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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_892_Библиотеки_им_академика_М_И_Перельмана
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M. J. Recker et al.
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Fig. 1.3 (continued)
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Fig. 1.3 (continued)
surgeons are performing simultaneous LeFort I and III advancements [24]. When
the midface and the maxilla are simultaneously and independently osteotomized,
less movement is required for each piece to reach proper occlusion. This is useful
for cases of soft tissue restriction or when a single-staged surgery is desired. Finally,
virtual planning allows surgeons to design and guide unconventional osteotomies
that would be difcult to execute in a free-hand style. This has led to the creation of
“modied” LeFort II/III osteotomies through a combined transoral and transconjunctival approach [25]. The concealed access of these modied procedures spares
the morbidity and external scarring of a coronal ap, although they do not permit for
nasofrontal advancement.
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Pierre Robin Sequence
Introduction
Pierre Robin sequence, or Robin sequence (RS), is a rare congenital anomaly characterized by a clinical triad of micrognathia, glossoptosis, and upper airway obstruction [26]. In RS, the precipitating event of an underdeveloped mandible initiates the
subsequent cascade of tongue base retropositioning, possible palatal clefting, and
respiratory and/or feeding difculties. The cleft palate of RS is generally U-shaped
and wider than that seen with other cleft conditions. Furthermore, the RS mandible
is morphologically abnormal with a shorter ramus and a more oblique symphysial
angle [27]. RS may occur in isolation or as part of an underlying genetic syndrome.
Isolated RS comprises between 20% and 40% of cases [28, 29]. The precise etiology of mandibular retrognathia in these isolated cases is unknown but may be
related to sporadic mutations of the SOX9 gene; however, this has not been proven
with convincing data [30]. Because no single genetic locus has been found to be
consistently altered across patients, isolated RS may also stem from environmental
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M. J. Recker et al.
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Intraoperative implants and guides. Cranioplasty implants (a) t to model and (b) patient.
Fig. 1.4
(c) Stereolithographic model showing pertinent anatomy and planned osteotomies. (d) Internal
distractor t to model. (e) Nasofrontal osteotome guide ensuring safe orientation away from anterior skull base. Imaging (f) immediately after distractor placement and (g) after completion of
distraction. (h) Excellent postop occlusion obtained with skeletal advancement. (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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f
g
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Fig. 1.4 (continued)
inuences of intrauterine growth restriction [31]. This environmental theory would
account for the postnatal catch-up growth observed with some patients. On the contrary, syndromic patients with RS are believed to present with a primary mandibular
growth disorder. Stickler syndrome followed by velocardiofacial syndrome are
most commonly associated with RS, although over 50 named syndromes are known
to present with features of RS.It is important to note that some researchers have
found that neither isolated nor syndromic RS patients exhibit meaningful catch-up
growth. This discordance highlights the fact that, although the clinical consequences
of micrognathia are well-known, the precise etiology and long-term trajectory of RS
are poorly understood.
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M. J. Recker et al.
Traditional Repair
Infants with RS can present along a broad spectrum of respiratory and feeding difculties, and surgical interventions are aimed at improving these issues. Nonoperative
measures for relieving airway obstruction include prone positioning, positive airway pressure, and intubation. It is important to verify tongue base collapse with
endoscopy and rule out other potential confounding conditions such as hypotonia,
central apneas, and laryngomalacia. In the authors’ experience, the decision to treat
the mandible in cases of suspected RS is not always straightforward especially in
the setting of multiple contributing comorbidities. In patients who have multifactorial drivers of poor weight gain and disordered breathing, tracheostomy and gastrostomy tube placement reliably provide a denitive means of ensuring spontaneous
respirations and adequate nutrition.
The routine and permanent use of tracheostomy and gastrostomy tubes should
not be the treatment of choice to circumvent oropharyngeal collapse. These interventions are considered a last resort after all other options have been exhausted. A
variety of targeted interventions have been developed to treat the anatomic anomalies of RS in order to avoid the need for tracheostomy/gastrostomy. Tongue–lip
adhesion (TLA) aims to hold the tongue in protrusion by pexying it to the lower lip.
This adhesion is generally maintained for 12months; however, the exact timing of
take down is individualized based on patient requirement and the capacity for catch up growth in the mandible. If a cleft palate exists, the release of the TLA is generally
deferred until 2–3months after palate repair assuming that it is safe to detach the
tongue at that time. The benet of TLA is that the effects are immediate, and the
procedure is well-tolerated with little need for specialized home care afterwards.
The literature supports the use of TLA for cases of mild obstructive sleep apnea
(OSA); however, recent experiences out of high-volume craniofacial centers have
demonstrated that mandibular distraction osteogenesis (MDO) consistently outperforms TLA across all endpoints [32]. MDO treats the primary deformity by lengthening and projecting the mandible. MDO involves performing a posterior body
osteotomy, applying mechanical distractors, transporting the free segments, and
allowing for bony consolidation of the intervening callous. Following a brief latency
period (often unnecessary in infants), the distraction is generally performed at a rate
of 1 to 2mm per day until the patient becomes slightly overcorrected and prognathic. We use the relationship of the upper and lower alveolar ridges as a guide to
judge lower jaw position. The distractor arms are removed once distraction is completed; however, a secondary procedure is still required to take out the remaining
hardware after a couple months of consolidation.
