Expandable Device Research Articles

Expandable Interbody Cages for Lumbar Spinal Fusion. A Systematic Review.

Since the early 2000s, various expandable spinal fusion cages have been developed to facilitate less invasive procedures, however, expandable cages have often been evaluated as a homogeneous group, neglecting differences in shape, size, material, expandability and lordotic adjustability. This systematic review aimed to comprehensively survey the literature on expandable spinal fusion cages, discuss their differentiating factors, and identify gaps in the literature regarding these devices. To demonstrate the range of design features included in expandable interbody devices and identify which of these features are associated with improved surgical outcomes. Systematic review. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. An electronic search of MEDLINE and Embase using the search terms "lumbar" AND "fusion" AND ("expandable cage" OR "expandable interbody") including only English language articles that contained sufficient detail to correlate a specific expandable cage design to patient outcomes. Relevant elements, including device design parameters, patient population information, details of the intervention, comparison data, outcome variables, and the timeframe were extracted. Statistical analysis was conducted to correlate patient outcomes with different device features. While 387 different articles were initially identified, 49 met all the criteria for inclusion. Design differences contributed to disparate outcomes, with rectangular titanium cages featuring medial-lateral and vertical expansion and continuous lordotic adjustability being correlated with significantly improved patient-reported outcomes. The surgical approach and location were also found to be correlated with patient outcomes, indicating that confounding factors are present. We recommend that expandable cage technologies not be considered a homogenous group, as long-term outcomes likely are dependent upon specific design characteristics. Categorizing devices based on design features such as material composition, shape, vertical expandability, horizontal expandability, and restoration of segmental lordosis may allow for more rapid identification of device characteristics associated with better outcomes.

Comparison of the Effects of Different Palatal Morphology on Maxillary Expansion via RME and MSE: A Finite Element Analysis.

This study aims to compare and analyze the biomechanical effect and the displacement trend of RME and MSE on the maxillofacial complex under different palatal shapes by using finite element analysis. The three-dimensional model of maxillofacial complex was obtained from a computed tomography image of a person with a normal palate. Then, we modified the shape of the palate to obtain the model with a high palate. Additionally, two expander devices were considered. MSE and RME were created and four models were made: Model 1: Normal-palate craniomaxillofacial complex with RME expander; Model 2: Normal-palate craniomaxillofacial complex with MSE expander; Model 3: High-palate craniomaxillofacial complex with RME expander; Model 4: High-palate craniomaxillofacial complex with MSE expander. Then, lateral forced displacement was applied and the analysis results were obtained. The lateral displacement of the palatal suture of Model 3 is greater than that of Model 1, and the maxilla has more rotation. The crown/root ratio of Model 1 is significantly greater than that of the other three groups. Compared with Model 1, Model 3 has greater stress concentration in the superstructure of the craniomaxillofacial complex. Both of them have greater stress in the anchorage area than Model 2 and Model 4. Different shapes of the palate interfere with the effects of RME and MSE, and its influence on the stress distribution and displacement of the craniomaxillary complex when using RME is greater than MSE. The lateral displacement of the palatal suture of MSE is significantly larger than that of RME. It is more prone to tipping movement of the anchor teeth using RME under normal palate, and MSE may manage the vertical control better due to the smaller crown/root ratio than RME and intrusive movement of molars.

Fabrication of 3D printed mutable drug delivery devices: a comparative study of volumetric and digital light processing printing.

