Anatomic evaluation of the posterior superior alveolar artery using cone-beam computed tomography: A systematic review and meta-analysis

Maxillary posterior bone deficiency presents a considerable challenge in dental implant surgery. The presence of atrophic bones and the pneumatization of the sinus necessitate reconstruction of the posterior maxilla for the placement of dental implants.1 Sinus augmentation is a highly predictable and safe method for increasing bone height prior to dental implant placement.2

Surgeons should remain cognizant of the potential intraoperative and postoperative complications associated with sinus augmentation. The most common intraoperative complication during sinus floor elevation is perforation of the Schneiderian membrane.3, 4 Additionally, trauma to a blood vessel is a frequent complication that can result in severe hemorrhage.5

The vascularization of the maxillary sinus is derived from the infraorbital artery, the greater palatine artery, and the posterior superior alveolar artery (PSAA).6, 7 An osteotomy procedure on the sinus lateral wall could potentially compromise the integrity of the PSAA.8 Therefore, understanding the blood supply of the maxillary sinus is crucial to avoid complications during sinus floor elevation surgery. These include excessive bleeding, Schneiderian membrane perforation, and bone necrosis.7

Cone-beam computed tomography (CBCT) is a valuable diagnostic tool commonly utilized in the field of dentistry, particularly for dental implant placement and sinus elevation procedures. CBCT images provide useful information regarding bone morphology, bone diseases, and the positioning of key anatomical landmarks such as the PSAA.9 Moreover, this tomographic technique is advantageous due to its cost-effectiveness, reduced scan time, higher resolution and lower radiation dose for patients compared to medical computed tomography (CT).10

A thorough, advanced diagnosis is crucial for anticipating and mitigating complications prior to treatment. To these authors’ knowledge, no new systematic review has been conducted on the characteristics of the PSAA since 2015.11 However, numerous original articles have been published during this period.12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36 These studies have revealed a broad range of detection rates for this artery using CBCT.12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36 For instance, in the Iranian population, the detection rate varies between 25%27 and 93%.25 The detection rate of this artery in the Turkish population ranges from 72.2%34 to 90%.1 In another study, the detection rate was found to be 24.5% in a Taiwanese population.35 Additionally, other anatomical characteristics such as artery diameter and location have been overlooked in previous reviews.11 Therefore, this systematic review was conducted to examine the detection rate of the PSAA, the diameter of this artery, and its various anatomical characteristics on CBCT images.

The study received approval from the ethics committee of Tabriz University of Medical Sciences under the Vice Chancellor for Research (Ethics Code: IR.TBZMED.VCR.REC.1400.182). This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.37

Cross-sectional and prevalence studies with full texts written in English were considered. Among these, articles investigating at least 1 characteristic of the PSAA using CBCT were included. All animal studies, abstracts, unpublished articles, reviews, studies conducted on cadavers or patients with systemic diseases that could impact bone metabolism, and studies of patients with anatomic abnormalities or a history of maxillary trauma were excluded. Studies that utilized medical CT, for assessment of the artery were also excluded. The literature search, which had no restrictions on publication date, was conducted until May 16, 2022 across the Web of Science, Medline, Scopus, and Embase electronic databases. Google Scholar was additionally searched for gray literature.38 Medical Subject Headings and related keywords used in the search included “posterior superior alveolar artery,” “PSAA,” “sinus lift,” “maxillary sinus,” “cone-beam computed tomography,” “CBCT,” and “dental implants,” including all subheadings. In addition, the references of selected citations, previous reviews on the same topic, and 2 major textbooks39, 40 were hand-searched. When articles contained incomplete data, emails were sent to the corresponding authors.

Two authors (F.R. and M.B.) independently screened studies for inclusion based on the titles and abstracts. Studies that did not meet the eligibility criteria were excluded. Full-text reading was conducted only when the title and abstract were unclear, or when consensus could not be reached. During these full-text readings, the studies were thoroughly evaluated against the eligibility criteria. Any disagreements that arose after the full-text reading were resolved through consultation with a third author (M.F.). Data from the included studies were independently extracted by 2 authors (F.R. and M.B.) using a pilot data extraction form and consolidated into a Microsoft Word file (ver. 2010, Microsoft Corp., Redmond, WA, USA). The extracted information included the author(s), year, country, study type, sample size, study population, and outcomes regarding various characteristics of the PSAA. In the event of any discrepancy, a third author (M.F.) was consulted. The investigation focused on 5 characteristics of the PSAA: detection rate, diameter, location, and the mean distances of the PSAA from the alveolar crest and sinus floor. Artery detection was defined as identification of the PSAA along the lateral wall of the maxillary sinus using coronal-axial or sagittal CBCT views. The diameter of the PSAA was defined as the maximum distance between the inner sides of the cortical borders. The location of the artery was classified into 3 categories based on a study by Ilgüy et al.:41 intraosseous (IO; inside the lateral wall), intrasinus (IS; below the membrane, between the sinus membrane and the osseous wall), and superficial (SF; extraosseous, on the outer cortex of the lateral sinus wall). The distances from the inferior border of the PSAA to the alveolar crest and sinus floor were measured by the authors of the studies.

