Deep Implantation Research Articles

Optimized radiofrequency shimming using low-heating B1+-mapping in the presence of deep brain stimulation implants: Proof of concept.

MRI of patients with Deep Brain Stimulation (DBS) implants is constrained due to radiofrequency (RF) heating of the implant lead. However, "RF-shimming" parallel transmission (PTX) has the potential to reduce DBS heating during MRI. As part of using PTX in such a "safe mode", maps of the RF transmission field (B1+) are typically acquired for calibration purposes, with each transmit coil excited individually. These maps often have large zones of low signal intensity distant from the specific coil that is being excited, raising concerns that low signal-to-noise ratio (SNR) in these zones might negatively impact the ability of the optimized RF shim settings to suppress heating in safe mode. One way to improve SNR would be to increase RF transmission power during B1+ mapping, but this also raises heating concerns especially for coil elements proximal to the implant. Acting with an abundance of caution, it would be useful to investigate methods that permit B1+ mapping with low localized heating while producing high SNR measurements that lead to safe PTX RF shim settings. The present work addresses this issue in proof of concept using electromagnetic simulations and experimental PTX MRI. A two-step optimization algorithm is proposed and examined for a cylindrical phantom with an implanted wire to enable 1) robust B1+ mapping with low localized heating; and 2) robust RF shimming PTX with low localized heating and good B1+ homogeneity over a large imaging volume. Simulation and experimental outcomes were compared with those obtained using an existing simulation-driven workflow for obtaining safe mode RF shim settings, and for quadrature RF transmission using a circularly polarized (CP) birdcage head coil. Experimental results showed that although both existing and proposed safe-mode workflows effectively suppressed localized heating at the wire tip in comparison to the CP coil results, the proposed workflow produced much smaller temperature elevations and much improved signal uniformity. These promising results support continued investigation and refinement of the proposed workflow, involving more realistic scenarios toward ultimate implementations in DBS patients.

Cornual Pregnancy as a Rare Entity of Ectopic Pregnancy After Assisted Reproductive Therapy‐Embryo Transfer (ART‐ET): A Case Report

ABSTRACTCornual pregnancy, a rare and life‐threatening form of ectopic pregnancy, poses significant diagnostic and therapeutic challenges due to its deep implantation in the uterus. This report presents a case of a 31‐year‐old woman with a history of assisted reproductive technology (ART) and prior salpingectomy, who was diagnosed with a right cornual pregnancy following embryo transfer. The patient experienced lower abdominal pain and was found to have an enlarged uterus on ultrasonography. Early diagnosis via three‐dimensional transvaginal ultrasonography enabled timely intervention, preventing rupture and severe hemorrhage. Surgical management involved a combined hysteroscopy and minilaparotomy to resect the cornual pregnancy. Histopathology confirmed the diagnosis, and the patient's recovery was uneventful. Elective cesarean section at 36–37 weeks was advised for future pregnancies to prevent uterine rupture.

Ultrasound-guided minimally invasive removal of deep contraceptive implants: outcomes and challenges.

Contraceptive arm implants, such as Implanon NXT®/Nexplanon®, are reversible methods of birth control that have gained global popularity, with over 20 million worldwide users. While palpable implants can be easily removed, deep or non-palpable implants pose complications during extraction, often requiring open surgery. This ultrasound-guided removal technique offers a minimally invasive, safe, and effective alternative, providing real-time control over the implant and neurovascular structures. Our study aims to evaluate the effectiveness and challenges of this implant removal method. In this retrospective observational study, all cases referred to our institution for ultrasound-guided removal of contraceptive implants, from June 2022 to December 2023, were reviewed. Our facility serves as a referral center for handling challenging implants. Twenty-nine women with contraceptive implants were referred for implant removal in this period of time. Thirty implants were sent for removal in total (one patient had a double implant). Data specific to the patients were collected: age and body mass index (BMI). Data specific to the implant were also collected: time since implant insertion (months), history of a previous removal attempt, type of implant (single or double rod), implant palpability, laterality of the implant, supra or subfascial location, success or failure of the ultrasound-guided removal procedure and presence of complications in the post-procedure. Statistical analysis was conducted to determine the relationship between the procedure success rate and these variables, and also between these variables and the supra or subfascial location of the implant. Twenty-six of the 30 implants (86.67%) were successfully removed with this fully ultrasound-guided technique. In cases where the implant could not be removed, there was a higher rate of subfascial implant location (75%), while in cases where the removal was successful, the rate of subfascial implant location was significantly lower at 19.23% (P=0.048). Patients whose implants could be removed had a median BMI of 23.71 kg/m2, which was higher than the BMI of patients whose implants could not be removed (20.82 kg/m2), with a P=0.022. No complications were registered. Percutaneous real-time ultrasound-guided implant removal is effective, safe and offers a minimally-invasive alternative to open surgery. The removal of subfascial implants is also feasible but more challenging, leading to a reduction of success rate in this group. These positive outcomes suggest its potential as a standard initial approach for deep contraceptive implant removal.

