Cochlear implant positioning: development and validation of an automatic method using computed tomography image analysis

The aim of this study was to preoperatively asses the feasibility of drilling a bony recess for the fixation of a cochlear implant in the temporal bone. Even though complications are rare with cochlear implantations, drilling at the site of implantation have resulted in hematoma or cerebrospinal fluid leakage. Mainly in cases with a reduced temporal bone thickness, the risk for complications has increased, such as in paediatric patients.MethodsAn in-house designed semi-automatic algorithm was developed to analyse a 3D model of the skull. The feasibility of drilling the recess was determined by a gradient descent method to search for the thickest part of the temporal bone. Feasibility was determined by the residual bone thickness which was calculated after a simulated drilling of the recess at the thickest position. An initial validation of the algorithm was performed by measuring the accuracy of the algorithm on five 3D models with known thickest locations for the recess. The accuracy was determined by a part comparison between the known position and algorithm provided position.ResultsIn four of the five validation models a standard deviation for accuracy below the predetermined cut-off value of 4.2 mm was achieved between the actual thickest position and the position determined by the algorithm. Furthermore, the residual thickness calculated by the algorithm showed a high agreement (max. 0.02 mm difference) with the actual thickness.ConclusionWith the developed algorithm, a semi-automatic method was created to analyse the temporal bone thickness within a specified region of interest on the skull. Thereby, providing indications for surgical feasibility, potential risks for anatomical structures and impact on procedure time of cochlear implantation. This method could be a valuable research tool to objectively assess feasibility of drilling a recess in patients with thin temporal bones preoperatively

Variability in surgical techniques for cochlear implantation: an international survey study

Objective: This study aimed to gain insight into current practices regarding the surgical techniques used for positioning and fixation of internal components of the cochlear implant. Methods: A questionnaire focused on surgical techniques used for cochlear implantation was distributed among 441 cochlear implant surgeons. Descriptive statistics were reported. Results: The questionnaire was completed by 59 surgeons working in 13 different countries. The most preferred incision shapes were the S-shape (41%) and the C-shape (36%). The preferred implantation angle for the receiver/stimulator device was either 45° (64%) or 60° (30%), relative to the Frankfurter Horizontal Plane. Most respondents used a drilled bony well with (42%) or without a subperiosteal pocket (31%) to fixate the receiver/stimulator device. All respondents used the facial recess approach. Most used the round window insertion technique to enter the scala tympani (73%). Approximately half of the respondents preferred the lateral wall electrode array, whereas the other half preferred the perimodiolar electrode array. During their career, most (86%) changed their technique towards structure preservation and minimizing trauma. Conclusion: This study indicates variability in the surgical techniques used to position and fixate the internal components of the cochlear implant. Additionally, surgical preference transits towards structure preservation and minimal invasiveness

Cochlear Implant Fixation Techniques: A Systematic Review of the Literature

OBJECTIVE: Given the lack of consensus on fixation techniques of the cochlear implant, this review aims to create an up-to-date overview of intra- and postoperative complications, focusing on migration of the internal receiver/stimulator (R/S) device and the electrode array. DATA SOURCES: On June 29, 2020 we conducted a search in PubMed, Embase, Cochrane, Web of Science, and CINAHL. Keywords were "Cochlear implant," "complication," "migration," and synonyms. STUDY SELECTION: Studies were considered if: 1) the adult study population consisted of ≥ 10 patients, 2) the R/S device was fixated using the bony well or tight subperiostal pocket technique without bone-anchoring sutures or screws on the implant, and 3) migration of the R/S device or displacement of the electrode array were described as outcomes. DATA EXTRACTION: Study characteristics, interventions, follow-up, and outcomes were extracted. For critical appraisal, an adapted version of the Newcastle-Ottawa quality assessment scale for cohort studies was used. DATA SYNTHESIS: Seven studies were included (n = 430 patients). Migration of the R/S device was reported by three studies. Two studies applying the tight pocket technique reported migration rates ranging from 9.0 to 69.2%. One study using the bony bed technique reported migration of 100%, with an average of 2.5 mm. All studies lacked the required standard for comparability, assessment of outcome, and follow-up. CONCLUSIONS AND RELEVANCE: There is currently no evidence of a difference between the bony bed- and tight pocket fixation technique, regarding migration of the R/S device or the electrode array, in adult patients

Cochlear Implant Receiver Location and Migration: Experimental Validation Pilot Study of a Clinically Applicable Screening Method

Objectives: Postoperative follow-up after cochlear implantation lacks a reliable screening method to detect cochlear implant receiver device migration. This study aims to validate a clinically applicable method to assess the position and migration of the cochlear implant receiver device. Study design: Validation study. Setting: Tertiary university medical center. Participants and method: To assess the cochlear implant receiver device location, round markers representing the external magnet were placed on both sides of the head of volunteers. Four independent clinicians took measurements of the distances between reference points on the head and the center of the marker. The reference points were: the lateral canthus (LC), tragus tip (TT), the mastoid angle (MA), and the mandibular angle (AM). Main outcome measures: The inter-clinician reliability was determined by calculating the intraclass correlation coefficient (ICC) and confidence interval (CI) with a two-way mixed model and both consistency and absolute agreement types for each distance. Results: Eight volunteers were included resulting in 16 individual cases. The consistency type ICC's for each reference point were: LC 0.90 (CI = 0.80, 0.96), TT 0.83 (CI = 0.69, 0.93), MA 0.75 (CI = 0.56, 0.89), and AM 0.29 (CI = 0.05, 0.59). The absolute agreement ICC's were: LC 0.87 (CI = 0.73, 0.95), TT 0.83 (CI = 0.68, 0.93), MA 0.68 (CI = 0.42, 0.86), and AM 0.18 (CI = 0.01, 0.46). The inter-clinician reliability was good to excellent for the lateral canthus and tragus tip reference points. Conclusions: The cochlear receiver device location can be assessed reliably by measuring the distance between the LC, TT, and the external magnet. This method can be used to registrate implant receiver location after implantation and detect implant migration postoperatively

