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M. J. Recker et al.
Computer-Aided Surgery
Computer-aided surgery can be divided into ve phases (Table1.1): (1) the data
acquisition phase, in which all imaging, laser surface scans, clinical information,
anthropometric measurements, implant STereoLithography (STL) and measurements are obtained; (2) the planning phase, in which computed tomography (CT)
data is imported into a proprietary software program for the purposes of virtually
planning the surgery; (3) manufacturing phase in which guides, stents, and patientspecic implants are fabricated using 3D printers; (4) surgical phase, which is performed utilizing computer-aided design and computer-aided manufacturing (CAD/
CAM) derived stereolithographic models, guide-stents, splints, patient-specic
implants, and/or intraoperative navigation; and (5) assessment phase, in which the
accuracy of the treatment plan transfer is evaluated using intraoperative (or postoperative CT imaging). This phase is often neglected; however, it can be used to assess
outcomes for the benet of the patient, the clinician for either critically evaluating
their outcomes and technique, or for research purposes (evaluating their outcomes
on a larger scale).
Table 1.1 Stages of computer-aided surgery
Step Tasks Examples
Data acquisition
phase
Planning phase – CT scan is imported into software
Manufacturing
phase
Surgical phase – Surgical phase is carried out in accordance
Assessment
phase
– Obtain clinical information
– Obtain pertinent patient history
– Obtain patient imaging
– Obtain STL les for potential patient
implants
program
– Virtual surgery is performed
– Virtual implants are manipulated and
placed, or patient-specic implants are
designed are targeted virtual surgery
– Patient-specic implants, splints, guides,
and hardware are fabricated using 3D
printers
with the virtually planned surgery using
guides, stents, and patient-specic
implants fabricated during the
manufacturing phase
Using intraoperative navigation and 3D
imaging to assess the virtual surgical plan
was achieved
– Laser scanning of teeth, bite,
and plaster models
– CT scan of hard tissues
– Choose hardware
manufacturer so STLS les
can be imported
– CT scan is imported
– Surgery is performed virtually
– Osteotomies and movements
are simulated
– Patient-specic implants are
designed
– Cutting guides and
positioning guides are printed
– Stents to reproduce
orthognathic movements are
printed
– Surgery is carried out using
custom guides
– Patient-specic implants are
placed
– Using intraoperative
navigation and postoperative
imaging to assess, bony
reduction, and implant
placement
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Computer-Aided Open Repair
Traditionally, open cranial vault remodeling has required manual planning of the
craniotomies and osteotomies to remodel the skull. This rather subjective process is
dependent on the surgeon’s expertise and creative vision to achieve the goal of normal skull shape and volume consistent with age-matched norms and expected
growth patterns. Computer-aided surgery has gained popularity in recent years in
head and neck surgery, having demonstrated positive impact in orbital reconstruction [13], orthognathic surgery [14], and more. This technology utilizes preoperative CT imaging to virtually plan an ideal surgical outcome prior to surgical
intervention. The data from this process is then used to manufacture sterile templates, which are utilized in the operating room to plan the osteotomies and cranial
reconstruction [15] (Fig.1.2). In craniosynostosis, computer-aided surgical planning has been shown to reduce operative time [16], although future research is warranted to describe the impact of this technology on cosmetic and neurologic
outcomes in craniosynostosis surgery.
Endoscopic andMinimally Invasive Techniques
In the late 1990s, Barone and Jimenez described their experience using endoscopic
strip craniectomy with adjunctive orthotic helmeting as an alternative to open cranial vault expansion. The endoscopic technique utilizes small incisions, under
which a burr hole is created. The endoscope is used for visualization as the periosteum is stripped from above the bone, and dura is stripped from below the bone. The
suturectomy is then performed using heavy scissors, ultrasonic bone aspiration, or a
high-speed drill. This technique results in reduced blood loss and need for blood
transfusion, smaller incisions, shorter operative time, and decreased hospital costs
compared to open techniques [17]. Since that time, a number of studies have supported the use of endoscopic strip craniectomy in sagittal, metopic, coronal, lambdoid, and multi-suture craniosynostosis with good outcomes. The utility of this
technique is limited after 3–6 months of age due to advanced deformity and
decreased effectiveness of helmeting. Helmeting carries the benet of being adjustable over time to optimize three-dimensional growth and is continued until adequate
head shape is reached or until 1 year of age.
Although poor outcomes in the historical literature would discourage the use of
strip craniectomy, it is important to note the difference in modern techniques.
Modern strip craniectomy must be complemented by augmentation of skull growth
by orthotic helmeting, springs, or distracting devices [18]. Spring-assisted cranioplasty uses metallic springs of various thickness to exert a constant force to reshape
the patient’s skull. Both springs and distractors have the advantage of producing
more predictable expansion in a known vector and can be used in older children, but
require a second operation for removal.
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a
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M. J. Recker et al.
d
c
Fig. 1.2 Isolated sagittal synostosis with switch cranioplasty for cranial vault remodeling. (a)
Bird’s eye and (b) lateral views of preoperative skull. Segmented skull viewed from (c) bird’s eye
and (d) lateral. Planned switch cranioplasty with expansion viewed from (e) bird’s eye and (f)
lateral. (g) Cutting guide to ensure accurate segmentation and safe distance from (h) sagittal sinus.