Mutable devices and dosage forms have the capacity to dynamically transform dimensionally, morphologically and mechanically upon exposure to non-mechanical external triggers. By leveraging these controllable transformations, these systems can be used as minimally invasive alternatives to implants and residence devices, foregoing the need for complex surgeries or endoscopies. 4D printing, the fabrication of 3D-printed structures that evolve their shape, properties, or functionality in response to stimuli over time, allows the production of such devices. This study explores the potential of volumetric printing, a novel vat photopolymerisation technology capable of ultra-rapid printing speeds, by comparing its performance against established digital light processing (DLP) printing in fabricating hydrogel-based drug-eluting devices. Six hydrogel formulations consisting of 2-(acryloyloxy)ethyl]trimethylammonium chloride solution, lithium phenyl-2,4,6-trimethylbenzoylphosphinate, varying molecular weights of the crosslinking monomer, poly(ethylene glycol) diacrylate, and paracetamol as a model drug were prepared for both vat photopolymerisation technologies. Comprehensive studies were conducted to investigate the swelling and water sorption profiles, drug release kinetics, and physicochemical properties of each formulation. Expandable drug-eluting 4D devices were successfully fabricated within 7.5s using volumetric printing and were shown to display equivalent drug release kinetics to prints created using DLP printing, demonstrating drug release, swelling, and water sorption properties equivalent to or better than those of DLP-printed devices. The reported findings shed light on the advantages and limitations of each technology for creating these dynamic drug delivery systems and provides a direct comparison between the two technologies, while highlighting the promising potential of volumetric printing and further expanding the growing repertoire of pharmaceutical printing.

Real-world uptake of an innovative pupil expander device for cataract surgery: Implementation lessons learnt.

Cataract surgery in the eyes, where the pupil does not dilate despite using eye drops, is fraught with vision-threatening complications. About 11 per cent of eyes undergoing cataract surgery have non-dilating, small pupils. The increasing prevalence of benign prostatic hyperplasia (BPH), hypertension, diabetes and medications used for the same are the contributing factors. The recent Food and Drug Administration (FDA) approval for the use of miotic agents in the treatment of presbyopia will lead to a further rise in the number of non-dilating pupils. While pharmacological agents and other methods have been used, mechanical pupil expander devices are the only fail safe option. However, available devices had a steep learning curve and limitations which made them difficult to use, unpredictable and unsafe. With its patented single plane, hexagonal, notches and flanges design, the US FDA registered B-HEX Pupil Expander (Med Invent Devices Pvt. Ltd., India) overcame these limitations and fulfilled an unmet need. The B-HEX is machinable, rapidly produced, consistent, easy to use, safe, and affordable. Despite such advantages, implementation hurdles have restricted its availability to healthcare systems worldwide. Peer acceptance has been steadily growing, with the B-HEX becoming the market leader in India, as evidenced by numerous publications, videos and papers presented at international conferences and comments from opinion leaders endorsing its use. However, impractical regulatory requirements and resource constraints remain a great impediment to the global distribution of this novel invention. This has denied many patients the benefits of a superior and more affordable option. Though value continues to be added to the B-HEX by maintaining a strong intellectual property portfolio with internationally granted Patents and Trademark, increasing its user base, and garnering support from key opinion leaders, only a collaboration with the right partner will help scale up the global reach and make it a leader in the global market.

Expandable Screws Can Increase Fixation Strength But Can They Be Removed? An in-vivo Sheep Study Demonstrating Removal Of A Novel Expandable Screw

Screw fixation failures remain clinically challenging especially hip fracture fixation in osteoporotic bone. Prior studies have shown that expandable orthopaedic screw devices can improve biomechanical fixation in bone, but concerns over their removability remains. A novel expandable screw implant has been developed that optimizes both implant fixation and removability. The present study investigated the implant removability in an animal model. A specially manufactured expandable screw implant was surgically implanted in 5 sheep for 4 months. The distal femur were extracted with the implants in-situ after euthanasia. The bone samples were scanned using micro-CT and the retraction torque of the expandable screw wings were measured to assess ease of removability. Analysis of the micro-CT images verified that bone had not grown inside the expandable screw mechanism and all expandable screw samples were removed without complication. The mean peak torque to fully retract the screws ready for removal was 0.86 Nm (0.59-1.30 Nm) and the mean peak removal torque for the retracted screws was 7.98 Nm (1.70-15.40 Nm). This large animal study result shows the feasibility of an expandable screw concept with a novel gapless design, to improve screw fixation strength mechanically, without compromising on the implant removability.

