Mohammed Almuzian,1 Josh Rowley,2 Hisham Mohammed,3 Mark B. Wertheimer,4 Aman Ulhaq5 and Samer Mheissen*6

Introduction

Le Fort I maxillary advancement surgery has been used widely to correct maxillary retrognathia in patients with a class III malocclusion and concave profile. The goal of such a procedure is to achieve a good occlusion and to improve facial harmony.1Although Le Fort I osteotomy affects the facial soft tissue at different degrees, the effect is mainly concentrated at the region of the upper lips and the base of the nose. The approximate ratio of nasolabial soft to hard tissue changes secondary to maxillary advancement is not well defined; therefore, estimating these changes is of vital importance.2

Traditionally, two-dimensional (2D) lateral cephalometric radiographs are utilised for both pre-surgical planning and prediction as well as post-surgical evaluation of outcomes.3 However, the accuracy of algorithms intended to forecast 2D-profile soft tissue changes as a result of skeletal movements is limited, owing to overlapping radiographic structures that do not represent the three-dimensional (3D) object.2 On the other hand, 3D virtual models and surgical planning are useful for accurate prediction and informed patient counselling.4,5 Several techniques to capture and analyse the 3D digital images of the soft and hard tissue are available, and these include surface and volumetric methods. Computed tomography (CT),6 cone beam CT (CBCT) and magnetic resonance imaging (MRI) fall under the umbrella of volumetric methods. Poor surface texture and resolution can limit the accuracy and reproducibility of landmarks acquired from CT/CBCT renderings, allowing only rough evaluation. However, 3D surface imaging methods including stereophotogrammetry7and laser surface scanning8 overcome these drawbacks, making them the superior methods of acquiring the 3D anatomy of the facial soft tissue.9 Recent studies validated the use of stereophotogrammetry for that purpose.4,5

Quantifying 3D soft and hard tissue changes in response to jaw surgery can be achieved using linear, angular and volumetric surface measurements,10,11 using reliable software such as Dolphin, 3dMD Vultus and Maxilim.12,13,14,15,16 However, the measured and quantified 3D soft to hard tissue changes as a result of jaw surgery vary among the studies and mainly focus on combined jaw surgery.13,14,15,16 A recent narrative systematic review17 with no prior registration tried to explore the 3D soft tissue effects of maxillary structures; however, the study included different types of jaw surgery (bimaxillary, surgically assisted rapid maxillary expansion procedures and Le Fort I advancement/setback/impaction) which were used to treat different types of malocclusion, including class III malocclusion and facial asymmetry. Consequently, the author of that review could not present the combined pool estimate. Therefore, the literature lacks consensus regarding the quantity of 3D soft tissue changes secondary to isolated maxillary advancement surgery in class III malocclusion with maxillary retrognathia. The aim of this systematic review and meta-analysis was to investigate and quantify the 3D nasolabial soft tissue changes of isolated Le Fort I maxillary advancement surgery in skeletal class III individuals.

Materials and methods

Protocol and registration

The authors followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines18,19 to develop the study protocol. The present systematic review was conducted according to the guidelines of the Cochrane handbook for systematic reviews of interventions (version 6)20 and was reported according to the PRISMA statement.21 The study protocol was registered with PROSPERO (CRD42019132151).

Eligibility criteria

Table 1 describes the main research question, which was defined in PICO format. Case reports, case series, studies using 2D images, review articles, in vitro and animal studies, editorials and opinions were excluded. Moreover, studies that included syndromic patients, patients with cleft lip and/or cleft palate or surgery relating to pathology/trauma were excluded. Studies that included osteotomies other than isolated Le Fort I osteotomy - including bimaxillary orthognathic procedures, genioplasty procedures and multiple sectioning of the maxilla - were also excluded. Only studies with more than six months of follow-up after surgery, to allow for reduction in swelling, were included.

Table 1 PICOS format of the review question
Full size table

Information sources and search strategy

Six electronic databases (Medline and Embase via Ovid, Cochrane Library, Scopus, LILACs via Virtual Health Library and Web of Science) were searched for published, unpublished and ongoing studies up to 4 December 2020. Specific search strategies using keywords, truncations and Boolean operators were developed for each database (Table 2) with the guidance of an experienced librarian at the University of Edinburgh. The electronic search was supplemented by search of the reference lists in selected articles, as well as manual search in all available issues (Table 2) at the Library of the University of Edinburgh until 11 November 2020. There was no search restriction on date or language. The grey literature was also searched using OpenGrey (www.opengrey.eu). Authors were contacted via e-mail when it was deemed necessary. Electronic searches were undertaken by two review authors (SM and MA) and a manual search was undertaken by one review author (MA). All the references retrieved through the search strategy were exported into and managed using EndNote version X7.8 (Clarivate, Philadelphia, PA, USA). Microsoft Word and Excel (Microsoft Corporation, Redmond, WA, USA) were utilised for management of data extraction and completion of the report.

