Zygomatic Arch Research Articles

Advancements in Temporomandibular Joint Arthroscopy: Refinements in Surgical Techniques for Treating the Superior Joint Spaces.

This study introduces a novel technique for arthroscopic surgery of the temporomandibular joint (TMJ), developed by the first author. Traditional TMJ arthroscopy techniques typically utilize a reference plane extending from the lateral canthus to the tragus, which may misalign with the zygomatic arch and create technical challenges during percutaneous joint access. The proposed method addresses these limitations by leveraging coronal and sagittal tomographic measurements alongside 3-dimensional reconstructions to determine precise and anatomically appropriate entry points. The inclusion of a 3-port video arthroscopy system enhances intraoperative visualization and access to the superior joint spaces. Compared with conventional techniques, this refined method demonstrates increased procedural efficiency, improved safety, simplified technical execution, and enhanced reproducibility. Detailed procedural steps are presented, supplemented with illustrative diagrams to ensure clarity and replicability. This innovative approach significantly advances surgical maneuverability, allowing for a comprehensive assessment and treatment of the glenoid fossa, condyle, and articular disc while minimizing the risk of iatrogenic complications often associated with traditional techniques.

The origin and evolution of shrews (Soricidae, Mammalia).

Shrews are among the most speciose of mammalian clades, but their evolutionary history is poorly understood. Their fossil record is fragmentary and even the anatomy of living groups is not well documented. Here, we incorporate the oldest, most complete fossil shrew yet known into the first phylogenetic analysis of the group to include molecular, morphological and temporal data. Our study reveals previously unknown diversity among total- and crown-group soricids. This includes a novel element of the mammalian skeleton: a robust, needle-like sesamoid extending cranially from the second thoracic neural arch in Myosoricini, comparable in length to these species' humeri. Additionally, 'red-toothed' shrews have an unusually elongate basicranium, and 'white-toothed' shrews probably evolved from a common ancestor with dental pigmentation. The fossil Domnina and crown soricids have a double-jaw articulation and incomplete zygomatic arch, but unlike nearly all crown species, Domnina has open vomeronasal canals and a tympanic process of the basisphenoid. Domnina and other heterosoricids are phylogenetically outside crown Soricidae. The oldest, well-supported total-group soricoids are North American, not Asian, and Soricidae probably originated during the Palaeocene or early Eocene. The diverse mammalian genus Crocidura originated and began to diversify during the Miocene.

Temporal Incision Super-high Superficial Musculoaponeurotic System Face Lift for Chinese Patients.

This investigation assessed patient satisfaction with a temporal incision technique using a super-high superficial musculoaponeurotic system (SMAS) flap for midface lifting in a Chinese patient cohort. From July 2019 to July 2023, 95 patients underwent midface lifts via a temporal incision approach at our institution. The extent of SMAS flap dissection spanned 2 cm above the outer canthus, to the lower margin of the zygomatic arch inferiorly, and medially to the zygomaticus major muscle. The technique involved anchoring the elevated SMAS flap to the deep temporal fascia to elevate the malar fat pads, correct sagging tissues, and ameliorate the appearance of nasolabial folds. Among the 95 patients, 61 completed a follow-up ranging from 6 months to 2 years postsurgery, with a majority reporting satisfaction with the aesthetic results of their midface lift. No significant complications, including permanent facial nerve injury, were reported. The temporal incision super-high SMAS face lift technique demonstrated high patient satisfaction and clinical effectiveness in improving the appearance of nasolabial fold and midface aesthetics. However, the success of this technique hinges on a comprehensive understanding of facial anatomy due to the confined operative field, highlighting its technical demands and the need for surgical expertise.