A monocenter, patient-blinded, randomized, parallel-group, non-inferiority study to compare cochlear implant receiver/stimulator device fixation techniques (COMFIT) with and without drilling in adults eligible for primary cochlear implantation

Abstract Background During the cochlear implantation procedure, the receiver/stimulator (R/S) part of the implant is fixated to prevent postoperative device migration, which could have an adverse effect on the position of the electrode array in the cochlea. We aim to compare the migration rates of two fixation techniques, the bony recess versus the subperiosteal tight pocket without bony sutures. Methods and analysis This single-blind randomized controlled trial will recruit a total of 112 primary cochlear implantation adult patients, eligible for implantation according to the current standard of practice. Randomization will be performed by an electronic data capture system Castor EDC, with participants block randomized to either bony recess or standard subperiosteal tight pocket in a 1:1 ratio, stratified by age. The primary outcome of this study is the R/S device migration rate; secondary outcomes include patient-experienced burden using the validated COMPASS questionnaire, electrode migration rate, electrode impedance values, speech perception scores, correlation between R/S migration, electrode array migration and patient complaints, assessment of complication rates, and validation of an implant position measurement method. Data will be collected at baseline, 1 week, 4 weeks, 8 weeks, 3 months, and 12 months after surgery. All data analyses will be conducted according to the intention-to-treat principle. Discussion Cochlear implantation by means of creating a tight subperiosteal pocket without drilling a bony seat is a minimally invasive fixation technique with many advantages. However, the safety of this technique has not yet been proven with certainty. This is the first randomized controlled trial that directly compares the minimally invasive technique with the conventional method of drilling a bony seat. Trial registration Netherlands Trial Register NL9698. Registered on 31 August 2021

Cochlear implant positioning and fixation using 3D-printed patient specific surgical guides; a cadaveric study

Hypothesis To develop and validate the optimal design and evaluate accuracy of individualized 3D- printed surgical guides for cochlear implantation. Background Positioning and fixation of the cochlear implant (CI) are commonly performed free hand. Applications of 3-dimensional (3D) technology now allow us to make patient specific, bone supported surgical guides, to aid CI surgeons with precise placement and drilling out the bony well which accommodates the receiver/stimulator device of the CI. Methods Cone beam CT (CBCT) scans were acquired from temporal bones in 9 cadaveric heads (18 ears), followed by virtual planning of the CI position. Surgical, bone-supported drilling guides were designed to conduct a minimally invasive procedure and were 3D-printed. Fixation screws were used to keep the guide in place in predetermined bone areas. Specimens were implanted with 3 different CI models. After implantation, CBCT scans of the implanted specimens were performed. Accuracy of CI placement was assessed by comparing the 3D models of the planned and implanted CI’s by calculating the translational and rotational deviations. Results Median translational deviations of placement in the X- and Y-axis were within the predetermined clinically relevant deviation range (Conclusion This study resulted in the first 3D-printed, patient- and CI- model specific surgical guide for positioning during cochlear implantation. The next step for the development and evaluation of this surgical guide will be to evaluate the method in clinical practice

Cochlear implant positioning and fixation using 3D-printed patient specific surgical guides; a cadaveric study

Hypothesis To develop and validate the optimal design and evaluate accuracy of individualized 3D-printed surgical guides for cochlear implantation. Background Positioning and fixation of the cochlear implant (CI) are commonly performed free hand. Applications of 3-dimensional (3D) technology now allow us to make patient specific, bone supported surgical guides, to aid CI surgeons with precise placement and drilling out the bony well which accommodates the receiver/stimulator device of the CI. Methods Cone beam CT (CBCT) scans were acquired from temporal bones in 9 cadaveric heads (18 ears), followed by virtual planning of the CI position. Surgical, bone-supported drilling guides were designed to conduct a minimally invasive procedure and were 3D-printed. Fixation screws were used to keep the guide in place in predetermined bone areas. Specimens were implanted with 3 different CI models. After implantation, CBCT scans of the implanted specimens were performed. Accuracy of CI placement was assessed by comparing the 3D models of the planned and implanted CI’s by calculating the translational and rotational deviations. Results Median translational deviations of placement in the X- and Y-axis were within the predetermined clinically relevant deviation range (< 3 mm per axis); median translational deviation in the Z-axis was 3.41 mm. Median rotational deviations of placement for X-, Y- and Z-rotation were 5.50°, 4.58° and 3.71°, respectively. Conclusion This study resulted in the first 3D-printed, patient- and CI- model specific surgical guide for positioning during cochlear implantation. The next step for the development and evaluation of this surgical guide will be to evaluate the method in clinical practice