Nasal sill augmentation: an overlooked concept in rhinoplasty—a technical note and review of the literatures

Background Nasal sill is one of the components of the alar ring, affecting the esthetic outcomes of rhinoplasty; accordingly, we developed a novel technique to adjust defects in this area and compared it with the available techniques. Methods Our technique was based on creating a tunnel access to the nasal sill area through an incision made in the lower third of the columella using the open approach or through a nostril base incision in patients, who underwent alar base reduction, followed by insertion of a cartilaginous graft into the marked defect area. Results A total number of 54 patients with a defect in the nasal sill area were included in this study. Thirty-one patients underwent open rhinoplasty with the sill approach from the lower third of the columella, while 23 patients underwent rhinoplasty with a nostril base approach for nasal sill augmentation procedure. There were no reports of patient dissatisfaction, infection, bleeding, sensory dysfunction, or remaining asymmetry of the sill area. Conclusion Based on the findings of the present study, this technique can be successfully used in reconstructing the nasal sill area with minimal complications and morbidity. Supplementary Information The online version contains supplementary material available at 10.1186/s40902-021-00298-3.

nasal sill soft tissue can result in deformities, such as tear-shaped nostrils [6].
On the contrary, nasal sill area augmentation has not received much attention so far, although the use of this technique is quite practical for cases, such as uni/bilateral cleft lip or cleft lip and palate, traumatic lesions, congenital asymmetry of the nostril size, secondary revision surgeries, and reconstruction of defects caused by malignancies (e.g., basal cell carcinoma) [7]. So far, few methods and techniques have been introduced for the nasal sill graft procedure [5,[8][9][10]. Therefore, in this study, we aimed to introduce our novel sill graft technique that can be safely used for most of the aforementioned cases.
This study aims to introduce a novel technique for nasal sill augmentation and compare it with previous techniques briefly. The hypothesis is that the clinical outcome of this technique is optimal esthetic results with minimal morbidity and postoperative complications.

Indications
1. During esthetic rhinoplasty, the need for nasal sill grafting/augmentation may be considered by a surgeon during an esthetic surgical procedure on the nose. For instance, when esthetic rhinoplasty is undertaken to reduce the width of the columellar base, the soft tissue complex, including muscles, ligaments, fibrosis tissue, and fat, is removed. The surgeon then reduces the width of the columellar base by suturing the structures in close proximity. The possibility of hollowing in the sill area can be one of the side effects of this process that must be considered by surgeons, and appropriate measures must be taken to adjust it. Overall, the sill graft can be considered as an appropriate treatment option for this condition. 2. In patients with cleft lip and palate, the lack of a well-defined nostril sill is often due to the presence of a poor-quality scar tissue. The decision about the type of graft is made, depending on the quality of soft tissue in the area. Scarred and adherent soft tissue quality may require the use of a chondrocutaneous composite graft for the reconstruction procedure. 3. Severe deviation of the nasal septum is another factor that may significantly affect the bulging of the sill area. One of the most serious complications of this condition is the asymmetry of the nostril sills, which may not be even compensated by the correction of the nasal septum deviation and may require separate reconstruction. 4. Inherent or trauma-related nasal sill deformities, besides deformities due to malignancies.

Surgical technique
All procedures were performed by an oral and maxillofacial surgeon in the hospital setting during 2018-2020.  Informed consent was obtained after the surgical procedure, potential risks, and complications were described to all patients. The surgery was performed under general anesthesia. Local anesthesia (2% lidocaine with epinephrine at a concentration of 1:80,000) was administered in the surgical field. The cartilaginous graft is harvested from the nasal septum in the priority for each patient. If it is not possible, cartilaginous ear grafts, allografts, and even autogenous rib grafts were the next donor sites consecutively. In the open approach, access to the sill area was achieved through a rhinoplasty incision made, in the lower third of the columella. Also, access to the sill area in patients, who underwent alar base reduction, was achieved through an incision in the nostril base area (Fig. 1). A subcutaneous pocket was dissected from the deficient nasal sill, using converse dissecting scissors.
Commonly, due to the presence of scar tissue and inadequate normal soft tissue in cleft lip and palate patients, there is often a need for scar revision and muscle repositioning. However, since this study aimed to show that nasal sill augmentation is not necessarily limited to cleft patients, individuals with simple congenital asymmetry in the sill area were also selected for photographic evaluation.
The nasal sill augmentation process is not usually performed as an independent procedure and is often a complementary corrective procedure during rhinoplasty or cleft lip repair process, after ensuring the proper form and symmetry of the ala. The remaining steps of the procedure, such as suturing incisions and dressing, are performed during standard rhinoplasty procedures.
For more information about different steps and variations of this technique, the supplemental materials section of this article is available on the website of the Journal of Oral and Maxillofacial Surgery (videos 1 and 2).