Comparison of Breast Sensibility Following Breast Reconstruction with Two Different Techniques: Deep Inferior Epigastric Perforator Flap and Implant

Introduction: Breast sensibility following reconstruction surgery, though often overlooked, holds significant importance due to its widespread occurrence and profound effects on patients’ well-being and safety. The author’s objective is to compare the sensory outcomes between deep inferior epigastric perforator (DIEP) flap microsurgery reconstruction and implant-based reconstruction. Additionally, the potential influence of sociodemographic and clinical factors on sensory recovery is explored, along with assessing temperature discrimination abilities and evaluating quality of life. Material and methods: An ambispective descriptive-analytical study was conducted involving women who underwent mastectomy with reconstruction using either DIEP flap and implants at the author’s hospital between 1990–2021. Data were collected from medical records, patient histories, physical examinations, and validated quality of life questionnaires (BREAST-Q). Spearman’s or Pearson’s correlation coefficients were employed for the analysis of quantitative variables, while the Student’s T test or Mann-Whitney U test were used to compare quantitative and qualitative variables. Results: A total of 99 women with breast reconstruction were included, 47 with DIEP flap and 52 with implants. Sensory recovery in implant-based reconstruction was found to be superior to DIEP flap reconstruction (5.03 and 5.18, respectively; p<0.005). A direct correlation was observed between sensory improvement and thermal discrimination (Spearman coefficient 0.9; p<0.001). Factors such as radiotherapy, delayed reconstruction with DIEP flap, and height with implants were associated with poorer sensory recovery in the breast. Women experiencing better breast sensibility reported higher satisfaction with their surgeon, medical team, and psychosocial quality of life. Conclusion: Women reconstructed with implants or DIEP abdominal flap exhibit suboptimal overall sensory recovery of the reconstructed breast, with slightly better outcomes observed in women reconstructed with implants. The development of novel surgical techniques aimed at enhancing sensibility after breast reconstruction could significantly benefit these patients.

Surgical treatment of long-term epilepsy-associated tumors guided by stereoelectroencephalography

PurposeAccurate detection and resection of the epileptogenic zone (EZ) in patients with long-term epilepsy-associated tumors (LEATs) are significantly correlated with favorable seizure prognosis. However, the relationship between tumors and the EZ remains unknown. This study aimed to evaluate the spatial relationship between LEATs and the EZ, as well as the electrophysiological features of LEATs.MethodsWe retrospectively studied five patients with LEATs who underwent deep electrode implantation and EZ resection in the hospital. The clinical characteristics, surgical outcomes, localizing features and intracranial SEEG results were reviewed.ResultsOne female and four males (mean age: 25.2 years; median age: 24 years; range: 13–45 years) were included in the study. Five-to-eleven electrodes (mean: 8.4) were implanted per patient. The EZ was located in the tumor and nearby cortex in three cases and in the tumor and distant areas in two cases. Pathological examination revealed ganglioglioma in four cases, two of which were associated with hippocampal sclerosis, and the other case showed a multinodular and vacuolating neuronal tumor with gliosis. All patients were seizure-free for at least 24 months postoperatively.ConclusionsSEEG provides valuable insights into the electrophysiological mechanisms of LEATs. The EZ often contains brain tissue around the tumor. However, only a few cases, particularly those with temporoparietal occipital (TPO) area involvement, a long history of epilepsy and other abnormalities on MRI, such as hippocampal sclerosis and focal cortical dysplasia, may include distant areas.

