Step-technique genioplasty: A case report

Abstract

Introduction

Genioplasty is the gold standard technique to modify natural chin anatomy based on an inferior border osteotomy of the mandible enabling 3D-repositioning of the chin. Our “step-technique genioplasty” is a modified and improved surgical technique for advancement genioplasty in patients with elusive chin and vertical excess of the lower third.

Case presentation

We performed this technique on a 23-year-old female patient with a history of facial trauma that affected the morphology and aesthetics of the lower third.

The surgery consisted of two osteotomy lines. The first osteotomy line was a monocortical osteotomy allowing to preserve the integrity of the lingual cortex. About 3 mm below, the second and complete bicortical osteotomy was performed to mobilize the chin segment. A bone fragment containing the vestibular cortex and medullary portion of the mandible was removed preserving the integrity of the lingual cortex and creating a bony step in mandibular symphysis. The osteotomized chin was advanced in the front of the bony step.

Discussion

Compared with known techniques, step-technique genioplasty allowed addressing the vertical chin excess not only at the level of the symphysis but also posteriorly with no over-projection of the chin and no deepening of the labiomental crease, common downsides in other approaches.

Conclusion

The aesthetic outcome reflected the preoperative planning: we obtained a smoother transition between symphysis and horizontal branch of the mandible, just the right amount of anterior projection of the chin, greater stability, and predictability of the outcome with satisfying aesthetical results and no complications.

Highlights

• •Genioplasty is the gold standard to modify the chin based on a mandible inferior border osteotomy enabling chin 3D-repositioning.
• •Step-technique is an improved advancement genioplasty, especially indicated on elusive chins with lower third vertical.
• •Step-technique obtains greater bone contact for better stability of the mobilized fragment, better aesthetics, faster healing.

1. Introduction

The chin has an important role in facial aesthetic harmony due to its projection and vertical length and it affects the facial profile in its lower third. Altering these supports allows to radically modify the appearance of the skeleton and soft tissues.

Genioplasty is the gold standard technique to modify the natural chin anatomy based on an inferior border osteotomy of the mandible enabling 3D-repositioning of the chin. The first chin advancement osteotomy was performed by Otto Hofer with an extra-oral approach on a cadaver, but the first official ‘genioplasty’ with an intraoral approach was executed by Trauner and Obwegeser in 1957 [1]. Afterward, especially in the last ten years, several types of genioplasty were introduced to improve esthetical results, reduce recovery time and complications (facial nerve damage, mental nerve paresis, swelling, and bleeding), and improve the surgical technique [2]. The standard genioplasty is the sliding genioplasty, based on an oblique osteotomy of the symphysis with chin repositioning, as described by Trauner and Obwegeser [1]. An improved genioplasty design to reduce aesthetic complications of this conventional approach (decreasing in vertical height and deepening of the mentolabial fold) is the sagittal split genioplasty by Schendel [3].

The purpose of this study is to present a modified and further improved surgical technique for advancement genioplasty, especially indicated in patients with an elusive chin with vertical excess of the lower third, called “step-technique genioplasty”, which allows obtaining a greater bone contact surface to offer better stability to the mobilized bone segment, ensuring a regular jawline, better aesthetic results, and faster healing. All our work has been reported in line with the SCARE criteria and guidelines [4].

2. Case presentation

In January 2017, a 23-year-old female patient referred to our Department of Maxillofacial Surgery suffered from Class II malocclusion induced by facial trauma, which occurred in 2003. The trauma involved mandibular symphysis and condyles bilaterally. The fractures were treated and stabilized in another center briefly after the accident. An X-ray orthopantomography, an X-ray telecranium, and a CT scan of the facial bones have been requested for further diagnostic analysis to confirm the findings of the clinical examination. These exams showed a good occlusal plane but an extraoral examination suggested to us that a restoration of the morphology and aesthetics of the lower third was necessary. Facial scans and preoperative planning with Dolphin Imaging (Version 9.0, Dolphin Imaging Software, Canoga Park, LA) to plan the chin osteotomy was performed. In May 2021, the patient underwent surgery. The surgical treatment plan was a “step-technique genioplasty” with chin advancement and impaction to reduce the vertical excess in the lower third of the face.