Comparison of the Haas Expander and the Elastodontic Device for the Resolution of Transverse Discrepancies in Growing Patients: A Single-Centre Observational Study

Background: This study aimed to compare the clinical outcomes of using two different devices to treat upper palatal discrepancies evaluated with a digital intraoral scanner. Methods: A total of 64 patients were enrolled and treated with either an elastodontic expansion device (32 patient test group, 16 females and 16 males, mean age 7.08 ± 0.44) or Haas expander (32 patient control group, 16 females and 16 males, mean age 7.32 ± 0.50). The two groups exhibited similar orthodontic features. The orthodontic criteria were: skeletal class I relationship; molar class I relationship; complete eruption of upper sixths; presence of unilateral or bilateral cross bite. All dental casts were examined and subsequently scanned with an intraoral scanner (I-Tero) pre-treatment (T0) and 12 months after the onset of therapy (T1) to assess the distance between the decidous upper canines (ICW, intercanine width) and the distance between the mesiopalatal cusps of the upper first molars (IMW, intermolar width). For statistical analysis, the t-test for continous variables and the chi-square test for categorical variables were used, respectively. Results: There were no statistically significant differences between the mean and SD of the expansions that resulted from the Haas expander and the elastodontic devices (Haas expander vs. Eptamed: ICW_T1 (Haas) = 42.34 (3.09), ICW_T1 (Eptamed) = 42.69 (2.77); p = 0.743; IMW_T1 (Haas) = 34.22 (2.29), IMW_T1 (Eptamed) = 34.00 (2.56); p = 0.800). The two devices were similarly effective. Conclusions: Elastodontic devices and the Haas expander can successfully help the orthodontist to conduct upper arch expansion treatment. However, elastodontic devices are more comfortable during the resolution of palatal discrepancies compared to palatal expander devices.

LIFETIME MANAGEMENT OF AORTIC STENOSIS IN EXTREME SETTING

Abstract A 51–year–old male patient returned to our attention due to symptomatic severe aortic stenosis. Despite the severity of the aortic valve disease, he had been previously turned down from aortic valve replacement by us because of lack of symptoms and very unfavorable anatomy. Indeed he had been irradiated at the age of 3 due to Hodgkin’s Lymphoma and presented with porcelain aorta, small ascending aorta and aortic annulus. The patient returned to us with a 3–month history of progressive dyspnea (NYHA class IIa) and one episode of lipothymia during physical exercise. Physical examination, hematologic and biochemical investigations at admission were normal. Our trans–thoracic echocardiogram confirmed a trileaflet aortic valve (AV) that was severely stenotic and calcified with a mean gradient of 60 mmHg and an AV area of 0.5 cm2 (0.3 cm2/m2), in presence of good left ventricular systolic function with an ejection fraction (EF) of 60%. CT excluded coronary disease but, confirmed severe calcified aortic stenosis and porcelain aorta with small calcific sino–tubular junction and ascending aorta and protruding LVOT calcium. (Ascending aorta 19 mm; STJ 19 mm). The heart–team judged the patient not suitable for AVR and decided to perform a high–risk TAVI, leaving apical conduit as the last resort. From a technical standpoint, the LVOT calcium and the short and narrow STJ were high risk features for rupture with balloon expandable devices. On the other hand the short and narrow STJ with the narrow ascending aorta would represent a serious issue for the expansion of self–expanding devices and an even more troublesome feature for future coronary access and coronary occlusion in the setting of TAVI–in–TAVI down the road. Given the patient’s young age, a balloon expandable SAPIEN ultra 23 mm was chosen to be implanted with a two–step inflation to minimize the risk of STJ rupture. The prosthesis was partially expanded until anchoring was achieved on the aortic leaflets then, on continuous pacing, the balloon was rapidly collapsed, pushed down deeper under the STJ and fully inflated to achieve prosthesis’ inflow expansion. Intra–procedural and post–procedural course were uneventful and the patient was discharged home in 5th Day. Transthoracic echocardiogram at the dismission reveal a trans–aortic mean gradient of 18 mmhg, the absence of significant paravalvular leaks and a preserved ejection fraction. Pre–discharge CT scan confirmed feasibility of future TAVI–in–TAVI in case of need.