Mandibular distraction, as rst described by McCarthy, was initially performed
using external devices with transcutaneous pins. In the early 1990s, external distractors were the standard method for mandibular distraction. These external devices
are still used in select circumstances with the main advantage being that the distraction vector can be altered and adjusted during the period of activation. In resourcelimited settings given their reusability, reduced surgical time, and lower overall
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treatment costs, external distractors are often still employed. Although infants generally tolerate the external appliance, the multiple pin sites are susceptible to infection and postremoval scarring. In the late 1990s and early 2000s, external distractors
were largely supplanted by lower-prole internal distractors with percutaneous distraction arms. These semi-buried devices have a unidirectional ratchet that prevents
backwards activation and provides a safety mechanism against inadvertent movements. The limitations to these appliances are that the vector cannot be altered once
the device is buried and that removal requires a revisit to the operating room to
uncover and retrieve the device.
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Contemporary Treatment
As in other areas of craniofacial surgery, computer-aided surgical planning has drastically improved the technique and safety of MDO. The accuracy of computerassisted distraction cannot be understated. A series out of Spain found that their
nal screw placement was consistently within 1mm of their plan and that angular
deviations of their osteotomy line were less than 4 degrees off-axis [33]. This conrms the notion that surgeons are able to reliably and accurately execute their virtual plan. Dental complications of MDO are well-known and some are certainly
unavoidable given the limited availability of bone stock and age at which RS patients
are treated [34]. Computer-aided surgical planning allows surgeons to plan the osteotomies away from tooth buds and the inferior alveolar nerve to optimize tooth
development. Multiangular osteotomies can be designed for this purpose. Likewise,
the predictive holes can be registered and pre-drilled through the same osteotomy
cutting guide in order to minimize trauma to the developing structures. The thickness of the bone can be measured to guide appropriate screw selection. Although
MDO is performed with a straight-line advancement, computer-aided surgical planning assists with choosing the optimal vector and with matching this vector on both
sides of the mandible. When the distraction is simulated, the MDO gap can be measured, and the duration of activation can be predicted. Stereolithographic models are
used to preoperatively adapt the footplates for ease and time-savings (Fig.1.5). To
the best of our knowledge, custom-milled or printed internal distractors are not
commercially available at this time; however, patient-specic distraction hardware
may be in the pipeline as such devices would further reduce surgical deviation from
the proposed plan.
Some of the challenges with computer-aided surgical planning, in addition to the
cost of the technology, include data acquisition and manufacturing lead time. CT
scans are required to capture the cross-sectional anatomy, and the exposure of
infants to ionizing radiation is a valid concern. In our experience, infants often need
intubation and general anesthesia to eliminate motion artifact especially, because
repeating a CT for poor image quality is difcult to justify when the anatomy can be
visualized and the sole purpose is to obtain accurate surgical guides. Many RS
infants also have difcult airways that require high-risk intubations by skilled
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Fig. 1.5
Patient with Robin sequence (RS) planned for mandibular distraction. (a, b) Internal
distractors placed virtually with simulated movement. (c) Oblique osteotomy planned away from
tooth buds with depth measurements of pertinent anatomy. (d) Cutting guide registered on patient
model. (e) Preoperative markings showing planned incision. (f, g) Intraoperative access with
excellent guide t and distractor adaptation. (h) Immediate postoperative result showing distractor
arms exiting anteriorly. (i) Symmetric advancement with overcorrection to Class III relationship.
(j) Improved mandibular projection appreciated at the time of distractor removal
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g
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Fig. 1.5 (continued)
specialists. As a result, extubating these patients after CT is not always advisable.
Finally, although the lead-time for obtaining patient models and guides has
decreased in recent years, at least 7days is generally required between planning
session and surgery date. In most cases, this period of time is not prohibitive to
using computer-aided surgical technology, and with the expansion of in-house
printing capabilities at more and more centers, we anticipate that the manufacturing
time will continue to shorten.
Hemifacial Microsomia andTreacher Collins Syndrome
Introduction
Both hemifacial microsomia (HFM) and Treacher Collins syndrome (TCS) are congenital conditions arising from the abnormal development of the rst and second
branchial arches. HFM, which is better termed craniofacial microsomia, is the
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second most common congenital anomaly of the face following cleft lip and palate.
