www.PRSGlobalOpen.com 1 INTRODUCTION The chin is a skeletal unit that is a fundamental part of the lower third of the face.1 Its different morpho- logical and positional alterations are mainly observed in combination, affecting facial harmony and balance, mainly in the context of dentofacial anomalies or cra- niofacial malformations. In this context, the corrective chin osteotomies (genioplasty) have shown great versa- tility and stability over time. Initially described in 1940 by Hofer as “anterior osteotomy of the mandible,” dif- ferent designs to correct specific alterations of the chin have been described, for example, sliding genioplasty, which allows the chin to be advanced, leaving it in a bal- anced anterior position.2 Cases that require a combined correction in the sagittal and vertical direction at the same time require more detailed planning. That is why, when vertical reduction and sagittal advancement are required, it is possible to design an osteotomy according to the description of Michelet et al.3 Another alternative for less severe cases is to perform a sliding osteotomy with an ascending inclined plane in a posterior-anterior direction, which allows the chin to be positioned in a more anterior and superior position.4 For those cases in which there is a vertical and sagittal deficit, the perfor- mance of a sliding osteotomy and the placement of a graft between the bone fragments and fixation of the distal segment in a more anterior and inferior position was usually proposed.5 However, in 2012, Fariña et al6 Cosmetic Original Article Background: This study aimed to evaluate changes of the M-shaped genioplasty in sagittal and vertical planes in a group of 34 patients and describe other indications, such as the increase of the mentolabial angle, decrease in the depth of the mento- labial fold, and the centering of the chin. Methods: A retrospective analysis was performed on 34 patients between 2010 and 2019. All studies were conducted at T0 (preoperative), T1 (a month after surgery), and T2 (1 year after surgery). The position of the bone pogonion (Pg) was mea- sured vertically and horizontally at T0, T1, and T2; the mentolabial angle and the depth of the mentolabial fold were measured at T0 and T2. Results: The average sagittal advancement at T1 was 6.6 mm and at T2 was 6.4 mm. The inferior movement was an average of 5.6 mm at T1 and T2, showing both movements excellent stability. The mentolabial angle increased at T2 an average of 28.2 degrees (5 degrees per each millimeter of inferior movement), whereas the depth of the mentolabial fold decreased an average of 2.8 mm (decreased 49% from the initial depth and decreased 0.56 mm per each mm of inferior move- ment). The average increase of the lower third of the face was 5 mm. No complica- tions were observed in any patient. Conclusions: M-shaped genioplasty is an anterior osteotomy of the mandible, which allows the chin to move forward and downward. Additionally, it allows an increase of the mentolabial angle and decreases the mentolabial fold. (Plast Reconstr Surg Glob Open 2023; 11:e4778; doi: 10.1097/GOX.0000000000004778; Published online 23 January 2023.) Rodrigo Fariña, DMD, Med*†‡ Salvador Valladares-Pérez, DMD, Med§¶ Carlos Navarro-Cuellar, DMD, MD║ Ramón Torrealba, DMD** Antonia Fariña-Silva†† Gabriel Fariña-Silva‡‡ From the *Service of Maxillofacial Surgery, Hospital del Salvador Santiago, Chile; †Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Universidad de Chile, Santiago, Chile; ‡Service of Maxillofacial Surgery, Hospital San Borja, Arriarán, Santiago, Chile; §Service of Maxillofacial Surgery, Hospital Clínico Metropolitano El Carmen; ¶Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile; ║Service of Maxillofacial Surgery, Hospital General Universitario Gregorio Marañón, Madrid, Spain; **Service of Maxillofacial Surgery, Hospital de Carabineros, Santiago, Chile; ††Department of Physics, University of Redlands, Calif.; and ‡‡Universidad Diego Portales, Santiago, Chile. Received for publication May 17, 2022; accepted November 21, 2022. Copyright © 2023 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of The American Society of Plastic Surgeons. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. DOI: 10.1097/GOX.0000000000004778 M-shaped Genioplasty: New Findings after 10 Years of Experience Disclosure: The authors have no financial interest to declare in relation to the content of this article. 