Impact of COVID-19 on Maxillofacial Trauma Incidence at Vajira Hospital: A Retrospective Study (2018-2021)

Background: Maxillofacial injuries vary globally depending on social, cultural, and environmental factors. The coronavirus disease 2019 (COVID-19) pandemic has further contributed to global variations in maxillofacial injury incidence owing to precautionary restrictions. Objective: To investigate the impact of COVID-19 on maxillofacial fractures. Materials and Methods: The present study was a retrospective cohort study that analyzed the medical records of patients with maxillofacial fractures admitted to the Emergency Department, Vajira Hospital, Bangkok. The incidence, causes, and anatomical sites of fractures were compared between the pre-COVID-19, 2018 to 2019, and COVID-19 periods, in 2020 to 2021. Results: The present study included 749 patients with maxillofacial fractures. The analysis revealed a 15% decrease in the number of patients with maxillofacial fractures during the COVID-19 pandemic. Males were more affected than females in both periods. Traffic accidents remained the primary cause of injuries, while assault-related injuries decreased significantly. Nasal bone fractures were the most frequent, with a significant reduction in orbital fractures caused by assault (p=0.033) during the COVID-19 period. The incidence of isolated zygomatic arch and panfacial fractures caused by assault increased during the COVID-19 period (p=0.026 and 0.041, respectively). The incidence of mandibular fractures due to other causes was significantly higher (p=0.009). Conclusion: The COVID-19 pandemic had led to significant changes in daily life in Thailand. Understanding the characteristics of patients with maxillofacial trauma provides valuable insights into prevention and management strategies, particularly during prolonged infectious disease outbreaks such as COVID-19 and potential future incidents.

Zygomatic arch three-dimensional morphology of capuchin monkeys of the genus Cebus

The zygomatic arch is an anatomical structure present in humans and monkey species. This study evaluated the three-dimensional morphology of the zygomatic arch of Cebus monkeys through microcomputed tomography scans. 13 dry skulls of Cebus apella from Southeastern Brazil were examined, 6 male and 7 female. The images were segmented in Mimics 18.0 (Materialise, NV, Belgium) software. Measurements were performed in Rhinoceros 5.0 (McNeel & Associates, Seattle, USA). With the transversal measurements, the zygomatic arch was classified as cylindrical (C), elliptical (E) or blade-like (Bl). Statistical analysis was performed by GraphPAD Prism v.8 software (San Diego, CA, USA) to compare measurements with types and sex. The Two-way ANOVA test with multiple comparisons using the Sidak test was employed to verify the relationship between sexes and types. The significance level was 5%. In males, there was an incidence on the left side of 25% of type E and 25% of type Bl and on the right side of 33% of type E and 17% of type Bl. In females, there was an incidence on the left side of 14% of type E and 36% of type Bl, and on the right side of 14% of type E and 36% of type Bl. The behavior of Cebus apella and its oral habits involving masticatory muscles may be related to the different shapes of the zygomatic arch found, as they have a direct relationship with this cranium structure.

Anatomical Measurements of the Malar Bone for Safe Zygomatic Implant Placement: A Study on Donated Bodies.

Background: The malar bone provides an anchorage point for zygomatic implants, avoiding invasive reconstructive surgeries in the fixed rehabilitation of fully edentulous and severely atrophic maxillae. The limited bone volume, however, requires precise implant placement to prevent complications related to nearby anatomical structures. This observational cross-sectional study aims to measure the malar and zygomatic arch bones and their distances from critical anatomical landmarks to guide surgeons in safe zygomatic implant placement. Methods: Dissections were performed bilaterally on 29 heads from human donated bodies in a cross-sectional observational study. Key landmarks evaluated include the infraorbital foramen (IF), pyriform nasal aperture (PNA), infraorbital margin (IM), zygomaticofacial foramen (ZFF), anterior end (A), and the most protruding point of the zygomatic arch (B). Measurements included IF-PNA, IF-IM, IF-ZFF, ZFF-IM, A-B, and orbital floor depth (OFD). Results: Significant findings showed IF-PNA was greater in males (18.66 ± 2.63 mm, p = 0.001), and IF-ZFF varied between sides (26.72 ± 8.7 mm, p = 0.002). ZFF-IM was larger in males (7.43 ± 2.09 mm, p < 0.001). Heights and thicknesses were also assessed, with significant side differences observed. Conclusions: These findings underscore the importance of understanding precise anatomical distances for successful implant placement. The study provides essential data to enhance surgical planning and training, ensuring safer procedures and minimizing the risk of complications.

