Comparing linear and non-linear models to estimate the appropriate cochlear implant electrode array length-are current methods precise enough?

PURPOSE: In cochlear implantation with flexible lateral wall electrode arrays, a cochlear coverage (CC) range between 70% and 80% is considered ideal for optimal speech perception. To achieve this CC, the cochlear implant (CI) electrode array has to be chosen according to the individual cochlear duct length (CDL). Here, we mathematically analyzed the suitability of different flexible lateral wall electrode array lengths covering between 70% and 80% of the CDL. METHODS: In a retrospective cross-sectional study preoperative high-resolution computed tomography (HRCT) from patients undergoing cochlear implantation was investigated. The CDL was estimated using an otosurgical planning software and the CI electrode array lengths covering 70-80% of the CDL was calculated using (i) linear and (ii) non-linear models. RESULTS: The analysis of 120 HRCT data sets showed significantly different model-dependent CDL. Significant differences between the CC of 70% assessed from linear and non-linear models (mean difference: 2.5 mm, p < 0.001) and the CC of 80% assessed from linear and non-linear models (mean difference: 1.5 mm, p < 0.001) were found. In up to 25% of the patients none of the existing flexible lateral wall electrode arrays fit into this range. In 59 cases (49,2%) the models did not agree on the suitable electrode arrays. CONCLUSIONS: The CC varies depending on the underlying CDL approximation, which critically influences electrode array choice. Based on the literature, we hypothesize that the non-linear method systematically overestimates the CC and may lead to rather too short electrode array choices. Future studies need to assess the accuracy of the individual mathematical models.

Impact of Insertion Speed, Depth, and Robotic Assistance on Cochlear Implant Insertion Forces and Intracochlear Pressure: A Scoping Review.

Cochlear implants are crucial for addressing severe-to-profound hearing loss, with the success of the procedure requiring careful electrode placement. This scoping review synthesizes the findings from 125 studies examining the factors influencing insertion forces (IFs) and intracochlear pressure (IP), which are crucial for optimizing implantation techniques and enhancing patient outcomes. The review highlights the impact of variables, including insertion depth, speed, and the use of robotic assistance on IFs and IP. Results indicate that higher insertion speeds generally increase IFs and IP in artificial models, a pattern not consistently observed in cadaveric studies due to variations in methodology and sample size. The study also explores the observed minimal impact of robotic assistance on reducing IFs compared to manual methods. Importantly, this review underscores the need for a standardized approach in cochlear implant research to address inconsistencies and improve clinical practices aimed at preserving hearing during implantation.

Association between lateral wall electrode array insertion parameters and audiological outcomes in bilateral cochlear implantation.

PURPOSE: The aims of this study were to compare speech recognition at different postoperative times for both ears in bilaterally implanted patients and to assess the influence of the time of deafness, frequency-to-place mismatch, angular insertion depth (AID) and angular separation between neighbouring electrode contacts on audiometric outcomes. METHODS: This study was performed at an academic tertiary referral centre. A total of 19 adult patients (6 men, 13 women), who received sequential bilateral implantation with lateral wall electrode arrays, were analysed in retrospective. Statistical analysis was performed using two-sided t test, Wilcoxon test, median test, and Spearman's correlation. RESULTS: Postlingually deafened patients (deafness after the age of 10) had a significantly better speech perception (WRS65[CI]) than the perilingually deafened subjects (deafness at the age of 1-10 years) (p < 0.001). Comparison of cochlear duct length between peri- and postlingually deafened subjects showed a slightly significantly smaller cochleae in perilingual patients (p = 0.045). No association between frequency-to-place mismatch as well as angular separation and speech perception could be detected. There was even no significant difference between the both ears in the intraindividual comparison, even if insertion parameters differed. CONCLUSION: The exact electrode position seems to have less influence on the speech comprehension of CI patients than already established parameters as preoperative speech recognition or duration of deafness.

[Speech perception as a function of cochlear coverage-comparison in bimodally hearing cochlear implant patients. German version]. / Sprachverstehen in Abhängigkeit von der cochleären Abdeckung ­ Vergleich bei bimodal versorgten Cochleaimplantatpatienten.