Neuronal activity in the ventral tegmental area during goal-directed navigation recorded by low-curvature microelectrode arrays

Navigating toward destinations with rewards is a common behavior among animals. The ventral tegmental area (VTA) has been shown to be responsible for reward coding and reward cue learning, and its response to other variables, such as kinematics, has also been increasingly studied. These findings suggest a potential relationship between animal navigation behavior and VTA activity. However, the deep location and small volume of the VTA pose significant challenges to the precision of electrode implantation, increasing the uncertainty of measurement results during animal navigation and thus limiting research on the role of the VTA in goal-directed navigation. To address this gap, we innovatively designed and fabricated low-curvature microelectrode arrays (MEAs) via a novel backside dry etching technique to release residual stress. Histological verification confirmed that low-curvature MEAs indeed improved electrode implantation precision. These low-curvature MEAs were subsequently implanted into the VTA of the rats to observe their electrophysiological activity in a freely chosen modified T-maze. The results of the behavioral experiments revealed that the rats could quickly learn the reward probability corresponding to the left and right paths and that VTA neurons were deeply involved in goal-directed navigation. Compared with those in no-reward trials, VTA neurons in reward trials presented a significantly greater firing rate and larger local field potential (LFP) amplitude during the reward-consuming period. Notably, we discovered place fields mapped by VTA neurons, which disappeared or were reconstructed with changes in the path–outcome relationship. These results provide new insights into the VTA and its role in goal-directed navigation. Our designed and fabricated low-curvature microelectrode arrays can serve as a new device for precise deep brain implantation in the future.

Removal of the Metaphyseal Screw From Tension Band Constructs After Hemiepiphysiodesis: High Rates of Physeal Tethering and Subsequent Implant Removal.

Removal of the metaphyseal screw from tension band plate constructs after correction of angular deformity in patients treated with hemiepiphysiodesis has been suggested as an alternative to removing the plate and both screws. While this has the potential benefit of easier implant removal and reinsertion in the event of rebound, there is debate in the literature regarding the benefits and risks of leaving the epiphyseal screw and plate in place. Patients treated with hemiepiphysiodesis at the distal femur and/or proximal tibia with tension band plates and screws who underwent subsequent removal of the metaphyseal screw after correction were included. Charts and radiographs were reviewed for the need for metaphyseal screw reinsertion, subsequent removal of deep implants, and evidence of physeal tethering. Tethering was defined as progressive overcorrection in the treated bone segment after removal of the metaphyseal screw with the mechanical axis moving one full mechanical axis zone or more. Patients with tethering were compared with those without. A total of 215 patients with 387 limbs treated met inclusion criteria. Of those, 175 patients were treated for idiopathic genu valgum, while 40 were treated for other conditions. Fifty-nine individuals (27%) underwent replacement of the metaphyseal screw for repeat angular correction. Fifty-one percent of patients underwent secondary procedures for reasons other than metaphyseal screw reinsertion (74 symptomatic implant removal, 7 elective implant removal, 29 due to tethering). There were 44 cases of tethering in 36 patients (17%). In cases of tethering, 7 patients were treated with observation, 11 with implant removal only, 16 with hemiepiphysiodesis on the opposite side, and 2 with osteotomy. Patients with tethering were significantly younger, more likely to be male, and more likely to have had the metaphyseal screw removed more than once (P < 0.05). Removal of only the metaphyseal screw after hemiepiphysiodesis has high rates of tethering and further surgery for iatrogenic deformity correction and implant removal. This technique is not recommended. Therapeutic Level III, case-control study.