Parosteal osteosarcoma in a cat treated by caudal maxillectomy and zygomectomy

AbstractA 13‐year‐old European cat was presented for evaluation of a sessile, non‐painful mass in the right zygomatic arch that had been slowly progressing over a 1‐year period. Initial histological analysis of a bone biopsy, conducted by the referring veterinarian, yielded inconclusive results, and a second incisional biopsy was interpreted as an osteoproliferative lesion suggestive of low‐grade osteosarcoma. Caudal maxillectomy and zygomectomy were performed. Subsequent histopathological examination confirmed the presence of parosteal osteosarcoma. This neoplasm, while uncommon in feline and canine populations, remains poorly documented in existing literature.

Development of an implantable sensor system for in vivo strain, temperature, and pH monitoring: comparative evaluation of titanium and resorbable magnesium plates

Biodegradable magnesium is a highly desired material for fracture fixation implants because of its good mechanical properties and ability to completely dissolve in the body over time, eliminating the need for a secondary surgery to remove the implant. Despite extensive research on these materials, there remains a dearth of information regarding critical factors that affect implant performance in clinical applications, such as the in vivo pH and mechanical loading conditions. We developed a measurement system with implantable strain, temperature, pH and motion sensors to characterize magnesium and titanium plates, fixating bilateral zygomatic arch osteotomies in three Swiss alpine sheep for eight weeks. pH 1–2 mm above titanium plates was 6.6 ± 0.4, while for magnesium plates it was slightly elevated to 7.4 ± 0.8. Strains on magnesium plates were higher than on titanium plates, possibly due to the lower Young's modulus of magnesium. One magnesium plate experienced excessive loading, which led to plate failure within 31 h. This is, to our knowledge, the first in vivo strain, temperature, and pH data recorded for magnesium implants used for fracture fixation. These results provide insight into magnesium degradation and its influence on the in vivo environment, and may help to improve material and implant design for future clinical applications.

Evaluation of the Effect of Pre-bent Z-shaped Titanium Plate on Narrowing of Zygomatic Arch in L-shaped Reduction Malarplasty

Objective: Pre-bent titanium plates are widely used for internal fixation in L-shaped zygomatic reduction. The aim is to evaluate the effect of pre-bent Z-shaped titanium plate on the narrowing of the zygomatic arch in L-shaped reduction malarplasty. Methods: Thirty cosmetic female patients were selected and scanned using computed tomography (CT). The CT images of pre-operation (T1) and post-operation(T2) were re-established through MIMICS26.0 (Materialise). After the 2 images were registered based on the skull base, the narrowing distance (ZRN) at the posterior end of the free zygomatic arch, as well as the preoperative and postoperative cross-sectional dimensions of the zygomatic arch, were measured. The ZRN and the altitude of the pre-bent titanium plate (TA) were compared using an independent t test, and their correlation was also analyzed using the Pearson coefficient. The preoperative and postoperative longest diameter (L1) and shortest diameter (L2) of the posterior zygomatic arch were compared using a paired t test. Results: The TA was 3.80±0.82 mm and the ZRN was 3.21±0.82 mm. The difference value was 0.59±0.41 mm, which was statistically significant. TA showed a strong correlation with ZRN (r=0.916, P=0.002). The L1 and L2 of the zygomatic arch root were slightly reduced postoperatively. Conclusion: The pre-bent Z-shaped titanium plate does not completely correspond to the zygomatic arch narrowing distance in the actual application of L-shaped reduction malarplasty. However, it can control the narrowing distance of the zygomatic arch predictably, and achieve satisfactory surgical outcomes.

