. 2.6 A comparison of young male adult faces constructed from neoclassical canons and from anthropometric measurements. (A) Frontal
and lateral views of the young male adult face constructed with the help of the neoclassical canons. The head and face have ve equal
vertical sections and four equal horizontal sections. The nose width equals the eye ssure width and the interocular distance. (B) Frontal
and lateral views of the average young male white North American head and face constructed with mean measurements of both sexes. In
general, these measurements are dierent than the idealized ones shown in (A). From Farkas etal. 1985,2 with permission.
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Chapter 2 Evaluation and planning for facial implant surgery
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planning implant and other craniofacial surgery. Table 2.1 lists anthropometric
landmarks (landmarks used in craniofacial anthropometry and radiographic
cephalometry may have the same name but not the same anatomic location),
while Table 2.2 lists measurements and inclinations.
These landmarks and measurements are diagrammed in Figs. 2.7–2.10.
Denitions of frontal and lateral anthropometric landmarks useful for evaluating the face
Landmark (abbreviationa) Notes
Craniofacial complex
Vertex (v) The highest point of the head when the head is oriented in the Frankfort horizontal (FH)
Glabella (g) The most prominent midline point between the eyebrows; it is identical to the bony glabella on the
frontal bone
Frontotemporale (ft) The point on each side of the forehead, laterally from the elevation of the linea temporalis; it approximately
corresponds with the tail of the eyebrow
Zygion (zy) The most lateral point of each zygomatic arch
Gonion (go) The most lateral point on the mandibular angle close to the bony gonion
Pogonion (pg) The most anterior midpoint of the chin; it is located on the skin surface in front of the identical bony
landmark of the mandible
Menton (or gnathion) (gn) The lowest median landmark on the lower border of the mandible; it is the lowest point on the face
used in measuring facial height. It is identical to the bony gnathion
Condylion laterale (cdl) The most lateral point on the surface of the condyle of the mandible
Trichion (tr) The point on the hairline in the midline of the forehead
Orbits
Endocanthion (en) The point on the inner commissure of the eye ssure
Exocanthion (ex) The point at the outer commissure of the eye ssure
Center point of the pupil (p) Determined with the head in the rest position and the patient looking straight ahead
Orbitale (or) The lowest point on the lower margin of each orbit; it is identical to the bony orbitale
Palpebral superius (ps) The highest point in the midportion of the margin of each upper lid
Palpebral inferius (pi) The lowest point in the midportion of the margin of each lower lid
Orbitale superius (os) In young adults this is the highest point on the lower border of the eyebrow; it is close to the highest
bony point of the upper margin of the bony orbit
Superciliare (sci) The highest point on the upper border in the midportion of each eyebrow
Nose
Nasion (n) The point in the midline of both the nasal root and the nasal suture; it is identical to the bony nasion
Subnasale (sn) The midpoint of the angle at the columella base where the lower border of the nasal septum and the
surface of the upper lip meet; it is not identical to the bony subnasion
Lips and mouth
Labiale superius (ls) The midpoint of the vermilion of the upper lip
Labiale inferius (li) The midpoint of the vermilion of the lower lip
Stomion (sto) The imaginary point at the intersection of the vertical facial midline and the horizontal labial ssure
a
Abbreviations used in Figs. 2.7–2.10 and Table 2.2.
Data from Farkas etal. 1994,6 with permission.
Table 2.1 Denitions of frontal and lateral anthropometric landmarks useful for evaluating the face
See frontal view (Fig. 2.7A); lateral view (Fig. 2.7B).
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Facial measurements
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Craniofacial complex measurements useful for evaluating the face
Measurement Facial area Male Female
Single linear frontal Height (mm)
v–gn Upper, middle, and lower face 229 ± 7 215 ± 8
v–n Upper face 111 ± 7 109 ± 6
v–tr Hair-bearing scalp 46 ± 9 47 ± 8
tr–n Forehead 67 ± 8 63 ± 6
n–gn Middle and lower face 125 ± 6 111 ± 5
n–sto Middle face 76 ± 4 70 ± 3
sn–gn Lower face 73 ± 5 64 ± 4
sto–gn Mandible 51 ± 4 43 ± 3
Single paired frontal Height (mm)
go–cdl Mandibular ramus 68 ± 5 62 ± 5
go–gn Mandibular body 86 ± 5 81 ± 4
Single linear frontal Width (mm)
ft–ft Forehead 116 ± 5 111 ± 4
zy–zy Midface 139 ± 5 130 ± 5
go–go Lower face 106 ± 7 95 ± 5
Single angular lateral (measured from the vertical) Prole (degrees)
tr–g Forehead −10 ± 4 −6 ± 5
g–sn Middle face 2 ± 3 2 ± 3
g–ls Middle face (Leiber line) 1 ± 4 2 ± 3
sn–pg Lower face −11 ± 5 −13 ± 5
li–pg Mandible −15 ± 7 −19 ± 7
g–pg General −3 ± 3 −4 ± 3
Data from Farkas etal. 1994,6 with permission.
