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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_557_Библиотеки_им_академика_М_И_Перельмана
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Chapter 13 Rejuvenation of the aging face and skeleton with implants
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dystrophy. Cleft Palate Craniofac J 1992;29(5):456–62.
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aging. Plast Reconstr Surg 1998;102(1):205–12.
17. Pessa JE, Desvigne LD, Lambros VS, et al. Changes in ocular globe-to-orbital rim position
with age: implications for aesthetic blepharoplasty of the lower eyelids. Aesthetic Plast Surg
1999;23(5):337–42.
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Chapter 14
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Designer faces: CAD/CAM facial
implants
INDICATIONS FOR AND ADVANTAGES OF CAD/CAM
Computer-aided design and manufacturing (CAD/CAM) provides added
sophistication to facial implant surgery. It provides three-dimensional millimeter accuracy in implant design and manufacturing specific to the facial
skeleton being addressed. This precision potentially minimizes or eliminates
limitations intrinsic to the use of “off-the-shelf” implants and asymmetry of
the facial skeleton. CAD/CAM implants are custom made for the individual
patient.
CAD/CAM implants are ideal for patients with significant facial asymmetry.
Asymmetries are three-dimensional. They can be thought of as twists of the
skeleton. As demonstrated in Fig. 14.1, asymmetry in the mandible is more than
an asymmetry in lower facial width. Note the difference in ramus height and
border inclination.
CAD/CAM implants are also useful to correct skeletal contour irregularities
that result after orthognathic surgery. Chapter 15 describes this application in
detail.
Fig. 14.1 Three-dimensional CT scan of the facial skeleton showing
complex mandible asymmetry.
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Chapter 14 Designer faces: CAD/CAM facial implants
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Nuanced design not possible with off-the-shelf implants is possible with
CAD/CAM implants. Note the three-dimensional change in the chin as well as
correction of asymmetry in mandible body shown in Fig. 14.2.
The precise fit of the CAD/CAM implant to the underlying skeletal contour makes for a more predictable result. There is a fundamental technical problem to placing off-the-shelf bilateral implants in similar positions on
opposite sides of the face (Fig. 14.3). Remote incisions routinely provide limi ted
access and therefore limited exposure of the areas to be augmented. Furthermore,
the surgeon never has the ability to see the position of both implants in a single
view. CAD/CAM implants are made to augment precisely defined areas of the
facial skeleton, making implant positioning less problematic. These implants can
also be designed with registration features, for example, a flange on a malar implant
that rests on the infraorbital rim or on the superior edge of the zygomatic arch. Custom implants are designed to avoid any gaps between the posterior surface of the
implant and the anterior surface of the skeleton (Fig. 14.4). Gaps are unavoidable
when using off-the-shelf implants. These gaps add to the effective projection of the
implant. A 2-mm gap beneath a 3-mm implant will result in an unanticipated 5-mm
projection. An implant designed and manufactured to have its posterior surface
mirror that of the underlying skeleton will avoid that unanticipated contour result.
A B
Fig. 14.2 CAD/CAM implant allows desired width, vertical elongation, and sagittal projection of the chin as well as correcting body
asymmetry. (A) Frontal view. (B) Lateral view.
A B C
Fig. 14.3 CT scan examples of o-the-shelf and CAD/CAM implants. (A) Frontal view of a three-dimensional CT scan revealing asymmetric
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position of malar implants. (B) Frontal view of CAD/CAM malar implants. Note symmetric placement. (C) Worm’s eye view of CAD/CAM
implants that allow symmetry of implant position, as well as symmetry of combined implant plus underlying skeleton projection.
Fig. 14.4 Sagittal section of posterior mandible with
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o-the-shelf implant placed to augment its contour.
The posterior surface of the implant does not mimic
the contour of the underlying skeleton resulting
in gaps between the two surfaces. Gaps result in
unanticipated increase in contour.
Implant development
A
Fig. 14.5 Implant design using model format. (A) Model obtained from CT DICOM data. (B) Model with implant prototypes fashioned by the
treating surgeon.
IMPLANT DEVELOPMENT
Computed tomography (CT) scans are obtained to provide digital imaging and
communication in medicine (DICOM) data. DICOM is a standard for handling,
storing, printing, and transmitting information in medical imaging. This data
is used to create a three-dimensional model of the facial skeleton or a threedimensional image. The three-dimensional model allows the surgeon to craft
with clay the desired implant configuration. The clay is then used as a prototype for the implant design (Fig. 14.5). DICOM data can also be used to create
a three-dimensional image for use in virtual design sessions between surgeon
and software engineer to create an implant (Fig. 14. 6). This technique is preferred by the authors because it allows millimeter precision of design. The computerized design is then used to computer manufacture an implant.
