Paper Submission & Registration
8th Dutch Bio-Medical Engineering Conference
12:30   Surgery & Intervention - I
Chair: Bart Verkerke
15 mins
Subtrochanteric fracture location effect on surgical management using proximal femoral nail antirotation (PFNA) versus dynamic hip screw (DHS): a finite element method analysis
Omid Daqiq, Hans Hendrickx
Abstract: Introduction: No previous literature found regarding the effects of fracture location in the subtrochanteric region (STR) for subtrochanteric fracture (STF) management. Therefore, “this simulation study, using numerical Finite Element Method (FEM), analysis the impact of fracture location in STR using Proximal Femoral Nail Antirotation (PFNA) versus Dynamic Hip Screw (DHS) implants.” Methods: Using Solidworks software, a normal femur CT-image was used to create a FEM-model. Then a straight-line fracture added at STR. Stepwise, the fracture was lowered from 0.5 to 4.5 cm below the lesser trochanter (LT) in 9 steps. PFNA- and DHS-model were implemented for fracture management. FEM-models were verified using mesh refining. Results: DHS gave lower von-Mises stress for proximal STF’s (until 3.5 cm below LT), where PFNA illustrated lower stress for distal fractures (from 4 cm below LT). Lower von-Mises stress means lower assembly failure or deformation. Mean von-Mises stress ratio [between PFNA versus DHS] also decreased from proximal (1.93) to distal (0.47) of STR, with intersection cross-point at 3.8 cm below LT. Maximum von-Mises stress remains at a similar position for all DHS locations: on distal locking screw. However, it varies for PFNA: for location 1-8 is at the distal locking screw and for location 9 at the lag screw. Conclusion: This simulation study shows that for uncomplicated straight-line STF, DHS is more favourable for fractures till 3.8 cm from LT; below this region is PFNA more suitable. Therefore, the STF location needs consideration for selecting proper osteosynthesis implants.
15 mins
Design of a flexible ovipositor inspired tissue-transporting mechanism
Esther de Kater, Aimée Sakes, Paul Breedveld
Abstract: During minimally invasive procedures, tissue damage can be limited by using smaller incisions or by using naturally occurring body orifices to reach the intervention site. During these procedures, the need can arise to transport tissue. Think of a biopsy or the removal of polyps. This calls for a novel tissue-transporting mechanism that is flexible such that it can be used in these minimally invasive procedures. Currently either suction based techniques or forceps are used. However, both show suboptimal behaviour. Friction-based transport, which is based on the egg laying principle of parasitoid wasps, is not prone to these sub-optimal behaviour modes and has been demonstrated in a rigid mechanism. To allow this form of transport to be used in a wider range of minimally invasive procedures, a flexible tissue-transporting mechanism was developed that uses the same friction-based transport method. The flexible shaft of the mechanism consists of ring magnets and wire ropes that can translate by rotating a cam. The translating motion of the wire ropes is similar to the motion of the valves in the wasp ovipositor and is used to transport the tissue. The developed flexible tissue-transporting mechanism was able to transport 10w% gelatine tissue phantoms with the shaft in straight and curved position (30o and 60o) and in vertical orientation transporting against gravity. It was found that the transport rate could be increased by increasing the rotational velocity of the cam. A rotational velocity of 25 RPM resulted in a transport rate of 0.8 mm/s and increasing the rotation velocity of the cam to 80 RPM increased the transport rate to 2.2 mm/s. The flexible tissue-transporting mechanism shows that friction-based transport can be applied in a flexible mechanism and has the potential to be used in a range of minimally invasive procedures.
15 mins
Developing an ambient sensor support system for continence care management: A lab evaluation
Hannelore Strauven, Hans Hallez, Vero Vanden Abeele, Bart Vanrumste
Abstract: Introduction. Over 50% of nursing home residents suffer from incontinence [1]. Effort has been made to improve continence care management in nursing homes automatically. Hence, most research mainly focused on wearables, such as the development of smart incontinence wear [2], [3]. In our previous work [4], we discussed the design and development of an ambient system to monitor urinary incontinence episodes. Here, we evaluated an improved version of the system in a controlled climate room. Materials and method. For the ambient monitoring of urinary incontinence episodes, a sensor system is developed with an ammonia (NH3) gas sensor [5]. In a climate controlled room (21 °C and 50 %RH), a measurement setup was established to simulate a sleeping incontinent nursing home resident. A mannequin was put to bed under the sheets, wearing different types incontinence materials (i.e., diaper or two-fold system). Around the pelvic area of the mannequin, a heat pad at body temperature (37 °C) was attached. Via a tube, mounted in the incontinence material, an NH3 solution of 24 ppm was gradually added to mimic incontinence episodes. The sensor system was placed under the sheets, close to the pelvic area of the mannequin for validation. Results. The output signal of the NH3 gas sensor varied between the different types of incontinence material. For a diaper, no change in the sensor signal could be noticed when adding the NH3 solution to the material. For a two-fold system, the sensor signal altered when the material became highly saturated. If the mannequin and sensor system were not covered with the sheets, no alteration in the output signal could be observed in relation to the added NH3 solution. Discussion and conclusion. An ambient sensor system is presented to support continence care management in nursing homes by monitoring urinary incontinence episodes while sleeping. The sensor system is able to detect a highly saturated two-fold incontinence material when under the sheets. However, this could not be observed for a diaper or when the setup was not covered with the bed sheets. Further research should therefor detail the possibilities and limitations of the system.
15 mins
Initial experimental validation of bone material identification model
Jack Wilkie, Knut Möller
Abstract: INTRODUCTION: Bone screws are widely used in orthopaedic surgery for stabilising fractures and securing orthopaedic implants. Correct tightening of bone screws is important to prevent thread stripping with over-tightening, or loosening/insufficient stabilisation with under-tightening. As the dynamics of bone screw insertion are dependant on the bone material properties, it has been proposed that it is possible to determine the bone material properties by monitoring the screwing process, and fitting the data to a model using parameter identification. The bone material properties may then be used in a predictive model to estimate the optimal torque. Previous work has focused on developing and simulating the model. This work extends this by testing with experimental data. METHOD: Due to the expected low importance of elasticity, the model previously used in [1] was modified to assume rigidity. This simplified the parameter identification algorithm, as linear least-squares could be used instead of simulated annealing. The experimental setup consisted of a stepper motor and torque sensor driving a wood screw into a pre-drilled hole in a block of wood. Two velocity profiles were used; one continuously inserting the screw, and the other followed a repeating trapezoidal pattern to mimic hand screwing. The torque and rotation data were then used to identify the strength of the wood by using them to identify the parameters of the model. The dimensions of the hole (3-mm diameter) and the screw (5-mm major diameter, 15-degree thread angle, 2-mm thread pitch) were considered a priori information, and the zero-displacement offset was adjusted to match the data. RESULTS: Insertion with constant speed gave identified values of 22.8 and 25.8 MPa. Insertion with trapezoidal velocity profile give identified values of 24.8 and 25.1 MPa. CONCLUSIONS: The identified values are within the reasonable range of compression strength for pine wood, which is 16-50 MPa [2]; this is dependent on the exact species, and may vary further with moisture content (assumed 12%, not measured). This demonstrates that this method can identify material strength properties; however, the degree of accuracy is uncertain, due to the uncertainty in the true value, and limited scope of the testing.

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