Outcomes and Complications of Monobloc Versus Le Fort III Procedures for Treating Craniosynostosis: A Literature Review

Abstract

Background:

Craniosynostosis is a congenital disorder resulting in the early fusion of several bones in the skull, causing a deformity of the head and facial structures. The 2 most commonly performed surgical procedures to treat craniosynostosis include the monobloc and Le Fort III procedures. This literature review compares the functional and anatomical outcomes and complications between the monobloc and Le Fort III procedures for treating craniosynostosis.

Methods:

A PubMed search was conducted to identify studies assessing the outcomes following monobloc and Le Fort procedures. Data on anatomical changes, ophthalmic, airway, and neurological sequelae, as well as miscellaneous infectious or aesthetic complications were extracted from each study.

Results:

A total of 63 articles were included for analysis. The average length of midface advancement across distraction and nondistraction procedures was significantly higher in the monobloc cases (14.28 mm; 98.8% of patients with distraction) compared with Le Fort III cases (12.26 mm; 63% of patients with distraction) (P = 0.002). Both procedures exhibited similar rates of obstructive sleep apnea improvement. Cerebrospinal fluid leakage (69 of 373 monobloc patients; 15 of 448 Le Fort III patients) (P ≤ 0.001), seizures (8 of 373 monobloc surgery patients), and meningitis (9 of 373 and 2 of 448, monobloc and Le Fort III patients respectively) (P = 0.01) were observed.

Conclusions:

In summary, this review demonstrates that both the monobloc and Le Fort III procedures are effective in producing maxillofacial advancement and correcting craniosynostosis, with the monobloc procedure demonstrating significantly greater average advancement. Future research should investigate the comparison of aesthetic and obstructive sleep apnea outcomes further.

Takeaways.

Question: How do postoperative outcomes compare between the monobloc and Le Fort III procedures for treating craniosynostosis?

Findings: Increased midface advancement in the monobloc procedure with increased Cerebrospinal fluid leakage, meningitis, and seizure risk postoperatively was observed.

Meaning: Patients undergoing monobloc surgery exhibit increased postoperative midface advancement, often at the expense of neurological complications and infection risk.

INTRODUCTION

Craniosynostosis, which involves the premature fusion of bones of the skull, is one of the most common congenital facial disorders, occurring in 1 in 2000 live births.¹ Although 85%–86% of craniosynostosis is nonsyndromic, it can also be a consequence of various types of genetic syndromes, commonly Crouzon syndrome, Apert syndrome, and Pfeiffer syndrome.² These syndromic cases of craniosynostosis commonly involve the coronal sutures, thus shortening the skull in an anterior–posterior manner.³ Sagittal craniosynostosis affecting the sagittal sutures is the most common form overall, producing a long and narrow head.⁴

The medical complications of craniosynostosis are considerable if not treated. The increased intracranial pressure raises the risk of papilledema and intracranial hemorrhage.^5–7 Moreover, abnormal facial and skull structures often result in airway obstruction, leading to issues such as obstructive sleep apnea (OSA) and respiratory difficulty. Malformations of the orbits can also occur, leading to exorbitism and hypertelorism.⁸ Therefore, prompt surgical intervention is often needed to prevent future respiratory, cardiac, and neurological deterioration.

Two commonly performed surgical procedures that treat craniosynostosis include the monobloc and Le Fort III advancements. The monobloc procedure begins with a bicoronal incision, followed by a subfrontal osteotomy that isolates the frontal bone and midface skeleton from the remainder of the skull.^9,10 The concurrent extradural retraction of the frontal lobes may predispose to neurological injury.⁹ The splitting of the pterygoid bones from the maxilla and midface may also be performed.¹¹ Once the midface is isolated, distracting pins and devices can be placed in the cranial and facial bones to lengthen the distance between the 2 structures gradually.¹²

As opposed to the monobloc, the Le Fort III osteotomy involves incisions at the nasofrontal suture, zygomatic arch, and lateral and medial orbital walls to separate the midface from both the frontal bone and skull base.¹³ Therefore, rather than advancing the forehead along with the midface, the Le Fort III separates the frontal bone and superior orbit from the more inferior bones of the face. The nasal septum is also released from the skull, and the pterygoid plates are dissected from the maxilla bone. Like the monobloc procedure, many Le Fort III osteotomies involve distractors that gradually lengthen the midface conglomerate from the rest of the skull over several weeks.

