A computer-based simulation of vacuum extraction during childbirth

Vacuum extraction is an instrumental method used in obstetrics when childbirth labour fails to progress. The instrument used during vacuum extraction is the ventouse. It comprises of a suction cup attached to the fetal scalp through a vacuum, and a chord or chain to apply a traction force to expedite the delivery of the baby. It is claimed in the obstetric literature that incorrect placement of the cup, in particular across the anterior fontanelle, may cause serious injury to the fetal scalp. Here we put this theory to the test using a computerised simulation with finite element analysis. The results show substantially larger soft tissue deformations near the anterior fontanelle which may constitute quantitative evidence of qualitative assessments reported in the obstetric literature

A Haptic User Interface to Assess the Mobility of the Newborn's Neck

A virtual reality program has been developed to assess the strength and flexibility of a computer based model of a term fetus or newborn baby's neck. The software has a haptic/force feedback user interface which allows clinical experts to adjust the mechanical properties, including range of motion and mechanical stiffness of a newborn neck model, at runtime. The developed software was assessed by ten clinical experts in obstetrics. The empirically obtained stiffness and range of motion values corresponded well with values reported in the literature

A computer‑based simulation of childbirth using the partial Dirichlet–Neumann contact method with total Lagrangian explicit dynamics on the GPU

During physiological or ‘natural’ childbirth, the fetal head follows a distinct motion pattern—often referred to as the cardinal movements or ‘mechanisms’ of childbirth—due to the biomechanical interaction between the fetus and maternal pelvic anatomy. The research presented in this paper introduces a virtual reality-based simulation of physiological childbirth. The underpinning science is based on two numerical algorithms including the total Lagrangian explicit dynamics method to calculate soft tissue deformation and the partial Dirichlet–Neumann contact method to calculate the mechanical contact interaction between the fetal head and maternal pelvic anatomy. The paper describes the underlying mathematics and algorithms of the solution and their combination into a computer-based implementation. The experimental section covers first a number of validation experiments on simple contact mechanical problems which is followed by the main experiment of running a virtual reality childbirth. Realistic mesh models of the fetus, bony pelvis and pelvic floor muscles were subjected to the intra-uterine expulsion forces which aim to propel the virtual fetus through the virtual birth canal. Following a series of simulations, taking variations in the shape and size of the geometric models into account, we consistently observed the cardinal movements in the simulator just as they happen in physiological childbirth. The results confirm the potential of the simulator as a predictive tool for problematic childbirths subject to patient-specific adaptations

An engineering perspective of vacuum assisted delivery devices in obstetrics: A review

Complications during childbirth result in the need for clinicians to use ‘assisted delivery’ in over 12% of cases (UK). After more than 50 years in clinical practice, vacuum assisted delivery (VAD) devices remain a mainstay in physically assisting child delivery; sometimes preferred over forceps due to their ease of use and reduced maternal morbidity. Despite their popularity and enduring track-record, VAD devices have shown little evidence of innovation or design change since their inception. In addition, evidence on the safety and functionality of VAD devices remains limited but does present opportunities for improvements to reduce adverse clinical outcomes. Consequently in this review we examine the literature and patent landscape surrounding VAD biomechanics, design evolution and performance from an engineering perspective, aiming to collate the limited but valuable information from a disparate field and provide a series of recommendations to inform future research into improved, safer, VAD systems

In Vitro Skin-Tissue Experiment for Increased Realism in Open Surgery Simulations

In-vitro uniaxial stress tests were conducted on samples of healthy human skin, obtained as a result of plastic surgical procedures. Pairs of test strips were cut from each sample to assess the effects of local orthotropy. Each strip was then subjected to constant strain-rate tensile testing, to observe its stress/strain behaviour. Typical maximal values for Young's modulus were found to be approximately 15.3MPa and 3.48Mpa for Langer-aligned and perpendicular test strips, respectively

A Hyperelastic Finite Element Model of Human Skin for Interactive Real-Time Surgical Simulation

A finite element model of human skin is proposed for future use in an interactive real-time surgical simulation to teach surgeons procedures such as facial reconstruction using skin flap repair. For this procedure, skin is cut into flaps that are stretched to cover openings in the face. Thus, the model must recreate the visual, haptic and force feedback expected by the surgeon. To develop the finite element model, a series of in vitro experiments were conducted on samples of human skin, subjected to uni-axial and planar tensile straining. Reduced polynomial hyperelastic materials were found to fit many of the samples stress-strain data well. Finally, an explicit dynamic finite element mesh was developed based on the fitted hyperelastic material models. A total Lagrangian formulation with the half-step central difference method was employed to integrate the dynamic equation of motion of the mesh. The mesh was integrated into two versions of a real-time skin simulator: a single-threaded version running on a computer's main central processing unit and a multithreaded version running on the computer's graphics card. The latter was achieved by exploiting recent advances in programmable graphics technology