Prospective multicentre study on barbed reposition pharyngoplasty standing alone or as a part of multilevel surgery for sleep apnoea.

OBJECTIVES: The aim of this study was to demonstrate in a prospective multicentre study that Barbed Reposition Pharyngoplasty (BRP) procedure is safe and effective in management of obstructive sleep apnoea/hypopnea syndrome (OSAHS) patients. DESIGN: Prospective study. SETTING: Multicentre study. PARTICIPANTS: Patients suffering from obstructive sleep apnoea. MAIN OUTCOMES MEASURES: Values of postoperative apnoea-hypopnea index (AHI), oxygen desaturation index (ODI), epworth sleepiness scale (ESS). RESULTS: 111 Barbed Reposition Pharyngoplasty procedures standing alone or as a part of multilevel surgery for OSAHS, performed between January and September 2016, were analysed in 15 different centres. The average hospitalisation period was 2.5 ± 0.5 days. The mean patient age was 46.3 ± 10.5 years. The average body mass index at the time of the procedure was 27.9 ± 3.2, and the majority of the patients were men (83%). The mean preoperative and postoperative apnoea/hypopnea index was 33.4 ± 19.5 and 13.5 ± 10.3, respectively (P < .001). The mean preoperative and postoperative ESS score was 10.2 ± 4.5 and 6.1 ± 3.6, respectively (P < .001). The mean preoperative and postoperative ODI were 29.6 ± 20.7 and 12.7 ± 10.8, respectively (P < .001). CONCLUSIONS: Patients undergoing BRP standing alone or as part of a multilevel approach for the treatment of OSAHS have a reasonable expectation for success with minimal morbidity.

Combined transnasal transcervical robotic dissection of posterior skull base: feasibility in a cadaveric model.

The current surgical trend is to expand the variety of minimally invasive approaches and, in particular, the possible application of robotic surgery in head and neck surgery. For this purpose, we explored the feasibility of a combined transcervical-transnasal approach to the posterior skull base, using the da Vinci Surgical System in 3 cadaver heads. Superb visualization of the sellar, suprasellar and clival regions was possible in all three specimens. The trocars` placement through a transcervical port made a more cephalad visualization possible, eliminating the need to split the palate. The advantages of robotic surgery applied to the posterior cranial fossa are similar to the ones already clinically experienced in other districts (oropharynx, tongue base), in terms of tremor-free, bimanual, precise dissection. The implementation of instruments for bony work will definitely increase the applicability of such a system in the forthcoming years.

Transoral robotic surgery for hilo-parenchymal submandibular stones: step-by-step description and reasoned approach.

The conservative transoral approach to hilo-parenchymal submandibular stones has been proposed as an alternative to traditional sialadenectomy. The main purpose is to preserve the gland and eliminate the risk of a cervical scar and damage to the marginal mandibular branch of the facial nerve. The spread of transoral robotic surgery has favoured its application not only in the oropharynx, but also in the anterior oral cavity. This article describes a transoral robotic approach for hilo-parenchymal submandibular stones. In January 2019, two patients with a right and a left hilo-parenchymal submandibular stone of 15mm and 8mm, respectively, underwent removal of the stone with transoral robotic surgery using the Si Da Vinci surgical robot. The procedure was performed successfully and tolerated well, with a one-night hospitalization. There were no complications such as lingual nerve damage, painful gland swelling, infection, or ranula. The patients were followed up clinically and ultrasonographically for the first 3 months to verify symptom relief and persistence of stones; no symptoms or stones were found. The transoral robotic surgical approach seems to be safe and adequate for the conservative management of large hilo-parenchymal submandibular stones. An adequate diagnosis together with proper docking and an appropriate approach to the oral floor is mandatory.

Defect-oriented reconstruction after transoral robotic surgery for oropharyngeal cancer: a case series and review of the literature.

