Three-dimensional evaluation of stability after bimaxillary orthognathic surgery for skeletal class III malocclusion in patients with cleft lip and palate

Abstract

Background

Using three-dimensional reconstruction technology, we evaluated postoperative jawbone stability in patients with cleft lip and palate and skeletal Class III malocclusion following bimaxillary surgery—maxillary advancement via LeFort I osteotomy and mandibular retraction via bilateral sagittal split osteotomy.

Methods

Twenty patients with cleft lip and palate who underwent bimaxillary surgery due to maxillary hypoplasia were selected for the study. Computed tomography (CT) images were collected at preoperative (T0), immediate postoperative (T1), and postoperative follow-up (T2) time points. The spatial distances (A-C, A-F, A-S, B-C, B-F, B-S) of points A (subspinale) and B (supramental) from the baseline coronal (C), horizontal (F), and sagittal (S) planes, as well as the spatial angles of the angles SNA, SNB, and ANB, were measured in the three periods after three-dimensional reconstruction utilizing Mimics21 software. Compare the changes in the three periods.

Results

1. All indicators from T0 to T1 showed statistically significant changes, P < 0.05.2. From T1 to T2, the average B-C increased by 2.25 mm, the average B-F decreased by 2.64 mm, the angle SNB increased by 1.25° on average, and the angle ANB decreased by 1.12° on average. All these changes were statistically significant (P < 0.05). However, the changes in the distance A-F, A-C, and the angle SNA were not statistically significant, P > 0.05.3. From T0 to T2, the average A-C increased by 3.16 mm, the average A-F increased by 1.81 mm, the average B-C decreased by 3.56 mm, the angle SNA increased by 2.77° on average, SNB decreased by 2.53° on average, and the angle ANB increased by 6.22° on average. All these changes were statistically significant (P < 0.05). The changes in A-S, B-F, and B-S were not statistically significant (P > 0.05).

Conclusion

Bimaxillary surgery is an effective method for correcting skeletal Class III malocclusion in patients with cleft lip and palate. The planned surgical movement of the mandible via bilateral sagittal split osteotomy (BSSO) with setback allows for compensatory reduction in the required maxillary advancement during LeFort I osteotomy. This approach may potentially reduce the extent of anteroposterior relapse in the maxilla.

Background

Cleft lip and palate (CLP) is among the most common congenital craniofacial anomalies. Midface depression frequently persists into adulthood after primary CLP repair, manifesting as maxillary hypoplasia characterized by sagittal and vertical deficiency, often accompanied by transverse maxillary arch narrowing [1]. A substantial proportion of these maxillary hypoplasia cases require surgical correction. Orthognathic surgery effectively addresses this three-dimensional jaw deficiency in skeletally mature patients [2]. The likelihood of requiring surgical correction for maxillofacial deformities in CLP patients correlates positively with the severity of the original cleft [3]. The primary surgical treatment for maxillary hypoplasia is LeFort I osteotomy with advancement. Tache and Mommaerts reported in their systematic review that approximately 20% of post-surgical CLP patients require maxillary advancement via LeFort I osteotomy [4]. However, LeFort I osteotomy in CLP patients is associated with a considerable relapse potential, with reported anteroposterior relapse rates reaching up to 40% [5]. Previous research has predominantly focused on conventional LeFort I advancement osteotomy in CLP patients [1, 2, 4–21], with most studies utilizing two-dimensional cephalometric analysis based on lateral radiographs for assessment. Studies examining bimaxillary surgery in this population remain relatively scarce [22]. Furthermore, comprehensive three-dimensional analyses of postoperative skeletal stability and relapse patterns are exceptionally limited. Therefore, this study aims to evaluate the stability of jawbone position during the follow-up period after bimaxillary surgery in CLP patients using CT-based three-dimensional reconstruction. This analysis seeks to provide deeper insights into potential three-dimensional jawbone movement patterns post-surgery, enabling more precise prediction of long-term outcomes and informing treatment strategies for this patient group.

Materials and methods

Ethical approval

This study was conducted following the Declaration of Helsinki and approved by the Ethics Committee of the Stomatology Hospital of Xi'an Jiaotong University (Approval No: 2025-XJKQIEC-KY-QT-0026–003). All procedures complied with applicable regulations and guidelines under the oversight of the Clinical Research Center of Shaanxi Province for Dental and Maxillofacial Diseases, College of Stomatology, Xi'an Jiaotong University. Informed consent was obtained from all participants and/or their legal guardians for the use of medical data and images in this research project.

Research object

Study subjects were recruited from patients with cleft lip and palate who underwent LeFort I osteotomy and maxillary advancement at Xi'an Jiaotong University School of Stomatology Hospital between January 2017 and January 2024 for the correction of maxillary hypoplasia. All included subjects concurrently underwent bilateral sagittal split ramus osteotomy (BSSO) of the mandible on the same day as part of their surgical treatment. Eligible participants were required to possess clear and complete preoperative (T0), immediate postoperative (at discharge, T1), and at least 8-month postoperative (T2) maxillofacial CT images. Study participants were selected from consecutive cases. Initial screening identified all cleft lip and palate patients who underwent orthognathic surgery during the study period (N = 45). After applying exclusion criteria, 20 cases were ultimately included for analysis. Primary exclusion reasons were incomplete or unclear imaging data (n = 7), single-jaw surgery only (n = 10), and bilateral cleft lip and palate (n = 8).

