Mesh Position Research Articles

Meshing Stiffness Calculation of Disposable Harmonic Drive under Full Load

Mechanical equipment in the field of aerospace that is used only once is called disposable machinery. As a piece of typical disposable machinery, disposable harmonic gear exhibit stiffness failure with a large load. This manuscript distinguishes disposable harmonic gear from conventional harmonic gear in terms of the application environment and structure. Then, this paper determines the single-tooth stiffness of the disposable harmonic gear under full load by using the non-uniform beam model and the improved energy method. In addition, the multi-tooth meshing in the disposable harmonic drive is considered, and the improved energy method is modified. Besides, the normal contact force and comprehensive elastic displacement at each meshing position are calculated according to the finite element model. Additionally, curves of the single-tooth stiffness and the comprehensive meshing stiffness are obtained. The theoretical results of the modified analytical method and FEM are compared to verify the correctness of the proposed method in terms of calculating the meshing stiffness of the disposable harmonic drive. Finally, FEM is used to obtain the failure form of the disposable harmonic gear under overload.

Guided bone regeneration using titanium mesh to augment 3-dimensional alveolar defects prior to implant placement. Apilot study.

ObjectivesTo evaluate the outcomes of bone regeneration using a customized titanium mesh scaffold to cover a bone graft for reconstruction of complex defects of the jaws.Materials and Methods19 large defects were digitally reconstructed using CT scans according to the prosthetic requirements. A titanium mesh scaffold was designed to cover the bone (autologous/bovine bone particulate) graft. At least 6 months after surgery, a new cone‐beam CT was taken. The pre‐ and postoperative CT datasets were then converted into three‐dimensional models and digitally aligned. The actual mesh position was compared to the virtual position to assess the reliability of the digital project. The reconstructed bone volumes (RBVs) were calculated according to the planned bone volumes (PBVs), outlining the areas under the mesh. These values were then correlated with the number of exposures, locations of atrophy, and virtually planned bone volume.ResultsThe mean matching value between the planned position of the mesh and the actual one was 82 ± 13.4%. 52.3% (40% early and 60% late) exposures were observed, with 15.8% exhibiting infection. 26.3% resulted as failures. The amount of reconstructed bone volume (RBV) in respect to PBV was 65 ± 40.5%, including failures, and 88.2 ± 8.32% without considering the failures. The results of the exposure event were statistically significant (p = .006) in conditioning the bone volume regenerated.ConclusionsThis study obtained up to 88% of bone regeneration in 74% of the cases. The failures encountered (26%) should underline the operator's expertise relevance in conditioning the final result.

A propensity-score matched analysis of ventral-TAPP vs. laparoscopic IPOM for small and mid-sized ventral hernias. Comparison of perioperative data, surgical outcome and cost-effectiveness

PurposeLaparoscopic techniques have been used and refined in hernia surgery for several years. The aim of this study was to compare an established method such as laparoscopic intra-peritoneal onlay mesh repair (lap. IPOM) with ventral Transabdominal Preperitoneal Patch Plasty (ventral-TAPP) in abdominal wall hernia repair.MethodsPatient-related data of 180 laparoscopic ventral hernia repairs between June 2014 and August 2020 were extracted from our prospectively maintained database. Of these patients, 34 underwent ventral-TAPP and 146 lap. IPOM. After excluding hernias with a defect size > 5 cm and obtaining balanced groups with propensity-score matching, a comparative analysis was performed in terms perioperative data, surgical outcomes and cost-effectiveness.ResultsPropensity-score matching suggested 27 patients in each of the two cohorts. The statistical evaluation showed that intake of opiates was significantly higher in the lap. IPOM group compared to ventral-TAPP patients (p = 0.001). The Visual Analogue Scale (VAS) score after lap. IPOM repair was significantly higher at movement (p = 0.008) and at rest (p = 0.023). Also, maximum subjective pain during hospital stay was significantly higher in the lap. IPOM group compared to ventral-TAPP patients (p = 0.004). No hernia recurrence was detected in either group. The material costs of ventral-TAPP procedure (34.37 ± 0.47 €) were significantly lower than those of the lap. IPOM group (742.57 ± 128.44 € p = 0.001). The mean operation time was 65.19 ± 26.43 min in the lap. IPOM group and 58.65 ± 18.43 min in the ventral-TAPP cohort. Additionally, the length of hospital stay in the lap. IPOM cohort was significantly longer (p = 0.043).ConclusionVentral-TAPP procedures represent an alternative technique to lap. IPOM repair to reduce the risk of complications related to intra-peritoneal position of mesh and fixating devices. In addition, our study showed that postoperative pain level, material costs and hospital stay of the ventral-TAPP cohort are significantly lower compared to lap. IPOM patients.