23January2023 23 January 2023 11 1 https://doi.org/10.1097/GOX.0000000000004778 http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ http://creativecommons.org/licenses/by-nc-nd/4.0/ https://doi.org/10.1097/GOX.0000000000004778 PRS Global Open • 2023 2 proposed an M-shaped osteotomy design that allows advances and inferior movements of the chin with a simple design. This technique allows movements in the three planes of space, avoiding autologous graft, and reducing both complications and morbidity. Other benefits of this technique are improvement of the mentolabial fold and mentolabial angle when they are deep and acute, respec- tively, because with conventional sliding genioplasty, the mentolabial fold increases, and the mentolabial angle decreases. This study aims to evaluate the changes produced by M-shaped genioplasty and their impact on the aesthetic and functional results. MATERIALS AND METHODS A descriptive, retrospective analysis was performed on 34 patients who underwent M-shaped genioplasty isolated or in association with other osteotomies of the jaws [Lefort I osteotomy (L1) and/or bilateral sagittal split ramus osteotomy (BSSRO)] (Table  1). All those patients were operated on between March 2010 and December 2019, in the maxillofacial surgery service of the Hospital del Salvador and the private practice of Dr. Fariña. The decision of treatment with M-shaped genioplasty isolated or as part of the uni- or bimaxillary orthognathic surgery was made according to the particular needs of each case, always considering the particular indications of the technique for the mentonian unit. Through a vestibular approach, the design is drawn on the bone tissue or using a surgical guide, with the planned inclination of the osteotomy. The cut is made bicortically, with a reciprocating saw, with a caudoce- phalic inclination generating an inclined plane. The dis- tal segment slides toward a lower and anterior position, maintaining bone contact with the proximal segments. Once the chin is positioned, it is fixed with osteosynthesis plates and screws 2.0. Depending on the magnitude of the desired move- ment in the vertical and sagittal direction, it can use a trigonometric formula (tangent function−1) or determine the inclination of the plane by repeating the geometric angle from the visual treatment objective to the patient, either in conventional or virtual planning (Figs. 1 and 2). The indications of M-shaped genioplasty are: • Lower third of the face decreased (more than 10% of middle third of the face or lower height between lower stomion to menton, compared with distance from sub- nasale to upper stomion). • Laterogenia that requires centering descent with or without advance. • Vertical excess of the maxilla that requires maxillary ascent through L1 osteotomy, which would change the vertical facial proportions. • Depth of mentolabial fold greater than 6 mm (norm is 4 ± 2 mm).7 • Mentolabial angle less than 110  degrees (norm is 122 degrees ± 12 degrees) in patients with microgenia or retrogenia.8 • Euryprosopic (79–83.9) or hypereuriprosopic (<78.9) in facial index (Martin and Saller: facial length × 100/ facial width).9 An analysis of the cases was carried out, using visual treatment objectives, frontal and profile photographs, and cephalometry on a cone beam computed tomography (CBCT). The studies of bone pogonion were conducted at T0 (preoperative), T1 (a month after surgery), and T2 (1 year after surgery). The position of the bone pogonion was measured vertically and horizontally from a line per- pendicular to the occlusal plane passing through the inci- sal edge of the lower central incisor. This measurement was done to eliminate the effects of BSSRO on the verti- cal and sagittal movement (Fig. 3). The mentolabial angle and mentolabial fold were measured in T0 and T2 (1 year after surgery, to avoid the effects of postoperative edema on soft tissues). The mentolabial angle was measured on the photographs from two imaginary lines that intersect the sublabial point (a line between the lower labial point to the sublabial point and another line between the subla- bial point to the soft pogonion)8 (Fig. 4). The depth of the mentolabial fold was determined by measuring the CBCT, the distance in millimeters from the deepest point of the sulcus to a line designed between the inferior labial point to the soft pogonion (Pg´). The increase of the lower third of the face was measured from the incisal edge