Data collection

The following data were collected for all included subjects:

1. Gender and age;

2. Anatomic location of the cleft;

3. Timing of image acquisition (corresponding to T0, T1, and T2 timepoints);

4. DICOM datasets of craniofacial CT scans obtained at all three timepoints.

Surgical procedure and postoperative protocol

All study subjects underwent preoperative orthodontic decompensation. All orthognathic procedures were performed by the same lead surgeon. Following dental decompensation, digital surgical planning was conducted using Dolphin software (version 11.8; Dolphin Imaging and Management Solutions, Chatsworth, CA, USA) to generate 3D-printed surgical splints. Intraoperatively, LeFort I osteotomy was performed. The posterior maxillary segment was separated at the pterygomaxillary junction using an osteotome. After downfracture, the maxilla was fully mobilized with maxillary disimpaction forceps until the preoperatively designed intermediate digital splint seated passively. The descending palatine arteries were preserved bilaterally in all cases. The repositioned maxilla was fixed with four-hole L-shaped titanium miniplates bilaterally at the piriform rim and zygomaticomaxillary buttress. Following stable maxillary fixation, bilateral sagittal split ramus osteotomy (BSSO) was performed. The mandible was mobilized until the preoperative final digital splint seated passively. After removing the designated bone segment, fixation was achieved with straight four-hole titanium miniplates. When the excised mandibular segment demonstrated sufficient volume, it was contoured and grafted to augment the piriform aperture region bilaterally, secured with titanium screws to address maxillary hypoplasia. No additional bone grafting from other sites was performed. Genioplasty via horizontal osteotomy was performed concurrently if indicated. Postoperatively, maxillomandibular fixation using the prefabricated final digital splint was maintained with elastics for 2–4 weeks, initiated 3–4 days after surgery. Throughout the study period, all surgical procedures were strictly performed in accordance with standardized technical protocols and a unified operational workflow. Although minor upgrades were made to auxiliary instruments, the core surgical steps remained consistently unchanged.

Methods for obtaining imaging data

Craniofacial CT scans were acquired using a United-Imaging uCT780 scanner (120 kV, 180 mA; Shanghai United-Imaging Healthcare Co., Ltd., Shanghai, China) and reconstructed in the axial plane with 0.5 mm slice thickness using a bone reconstruction algorithm.

Selection and definition of landmark points

The following cephalometric landmarks were utilized in this study:

• Sella (S): Midpoint of the sella turcica

• Nasion (N): Most anterior point of the frontonasal suture

• Subspinale (A): Deepest midline point on the maxillary alveolar process

• Supramentale (B): Deepest midline point on the mandibular alveolar process

• Porion (P):

  • o
    Left Porion (PL): Superior-most point of the left external auditory meatus
  • o
    Right Porion (PR): Superior-most point of the right external auditory meatus

• Orbitale (O): Inferior-most point of the orbital margin (Note: Only right Orbitale was used per study protocol)

Reference planes definition

1. Frankfort Horizontal Plane (F-plane): The anatomical reference plane defined by the bilateral porion landmarks (superior margin of the external acoustic meatus: PL and PR) and the right orbitale (O), constituting the PL-O-PR plane.

2. Coronal Reference Plane (C-plane): The vertical plane perpendicular to the F-plane passing through the bilateral porion landmarks (PL and PR).

3. Midsagittal Reference Plane (S-plane): The plane perpendicular to both F-plane and C-plane, intersecting the nasion (N).

Measurement methods and parameters

In the Measure and Analyze Template option of the Mimics 21 software (version 21.0.0.406, Materialise NV Technologielaan 15, 3001 Leuven, Belgium), create a measurement template. This template includes points S, N, A, and B. It also contains faces F, C, and S. It includes angles SNA, SNB, and ANB. It also includes distances A-F, A-C, A-S, B-F, B-C, and B-S (the vertical distances from points A and B to face F, C, and S, respectively). Import the DICOM data of the research subjects' CT into the Mimics 21.0 software, select the "Bone Scale" option for gray-scale value, and perform three-dimensional bone reconstruction. On the reconstructed jawbone, mark the points in the built template separately and precisely confirm the position of the marked points in the two-dimensional window. The software will automatically measure the defined angles and distances (as shown in Fig. 1). Since the software cannot automatically mark the spatial direction of the landmark points relative to the reference plane, and the spatial direction of the angles. Therefore, the points on the S plane on the left side are defined as positive values, and those on the right side are defined as negative values. After manual checking of the distances from the landmark points to the S plane and the ANB angle in the software, the positive or negative values of the numerical data are manually marked. The measurement data are measured by two physicians once every two months, and the average value is taken as the result.

Fig. 1.

Three-dimensional bone reconstruction and measurement. a) T0 SP Sagittal plane, FP Horizontal plane, CP Coronal plane (b) T1, (c) T2

Statistical analysis

All statistical analyses were performed using IBM SPSS Statistics software, version 21. A paired t-test was used to conduct a comparative analysis of various indicators at different periods, with the significance level set at 0.05. The agreement level between observations was assessed by the intraclass correlation coefficient (ICC).

Results

The ICC of the measurements was greater than 0.9, showing the high reliability of the measurements.