Multivariate Analysis of Risk Factors for Complications in Pediatric Tissue Expansion.

Tissue expanders represent one of the main surgical options for skin reconstruction in cases of tumors, traumalike burn injury, scar contracture, and alopecia. However, the tissue expander device is also associated with complications such as infection and extrusion. The aim of this study was to analyze risk factors for major complications of use of tissue expanders in pediatric patients using multivariate analysis. A retrospective, single-center observational study was performed over 10 years in pediatric patients who were treated with tissue expanders for tumors, nevus, scars, burn reconstruction, and alopecia from April 2012 to March 2022. The primary outcome was overall complications per operation and expander, including infection and extrusion. Ten predictor variables were included as risk factors based on previous studies and as new factors considered important from clinical experience. Univariate and multivariate logistic regression analyses were performed to identify risk factors for major complications such as expander infection or extrusion. The study included 44 patients who underwent 92 operations using 238 tissue expanders. The overall complication rate per expander was 14.3%. Univariate logistic regression analysis identified associations of younger age, number of expanders used per operation, history of infection, and tissue expander locations with a higher complication rate. In multivariate logistic regression analysis, younger age (odds ratio, 1.14; P = 0.043) was associated with a high likelihood of expander complications. Younger age is an independent risk factor for tissue expander complications in pediatric patients. This factor should be considered in preoperative planning and discussions with the patient's family.

Cu-doped Sb-Zn alloy anodes tailored by novel pulse electrodeposition achieving robust sodium storage

Sodium-ion batteries (SIBs) have garnered significant attention as cost-efficient and expandable energy conversion devices. Nonetheless, their further utilization is impeded by the rapid deterioration in the capacity of anode materials during cycling. Herein, we have successfully introduced both active (Zn) and non-active (Cu) metal components into Sb by fabricating Cu-doped Sb-Zn (SZC-N) anodes through a template-free novel pulse potential electrodeposition (NPPED) approach. The introduction of Cu demonstrated a crucial role in directing the formation of the uniform structure. On the other hand, active “Zn” increases overall capacity and serves as a cushion against the volume expansion of Sb. Notably, the SZC-N exhibits enhanced charge diffusion while maintaining the structural integrity of the electrode, making it a promising choice for SIBs. Interestingly, the SZC-N electrode demonstrated remarkable cycling and rate performance, manifesting an excellent reversible capacity of 380.9 mAh·g−1 after 250 cycles, with an outstanding capacity retention of 80 % when operated at 1 C. Furthermore, it achieved a noteworthy capacity of 454.1 mAh·g−1 at a high current density of 10 C. In contrast, both the SZC-R and SZ-C anodes only yielded 52.9 and 3.9 mAh·g−1 (after 250 cycles), moreover, delivering inferior rate performance. The increased cyclic performance of the SZC-N electrode can be ascribed to the presence of a Cu network, which facilitates charge transport and promotes the stabilization of the electrode structure. The findings suggest that binder-free anode materials produced through the NPPED method present a promising opportunity for SIBs.

Anterior Cervical and Upper Thoracic Column Reconstruction Using an Expandable Poly-Ether-Ether-Ketone Vertebral Body Replacement: A Retrospective Single Center Cohort Analysis