TEHL analysis of VH-CATT cylindrical gear transmission in elliptical contact considering time-varying parameters

The lubrication characteristics of a cylindrical gear transmission with a variable hyperbolic circular-arc-tooth-trace (VH-CATT) are important theoretical bases for the tribology design of the gear and its fatigue life prediction. Existing lubrication characteristics studies of it are based on simplified linear contact models, which are limited to one specific meshing position only. Therefore, the mathematical models for tooth contact analysis (TCA) and loaded tooth contact analysis (LTCA) are established to calculate most time-varying parameters in a meshing period, such as the kinematic parameters, spatial geometric parameters, and contact parameters, are calculated. Accordingly, a thermo-elastohydrodynamic lubrication (TEHL) model of an elliptical contact of this gear transmission is presented. Using all the proposed mathematical models, the TEHL results with smooth and rough tooth surfaces in a meshing period are analyzed. The obtained results reveal that these models can be used to predict the distribution of the film thickness, pressure, and temperature rise on the smooth and rough tooth surfaces of VH-CATT cylindrical gear transmission in each contact area of a meshing period. And it shows that the time-varying parameters have great influences on lubrication performance. Furthermore, the lubrication mechanism in a meshing period is investigated systematically in VH-CATT cylindrical gear transmission.

Path-related pain after implantation of anterior transvaginal mesh: perspective from anatomical study.

Pelvic organ prolapse (POP) is a common gynecological disease caused by defects in pelvic support tissue that manifests as the descent of the pelvic organs, significantly impacting patient quality of life. Transvaginal mesh (TVM) is an effective treatment (Grade A). However, postoperative pain in the groin and medial thigh is very common. Although the use of mesh for transvaginal POP repair has been prohibited or the indications for such use have been extensively limited in many places, it is still an alternative in some countries. Therefore, the safety of the use of mesh still needs to be discussed. The current research on postoperative pain has mainly focused on management. The pathophysiology is unclear. In this study, anterior TVM surgery was performed on ten frozen cadavers. The obturator area was carefully dissected. We explored the relative position of the polypropylene mesh to the internal segment of the obturator nerve in the obturator canal. Four out of 20 obturator explorations were insufficient to allow conclusions to be drawn. We observed a small branch of the obturator nerve, which is a new anatomical finding that we named the obturator externus muscle branch. This structure terminated in the external obturator muscle in 6 out of the 16 successfully dissected obturator areas. The mean distance between the superficial mesh arm and this nerve branch was 7.5 mm. The mean distance between the deep mesh arm and the closest nerve branch was 5.5 mm. The path of the obturator externus muscle branch of the obturator nerve ran close to the mesh arm. It may provide a clinical anatomical basis explaining the observed postoperative pain.

Influence of meshing stiffness on load distribution between planets of planetary gear drives

Planetary gear sets are suitable for high power density and gear ratio, but this means high torques and stress levels. Though the torque is transmitted between multiple planets, it is not evenly distributed among them due to manufacturing and assembly errors. The torque is greater than the average value in some planets, and smaller in the others, which will have to be considered for strength calculations. In addition, this uneven load distribution among planets can also be affected by the meshing stiffness, if the planets are not at the same relative meshing position at any moment. In this paper, the condition for uneven distribution of the load between planets due to the meshing stiffness is established, and the calculation method of the corresponding influence factor is proposed.

Prophylactic retrorectus mesh versus no mesh in midline emergency laparotomy closure for prevention of incisional hernia (PREEMER): study protocol for a multicentre, double-blinded, randomized controlled trial