(i) Positioning guide for aligning cranial segments allowing for external plating. (j, k) Bicoronal
incision design with subgaleal dissection. (l) Cutting guide seated on cranium. (m) Cranial segments removed exposing underlying dura. (n) Internal view of cranial segments showing “copper
beaten” appearance indicating elevated intracranial pressure. (o) Bony segments xated according
to virtual plan and (p) reapplied to patient. Two-year postoperative result as viewed from (q) lateral, (r) frontal, (s) bird’s eye. (Reproduced with permission from Markiewicz MR, Recker MJ,
Reynolds RM. Management of Sagittal and Lambdoid Craniosynostosis Open Cranial Vault
Expansion and Remodeling. Oral Maxillofac Surg Clin North Am. 2022;34 (3):395–419)
e
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i
h
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j
Fig. 1.2 (continued)
k
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M. J. Recker et al.
lm
o
n
p
Fig. 1.2 (continued)
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rs
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Fig. 1.2 (continued)
Midface Advancement
Introduction
Craniofacial dysostosis refers to the syndromic form of craniosynostosis that
includes premature fusion of not only the cranial sutures but also the sutures of the
anterior skull base [19]. Notably, Apert, Crouzon, Carpenter, and Pfeiffer syndromes
are included in this family of malformations. Autosomal dominant defects in various broblast growth factor receptors (FGFRs) have been identied and implicated
in the pathogenesis of these syndromes. Unlike that of Apert and other such syndromes, the defects in Crouzon are largely limited to the head and face.
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Restricted skull base growth in craniofacial dysostosis results in severe midface
hypoplasia. This manifests as a concave “dish-face” prole, maxillary constriction,
a high-arched palate, and a parrot-beak deformity of the nose [20]. The shallow
orbits, which create a striking degree of exophthalmos, are also a consequence of
premature fusion at the cranial base. Bicoronal synostosis contributes to the brachycephalic head shape and hypertelorism. There are a variety of functional considerations in these patients. As with other forms of craniosynostosis, it is important to
evaluate for increased intracranial pressures and brain growth restriction. Concern
for either would mandate early surgical release of the involved sutures. Proptosis
can expose the eyeball to injury, and care should be taken to ensure that the cornea
is protected. Vision likewise needs to be assessed early on. Infants are obligate nasal
breathers, and the severe midfacial growth restriction can cause decreased nasal and
nasopharyngeal airway volumes. Obstructed nasal breathing during oral feeds in the
neonatal period can lead to failure to thrive and poor weight gain.
M. J. Recker et al.
Traditional Midface Reconstruction intheSyndromic Patient
The management of patients with syndromic craniosynostosis varies by center;
however, the generally accepted sequencing involves cranio-orbital surgery in
infancy, midface advancement in mid-childhood, and orthognathic surgery for
occlusal correction after skeletal maturity [19]. Global midface advancement is
achieved with a LeFort III osteotomy. If the supraorbital ridges are judged to be
well-positioned, a Monobloc advancement can be deferred. The goals of the LeFort
III operation are to normalize the projection of the inferior orbital rim, zygoma, and
maxilla. Obtaining a good Class 1 occlusal relationship is not a consideration at this
time as the dental discrepancies can be subsequently corrected in adulthood with
orthodontics and a LeFort I.The LeFort III procedure was originally described as a
single-staged procedure; however, with the advent of craniofacial distraction osteogenesis, there has been a strong preference toward progressively distracting the segments following craniofacial disjunction. Compared to the conventional approach,
midface distraction has been shown to reduce morbidity and relapse [21]. Distraction
also allows for larger advancements. Immediate rigid xation permits only 6–10mm
of stable advancement, whereas up to 20mm are possible with distraction [20].
Contemporary Treatment
Modern technology has improved the safety and predictability of the subcranial
LeFort III osteotomy. Piezoelectric devices allow for better protection of the orbital
soft tissues. The high-frequency vibrations that are transmitted to the metal instrument tip selectively cut mineralized tissues without collateral thermal damage to the
bone. Compared with mechanical saws, piezo devices have been shown to improve
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the speed and safety of the LeFort III procedure [22]. With respect to planning, the
simulated movements on computer-aided surgery translate to more accurate intraoperative movements (Fig. 1.3). For distraction, internal distractor guides can be
fabricated to ensure that the desired vectors are achieved [23]. Surgical guides can
also be made for the pterygoid plate and nasofrontal junction osteotomes (Fig.1.4).
The predicted movements have become so reliable in all planes of space that some
a
b
c
Fig. 1.3 Computer-assisted planning of LeFort III distraction with augmentation cranioplasty.
Preoperative (a) occlusion and (b, c) CT scan of head and face showing cranial defects and decient bitemporal and biparietal volume. (d) Planned orientation of internal distractors to achieve (e,
f) nal expected position of midface. (g, h) Heat map of bone to optimize the location of predictive
holes. (i, j) Design of custom cranioplasty implant using normative data to provide volume and
coverage. (Reproduced with permission from Schlieder D, Markiewicz MR. Craniofacial
Syndromes: The Le Fort III Osteotomy for Correction of Severe Midface Hypoplasia. Atlas Oral
Maxillofac Surg Clin North Am. 2022;30 (1):85–99)
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e
Fig. 1.3 (continued)
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f
g
h
Fig. 1.3 (continued)
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