Transoral robotic surgery (TORS) is a fascinating new technique that has been shown to be a safe and feasible treatment for selected oropharyngeal cancers. Furthermore, TORS might offer some advantages in selected locoregionally advanced cancers. Thus, the patient selection is the keypoint for the useful application of TORS. However, the reconstruction of large oropharyngeal defects is challenging due to the restoration of velopharyngeal competency and swallowing. Moreover, the absence of mandibular splitting increases the difficulties faced by reconstructive surgeons. The paradigm for oropharyngeal reconstruction has undergone changes paralleling reflecting the overall change in the trend of the treatment alternatives over the last few decades. Flap choice and harvesting should be tailored to obtain significant advantages both in functional terms and for easy insetting. In this review, we analyse the strengths and weaknesses of the various flaps used in TORS framework with particular regards on our preliminary experience.

Does the Ventrica magnetic vascular positioner (MVP) for coronary artery bypass grafting significantly alter local fluid dynamics? A numeric study.

OBJECTIVE: Automatic devices have been recently introduced to make the anastomosis procedure quick and efficient when creating a coronary bypass on the beating heart. However, the implantation of these devices could modify the graft configuration, consistently affecting the hemodynamics usually found in the traditional anastomosis. As local fluid dynamics could play a significant role in the onset of vessel wall pathologies, in this article a computational approach was designed to investigate flow patterns in the presence of the Ventrica magnetic vascular positioner (Ventrica MVP) device. METHODS: A model of standard hand-sewn anastomosis and of automated magnetic anastomosis were constructed, and the finite volume method was used to simulate in silico realistic graft hemodynamics. Synthetic analytical descriptors -- i.e., time-averaged wall shear stress (TAWSS), oscillating shear index (OSI) and helical flow index (HFI) -- were calculated and compared for quantitative assessment of the anastomosis geometry hemodynamic performance. RESULTS: In this case study, the same most critical region was identified for the 2 models as the one with the lowest TAWSS and the highest OSI (TAWSS=0.229, OSI=0.255 for the hand-sewn anastomosis; TAWSS=0.297, OSI=0.171 for the Ventrica MVP(R)). However, the shape of the Ventrica MVP does not induce more critical wall shear stresses, oscillating flow and damped helicity in the graft fluid dynamics, as compared with conventional anastomosis. CONCLUSIONS: We found that the use of the Ventrica MVP for the case study under investigation was not associated with more critical fluid dynamics than with conventional hand-sewn anastomosis. Thereby, the device could facilitate beating heart and minimally invasive coronary artery bypass grafting without increasing local hemodynamic-related risks of failure.

A new electro-mechanical bioreactor for soft tissue engineering.

By enabling the maintenance of controlled chemical and physical environmental conditions, bioreactors proved that electro-mechanical stimulation improves tissue development in vitro, especially in the case of tissues which are subjected to stimuli during embryogenesis and growth (i.e. skeletal and cardiac muscle tissue). However, most of the bioreactors developed in the last 20 yrs, designed to suit specific applications, lack versatility. With the aim to provide researchers with a yielding, versatile tool, we designed and realized in this study an electro-mechanical stimulator capable of dynamically culturing four biological constructs, delivering assignable stretching and electrical stimulation patterns. The device has been conceived to be easy to handle and customizable for different applications, while ensuring sterility along with stimuli delivery. The gripping equipment, modular and adaptable to scaffolds of different consistencies, is provided with dedicated tools for supporting sample insertion into the culture chamber performed under a laminar flow hood. As to performance, a wide range of electro-mechanical stimulation patterns and their relative occurrence can be accomplished, permitting the adjustment of the dynamic culture parameters both to the specific cell species and to the developmental phase of the cultured cells.

Barbed reposition pharyngoplasty in multilevel robotic surgery for obstructive sleep apnoea.

The surgical treatment of obstructive sleep apnoea in patients who are non-compliant with continuous positive airway pressure therapy still represents a valid alternative. In recent years, the multilevel approach is becoming more diffuse in routine surgical practice, especially since the introduction of transoral robotic surgery. Barbed reposition pharyngoplasty in multilevel robotic surgery for OSA may represent a valid option to surgically approach the soft palate. Herein, we describe the technique and preliminary results of our experience.