Table 2 The search strategy for MEDLINE on which other searches were based
Full size table

Study selection

Two independent reviewers (JR and AU) screened, in duplicate, titles and abstracts using the eligibility criteria. Full texts were also examined independently and in duplicate for eligibility. Any disagreements, if presented, were resolved by consensus and discussion with a third reviewer (MA). The degree of agreements in every step was tested using the Kappa test (Kappa 0.94), though a recent guideline discourages its use.20

Data items and extraction

Data were extracted independently by two reviewers (JR and MA) using a pro forma. Data extraction involved items related to participant information, type of intervention, method of evaluation and the outcomes. Disagreements between the reviewers were resolved through discussion, and if needed, via consultation with a third reviewer (AU). It was pre-planned to contact corresponding authors if additional information was needed. The 3D effect of Le Fort I osteotomy on soft tissues was undertaken by comparing pre- and post-surgical data.

Risk of bias in the individual studies

SM and MA assessed the risk of bias for each study using the quality assessment of controlled intervention studies (https://www.nhlbi.nih.gov/health-topics/study-quality-assessment-tools). Disagreements between the reviewers were resolved through discussion, and if needed, via consultation with a third reviewer (AU). This checklist was developed for medical studies and was adapted for use in orthognathic surgery studies.22 The bias assessment tool for all included articles was analysed to give an overall quality rating found in Table 3. The quality of the included studies was rated as good quality (9-12 'yes' answers), fair quality (5-8 'yes' answers) or poor quality (1-4 'yes' answers).

Table 3 Quality assessment of the studies included in the review (NA = not applicable, NR = not required)
Full size table

Summary measures and approach to data synthesis

Quantitative analysis of the assigned studies was pre-planned to be conducted by SM using Review Manager (RevMan, version 5.4.1, Copenhagen; The Nordic Cochrane Centre, The Cochrane Collaboration, 2020). It was pre-planned to undertake statistical synthesis, if possible, by inspecting the included studies with respect to the population groups, described variables, study design and outcome reporting. The statistical heterogeneity detection was pre-planned using Tau2 and I2.23 If there was a substantial statistical heterogeneity (I2 >50%), the random-effect model would be adopted. Otherwise, the fixed-effect model would be used. The continuous data were expressed using the mean difference and 95% confidence interval (CI).23 However, the narrative description of the findings was pre-planned to be used if significant clinical and methodological heterogeneity of the included studies was present.

Risk of bias across studies and additional analyses

For the quality of the evidence, the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach was used.24 The authors decided in advance to use sensitivity and subgroup analyses, if possible. Also, the authors pre-planned to detect the potential publication bias in a meta-analysis using Egger's linear regression test,25 and by visually inspecting a generated contour-enhanced funnel plot if the number of included trials that address the same intervention and outcome was sufficient (>10 trials).

Results

Selection of the studies

The selection of studies is summarised in the PRISMA flowchart (Fig. 1). The initial search resulted in 1,092 records. After removing the duplicates, 822 articles remained. Reviewing the 822 titles and abstracts led to excluding 783 articles. Thirty-nine articles were identified for full-text reading. Thirty-five articles were excluded because of various reasons (Figure 1 and online Supplementary Table 1). Finally, four studies were included in this systematic review26,27,28,29 and were pooled in meta-analysis.

figure 1

PRISMA flow diagram

Characteristics of the studies

Characteristics of the included studies are presented in Table 4. The included studies were two prospective studies28,29 and two retrospective studies,26,27 with a total of 105 patients (mean age 16.7 ± 33.9 years). All patients underwent maxillary advancement osteotomy in isolation and were followed up for at least six months after the surgery. The overall mean of the amount of maxillary advancement in the included studies was 5.58 mm (95% CI 5.20-5.96). Two studies were undertaken in the US26,27 and the others in Germany28 and Slovenia.29

Table 4 Characteristics of potential articles related to aim of the report and participants (M = male, F = female, ND = not described)
Full size table

Different methods were used to assess the nasolabial soft tissue changes, with some studies26,27 using direct linear and angular anthropometric parameters measured separately on pre- and post-surgery 3D renderings. Two studies evaluated the soft tissue changes in the whole face,28,29 while two of the included studies26,27 evaluated changes in the nasal and upper lip regions of the face. Included studies used either 3D photogrammetry26,27 or optical 3D surface scan28,29 to acquire soft tissue scans. MRI or CT were not used in any of the included studies.

