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1.
J Minim Invasive Gynecol ; 31(5): 445-452, 2024 May.
Article in English | MEDLINE | ID: mdl-38417674

ABSTRACT

STUDY OBJECTIVE: To assess the impact visceral adipose tissue percentage (VAT%) on surgical outcomes during minimally invasive surgery in obese women with endometrial cancer. DESIGN: Retrospective observational cohort study. SETTING: Mie University Hospital, Japan. PATIENTS: Of the 73 women (body mass index [BMI] >30 kg/m2) with obesity and primary endometrial cancer, 52 underwent robotic surgery, while 21 underwent laparoscopic surgery between April 2014 and December 2022. INTERVENTIONS: We investigated the correlation between surgical outcomes (operative time and blood loss) and obesity (BMI and visceral adipose tissue percentage [VAT%]). MEASUREMENTS AND MAIN RESULTS: Abdominal fat-related parameters were measured at the level of the umbilicus using preoperative computed tomography. A weak negative correlation was found between BMI and VAT% (CC = -0.313, p = .001). Multivariate analysis showed that VAT% had a stronger correlation to total and practical operative time than BMI (ß = 0.338 vs 0.267, ß = 0.311 vs 0.209, respectively) and was an independent predictor of blood loss. VAT% was an independent predictive marker prolonged for operative time and increased blood loss during lymphadenectomy. CONCLUSION: VAT% could be an indicator of surgical outcomes for patients with obesity and endometrial cancer.


Subject(s)
Body Mass Index , Endometrial Neoplasms , Intra-Abdominal Fat , Laparoscopy , Obesity , Operative Time , Humans , Female , Endometrial Neoplasms/surgery , Endometrial Neoplasms/pathology , Endometrial Neoplasms/complications , Intra-Abdominal Fat/diagnostic imaging , Retrospective Studies , Middle Aged , Obesity/complications , Aged , Laparoscopy/methods , Robotic Surgical Procedures/methods , Blood Loss, Surgical , Treatment Outcome , Japan/epidemiology , Lymph Node Excision/methods
2.
Intern Med ; 2023 Nov 06.
Article in English | MEDLINE | ID: mdl-37926536

ABSTRACT

A 34-year-old Japanese man presented with blurred vision, headache, nausea, anemia, thrombocytopenia, and severe renal dysfunction. Thrombotic microangiopathy was initially suspected to have been caused by malignant hypertension. Antihypertensive medications did not improve his thrombocytopenia or renal dysfunction, and other diseases causing thrombotic microangiopathy were ruled out. Therefore, the patient was diagnosed with atypical hemolytic uremic syndrome. A renal biopsy revealed an overlap of thrombotic microangiopathy and C3 glomerulopathy. Genetic testing revealed c.848A>G (p.Asp283Gly), a missense heterozygous variant in the gene encoding complement factor I. Overlapping atypical hemolytic uremic syndrome and C3 glomerulopathy with complement factor I mutation is very rare, especially in Japan.

3.
Curr Oncol ; 30(10): 9327-9334, 2023 10 20.
Article in English | MEDLINE | ID: mdl-37887574

ABSTRACT

The prognosis for cancer of unknown primary site (CUP) is poor, and squamous cell carcinoma of the unknown primary site (SCCUP) is a rare histological type. CUP is often treated with aggressive multimodal treatments, while the treatment of single-area localized CUP remains controversial. We retrospectively reviewed the medical records of patients with CUP. SCCUP in women was classified according to several definitions. Based on the histologic type and site, they were classified into favorable and unfavorable subsets. We further divided SCCUP into two types (single and multiple areas) and reviewed treatment and efficacy. Among the 227 female CUP patients, 36 (15%) had SCCUP. The median age was 59.9 years (range, 31-90 years). Most patients (61.1%) had a good performance status. Of the SCCUP patients, 22 had cancer in a single area, and 14 in multiple areas. Single-area SCCUP was further divided into favorable (16 cases) and unfavorable subsets (6 cases). In the favorable subset, local treatment was predominant, and almost all cases had a good prognosis. Even in the unfavorable subset, local therapy was combined with systemic chemotherapy in only two cases, and four cases showed no recurrences. Local treatment may be effective for single-area SCCUP, even in the unfavorable subset.