A total of 20 patients (14 males, 6 females) with cleft lip and palate were included. The cohort comprised 6 cases of unilateral cleft lip and alveolus (UCLA) and 14 cases of unilateral cleft lip, palate, and alveolus (UCLPA). The mean age was 20.35 ± 3.05 years (range: 16–28 years), with a mean follow-up period of 14.75 ± 4.35 months (range: 8–24 months).

Table 1 indicates that from T0 to T1 period, the mean increase in A-C was 3.45 mm, A-F increased by an average of 1.65 mm, A-S increased by a mean of 0.8 mm, and the ANB angle increased by an average of 7.35°. Meanwhile, B-C decreased by a mean of 5.82 mm, B-F increased by an average of 2.68 mm, B-S increased by a mean of 1.52 mm, the SNA angle increased by an average of 2.89°, and the SNB angle decreased by a mean of 3.78°. All measurements demonstrated statistically significant changes (P < 0.05).

Table 1.

Changes in cephalometric landmarks and angular measurements across different periods

	T0	T1	T2	T0-T1		T1-T2		T0-T2
	Mean ± SD			Mean ± SD	p	Mean ± SD	p	Mean ± SD	p
A-C(mm)	82.68 ± 3.7	86.13 ± 3.6	85.84 ± 3.71	−3.45 ± 2.64	0.000	0.29 ± 1.43	0.375	−3.16 ± 2.92	0.000
A-F(mm)	30.42 ± 2.66	32.07 ± 3.5	32.23 ± 3.62	−1.65 ± 2.32	0.005	−0.16 ± 2.32	0.759	−1.81 ± 2.79	0.009
A-S (mm)	0.21 ± 2.21	1.01 ± 1.98	0.39 ± 1.84	−0.8 ± 1.66	0.043	0.63 ± 0.88	0.005	−0.18 ± 1.57	0.623
ANB°	−3.6 ± 2.35	3.75 ± 1.93	2.63 ± 1.44	−7.35 ± 1.74	0.000	1.12 ± 1.91	0.017	−6.22 ± 2.58	0.000
B-C(mm)	84.23 ± 5.77	78.42 ± 4.14	80.67 ± 3.17	5.82 ± 3.37	0.000	−2.25 ± 2.44	0.001	3.56 ± 3.81	0.001
B-F(mm)	68.34 ± 4.79	71.02 ± 5.17	68.38 ± 5.02	−2.68 ± 3.17	0.001	2.64 ± 1.9	0.000	−0.04 ± 2.58	0.942
B-S (mm)	−1.22 ± 4.39	0.31 ± 2.88	−0.54 ± 2.24	−1.52 ± 3.07	0.039	0.85 ± 1.14	0.003	−0.67 ± 2.79	0.294
SNA°	74.55 ± 4.07	77.44 ± 5.36	77.33 ± 5.78	−2.89 ± 1.95	0.000	0.12 ± 1.32	0.693	−2.77 ± 2.3	0.000
SNB°	77.78 ± 3.33	74.01 ± 4.18	75.26 ± 4.61	3.78 ± 2.1	0.000	−1.25 ± 1.45	0.001	2.53 ± 2.3	0.000

From the T1 to T2 period, the mean decrease in A-S was 0.63 mm, B-C increased by a mean of 2.25 mm, B-F decreased by an average of 2.64 mm, B-S decreased by a mean of 0.85 mm, the SNB angle increased by an average of 1.25°, and the ANB angle decreased by a mean of 1.12°. These changes were all statistically significant (P < 0.05). Meanwhile, the changes in distances A-F and A-C, as well as the SNA angle, demonstrated no statistically significant differences (P > 0.05).

From the T0 to T2 period, the mean increase in A-C was 3.16 mm, A-F increased by a mean of 1.81 mm, B-C decreased by a mean of 3.56 mm, the SNA angle increased by a mean of 2.77°, the SNB angle decreased by a mean of 2.53°, and the ANB angle increased by a mean of 6.22°. These changes were all statistically significant (P < 0.05). However, the changes in distances A-S, B-F, and B-S demonstrated no statistically significant differences (P > 0.05).

Table 2 presents the mean magnitude of relapse, the direction of change, and statistical significance for all parameters evaluated across the entire study cohort between time points T1 and T2.

Table 2.

Relapse magnitude, direction, and statistical significance of measured parameters in the overall cohort between T1 and T2

Variable	(T1-T2) Mean ± SD	p	Significance	Direction
SNA°	0.12 ± 1.32	0.693	n.s	⚪
SNB°	−1.25 ± 1.45	0.001	**	+
ANB°	1.12 ± 1.91	0.017	*	一
A-C (mm)	0.29 ± 1.43	0.375	n.s	⚪
A-S (mm)	0.63 ± 0.88	0.005	**	→
A-F (mm)	−0.16 ± 2.32	0.759	n.s	⚪
B-C (mm)	−2.25 ± 2.44	0.001	**	»
B-F (mm)	2.64 ± 1.90	0.000	***	↑
B-S (mm)	0.85 ± 1.14	0.003	**	→

Significance designations: ***p < 0.001, **p < 0.01, *p < 0.05, n.s. indicates non-significance (p ≥ 0.05)

Symbol meanings: + (increase), – (decrease), ⚪ (no significant change), ↑ (upward), → (rightward), » (forward)

The cohort was divided into two subgroups based on a 12-month follow-up threshold: a short-term group (≤ 12 months; 8–12 months, n = 12) and a long-term group (> 12 months; 12–24 months, n = 8). Comparative analysis of parameter changes between T1 and T2 showed that neither subgroup exhibited statistically significant changes in A–C, A–F, or SNA measurements, whereas significant changes were observed in B–C, B–F, and SNB—consistent with trends observed in the overall cohort. Notably, the ≤ 12-month group showed significant change in the ANB angle (consistent with the overall trend), but no significant changes in the linear measurements A–S or B–S (diverging from the overall trend). In contrast, the > 12-month group exhibited no significant change in ANB (diverging from the overall trend), while demonstrating significant changes in A–S and B–S (consistent with the overall trend). Complete results are provided in Table 3.