Palatal surgery in a transoral robotic setting (TORS): preliminary results of a retrospective comparison between uvulopalatopharyngoplasty (UPPP), expansion sphincter pharyngoplasty (ESP) and barbed repositioning pharyngoplasty (BRP).

It has become increasingly clear in the past decade that surgical management of obstructive sleep apnoea hypopnoea syndrome (OSAHS) is most successfully managed with multilevel surgery. We evaluated the outcomes of multilevel interventions comparing three different palatal techniques added to TORS: uvulopalatopharyngoplasty (UPPP), a modified expansion sphincter pharyngoplasty (ESP), inspired by the Pang expansion sphincter pharyngoplasty technique and the latest barbed repositioning pharyngoplasty (BRP). Thirty patients were retrospectively evaluated. Ten patients underwent UPPP by Fairbanks, 10 BRP and 10 a modified ESP already described. All patients underwent TORS, tonsillectomy and septo-turbinoplasty. For all cases, the following data were retrieved and revaluated: preoperative and postoperative apnoea-hypopnoea index (AHI), preoperative and postoperative Epworth Sleepiness Scale (ESS), pain visual analogue scale (VAS; 0-10) for the first 5 days postoperatively, palatal operative time for each surgical technique, discharge date and complication types and rate. Both BRP and ESP resulted in better postoperative AHI values and higher surgical success rates in comparison with UPPP. On the other hand, BRP was not more effective than ESP. ESP surgery time was significantly higher than UPPP, while BRP was the quickest procedure. In summary, ESP and BRP seem to be more effective than UPPP in a multilevel surgical robotic setting. However, being quicker, easy to learn and with a low rate of complications, BRP is a safe, effective and promising option for treatment of OSAHS patients.

Transoral robotic surgery (TORS): a new tool for high risk tracheostomy decannulation.

Tracheostomy decannulation has always been considered a procedure with an attendant risk, especially in patients with a reduced upper airway diameter as is commonly observed in the obstructive sleep apnoea (OSA) population. We report on 4 cases where transoral robotic surgery (TORS) helped in the management of long-term cannulated patients. The aims of our paper are: 1. To demonstrate how the otolaryngology team can help identify patients at high risk for decannulation failure; and 2. To demonstrate how TORS may aid in the decannulation process of patients at high risk for failure due to severe tongue base hypertrophy. From our experience, TORS appears to offer an effective option to aid in the decannulation of patients with a severe hypertrophy of the base of tongue and floppy epiglottis.

Endothelial cell adhesion force estimation at the nanoscale.

Endothelial cell adhesion to a synthetic surface includes a definite set of molecular interactions. Cell adhesion is managed by fibronectin and vitronectin in extracellular matrix (ECM) that binds the receptor site of the trans-membrane protein dimers, the integrins. These proteins contain one of the binding sites (I-like domain receptor) for the Arg-Gly-Asp (RGD) peptides that are the established adhesion receptor sites in the ECM. A molecular approach can quantify the adhesion strength by ligand-receptor force computation. The molecular interaction energy between a polyethylene (PE) surface covalently grafted with the adhesion sites (RGD-containing) and trans-membrane integrin receptor (I-domain) was evaluated through a molecular model of a single ligand-receptor complex. The aims of this work were: (i) the generation of the receptor molecular model: the I-like domain; (ii) the evaluation of the greatest binding chemical affinity between the I-like domain and three RGD-containing peptides; (iii) the development of the molecular model of crystalline lamellae of PE; and (iv) the evaluation of the interac-tion energies and the interaction force between the I-like domain and the grafted biomaterial. The calculation of the interaction energies can provide an estimation of the adhesion force of the ligand-receptor complex and, finally, of the endothelial cell adhesion force. The calculated cell adhesion force is in agreement with experimental data.(Journal of Applied Biomaterials and Biomechanics 2005; 3: 42-9).