Subject(s)
Carcinoma, Squamous Cell , Neoplasms, Unknown Primary , Humans , Female , Middle Aged , Neoplasms, Unknown Primary/drug therapy , Neoplasms, Unknown Primary/pathology , Retrospective Studies , Carcinoma, Squamous Cell/therapy , Prognosis , Treatment Outcome
4.
J Obstet Gynaecol Res ; 49(12): 2868-2874, 2023 Dec.
Article in English | MEDLINE | ID: mdl-37658751

ABSTRACT

AIM: There is no conclusive data on the prognosis of patients who receive paclitaxel-carboplatin (TC) plus bevacizumab therapy for advanced neuroendocrine carcinoma (NEC) of the uterine cervix, a rare histological subtype of cervical cancer. Thus, the aim of this study was to determine the efficacy of TC chemotherapy plus bevacizumab and bevacizumab single maintenance therapy for advanced NEC of the cervix. METHODS: This was a retrospective review of patients who received TC plus bevacizumab therapy for metastatic, recurrent, or persistent NEC of the cervix at seven institutions between 2015 and 2020. Relevant data were extracted from the patients' medical records and analyzed. RESULTS: Seven patients, including six with small-cell NEC and one with large-cell NEC, were included for analysis. Three patients received bevacizumab single maintenance therapy following TC plus bevacizumab therapy, whereas four patients did not receive bevacizumab single maintenance therapy. The median overall survival and progression-free survival of the patients who received bevacizumab single maintenance therapy were longer than those of the patients who did not receive the therapy (34 months vs. 10.5 months and 19 months vs. 5 months, respectively). However, the patients who received bevacizumab single maintenance therapy had received cisplatin-based chemotherapy previously. CONCLUSIONS: On the premise that cisplatin-based chemotherapy is administered as the first-line treatment for advanced NEC of the cervix, bevacizumab single maintenance therapy following TC plus bevacizumab may be considered the second- or third-line treatment. However, the risk of adverse events, such as intestinal perforation, should be discussed with patients.


Subject(s)
Carcinoma, Neuroendocrine , Uterine Cervical Neoplasms , Female , Humans , Bevacizumab/therapeutic use , Carboplatin , Paclitaxel/therapeutic use , Cisplatin/therapeutic use , Retrospective Studies , Uterine Cervical Neoplasms/pathology , Cervix Uteri/pathology , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Carcinoma, Neuroendocrine/drug therapy
5.
J Gynecol Oncol ; 34(5): e60, 2023 09.
Article in English | MEDLINE | ID: mdl-37170726

ABSTRACT

OBJECTIVE: Bevacizumab maintenance therapy following platinum-based combination chemotherapy for metastatic, recurrent, or persistent cervical cancer is not recommended as standard therapy. This pilot study aimed to evaluate the efficacy and safety of bevacizumab maintenance therapy and the contribution of the platinum-free interval to the efficacy of subsequent chemotherapy for advanced cervical cancer. METHODS: We retrospectively identified 115 patients with metastatic, recurrent, or persistent cervical cancer treated with platinum-paclitaxel chemotherapy plus bevacizumab at 7 institutions between 2015 and 2020. The primary endpoints were overall survival (OS) and progression-free survival (PFS) in patients who received bevacizumab maintenance therapy and those who did not. We also analyzed the adverse events associated with bevacizumab and survival time from the start of subsequent chemotherapy in both groups. RESULTS: Following platinum-paclitaxel plus bevacizumab chemotherapy, 34 patients received bevacizumab maintenance therapy and 81 patients did not. Of the 115 patients, 56 received chemotherapy for subsequent relapse. Although bevacizumab maintenance therapy prolonged PFS (median of 16.0 months vs. 9.0 months, p=0.041), significant differences were not observed in OS (p=0.374). Furthermore, bevacizumab maintenance therapy did not prolong OS and PFS after the start of subsequent chemotherapy (p=0.663 and p=0.136, respectively). Bevacizumab maintenance therapy significantly increased hypertension (p=0.035) and proteinuria (p=0.005) but did not cause complications leading to death. CONCLUSION: Bevacizumab single-maintenance therapy for advanced cervical cancer can be considered in selected cases, such as those with acceptable bevacizumab-related side effects. The outcomes of our study will likely contribute to decision-making regarding practical treatment strategies.