BackgroundDespite the fact that emergency midline laparotomy is a risk factor for an incisional hernia, active research on hernia prevention in emergency settings is lacking. Different kinds of meshes and mesh positions have been studied in elective abdominal surgery, but no randomized controlled trials in emergency settings have been published thus far.MethodThe PREEMER trial (registration number NCT04311788) is a multicentre, patient- and assessor-blinded, randomized controlled trial to be conducted in six hospitals in Finland. A total of 244 patients will be randomized at a 1 : 1 ratio to either the retrorectus mesh group, featuring a self-gripping prophylactic mesh, or to the no mesh (control) group, both closed by small-stitch 4 : 1 closure with continuous slowly absorbable monofilament suturing. The primary outcome of the PREEMER trial is the incidence of incisional hernia 2 years after surgery, which will be detected clinically and/or radiologically. Secondary outcomes are the Comprehensive Complication Index score, incidence of surgical-site infections and fascial dehiscence within 30 days of surgery; the incisional hernia repair rate and mesh- or hernia-related reoperations within the 2- and 5-year follow-ups; the incidence of incisional hernia within the 5-year follow-up; and quality of life measured by RAND-36, the Activities Assessment Scale and the PROMIS questionnaire within 30 days and 2 and 5 years from surgery. Additionally, health–economic explorative measures will be explored.ConclusionThe PREEMER trial will provide level 1 evidence on incisional hernia prevention in an emergency setting.Registration numberNCT04311788 (http://www.clinicaltrials.gov). Registered 7 March 2020.

Full-thickness skin grafts to reinforce the abdominal wall: a cross-sectional histological study comparing intra- and extraperitoneal onlay positions in mice.

In the repair of complex abdominal wall hernia, there can be a strong preference to avoid synthetic or biological implants as reinforcement material. Autologous full-thickness skin grafts (FTSG) have shown promising results. However, there are few clinical data on the use of FTSG in an intraperitoneal position and rudimentary knowledge about postoperative histological appearance of tissue remodelling and repair. To investigate the histological appearance of FTSG in the intraperitoneal onlay mesh (IPOM) position. Isogeneic FTSG was positioned in the IPOM (10 mice) and the onlay position (10 mice). After eight weeks, tissues were harvested for histological analysis. Tissue structure, inflammation and cell survival were investigated with histological and immunohistochemical staining. Morphology was similar in both positions. Luciferase staining indicated both onlay and IPOM graft cell survival, with microvascular networks present. In both positions, FTSG showed ongoing tissue remodelling processes and cystic formations containing hair and epidermis. Low-grade acute phase and chronic inflammation were present. Integration was observed in 50% of the mice with similar appearances in IPOM and onlay grafts. FTSG is tolerated, with comparable results either inside or outside the abdominal cavity, and in line with historic histological evaluations. The results suggest further research on FTSG as a potential future reinforcement material in selected cases of complex abdominal wall hernia repair.

When hernia mesh erodes into the bowel

Incisional hernia repair surgery is commonly performed by using a synthetic mesh; due to its low complication rate. This article describes the management of a patient with mesh erosion into the small bowel, a rare complication of mesh-based ventral hernia repair. Fatigue secondary to iron-deficiency anemia and disfigurement from his hernia were his only symptoms. The patient was conservatively managed for several years due to the risks associated with restorative surgery. Eventually, due to deterioration of his health as well as advances in the techniques of abdominal wall reconstruction, the patient underwent surgery. The patient made excellent recovery. The complications associated with the synthetic mesh are likely to be very underreported. This article discusses the factors leading to mesh erosion, including mesh type, fixation methods, mesh migration, and mesh position, and it emphasizes the importance of reporting and following up hernia patients to advance the science behind mesh technology and surgical techniques surrounding ventral hernia repair.

Efficient Algorithm to Calculate a Time-Domain Echo Signal from Moving Targets Based on Physical Optics and the Application to an Autonomous Driving Simulation

An automotive radar simulator is proposed that can consider a dynamic driving scenario. The impulse response is computed based on the distance between the radar and the mesh position and the radar equation. The first-order physical optics technique is used to calculate the backscattering by the meshes, which can efficiently consider the shape of the target; however, because the radar operating frequency is very high, the required amount of mesh for discretization is large. Hence, the calculation of the time-domain echo signal requires considerable computational time. To reduce this numerical complexity, a new scheme is proposed to accurately approximate the time-domain baseband signal generated by the large number of meshes. The radar adopts the frequency modulated continuous waveform. Range-Doppler processing is used to estimate the range and relative velocity of the targets based on which simulation results are numerically verified for a driving scenario.