A novel approach emphasising intra-operative superficial margin enhancement of head-neck tumours with narrow-band imaging in transoral robotic surgery.

The primary goal of surgical oncology is to obtain a tumour resection with disease-free margins. Transoral robotic surgery (TORS) for surgical treatment of head-neck cancer is commensurate with standard treatments. However, the likelihood of positive margins after TORS is up to 20.2% in a recent US survey. The aim of this study is to evaluate the efficacy and the feasibility of narrow-band imaging (NBI) during TORS in order to improve the ability to achieve disease-free margins during tumour excision. The present study was conducted at the ENT, Head- Neck Surgery and Oral Surgery Unit, Department of Special Surgery, Morgagni Pierantoni Hospital, Azienda USL Romagna. From March 2008 to January 2015, 333 TORS were carried out for malignant and benign diseases. For the present study, we retrospectively evaluated 58 biopsy-proven squamous cell carcinoma patients who underwent TORS procedures. Patients were divided into 2 groups: (1) 32 who underwent TORS and intra-operative NBI evaluation (NBI-TORS); (2) 21 who underwent TORS with standard intra-operative white-light imaging (WLITORS). Frozen section analysis of margins on surgical specimens showed a higher rate of negative superficial lateral margins in the NBI-TORS group compared with the WLI-TORS group (87.9% vs. 57.9%, respectively, p = 0.02). The sensitivity and specificity of intra-operative use of NBI, respectively, were 72.5% and 66.7% with a negative predictive value of 87.9%. Tumour margin enhancement provided by NBI associated with magnification and 3-dimensional view of the surgical field might increase the capability to achieve an oncologically-safe resection in challenging anatomical areas where minimal curative resection is strongly recommended for function preservation.

Flow dynamics of the St Jude Medical Symmetry aortic connector vein graft anastomosis do not contribute to the risk of acute thrombosis.

BACKGROUND: The efficacy of the St Jude Medical Symmetry aortic connector (St Jude Medical, Inc, St Paul, Minn) for coronary artery bypass is currently debated. Potential drawbacks are the biocompatibility of the endoluminal device, the need for graft manipulation during the procedure, and the 90 degrees offset of the vein graft from the ascending aorta, which may induce graft kinking and abnormal fluid dynamics. In this article, a computational approach was designed to investigate the fluid dynamics pattern at the proximal graft. METHODS: Four models of hand-sewn anastomoses and two models of automated anastomoses were constructed; a finite volume technique was used to simulate realistic graft fluid dynamics, including aortic compliance and proper aortic and graft flow rates. The anastomosis geometry performance was analyzed by calculating time-averaged wall shear stress and the oscillating shear index at the toe and heel regions of the proximal graft. RESULTS: Time-averaged wall shear stress was significantly lower in the hand-sewn anastomosis models than in the two models that simulated the use of the aortic connector (0.38 +/- 0.07 Pa vs 1.32 +/- 0.4 Pa). Higher oscillating shear index values were calculated in the hand-sewn anastomosis models (0.15 +/- 0.02 Pa vs 0.06 +/- 0.02 Pa). CONCLUSIONS: Automated anastomosis geometry is associated with less critical fluid dynamics than with conventional hand-sewn anastomosis: the shape of the proximal graft induces more physiological wall shear stresses and less oscillating flow, suggesting a lower risk of atherosclerotic plaque and intimal hyperplasia as compared with conventional anastomosis geometry. Therefore, the reported early thrombosis and late failure of the St Jude Medical aortic connector anastomoses are not related to unfavorable fluid dynamics.

Ventricular motion during the ejection phase: a computational analysis.