Subject(s)
Paclitaxel , Uterine Cervical Neoplasms , Female , Humans , Bevacizumab/therapeutic use , Uterine Cervical Neoplasms/pathology , Platinum/therapeutic use , Retrospective Studies , Pilot Projects , Antineoplastic Combined Chemotherapy Protocols/adverse effects
6.
Asian J Surg ; 46(9): 3575-3580, 2023 Sep.
Article in English | MEDLINE | ID: mdl-37142500

ABSTRACT

BACKGROUND/OBJECTIVE: This study determines whether the use of a portable interface pressure sensor (Palm Q) for robotic surgery could prevent compartment syndrome. METHODS: In the present single center, non-trial observational study, patients diagnosed with gynecological diseases between April 2015 and August 2020 treated with laparoscopic or robotic surgery were enrolled. We assessed 256 cases involving surgery performed in the lithotomy position with an operative time >4 h. The Palm Q device was placed preoperatively on both sides of the patients' lower legs. The pressure was measured every 30 min preoperatively and intraoperatively and adjusted to ≤30 mmHg. If the pressure reached ≥30 mmHg, the operation was stopped, the patient was repositioned, the leg position was released, the pressure was reduced to ≤30 mmHg, and the procedure was resumed. We compared the maximum creatine kinase levels of the Palm Q and non-Palm Q groups. We also analyzed the correlation between the patients' symptoms postoperatively (shoulder and leg pain) and compartment syndrome. RESULTS: Our data showed that immediate postoperative creatine kinase levels predict compartment syndrome. Propensity score matching of the 256 enrolled patients resulted in 92 cases (46 per group), balanced for age, body mass index, and lifestyle disease. Creatine kinase levels differed significantly between the Palm Q and non-Palm Q groups (p = 0.041). None of the patients in the Palm Q group experienced well-leg compartment syndrome complications. CONCLUSION: Palm Q can potentially help to prevent perioperative compartment syndrome.


Subject(s)
Compartment Syndromes , Laparoscopy , Robotic Surgical Procedures , Humans , Robotic Surgical Procedures/adverse effects , Compartment Syndromes/diagnosis , Compartment Syndromes/etiology , Compartment Syndromes/prevention & control , Supine Position , Laparoscopy/methods , Leg , Creatine Kinase
7.
Medicina (Kaunas) ; 59(5)2023 May 08.
Article in English | MEDLINE | ID: mdl-37241131