Anthropological and forensic significance of facial soft tissue thickness in Montenegrin population

A lack of soft tissue leads to difficulties in facial reconstruction and further identification in the absence of DNA (deoxyribonucleic acid), finger print and dental data. If these data are not available, then identification based on facial soft tissue thickness (FSTT) is the next reliable method. There is no data in the literature about facial soft tissue thickness in Montenegrin population. Once the measurement is performed, a software algorithm based on the multidetector computerized tomography (MDCT) imaged bone structures and use of FSTT would be able to provide a useful picture of the face for identification purposes. This prospective research was performed by MDCT head examinations of 83 adults aged 18–85, living in Montenegro. The FSTT was measured at eight central points (glabella (GL), nasion (NA), rhinion (RHI), mid-philtrum (MID), upper lip (UL), lower lip (LL), mental eminence (ME), and the point beneath the chin (BC)), and five bilateral points (frontal tubers (FT), supraorbital (SO), external orbital marginal point (EX), zygomatic arch (ZY), and middle masseter (MST)). It was observed that the points RHI, MID, UL, LL, ME, FT, SO and MST are thicker in men compared to women. With an increase in BMI, FSTT in the central points also increases, as well as bilaterally at the ZY, FT, SO and MST points. With aging, there is an increase of the thickness of the FSTT at the RHI and bilaterally at the EX and ZY, while at the MID, LL and MST, the thickness decreases with aging, in both sexes.

Temporal Augmentation Effect of Reduction Malarplasty: Application of our Bracing Technique with Zygomatic Arch Elevation.

A broad midface is usually accompanied by temporal depression. Traditional reduction malarplasty may visually improve the temporal depression by the inward reduction of zygomatic arch, but also has a high risk of soft tissue sagging. Our bracing technique has been reported to have an anti-sagging effect and may have a temporal augmentation effect as observed during our long-term clinical practice. Data of patients who received reduction malarplasty with our bracing technique from September 2015 to July 2023 were retrospectively collected. The pre-op and post-op CT images of those who met the inclusion criteria were used for three-dimensional reconstruction and measurements of the thickness and volume of the temporal soft tissue as well as the elevation distance of zygomatic arch. Fifty-eight patients with an average follow-up of 18.4 ± 9.1months were included. Despite mild thinning of the temporalis muscle after reduction malarplasty, the overall thickness of the temporal soft tissue significantly increased due to the significant thickening of the temporal adipose-fascial layer. There was a 0.5ml-increase in the temporal volume although without statistical difference. No significant correlation was detected between the elevation distance of zygomatic arch and the temporal thickness or volume change. The bracing technique of reduction malarplasty not only plays an anti-sagging role, but also has a temporal augmentation effect through the superior bracing by the elevation and rigid fixation of the zygomatic arch. It adds brilliance to the traditional technique and can be suggested especially when the patients are disturbed by temporal depression. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Long-term Follow-up of Secondary Reconstruction of Facial Paralysis and Depressive Deformities After Subtotal Temporal Bone Resection.

Subtotal temporal bone resection (STBR) frequently results in facial paralysis and depression, making reconstruction challenging due to significant tissue loss. This study aimed to evaluate the effectiveness of a procedure designed for simultaneous smile and soft tissue reconstruction after STBR. The authors included 3 patients who underwent latissimus dorsi (LD) neuromuscular flap combined with adipose flap transfer after STBR at the Tokyo Medical and Dental University Hospital between 2010 and 2016. Among these patients, 2 had facial vessels unsuitable for anastomosis due to prior neck dissection, and their masseteric nerves were unavailable for neurorrhaphy due to STBR. The thoracodorsal nerve was coaptated to the contralateral facial nerve in all patients and to the ipsilateral masseter nerve in one patient. Follow-up periods ranged from 7 to 13 years, with all patients achieving spontaneous smiles within 12 months post-surgery. Although depressive deformities improved, long-term follow-up revealed buccal muscle bulging due to unstable LD muscle fixation from a zygomatic arch defect caused by STBR. Revision surgeries, including muscle refixation with a tensor fasciae lata graft, muscle reduction, eyebrow lifting, blepharoplasty, and adipose tissue repositioning, were performed as needed. Ultimately, all patients achieved satisfactory facial contours and spontaneous smiles. This study demonstrates that free LD muscle with adipose flap transfer is effective for post-STBR reconstruction. However, detailed surgical planning and multistage reconstruction are often necessary due to the complexities involved.