of the lower incisor to the soft Me’ chin point in the CBCT, perpendicular to the Frankfort plane. This way to mea- sure was done to eliminate the he effects of L1 and BSSRO on the vertical and sagittal movement. This study follows the Declaration of Helsinki on medical protocol and eth- ics and has been approved by the ethical review board of Hospital del Salvador. Takeaways Question: This publication shows a long-term follow-up of the M-shaped genioplasty technique, described by the authors in 2012. Findings: In addition to its initial indication of advance and descent of the chin with a single osteotomy, a positive impact on mentolabial angle and mentolabial fold was observed. Meaning: A single osteotomy allows the chin to be mobi- lized forward and downward, as well as improving the aes- thetic result of the angle and depth of the mentolabial fold. Table 1. Types of Surgery in the 34 Patients Type of Surgery No. Patients Gender (Male/ Female) L1+BSSRO+ M-shaped genioplasty 11 6/5 L1+ M-shaped genioplasty 6 3/3 BSSRO + M-shaped genioplasty 10 4/6 Isolated M-shaped genioplasty 7 3/4 Total 34 16/18 Fariña et al • M-shaped Genioplasty 3 RESULTS Thirty-four patients were operated on with M-shaped genioplasty, 11 patients with L1 osteotomy and BSSRO (Figs. 4–7), six patients with L1 osteotomy, 10 patients with BSSRO (Figs. 8 and 9), and seven patients with only M genio- plasty (Fig. 10). The distribution by gender was 18 women and 16 men (Table  1). Average sagittal advancement at T1 was 6.6 mm and at T2 was 6.4 mm, decreasing just 3% in a 1-year follow-up. The inferior movement was an average of 5.6 mm at the level of the bone pogonion at T1 and T2, showing both movements excellent stabil- ity. The mentolabial angle increased at T2 by an aver- age of 28.2 degrees (5 degrees per each millimeter of inferior movement), whereas the depth of the mentola- bial fold decreased by an average of 2.8 mm (decreased 49% from the initial depth, and decreased 0.56 mm per each 1 mm of inferior movement). The average increase of the lower third of the face was 5 mm (89% of infe- rior the bone movement) (Table 2). No complications Fig. 1. M-shaped genioplasty. A, Lateral view of virtual planning, forward and downward movement. B, Hatched area: slanted bicel cut. Fig. 2. M-shaped genioplasty. A, Lateral view of virtual planning, forward and downward movement. B, Hatched area: slanted bicel cut. PRS Global Open • 2023 4 were observed in any patients, and a good stability was observed after a 1-year follow-up. DISCUSSION Genioplasty is a mandibular osteotomy that is used to correct structural and spatial anomalies of the chin. Multiple designs have been described that want to cor- rect the underlying skeletal anomaly.3 Among its multi- ple design alternatives, Fariña et al6 described M-shaped genioplasty in 2012, which allows the modification of the position of the chin in the vertical and sagittal plane. It is an easy technique to perform, and it requires precise presurgical planning to determine the inclination of the corresponding inclined plane for each case, to allow the chin movement in the desired direction and magnitude. It reduces the morbidity of another technique describing the same objective (genioplasty with interpositional graft placement) and its complications. This technique can also change the transversal plane to center the chin, with an inferior and lateral movement Fig. 3. CBCT before (A) and after (B) (T2) bimaxillary surgery. The position of the bone pogonion was measured vertically and horizontally from a line perpendicular to the occlusal plane passing through the incisal edge of the lower central incisor. This measurement was done to eliminate the effects of BSSRO on the vertical and sagittal movement. B, Before surgery, the Pg height was 29.7 mm and it was 5.8 mm behind the perpendicular line to occlusal plane from the incisal border. After surgery, the Pg height was 36.1, and it was 5.8 mm forward (touching the vertical line from incisal edge). Fig. 4. Lateral view. Before (A) and after (B) L1 (impaction surgery), BSSRO and M-shaped genioplasty. Note the change in mentolabial angle. Fariña et al • M-shaped Genioplasty 5 (Fig.  2). At the same time, we have found that it allows to decrease the mentolabial fold and increase the mento- labial angle, optimizing aesthetic results in patients with deep mentolabial fold and acute mentolabial angle. This occurs because, when the bony chin moves