ABSTRACT

Background and Objectives: Tadalafil is expected to treat fetal growth restriction (FGR), a risk factor for stillbirth and neonatal morbidity. This study aimed to evaluate the fetal biometric growth pattern of fetuses with FGR treated with tadalafil by ultrasonographic assessment. Materials and Methods: This was a retrospective study. Fifty fetuses diagnosed with FGR and treated by maternal administration of tadalafil and ten controls who received conventional treatment at Mie University Hospital from 2015 to 2019 were assessed. Fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), and estimated fetal weight (EFW) at the start of treatment and at two weeks and four weeks of treatment were mainly assessed by ultrasound examination. The Wilcoxon signed-rank test was used to assess the measures. The Kyoto Scale of Psychological Development (KSPD) was used to assess the developmental prognosis on tadalafil-treated children at 1.5 years of corrected age (CA) and 3 years old. Results: The median gestational age at the start of treatment was 30 and 31 weeks in the tadalafil and control groups, respectively, and the median gestational age at delivery was 37 weeks in both groups. The Z-score of HC was significantly increased at 4 weeks of treatment (p = 0.005), and the umbilical artery resistance index was significantly decreased (p = 0.049), while no significant difference was observed in the control group. The number of cases with an abnormal score of less than 70 on the KSPD test was 19% for P-M, 8% for C-A, 19% for L-S, and 11% for total area at 1.5 years CA. At 3 years old, the respective scores were 16%, 21%, 16%, and 16%. Conclusions: Tadalafil treatment for FGR may maintain fetal HC growth and infants' neuro-developmental prognosis.


Subject(s)
Biometry , Fetal Growth Retardation , Pregnancy , Infant, Newborn , Female , Child , Infant , Humans , Tadalafil/therapeutic use , Fetal Growth Retardation/drug therapy , Retrospective Studies , Prognosis , Ultrasonography, Prenatal
8.
Soft Robot ; 10(5): 1028-1040, 2023 Oct.
Article in English | MEDLINE | ID: mdl-37231619

ABSTRACT

Legged robots have remarkable terrestrial mobility, but are susceptible to falling and leg malfunction during locomotion. The use of a large number of legs, as in centipedes, can overcome these problems, but it makes the body long and leads to many legs being constrained to contact with the ground to support the long body, which impedes maneuverability. A mechanism for maneuverable locomotion using a large number legs is thus desirable. However, controlling a long body with a large number of legs requires huge computational and energy costs. Inspired by agile locomotion in biological systems, this study proposes a control strategy for maneuverable and efficient locomotion of a myriapod robot based on dynamic instability. Specifically, our previous study made the body axis of a 12-legged robot flexible and showed that changing the body-axis flexibility produces pitchfork bifurcation. The bifurcation not only induces the dynamic instability of a straight walk but also a transition to a curved walk, whose curvature is controllable by the body-axis flexibility. This study incorporated a variable stiffness mechanism into the body axis and developed a simple control strategy based on the bifurcation characteristics. With this strategy, maneuverable and autonomous locomotion was achieved, as demonstrated by multiple robot experiments. Our approach does not directly control the movement of the body axis; instead, it controls body-axis flexibility, which significantly reduces computational and energy costs. This study provides a new design principle for maneuverable and efficient locomotion of myriapod robots.

9.
J Minim Invasive Gynecol ; 30(7): 531-532, 2023 07.
Article in English | MEDLINE | ID: mdl-37040815

ABSTRACT

OBJECTIVE: To demonstrate the surgical technique of retroperitoneal para-aortic lymphadenectomy to prevent peritoneal rupture in gynecologic malignant disease. In this video, the authors describe how to use a balloon trocar to create a safe and efficient working space without peritoneal rupture. DESIGN: A step-by-step video demonstration of a surgical technique. SETTING: Department of Gynecology and Obstetrics, Mie University, Tsu, Japan. INTERVENTIONS: Para-aortic lymphadenectomy is a part of most gynecologic oncology procedures for primary and recurrent gynecologic malignancies. There are 2 approaches to para-aortic lymphadenectomy: transperitoneal and retroperitoneal approaches. Although there are no significant differences between these approaches (such as in terms of the number of isolated lymph nodes or related complications), they are performed based on the operator's preference. The retroperitoneal approach is an unfamiliar surgical technique compared with usual laparotomy and laparoscopic surgery, and its disadvantages include a steeper learning curve for attaining proficiency. It is also difficult to develop the retroperitoneal space without a peritoneal rupture. In this video, we demonstrate the use of balloon trocars to create a retroperitoneal compartment. The patient was placed in the lithotomy position with the pelvis elevated at 5° to 10°. The left internal iliac approach, which is considered the standard approach, was used in this case (Fig 1). After identifying the left psoas muscles and the ureter crossing the common iliac artery, dissection of the left para-aortic lymph node was initiated (Supplemental Video 1, 2). CONCLUSION: Herein, we demonstrated a successful surgical technique for retroperitoneal para-aortic lymphadenectomy to prevent peritoneal ruptures.