BACKGROUND: Hearing success in bimodally hearing patients with a cochlear implant (CI) and a hearing aid (HA) exhibits different results: while some benefit from bimodal CI and HA, others do not. OBJECTIVE: The aim of this study was to investigate hearing success in terms of speech perception in bimodally fitted patients in relation to the cochlear coverage (CC) of the CI electrodes. MATERIALS AND METHODS: Using the OTOPLAN software (CAScination AG, Bern, Switzerland), CC was retrospectively measured from CT scans of the temporal bone of 39 patients, who were then categorized into two groups: CC ≤ 65% (CC500) and CC > 65% (CC600). Monaural speech intelligibility for monosyllables at a sound pressure level (SPL) of 65 dB in open field was assessed at various timepoints, preoperatively with HA and postoperatively with CI, and compared between the groups. In addition, speech intelligibility was correlated with CC in the entire cohort before surgery and during follow-up (FU). RESULTS: Overall, no significant differences in speech intelligibility were found between CC500 and CC600 patients at any of the FU timepoints. However, both CC500 and CC600 patients showed a steady improvement in speech intelligibility after implantation. While CC600 patients tended to show an earlier improvement in speech intelligibility, CC500 patients tended to show a slower improvement during the first 3 months and a steeper learning curve thereafter. The two patient groups converged during FU, with no significant differences in speech intelligibility. There was no significant relationship between unimodal/unilateral free-field speech intelligibility and CC. However, patients with a CC of 70-75% achieved maximum speech intelligibility. CONCLUSION: Despite a nonsignificant correlation between CC and speech discrimination, patients seem to reach their maximum in unimodal/unilateral speech understanding mainly at 70-75% coverage. However, there is room for further investigation, as CC500 was associated with a shorter cochlear duct length (CDL), and long and very long electrodes were used in both groups.

Effects of different pedicle screw insertion depths on sagittal balance of lumbar degenerative spondylolisthesis, a retrospective comparative study.

BACKGROUND: Few reports to date have evaluated the effects of different pedicle screw insertion depths on sagittal balance and prognosis after posterior lumbar interbody and fusion (PLIF) in patients with lumbar degenerative spondylolisthesis (LDS). METHODS: A total of 88 patients with single-level PLIF for LDS from January 2018 to December 2019 were enrolled. Long screw group (Group L): 52 patients underwent long pedicle screw fixation (the leading edge of the screw exceeded 80% of the anteroposterior diameter of vertebral body). Short screw group (Group S): 36 patients underwent short pedicle screw fixation (the leading edge of the screw was less than 60% of the anteroposterior diameter of vertebral body). Local deformity parameters of spondylolisthesis including slip degree (SD) and segment lordosis (SL), spino-pelvic sagittal plane parameters including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS) and lumbar lordosis (LL), Oswestry Disability Index (ODI), and Visual Analog Scale (VAS) for back pain of both groups were compared. Postoperative complications, including vertebral fusion rate and screw loosening rate, were recorded. RESULTS: Except that PI in Group S at the final follow-up was not statistically different from the preoperative value (P > 0.05), other parameters were significantly improved compared with preoperative values one month after surgery and at the final follow-up (P < 0.05). There was no significant difference in parameters between Group L and Group S before and one month after surgery (P > 0.05). At the final follow-up, SD, SL, LL, PT and PI-LL differed significantly between the two groups (P < 0.05). Compared with the preoperative results, ODI and VAS in both groups decreased significantly one month after surgery and at the final follow-up (P < 0.05). Significant differences of ODI and VAS were found between the two groups at the final follow-up (P < 0.05). Postoperative complications were not statistically significant between the two groups (P > 0.05). CONCLUSIONS: PLIF can significantly improve the prognosis of patients with LDS. In terms of outcomes with an average follow-up time of 2 years, the deeper the screw depth is within the safe range, the better the spino-pelvic sagittal balance may be restored and the better the quality of life may be.

Stapes Prosthesis Length: One Size Fits All?