Optoplasmonic tuneable response by femtosecond laser irradiation of glass with deep-implanted gold nanoparticles

The manipulation of the optical properties of plasmonic nanocomposites is of high interest for the development of advanced optical devices with tailored unique properties. Achieving these objectives requires a combination of synthesis techniques and post-fabrication strategies. Here, we combine the use of two well-established physical strategies: MeV ion implantation and femtosecond laser processing. Firstly, we synthesize Au-doped soda lime glass nanocomposite through ion beam implantation (Au2+ at 1.8 MeV) followed by thermal annealing. This synthesis procedure results in a peculiar optical response based on the combination of Au-nanoparticle plasmonic resonance and a Fabry-Perot interference, caused by the deep implantation (centered at 480 nm). Secondly, this dual response is demonstrated to be highly tuneable by non-resonant femtosecond laser irradiation (800-nm wavelength and 130-fs pulse duration). Depending on the laser fluence, three transformation regimes are distinguished: supressing the interferometric response by spallative ablation, inducing vivid blue colors by surface swelling, and producing red-shifted color changes by multi-shot irradiation at low fluences. The proposed method is very versatile, since it is applicable to any dielectric matrix or implanted element. This work paves the way to a new route for the development of scalable and tuneable nanocomposites with several potential applications in optics.

Assessing post-TAVR cardiac conduction abnormalities risk using an electromechanically coupled beating heart.

Transcatheter aortic valve replacement (TAVR) has rapidly displaced surgical aortic valve replacement (SAVR). However, certain post-TAVR complications persist, with cardiac conduction abnormalities (CCA) being one of the major ones. The elevated pressure exerted by the TAVR stent onto the conduction fibers situated between the aortic annulus and the His bundle, in proximity to the atrioventricular (AV) node, may disrupt the cardiac conduction leading to the emergence of CCA. In this study, an in silico framework was developed to assess the CCA risk, incorporating the effect of a dynamic beating heart and preprocedural parameters such as implantation depth and preexisting cardiac asynchrony in the new onset of post-TAVR CCA. A self-expandable TAVR device deployment was simulated inside an electromechanically coupled beating heart model in five patient scenarios, including three implantation depths and two preexisting cardiac asynchronies: (i) a right bundle branch block (RBBB) and (ii) a left bundle branch block (LBBB). Subsequently, several biomechanical parameters were analyzed to assess the post-TAVR CCA risk. The results manifested a lower cumulative contact pressure on the conduction fibers following TAVR for aortic deployment (0.018MPa) compared to nominal condition (0.29MPa) and ventricular deployment (0.52MPa). Notably, the preexisting RBBB demonstrated a higher cumulative contact pressure (0.34MPa) compared to the nominal condition and preexisting LBBB (0.25MPa). Deeper implantation and preexisting RBBB cause higher stresses and contact pressure on the conduction fibers leading to an increased risk of post-TAVR CCA. Conversely, implantation above the MS landmark and preexisting LBBB reduces the risk.

Cerebral Microcirculation: Progress and Outlook of Laser Doppler Flowmetry in Neurosurgery and Neurointensive Care.

Laser Doppler flowmetry (LDF) is a well-established technique for the investigation of tissue microcirculation. Compared to skin, the use in the human brain is sparse. The measurement of cerebral microcirculation in neurointensive care and during neurosurgery is challenging and requires adaptation to the respective clinical setting. The aim of the review is to present state of the art and progress in neurosurgery and neurointensive care where LDF has proven useful and can find clinical importance in the investigation of cerebral microcirculation. The literature in the field is summarized and recent technical improvements regarding LDF systems and fiber optical probe designs for neurosurgical and neurocritical care described. By combining two signals from the LDF unit, the measurement of the microcirculation (Perfusion) and gray whiteness (TLI) of the brain tissue, the full potential of the device is achieved. For example, a forward-looking LDF-probe detects high-risk hemorrhage areas and gray-white matter boundaries along intraoperative trajectories during stereotactic neurosurgery. Proof of principles are given for LDF as a guidance tool in deep brain stimulation implantation, brain tumor needle biopsies, and as long-term monitoring device in neurocritical care. With well-designed fiber optical probes, surgical fixation, and signal processing for movement reduction, LDF monitoring of the cerebral microcirculation is successful up to 10 days. The use of LDF can be combined with other physiological measurement techniques, for example, fluorescence spectroscopy for identification of glioblastoma during tumor surgery. Fiber optics can also be used during magnetic resonance imaging (MRI). Despite the many advantages, fiber optical LDF has not yet reached its full potential in clinical neuro-applications. Multicenter studies are required to further evaluate LDF in neurosurgery and neurointensive care. In conclusion, the present status of LDF in neurosurgery and neurointensive care has been reviewed. By combining Perfusion and TLI with tailored probe designs the full potential of LDF can be achived in measuring cerebral microcirculation. This includes guidance during DBS implantation and needle biopsies, and long-term monitoring in neurocritical care.