The quality of the articles was assessed using a 5-item binary scale (yes or no) developed by Varela-Centelles et al.11 This scale was based on the Strengthening the Reporting of Observational Studies in Epidemiology guidelines for reporting observational studies. The 5 items were: 1) Does the report provide details about the study participants? 2) Are the aim and outcome of the study clearly defined? 3) Is the sampling frame a true or close representation of the target population? 4) Is the measuring instrument adequately described? and 5) Does the report offer a cautious overall interpretation of the results? Two investigators (F.R. and M.B.) independently graded the quality score in consultation with a third author (M.F.). Based on the overall score, articles were categorized into 3 quality groups: low (0 to 2), moderate (3 or 4), and high (5).

The detection rate, location, and classified diameter of the PSAA were estimated as prevalence values with associated 95% confidence intervals (CIs). The diameter of the PSAA and its distance from the alveolar crest and sinus floor were determined as means, again with corresponding 95% CIs.

For each characteristic, studies were enrolled in the meta-analysis if they reported the mean amount for the sinus unit. Specifically, for diameter classification, only studies utilizing the classification system of Mardinger et al.42 were enrolled. This system categorizes diameters into 3 groups: less than 1 mm, between 1 and 2 mm, and greater than 2 mm. Regarding location, studies using the classification scheme of Ilgüy et al. were included in the meta-analysis.41 Finally, the data from the included studies were entered into a standardized MS Excel spreadsheet (version 2010; Microsoft Corp.).

The meta-analysis was conducted, and forest plots were generated using Comprehensive Meta-Analysis (CMA) version 2.2.064 (Biostat Inc., Englewood, NJ, USA). Meta-regression, facilitated by CMA, was employed to identify the factors contributing to any observed heterogeneity.

Heterogeneity was assessed using the Cochran Q test and the I² statistic. Heterogeneity was considered significant if the I² value was at least 40% and/or if the P-value was less than 0.1.

Pooled prevalence estimates of the detection rate, location, and classified diameter of the PSAA were calculated. Additionally, pooled mean estimates were calculated regarding the diameter of the PSAA and its distance from the alveolar crest and sinus floor. These values were presented with 95% CIs, and calculations were made using either fixed or random effects models, based on the level of heterogeneity. If significant heterogeneity was detected, a random-effects model was applied; otherwise, a fixed-effects model was used. Given the descriptive nature of this systematic review, publication bias was not a relevant factor.

This study was conducted to assess various anatomical characteristics of the PSAA as seen on CBCT images. A previous review indicated that preoperative evaluation using CBCT facilitates more frequent and effective identification of the PSAA compared to medical CT;11 hence, studies utilizing CBCT were incorporated into this research. According to this meta-analysis, the detection rate of the PSAA via CBCT was 79%. In comparison, Varela-Centelles et al. reported a 78.12% detection rate of the PSAA via CBCT.11 This discrepancy could be due to the publication of new studies since 2015.12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36 Notably, however, this artery is present in all sinuses, as confirmed by multiple cadaveric studies.7, 71, 72 The inability to detect the vessel can be attributed to several factors. First, some studies suggest that a PSAA with a diameter of less than 0.5 mm may not be detectable by CBCT.10, 12, 15, 42, 45, 51, 71 Second, the path of the artery may not be consistent through the lateral wall of the maxillary sinus. The artery may be located in an extra-bony or completely intrasinus position in areas examined by the operator. The absence of arteries on radiographs could be due to the limited capacity of CBCT to discern soft tissues.44, 54 Third, variations in methodologies and operator experience could lead to a lower detection rate relative to cadaveric studies.27, 32 Differences in image resolution, voxel size, and the use of more advanced software for analysis have been cited in previous studies as reasons for the lower detection rate of the PSAA.15, 61

Understanding the diameter of this artery is imperative for evaluating the risk of excessive bleeding. Managing complications becomes more complex and potentially alarming with arteries of larger diameters.61 In this study, the mean diameter of the PSAA was 1.06±0.05 mm, with a range of 0.54–1.42 mm. To provide clinicians better insight into the diameter of the artery, a classification analysis was performed. This revealed that 55% of the arteries were <1 mm in diameter, while only 2% were >2 mm in diameter. Comparing the mean artery diameter obtained through CBCT with the limited evidence from cadaver studies,7, 72 it may be challenging to conclude that CBCT imaging overlooks arteries with a diameter less than 0.5 mm. For this to be the case, the mean artery diameter in cadavers should be lower than the mean diameter found in the meta-analysis. Interestingly, the mean sample diameter reported by Solar et al.7 was even higher than the mean diameter in the present study. However, Hur et al.72 reported a mean diameter of the PSAA of 0.8±0.3. This suggests that further studies are required to obtain more accurate results. Reportedly, the risk of severe hemorrhage decreases in canals smaller than 1 mm. In this context, this carries little clinical significance, as any resulting hemorrhage can be readily managed.61, 62 However, a PSAA with a diameter greater than 2 mm can lead to excessive bleeding and non–life-threatening bleeding complications.52, 61 Considering the results of this study and the risks associated with artery diameter, only 2% of the arteries could potentially lead to serious complications. A review of the literature revealed inconsistencies in detection rates and diameters based on sex.10, 12, 13, 16, 17, 18, 20, 21, 24, 31, 33, 34, 41, 63, 68, 69 In the present study, both the detection rate and the artery diameter were significantly higher in male participants. Given the latter, extra caution is warranted when the patient is male.