BACKGROUND: The insertion of the stapes piston into the vestibule provides the physical basis for a successful stapedotomy. In routine clinical practice, two different ways to handle prosthesis length are performed: (1) an individualized measurement of the stapes prosthesis length or (2) a standard prosthesis length for all cases. OBJECTIVE: The objective of this study was to compare both ways of handling prosthesis length and the effect of these methods on insertional prosthesis depth. MATERIAL AND METHOD: We retrospectively evaluated 39 patients after performing a stapedotomy for radiologically estimated vestibular stapes prosthesis insertion depth. The individual measured length data were hypothetically changed to a standard length of 4.75, 5, 5.25, and 5.5 mm, and the insertion depths were compared. RESULTS: The individually measured prosthesis lengths led to an insertion depth between 0.2 and 1.6 mm (mean 0.74 mm). The ratio of insertion depth/vestibular depth was between 8 and 59.1% (mean 26.6%). The different assumed standard lengths led to different rates of the vestibulum positions and possible bony contacts at the vestibulum floor. CONCLUSION: The individual measurement led to a zero rate of the vestibulum positions of stapes prosthesis pistons with a low insertion depth/vestibular depth ratio.

An accelerometer-based navigation did not improve the femoral component positioning compared to a modified conventional technique of pre-operatively planned placement of intramedullary rod in total knee arthroplasty.

INTRODUCTION: Although the most commonly used method of femoral component alignment in total knee arthroplasty (TKA) is intramedullary (IM) guides, this method demonstrated a limited degree of accuracy. Because of the femoral anterior bowing, the tip of the guide rod will impinge on the anterior cortex if a long rod is inserted. We hypothesized that the pre-operative planned insertion depth of the rod could increase the accuracy of the femoral component positioning in conventional TKA (modified conventional technique). Accelerometer-based, portable navigation device has been postulated to have better accuracy than conventional TKA in component positioning. The purpose of this study was to compare the post-operative femoral component alignment of TKA using the modified conventional technique with the accelerometer-based navigation. MATERIALS AND METHODS: Fifty-five knees underwent TKA using the modified conventional technique and femoral component positioning was compared with 55 knees performed using the accelerometer-based navigation device. The femoral component alignment was evaluated with a CT-based three-dimensional software. RESULTS: The mean absolute deviation from targeted alignment in the sagittal plane was significantly less in the modified conventional cohort than in the accelerometer-based navigation cohort (1.1° vs 2.6°, P < 0.001). In the modified conventional cohort, 96.4% had an alignment within 3° of a targeted angle in the coronal plane (vs 89.1% with the accelerometer-based navigation, P = 0.14), and 96.4% in the sagittal plane (vs 74.5% with the accelerometer-based navigation, P < 0.001). CONCLUSION: The modified conventional technique is a simple and equal to or more accurate method than the accelerometer-based navigation in positioning the femoral component in TKA at a mid-volume hospital.

Assessment of tobacco heating product THP1.0. Part 8: Study to determine puffing topography, mouth level exposure and consumption among Japanese users.

A four-arm study was undertaken in Japan to determine the puffing topography, mouth level exposure and average daily consumption by consumers of the tobacco heating products (THPs): the non-mentholated THP1.0(T), the mentholated THP1.0(M) and a tobacco heating system (THS). The extent of lip blocking of air inlet holes while using THP1.0(T) was also assessed. Groups 1, 2, and 4 included smokers, and group 3 included regular THP users. Smokers of 7-8 mg ISO nicotine free dry particulate matter (NFDPM) non-mentholated cigarettes took on average larger mean puff volumes from THPs than from conventional cigarettes, but puff numbers and durations were similar. Mouth level exposure to NFDPM and nicotine levels were significantly lower when using THPs than conventional cigarettes. Similar trends were observed among smokers of 7-8 mg ISO NFDPM mentholated cigarettes who used mentholated cigarettes and THP1.0(M). Regular users of commercial THS had similar puffing behaviours irrespective of whether they were using THS or THP1.0(T), except for mean puff volume which was lower with THP1.0(T). No smokers blocked the air inlet holes when using THP1.0(T). The puffing topography results support the machine puffing regime used to generate toxicant emissions data and in vitro toxicology testing.