Radiographic abnormalities and their clinical significance in patients with Parkinson disease who receive deep brain stimulation implants.

Preoperative MR images obtained in patients with Parkinson disease (PD) undergoing deep brain stimulation (DBS) often reveal incidental radiographic abnormalities (RAs). These findings range from small changes to gross pathologies. The effect of these findings on patients' clinical outcomes is unknown. The authors characterized RAs in patients with PD who underwent DBS and assessed clinical outcomes. Records of patients at the authors' institution with PD who underwent MRI for DBS electrode implantation from 2010 through 2022 were reviewed. RAs were identified from the official preoperative MRI reports. RAs were grouped into four general categories (ischemic changes, atrophy or degenerative changes [ADCs], structural abnormalities, and tumors) and correlated with clinical outcomes (including subjective clinical response, levodopa equivalent dose [LED], and Unified Parkinson's Disease Rating Scale Part III [UPDRS] score) at the 1-year and last available follow-ups. In this review, 160 patients were identified for initial analysis, with 135 presenting with ≥ 1 RAs. Of these 135 patients, 69.4% (111/160) had ischemic vascular changes, 39.4% (63/160) had ADCs, 16.9% (27/160) had structural changes, and 1.9% (3/160) had tumors. No differences in preoperative LED or UPDRS score were observed between these groups. After DBS, no differences in outcomes were observed between patients with RAs and those without RAs for both the 1-year and last follow-up time points, including mortality rates and times. Structural lesions were associated with lower mortality rates (OR 0.1, p = 0.04). ADCs were associated with a worse subjective clinical response at the 1-year (OR 0.50, p = 0.04) and last (OR 0.49, p = 0.03) follow-ups, but subjectively worse responses were not correlated with worse objective outcome measures. Most RAs have no significant effect on clinical outcomes in PD patients undergoing DBS. Generalized ADCs may be associated with poorer subjective responses and may warrant further discussion with the patient if diagnosed on preoperative MRI.

Pediatric Surgical Opioid Prescribing by Procedure, 2020-2021.

Surgery is one of the most common indications for opioid prescribing to pediatric patients. We identified which procedures account for the most pediatric surgical opioid prescribing. We conducted a cross-sectional analysis of commercial and Medicaid claims in the Merative MarketScan Commercial and Multi-State Medicaid Databases. Analyses included surgical procedures for patients aged 0 to 21 years from December 1, 2020, to November 30, 2021. Procedures were identified using a novel crosswalk between 3664 procedure codes and 1082 procedure types. For each procedure type in the crosswalk, we calculated the total amount of opioids in prescriptions dispensed within 3 days of discharge from surgery, as measured in morphine milligram equivalents (MMEs). We then calculated the share of all MMEs accounted for by each procedure type. We conducted analyses separately among patients aged 0 to 11 and 12 to 21 years. Among 107 597 procedures for patients aged 0 to 11 years, the top 3 procedures accounted for 59.1% of MMEs in opioid prescriptions dispensed after surgery: Tonsillectomy and/or adenoidectomy (50.3%), open treatment of upper extremity fracture (5.3%), and removal of deep implants (3.5%). Among 111 406 procedures for patients aged 12 to 21 years, the top 3 procedures accounted for 33.1% of MMEs: Tonsillectomy and/or adenoidectomy (12.7%), knee arthroscopy (12.6%), and cesarean delivery (7.8%). Pediatric surgical opioid prescribing is concentrated among a small number of procedures. Targeting these procedures in opioid stewardship initiatives could help minimize the risks of opioid prescribing while maintaining effective postoperative pain control.