Although the 2 procedures share the goal of advancing the facial bones forward, the variation in their separation points leads to disruption of different anatomical structures. The monobloc procedure involves a subfrontal osteotomy not performed in the Le Fort III procedure, leading to substantial manipulation and retraction of the frontal lobes. Contrastingly, the Le Fort III procedure is conducted in closer proximity to the eye and extraocular nerves than the monobloc procedure, potentiating damage to these structures with resulting vision impairment. Both procedures operate close to several crucial vascular structures at the pterygomaxillary junction, including the sphenopalatine artery, internal maxillary artery, and posterior superior alveolar artery.¹⁴ Although no particular surgery is generally preferred over the other by craniofacial surgeons, each has its own relative purposes. The monobloc technique is beneficial for the most severe cases of craniosynostosis involving elevated intracranial pressure, severe exorbitism, and severe airway obstruction, likely due to its substantial expansion of intracranial volume through advancing the frontal bone and midface simultaneously.¹¹ Le Fort III surgery is also preferred over the monobloc surgery in patients with class I or II dental occlusion, as opposed to class III, as the monobloc surgery can significantly advance the maxilla and thus worsen incongruity between the maxilla and mandible in overbites.¹¹

Due to the differing techniques involved in these 2 procedures, there is a need to assess the variation in outcomes between them. This literature review compares functional and anatomical outcomes and complications between the monobloc and Le Fort III procedures for treating craniosynostosis.

METHODS

A PubMed database search was conducted to identify retrospective reviews and case reports assessing outcomes in patients who underwent monobloc (Fig. 1A) and Le Fort III (Fig. 1B) operations. Specific outcomes included any mention of resolution of obstructive airway pathology or airway complications, ocular deformities or dysfunction, neurological complications, satisfaction with aesthetic outcomes, causes of infection, and other miscellaneous postoperative complications. The following search terms were used: (“Craniosynostosis” OR “Crouzon” OR “Pfeiffer” OR “Apert”) AND monobloc; (“Craniosynostosis” OR “Crouzon” OR “Pfeiffer” OR “Apert”) AND (“lefort” OR “le fort”). Exclusion criteria included review articles and articles not discussing syndromic craniosynostosis or articles that did not report clinical outcomes of concern. As such, the majority of craniosynostosis cases covered in this review were regarding syndromic bicoronal or coronal-predominant craniosynostosis. Data on relevant anatomical changes, ophthalmic, airway, and neurological sequelae, as well as miscellaneous infectious or aesthetic complications were extracted from each study. The average facial advancement accomplished with each procedure was also calculated based on the number of patients each article assessed.

Fig. 1.

Osteotomy lines for repairing craniosynostosis. A, Monobloc osteotomy lines depicting the pattern of the osteotomy cuts (highlighted in red) performed during the monobloc surgery. The procedure involves separating the frontal skull from the orbits and skull base, as well as cuts along the orbital floor and walls, and pterygomaxillary fissure to separate the midface from the skull base. B, Le Fort III osteotomy lines depicting the pattern of the osteotomy cuts (highlighted in red) performed during the Le Fort III surgery. The procedure involves separating the midface from the remainder of the skull through cuts along the orbital floor and walls, and the pterygomaxillary fissure.

Statistical Analysis

A two-tailed t test assuming unequal variance was conducted to analyze the statistical significance between the length of the midface and maxillary advancement after the monobloc and Le Fort procedures. A χ² test was used to assess differences in the proportion of patients who experienced resolution of sleep apnea, cerebrospinal fluid (CSF) leakage, and meningitis after each procedure.

RESULTS

A total of 63 articles were reviewed. Fifty-nine articles were found through the PubMed search, and an additional 4 were included through identification from the discussion sections of original articles.^11,15–76 (See table, Supplemental Digital Content 1, which displays the summary of article findings: inclusion of airway, neurological, ocular, and miscellaneous outcomes, https://links.lww.com/PRSGO/F339.) A total of 373 patients who underwent the monobloc surgery were identified, and 448 patients who underwent the Le Fort procedure were identified.