Chest Computed Tomography Image for Accurately Predicting the Optimal Insertion Depth of Left-Sided Double-Lumen Tube.

OBJECTIVE: The main objective of this study was to assess the feasibility and accuracy of measuring the distance between the vocal cord and carina using chest computer tomography (CT) as a guide for the intubation of a left-sided double-lumen tube (LDLT). DESIGN: Single-center, prospective, randomized study. SETTING: Local hospital in China. PARTICIPANTS: Sixty adult patients undergoing elective thoracic surgery requiring an LDLT for one lung ventilation were enrolled in this study. INTERVENTIONS: Patients were randomly allocated to the following 2 groups: blind intubation group (B group, n = 30) or chest computed tomography-guided group (C group, n = 30). The placement of the LDLT was accomplished using 1 of the 2 intubation methods. After intubation, an independent anesthesiologist evaluated the position of the LDLT and carina and bronchial injuries using fiber optic bronchoscopy. The number of optimal positions, the time for LDLT intubation, the time for fiber optic bronchoscope confirmation, and carina and bronchial injuries were recorded. RESULTS: Sixteen of 30 intubations in the B group were in optimal position, whereas 27 of 30 intubations in the C group were in optimal position; the difference was statistically significant (p < 0.01). The time for intubation of the LDLT took 118.0 ± 26.2 seconds in the B group and 71.5 ± 8.7 seconds in the C group (p < 0.01). The time for position confirmation using fiber optic bronchoscope took 40.8 ± 15.8 seconds in the B group and 18.7 ± 7.9 seconds in the C group (p < 0.05). The incidences of carina and bronchial injuries were obviously lower in the C group (occurred in 3 of 30 cases) than in the B group (11 of 30 cases) p < 0.05. The incidences of postoperative sore throat and hoarseness showed no significant differences between the 2 groups (p > 0.05). CONCLUSION: This study demonstrated that the method of measuring the distance between the vocal cord and carina according to the chest CT as a guide for the intubation of LDLT is more effective and more accurate than the blind intubation method.

Influence of subcrestal implant placement compared with equicrestal position on the peri-implant hard and soft tissues around platform-switched implants: a systematic review and meta-analysis.

AIM: The aim of this article is to systematically review the effect of subcrestal implant placement compared with equicrestal position on hard and soft tissues around dental implants with platform switch. MATERIAL AND METHODS: A manual and electronic search (National Library of Medicine and Cochrane Central Register of Controlled Trials) was performed for animal and human studies published up to December 2016. Primary outcome variable was marginal bone level (MBL) and secondary outcomes were crestal bone level (CBL), soft tissue dimensions (barrier epithelium, connective tissue, and peri-implant mucosa), and changes in the position of soft tissue margin. For primary and secondary outcomes, data reporting mean values and standard deviations of each study were extracted and weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated. RESULTS: A total of 14 publications were included (7 human studies and 7 animal investigations). The results from the meta-analyses have shown that subcrestal implants, when compared with implants placed in an equicrestal position, exhibited less MBL changes (human studies: WMD = - 0.18 mm; 95% CI = - 1.31 to 0.95; P = 0.75; animal studies: WMD = - 0.45 mm; 95% CI = - 0.66 to - 0.24; P < 0.001). Furthermore, the CBL was located at a more coronal position in subcrestal implants with respect to the implant shoulder (WMD = - 1.09 mm; 95% CI = - 1.43 to - 0.75; P < 0.001). The dimensions of the peri-implant mucosa seem to be affected by the positioning of the microgap and were greater at implants placed in a subcrestal position than those inserted equicrestally (WMD = 0.60 mm; 95% CI = 0.26 to 0.95; P < 0.001). While the length of the barrier epithelium was significantly greater in implants placed in a subcrestal position (WMD = 0.39 mm; 95% CI = 0.19 to 0.58; P < 0.001), no statistical significant differences were observed between equicrestal and subcrestal implant positioning for the connective tissue length (WMD = 0.17 mm; 95% CI = - 0.03 to 0.36; P = 0.10). CONCLUSION: This systematic review suggests that PS implants placed in a subcrestal position have less MBL changes when compared with implants placed equicrestally. Furthermore, the location of the microgap seems to have an influence on the dimensions of peri-implant soft tissues. Clinical relevance When compared with PS placed in an equicrestal position, subcrestal implant positioning demonstrated less peri-implant bone remodeling.