Impact of Different Valve-in-Valve Positions on Functional Results of the New Generation of Balloon-Expandable Transcatheter Heart Valve.

Very precise positioning of the transcatheter heart valve (THV) inside the degenerated SAV is a crucial factor for valve-in-valve (ViV) procedure to achieve optimal hemodynamic results. Therefore, our study aimed to investigate the impact of implantation depth on functional results after ViV procedures in a standardized in vitro setting. THV (SAPIEN 3 Ultra 23-mm size) and three SAV models (Magna Ease, Trifecta, and Hancock II-all 21-mm size) were tested at different circulatory conditions in five different positions of the THV (2-6 mm) inside the SAV. Mean pressure gradient (MPG), effective orifice area (EOA), geometric orifice area (GOAmax), and pinwheeling index (PWImean) were analyzed. EOA and MPG of the THV did not differ significantly regarding the position inside the Magna Ease and the Hancock II (p > 0.05). However, EOA differed significantly, depending on the position of the THV inside Trifecta (2 vs. 5 mm; p = 0.021 and 2 vs. 6 mm; p < 0.001). The THV presented the highest EOA (2.047 cm2) and the lowest MPG (5.387 mm Hg) inside the Magna Ease, whereas the lowest EOA (1.335 cm2) and the highest MPG (11.876 mm Hg) were shown inside the Hancock II. Additionally, the highest GOAmax and the lowest PWImean of the THV were noticed inside the Magna Ease. The THV showed lower GOAmax and higher PWImean inside the Trifecta when placed in a deeper position. Deep implantation of the SAPIEN 3 Ultra inside the Trifecta correlates with impaired functional results. In contrast, the implantation position of the SAPIEN 3 Ultra inside the Magna Ease and the Hancock II did not have a significant effect on functional results.

Nonpalpable implant removals at centre of experience in France: a cohort study

Objective(s) Management and localisation strategies to remove nonpalpable contraceptive implants may be difficult. We aimed to evaluate our imaging modalities to identify deep implant and patient outcomes related to removal. Study design In this retrospective study, we reviewed all cases referred to our specialised centre for nonpalpable contraceptive implants from January 2018 to August 2022. Results Out of the cohort studied, 47 female subjects exhibited nonpalpable implants. The implant was nonpalpable for thirty-six patients (76,6%) immediately after the insertion whereas it was not palpable several months after the insertion for eleven patients (23.4%). Twelve patients (25.5%) had one or more failed removal attempts before referral. All 47 implants were successfully visualised via ultrasound in the upper arm: 40 implants (85.1%) were located in the subdermal tissue, 4 (8.5%) were intrafascial and 3 (6.4%) were intramuscular. Depth of the implant was 4.0 mm [1.7 − 12.0]. No clinical factors were statistically associated with differences in depth or location (subdermal vs subfascial). Removal procedures were mainly under local anaesthesia in 74.5% of cases in an outpatient setting. There were two Clavien-Dindo grade 1 complications (one case of cutaneous scar dehiscence and one transient postoperative neuropathic complaint in the upper arm resolved within 3 months under analgetics) Conclusions Identification of deep implants requires following the ultrasound modality protocol. Ultrasound detection makes easy and safe implant removal. Training programs for the insertion as well as for the removal of correct and incorrect inserted implants should be continued and developed all around the world.