Использование имплантатов из пористого никелида титана в замещении тотальных дефектов скуловой кости и дуги

Summary. The aim of the study is to increase the efficiency of total replacement of the zygomatic bone and arch by developing a new medical technology using shape memory materials. Materials and methods of the study. Research materials – technologies using shape memory materials. Research method – development of an endoprosthesis of the zygomatic bone and arch. Research results and their analysis. Analysis of the research results showed: – the use of endoprostheses made of porous titanium nickelide in accordance with the anatomical features of the affected organ makes it possible to fully restore the lost anatomical and functional capabilities of the facial skull; – coating the endoprosthesis frame with textile titanium nickelide, in addition to improving the conditions for the interaction of the implant with the recipient tissues, allows to fully compensate for the insufficiency of the soft tissue component of the face; – fixing structures with a shape memory effect are easy to use, do not require significant time costs and provide stable fixation of the endoprosthesis with bone structures.

Modified Dautrey's Procedure for Recurrent Temporomandibular Joint Dislocation.

This study introduced and analyzed the clinical effects of a modified Dautrey's procedure, involving down-fracture of the zygomatic arch and articular tubercle augmentation, for the treatment of recurrent TMJ dislocation. Recurrent TMJ dislocation patients were treated using the modified Dautrey's procedure. The recurrence of joint dislocation, maximal mouth opening (MMO), and pain were evaluated postoperatively. A total of 7 patients were treated using the modified procedure, with no instances of facial nerve injury. No recurrences occurred during the follow-up period of 0.5 to 5 years. The average MMO was 35.4mm and 35.7mm before the operation and during follow-up, respectively. The modified Dautrey's procedure was effective and particularly suitable for elderly patients with abnormal muscle control, resulting in low recurrence.

The experience of chronic protracted mandibular dislocation treatment: manual vs. surgical reduction

Temporomandibular joint dislocation is a common challenge in dental care, but it can be promptly addressed through manual realignment, making it standard procedure in the realm of oral health. Nonetheless, effectively preventing and treating chronic protracted mandibular dislocation (CPMD), characterized by prolonged dislocation, remains a significant challenge. Hence, a retrospective analysis was conducted on the clinical data of 10 patients diagnosed with chronic protracted mandibular dislocation (CPMD), encompassing diagnosis, treatment, and prognosis details. CPMD tends to be more prevalent among the elderly population, with an average age of 67.2±11.9 years and a male-to-female ratio of 1:9. All diagnosed patients presented with bilateral anterior dislocation, each requiring diverse pre-treatment approaches. The most significant risk factor contributing to CPMD was unconsciousness resulting from nervous system injury, which delayed the perception of symptoms associated with temporomandibular joint dislocation. 90% of CPMD patients experienced successful treatment through manual reduction, while a refractory CPMD cohort, resistant to manual reduction, necessitated surgical intervention for resolution. All patients underwent treatment involving elastic intermaxillary traction, which served as the primary means of achieving reduction. Subsequent analysis of CT data revealed that condylar displacement beyond the zygomatic arch served as an indication for surgical reduction. Consequently, manual reduction under general anesthesia combined with elastic intermaxillary traction proved effective for managing CPMD cases. However, cases displaying excessive vertical displacement beyond the zygomatic arch should be considered for surgical intervention based on CT findings.

Aesthetic Approaches to Zygomatic Fracture Management: Achieving Optimal Outcomes With Minimal Scarring.