Three-dimensional assessment of crestal bone levels at titanium implants with different abutment microstructures and insertion depths using micro-computed tomography.

OBJECTIVES: To (i) assess the impact of insertion depth and abutment microstructure on the three-dimensional crestal bone-level changes at endosseous titanium implant using µCT and computerized image processing and (ii) to correlate the findings with previously reported histology. MATERIAL & METHODS: Titanium implants (conical abutment connection) were inserted in each hemimandible of n = 6 foxhounds with the implant shoulder (IS) located either in epicrestal (0 mm), supracrestal (+1 mm) or subcrestal (-1 mm) positions and randomly (split-mouth design) connected with machined or partially micro-grooved healing abutments. At 20 weeks, the tissue biopsies were processed for µCT and histological (HI) analyses. The volumetric dehiscence profile around the implants was computed as distance between the implant shoulder (IS) and the most coronal bone-to-implant contact (CBI) using MATLAB. The respective buccal and oral values were averaged, and agreement with the respective IS-CBI scores from HI was assessed using Bland-Altman plots. RESULTS: A median net bone gain was observed for supracrestal insertion depths at both abutment types, but lower bounds of the 75% quartile experienced net bone losses. Epicrestal and subcrestal insertion depths were linked to slight bone losses, and the buccal and oral dehiscences were smaller compared to supracrestal positioning. Bland-Altman plots yielded a moderate agreement of IS-CBI values measured with µCT and HI. CONCLUSION: The novel image processing method allowed reliable evaluations and pointed to a direct impact of insertion depths on crestal bone-level changes. Additionally, it demonstrated that HI morphometry crucially depends on the chosen cutting position.

Impact of needle insertion depth on the removal of hard-tissue debris.

AIM: To evaluate the effect of depth of insertion of an irrigation needle tip on the removal of hard-tissue debris using micro-computed tomographic (micro-CT) imaging. METHODOLOGY: Twenty isthmus-containing mesial roots of mandibular molars were anatomically matched based on similar morphological dimensions using micro-CT evaluation and assigned to two groups (n = 10), according to the depth of the irrigation needle tip during biomechanical preparation: 1 or 5 mm short of the working length (WL). The preparation was performed with Reciproc R25 file (tip size 25, .08 taper) and 5.25% NaOCl as irrigant. The final rinse was 17% EDTA followed by bidistilled water. Then, specimens were scanned again, and the matched images of the canals, before and after preparation, were examined to quantify the amount of hard-tissue debris, expressed as the percentage volume of the initial root canal volume. Data were compared statistically using the Mann-Whitney U-test. RESULTS: None of the tested needle insertion depths yielded root canals completely free from hard-tissue debris. The insertion depth exerted a significant influence on debris removal, with a significant reduction in the percentage volume of hard-tissue debris when the needle was inserted 1 mm short of the WL (P < 0.05). CONCLUSIONS: The insertion depth of irrigation needles significantly influenced the removal of hard-tissue debris. A needle tip positioned 1 mm short of the WL resulted in percentage levels of hard-tissue debris removal almost three times higher than when positioned 5 mm from the WL.

Effects of insertion depth on spatial speech perception in noise for simulations of cochlear implants and single-sided deafness.