Literature review
A literature review was performed to evaluate previously described techniques addressing for nasal sill deficiency. A comprehensive search was undertaken in PubMed and Scopus databases, without any time restrictions, using keywords related to reconstruction, augmentations, or graft procedures in the nasal sill area, which are as follows: ("nostril sill" OR "nasal sill") AND ("Reconstructive Surgical Procedures" OR augmentation OR reconstruction OR graft). Figure 2 presents the PRISMA flowchart regarding the search results and screening. Title, abstract, and full-text screening was performed by two independent researchers. Finally, a total of 19 articles were included in this study.

Results
A total number of 54 patients (19 males and 35 females) with a defect in the nasal sill area were included in this study. The mean age of the patients was 31 years. The candidates for nasal sill   (4) 3.5 ± 0.1 Question 3: Do you believe your friends and people who are dear to you like your nose?
Absolutely no (0), A little (1), More or less (2), Very much (3), Absolutely yes (4) 2.9 ± 0.8 Question 4: Do you think the current appearance of your nose hampers your social or professional activities?
Certainly yes (0), Very likely yes (1), Possibly yes (2), Probably no (3), Certainly no (4) 3.6 ± 0.  augmentation included esthetic rhinoplasty patients (n=21), patients with cleft lip nasal deformities (n= 12), patients with congenital sill defects (asymmetry or absence of the sill) (n=9), patients who underwent removal of a malignant lesion (n=5), and patients with traumatic injuries (n=7). Thirty-one patients underwent open rhinoplasty; therefore, access to the sill graft was achieved from the lower third of the columella. Also, 23 patients underwent the nasal sill augmentation procedure, using a nostril base approach.
The follow-up duration ranged from 11 months to 3 years (mean 1.3 years). The same surgeon evaluated the patients in the follow-up sessions. The patients' satisfaction was evaluated using the Rhinoplasty Outcome Evaluation Form (ROF) by Izu et al., adapted from a study by Guillemin et al. [11,12]. Table 1 presents the mean scores of patients' satisfaction at the end of the follow-up. There was no report of patients' dissatisfaction at the end of the follow-up. Also, there were no significant complications, such as infection, bleeding, sensory dysfunction, or remaining asymmetry of the sill area. Figures 3, 4, 5, 6, and 7 present the final outcomes at the end of the follow-up in five patients, who underwent sill graft procedures. Table 2 presents the findings of articles, addressing the sill graft/augmentation in terms of the techniques, approaches, clinical results, and complications.

Discussion
The nasal sill area is a key component of the alar ring, which needs to be considered by surgeons during the nasal base reconstruction procedure [13]. Augmentation of this area is indicated when conditions, such as congenital asymmetrical nostrils, cleft lip and palate, malignancies, or traumatic lesions, occur [20].