Table 3.

Changes of parameters from T1 to T2 in the ≤ 12-month and > 12-month follow-up subgroups

	T1-T2
	≤ 12 m(N = 12)		> 12 m(N = 8)
	Mean ± SD	P	Mean ± SD	P
A-C(mm)	0.21 ± 1.02	0.493	0.42 ± 1.98	0.571
A-F(mm)	0.21 ± 1.42	0.619	−0.72 ± 3.28	0.556
A-S (mm)	0.55 ± 0.93	0.064	0.74 ± 0.85	0.043
ANB°	1 ± 1.22	0.016	1.3 ± 2.74	0.221
B-C(mm)	−1.85 ± 2.29	0.017	−2.86 ± 2.7	0.020
B-F(mm)	3.4 ± 1.82	0.000	1.49 ± 1.43	0.021
B-S (mm)	0.77 ± 1.45	0.093	0.97 ± 0.41	0.000
SNA°	0.04 ± 1.21	0.907	0.23 ± 1.56	0.684
SNB°	−1.16 ± 0.84	0.001	−1.39 ± 2.13	0.048

Subgroup analysis was performed by categorizing the enrolled subjects into two cohorts according to palatal cleft type: unilateral incomplete cleft palate (UICP) and unilateral complete cleft palate (UCCP). Comparative assessment of parameter changes from T1 to T2 indicated that neither subgroup exhibited statistically significant changes in A–C, A–F, ANB, or SNA measurements, whereas significant changes were observed in B–C, B–F, and SNB—consistent with the trends identified in the overall cohort. Specifically, the incomplete cleft group displayed statistically significant changes in B–S (consistent with overall trends), but not in A–S (diverging from overall trends). In contrast, the complete cleft group showed significant changes in A–S (aligning with overall trends), while no significant change was observed in B–S (diverging from overall trends). Comprehensive results are provided in Table 4.

Table 4.

Changes in parameters from T1 to T2 by cleft type subgroups

	T1-T2
	UICCP (N = 9)		UCCP (N = 11)
	Mean ± SD	P	Mean ± SD	P
A-C(mm)	0.13 ± 1.47	0.791	0.42 ± 1.46	0.362
A-F(mm)	−0.12 ± 2.52	0.889	−0.19 ± 2.26	0.783
A-S (mm)	0.63 ± 0.96	0.086	0.62 ± 0.85	0.035
ANB°	0.99 ± 2.01	0.175	1.23 ± 1.93	0.060
B-C(mm)	−2.72 ± 2.47	0.011	−1.88 ± 2.47	0.031
B-F(mm)	2.72 ± 2.08	0.004	2.57 ± 1.83	0.001
B-S (mm)	0.97 ± 1.18	0.039	0.75 ± 1.15	0.055
SNA°	0.17 ± 1.51	0.744	0.08 ± 1.22	0.840
SNB°	−1.43 ± 1.48	0.020	−1.11 ± 1.47	0.032

Discussion

Severe jawbone deformities require orthognathic surgery for treatment. The purpose of orthognathic surgery is to restore a good facial shape and occlusion function. Due to the inherent defects of development and the scars caused by surgical intervention, patients with adult skeletal Class III malocclusion due to cleft lip and palate are more likely to have severe insufficient development of the maxilla compared to non-cleft patients [23, 24]. Approximately 25% to 35% of CLP patients develop maxillary hypoplasia severe enough to necessitate surgical intervention [22]. The most common surgical approach is maxillary osteotomy [5]. LeFort I osteotomy with advancement is the most frequently employed surgical method for treating maxillary hypoplasia [12]. However, postoperative relapse can occur due to factors such as soft tissue tension, scarring, muscle strain, and instability of the osteotomized segment [9]. Studies suggest that the relapse rate following LeFort I advancement osteotomy is approximately 20% in non-cleft patients [17]. CLP patients are more susceptible to relapse after orthognathic surgery. Relapse represents a significant challenge following orthognathic surgery, as it adversely affects the surgical outcome. Therefore, investigating the causes of relapse in CLP orthognathic patients, the magnitude of relapse, and strategies to minimize relapse are all of significant importance.

Current research suggests that factors potentially contributing to the increased susceptibility to relapse after maxillary advancement surgery in cleft lip and palate (CLP) patients may include: soft tissue scarring, compromised bone strength resulting from alveolar ridge and palatal bone defects, and reduced stability due to missing teeth [1]. Among these, soft tissue scarring exhibits significant individual variation, influenced by prior surgical interventions and patient-specific factors. Consequently, quantifying the impact of soft tissue scarring on orthognathic surgical outcomes is challenging. Similarly, defects in the palatal bone and alveolar ridge are highly patient-specific and difficult to measure precisely. Although some studies have found no significant correlation between the intraoperative advancement magnitude during LeFort I osteotomy and postoperative relapse [15], recent research frequently suggests a significant correlation exists [19]. Therefore, this study focuses on exploring the precisely quantifiable parameter of three-dimensional skeletal movement magnitude.