The surgery was performed under general anesthesia and the patient was positioned in dorsal decubitus. Nasotracheal intubation was performed to allow the positioning of the rigid intermaxillary fixation (IMF). IMF increases the stability of the bone segments and facilitates osteotomy. The rigid IMF was placed using one screw in the region of the incisors on both the upper and the lower jaw. The screw on the maxilla was connected to the one on the mandible with a metal wire to stabilize the occlusion. A 3 cm mucosal incision was carried out on the inferior vestibular fornix and the mentalis muscle was cut as well. The mandibular symphysis was then surgically exposed by atraumatic subperiosteal dissection preserving the muscle insertion and the soft tissues in the lower part of the symphysis to ensure the vascular supply of the bone segment. The emergence of the mental nerve was identified and the median of the chin was marked by positioning a screw to facilitate the subsequent repositioning of the bone segment. The osteotomy was performed using piezosurgery (Piezosurgery Plus, Mectron s.p.a. 2014) with a short-angled tip (MT5-10L). The osteotomy lines began in the median region and extended laterally about 5 mm below the mental foramen, making sure to preserve the roots of the dental elements (Fig. 1). The first osteotomy line was a monocortical osteotomy allowing to preserve the integrity of the lingual cortex. About 3 mm below, the second and complete bicortical osteotomy was performed to mobilize the chin segment. A bone fragment (Fig. 2) containing the vestibular cortex and medullary portion of the mandible was removed by chisel preserving the integrity of the lingual cortex and creating a bony step in mandibular symphysis. The osteotomized chin was mobilized using the bone anchoring screw as a traction point and advanced in the front of the bony step. This movement allows a simultaneous advancement and impaction of 3 mm of the chin, as preoperatively planned, ensuring greater support for the repositioned segment, greater stability to the internal fixation, and counteracting the traction forces of suprahyoid muscles. The osteosynthesis of the segment was carried out using 2 titanium plates intraoperatively modeled by the surgeon. The integrity of the mentalis muscle was restored by a 4.0 Vicryl suture to prevent any alteration of the labiomental angle and the mucosal layer was sutured with 4.0 Rapid Vicryl. A genioplasty dressing was applied for 3 days postoperatively together with cryotherapy to prevent swelling and gaps in the soft tissues.

Fig. 1.

(A) Upper monocortical osteotomy line and lower bicortical osteotomy line performed by piezosurgery; (B) mobilization of the bone fragment containing the vestibular cortex and medullary portion; (C) chin advancement in front of the bony step; (D) chin osteosynthesis by two titanium plates.

Fig. 2.

Bone fragment containing the vestibular cortex and medullary portion of the mandible.

An X-ray orthopantomography was done the first day after surgery to check the bone repositioning and stability of the titanium plates. The patient underwent postoperative check-ups for 4 weeks following the surgery to ensure the correct healing of surgical incisions. A new X-ray was done 2 months after surgery, demonstrating complete bone healing and plates stability (Fig. 3).

Fig. 3.

(A) X-ray orthopantomography pre-op; (B) X-ray orthopantomography 2 months after surgery.

No complications such as hematomas, hemorrhages, infections, and sensory alterations in the area innervated by the mandibular branch of the trigeminal nerve, were highlighted. The aesthetic outcome reflected the preoperative planning. Soft tissues adapted satisfactorily to the new position. The lower third morphology was aesthetically satisfying (Fig. 4).

Fig. 4.

(A) 3D-imaging pre-op; (B) virtual surgical planning performed with Dolphin Imaging; (C) 3D-imaging 2 months after surgery.