In this review, most PSAAs were found in the IO location (64%); 30% of the arteries had IS placement, and the least common location of the PSAA was SF (5%). The arterial branch within the canal is often obscured by the thickness of the osseous wall during lateral window preparation, which heightens the risk of inadvertent injury to the arterial branch.10 The IS location of the PSAA should also be considered to avoid vascular injuries during membrane detachment.73

To prevent further complications in sinus lift surgery, practitioners must factor in the distances from the PSAA to the sinus floor and alveolar crest. Park et al.46 found that the distance between the PSAA and sinus floor ranged from 7.71–8.01 mm. They suggested that the window height should be at least 8 mm to ensure adequate visualization, straightforward instrumentation, and proper osseous graft placement. This implies that the risk of artery injury can be minimized if the surgeon positions the osteotomy site as low as possible on the sinus floor. The present review indicated that the mean distance between the sinus floor and the inferior border of the PSAA was 8.85±0.4 mm, indicating that the risk of vessel injury would be low if the window width did not exceed 8 mm. Based on the results of other studies, the bony window should be no more than 15 mm above the alveolar crest.10, 11, 42, 43, 48, 63 As a result, depending on the implant length, preparation of the lateral window closer to the alveolar crest should be considered.62 According to the meta-analysis, the mean distance of the PSAA from the alveolar crest was 16.71±0.49 mm. This suggests that the risk of cutting the artery during the procedure is decreased in most cases, given that a distance of 15 mm is considered safe. Overall, the distance between the alveolar crest and the PSAA significantly decreases when teeth are missing, primarily in fully edentulous patients, although this reduction is not statistically significant in partially edentulous patients.74 It is widely recognized that following tooth loss, alveolar bone resorption and maxillary sinus pneumatization occur concurrently, leading to maxillary sinus expansion.74, 75 The distance between the sinus floor and the PSAA is expected to increase after tooth extraction, regardless of the time elapsed between the extraction and the measurement. However, this shift in the location of the sinus floor is far smaller than the dimensional change in the alveolar crest. The maxillary sinus volume increases from birth until around 20 years of age, at which point the pneumatization stops, and the maxillary sinus reaches its final position.76 In studies10, 12, 13, 14, 15, 17, 18, 19, 20, 21, 23, 24, 25, 28, 30, 31, 32, 33, 35, 41, 62, 63, 64, 65, 66, 67, 68, 69 examining the distance from the artery to the alveolar crest, researchers may neglect to distinguish between edentulous and dentulous areas, resulting in imprecise interpretation due to the atrophic alveolar crest. Therefore, measurements are more reliable when evaluating the PSAA location using the sinus floor as a reference point. Furthermore, assessing the PSAA location in relation to the maxillary sinus floor is crucial when preparing the lateral window for a sinus lift, as it can help minimize bleeding complications.

The distance from the PSAA to both the sinus floor and the alveolar crest was found to be greater in male than in female patients. This difference was significant due to the larger craniofacial size in males.21

Excessive bleeding from the PSAA during sinus lift surgery can disrupt the clinician’s view61 and prolong the operation time.66 However, according to the results of this meta-analysis, life-threatening hemorrhage resulting from injury to the superior alveolar arteries is not a genuine clinical concern in surgical procedures involving the maxilla, such as sinus augmentation. Furthermore, preoperative CBCT is essential for preventing complications during surgery. The limited diameter of the injured arteries and reactive vasoconstriction will ultimately minimize blood loss. Moreover, experienced clinicians can easily manage bleeding in patients with normal blood hemostasis. Conversely, severe bleeding may compromise visibility for less experienced surgeons.6 Given the variability in the anatomical characteristics of the PSAA, relying solely on mean values is insufficient for making clinical decisions. That said, these mean measurements can provide clinicians with a better understanding of the PSAA. Variations in the study populations, CBCT machines, operators, and conditions of edentulism make it challenging to draw a definitive conclusion. The strength of the present study lies in its thorough investigation of PSAA characteristics and assessment of these characteristics based on sex. To reach a precise conclusion, it would be even better to analyze the anatomical characteristics based on the location of each tooth. Some studies14, 23 have examined PSAA characteristics based on tooth location, and further research is needed in this area. Future studies should also clearly state the populations investigated and the methods of measurement used, in accordance with quality assessment practices.

In conclusion, the mean distances of the PSAA from the alveolar crest and sinus floor, coupled with the small diameter of the artery, suggest a low risk of severe hemorrhage during the sinus floor lift procedure. Furthermore, preoperative CBCT is essential to prevent complications during surgery.