The results of this study indicate that all measured parameters—including linear distances (A-C, A-F, A-S, B-F, B-C, B-S) and angular measurements (SNA, SNB, ANB)—underwent statistically significant changes from the T0 to T1 stage. This confirms effective surgical repositioning of the maxillomandibular complex. Point A demonstrated an average displacement of 3.45 mm anteriorly, 1.65 mm inferiorly, and 0.80 mm to the left. Conversely, Point B exhibited an average displacement of 5.82 mm posteriorly, 2.68 mm inferiorly, and 1.52 mm to the left. Angular measurements revealed an average increase of 2.89° in SNA, a decrease of 3.78° in SNB, and an increase of 7.35° in ANB. These changes demonstrate successful maxillary advancement and mandibular setback, accompanied by inferior displacement of both jaws, which effectively increased lower facial vertical height. Notably, the mean ANB angle shifted from −3.6° preoperatively to 2.63° postoperatively, achieving immediate correction of the preoperative negative overjet.

Significant relapse occurred between T1 and T2. Point A relapsed an average of 0.63 mm laterally rightward. Point B relapsed anteriorly (2.25 mm), superiorly (2.64 mm), and rightward (0.85 mm). Concurrently, angle SNB increased by 1.25° and angle ANB decreased by 1.12° (all P < 0.05), indicating relapse of the maxillomandibular relationship. This demonstrates horizontal maxillary relapse and three-dimensional mandibular relapse. Stability was observed anteroposteriorly and vertically for Point A (no significant change in A-F, A-C, SNA; P > 0.05) and in distances A-S, B-F, B-S. This pattern confirms susceptibility to horizontal relapse in the maxilla and susceptibility to relapse in all dimensions in the mandible during the follow-up period.

From the T0 to T2 stage, Point A demonstrated a mean anterior displacement of 3.16 mm and inferior displacement of 1.81 mm, while Point B exhibited a mean posterior displacement of 3.56 mm. Angular measurements revealed a statistically significant increase in SNA of 2.77°, a decrease in SNB of 2.53°, and an increase in ANB of 6.22° (all P < 0.05). Notably, the ANB angle shifted from −3.6° preoperatively to 2.63° postoperatively. These sustained, statistically significant changes demonstrate that bimaxillary orthognathic surgery effectively corrects skeletal Class III malocclusion in cleft lip and palate patients over the medium-to-long term.

The SNA angle reflects the position of the maxilla relative to the anterior cranial base, with a normative range of 82° ± 2°. The SNB angle indicates the position of the mandible relative to the anterior cranial base, with a normative range of 80° ± 2°. The ANB angle represents the sagittal relationship between the maxilla and mandible, having a normative range of 2° to 4° [25]. In this study, the mean preoperative SNA angle was 74.55°, increasing to 77.33° at follow-up. The mean preoperative SNB angle was 77.78°, decreasing to 75.26° postoperatively. Although both follow-up SNA and SNB angles remained below normative ranges, the mean ANB angle was corrected from a preoperative value of −3.6° to 2.63° at follow-up, achieving a normal sagittal relationship. This outcome aligns with our treatment strategy: employing a compensatory bimaxillary approach involving judiciously moderated maxillary advancement combined with mandibular setback. This strategy achieved an ideal maxillomandibular correction with relatively modest absolute skeletal movements, effectively addressing skeletal Class III malocclusion in cleft lip and palate patients. All included patients expressed satisfaction with their postoperative facial aesthetics.

While existing studies indicate higher relapse rates following inferior displacement (downward movement) compared to superior repositioning of the maxilla in the vertical dimension [9, 26], the present findings demonstrate contrasting outcomes. In this study, surgical inferior displacement of Point A averaged 1.65 mm, yet no statistically significant vertical relapse was observed during the follow-up period (P > 0.05). Similarly, the mean distance of Point A from the coronal plane decreased minimally from 86.13 mm immediately postoperatively to 85.84 mm at follow-up; this change was not statistically significant, confirming good vertical stability. Potential contributing factors to this stability may include: (1) the compensatory bimaxillary approach allowing relatively moderated maxillary advancement, thereby reducing soft tissue tension; and (2) thorough mobilization of the maxillary and mandibular osteotomized segments, minimizing restrictive forces [23, 27].

Research on postoperative mandibular relapse in cleft lip and palate (CLP) patients undergoing orthognathic surgery remains limited. Yoon-Hee Park et al. posit a positive correlation between the magnitude of mandibular setback and subsequent relapse in bimaxillary cases [24]. In the present study, bilateral sagittal split ramus osteotomy (BSSO) achieved a mean mandibular setback of 5.82 mm. During follow-up, Point B exhibited statistically significant three-dimensional relapse, most pronounced sagittally (anterior relapse: 2.25 mm) and vertically (superior relapse: 2.64 mm). This pattern suggests reverse-rotational movement of the mandible during the postoperative period. The observed relapse may be attributed to the mandible’s biomechanical behavior as a hinged articulation subject to functional loading. Mastication forces—particularly the upward and anterior vector exerted by the temporalis and masseter muscles on the proximal segment—create a propensity for anterior–superior displacement of the proximal segment [28]. Given the rigid fixation provided by titanium plates, this movement may be transmitted to the distal segment at Point B, manifesting as coordinated anterior–superior relapse. Concurrently, vertical maxillary relapse may further potentiate mandibular superior displacement. Despite statistically significant relapse at Point B, the mean ANB angle—representing the maxillomandibular relationship—remained stable at 2.63° during follow-up, well within the normative range (2°–4°). Based on these findings, we hypothesize that incorporating planned mandibular overcorrection into orthognathic surgery for cleft lip and palate patients may yield improved long-term stability. This assumption, however, requires further validation through targeted subsequent studies.