Subject(s)
Carcinoma , Genital Neoplasms, Female , Laparoscopy , Female , Humans , Neoplasm Recurrence, Local/surgery , Lymph Node Excision/methods , Lymph Nodes/pathology , Dissection/methods , Laparoscopy/methods , Genital Neoplasms, Female/surgery , Surgical Instruments , Carcinoma/surgery
10.
Cancers (Basel) ; 14(18)2022 Sep 09.
Article in English | MEDLINE | ID: mdl-36139549

ABSTRACT

Our goal was to compare the treatment outcomes of open-abdominal radical hysterectomy (O-RH) and total laparoscopic hysterectomy (TLRH) with vaginal cuff creation and without using a uterine manipulator in stage IB1-B2 (tumor size < 4 cm) cervical cancer cases. In this retrospective multicenter analysis, 94 cervical cancer stage IB1-B2 patients who underwent O-RH or TLRH in six hospitals in Japan between September 2016 and July 2020 were included; 36 patients underwent TLRH. Propensity score matching was performed because the tumor diameter was large, and positive cases of lymph node metastases were included in the O-RH group due to selection bias. The primary endpoint was progression-free survival (PFS) and recurrence sites of TLRH and O-RH. PFS and OS (overall survival) were not significant in both the TLRH (n = 27) and O-RH (n = 27) groups; none required conversion to laparotomy. The maximum tumor size was <2 and ≥2 cm in 12 (44.4%) and 15 (55.6%) patients, respectively, in both groups. Reportedly, the TLRH group had lesser bleeding than the O-RH group (p < 0.001). Median follow-up was 33.5 (2−65) and 41.5 (6−75) months in the TLRH and O-RH groups, respectively. PFS and OS were not significantly different between the two groups (TLRH: 92.6%, O-RH: 92.6%; log-rank p = 0.985 and 97.2%, 100%; p = 0.317, respectively). The prognosis of early cervical cancer was not significantly different between TLRH and O-RH. Tumor spillage was prevented by creating a vaginal cuff and avoiding the use of a uterine manipulator. Therefore, TLRH might be considered efficient.

11.
Front Neural Circuits ; 16: 836121, 2022.
Article in English | MEDLINE | ID: mdl-35814485

ABSTRACT

Stride intervals in human walking fluctuate from one stride to the next, exhibiting statistical persistence. This statistical property is changed by aging, neural disorders, and experimental interventions. It has been hypothesized that the central nervous system is responsible for the statistical persistence. Human walking is a complex phenomenon generated through the dynamic interactions between the central nervous system and the biomechanical system. It has also been hypothesized that the statistical persistence emerges through the dynamic interactions during walking. In particular, a previous study integrated a biomechanical model composed of seven rigid links with a central pattern generator (CPG) model, which incorporated a phase resetting mechanism as sensory feedback as well as feedforward, trajectory tracking, and intermittent feedback controllers, and suggested that phase resetting contributes to the statistical persistence in stride intervals. However, the essential mechanisms remain largely unclear due to the complexity of the neuromechanical model. In this study, we reproduced the statistical persistence in stride intervals using a simplified neuromechanical model composed of a simple compass-type biomechanical model and a simple CPG model that incorporates only phase resetting and a feedforward controller. A lack of phase resetting induced a loss of statistical persistence, as observed for aging, neural disorders, and experimental interventions. These mechanisms were clarified based on the phase response characteristics of our model. These findings provide useful insight into the mechanisms responsible for the statistical persistence of stride intervals in human walking.