In the present paper, the study of the ventricular motion during systole was addressed by means of a computational model of ventricular ejection. In particular, the implications of ventricular motion on blood acceleration and velocity measurements at the valvular plane (VP) were evaluated. An algorithm was developed to assess the force exchange between the ventricle and the surrounding tissue, i.e., the inflow and outflow vessels of the heart. The algorithm, based on the momentum equation for a transitory flowing system, was used in a fluid-structure model of the ventricle that includes the contractile behavior of the fibers and the viscous and inertial forces of the intraventricular fluid. The model calculates the ventricular center of mass motion, the VP motion, and intraventricular pressure gradients. Results indicate that the motion of the ventricle affects the noninvasive estimation of the transvalvular pressure gradient using Doppler ultrasound. The VP motion can lead to an underestimation equal to 12.4 +/- 6.6%.

A model of multicomponent cardiac fibre.

In order to simulate the contraction of a cardiac myofibre, a multicomponent fibre model has been developed. This model is composed of a series of segments which are activated in succession. Each segment is represented by the Hill's three component model of the sarcomere. The contractile element behaviour is described by the Huxley's theory and the time dependence agrees with the activation factor proposed by Julian for skeletal muscle, and modified by Wong for cardiac muscle. The two elastic elements have non-linear exponential characteristics. The isometric contraction of the multicomponent fibre has been simulated by means of a computer program. The results show the tension generated by the fibre, the propagation of the contraction along the fibre and the different contribution of each segment depending on its position inside the fibre.

Myosin head mechanical performance under different conformational change mechanisms.

The present paper puts forward a mathematical approach to model the conformational changes of the myosin head due to ATP hydrolysis, which determine the head swinging and consequent sliding of the actin filament. Our aim is to provide a simple but effective model simulating myosin head performance to be integrated into the overall model of sarcomere mechanics under development at our Laboratory (J. Biomech. 34 (2001) 1607). We began by exploring myosin head mechanics in recent findings about myosin ultrastructure, morphology and energetics in order to calculate the working stroke distance (WS) and the force transmitted to the actin filament during muscle contraction. Two different working stroke mechanisms were investigated, assuming that the swinging of the myosin head occurs either as a consequence of purely conformational changes (Science 261 (1993a) 58) or by thermally driven motion (ratchet mechanism) followed by conformational changes (Cell 99 (1999) 421). Our results show that force and WS values vary markedly between the two models. The maximum force generated is about 10 pN for the first model and 31 pN for the second model, and the WSs are about 13 and 4 nm, respectively. These results are then discussed and compared with published data. The experimental data used for comparison are scarce and non-homogeneous; hence, the final remarks do not lead to definite conclusions. In any event, relatively speaking, the first model is more coherent with experimental findings.

Myosin cross-bridge mechanics: geometrical determinants for continuous sliding.

Advances in experimental techniques have provided new details on the molecular mechanisms governing the cross-bridge kinetics. Nevertheless, the issue of micromechanics of sliding is still debated. In particular, uncertainty exists regarding the myosin filament arrangement and structure and the mechanics of the myosin head with respect to the working stroke distance (WS) and the duty ratio (r), i.e. the fraction of the ATPase cycle time the myosin head is attached to the actin filament. The object of the present work is to provide a theoretical framework to correlate different features of cross-bridge mechanics; the main hypothesis is that the attachment between the actin filament and the surrounding myosin filaments has to be continuous through the sliding (continuous sliding hypothesis) in order to maximise the effect of the myosin head performance. A 3-D model of the sliding mechanism based on a geometrical approach is presented, which is able to identify the architectures that accomplish the continuous sliding under unloaded conditions. About 200 different configurations have been simulated by changing the myosin head binding range, i.e. its ability to reach an actin binding site from its rest position, WS, the myosin head orientation and the actin filament orientation. Only few configurations were consistent with the continuous sliding hypothesis. Depending on the parameter set adopted, the percentage of attached heads (%AH) calculated ranges between 4% and 28%, r between 0.08 and 0.02s(-1), and the sliding velocity between 0.7 and 10.6 microm/s. In all the cases, results were not affected by the WS value.

Poroelastic finite element analysis of a bone specimen under cyclic loading.