To evaluate the influence of follow-up duration on postoperative relapse. The study subjects were stratified into two groups using a 12-month follow-up threshold. The results revealed that changes in the ANB angle were statistically significant in the group with follow-up ≤ 12 months, whereas no significant relapse was observed in the group followed for more than 12 months. This may be attributed to the fact that, over time, postoperative orthodontic treatment was largely or fully completed. Orthodontic traction likely contributed to a more stable and ideal anteroposterior relationship between the maxilla and mandible compared to earlier stages. In contrast, changes in A–S and B–S values were not statistically significant in the group with ≤ 12 months of follow-up, but became significant in the group followed beyond 12 months. This suggests that transverse relapse may become more pronounced over time.

To investigate the influence of cleft type on postoperative relapse. Subjects were categorized into two groups according to the type of cleft palate. The results demonstrated a statistically significant change in the A–S value in the complete cleft palate group, whereas this change did not reach statistical significance in the incomplete cleft group. This suggests that the relapse tendency of point A in the transverse dimension may be more pronounced in patients with complete clefts. Conversely, a statistically significant change in the B–S value was observed in the incomplete cleft group, but not in the complete cleft group. This discrepancy may be attributed to the fact that the relationship between mandibular stability and the type of cleft palate remains unclear. The stability of the mandible is likely influenced by a combination of factors, including masticatory muscle forces, condylar morphology and position, condylar stability, postoperative orthodontic management, and the patient’s mandibular functional patterns. Moreover, given the relatively small magnitude of postoperative changes in these measurements and the limited sample size, the clinical relevance of these findings should be interpreted with caution. Further studies with larger sample sizes are warranted to validate and elucidate these observations.

Some scholars contend that the maxillary relapse rate does not differ significantly between single-jaw (maxillary-only) and bimaxillary orthognathic surgeries [9, 12, 19]. Others posit that bimaxillary surgery entails a higher relapse rate [20]. However, our team maintains that maxillary hypoplasia secondary to cleft lip and palate (CLP) is often severe. Consequently, the magnitude of advancement required in isolated maxillary LeFort I osteotomy is typically substantial. Nevertheless, due to the restrictive effects of scar tissue from the cleft repair, achieving the necessary advancement during single-jaw surgery is frequently challenging. Based on our clinical experience, excessive maxillary advancement in CLP patients often requires prolonged operative time and may incur greater surgical trauma. Furthermore, midfacial deficiency in these patients commonly extends beyond the LeFort I osteotomy line. Thus, significant maxillary advancement alone may create a pronounced discrepancy in position across the osteotomy site, potentially compromising overall midfacial harmony. Additionally, compromised blood supply in scarred regions of the maxilla may lead to impaired healing following excessive mobilization. Moreover, substantial maxillary advancement risks inducing or exacerbating postoperative velopharyngeal insufficiency (VPI) [27]. For these reasons, our team routinely performs bilateral sagittal split ramus osteotomy (BSSO) of the mandible concurrently when addressing maxillary hypoplasia in CLP patients. This approach allows compensatory reduction of the required maxillary advancement [24], resulting in a more harmonious postoperative profile while mitigating potential VPI risks. Studies demonstrate that bimaxillary surgery in CLP patients not only improves skeletal relationships but also significantly enhances soft tissue contours, yielding substantial improvements in facial aesthetics. Consequently, most CLP patients undergoing bimaxillary surgery avoid the need for additional cosmetic procedures [22]. By employing this bimaxillary strategy, the mean maxillary advancement in our study cohort was limited to 3.45 mm. This minimal advancement effectively corrected skeletal Class III malocclusion in CLP patients. Moreover, no statistically significant relapse was observed among the study participants.

Mitigating relapse represents a critical consideration. Bibiana Dalsasso Velasques et al. posit that relapse following maxillary advancement via LeFort I osteotomy in cleft lip and palate (CLP) patients is predictable [20]. Valls-Ontañón et al. suggest that for every 1 mm of maxillary advancement, an anticipated relapse of 0.23 mm may occur [2]. D. Séblain et al. reported the application of a minimally invasive approach for LeFort I osteotomy in CLP patients, proposing that this technique results in reduced relapse and fewer complications compared to conventional approaches [18]. While the precise degree of intraoperative maxillary mobilization cannot be quantified for each individual patient, our clinical experience indicates that the adequacy of intraoperative bony release constitutes a key factor influencing postoperative relapse. Buddhathida Wangsrimongkol et al. recommend implementing moderate overcorrection for all CLP patients undergoing LeFort I advancement osteotomy to compensate for the expected postoperative relapse [21]. This study similarly observed that, although not all measured parameters demonstrated statistically significant relapse at follow-up, the mean values for all parameters exhibited a tendency to shift in the direction opposite to the surgical movement. Therefore, moderate overcorrection may represent a potential strategy to reduce postoperative relapse.