The knowledge regarding the impacts and management of black triangles among dental professionals and laypeople

This study aimed to assess the knowledge regarding impacts, causes and management of black triangles (BT) among participants from different educational backgrounds including dental students, dentists and laypeople. This descriptive cross-sectional observational research included 435 participants who comprised 4 groups: pre-clinical (3rd year) dental students, clinical (4th and 5th year) dental students, dentists, and laypeople. A constructed self-reported questionnaire was utilized to assess participants’ demographic data and their knowledge of the impacts, causes and management of BT. The VAS scale was used to assess participants’ ratings for the impacts of BT on esthetics, with 0 meaning no impact and 10 meaning very severe negative impacts. The most reported treatments for BT were “cannot be treated” 99.3% and “non-surgical periodontal treatment” 67.1%. Meanwhile, the least reported was “modify the porcelain” 41.8%. The most reported cause of BT was “periodontal disease” 85.1%. However, the least reported were “parafunction” and “deep implants” 33.1% each. Dental professionals had better knowledge of the causes (t = 8.189, P < 0.001) and management (t = 8.289, P < 0.001) of BT than the non-dental participants. The dentists had the best knowledge, while the laypeople had the least knowledge of the causes (F = 62.056, P < 0.001) and treatment (F = 46.120, P < 0.001) of BT. The knowledge of the causes (t = 0.616, P = 0.538) and treatment (t = 1.113, P = 0.266) for BT was not significantly different between males and females. Age was not significantly related to the total knowledge about the causes (r = −0.034, P = 0.475) or treatment (r = −0.034, P = 0.482) for BT. Dental professionals had better knowledge of the impacts, causes and management of BT than the non-dental participants. The dentists were the best, while the laypeople were the worst in this regard. Age and gender had no relationships with the knowledge of causes or management of BT.

A New Design and Analysis for Metasurface-Based Near-Field Magnetic Wireless Power Transfer for Deep Implants

A New Design and Analysis for Metasurface-Based Near-Field Magnetic Wireless Power Transfer for Deep Implants

Screw Diameter and Use of a Washer Affect Symptomatic Implant Removal Rates in Pediatric Medial Epicondyle Fractures.

Medial epicondyle fractures are a common pediatric injury. When operative, cannulated partially threaded screws, with or without a washer, are commonly utilized. These implants may need to be removed after full healing if symptomatic. There is mixed evidence regarding the influence of a washer on rates of implant removal, and the influence of screw size has not been studied. We aim to determine the rate of symptomatic deep implant removal for each fixation type and identify factors associated with the need for removal. This was an IRB-reviewed, retrospective, case-cohort study. Patients treated at our institution between January 1, 2004 and December 31, 2019, age 18 years old or younger, with a medial epicondyle fracture managed operatively with 4.0 or 4.5mm cannulated screws with or without washers were included. Patients with multiple operative ipsilateral elbow fractures and those who underwent implant removal for reasons other than pain or irritation were excluded. Removal rates were compared between screw sizes (4.0 vs 4.5mm), as well as with and without a washer using a Cox proportional hazards model. In total, 151 patients met the inclusion criteria, 54 with symptomatic hardware removed and 97 without symptomatic hardware removed. A significantly higher number of patients treated with 4.5mm screws compared with 4.0mm screws underwent removal of symptomatic deep implants (50% vs 30%, P = 0.033). In a multivariable Cox regression model adjusting for age and ulnar nerve status, when no washer was used, the hazard ratio (HR) for symptomatic hardware removal for 4.5mm screws was 2.92 times the HR for 4.0mm screws (95% CI: 1.35-6.29). When a 4.0mm screw was used, the HR for symptomatic hardware removal for a washer was 3.24 times the HR without a washer (95% CI: 1.53-6.84). Implant removal rates are influenced by screw size and the use of a washer. These results may help guide implant choice and counsel families regarding the rate of symptomatic implant removal. Level III-therapeutic level, case-control study.