The zygomaticomaxillary complex is integral to facial aesthetics and is frequently involved in facial fractures. These injuries often necessitate surgical intervention, with open reduction and internal fixation being the standard treatment. This article presents a novel philosophy for managing zygomatic fractures, emphasizing the "Scarless Surgery" technique. The authors' approach prioritizes minimal osteosynthesis material and fixation points while utilizing the least visible surgical access. For isolated zygomatic arch fractures, an intraoral technique is preferred, whereas the frontozygomatic suture is approached through an upper eyelid crease for optimal aesthetic outcomes. The zygomaticomaxillary buttress is accessed through a vestibular mucosal incision and the infraorbital rim benefits from a transconjunctival approach. The findings suggest that fewer fixation points can still yield satisfactory stability and cosmetic results, aligning with literature supporting the efficacy of 1 and 2-point fixations. This modern technique not only minimizes visible scarring but also conforms to the contemporary push for minimally invasive surgical methods. The authors' experience and the existing literature support the efficacy of this approach, reinforcing its viability as a standard practice in the surgical management of facial trauma.

Two-step cluster analysis based on three-dimensional CT measurements of craniofacial structures in severe craniofacial microsomia

BackgroundThe Pruzansky-Kaban and OMENS classifications do not provide additional details on temporomandibular joint deformities. The aim of this study was to classify and quantitatively delineate severe forms of craniofacial microsomia based on three-dimensional maxillofacial measurements, focusing on deformities in the zygomatic, temporal, and mandibular bones. MethodsMaxillofacial computed tomography(CT) scans of children with severe types of CFM from 2010 to 2020 were collected. Three-dimensional measurements of zygomatic arch length, height of mandibular ramus, height of maxilla, and occlusal cant were performed. Two-step cluster analysis was conducted based on zygomatic arch continuity, occlusal cant, the ratio of affected side to unaffected side(A/U ratio) for zygomatic arch length, mandibular ramus height, and maxillary height. ResultsFifty patients (32 male, 18 female) were included in the study. They were classified into 2 clusters through cluster analysis. Cluster 1 comprised subjects (44% of patients) with continuous zygomatic arches. Cluster 2 comprised subjects (39%) with discontinuous zygomatic arches. The zygomatic arch A/U ratio in Cluster 1 was greater than that in Cluster 2, with statistical significance observed. Additionally, the maxilla height A/U ratio in Cluster 1 was lower than in Cluster 2, also with statistical significance. There was no statistically significant difference observed in the ramus height A/U ratio and occlusal cant between Cluster 1 and Cluster 2. ConclusionsBased on craniofacial measurements, severe CFM can be categorized into two types: continuous zygomatic arch and discontinuous zygomatic arch. This cluster analysis complemented the OMENS classification and could assist in the selection and design of prosthetic joints for patients with CFM.

The impact of breastfeeding on facial appearance in adolescent children.

Evidence that breastfeeding impacts the facial features of children is conflicting. Most studies to date have focused on dental and skeletal malocclusion. It currently remains unclear whether such effects are of sufficient magnitude to be detectable on outward facial appearance. Here, we evaluate the extent to which maternally reported breastfeeding is associated with 3D facial shape in a large adolescent cohort. After extracting 3D facial surfaces from MR scans in 2275 9- and 10-year-old children and aligning the surfaces in dense correspondence, we analyzed the effect of breastfeeding on shape as a dichotomous (no/yes) and semi-quantitative (to assess duration in months) variable using partial least squares regression. Our results showed no effect (p = 0.532) when breastfeeding was dichotomized. However, when treated as a semi-quantitative variable, breastfeeding duration was associated with statistically significant changes in shape (p = 3.61x 10-4). The most prominent facial changes included relative retrusion of the central midface, zygomatic arches, and orbital regions along with relative protrusion of forehead, cheek, and mandible. The net effect was that as breastfeeding duration increased, the facial profile in children became flatter (less convex). The observed effects on the face, however, were subtle and likely not conspicuous enough to be noticed by most observers. This was true even when comparing the faces of children breastfed for 19-24 months to children with no reported breastfeeding. Thus, breastfeeding does appear to have detectable effect on outward facial appearance in adolescent children, but its practical impact appears to be minimal.