Table 2.2 Craniofacial complex measurements useful for evaluating the face
See frontal female (Fig. 2.8A), frontal male (Fig. 2.8B); lateral female (Fig. 2.9A), lateral male (Fig. 2.9B).
Sexual dimorphism
These objective data identify the sexual dimorphism in human faces. On the
average, all facial measurements are greater in men than in women. In addition, the relationship between measurements differs in men and women. These
differences are pronounced in the lower third of the face. The bigonial distance (go–go) is the transverse facial dimension that has the greatest difference
between the sexes. In other words, the lower one-third of women’s faces tends
to be absolutely and relatively narrower than that of men. Gender-related differences have implications for surgical planning. For example, if a normaldimensioned male mandible is augmented in the transverse dimension, it may
be perceived as stronger. However, if a normal-dimensioned female mandible
is augmented, it may be perceived as masculine. Fig. 2.11 shows typical male
and female skulls.
Anthropometric data aids facial evaluation and surgical planning by
describing normal facial measurements and relations. With this framework,
the status of the patient is more easily understood and the goals of surgery
defined.
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v
v
tr
ft
g
ft
tr
ft
g
n
zy zy
or
n
or
zy
cdl
sn
sn
ls
go
sto
go
li
pg
A
gn
ls
sto
li
go
pg
gn
B
Fig. 2.7 Anthropometric landmarks relevant to implant surgery; see Table 2.1 for denitions. The schematic drawings show the surface
landmarks in relation to the underlying facial skeleton: (A) frontal and (B) lateral view.
op
v
46
tr
109
63
n
70
111
sto
43
gn
ft-ft
111
zy-zy
130
go-go
95
215
sn
64
A
v
46
tr
111
67
n
76
125
sto
51
gn
ft-ft
116
zy-zy
139
go-go
106
B
Fig. 2.8 Frontal view of female and male faces drawn from average anthropometric measurements for 21-year-old white North
Americans: (A) female and (B) male. See Table 2.1 for denitions.
20
229
sn
73
Facial measurements
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sn
sto
gn
v
46
tr
67
n
76
51
73
86
cdl
68
go
B
sto
v
47
tr
63
n
70
sn
43
64
gn
81
cdl
62
go
A
Fig. 2.9 Lateral view of female and male faces drawn from average anthropometric measurements for 21-year-old white North Americans:
(A) female and (B) male. See Table 2.1 for denitions.
tr
6°
n
2°
-4°
2°
sn
ls
-13°
li
pg
-19°
A
tr
10°
n
1°
-3°
2°
sn
ls
-11
li
pg
-15°
B
Fig. 2.10 Lateral view of female and male faces drawn from average anthropometric
measurements for 21-year-old white North Americans showing prole inclinations: (A)
female and (B) male. See Table 2.1 for denitions.
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Chapter 2 Evaluation and planning for facial implant surgery
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A
B
Fig. 2.11 (A) Female and (B) male skull images. From the Atkinson Skull Collection, University of the Pacic, Dugoni School of Dentistry, 155
Fifth Street, San Francisco, CA.
The small dimensions and complex configuration of the face make millimeter differences and changes noticeable and significant. For these reasons, it is
important to know the average or “normal” dimensions of the face and its component features. Implants that are too large create unnatural contours that relate
poorly to other areas of the face. Inappropriate implants may therefore upset
the “balance” of the face. Facial implants must be appropriately sized, shaped,
and positioned to be effective.
REFERENCES
1. Clayton M. Leonardo Da Vinci – The divine and the grotesque. 1st ed. London: Royal
Collection Enterprises; 2002.
2. Farkas L, Hreczko TA, Kolar JC, Munro IR. Vertical and horizontal proportions of the face in
young adult North American Caucasians: revision of neoclassical canons. Plast Reconstr Surg
1985;75(3):328–38.
3. Farkas LG, Kolar JC. Anthropometrics and art in the aesthetics of women’s faces. Clin Plast
Surg 1987;14(4):599–616.
4. Ricketts RM. Divine proportions in facial esthetics. Clin Plast Surg 1982;9(4):401–22.
5. Etcoff N. Survival of the prettiest. 1st ed. New York: Anchor Books; 2000.
6. Farkas LG, Hreczko TA, Katic MJ. Appendix A: Craniofacial norms in North American
Caucasians from birth (one year) to young adulthood. In: Farkas LG, editor. Anthropometry of
the head and face. 2nd ed. New York: Raven Press; 1994.