Prefrontal-subthalamic theta signaling mediates delayed responses during conflict processing

While medial frontal cortex (MFC) and subthalamic nucleus (STN) have been implicated in conflict monitoring and action inhibition, respectively, an integrated understanding of the spatiotemporal and spectral interaction of these nodes and how they interact with motor cortex (M1) to definitively modify motor behavior during conflict is lacking. We recorded neural signals intracranially across presupplementary motor area (preSMA), M1, STN, and globus pallidus internus (GPi), during a flanker task in 20 patients undergoing deep brain stimulation implantation surgery for Parkinson disease or dystonia. Conflict is associated with sequential and causal increases in local theta power from preSMA to STN to M1 with movement delays directly correlated with increased STN theta power, indicating preSMA is the MFC locus that monitors conflict and signals STN to implement a ‘break.’ Transmission of theta from STN-to-M1 subsequently results in a transient increase in M1-to-GPi beta flow immediately prior to movement, modulating the motor network to actuate the conflict-related action inhibition (i.e., delayed response). Action regulation during conflict relies on two distinct circuits, the conflict-related theta and movement-related beta networks, that are separated spatially, spectrally, and temporally, but which interact dynamically to mediate motor performance, highlighting complex parallel yet interacting networks regulating movement.

Irregularity of instantaneous gamma frequency in the motor control network characterize visuomotor and proprioceptive information processing

Objective. The study aims to characterize movements with different sensory goals, by contrasting the neural activity involved in processing proprioceptive and visuo-motor information. To accomplish this, we have developed a new methodology that utilizes the irregularity of the instantaneous gamma frequency parameter for characterization. Approach. In this study, eight essential tremor patients undergoing an awake deep brain stimulation implantation surgery repetitively touched the clinician’s finger (forward visually-guided/FV movement) and then one’s own chin (backward proprioceptively-guided/BP movement). Neural electrocorticographic recordings from the motor (M1), somatosensory (S1), and posterior parietal cortex (PPC) were obtained and band-pass filtered in the gamma range (30–80 Hz). The irregularity of the inter-event intervals (IEI; inverse of instantaneous gamma frequency) were examined as: (1) auto-information of the IEI time series and (2) correlation between the amplitude and its proceeding IEI. We further explored the network connectivity after segmenting the FV and BP movements by periods of accelerating and decelerating forces, and applying the IEI parameter to transfer entropy methods. Main results. Conceptualizing that the irregularity in IEI reflects active new information processing, we found the highest irregularity in M1 during BP movement, highest in PPC during FV movement, and the lowest during rest at all sites. Also, connectivity was the strongest from S1 to M1 and from S1 to PPC during FV movement with accelerating force and weakest during rest. Significance. We introduce a novel methodology that utilize the instantaneous gamma frequency (i.e. IEI) parameter in characterizing goal-oriented movements with different sensory goals, and demonstrate its use to inform the directional connectivity within the motor cortical network. This method successfully characterizes different movement types, while providing interpretations to the sensory-motor integration processes.

Thalamic segmentation based on diffusion tensor imaging in patients with trigeminal neuralgia

Classical trigeminal neuralgia (CTN) refers to episodic pain that is strictly confined to the trigeminal distribution area, and the thalamus is an important component of the trigeminal sensory pathway. Probabilistic tracking imaging algorithm was used to identify specific connections between the thalamus and the cortex, in order to identify structural changes in the thalamus of patients with CTN and perform thalamic segmentation. A total of 32 patients with CTN and 32 healthy controls underwent DTI-MRI scanning (3.0 T). Differences in fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD) and mean diffusivity (MD) between the groups were studied. Correlation analysis was performed with clinical course and pain level. Compared to the healthy controls, patients in the CTN group had significantly reduced FA, increased AD, RD and MD in somatosensory subregion of the bilateral thalamus, increased RD in frontal subregion, increased RD and MD in motor subregion. Correlation analysis showed that patient history was positively correlated with pain grading, and that medical history was positively correlated with significantly reduced FA in somatosensory subregion, negatively correlated with increased RD and MD in motor subregion. We used DTI-based probabilistic fiber tracking to discover altered structural connectivity between the thalamus and cerebral cortex in patients with CTN and to obtain a thalamic segmentation atlas, which will help to further understand the pathophysiology of CTN and serve as a future reference for thalamic deep brain stimulation electrode implantation for the treatment of intractable pain.