O12 OPEN PREPERITONEAL INGUINAL HERNIA REPAIR, TREPP VERSUS TIPP IN A RANDOMIZED CLINICAL TRIAL

Abstract Aim The preperitoneal mesh position for inguinal hernia repair showed beneficial results regarding Chronic Postoperative Inguinal Pain (CPIP) with low recurrence rates. Two open preperitoneal techniques, the TransREctus Sheath PrePeritoneal (TREPP) and the TransInguinal PrePeritoneal (TIPP) technique, were compared in a randomized clinical trial with the hypothesis of less patients with CPIP after TREPP due to complete avoidance of nerve contact. Materials and Methods Adult patients with a primary unilateral inguinal hernia were randomized to either TREPP or TIPP in four hospitals. Prior to the trial’s start the study protocol was ethically approved and published. Outcomes included CPIP after 1 year (primary outcome) and recurrence rates, adverse events and Health related Quality of Life (secondary outcomes). Follow-up was performed at 2 weeks, 6 months and 1 year. Results Baseline characteristics were comparable in both groups. Pain was less often present after TREPP at 2 weeks and 6 months, but the CPIP at rest at 1 year was comparable 1.9% after TREPP vs 1.4% after TIPP, p = 0.535). The overall recurrence rate was higher in the TREPP group, 8.9% vs 4.6%, p = 0.022). Corrected for a learning curve for TREPP, no significant difference could be assessed (TREPP 5.7% and TIPP 4.8%, p = 0.591). Conclusions both the TREPP and TIPP technique resulted in a low incidence of CPIP after 1 year follow-up. The TREPP method can be considered a solid method for inguinal hernia repair if expertise is present. The learning curve of the TREPP techniques needs further evaluation.

P083 PARASTOMAL HERNIA REPAIR - EXPERIENCES WITH THE MODIFIED RETROMUSCULAR SUGARBAKER TECHNIQUE

Abstract Aim Parastomal hernias are complex findings with a high recurrence rate. Various methods were described for surgical repair. A new method for the treatment of parastomal hernias with extraperitoneal mesh placement was published in 2016 (Pauli et al.). Recently, open retromuscular repair has been shown to be safe, effective and durable (Beffa et al. 2017). Still, there are concerns regarding mesh related complications (Tastaldi et al. 2017). Material and Methods All patients who underwent an open or laparoscopic modified retromuscular Sugarbaker parastomal hernia repair at our institution were identified. We describe the patient characteristics, operative details, perioperative results and the follow-up. Results Between January 2018 to May 2021 14 patients received surgical repair for parastomal hernia at our institution. Eight of these patients received retromuscular extraperitoneal mesh placement (4 open, 4 laparoscopic) in the aforementioned technique. The median age was 72 years (65 – 85) and the median BMI was 31 kg/m² (26 – 34). Six patients had a urostomy and two had a colostomy. One patient had a recurrent parastomal hernia after previous intraabdominal mesh repair. The median operating time was 223 minutes (144 – 425). Median Mesh size was 300 cm² (225 – 750). Two minor complications (Clavien-Dindo Classification Grade II) demanding pharmacological treatment. The median hospital stay was 8 days (4 – 17). Median follow up was 17 month (range 1 – 26). Recurrence rate was 25 %. Conclusions The modified retromuscular sugerbaker technique seems to be safe and feasible as shown by our data. Due to the extraperitoneal mesh position, we see fundamental methodological advantages. Further studies are necessary for long-term results.

VP028 TAPP REPAIR FOR INCISIONAL LUMBAR HERNIA

Abstract Aim “Incisional hernias are very common and can present even after minimally invasive surgery for other pathologies. Laparoscopic ventral hernia repair first described by LeBlanc in 1992, gained great popularity, because of its known advantages over the open techniques. In the last decade because of increasing concerns about the future risks of using an intra-peritoneal mesh, several minimally invasive techniques using a mesh outside abdominal cavity have been described. We report the use of a TAPP technique.” Material and Methods “48 yo female patient, that underwent a laparoscopic right adrenalectomy, for myelolipoma, in 2015, with subsequent incisional lumbar hernia (L4W1) in the extraction incision.” Results “The patient was submitted to a laparoscopic TAPP repair in ambulatory surgery with extended recovery. The hernia defect was closed with a barbed suture and it was used a 15x15cm medium weight polypropylene mesh without traumatic fixation. For pain control it was done a TAP block guided by laparoscopy. The duration of surgery was 90 minutes. The patient had no complications. No recurrence on follow-up (4 months).” Conclusions “New minimally invasive procedures for the repair of incisional hernias avoid the intraperitoneal mesh position and maintain all the advantages of the minimally invasive approach. Some of these techniques may be complex and have a long learning curve. TAPP seems reproducible and a good option if a good extra-peritoneal dissection is possible. Larger series are needed, to accurately compare these new techniques with IPOM, open sublay and to select the best technique for each patient.”