Anatomical, Ocular, Airway, and Neurological Outcomes

The average length of midface advancement across distraction and nondistraction procedures was significantly higher in the monobloc cases (14.28 mm; 98.8% of patients with distraction) compared with Le Fort III cases (12.26 mm; 63% of patients with distraction) (P = 0.002). Moreover, the monobloc surgery was shown to correct exorbitism and exophthalmos in 11 patients, with 2 patients experiencing a relapse of proptosis; 1 patient whose exorbitism was corrected underwent the monobloc procedure with subsequent Le Fort I osteotomy.⁵¹ Five patients who underwent Le Fort III osteotomy experienced resolution of exorbitism and exophthalmos. Moreover, both the monobloc and Le Fort procedures demonstrated statistically similar rates of improvement in sleep apnea; 75 of 105 (71.4%) patients demonstrated improvement or resolution of OSA or airway obstruction following the monobloc procedure, and 68 of 98 (69.4%) patients showed resolution or improvement in airway obstruction after the Le Fort III procedure (P = 0.75).

Complications

Multiple neurological and ophthalmic complications were observed in patients as well. CSF leakage (69 of 373 monobloc patients; 15 of 448 Le Fort III patients) (P ≤ 0.001), seizures (8 of 373 monobloc patients), and meningitis (9 of 373 and 2 of 448, respectively) (P = 0.01) were observed. However, 1 retrospective study of the monobloc procedure, which reported CSF leakage in 6 patients and postoperative epilepsy in 7 patients, observed a subset of patients who also underwent a Le Fort procedure in addition to the monobloc procedure.⁷⁷ Moreover, postoperative migration of cranial pins occurred in 6 patients who underwent the Le Fort procedure. Pin slippage was also described as a complication in 1 study of distraction in patients who underwent the Le Fort procedure.¹⁸ Multiple patients who underwent Le Fort osteotomy also experienced damage to the cranial bones and/or intracranial hemorrhage. Three patients experienced cranial bone fractures, with 1 occurring in the middle cranial fossa with a subsequent subarachnoid hemorrhage and death, 4 months postoperatively.²⁶ An additional patient experienced a puncture wound of the dura following distraction, and anisocoria, an internal carotid artery dissection, and subdural hemorrhage with uncal herniation, after 4 days postoperatively.²⁸

New-onset postoperative visual disturbances, including diplopia and reduced visual acuity, were reported in 3 patients who underwent the monobloc procedure and 3 patients who underwent the Le Fort procedure (Table 1). Additionally, there were 2 Le Fort patients who experienced optic nerve damage. Ocular cellulitis was reported to occur in 6 patients who underwent monobloc surgery.

Table 1.

Comparison of Key Outcomes Between Monobloc and Le Fort III Patients

	Monobloc	Le Fort III
Total no. patients	373	448
Average midface advancement, mm	14.28*	12.26*
Exorbitism correction/improvement	11	5
Obstructive airway resolution, n/N (%)	75/105 (71.4)	68/98 (69.4)
CSF leakage, n/N (%)	69/373 (18.5)*	15/448 (3.3)*
Meningitis, n/N (%)	9/373 (2.4)*	2/448 (0.4)*

*P < 0.05.

DISCUSSION

In summary, this review demonstrates that both the monobloc and Le Fort III procedures are effective in producing maxillofacial advancement and correcting craniosynostosis, with the monobloc procedure demonstrating significantly greater average advancement. Both operation techniques show similar efficacy in alleviating sleep apnea. However, proportionately more patients undergoing monobloc surgery were reported to experience CSF leakage, meningitis, and seizures postoperatively compared with patients undergoing Le Fort III procedures. Nevertheless, multiple patients undergoing Le Fort surgery experienced instability of cranial pins and intracranial hemorrhage. Both procedures are associated with ocular complications, including proptosis, diplopia, and optic atrophy (Supplemental Digital Content 1, https://links.lww.com/PRSGO/F339).

This review comprehensively assessed neurological, infectious, ophthalmic, and airway outcomes after the monobloc and Le Fort III procedures. In addition, this is the first review, to our knowledge, concluding a significant difference in midface advancement between the monobloc and Le Fort III procedures. However, multiple other systematic and literature reviews have compared postoperative outcomes between the 2 procedures. Knackstedt et al⁷⁸ completed a literature review comparing the 2 procedures, similarly reporting a higher rate of CSF leakage and meningitis in patients undergoing the monobloc procedure compared with the Le Fort procedure. Moreover, they found that patients who underwent distraction with monobloc surgery experienced significantly higher rates of CSF leakage and infectious complications compared with those without distraction; patients who underwent the Le Fort surgery did not exhibit the same disparities between distraction and the lack thereof.