Several studies have reported the use of interpositional bone grafting at the osteotomy gap to mitigate postoperative relapse; however, numerous investigations indicate that relapse rates following bone grafting remain above 20% [27]. Moreover, bone grafting additionally prolongs operative time and introduces donor site morbidity with potential complications. Consequently, our team seldom employs supplemental bone grafting during orthognathic surgery for cleft lip and palate (CLP) patients. Hun Jang et al. suggest that favorable stability can be achieved without bone grafting in bimaxillary surgery when maxillary advancement is less than 6 mm [27]. Given our adoption of the bimaxillary approach, the mean maxillary advancement in the present study cohort was limited to 3.45 mm; therefore, interpositional bone grafting was omitted in all cases.

The shape and position of the condyle are closely related to the stability of the mandible after orthognathic surgery [29]. If the position of the condyle is improperly determined during orthognathic surgery, it may lead to various complications such as joint clicking, condylar resorption, etc. [30]. Multiple factors during orthognathic surgery may cause changes in the position of the condyle, such as the use of muscle relaxants, the position of the head during the operation, joint edema, incorrect fixation methods during the operation, etc. Changes in the position of the condyle after orthognathic surgery may lead to a decrease in the matching degree between the condyle and the joint fossa. The differences in the force exerted on the condyle by the surrounding muscles of the mandible after the operation may also affect the stability of the mandible after orthognathic surgery. Previous literature suggests that the position of the condyle after orthognathic surgery tends to move in a specific direction, lasting for up to 6 months, and then stabilizes [29]. The height of the mandibular ramus on the fissure side and the total height of the mandibular ramus plus the condyle in unilateral cleft patients are significantly lower than those on the non-fissure side [31]. The asymmetry of the condylar shape in unilateral cleft patients becomes more severe with age, but its position tends to normalize [32].

Due to differences in the shape and position of the condylar process between patients with and without cleft lip and palate (CLP), those with CLP may exhibit poorer stability of the jawbone following orthognathic surgery. This increased instability raises the risk of postoperative recurrence. Therefore, routine evaluation of the condylar process—including clinical assessment as well as computed tomography (CT) or cone-beam computed tomography (CBCT)—should be incorporated into surgical planning. For selected patients, magnetic resonance imaging (MRI) of the temporomandibular joint may be further indicated to comprehensively assess the morphological and positional characteristics of the condylar process. Such imaging allows the potential influence of condylar anatomy on postoperative relapse to be considered during the preoperative planning process.

Accurate intraoperative positioning of the condylar process is a critical aspect of orthognathic surgery. Both precise placement during operation and postsurgical stability of the condyle are regarded as essential for achieving stable occlusion, maintaining jaw position, and preventing the recurrence of dentofacial deformities and temporomandibular joint disorders. However, achieving optimal positioning remains challenging. In current practice, condylar positioning largely depends on the surgeon’s experience, involving dynamic intraoperative assessment of joint pressure and alignment to place the condyle in its natural position. When available, digital three-dimensional surgical simulation can be employed during preoperative planning to accurately simulate condylar placement. Additionally, surgical navigation or a digital condylar positioning guide may be utilized to enhance intraoperative precision.

There is considerable individual variation in soft tissue scarring among patients with cleft lip and palate, influenced by factors such as the initial surgical technique, scar severity, and scar location. Currently, there is no reliable method to precisely quantify the direction and magnitude of forces exerted by these scars. The primary approach for investigating soft tissue scarring in cleft lip and palate patients is the three-dimensional finite element method. Some researchers have employed this technique to simulate and compare the effects of anterior versus posterior palatal scarring on maxillary growth. Their findings indicate that scar tissue in different regions of the hard palate following palatoplasty may three-dimensionally constrain maxillary development. Among these, anterior scarring appears to exert a more pronounced inhibitory effect on maxillary growth [33]. Scarring on the palate and lip following surgical repair in patients with cleft lip and palate may represent a significant factor contributing to relapse after orthognathic surgery. These scars can restrict maxillary movement and exert continuous tensile forces on the maxilla, thereby potentially leading to postoperative recurrence [5]. Postoperative recurrence may also be attributed to scar tissue formation in the pterygomaxillary region [34]. Analysis of the overall study cohort indicates that point A has relapsed in the transverse direction, suggesting that postoperative soft tissue and scar contractions have exerted a horizontal pulling force on this landmark. The author proposes the following potential mechanisms for the recurrence: Movement of the maxilla results in corresponding displacement of the directly or partially attached soft tissues and scars. In certain regions, these soft tissues and scars may undergo deformation, primarily manifested as stretching or folding. During LeFort I osteotomy, when the pterygomaxillary junction is separated, the soft tissue of the hard palate remains attached to the palatal bone. Consequently, repositioning of the maxilla induces partial displacement or deformation of the soft tissues and scars in the labial, buccal, palatal, and pterygomaxillary regions.Scar tissue, which exhibits centripetal contractility, is compositionally distinct from normal mucoperiosteal tissue. It lacks elastic fibers and is predominantly composed of dense collagen bundles. Furthermore, Sharpey’s fibers anchor the scar tissue firmly to the hard palate, thereby altering its biomechanical properties and response to forces. [35]. Under identical conditions of displacement or deformation, scar tissue may generate a stronger contractile force compared to normal soft tissue, thereby exerting a retractive force that tends to pull the repositioned jawbone toward its original position following orthognathic surgery.