The term Goldenhar syndrome is used in the presence of internal organ and vertebral alterations. The incidence of HFM lies between 1in 3000 and 5000 births. The
precise etiology of HFM is unknown; however, the prevailing theory implicates an
in-utero vascular event affecting the stapedial artery, which in turn results in massive tissue injury in the characteristic distribution. Experiments provoking a stapedial artery hematoma in mouse embryos have successfully replicated the HFM
phenotype [35]. The branchial arches are derived from neural crest cells, and failed
migration is thought to also play a role in the pathogenesis. There is also a potential
genetic contribution to HFM, as higher rates of HFM have been identied among
rst degree relatives and an autosomal dominant inheritance pattern has been
observed. Classically, HFM affects boys more commonly than girls, and although
10% of cases have a bilateral presentation, the right side is affected more severely
and commonly than the left. The reasons for this pattern are poorly understood. The
OMENS classication of HFM is the most commonly used nomenclature for stratifying disease severity. The OMENS system encompasses the anatomic spectrum of
craniofacial deformities seen in HFM, namely, the orbit, mandible, ear, facial nerve,
and soft tissue.
TCS, also known as mandibulofacial dysostosis, likewise manifests as an underdevelopment of the rst two branchial arches. TCS is much rarer than HFM, arising
in 1in 50,000 births, and is most frequently caused by mutations to the TCOF1
gene, which is inherited in an autosomal dominant fashion. Despite their similarities, there are a few distinguishing features between HFM and TCS.TCS is always
bilateral with fairly symmetric facial hypoplasia. The malar depression, sunken
cheek appearance, and downward slating of the palpebral ssures are much more
profound in TCS. TCS also has a higher rate of palatal clefting and transverse maxillary constriction, whereas in HFM there is a tendency to see Tessier 7 clefting and
macrostomia from failed fusion of the maxillary and mandibular processes.
Although the Kaban–Pruzansky classication of mandibular deciency is integrated
as part of the OMENS classication for HFM, the Kaban–Pruzansky classication
is also an acceptable taxonomy for describing the TCS mandible given the morphologic similarities.
M. J. Recker et al.
Traditional Repair
A wide range of severities exists for both HFM and TCS.In infancy, the early treatment goals are aimed at relieving airway obstruction, correcting orofacial clefts,
and addressing any vision and hearing abnormalities. Some surgeons will elect to
intervene and operate on the facial bones during active growth with the intent of
minimizing psychosocial stress and intercepting growth to limit the magnitude of
secondary craniofacial deformities. Similar to other dentofacial deformities, denitive skeletal and soft tissue correction are best postponed until after skeletal maturity. Maxillomandibular growth is completed around 16–18 years with skeletal
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maturity being reached later for boys than girls. The cranium and orbit generally
can be corrected earlier, at around age 10, because skull growth is complete at that
time. Likewise, for HFM, the growth of an unaffected ear is completed at around
7 years, so auricular reconstruction of the malformed ear can be done any time
after then.
Similar to RS infants, OSA secondary to mandibular retrognathia is treated with
either TLA, MDO, or tracheostomy. Because severe expressions of HFM and TCS
present with an absent ramus-condyle unit (RCU), MDO may not be feasible in
infancy given the poor retromolar bone stock. Therefore, it may be prudent to obtain
a plain lm prior to submitting the patient to a CT for surgical planning. Among
children with grade 2b and 3 mandibular morphology, Kaban and Pruzansky have
traditionally recommended early mandibular reconstruction to keep pace with normative growth. Their preference toward early intervention was motivated by the
aforementioned reasons with the thought that doing so would simplify subsequent
corrections at maturity. Furthermore, without staging the reconstruction, the soft
tissue envelope in adulthood may not be able to accommodate the sudden stretch
required to make the necessary skeletal movements. Still, despite the intuitive logic,
the benets of early interceptive surgery have yet to be proven [36].
At the time of Kaban and Pruzansky’s publication, RCU reconstruction had primarily been achieved with costochondral grafting. The rib graft is a relatively simple harvest and does not require any additional imaging outside of a chest X-ray. If
the periosteal sleeve of the rib is preserved and reapproximated in children, a neorib can regenerate to ll the donor defect. Costochondral grafts in younger patients
have the purported benet of conferring growth potential so long as care is taken to
ensure that the cartilaginous cap remains attached. Unfortunately, the overwhelming consensus is that costal cartilage growth is unpredictable [37]. Some believe the
amount of growth is a function of the size of the cartilaginous cap that is attached to
the graft.
In the early 1990s, when distraction of the maxillofacial complex gained popularity, vertical ramus distractors became another popular option for RCU reconstruction. As with mandibular distractors, the rst such devices were externally
xated. Some patients planned for distraction may require an initial bone graft to
create a surface to attach the posterior foot plate. Mandibular distraction for HFM
and TCS often requires a multivector or a curvilinear pathway to simultaneously
advance, vertically lengthen, and counterclockwise rotate the mandible. In the
absence of a glenoid fossa, it may be hard to ensure that the transported bone reaches
a suitable landing point. It is often the case that the distracted condylar segment
ends up far away from the external auditory meatus in a position too medial and
anterior to give any meaningful function.
The orbito-zygomatic complex is another region that maxillofacial surgeons are
often challenged with reconstructing. The rudimentary malar bones can be osteotomized and advanced, raised, and lateralized to improve projection. A split calvarial
bone graft is often used for augmentation because of its good take, low absorption
rates, and existing availability through the same coronal access used to approach the
upper midface [38]. Iliac crest bone can also be harvested to but is less preferred.
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