Linear analysis of the nasal septum in patients treated with surgically assisted rapid maxillary expansion

Introduction

Surgically assisted rapid maxillary expansion is a widely used surgical procedure for resolving transverse maxillary occlusal changes in patients with bone maturity. However, few studies about the postoperative morphologic alterations in the nasal cavity in its inferior portion and the nasal septum positioning exist.

Methods

The linear nasal septum measurements of 26 adult patients treated with surgically assisted rapid maxillary expansion from 2009 to 2013 were assessed through a retrospective analysis of cone-beam computed tomographies, in Digital Imaging and Communications in Medicine files, through the Dolphin Imaging program (Dolphin Imaging and Management Solutions, Chatsworth, Calif), aimed to identify significant changes during 3 time periods of the treatment: preoperative, immediately after the palatal expansion device locking (immediate postoperative), and 6-months postoperative (late postoperative). The analyses were performed in the inferior third of the nasal septum, from 4 equidistant points in anteroposterior position and height, using fixed cranial references for lateral measures of displacement.

Results

No significant difference was found between preoperative, immediate postoperative, and late postoperative measurements in the 4 fixed nasal septum measurements, applying the analysis of variance test with a significance level of 5%. Comparing the surgical times alone, we found no statistically significant difference between the right and left sides applying the Student t test, which also showed symmetry in the nasal septum.

Conclusions

The measurements of the nasal septum did not change in the different surgical times throughout their inferior extension, and they remained symmetrical throughout patients’ follow-up period.

Highlights

  • Maxillary expansion surgery without the release of nasal septum does not cause its deviation.

  • The nasal septum remains symmetrical in the 6 months postoperative stage.

  • The insertion of the nasal septum does not need osteotomy in maxillary expansion surgery.

Surgically assisted rapid maxillary expansion (SARME), originally proposed in 1938, is a widely used surgical procedure for resolving transverse maxillary occlusal changes in patients with bone maturity, through the osteotomy of the maxillary midline, allowing the lateral dislocation of the palate. This technique was further improved by some authors, who added osteotomies in other maxillary force abutments, such as zygomatic-maxillary pillars, nasal septum, pterygopalatine processes, and lateral nasal pillars, to facilitate the expansion of the maxilla and make this movement more predictable, one of the most common technique being the one proposed by Bell and Epker in 1976.

With the popularization of SARME over the years, other studies were necessary to reduce the index of complications inherent to the technique, one of the most critical being the one related to the postsurgical instability. A question that has existed in the literature since the beginning of the application of SARME, as already questioned by Haas in 1961 during the study of the nonsurgical maxillary expansion technique, refers to the transoperative and postoperative surgical displacement of the nasal septum.

Nasal septum deviation is often associated with respiratory troubles, which is common in maxillary atresia, and rectification of the nasal septum would be important after surgically assisted expansion. Some authors even propose SARME with nasal septum osteotomy at its insertion in the maxilla, justifying that there is a possibility of nasal septum’s deviation or lateral displacement or a possibility of alteration of the nasal airways during the distraction phase if SARME with nasal septum osteotomy is not performed. ,

Despite the importance of nasal septum placement in the postoperative period, there are few articles in the literature that have studied nasal septum changes after the SARME procedure, most of which approach the positions and changes only through 2-dimensional clinical or imaging tests. There is a lack of consensus in the literature regarding the need to perform the osteotomy of the septum base to avoid its deviation. Considering that this osteotomy increases postoperative morbidity, it is necessary to identify whether such a technique is fundamental for preserving the septum position. Therefore, the present study aimed to compare the position of the nasal septum before SARME and in the immediate and late postoperative period to verify if there were any significant changes.

Material and methods

This study was approved by the Ethics Committee of the School of Dentistry of Ribeirão Preto, University of São Paulo (protocol number: 56389416.0.0000.5419). The linear nasal septum measurements of adult patients treated with SARME at the Oral and Maxillofacial Surgery Residency Training Program at the School of Dentistry of Ribeirão Preto from 2009 to 2013 were assessed in a retrospective analysis of cone-beam computed tomography (CBCT) images obtained at 3 time periods of the treatment: preoperative, immediately after the palatal expansion device locking (immediate postoperative), and 6 months after the expansion device locking (late postoperative). Patients were discarded from the study on the basis of the following criteria: did not perform CBCT at the correct time, did not respect the preoperative and postoperative protocol (medication use, diet, etc), abandoned treatment for any reason, had a history of nasal septum surgery, used drugs with interference in bone metabolism (long-term corticosteroids, bisphosphonates, etc), underwent a new surgical intervention in the same place, Hyrax palatal expansion device used for expansion presented with a problem during the period of follow-up or activation, and had any syndrome that could somehow interfere with the results of the research. The final sample consisted of 26 patients, with a mean age of 30.58 years.

The Hyrax device, placed in all patients by the same orthodontist, had bands positioned bilaterally in the maxillary first premolars and first molars. The device had a palatal extension from the canine mesial to second molar distal, on both sides, and was made of 0.8-mm steel wire. It was placed at a minimum distance of 2 mm from the palatal mucosa to avoid its contact during activation.