This study aimed to evaluate the safety and efficacy of a novel Poly-Ether-Ether-Ketone (PEEK) expandable vertebral body replacement (VBR) for anterior cervico-thoracic vertebral column reconstruction in patients with metastatic, traumatic, or degenerative diseases. Radiographic and clinical outcomes, as well as complication rates, were analyzed in a retrospective analysis of 28 patients (61 ± 13 years; 64% female) who underwent an anterior cervical corpectomy and fusion (ACCF) with the Expandable Corpectomy Device (ECD) from DePuy/Synthes (2011–2020). Correction of the bisegmental kyphotic angle (BKA) was chosen as the primary outcome. Bony fusion, loss of device height, and implant subsidence were evaluated additionally. Clinical outcome was assessed using Odom’s criteria, the numerical pain rating scale (NRS), the American Spinal Injury Association Impairment Scale (AIS), and the Karnofsky Performance Status Scale (KPSS). Our study found a significant improvement in the BKA (12.3° ± 9.6°; p = 0.0002) at the last follow-up with no statistically relevant loss of device height (p = 0.96) or implant subsidence (p = 0.99). Successful bony fusion was observed in all patients. The KPSS significantly improved in patients with a tumorous disease at the time of discharge (p = 0.0009), and the sensation of pain showed significant improvement at six months post-operatively and at the final follow-up (p = 0.004; p = 0.021). However, four patients needed further secondary posterior stabilization, and one ECD was explanted due to a severe surgical site infection after an accidental esophageal lesion. In conclusion, the ECD proofed the radiographic stability for the anterior column reconstruction of the cervico-thoracic spine with significantly improved clinical outcome.

Angular spectrum method for simulation and analysis of ground glass produced laser speckle pattern

The feature size of holographic diffuser is an important parameter which affects the display resolution when the holographic diffuser is used as an exit-pupil expander device in head up display. However, there is currently a lack of relevant research work on it. Here, we derive the amplitude and phase properties of the scattering light based on a statistical model of the surface undulations of ground glass. Combining with angular spectrum diffraction theory, a method for accurately simulating the speckle pattern is developed. The speckle patterns in the far-field and near-field diffraction areas of light passing through ground glass is calculated, then compared with estimation and experimental results. The comparison shows that the speckle feature size obtained by the traditional estimation method is quite different from the experimental results in the nearfield diffraction area. While the results obtained by our simulation method is in good agreement with the experiment in both near-field and far-filed diffraction areas. This work provides an effective method for the design and preparation of small feature size holographic diffuser elements.

Power Generation at Low Temperatures Using Thermoelectric Generators and Cost Analysis

Interest in thermoelectric generators (TEGs) for waste heat recovery (WHR) and geothermal energy has grown significantly in recent years due to the ability to convert low‐grade thermal energy into electricity, which is essential to reduce carbon emissions. One of the main challenges in TEG power generation is the expandability and the number of layers in TEG devices. The currently reported maximum number of layers is six. In this study, the expandable TEG devices with different number of layers, up to 20, were designed and manufactured. The field tests have been then conducted with these TEG devices using the waste heat from a coal bed methane power plant at a temperature of around 80°C. To our best knowledge, this is the lowest temperature at which TEG field tests have been implemented. At a flow rate of about 3 m3/hr, a TEG unit with a volume of about 3 m3 can generate a power of 15 kW at a temperature difference of 60°C. The power density and power per unit area of the TEG are investigated and compared to those of diesel generators and photovoltaic panels at different temperature differences. Furthermore, to offer guidance for the commercial‐scale implementation of TEG, we have estimated the fabrication and installation costs, as well as the levelized cost of electricity, across various temperature differences. The results indicate that TEG is a feasible and promising technology for large‐scale power generation and WHR.

Effect of different palatal expanders with miniscrews in surgically assisted rapid palatal expansion: A non-linear finite element analysis.