Risk of bias within studies

Risk of bias assessment for the included studies is summarised in Table 3. All studies received a fair score, indicating a high risk of bias owing to the lack of sample size calculation, lack of blinding of researchers and no mention of intention-to-treat or per-protocol analysis in the prospective trials.

Results of individual studies and data synthesis - soft tissue changes

Nasolabial soft tissue changes were pooled into two main categories based on the outcomes and the measurements: nose and lip changes. All of these occurred as a result of 5.58 mm (95% CI 5.20-5.96) of maxillary advancement as reported by the included studies. Figure 2 explains the nasolabial soft tissue measurements and their landmarks, which were used in the included studies.

figure 2

Nose changes secondary to Le Fort I maxillary advancement

Nose changes

Two studies26,27 reported on the changes in the nasal tip projection. Maxillary advancement resulted in 0.89 mm (95% CI, -2.44-4.22, P = 0.60. I2 = 0) increase in nasal tip projection, which was statistically non-significant (Fig. 3a).

figure 3

Forest plot showing upper lip changes secondary to Le Fort I maxillary advancement. a) Upper lip projection. b) Upper lip philtrum width. c) Lower lip philtrum width

In terms of the changes in the nasal tip prominence, the pooled estimate of two of the included studies,27 showed that it decreased post-surgically by 0.77 mm (95% CI, -2.62-1.07, P = 0.41, I2 = 63%) and this was not statistically significant (Fig. 3b). On the other hand, the pooled outcomes of two of the included studies26,27 showed that osteotomy resulted in forward advancement of the subnasal region, which was statistically significant (mean difference [MD; 1.7 mm, 95% CI, 0.9-2.5, P = 0.0001, I2 = 0%] (Fig. 3c).

Lip changes

The pooled estimate of all included studies showed that maxillary advancement significantly increased upper lip projection (MD; 2.90 mm, 95% CI, 1.91-3.88, P <0.00001, I2 = 0%; 105 participants) (Fig. 4a). Additionally, the data of two of the included studies26,27 showed that Le Fort I advancement osteotomy significantly widens the upper lip philtrum (MD 0.84 mm, 95% CI, 0.10-1.58, P = 0.03, I2 = 0%; 67 participants) (Fig. 4b). However, the effect of surgery on lower lip philtrum width varied and it was statistically non-significant (MD; 3.06 mm, 95% CI, -0.67-6.55, P = 0.12, I2 = 96%) (Fig. 4c).

figure 4

Forest plot showing nose changes secondary to Le Fort I maxillary advancement. a) Nasal tip projection. b) Nasal tip prominence. c) Subnasal projection

Risk of bias across studies and additional analyses

The GRADE approach was used to assess the quality of the evidence for two outcomes. The quality of the evidence was very low due to the high risk of bias and the inherent limitations in the design of the included studies (Table 5). Sensitivity analysis, after excluding retrospective studies,26,27 showed a higher pooled estimate effect for the upper lip projection compared to the overall estimate effect (MD 3.89 mm, 95% CI, 1.81-5.96, P = 0.0002, I2 = 0) (Fig. 5). This indicates adequate robustness of this outcome based on the remaining two prospective studies.28,29 The number of the included studies was not sufficient to perform publication bias.

Table 5 Summary of findings clarifying the nasolabial change secondary to Le Fort I advancement and the certainty of the evidence
Full size table
figure 5

Sensitivity analysis of the upper lip projection outcome

Discussion

Single Le Fort I advancement surgery is likely to change the midfacial region, particularly the nasolabial region. Despite accurate hard tissue surgical planning, predicting the 3D nasolabial soft tissue changes can be difficult. The aim of this systematic review was to evaluate the current evidence regarding 3D nasolabial soft tissue changes that accompany Le Fort I maxillary advancement osteotomy in isolation from any other surgical procedures in class III malocclusion with maxillary retrognathia. This is of particular importance to orthodontists and maxillofacial surgeons.