Subject(s)
Gait , Walking , Gait/physiology , Humans , Walking/physiology
12.
Anticancer Res ; 42(8): 4165-4171, 2022 Aug.
Article in English | MEDLINE | ID: mdl-35896225

ABSTRACT

BACKGROUND/AIM: Adverse events associated with long-term bevacizumab administration for ovarian cancer have been poorly documented in Japan. This study aimed to evaluate the adverse events of bevacizumab combined with chemotherapy for treating primary and recurrent epithelial ovarian cancer in Japan. PATIENTS AND METHODS: In this single-center retrospective study, we analyzed data of patients with advanced and recurrent epithelial ovarian cancer treated with bevacizumab and chemotherapy between January 2013 and November 2019. Statistical analyses were performed using the Fisher's exact test and Kaplan-Meier method. RESULTS: A total of 46 patients were included and the follow-up time was 30 months. The median duration of bevacizumab treatment was 14 months, and the median total dose of bevacizumab was 247.5 mg/kg. The most common adverse events were hypertension (n=30; 65.2%) and proteinuria (n=24; 49%) in all grades. The onset of hypertension and proteinuria occurred at a median of 2 months and 14 months after treatment initiation in all grades, respectively. Gastrointestinal perforation occurred significantly more frequently in patients with a history of radiation therapy. CONCLUSION: This study included cases of primary advanced and recurrent epithelial ovarian cancer, and had a longer observation period and reported more adverse events of bevacizumab with chemotherapy than previous reports. The administration of bevacizumab therapy in patients with a history of radiation should be carefully considered due to increased chances of gastrointestinal perforation.


Subject(s)
Hypertension , Ovarian Neoplasms , Antineoplastic Combined Chemotherapy Protocols/adverse effects , Bevacizumab/adverse effects , Carcinoma, Ovarian Epithelial/drug therapy , Female , Humans , Hypertension/chemically induced , Hypertension/drug therapy , Neoplasm Recurrence, Local/drug therapy , Ovarian Neoplasms/drug therapy , Ovarian Neoplasms/etiology , Proteinuria/chemically induced , Proteinuria/drug therapy , Retrospective Studies
13.
Sci Rep ; 12(1): 166, 2022 01 07.
Article in English | MEDLINE | ID: mdl-34997003

ABSTRACT

This study evaluated the influence of positive peritoneal cytology (PPC) on the prognosis of patients with stage IA endometrial cancer, and the usefulness of adjuvant chemotherapy in their treatment. We retrospectively analyzed the data of patients with stage IA endometrial cancer admitted in our hospital between 2005 and 2015. Among 989 patients who underwent peritoneal cytology, 135 (13.7%) had PPC. Multivariate analysis extracted several independent risk factors for recurrence in stage IA patients, including those with PPC. Adjuvant chemotherapy did not cause a significant difference in the 5-year relapse-free survival rate in patients with PPC (p = 0.78). Similarly, the 5-year recurrence-free survival rate with or without chemotherapy was not different among type II cancer patients (p = 0.11). However, the baseline risk of 5-year relapse-free survival without chemotherapy in patients with PPC and type II was very low (66.7%). While PPC was an independent risk factor for recurrence in stage IA endometrial cancer, adjuvant chemotherapy did not influence the survival rate in patients with PPC. While it is controversial whether adjuvant chemotherapy should be administered in stage IA uterine cancer with only PPC as a prognostic factor, it should be considered for early-stage patients who have multiple risk factors for recurrence.