Surgically assisted rapid palatal expansion (SARPE) has been the treatment of choice in subjects presenting skeletally mature sutures. The purpose of this study was to analyze stress distribution and displacement of the craniofacial and dentoalveolar structures resulting from three types of palatal expanders with surgical assistance using a non-linear finite element analysis. Three different palatal expanders were designed: Model-I (tooth-bone-borne type containing four miniscrews), Model-II (tooth-bone-borne type containing two miniscrews), and Model-III (bone-borne type containing four miniscrews). A Le Fort I osteotomy was performed, and a total of 5.0 mm palatal expansion was simulated. Nonlinear analysis (three theory) method (geometric nonlinear theory, nonlinear contact theory, and nonlinear material methods) was used to evaluate stress and displacement of several craniofacial and dentoalveolar structures. Regardless of the maxillary expander device type, surgically assisted rapid palatal expansion produces greater anterior maxillary expansion than posterior (ANS ranged from 2.675 mm to 3.444 mm, and PNS ranged from 0.522 mm to 1.721 mm); Model-I showed more parallel midpalatal suture opening pattern - PNS/ANS equal to 54%. In regards to ANS, Model-II (1.159 mm) and Model-III (1.000 mm) presented larger downward displacement than Model-I (0.343 mm). PNS displaced anteriorly more than ANS for all devices; Model-III presented the largest amount of forward displacement for PNS (1.147 mm) and ANS (1.064 mm). All three type of expanders showed similar dental displacement, and minimal craniofacial sutures separation. As expected, different maxillary expander designs produce different primary areas and levels of stresses (the bone-borne expander presented minimal stress at the teeth and the tooth-bone-borne expander with two miniscrews presented the highest). Based on this finite element method/finite element analysis, the results showed that different maxillary expander designs produce different primary areas and levels of stresses, minimal displacement of the craniofacial sutures, and different skeletal V-shape expansion.

Transforaminal lumbar interbody fusion with an expandable interbody device: Two-year clinical and radiographic outcomes

BackgroundThe use of interbody cages as an adjunct to lumbar spinal fusion remains an important technique to enhance segmental stability, promote solid arthrodesis, maintain neuroforaminal decompression, and preserve/improve segmental lordosis. Appropriate segmental lumbar lordosis and sagittal balance is well-known to be critical for long-term patient outcomes. This study sought to evaluate the radiographic and clinical results of TLIF in patients using an articulating, expandable cage. Primary endpoint was clinical and radiographic outcomes, including complications, at 12 and 24 months. MethodsA total of 37 patients underwent open single-level or 2-level TLIF by a single surgeon using an expandable cage with concomitant bilateral pedicle screws and posterolateral arthrodesis. Clinical outcomes included ODI and VAS for back and legs. Radiographic outcomes included pelvic incidence and tilt, lumbar and segmental lordoses, and disc height at the operative level(s). All outcomes were collected at baseline, 2-weeks, 6-weeks, 3-months, 6-months, 12-months, and 24-months postop. ResultsA total of 28 patients were available for analysis. Nine patients failed to follow-up at 24 months. Mean ODI scores showed significant improvement, from pre-to-postoperative at 24 months (55%; p<.0001). VAS for back and legs was significantly lower at 24 months on average by 72 and 79%, respectively (p<.0001 for both). Both segmental and lumbar lordoses significantly improved by 5.3° and 4.2° (p<.0001 and p=.049), respectively. Average disc height improved by 49% or 6.1 mm (p<.001). No device-related complications nor instances of measured subsidence. One patient had a superficial infection, and another had an intraoperatively repaired incidental durotomy. ConclusionsThe use of an expandable cage contributed to improvement in both segmental and lumbar lordosis with no reported complications at 24-month follow-up. All clinical measures significantly improved as well. The expandable cage design represents an effective and safe option to increase cage size and allow significant segmental lordosis correction.

Design and Biomechanical Evaluation of a Bidirectional Expandable Cage for Oblique Lateral Interbody Fusion