Surgical anatomy
The emphasis on the precise anatomical considerations in the sill area helps the surgeon to have a broader horizon to reach the optimal esthetic results. The alar ring is the most caudal area of the nose, which involves the edge of the nostril, extending to the alar base. It contains the alar cartilage with lateral and medial crura, as well as A1 to A4 accessory cartilages, positioned along the tail of the lateral crural cartilage [29] (Fig. 8). The boundaries of the nostril opening (alar ring) contains alar lobules, columellar base, and nostril sill [30]. As an alar ring subunit, the nasal sill is a protuberant soft tissue bridge, extending from the base of the columella to the ala of the nose, separating the upper lip soft tissue from the nasal vestibule cephalocaudally [30]. The nostril sill is situated approximately in the area of A3 and A4 cartilages. Also, the nostril sill can vary based in terms of width, height, and shape ( Fig. 9). In 1995, Irwin et al. categorized the nostril sill into three main types; 1. In Full/Sill-proper type, a protuberant area connects the columella and the ala. It is the most common variant with the greatest muscle and soft tissue thickness of all three [31]. 2. In the Point type, the medial and lateral walls of the nostril sill approximate each other to form an apex. 3. In the Flat type, there is no soft tissue protuberance between the vestibule of the nose and the upper lip, with the least soft tissue thickness [31,32] (Fig. 10).
The direct relationship between the nostril shape and sill area can be inferred from two measurable angles in this area. Figure 11 shows the angle between the longitudinal axis of the nostril and the horizontal plane, and the second angle is between the medially inclined nasal sill and the sagittal plane. An elliptical or pear-shaped nostril with a longitudinal axis angle of 45°has higher esthetic values [6]. These angles can be considered and recorded in the patient's preoperative analysis.
Muscle insertions of the nostril sill area include the depressor septi nasalis, myrtiformis, and dilator naris (DN) muscles, which originate from the maxilla and insert into the soft tissue and skin of the nares. The tela subcutanea cutis (TSC) that can be seen in this area (Figs. 12, 13, and 14) is a folded layer of dermis and subcutaneous tissue that connects the lateral and medial crura when seen from the basal view.
Other anatomical considerations in the sill area include the superficial and deep pitanguy's ligaments, which extend caudally between the lower lateral cartilages and continue along the superficial orbicularis oris nasalis (SOON) and depressor septi nasalis (DSN) muscles, respectively (Fig. 15).
Our experience in the present study revealed that the proper symmetry and shape of the alar base and nostrils are dependent on the precise evaluation and further reconstruction of the nasal sill dimensions, especially in unilateral deformities where the normal shape of the sill is achieved similar to the normal side. In minor sill defects, muscle repositioning, specific suturing techniques, and small soft tissue grafts may result in the satisfactory elevation of the sill area [19]; however, in larger defects, composite grafts may be required to achieve the desired clinical outcomes [27].
Among esthetic rhinoplasty patients, those who require nasal tip modification and correction of gross septal deviation or perforation, as well as those who undergo esthetic rhinoplasty through an open approach, augmentation of the sill area can be performed using an open approach if needed (Fig. 1b). Also, in esthetic rhinoplasty patients, who require alar base reduction and have defects in the sill area,   insertion of the sill graft through the alar base incision can be highly useful (Fig. 1c).
The review of published literature, addressing the concept of nasal sill augmentation, revealed that cleft palate patients require major corrections for sill defects (Table 2). Therefore, special attention must be paid to nasal sill reconstruction in these patients. However, nasal sill reconstruction in these patients is not usually performed as an independent procedure but as part of the cleft repair process. Dissection and repositioning of the orbicularis oris and depressor septi muscles is often the most preferred technique for sill augmentation in these patients [13,23,24]. Repositioning of the medial and lateral flaps of the upper lip during cleft closure is another method for reconstruction of the sill area [22]. Although no major complications were reported for this method, the absence of graft can occasionally result in further depression of the sill area in the long term.
As mentioned earlier, no complications were detected among the participants of our study; however, infection, bleeding, ischemia, flap necrosis, complications associated with the harvesting procedure, graft deviation, obvious scar, excessive decrease in the nostril size, impaired ventilation, shortening of the upper lip, and sensory dysfunction are among potential complications, which require strict considerations, especially in the follow-up examinations [10,20,23,25]. Earlobe-derived cartilage grafts do not offer satisfactory esthetic results in the sill area and are associated with complications in some cases [20]. Instead, alveolar bone grafting in 18 unilateral cleft lip and palate patients with tension-free sutures produced optimal esthetic outcomes in the nasal sill area [19], with significant improvement in the width and height measures of the cleft site.
A review of previous studies showed that many of the published techniques are based on the Fig. 9 The nasal sill can have variety in terms of (a) width (b) height, and (c) shape transposition of flaps [13,14,18,[22][23][24]. The application of these techniques may be justified for patients with clefts or those with malignancies, where a part of the soft tissue is usually deficient. However, the use of these techniques in patients, who are diagnosed with simple congenital defects, seems extremely aggressive. On the other hand, the conservative design of our technique and the lack of extensive flaps provide an opportunity for nasal sill reconstruction in patients with congenital defects. In other words, the non-invasive design of our technique and providing a solution for nasal sill reconstruction in patients with congenital defects can be considered the most significant advantages of this study. However, the possibility of using our technique for patients with clefts, malignancies, or traumatic lesions cannot be rejected. Recurrent asymmetry following graft deformity may be the most important limitation of this technique. Overall, ensuring that the graft is stable and fixed in its position can be very helpful in preventing the occurrence of this complication. However, in such cases, a secondary revision intervention is required.
In general, one of the advantages of this procedure is that it is not technique-sensitive, and it is easy to perform. Also, this technique is repeatable and does not produce a remarkable scar in the surgical site. On the other hand, its disadvantage is donor site morbidity.