3. Discussion

The chin is defined by Riedel's lines or facial harmony lines which connect the most prominent points of the upper and lower lip with the chin point above the pogonion and define the preferable projection of the chin. Any alteration of these proportions affects the balance and harmony of the face [5].

Many discrepancies in the chin structure can be congenital and they can even be accentuated by orthognathic procedures, but they can also be a consequence of facial traumas, such as in our case. Our patient showed a vertical excess and a sagittal setback of her chin after correction for mandibular symphysis and condyles fracture. The vertical excess, extending also more posteriorly along the horizontal branch of the mandible, made the chin look broader and flatter. For this reason, as stated by Tulasne, the correction should have been not only anterior but also posterior to be complete. Sliding genioplasty and other conventional techniques did not seem to be the best options in our case, since they only address the mandibular symphysis [6]. Our step-technique genioplasty technique allowed instead to create a central posterior bony step and reposition the anterior fragment of the chin on top of it, ensuring excellent and stable bone contact and avoiding palpable bony steps. Simultaneous advancement and impaction of 3 mm of the chin, with a smoother transition between symphysis and horizontal branch of the mandible, were possible.

Step-technique genioplasty showed also advantages compared to Tessier's split-overlapping genioplasty. Roul-Yvonnet et al. underlined how split-overlapping genioplasty frequently caused an overcorrection of the projection of the chin with anterior notches and deeper labiomental creases, which looked particularly antiaesthetic in women [7]. Women prefer, in fact, a more narrow, less projected, and V-chin with one-point light reflection [8]. With step-technique genioplasty, a better labiomental contour was obtained by removing a bone segment and using partial osteotomies. The degree of advancement can also be adjusted based on the dimensions of the bone segment and osteotomies, similarly to the stair-step genioplasty [11]^, [12].

The small size of the removed bony segment and the bony step allowed only a minimal degree of anteroposterior rotation of the lower segment of the chin [9]. Therefore, the bony step ensured greater central support for the repositioned chin and counteracted the traction forces of suprahyoid muscles without compromising the lateral stability. This way outcomes of the internal fixation showed to be more stable and predictable. The greater stability given by the greater bone contact prevented also long-term complications, such as mobility and pseudarthrosis of the bone segments.

Furthermore, the use of virtual surgical 3D-planning of the osteotomies and segment repositioning with Dolphin Imaging allowed in the preoperative phase to quantify the amount of bone to be removed to obtain the desired aesthetic result by simulating the deformation of soft tissues. Therefore, the final result was more predictable and accurate, even without a cutting guide [10].

The overall aesthetical result showed to be satisfactory both for the patient and for our surgical team, clinically and radiologically.

The drawback of this study is instead the fact that this technique was only performed on one patient and it should be assessed on several ones to support our findings and to determine if it can be useful also for bigger defects.

4. Conclusion

Our step-technique genioplasty technique is an effective option for the advancement and reduction of the vertical excess of the chin. It showed a smoother transition between symphysis and horizontal branch of the mandible, just the right amount of anterior projection of the chin, greater stability, and predictability of the outcome with satisfying aesthetical results and no complications.

Informed patient consent

Signed patient consent was obtained for the subject of the study in accordance with the declaration of Helsinki.

Consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Ethical approval

This study is based on the description of a single surgical procedure therefore a clinical trial and approval of the ethics committee is not required.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Guarantor

Dott. Fabio Maglitto.

Research registration number

• 1.Name of the registry: None
• 2.Unique identifying number or registration ID: None
• 3.Hyperlink to your specific registration (must be publicly accessible and will be checked): None.

CRediT authorship contribution statement

• Fabio Maglitto: Project administration, Supervision

• Marco Friscia: Methodology, Resources

• Lorenzo Sani: Writing – Review & editing, Methodology

• Sara Piloni: Writing – Original draft, Investigation

• Giovanni Salzano: Formal analysis, Conceptualization

• Luigi Califano: Validation.

Declaration of competing interest

None.