In this review, 11 (3.42%) patients who underwent monobloc surgery were reported to experience resolution of exorbitism following the procedure, compared with 5 (1.2%) Le Fort surgery patients. Although both procedures demonstrated efficacy in correcting ocular deformities, previous studies have shown that advancement following the Le Fort procedure is characteristically around the midface and nasal structures, whereas that of the monobloc procedure is predominantly in the fronto-orbital region.⁷⁹ Future research should investigate whether this variation could impact the effectiveness of each surgical technique in resolving exorbitism and any consequent ocular dysfunction. Moreover, this review revealed no significant difference in OSA improvement and resolution between the monobloc and Le Fort procedures, as they both resulted in advancement of the midface with increased airway volumes.⁸⁰

Although our study found that both the monobloc and Le Fort procedures resulted in improved facial aesthetics as reported by the patients, the movement of the midface and fronto-orbital region simultaneously may offer some improved aesthetic benefit due to a coherent advancement. Future studies should compare subjectively reported satisfaction with postoperative facial aesthetics of patients between the Le Fort and monobloc procedures.

This review determined that significantly more patients who underwent monobloc surgery were likely to experience CSF leakage and neurological infections, such as meningitis, compared with patients who underwent Le Fort surgery. Other studies have found comparatively high rates of neurological complications in the monobloc patient population. A meta-analysis assessing 363 patients, conducted by Knackstedt et al,⁷⁸ found patients undergoing the monobloc procedure to be significantly more likely to endure CSF leaks, reoperation, meningitis, and death following operation compared with patients undergoing the Le Fort III procedure. The relatively higher rates of complications may be attributable to the neurologically invasive nature of the monobloc surgery; the frontal lobe must be retracted to mobilize the cranial bones during the monobloc osteotomy. A retrospective study by Cobb et al⁹ identified that 64% of their cohort undergoing monobloc surgery experienced ischemia in the frontal lobe, identifiable on computed tomography imaging, ranging from mild changes to large infarcts. The authors attributed these changes to the substantial retraction needed to complete the osteotomy. The movement of the frontal bone also produces a dead space between the skull and the brain matter, allowing for infection and abscesses to form.⁸¹

Of particular interest are the findings presented by Bradley et al⁵² in a retrospective review comparing rates of CSF leaks, meningitis, and wound infections in patients of syndromic craniosynostosis undergoing either a conventional monobloc procedure with immediate advancement or a monobloc with gradual internal distraction starting 1 week postoperatively. About 42% of patients undergoing the conventional procedure experienced meningitis, 25% experienced a CSF leak, and 42% experienced a wound infection. None of the patients undergoing the distraction procedure experienced either CSF leakage or meningitis, and only 8% experienced a wound infection. The reduced morbidity experienced by patients with distraction can be explained by several factors. The gradual advancement accomplished with distraction allowed for less significant dead space behind the frontal bone compared with the monobloc procedure with immediate advancement.⁸² Moreover, the gradual lengthening allowed the nasofrontal sinus to remucosalize, permitting better tissue healing.⁸² Gradual distraction also demonstrated evidence of reduced blood loss compared with intraoperative advancement, which could reduce subsequent complications as well.^52,82 Therefore, future decisions to involve gradual distraction or immediate advancement should weigh these risks on a patient-by-patient basis, considering their risk factors.

Contrastingly, distraction, especially with a halo pin device, presented a significant risk of pin loosening, leading to superficial skin infections and possible dural puncture.^54,83 However, certain halo pin designs, specifically a trochar-style, may tolerate higher mechanical pressure than others and could be less prone to loosening.⁸⁴ Moreover, a retrospective study by Nemeth and Mattingly⁸⁵ displayed that higher pin numbers improved device stability with a higher threshold of mechanical failure.

Despite the significant risk of neurological complications in patients undergoing the monobloc procedure, 2 patients experienced an internal carotid artery dissection following the Le Fort III procedure. Nout et al²⁸ attributed this risk to neck tissue trauma during the manipulation and movement of the midface bones. Moreover, the patient in this case report had previously undergone a monobloc procedure, increasing the density of scar tissue in the surgical site and the subsequent risk of vascular trauma.