Oblique lateral interbody fusion (OLIF) surgery is a minimally invasive spinal surgery technique that has become increasingly popular in recent years. The primary objective of the current study was to design a minimally invasive expandable fusion device that can reduce iatrogenic nerve damage and minimize endplate damage during OLIF surgery, while restoring intervertebral height and alignment. The second objective was to use finite element analysis to evaluate the biomechanical stability of the newly designed expandable fusion device after implantation into the intervertebral space. A new bidirectional expandable cage was designed in this study. A finite element model (FEM) of L3-L5 lumbar segment was modified to simulate decompression and fusion. The modified FEMs were constructed in the following cases: intact model, bidirectional expandable cage (alone, with unilateral pedicle screws [UPSs], and with bilateral pedicle screws [BPSs]) model, conventional OLIF cage (alone, with UPSs, and with BPSs) model. To simulate physiological loadings, the models were subjected to a follower compressive pre-load of 400 N, in addition to 8.0 Nm of flexion, extension, lateral bending, and axial rotation moments. All modified FEMs exhibited a significant reduction in motion at L3-L5 compared to the intact model. Among the fusion models, the bidirectional expandable cage (BEC) with BPS model displayed the highest stiffness and demonstrated a reduced range of motion (48.5%-75.7%). Additionally, the peak stress on the endplate in the conventional OLIF cage (Conv-OLIF) model was generally lower than that in the BEC models. The cage in the BEC ALONE model exhibited the highest stress (93.87-176.3 MPa) on the endplate in most motion modes, while the cage in the Conv-OLIF+BPS model had the lowest stress (16.67-30.58 MPa) on the endplate in most motion modes. The maximum stress on the fixation in the BEC fusion models was generally lower than that in the Conv-OLIF fusion group under the same loading conditions. The OLIF ALONE model had the lowest stress on the adjacent disc, while the stress level in the BEC ALONE model was very close to it. The BEC implanted models had higher stiffness, and more proper stress distribution on the posterior fixation was comparable to that of the Conv-OLIF models. However, the endplate stress peaks and cage stress peaks of the BEC models were slightly higher than those of the Conv-OLIF models, though still within a clinically acceptable range. Taking into account both biomechanical and clinical perspectives, BEC-assisted unilateral pedicle screw fixation meet clinical demand and may serve as a viable alternative to Conv-OLIF fusion.

Maxillary expansion in nongrowing patients. Conventional, surgical, or miniscrew-assisted, an update.

Maxillary transverse deficiency can occur in various clinical dentoskeletal deformities and include unilateral or bilateral posterior crossbite, narrow, tapering, or high palatal arch. The development of temporary anchorage devices led to a new generation of tooth-bone-borne expansion appliance using two or four screws to apply the mechanical forces to the bone and reduce the stress to the anchored teeth. The aim of these new devices is to reduce the adverse dentoalveolar effect and achieve more skeletal expansion than conventional tooth-borne rapid palatal expansion. This article reviews the age limitation and complication and soft tissue change of nonsurgical maxillary expansion. We discuss the approach of surgical maxillary expansion with maxillary skeletal expander device. The clinical case will show the benefit of nonsurgical and surgical tooth-bone-borne rapid palatal expansion.

Determination of the load bearing capacity of pre-stressed expandable props for ground support in underground mines

This paper aims to determine the load bearing capacity of pre-stressed expandable props with different geometries and load eccentricities for flexible support in underground mining or excavation. It is deduced that the expandable device could have much higher strength (>89 MPa) by laboratory tests, and the load bearing capacity of the expandable prop may depend on the stability of the supporting steel pipe structure. A good agreement was found between the laboratory test and numerical results in terms of the load bearing capacity and the final macro-bending failure pattern for expandable props with heights of 1.5 and 2.7 m, and the theoretical calculation for the strength of traditional steel structures is not directly suitable for the expandable props. Moreover, additional numerical simulations were performed for the expandable props with different normalized slenderness ratios λn and loading eccentric distances e. The variation of stability coefficient of the expandable prop is in line with the Perry-Robertson equation and its correlation coefficients are fitted as a of 0.979 and b of 0.314. For estimating the load bearing capacity of the expandable props, the strength equation for traditional steel structures is improved by introducing a bending magnification factor and by modifying the normalized slenderness ratio to a converted slenderness ratio. Based on the underground field monitoring for the strength of expandable props with different heights, the empirical eccentric distances were back calculated, and a safety factor is introduced to obtain the designed strength of the expandable prop. In addition, a four-step design procedure is proposed for the expandable prop.

Villi Inspired Mechanical Interlocking for Intestinal Retentive Devices.