Subject(s)
Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Endometrial Neoplasms/drug therapy , Hysterectomy , Peritoneum/pathology , Adult , Aged , Aged, 80 and over , Antineoplastic Combined Chemotherapy Protocols/adverse effects , Biopsy , Chemotherapy, Adjuvant , Disease Progression , Endometrial Neoplasms/mortality , Endometrial Neoplasms/pathology , Female , Humans , Hysterectomy/adverse effects , Hysterectomy/mortality , Middle Aged , Neoplasm Metastasis , Neoplasm Recurrence, Local , Neoplasm Staging , Predictive Value of Tests , Progression-Free Survival , Retrospective Studies , Risk Assessment , Risk Factors , Time Factors
14.
Sci Rep ; 11(1): 1441, 2021 01 14.
Article in English | MEDLINE | ID: mdl-33446912

ABSTRACT

After pelvic lymphadenectomy (PLA), pelvic vessels, nerve, and ureter are skeletonized. Internal hernias beneath the skeletonized pelvic structure following pelvic lymphadenectomy (IBSPP) are a rare complication following PLA. To the best of our knowledge, only 12 IBSPP cases have been reported and clinical details on such hernias remain unknown. The aim of the study was to investigate the incident and etiology of IBSPP. 1313 patients who underwent open or laparoscopic pelvic lymphadenectomy were identified from our database. A retrospective review was performed. Mean follow-up period was 33.9 months. A total of 12 patients had IBSPP. Multivariate analysis of laparoscopic surgeries group as compared to open surgeries group, para-aortic lymphadenectomy rate, number of dissected lymph nodes by PLA, antiadhesive material use rate, and blood loss were lower in laparoscopic surgeries group: odd ratio (OR) = 0.13 [95% confidence interval (CI) 0.08-0.19], and OR = 0.70 [95% CI 0.50-0.99], OR = 0.17 [95% CI 0.10-0.28], OR = 0.93 [95% CI 0.92-0.94]. However, no significant difference was observed in the incidence of IBSPP between laparoscopic surgery (1.0%) and open surgery (0.8%). All IBSPP occurred in the right pelvic space. These findings may contribute to the development of prevention methods for this disease.


Subject(s)
Genital Neoplasms, Female , Hernia , Intestine, Small , Laparoscopy/adverse effects , Lymph Node Excision/adverse effects , Postoperative Complications/epidemiology , Adult , Female , Follow-Up Studies , Genital Neoplasms, Female/epidemiology , Genital Neoplasms, Female/surgery , Hernia/epidemiology , Hernia/etiology , Humans , Middle Aged , Retrospective Studies
15.
Bioinspir Biomim ; 15(5): 055002, 2020 07 15.
Article in English | MEDLINE | ID: mdl-32396880

ABSTRACT

Passive dynamic walking is a model that walks down a shallow slope without any control or input. This model has been widely used to investigate how humans walk with low energy consumption and provides design principles for energy-efficient biped robots. However, the basin of attraction is very small and thin and has a fractal-like complicated shape, which makes producing stable walking difficult. In our previous study, we used the simplest walking model and investigated the fractal-like basin of attraction based on dynamical systems theory by focusing on the hybrid dynamics of the model composed of the continuous dynamics with saddle hyperbolicity and the discontinuous dynamics caused by the impact upon foot contact. We clarified that the fractal-like basin of attraction is generated through iterative stretching and bending deformations of the domain of the Poincaré map by sequential inverse images. However, whether the fractal-like basin of attraction is actually fractal, i.e., whether infinitely many self-similar patterns are embedded in the basin of attraction, is dependent on the slope angle, and the mechanism remains unclear. In the present study, we improved our previous analysis in order to clarify this mechanism. In particular, we newly focused on the range of the Poincaré map and specified the regions that are stretched and bent by the sequential inverse images of the Poincaré map. Through the analysis of the specified regions, we clarified the conditions and mechanism required for the basin of attraction to be fractal.


Subject(s)
Fractals , Walking/psychology , Biomechanical Phenomena , Energy Metabolism/physiology , Foot/physiology , Gait , Hip Joint/physiology , Humans , Leg , Models, Biological
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