B
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Chapter 14 Designer faces: CAD/CAM facial implants
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A
Fig. 14.6 Image created using DICOM data to design an implant. (A) Image of facial skeleton. (B) Virtually designed implant.
B
PERSONAL DESIGN TECHNIQUE
Critical to the design process is to recognize the patient’s goals. The patient
may desire to create angularity, provide symmetry, improve facial balance,
or correct irregularities. It is useful for the patient to provide photographs
of people who have the desired look. Digital manipulation of patient images
can be helpful. The patient should understand that these images are used
as guides in the design process and not predictions of the surgical outcome.
There is no algorithm that can translate a digitally created change in soft tissue to an implant design that will result in the outer contour change. Effective communication between surgeon and patient is invaluable to the design
process.
Because the native facial skeleton is not symmetric, implant augmentation will provide a “relative symmetry.” Chin implants should create
symmetry relative to the midline structures – nasal radix, nasal septum,
central incisors, and central lip elements. This symmetry should extend
from mental foramen to mental foramen. Lateral to the mental foramen,
mandible implants should relate to the width of the upper face. For example, the extent of lateral augmentation of the mandible angles should
relate to the lateral orbital rims in the same way (Fig. 14.7). Designing
an implant for one side of the face and mirroring it to create an implant
for the opposite side will create mandible symmetry only if the mandible
and midface are symmetric prior to augmentation. When augmenting the
midface, the goal is to achieve similar implant-plus-skeleton projection
(Fig. 14.8). Because the contours of the midface will vary from one side
to the other, mirroring one side to the other is unlikely to result in similar
contours.
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Personal design technique
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Fig. 14. 7 Design of chin/mandible implant demonstrating “relative
symmetry.” Note that the chin component is symmetric to the
midline from mental foramen to mental foramen. The mandible
angles are augmented in width relative to landmarks of the upper
face (lateral orbital rim, in this case).
Fig. 14.8 CAD of implants allows projection
of implant plus underlying skeleton to be
symmetric, as demonstrated in colorized
projection map on implant surface.
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Chapter 14 Designer faces: CAD/CAM facial implants
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Clinical experience has taught the senior author to control the design process.
After voicing their goals and preferences, patient participation in the step-bystep design process has proved unrewarding. The design process is inevitably
protracted and therefore more expensive when the patient is involved. More
importantly, heavily patient-influenced designs have been almost routinely
disappointing to the patient.
Clinical examples are presented in Figs. 14.9–14.12.
PEARL
Limit patient involvement in the
ongoing design process. It is often
unrewarding for both patient and
surgeon.
A B
C
Fig. 14.9 Preoperative and postoperative clinical appearance and three-dimensional CT images of a patient who underwent CAD/CAM
implant midface and mandible augmentation. (A) Preoperative appearance. (B) Postoperative appearance. (C) Image of native skeleton. (D)
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Image of designed implants.
D
Personal design technique
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Fig. 14.10 A 28-year-old man who underwent CAD/CAM implant augmentation of
midface and lower jaw as well as rhinoplasty.
(A) Preoperative frontal appearance. (B)
Postoperative frontal appearance. (C) Preoperative lateral appearance. (D) Postoperative lateral appearance. (E) Frontal view of
preoperative skeletal appearance. (F) Frontal
view of design of CAD/CAM implants. (G)
Lateral view of preoperative skeletal appearance. (H) Lateral view of design of CAD/CAM
A
B
implants.
C
E
D
F
G H
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Chapter 14 Designer faces: CAD/CAM facial implants
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Fig. 14.11 A 24-year-old woman underwent
CAD/CAM implant augmentation of her
midface and mandible. (A) Preoperative
frontal appearance. (B) Postoperative frontal
appearance. (C) Preoperative oblique
appearance. (D) Postoperative oblique
appearance. (E) Frontal view of preoperative
skeletal appearance. (F) Frontal view of
design of CAD/CAM implants. (G) Lateral
view of preoperative skeletal appearance.
(H) Lateral view of design of CAD/CAM
implants.
A
B
C
E F
D
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G
H
Personal design technique
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Fig. 14.12 A 26-year-old man underwent
CAD/CAM implant augmentation of his
midface and mandible. (A) Preoperative
frontal appearance. (B) Postoperative frontal
appearance. (C) Preoperative oblique
appearance. (D) Postoperative oblique
appearance. (E) Frontal view of preoperative
skeletal appearance. (F) Frontal view of
design of CAD/CAM implants. (G) Lateral
view of preoperative skeletal appearance.
(H) Lateral view of design of CAD/CAM
implants.
A
C
B
D
E F
G H
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