Head and Neck Airbag Penetrating Injuries.

Airbags have significantly decreased fatalities in frontal vehicle accidents, but their deployment can lead to more severe injuries and rarely death. The authors present a case of a penetrating injury causing tissue loss in the left cheek, an "explosion" of the zygomatic arch, and facial nerve damage, discussing the management in the contest of literature examining similar injuries in the head and neck region. Reviewing English literature from 1995 to 2023, 9 patients experienced severe airbag-related penetrating head and neck injuries, in 3 cases resulting in death. In addition, we describe the case of a young male reporting a deep cheek laceration with facial nerve damage, tissue loss, and comminuted maxilla-zygomatic fracture; 48 hours after trauma, he underwent surgical reconstruction using a bilobed flap, direct suture of the resected masseter muscle, closed reduction of the comminuted zygomatic arch fracture, and direct neurorrhaphy of the lacerated facial nerve. Five months after surgery, facial nerve function recovery was observed. Mouth opening was restored, but a mixed low-medium hearing loss persisted for high frequencies. In another case marginal nerve damage was reported, but management is not described. The use of seat belts and airbags has led to a significant reduction in the incidence of facial fractures and fatalities after motor vehicle accidents, but at the same time, in some cases, complex facial trauma and/or penetrating injury can be observed. In case of suspected or certain facial nerve damage, it is mandatory to perform exploration and eventual reconstruction within 72 hours.

Noise exposure of the inner ear during robotic drilling.

Preserving the cochlear structures and thus hearing preservation, has become a prominent topic of discussion in cochlear implant (CI) surgery. Various approaches and soft surgical techniques have been described when approaching the inner ear. Robot-assisted cochlear implant surgery (RACIS) reaches the round window in a minimally invasive manner by following a trajectory of minimal trauma. This involves the drilling of a keyhole trajectory to the round window, through the facial recess, with no need for a complete mastoidectomy. It involves less drilling, less drilling time and less structural damage. A lot of attention has been paid to the structural traumatic causes of hearing loss but acoustic trauma during the exposure of the inner ear appears to be neglected topic. The aim was to measure the noise exposure of the inner ear during the robotic drilling of the mastoid and bony overhang of the round window. The results were compared with the milling in conventional cochlear implantation surgery. RACIS on fresh frozen human cadavers. The equivalent frequency-weighted and time-averaged sound pressure level LAF in dB and the noise dose in % derived from a noise damage model, both obtained during RACIS. The robotic drilling of 6 trajectories towards the inner ear were performed, including 4 trajectories through round window access and 2 trajectories through cochleostomy. The results were compared with the data of 7 cases of conventional CI surgery that have been described in literature. The induced equivalent sound pressure level LAF was determined via an accelleration sensor at the zygomatic arch and a calibration according to bone conduction audiometry. A noise dose for the whole procedure was calculated from the equivalent sound pressure level LAF and the exposure time using a noise damage model. A noise dose of 100% is considered a critical exposure limit and values above are considered potentially harmful, with the risk of hearing impairment. The maximum LAF was 82 dB during fiducial screw placement; 87 dB during middle ear access; 95 dB for the accesses through the round window and 88 dB for the accesses through cochleostomy. The noise dose due to the HEARO®-procedure was always far below the critical value of 100%. There was no acoustic trauma of the inner ear in all cases with the noise dose being smaller than 0.1% in five out of the six cases. The maximum LAF in the seven cases of conventional CI surgery was 118 dB with a maximum cumulative noise dose of 172.6%. The critical exposure limit of 100% was exceeded in three cases of conventional CI surgery. RACIS provokes significantly less acoustic trauma than conventional mastoid surgery in our findings. There were no observable differences in noise exposure levels between a cochleostomy or a round window approach where the bony overhang needed to be drilled.