OBJECTIVE: This study evaluated the effects of insertion depth on spatial speech perception in noise for simulations of cochlear implants (CI) and single-sided deafness (SSD). DESIGN: Mandarin speech recognition thresholds were adaptively measured in five listening conditions and four spatial configurations. The original signal was delivered to the left ear. The right ear received either no input, one of three CI simulations in which the insertion depth was varied, or the original signal. Speech and noise were presented at either front, left, or right. STUDY SAMPLE: Ten Mandarin-speaking NH listeners with pure-tone thresholds less than 20 dB HL. RESULTS: Relative to no input in the right ear, the CI simulations provided significant improvements in head shadow benefit for all insertion depths, as well as better spatial release of masking (SRM) for the deepest simulated insertion. There were no significant improvements in summation or squelch for any of the CI simulations. CONCLUSIONS: The benefits of cochlear implantation were largely limited to head shadow, with some benefit for SRM. The greatest benefits were observed for the deepest simulated CI insertion, suggesting that reducing mismatch between acoustic and electric hearing may increase the benefit of cochlear implantation.

Effect of fiber insertion depth on antibacterial efficacy of photodynamic therapy against Enterococcus faecalis in rootcanals.

OBJECTIVES: This in vitro study evaluated the effect of fiber insertion depth on antimicrobial efficacy of antimicrobial photodynamic therapy (aPDT) using a photosensitizer (PS; toluidine blue) and a red light-emitting diode (LED) in root canals infected with Enterococcus faecalis. MATERIALS AND METHODS: Single-rooted extracted teeth were prepared with nickel-titanium-instruments, sterilized, contaminated with E. faecalis, and incubated for 72 h. Roots were randomly divided into four experimental groups: PS only, LED only, aPDT with LED in the apical third, aPDT with LED in the coronal third, as well as into infection and sterile controls (each n = 10). Samples were taken by collecting standardized dentine shavings from the root canal walls. After serial dilution and culturing on blood agar, colony-forming units (CFU) were counted. RESULTS: Both aPDT groups showed a CFU reduction of 1-2 log10 steps compared with the infection control, whereas the effect of fiber insertion depth was negligible (<0.5 log10 steps). CFU reduction of approximately 0.5 log10 steps for PS alone was detected compared with the infection control, but PS alone was less effective than both aPDT groups. No antibacterial effect was detected for LED alone. CONCLUSIONS: aPDT reduced E. faecalis within the root canal, whereas fiber insertion depth had a negligible influence on antimicrobial effectiveness of aPDT. CLINICAL RELEVANCE: The insertion depth of the light-emitting diode may not influence the antibacterial efficacy of photodynamic therapy against E. faecalis in straight root canals.

Predicting Optimal Insertion Depth of a Left-sided Double-Lumen Endobronchial Tube.

OBJECTIVE: Appropriate placement of the double-lumen endobronchial tube (DLT) is essential for one-lung ventilation. Several formulae based on body height (BH) have been used for estimating the optimal insertion depth of a left-sided DLT. In this study, the authors examined the following 5 formulae for accuracy of prediction: 0.11×BH+10.53 (cm) from Brodsky et al(1); 0.15×BH+3.96 (cm) from Bahk and Oh(2); 0.148×BH+3.8 (cm) from Chow et al;(3) 0.1×BH+12.5 (cm) from Takita et al(4); and 0.1977×BH - 4.2423 (cm) (authors' formula). DESIGN: Single-center, retrospective, observational study. SETTING: University hospital. PARTICIPANTS: Anesthetic records of patients older than 20 years who received one-lung ventilation using a left-sided DLT were included. INTERVENTIONS: The patients' sex, age, body weight, BH, and the final correct insertion depth of the left-sided DLT after fiberscope verification were recorded. Linear regression and correlation were used to analyze the data. MEASUREMENTS AND MAIN RESULTS: One hundred seventy anesthetic records were analyzed. The insertion depth was distributed normally in 4 groups with different BH intervals. The correlations between the correct insertion depth and all the lengths calculated using each formula were significant (p<0.001), with a similar high coefficient of determination (r = 0.809). The regression line derived from the authors' formula-0.1977×BH - 4.2423 (cm)-showed the most accuracy in predicting the correct insertion depth. CONCLUSIONS: The height-based formula of 170 - 29.5 - 5 - 1 (the insertion depth is 29.5 cm for patients who are 170 cm tall, and the insertion length is increased or decreased by 1 cm for every 5 cm increase or decrease in BH) modified by the equation of 0.1977×BH - 4.2423 is a useful tool to predict the optimal insertion depth in initially blind left-sided DLT insertion.