Management of lateral abdominal wall hernias

Lateral abdominal wall hernias are rare and inconsistently defined, which is why the use of the European Hernia Society classification makes sense, not least for the purpose of comparing the quality of surgical results. Adistinction must be made between true fascial defects and denervation atrophy. Based on the available literature, there is generally alow level of evidence with no consensus on the best operative strategy. The proximity to bony structures and the complex anatomy of the three-layer abdominal wall make the technical treatment of lateral hernias difficult. The surgical variations include laparoendoscopic, robotic, minimally invasive, open or hybrid approaches with different mesh positions in relation to the layers of the abdominal wall. The extensive preperitoneal mesh reinforcement open, transabdominal peritoneal (TAPP) laparoscopic repair or total extraperitoneal (TEP) endoscopic repair has met with the greatest approval. The extent of the required medial mesh overlap is determined by the distance between the medial defect boundary and the lateral edge of the straight rectus abdominus muscles. The medially directed preperitoneal and retroperitoneal dissection can be extended into the homolateral retrorectus compartment by laterally incising the posterior rectus sheath or by crossing the midline behind the intact linea alba into the contralateral retrorectus compartment. The intraperitoneal onlay mesh (IPOM) technique is asuitable procedure only for smaller defects with possible defect closure but it is also important as an exit strategy in the case of adefective peritoneum. Individualized prehabilitative and preconditioning measures are just as important as the assessment of preoperative anamnestic and clinical findings and risks with radiographic cross-sectional imaging diagnostics.

The Plane of Mesh Placement Does Not Impact Abdominal Donor Site Complications in Microsurgical Breast Reconstruction.

Reinforcement of the abdominal wall with synthetic mesh in autologous breast reconstruction using abdominal free tissue transfer decreases the risk of bulging and herniation. However, the impact of the plane of mesh placement on donor site complications has not yet been investigated. We performed a retrospective analysis of 312 patients who had undergone autologous breast reconstruction with muscle-sparing transverse rectus abdominis myocutaneous (MS-TRAM) flaps or deep inferior epigastric perforator (DIEP) flaps as well as polypropylene mesh implantation at the donor site. Donor site complications were compared among patients with different flap types and different mesh positions including overlay (n = 90), inlay and overlay (I-O; n = 134), and sublay (n = 88). Abdominal hernias occurred in 2.86% of patients who had undergone MS-TRAM reconstructions and in 2.63% of patients who had undergone DIEP reconstructions. When comparing patients with different mesh positions, donor site complications occurred in 14.4% of patients with overlay mesh, 13.4% of patients with I-O mesh, and 10.2% of patients with sublay mesh (P = 0.68). Abdominal hernias occurred in 4.44% of patients with overlay mesh, 2.24% of patients with I-O mesh, and 2.27% of patients with sublay mesh (P = 0.69). Multivariable logistic regression analysis did not identify a significant association between mesh position and hernia rates as well as wound complications. Our data indicate that the plane of synthetic mesh placement in relation to the rectus abdominis muscle does not impact the rate of postoperative donor site complications in patients undergoing breast reconstruction with MS-TRAM or DIEP flaps.

ROBotic Utility for Surgical Treatment of hernias (ROBUST hernia project)

We describe the evolution in hernia repair approaches in our practice during the first 3 years of adopting robotic assisted laparoscopic surgery. For inguinal hernia repair, we began using the robotic platform for complex hernias, and the use of open repair decreased from 17% to 6%. For primary ventral hernias, open procedures decreased from 59% to 10% and for incisional ventral hernias, from 48% to 11%. Moreover, a large shift in mesh position for ventral hernias was seen, with an increase of the retromuscular position from 20% to 82% and a decrease of intraperitoneal mesh position from 48% to 10%.The robotic platform seems to hold a significant potential for complex inguinal hernias, in addition to ventral and incisional hernias which require component separation. A shorter hospital stay and less postoperative complications might make the adoption of the robotic platform for abdominal wall surgery a valuable proposition.

Effect of through-the-thickness position of aluminum wire mesh on the mechanical properties of GFRP/Al hybrid composites

Glass laminate aluminum reinforced epoxy (GLARE) mixes an extremely thin ply of aluminum wire mesh layers with epoxy strengthened with fibers to create a hybrid composite laminates. During this investigation, plain E-glass fiber/epoxy specimens in addition to specimens with epoxy laminates reinforced with both E-glass/fiber, and wire meshes of aluminum were created. Meshes made of aluminum wire were used to increase the toughness of the E-glass fiber/epoxy combination. Tensile, bending, and hardness tests were performed to see how inserting Al wire meshes through thickness of the specimen in place of glass fiber layers affected the material mechanical characteristics. According to the outcomes from results, an influence on strength, toughness, and ductility of laminates due to using Al wire mesh instead of glass fiber. The characteristics of the generated hybrid laminates were greatly influenced by the varying position and the orienting direction of the aluminum wire mesh ply. Inclusion of Al wire mesh in the outer layers significantly made deterioration in material tensile strength and bending strength. The tensile strain also bending strain, on the other hand, were improved by 16.95 percent and 117 percent, respectively.