down, the mentalis soft tissues are pulled, mobilizing them caudally. This is an advantage in patients with a small chin and deep mentolabial fold, who require genioplasty of advancement (Fig.  3). Reddy et al10 demonstrated that conventional advancement genioplasty causes an average of 1.14 mm increase in the depth of the mentolabial fold. A limitation of this study is that we did not measure patient-related outcomes, so future research should include this information to know the impact of genio- plasty on postoperative outcomes directly from patients. Moreover, a widely used PROM is the Oral Health-Related Fig. 5. Frontal view. Before (A) and after (B) L1 (impaction surgery), BSSRO, M-shaped genioplasty and rhinoplasty. Fig. 6. Lateral view. Before (A) and after (B) L1 osteotomy, BSSRO (counterclockwise movement) and M-shaped genioplasty. PRS Global Open • 2023 6 Quality of Life (OHRQoL), which refers to the impact of oral conditions on at least three dimensions of quality of life, including physical, emotional, and social well-being. Also, OHRQoL could be measured by generic or disease- specific instruments. In this way, Disease-specific ques- tionnaires may show intervention-related changes more precisely than the generic ones, applicable to all popu- lations. The Orthognathic Quality of Life Questionnaire is the only validated instrument to measure OHRQoL in patients with dentofacial deformities.11 In this retrospective descriptive study, the patients included are all those operated on in the time interval described. The two-step method for gender identity col- lection was not used. Although this method is not widely used in Chile, the lack of this identification could be considered a limitation of the study as it does not fully Fig. 7. Frontal view. Before (A) and after (B) L1 osteotomy, BSSRO (counterclockwise movement) and M-shaped genioplasty. Fig. 8. Lateral view. Before (A) and after (B) BSSRO, M-shaped genioplasty, and otoplasty. Fariña et al • M-shaped Genioplasty 7 represent the patients and how they identify. Oftentimes, the limiting binary options with the addition of “other” might be considered offensive12 or inaccurate, which is why the two-step method provides people with validation as well as an option for those who prefer to decline to state. This two-step method is recommended and encouraged Fig. 9. Lateral view. Before (A) and after (B) BSSRO, M-shaped genioplasty, and otoplasty. Fig. 10. Lateral view. Before (A) and after (B) M-shaped genioplasty and rhinoplasty. Table 2. Average Measurements of the Variables under Study Patient 34 Anterior Movement Pg (mm) T1/T2 Inferior Movement Pg (mm) T1/T2 Mentolabial Angle: Before/After (T0/T2) Mentolabial Fold (mm): Before/ After (T0/T2) Increase of Lower Third Measured from Inferior Incisal Edge to Soft Me (mm) in Vertical Line from Frankfort Plane (T2) Average 6.6/6.4 (97%) 5.6/5.6 100.4°/126.8° (↑28,2°) 7/ 4.2 (↓2.8) 5 PRS Global Open • 2023 8 for future research to gather more accurate data on the individuals and provide representation to those who felt neglected. M-shaped genioplasty is a good alternative for those cases in which it is required to mobilize the chin for- ward and downward, decrease the mentolabial fold, and increase the mentolabial angle. CONCLUSIONS M-shaped genioplasty is an anterior osteotomy of the mandible, which allows the chin to move forward and downward. In addition, it increases the mentolabial angle and decreases the mentolabial fold. After 10 years of experience, it has proven to be sim- ple, versatile, and stable over time, with low associated morbidity. Rodrigo Fariña, DMD, Med Av. Providencia 2330, OFF 33 Santiago, Chile E-mail: rofari@gmail.com PATIENT CONSENT Patients provided written consent for the use of their images. REFERENCES 1. Janssens E, Shujaat S, Shaheen E, et al. Long-term stabil- ity of isolated advancement genioplasty, and influence of associated risk factors: a systematic review. J Craniomaxillofac Surg. 2021;49:269–276. 2. Chang E, Lam S, Karen M, et al. Sliding genioplasty for correc- tion of chin abnormalities. Arch Facial Plast Surg. 2001;3:8. 3. Michelet F, Goin J, Pinsolle J, et al. L’utilization de la symphyse mentionniere. Ann Chir Plast. 1974;19:69–75. 4. Qeytoni D, Zribi A, Raphael B, et al. Les Genioplasties: tech- niques et applications. Rev Stomatol Chir Maxillofac. 2007;108:441. 5. Kim J-Y, Kim J-K, Park J, et al. 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