[Estimation of the optimal tube length : Systematic review article on published formulae for infants and children]. / Abschätzung der optimalen Tubuslänge : Systematische Übersichtsarbeit zu publizierten Formeln bei Säuglingen und Kindern.

BACKGROUND: The correct placement of an endotracheal tube in children is essential as incorrect placement following unilateral ventilation and tube displacement may lead to far-reaching consequences, such as volutrauma and hypoxia, respectively. Different formulae referring to the correct placement of nasotracheal and orotracheal tubes have been published with reference to body weight and age. OBJECTIVE: The aim of the present review article was to identify and compare the published formulae for estimating correct endotracheal tube placement in children with their advantages and disadvantages. MATERIAL AND METHODS: A search in Medline and PubMed was performed to identify published formulae. Formulae for insertion depth in orotracheal and also nasotracheal intubation are discussed. The published formulae for newborns and infants are presented separately. The keywords "paediatric"/"pediatric", "anaesthesia"/"anesthesia", "anaesthesiology"/"anesthesiology", "endotracheal tube", "placement", "position", "length", "depth" and "insertion" were used to identify the formulae. RESULTS: A total of 806 publications were found, 16 publications were identified as being relevant and 13 different formulae were identified. In the age group from 1 to 16 years old a total of 7 formulae (6 age-based formulae and one based on weight) and for newborns and infants a total of 6 formulae (4 formulae based on body weight, 1 formula based on body length and 1 formula based on gestational age) were found. All publications were subsequently assessed and classified independently by a specialist physician in anesthesiology and a specialist physician in pediatrics. CONCLUSION: The published formulae were comparatively simply to apply but had notable limitations. Correlating the position of the endotracheal tubes with chest x-rays, the concordance analysis showed that for the age-based formulae using orotracheal as well as nasotracheal intubation and in both age groups, an accordance could only be achieved in a maximum of 81%. In the presence of a lack of alternative possibilities, only one formula based on the gestational age seemed to have an impact on estimation of correct endotracheal tube depth placement in newborns and infants. Therefore, a generally valid formula cannot be recommended without verification by auscultation or chest x-ray.

Impact of abutment microstructure and insertion depth on crestal bone changes at nonsubmerged titanium implants with platform switch.

OBJECTIVES: To assess the impact of microgrooved abutments and the insertion depth on crestal bone changes at titanium implants with platform switch. MATERIALS AND METHODS: A total of n = 3 titanium implants (conical abutment connection) were inserted in each hemimandible of n = 6 foxhounds with the implant shoulder (IS) located at either epicrestal, supracrestal (+1 mm), or subcrestal (-1 mm) positions and randomly (split-mouth design) connected with machined or partially microgrooved healing abutments. At 20 weeks, tissue biopsies were processed for histological (primary outcome: net bone loss - NET) analyses. RESULTS: Subcrestal positioning of IS tended to be associated with higher mean NET values (mm) at both machined (subcrestal [-0.72 ± 0.32] > epicrestal [-0.34 ± 0.21] > supracrestal [+0.20 ± 0.64]) and microgrooved (subcrestal [-0.48 ± 0.25] > epicrestal [-0.13 ± 0.54] > supracrestal [+0.33 ± 0.58]) abutments. However, these differences failed to reach statistical significance. CONCLUSIONS: The insertion depth may have a direct influence on crestal bone-level changes at both types of abutments investigated.

Estimation of insertion depth angle based on cochlea diameter and linear insertion depth: a prediction tool for the CI422.