Ventral Hernia Repair in Endoscopically Total Extrapertoneal Technique (eTEP) - Evaluation of Postoperative Outcome and One Year Follow-up

Several recent meta-analyses have identified the retromuscular plane as the preferred mesh position in ventral hernia repair. Open surgery used to be the standard technique for these procedures. However, new minimally invasive techniques with totally extraperitoneal access and mesh positioning in the retromuscular plane have evolved. Between September 2018 and March 2019, 18 consecutive patients with ventral hernia were treated endoscopically in the totally extraperitoneal technique. Depending on the localisation and size of the hernia, the appropriate access was chosen and an uncoated mesh was placed in the retromuscular space in all patients. Data of patients' characteristics as well as peri- and postoperative parameters were collected. One year after surgery, patients were asked about recurrence, pain and complications, using the questionnaire of the herniamed data base. No intraoperative complications were noted. Postoperatively, there was one retromuscular seroma that did not need treatment, one temporary paralysis of the radial nerve and one pulmonary embolism. None of these complications led to persistent problems. 17 of 18 patients were available for follow-up. One year follow-up showed no hernia recurrence. One patient had pain at rest requiring treatment. Totally extraperitoneal endoscopic hernia surgery is a safe and promising new technique that is also feasible in complex hernias and with satisfactory 1 year results. This technique can combine the advantages of minimally invasive surgery with those of extraperitoneal mesh placement.

MRI Surveillance of Plastic Material Surgical Meshes: Experimental Model - Interim Results

The number of surgical procedures for abdominal wall defects is increasing, often requiring the insertion of plastic material meshes. Surveillance of patients with inserted plastic meshes requires an accurate determination of the position of the mesh. However, this is a difficult task, depending on the kind of mesh, magnetic resonance imaging (MRI) protocol or consistence of the surrounding tissue (fat, muscle, aponeurosis). The aim of our research was to develop an experimental model to test the ability of MRI to identify the exact position of surgical plastic meshes: polypropylene or polyester. To simulate the placement of a mesh in human body we developed a model built up from two pieces of tissue with dimensions of 40 cm x 20 cm, harvested from a pig with a weight of 120 kg. The meshes were situated for MRI evaluation between the two pieces: abdominal pig muscle respectively suprajacent abdominal pig wall subcutaneous fat, approximately 2 cm high. Five surgical meshes were scanned through six MRI sequences, in view of establishing an optimal MRI scanning protocol and best visible meshes. The MRI scans were evaluated by 5 radiologists with different degrees of training. Our results showed that the experimental model developed by us can be successfully used to test the ability of MRI to visualize different kind of plastic meshes. Also, our experiment has revealed that T1fl2D sequence is the best in highlighting meshes from surrounding tissue, and the best visualized Mesh was number 4, made of polyester. In conclusion, based on our experimental model, we should select a plastic mesh or MRI protocol which will allow an optimal post implantation monitoring. Modern technology of material�s fabrication can help to better identify the mesh itself using MRI scanning.

Time-varying mesh stiffness calculation for gear pairs with misalignment errors in multiple degrees of freedom based on an analytical method

Misalignment errors (MEs) in multiple degrees of freedom (multi-DOFs) at the mesh position will lead to a change in the time-varying mesh stiffness (TVMS) and then affect the dynamic behaviour of gear pairs. Therefore, a new, more rapid, three-dimensional analytical model for TVMS calculation for gear pairs with three rotational and three translational MEs is established in this paper, and a new solution method based on potential energy theory is presented. In addition, the correctness of the new model is verified by the finite element method (FEM). Moreover, the effective contact line, uneven distribution of mesh force on the contact line, and mesh position change are taken into account. Finally, the TVMS under different ME conditions is calculated with the new analytical model. The results showed that the different MEs have dissimilar effects on the TVMS, and the relationship between the ME and TVMS is nonlinear. In addition, the region of single-pair and double-pair teeth in contact would also change with ME.