It had been suggested that the fluid embodied in bone lacunar-canalicular porosity may play an important role in bone remodelling [Weinbaum et al., 1994. Journal of Biomechanics 27, 339-360]. In this paper a finite element model of a poroelastic prismatic solid of rectangular cross-section is considered to simulate bone behaviour, precisely as in the previous work by Zhang and Cowin [Zhang and Cowin, 1994. Journal of Mechanical Physics of Solids 42, 1575-1599]. This solid is subject to combined cyclic axial and bending loads at its end. The objectives of the study are: (1) to verify the accuracy of the simplifying hypotheses underlying the analytical solutions established by the above authors; (2) to provide further insight into the behaviour of that solid; (3) to test the advantages in generality and versatility and the computing costs of general-purpose finite element codes in poroelastic analysis. The study is parametric with respect to the fluid leakage coefficient, to the ratio of the bending moment and axial load, and to the ratio of the characteristic relaxation time of the pore pressure over the excitation period. Results show that, for all the cases considered, the pore pressure distribution along the section height of the poroelastic beam exhibits a very good matching with previous analytical results. Stresses transversal with respect to the beam axis (assumed as constant or zero in previous analytical solutions) are evaluated. The analysis pointed out that: (1) the effects due to end-loads with zero resultants practically extinguish within a distance from the beam end almost equal to a typical length of the cross-section; (2) cross-sections remain plane above that distance; (3) the transversal total stresses are three orders of magnitude lower than axial stress.

Possible role of decorin glycosaminoglycans in fibril to fibril force transfer in relative mature tendons--a computational study from molecular to microstructural level.

Experimental studies on immature tendons have shown that the collagen fibril net is discontinuous. Manifold evidences, despite not being conclusive, indicate that mature tissue is discontinuous as well. According to composite theory, there is no requirement that the fibrils should extend from one end of the tissue to the other; indeed, an interfibrillar matrix with a low elastic modulus would be sufficient to guarantee the mechanical properties of the tendon. Possible mechanisms for the stress-transfer involve the interfibrillar proteoglycans and can be related to the matrix shear stress and to electrostatic non-covalent forces. Recent studies have shown that the glycosaminoglycans (GAGs) bound to decorin act like bridges between contiguous fibrils connecting adjacent fibril every 64-68 nm; this architecture would suggest their possible role in providing the mechanical integrity of the tendon structure. The present paper investigates the ability of decorin GAGs to transfer forces between adjacent fibrils. In order to test this hypothesis the stiffness of chondroitin-6-sulphate, a typical GAG associated to decorin, has been evaluated through the molecular mechanics approach. The obtained GAG stiffness is piecewise linear with an initial plateau at low strains (<800%) and a high stiffness region (3.1 x 10(-11)N/nm) afterwards. By introducing the calculated GAG stiffness in a multi-fibril model, miming the relative mature tendon architecture, the stress-strain behaviour of the collagen fibre was determined. The fibre incremental elastic modulus obtained ranges between 100 and 475 MPa for strains between 2% and 6%. The elastic modulus value depends directly on the fibril length, diameter and inversely on the interfibrillar distance. In particular, according to the obtained results, the length of the fibril is likely to play the major role in determining stiffness in mature tendons.

A numerical fluid mechanical study of repaired congenital heart defects. Application to the total cavopulmonary connection.

A computational fluid dynamics study based on the application of the finite element method has been performed to investigate the local hemodynamics of the total cavopulmonary connection. This operation is used to treat congenital malformations of the right heart and consists of a by-pass of the right ventricle. In this paper the adopted methodology is presented, together with some of the preliminary results. A three-dimensional parametric model of the connection and a lumped-parameter mechanical model of the pulmonary circulation have been developed. The three-dimensional model has been used to simulate the local fluid dynamics for different designs of the connection, allowing a quantitative evaluation of the dissipated energy in each of the examined configurations. The pulmonary afterload of the three-dimensional model has been reproduced by coupling it with the pulmonary mechanical model. The results show that, from a comparative point of view, the energetic losses can be greatly reduced if a proper hydraulic design of the connection is adopted, which also allows control of the blood flow distribution into the lungs.