Beside the cochlear size, the linear insertion depth (LID) influences the insertion depth angle of cochlear implant electrode arrays. For the specific implant CI422 the recommended LID is not fixed but can vary continuously between 20 and 25 mm. In the current study, the influence of cochlea size and LID on the final insertion depth angle was investigated to develop a prediction tool for the insertion depth angle by means of cochlea diameter and LID. Preoperative estimation of insertion depth angles might help surgeons avoid exceeding an intended insertion depth, especially with respect to low-frequency residual hearing preservation. Postoperative, high-resolution 3D-radiographs provided by Flat Panel Computed Volume Tomography (FPCT) were used to investigate the insertion depth angle in 37 CI422 recipients. Furthermore, the FPCT images were used to measure linear insertion depth and diameter of the basal turn of the cochlea. A considerable variation of measured insertion depth angles ranging from 306° to 579° was identified. The measured linear insertion depth ranged from -18.6 to 26.2 mm and correlated positively with the insertion depth angle. The cochlea diameter ranged from 8.11 to 10.42 mm and correlated negatively with the insertion depth angle. The results suggest that preoperatively measured cochlea diameter combined with the option of different array positions by means of LID may act as predictors for the final insertion depth angle.

Ultrasonic irrigation flows in root canals: effects of ultrasound power and file insertion depth.

Ultrasonic irrigation during root canal treatment can enhance biofilm disruption. The challenge is to improve the fluid flow so that the irrigant reaches areas inaccessible to hand instrumentation. The aim of this study is to experimentally investigate how the flow field and hydrodynamic forces induced by ultrasonic irrigation are influenced by the ultrasound power and file insertion depth. A root canal phantom was 3D printed and used as a mold for the fabrication of a PDMS channel. An ultrasonic instrument with a #15K-file provided the irrigation. The flow field was studied by means of Particle Image Velocimetry (PIV). The time averaged velocity and shear stress distributions were found to vary significantly with ultrasound power. Their maximum values increase sharply for low powers and up to a critical power level. At and above this setting, the flow pattern changes, from the high velocity and shear stress region confined in the vicinity of the tip, to one covering the whole root canal domain. Exceeding this threshold also induces a moderate increase in the maximum velocities and shear stresses. The insertion depth was found to have a smaller effect on the measured velocity and shear stresses. Due to the oscillating nature of the flow, instantaneous maximum velocities and shear stresses can reach much higher values than the mean, especially for high powers. Ultrasonic irrigation will benefit from using a higher power setting as this does produce greater shear stresses near the walls of the root canal leading to the potential for increased biofilm removal.

Insertion profiles of 4 headless compression screws.

PURPOSE: In practice, the surgeon must rely on screw position (insertion depth) and tactile feedback from the screwdriver (insertion torque) to gauge compression. In this study, we identified the relationship between interfragmentary compression and these 2 factors. METHODS: The Acutrak Standard, Acutrak Mini, Synthes 3.0, and Herbert-Whipple implants were tested using a polyurethane foam scaphoid model. A specialized testing jig simultaneously measured compression force, insertion torque, and insertion depth at half-screw-turn intervals until failure occurred. RESULTS: The peak compression occurs at an insertion depth of -3.1 mm, -2.8 mm, 0.9 mm, and 1.5 mm for the Acutrak Mini, Acutrak Standard, Herbert-Whipple, and Synthes screws respectively (insertion depth is positive when the screw is proud above the bone and negative when buried). The compression and insertion torque at a depth of -2 mm were found to be 113 ± 18 N and 0.348 ± 0.052 Nm for the Acutrak Standard, 104 ± 15 N and 0.175 ± 0.008 Nm for the Acutrak Mini, 78 ± 9 N and 0.245 ± 0.006 Nm for the Herbert-Whipple, and 67 ± 2N, 0.233 ± 0.010 Nm for the Synthes headless compression screws. CONCLUSIONS: All 4 screws generated a sizable amount of compression (> 60 N) over a wide range of insertion depths. The compression at the commonly recommended insertion depth of -2 mm was not significantly different between screws; thus, implant selection should not be based on compression profile alone. Conically shaped screws (Acutrak) generated their peak compression when they were fully buried in the foam whereas the shanked screws (Synthes and Herbert-Whipple) reached peak compression before they were fully inserted. Because insertion torque correlated poorly with compression, surgeons should avoid using tactile judgment of torque as a proxy for compression. CLINICAL RELEVANCE: Knowledge of the insertion profile may improve our understanding of the implants, provide a better basis for comparing screws, and enable the surgeon to optimize compression.