7. Farkas LG, Ngim RCK, Lee ST. Appendix B: Craniofacial norms in 6-, 12-, and 18-year-old
Chinese subjects. In: Farkas LG, editor. Anthropometry of the head and face. 2nd ed. New York:
Raven Press; 1994.
8. Farkas LG, Venkatadri G, Gubbi AV. Appendix B: Craniofacial norms in young adult African-
Americans. In: Farkas LG, editor. Anthropometry of the head and face. 2nd ed. New York:
Raven Press; 1994.
9. Farkas LG, Katic MJ, Forrest CR. International anthropometric study of facial morphology in
various ethnic groups/races. J Craniofac Surg 2005;16:615–46.
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Chapter 3
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Implant materials
The craniofacial skeleton can be reconstructed with both autogenous bone and
alloplastic implants. Alloplastic implants are used only as onlay grafts to the
native skeleton to improve facial contour and to replace missing portions of
the non-load-bearing cranial vault and internal orbit. Autogenous bone may be
used for these purposes, but is more suited to replace segmental, load-bearing
defects of the facial skeleton. Virtually all aesthetic facial skeletal augmentation, as well as cranial vault replacement, is done with alloplastic materials.
Three basic categories of alloplastic materials are used in facial reconstruction.
Polymers and ceramics are used to replace or augment bone. Metals are used as
fixation or support devices.
AUTOGENOUS MATERIALS
Bone
Autogenous bone has long been considered the standard material to restore or
improve the craniofacial skeleton because it has the potential to become revascularized and then assimilated into the facial skeleton. In time, it could be biologically indistinguishable from the adjacent native skeleton. These attributes make
it ideal and the only material available to reliably reconstruct segmental loadbearing defects of the facial skeleton. When used as an onlay graft, these attributes lead to graft resorption and unreliable augmentation of the facial skeleton.
Factors that impact result
Clinical experience and laboratory investigation have revealed that the fate of
non-vascularized onlay bone grafts placed in the craniofacial skeleton depends
on three interrelated factors: the architecture of the graft, its revascularization,
and the recipient site.
Graft architecture and revascularization
Onlay grafts harvested from the calvarium are superior to grafts harvested from
the iliac crest in volume maintenance. This difference was initially attributed
to the embryonic origin of the graft, prompting use of the terms membranous
and endochondral grafts as opposed to the anatomic terms calvarial and iliac crest
grafts. Kusiak et al. reported that calvarial bone grafts become revascularized
earlier than iliac grafts, and attributed this volume maintenance to their early
revascularization.1 However, this explanation was questioned when Lin et al.2
and Sullivan et al.3 reported more extensive revascularization in iliac crest grafts.
Lin evaluated the volume persistence of calvarial and iliac crest grafts fixed
to the rabbit snout with lag screws (Fig. 3.1).2 Early revascularization of the
grafts occurred only in the cancellous portion of both grafts suggesting that the
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Iliac crest Calvarial graft
Cortical bone
Cancellous bone
Fig. 3.1 Schematic drawing of the placement of iliac crest (left) and calvarial (right) onlay
bone grafts on the snout of the rabbit.
Fig. 3.2 Latex vascular cast injection of 6-week onlay bone graft harvested from the
calvarium and xed to the snout of its rabbit host with a lag screw (×5). Arrow points to lag
screw. Broken line separates cortical layer (above) from cancellous layer (below). Note that
the vessels (yellow dye) penetrate only the cancellous portions of the graft.
cortical portion of the grafts acted as a mechanical barrier to ingrowing blood
vessels (Fig. 3.2). This observation prompted Chen’s study.
4
Using a model similar to Lin’s, Chen et al. also evaluated the volume persistence of calvarial and iliac crest grafts fixed to the rabbit snout with lag screws.4
In addition, Chen correlated graft revascularization and graft resorption with
graft architecture in the cortical and cancellous regions of both calvarial and
iliac grafts. Revascularization was evaluated using latex vascular cast injection, while osteoclastic activity was evaluated using a tartrate-resistant acid
phosphatase stain. As expected, he found that at 70 days the calvarial grafts
demonstrated greater volume maintenance than the iliac bone (72% vs. 32%,
P < .025). He found significantly greater revascularization and osteoclastic activity in the cancellous portion of both the calvarial and iliac crest bone grafts by
the 10th day after onlay grafting. Minimal activities were present in the cortical
bone (Figs. 3.3 and 3.4). Because calvarial grafts contain more cortical bone, the
superior volume maintenance can be understood by the influence of bone architecture on revascularization and resorption. Cortical bone is more slowly revas-
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cularized, and therefore less available to osteoclastic activity. The amount of
Autogenous materials
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A
Fig. 3.3 Latex vascular cast injection of (A) 10-day calvarial graft and (B) 10-day iliac crest
graft (×10). The orientation is similar to that shown in Fig. 3.1. Arrows point to lag screws.