Since postoperative scarring in patients with cleft lip and palate occurs predominantly in the maxillary region, the author suggests that the vertical relapse of point B is primarily associated with the forces exerted by the masticatory muscles on the mandible following orthognathic surgery—a view consistent with previously reported findings in the literature, as detailed earlier in the text. Furthermore, the postoperative stability of the mandible is closely influenced by factors such as condylar morphology and position, postoperative orthodontic management, and the patient’s functional mandibular movements. For the overall cohort, the transverse relapse tendency of point B was found to align with that of point A. This correlation may be attributed to the fact that the final occlusal relationship—which serves as a predetermined reference—prioritizes harmony between the maxillary and mandibular midlines. Postoperative orthodontic treatment is subsequently performed based on this planned occlusion. Given that points A and B are typically situated near or on the midline, their horizontal relapse patterns are consequently similar. It is important to note that although statistically significant transverse relapse was observed for both points A and B in the overall sample, the actual magnitude of displacement was minimal. Moreover, subgroup analyses stratified by follow-up duration and cleft type revealed that the relapse patterns and statistical significance of horizontal changes were not entirely consistent across groups. Therefore, the clinical relevance of these findings should be interpreted cautiously. Such minor discrepancies may reflect variations in surgical technique or the influence of confounding factors rather than true biological relapse. Further studies with larger sample sizes are warranted to enhance the reliability and generalizability of these results.

Cleft lip and palate patients who undergo bimaxillary orthognathic surgery effectively have their pathological skeletal Class III relationship between the maxilla and mandible converted to a Class I relationship. This improves the appearance of the face in part by ameliorating serious defects in the middle face and promoting the development of soft tissue in the concave of the upper lip and the base of the nose. Combined with pre-and post-operative orthodontic treatment, patients achieve excellent occlusal function. As a result, chewing function and facial appearance improved, further improving the quality of life of patients. On the other hand, the propulsion of the maxilla also causes the soft palate attached to the maxilla to move forward to a certain extent. This forward movement of the soft palate may adversely affect velopharyngeal closure. Therefore, the closure of the cleft palate should be assessed in the development of treatment plans. Subjective and objective assessment of cleft pre-existing velopharyngeal insufficiency before and after surgery is particularly important in the patient population because velopharyngeal function is likely to be deficient.

The main strength of the study was a three-dimensional analysis of maxillomandibular movement. In addition, this study uniquely characterizes mandibular displacement patterns after bimaxillary surgery. There are several limitations worth acknowledging. Patients with cleft lip and palate have significant heterogeneity when receiving orthognathic procedures, including variability of timing of primary cleft lip and palate resection, preoperative burden, and characteristics of scar tissue characteristics in different sites. These individualized factors constitute potential confounding variables that may influence surgical outcomes. In this study, some landmarks represented the smallest mandible displacement (less than 1 mm). Although potentially statistically significant, its clinical value requires careful interpretation. This small change may be part of a variation in surgical techniques or may be influenced by confounding factors rather than representing a true biological recurrence. Soft tissue scarring and muscle function are known to contribute to relapse. The lack of any functional or soft tissue assessment limits the comprehensiveness of the analysis. The study did not include a control group. Therefore, although these findings apply to patients with cleft lip and palate undergoing bimaxillary surgery, it is unclear whether the observed pattern of recurrence and stability is specific to cleft lip pathology or comparable to the outcome of general orthognathic surgery. Subsequent studies require the addition of an appropriate control group for further investigation. The small sample size limits the certainty of the conclusions. Therefore, these results should be considered preliminary results that need to be validated in larger future studies.

Conclusions

In conclusion, bimaxillary surgery has been shown to be an effective intervention in the treatment of cleft lip and palate in patients with triple dislocation of the bone. Specifically, bimaxillary surgery is performed to reduce the extent of compensation required for anterior maxillary movement. This strategic approach has the potential to reduce the extent of maxillary relapse. However, the recurrence of the mandible was observed to be relatively prominent. Given this finding, incorporating appropriate mandibular overcorrection into treatment may be a viable solution that warrants further exploration and consideration in clinical practice.

Authors’ contributions

Ming Gao made contributions to paper writing, data gathering, measurement, and analysis, as well as research design. Zhanping Ren and Jinfeng Li assisted with the analysis and discussion of the results. Yongwei Tao and Sis Bi assisted in the collection of some patient data. Ren Zhanping and Ming Gao were the guarantors of the final approval and manuscript. All authors read and approved the final version of the manuscript.

Funding

None.

Data availability

To protect patient confidentiality, the datasets collected and analyzed for this study are not publicly accessible. However, they can be obtained from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

Guidelines: This study is being conducted on individuals in compliance with the applicable regulations and guidelines that have been approved by the Clinical Research Center of Shaanxi Province for Dental and Maxillofacial Diseases, College of Stomatology, Xi’an Jiaotong University.

Ethical approval: This study was approved by the Ethics Committee of the Stomatology Hospital of Xian Jiaotong University (No: 2025-XJKQIEC-KY-QT-0026–003). Written informed consent was obtained from all the patients. This study was conducted following the Declaration of Helsinki.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.