Four studies met the inclusion criteria and their data were meta-analysed when possible. The mean maxillary advancement of the included studies was 5.58 mm. Meta-analysis demonstrated that advancing the maxilla has significant effects on the upper lip region, but mildly affected the nose region, while the effect on the lower lip region was negligible. Figure 2 represents a diagrammatic explanation of the soft tissue changes. Unsurprisingly, upper lip projection significantly increased post-surgically; hard tissue (maxilla) to soft tissue (HT:ST) changes in this region were approximately 2:1. Moreover, this review showed that the upper philtrum had mildly widened subsequent to maxillary advancement (HT:ST = 6:1). The changes in the upper lip projection and philtrum width could be due to the forward pressure of the dento-alveolar region on lip muscles secondary to maxillary advancement. These findings are similar to the findings of previous studies.30,31 Moreover, isolated Le Fort I osteotomy advancement significantly increased the subnasal projection (HT:ST = 3.2:1). These findings are close to the 2D outcomes of a previous qualitative systematic review.3On the other hand, change in the lower philtrum width of the upper lip varies widely and was statistically non-significant; this is probably because the anatomy of this region is mainly dependent on free muscle with a high degree of adaptability.

It is generally agreed that Le Fort I osteotomy advancement affects the nasal region and widens the alar base width.31,32,33 One possible explanation is that the surgery involves elevation of the periosteum, muscles and ligaments that stabilise the alar region with the anterior surface of the maxilla.30 However, our review showed that the effects of the surgery on flattening nasal prominence and nasal projection were mild and insignificant - HT:ST were 5.6:1 and 6.2:1, respectively. One of the possible explanations is the use of the nasal cinch suture and/or V-Y lip closure surgery in the included studies, which may have eased the effect of Le Fort I osteotomy advancement on nasal prominence and projection.3,26 Another explanation could be that the widening of the alar base as a result of maxillary advancement led the nasal tip to be restrained in the nasal complex.27,34 Furthermore, it is important to consider that the vertical changes and anticlockwise rotation of the occlusal plane as a consequence of jaw surgery may have a confounding influence on nasal prominence and projection.35 It is crucial to consider clinical heterogeneity as a causative factor for these findings. Although two included studies26,27 were performed at the same institution with an interval of two years, the authors reported different results regarding the 3D changes of the nose. This may be due to differences in the demographics of the patients. Metzler et al.27 recruited mainly young women (mean age was 16.7), while DeSesa et al.26 collected their data from older participants with an equal gender distribution. A recent retrospective study,36using 2D cephalometric measurements of patients who underwent maxillary advancement, reported a significant decrease in nasal prominence and a non-significant increase in nasal projection that agreed to some extent with the 3D findings of our meta-analysis.

It is important to note that the best fit reference-based registration method used for superimpositions and 3D measurement of data of the included studies in this review has not been considered as an accurate method of combining 3D images, and may have accounted for some error in measuring the changes.37 Anthropometric landmark identification is a further source of bias when not repeated by different researchers over separate time periods to identify errors, particularly in the peri-labial region.38

GRADE assessment showed that the evidence is of a very low certainty due to the high risk of bias and the inherent limitations in the design of the included studies. Therefore, the results should be interpreted with caution.

Strength and limitations

The registration of the a priori protocol, the non-restricted search, the strict inclusion criteria, and using validated risk of bias and GRADE approaches to assess the quality of the evidence are the strengths of the current systematic review. Moreover, confounding factors such as body mass index, facial expression during image capture, lip tonicity, fullness of soft tissue drape and presence of orthodontic appliances could influence soft tissue response;39 hence, this review included studies with a minimum of six months' follow-up to minimise the confounders.

Although four studies that portrayed a fair quality of evidence were included, these studies demonstrated differences in patients' gender and age. The authors also acknowledge that the methods of image acquisition used in the included studies of this review were heterogeneous. These indicate some degree of heterogeneity among the included studies.

Recommendations

The authors disclose that there are inconsistencies in terms of study settings, study sample populations, the adopted surgical procedures and amount of surgical movement, as well as ethnicity, gender and soft tissue characteristics.

With the current advancement in technology and the growing number of orthognathic planning software, these findings would be beneficial for surgical prediction. Hence, the review highlights a need for better primary research directed towards more accurate methods of 3D facial surface acquisition, accounting for the whole face in response to orthognathic surgical movements.

Conclusion

Low-level evidence concludes that the sagittal effect of isolated Le Fort I osteotomy on the nasolabial region is concentrated around the junction of the nose and upper lip, and the tip of the upper lip, but gradually diminishes in other regions. Post-surgical transverse nasolabial changes are negligible. Significant inconsistencies among the included studies were identified. Based on the quality of the available evidence presented in this study, long-term randomised controlled trials with standardised methods of 3D assessment are recommended to reach conclusive findings.