During the SARME procedures, an osteotomy was performed through the zygomaticomaxillary pillar in the lateral wall of the maxilla to the nasal pyriform aperture on both sides, according to the technique proposed by Bays and Greco. The pterygoid plaques and the nasal septum were not osteotomized. After initial procedures, a vertical incision was made on the labial frenum with a number 15 surgical blade, followed by a soft tissue detachment restricted to this topography. A medial osteotomy between the central incisors was first demarcated through surgical drill number 701, and then the maxillary separation was completed with a Sverzut chisel and hammer. The expander was then activated 8 times and deactivated 4 times, resulting in 1 mm of activation. After a 1-week latency period, 2 activations (2/4 turn) were indicated in the morning and 2 more activations (2/4 turn) in the afternoon, totaling 1 mm of activation per day, until adequate expansion was achieved, and the device was then locked for 6 months.

All the CBCT scans were saved in Digital Imaging and Communication in Medicine format and standardized using Dolphin Imaging software (version 11.9; Dolphin Imaging and Management Solutions, Chatsworth, Calif), similarly to previous studies, , in the coronal plane, following a line connecting the infraorbital margin bilaterally, in the axial plane by a horizontal line connecting the PNS and the ANS bilaterally aligned, and in the sagittal plane, established through the horizontal plane of Frankfurt.

The same evaluator performed all the linear measurements, and calibration was performed in 20% of the patients. After standardization of the cranial positioning, linear measurements ( Table I ) were performed on the preoperative CBCT scans of each patient, making them reference for immediate and late postoperative CBCT scans.

Table I
Linear measurements
Measurement Definition
ML (midline) The point in the middle of the distance between the right and left spinous foramen, viewed in the coronal tomographic cut ( Fig 1 )
PML (posterior midline) The meeting of the posterior horizontal projection of a line drawn from the posterior nasal spine (PNS) to the anterior nasal spine (ANS), passing through the highest point of the premaxilla, with the bottom vertical projection of the ML point, at the cut of the ML point, viewed in the sagittal tomographic cut.
P2, P3, P4 and PNS Four equidistant points dividing the distance between ANS and PNS in the sagittal cut ( Fig 2 )
ZML (zygomatic arch midline) A measure coinciding with or superiorly to the ML point, where the visualization of the bilateral zygomatic arch was complete, allowing it to be used to project the lowest points of the nasal septum, based on the coronal and axial tomographic cuts ( Fig 4 )
P2′, P3′, P4′ and PNS’ Reference points following the projections of the P2, P3, P4 and PNS at the height of the ZML point, allowing the visualization of the zygomatic arch throughout its anteroposterior extension, viewed in the sagittal tomographic cut ( Fig 5 )
P2’R, P3’R, P4’R and PNS’R Measurements at the ZML height from the projected reference points P2′, P3′, P4′ and PNS’ until the right side of the zygomatic arch, in axial tomographic cut ( Fig 6 )
P2’L, P3’L, P4’L and PNS’L Measurements at the ZML height from the projected reference points P2′, P3′, P4′ and PNS’ until the left side of the zygomatic arch, in axial tomographic cut ( Fig 6 )

In the 2-dimensional coronal tomographic cut, points called landmarks were marked on the right and left spinous foramen, and between these, in the middle of the distance, the first reference point is called the midline (ML) ( Fig 1 ). Then, in the sagittal tomographic window, at the cut of the ML point, a line was drawn from the posterior nasal spine (PNS) to the anterior nasal spine (ANS), which passed through the highest point of the premaxilla. The meeting of the posterior horizontal projection of this line with the bottom vertical projection of the ML point was called the posterior ML and provided the height of the maxilla in relation to the ML point. This height was fixed at all tomographic time periods of the same patient.

Fig 1
The coronal section in CBCT. The ML point is located in the middle of the distance between the right and left spinous foramen.

In the sagittal window, the distance between ANS and PNS was divided into 4 equal parts, creating 5 reference points. The first reference point, exactly in the ANS, was removed because it was outside the nasal fossa area, which did not justify its measurement, and the remaining 4 points were called P2, P3, P4, and PNS. The measurement from the posterior ML point to the PNS was also standardized to become constant on all computed tomography (CT) scans of the same patient ( Fig 2 ). Then, in the axial tomographic window, the 4 points of division of the maxilla were individually adjusted in the nasal septum region, so that they were located exactly in the central region of the septum in its entire extension as shown in Figure 3 .

Fig 2
The sagittal section in CBCT. Reference points in the maxilla (P2, P3, P4, and PNS), distance from the reference line ML to the maxillary height PML, and the distance from PML to the PNS. PML, posterior midline.

Fig 3
The axial section in CBCT. The 4 reference points of the maxillary division were adjusted to lie exactly in the central region of the nasal septum.

After the references of the coronal and axial tomographic windows, a measure coinciding with or superiorly to the ML point was chosen, in which the visualization of the bilateral zygomatic arch was complete, allowing it to be used to project the lowest points of the nasal septum (P2, P3, P4, and PNS). This reference point was called the zygomatic arch ML (ZML), and this was also standardized on all subsequent CT scans ( Fig 4 ).

Jan 30, 2021 | Posted by in Orthodontics | Comments Off on Linear analysis of the nasal septum in patients treated with surgically assisted rapid maxillary expansion
Premium Wordpress Themes by UFO Themes