Note that the blood vessels (red dye) penetrate only the cancellous portions of the graft.
A
Fig. 3.4 Tartrate-resistant acid phosphatase (TRAP) histochemical stain of the osteoclastic
activity of (A) 10-day calvarial and (B) 10-day iliac crest grafts (both ×50). There was
signicant osteoclastic activity (red dye) in the cancellous areas of the grafts but minimal
activity in the cortex. Solid line separates onlay graft from snout. TRAP stain penetration
mimics that of vascular penetration shown in Fig. 3.3.
B
B
cortical bone in an onlay graft determines its volume maintenance. The importance of graft architecture, as opposed to its embryologic origin, to the volume
persistence of onlay bone grafts has been supported in later studies by Gosain.5
Rigid fixation
Chen’s study also explained the observation of others that rigid fixation
improves graft volume maintenance.4 Lag screw fixation obliterates the gap
between the graft and the recipient bed and therefore may reduce neovascularization of the graft at this interface. Rigid fixation may therefore improve the
volume maintenance of onlay bone grafts by limiting, rather than facilitating,
revascularization of the graft.
Recipient site
The volume maintenance of a bone graft depends on where it is placed. Zins
et al. originally proposed that bone grafts placed in depository fields on the
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Chapter 3 Implant materials
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growing facial skeleton would have improved volume maintenance.6 Gosain
et al., using an adult animal model, found complete or near-complete resorption
of onlay bone grafts over 1 year (despite the use of rigid fixation and irrespective of their depository or resorptive recipient beds).7 Rather than its embryologic role in facial growth, the recipient site impacts the fate of a bone graft by
the functional stresses it places on the graft. These stresses are determined by
regional musculoskeletal forces and by deforming forces of the overlying soft
tissue envelope.
The description of this phenomenon is attributed to the German anatomist
Julius Wolff, and has long been referred to as Wolff’s Law. It was described for
the axial skeleton but is equally applicable to the craniofacial skeleton. When
used as an interposition or inlay graft to fill a defect in a location with significant musculoskeletal forces acting on it, for example the mandible, functional
stresses will result in the graft’s eventual remodeling into a size and shape similar to the segment it is replacing. When the bone replaced provides a more
protective function with little stress on it, for example the cranial vault, the
graft loses volume due to osteolysis, as well as revascularization and osteoclastic resorption. Similarly, the volume persistence of an onlay bone graft will be
determined by the musculoskeletal forces working on them and the deforming forces of the overlying soft tissue envelope. This translation of mechanical
forces into chemical or electrical signals to elicit cell activity is termed “mechanotransduction,” where osteocytes are believed to be the primary mediators.
When stressed, osteocytes convert the mechanical forces into molecular signals,
which result in bone remodeling.
In summary, the fate of an onlay bone graft is unpredictable but depends
on its revascularization and factors that impact its subsequent remodeling. If
a bone graft does not become revascularized, it acts like a sequestrum, which
remains inert and can maintain its volume indefinitely.9 This realization
prompted the senior author’s use of certain alloplastic materials to replace or
augment the facial skeleton. The use of alloplastic materials also has the advantage of avoiding the morbidity, time, and cost associated with autogenous graft
harvest.
Autogenous bone graft has long been considered the gold standard material
for facial skeleton reconstruction.10 The term “gold standard” is derived from
economics, where the standard economic unit of account is based on a fixed
quantity of gold. Gold was chosen because, of all major metals, it is the most
resistant to corrosion, and therefore maintains its volume and value over time.
Ironically, as noted above, volume retention is not an attribute of autogenous
bone when used as an onlay graft.
PEARL
After a bone graft is revascularized,
its volume will be determined by
functional stresses.
Cartilage
In the realm of facial skeletal augmentation, cartilage has a limited role except
for nasal onlay grafts. Advantages for using cartilage include lowest rate of
resorption (since it is not vascularized) and extrusion. Potential donor sites
include auricular, nasal septal, and costal grafts. Costal cartilage grafts provide
an ample source of cartilage for nasal dorsal augmentation. However, cartilage
grafts have a tendency to warp and their donor site is not free of morbidity.11
Cadaveric cartilage presents an alternative source of cartilage, free of donor site
morbidity, with reports of good tissue compatibility and low rate of infection.
However, the problem of warping remains, regardless of whether the cartilage
26
was irradiated or not. Graft resorption has been reported as well.12
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