Two patients analyzed in our study experienced an intracranial hemorrhage. A rare, yet noteworthy, case of subarachnoid hemorrhage was described by Matsumoto et al,³¹ in which the team used a curved osteotome to separate the pterygoid and maxilla in their Le Fort III procedure. The force from the separation was believed to have pushed the pterygoid posteriorly and subsequently transferred pressure to the sphenoid bone, ultimately fracturing the skull base. Irregular fracture patterns have been shown to increase the risk of intracranial hemorrhage in the Le Fort procedures.⁸⁶ Several studies, however, show various fracture outcomes with alternative devices. A cohort study by Burgaz et al⁸⁷ found that using a piezoelectric device to separate the pterygoid and maxilla in Le Fort osteotomies resulted in significantly more favorable fracture patterns along the divide between the 2 bones, whereas using a curved osteotome through a buccal approach resulted in significantly more fractures anteriorly or posteriorly to the divide. Another cohort study found that an ultrasonic bone saw performed even more favorable separations than a piezo and bur device.⁸⁸ Such methods should be investigated further to compare their direct relationships to intracranial hemorrhage in the Le Fort procedures.

The existing literature reports a wide range of cephalometric measures to evaluate in patients undergoing the Le Fort III or monobloc procedures. Rostamzad et al^79,89 measured advancement of soft tissue landmarks, such as the nasion, lateral canthi, and medial canthi; and skeletal landmarks, such as the right and left dacryon, zygion, and orbitale; then advancement ratios between soft tissue landmarks and respective skeletal landmarks were reported. Other measures involving 3-dimensional facial assessment include maxillary advancement and stability.⁵² Given that ophthalmological abnormalities are often indications for craniofacial surgery, several studies and case reports evaluated the correction of exorbitism, reduction in proptosis, increase in orbital volume, and degree of globe protection postoperatively.^90–92 Despite the challenge in measuring it, postoperative upper airway volume is vital to track to record improvements in sleep quality and resolution of OSA.^15,91 Notably, some articles examined patient-centered outcomes, including aesthetic perception and the child’s improvement in sleep quality and cognition, as reported by parents, following surgery.^93,94 Our review focused on studies that reported clinical outcomes, such as vision improvement or resolution of OSA. This limited the number of articles included, as some studies had solely focused on anatomical outcomes.

The reporting of data in this review was further limited by the variable outcomes included in observational studies. Many papers might have omitted how many patients were diagnosed with OSA, proptosis, or other ocular pathologies preoperatively, thus limiting our calculation of resolution rates for these conditions between the 2 procedures. Moreover, the significance of the variation in midface advancement between the Le Fort and monobloc procedures may be limited by the extent to which individual surgical teams decided to advance the facial bones through distraction, rather than due to the nature of the operation itself. Lastly, the net movement of midfacial bone structures, such as the maxilla and zygomatic bones, may differ from the intended distraction length. For instance, the angle of force applied with the distractor devices impacts the extent of anterior movement of the nasion and orbitale in Le Fort III distraction.⁹⁵ The use of external distractors in monobloc surgery may also lead to disparity between the extent of upper and lower midface advancement postoperatively.⁵⁶ Based on these data, the decision was made to ultimately exclude distraction length values, reported without concurrent midface advancement numbers, from the studies we assessed when calculating average midface advancement. Moreover, the argument can be made that the significant difference in midface advancement can be attributed to the relatively higher proportion of monobloc patients (98.8%) who underwent distraction in our cohort versus Le Fort III patients (63%). However, when patients who underwent distraction in both groups were compared, the difference in midface advancement remained significant (monobloc, 14.3 mm; Le Fort III, 12.5 mm; P = 0.03). The methods for determining midface advancement may also differ among studies, inevitably resulting in variation in these values among the articles we assessed.

In conclusion, patients undergoing monobloc surgery for craniosynostosis repair exhibit increased postoperative midface advancement compared with patients undergoing Le Fort III surgery, often at the expense of a higher risk of neurological complications and infections. Moreover, both operative techniques possess a strong capability of correcting or improving OSA caused by craniosynostosis. In addition, the choice to complete either of these procedures with gradual distraction or immediate advancement should be done on an individualized patient basis, as the risk of complications, such as CSF leakage and meningitis, is substantial with distraction. Future research should investigate subjective patient satisfaction with aesthetic outcomes between both the monobloc and Le Fort procedures. There is an additional need to assess the relationship between the variation in midface and fronto-orbital advancement and the ability of each procedure to effectively repair OSA and proptosis.

DISCLOSURE

The authors have no financial interest to declare in relation to the content of this article.

Supplementary Material

gox-14-e8193-s001.pdf ^{(331.6KB, pdf)}