Intestinal retentive devices have applications ranging from sustained oral drug delivery systems to indwelling ingestible medical devices. Current strategies to retain devices in the small intestine primarily focus on chemical anchoring using mucoadhesives or mechanical coupling using expandable devices or structures that pierce the intestinal epithelium. Here, the feasibility of intestinal retention using devices containing villi-inspired structures that mechanically interlock with natural villi of the small intestine is evaluated. First the viability of mechanical interlocking as an intestinal retention strategy is estimated by estimating the resistance to peristaltic shear between simulated natural villi and devices with various micropost geometries and parameters. Simulations are validated in vitro by fabricating micropost array patches via multistep replica molding and performing lap-shear tests to evaluate the interlocking performance of the fabricated microposts with artificial villi. Finally, the optimal material and design parameters of the patches that can successfully achieve retention in vivo are predicted. This study represents a proof-of-concept for the viability of micropost-villi mechanical interlocking strategy to develop nonpenetrative multifunctional intestinal retentive devices for the future.

Three-dimensional analysis of miniscrew position changes during bone-borne expansion in young and late adolescent patients

IntroductionMaxillary expansion in patients at the end of their growth relies on the possibility to use miniscrew supported expanders to apply expansion forces directly to the midpalatal suture. Although miniscrews provide a stable anchorage unit, several studies have reported that they do not remain in exactly the same position during treatment. The aim of the present study was to analyze miniscrew position changes after the expansion using bone-borne appliances in late adolescent patients.MethodsNineteen patients (13 females, 6 males), with a mean age of 17.81 (SD = 4.66), were treated with a Bone-Borne Expander Device. The appliance was designed with 4 miniscrews: 2 in the anterior palatal area, at the third rugae level; 2 in the posterior area. A CBCT and an intraoral scan were obtained before treatment (T0), and then, a second CBCT was obtained after the expansion (T1). Data on peri-suture bone thickness were collected at T0, then the CBCTs were superimposed, and changes between mini-screws position on T0 and T1 were evaluated, both by linear and angular displacements.ResultsSignificant longitudinal differences were found in the distance of the head and the tip of miniscrews measured at the occlusal plane, as well as angular changes. Correlations between displacement measurements and peri-suture bone thickness and height measurements were found as well.ConclusionsWhile acting as bone anchor units, miniscrews do not remain in the same position during bone-borne expansion. The amount of displacement was related to peri-sutural total bone height and cortical thickness, especially in the anterior area of the naso-frontal maxillary complex.

Safety and Effectiveness of Expandable Intravertebral Implant Use for Thoracolumbar Burst Fractures

PurposeTo determine the safety and effectiveness of an expandable intravertebral implant (Spinejack; Stryker, Kalamazoo, Michigan) as a treatment option for patients with thoracolumbar spine burst fractures without fracture-related neurologic deficit. Materials and MethodsImaging studies before and after expandable intravertebral implantation and medical records of 33 patients, 11 (33.3%) men and 22 (66.6%) women with an overall mean age of 71.7 years ± 8.3, were reviewed for 60 thoracolumbar Magerl Type A3 injuries secondary to osteoporosis, trauma, or malignancy. The mean follow-up time was 299 days. ResultsImplantation of an expandable intravertebral device resulted in a statistically significant reduction in bone fragment retropulsion (mean ± SD, 0.64 mm ± 16.4; P < .001), reduction in the extent of canal compromise (mean, 5.5%; P < .001), increased central canal diameter (mean ± SD, 0.71 mm ± 1.3; P < .001), and restoration of vertebral body height, with a mean increase of 5.0 mm (P < .001). However, the implantation did not result in a statistically significant kyphosis reduction (mean, 1.38°; P = .10). All patients except for 1 reported improvement in pain after surgery, with a mean improvement of 1.54 on a 4-point pain scale (P < .001). No clinically significant adverse events were reported. ConclusionsThis study suggests that expandable intravertebral device implantation is a safe and effective treatment for thoracolumbar vertebral burst fractures in patients without fracture-related neurologic deficit. Although implantation did not result in a statistically significant reduction in kyphotic angle, it offered significant improvement in pain, vertebral body height, fracture fragment retropulsion, and central canal diameter compromise.