Design and stepwise user evaluation of an ergonomic 2 DOF arthroscopic cutter

The goal of this study was to determine the preferred handle design for two degrees of freedom steerable arthroscopic cutter by performing a two-step development approach. The expected usefulness and usability of control components of three entirely different handles were defined by an on-line survey with 101 students and the actual control by a standardised laboratory study with mock-up models by 16 students. The preferred handle design was integrated in a full functional prototype and optimized by 10 experts performing a meniscectomy on human cadaver knees. Students (survey 70% and task 91%) expected the same control behaviour as the experts (60%): steering a wheel to the right should evoke tip steering to the right regardless the orientation of the beak and moving a ring lever towards the handle’s centre point should evoke closure of the tip. Development of surgical instruments can benefit from expected control behavior based on daily life tools, but requires expert involvement for specific surgical tasks and context

The preferred technique for knee synovium biopsy and synovial fluid arthrocentesis

For knee osteoarthritis and related conditions, analysis of biomarkers hold promise to improve early diagnosis and/or offer patient-specific treatment. To compare biomarker analyses, reliable, high-quality biopsies are needed. The aim of this work is to summarize the literature on the current best practices of biopsy of the synovium and synovial fluid arthrocentesis. Therefore, PubMed, Embase and Web of Science were systematically searched for articles that applied, demonstrated, or evaluated synovial biopsies or arthrocentesis. Expert recommendations and applications were summarized, and evidence for superiority of techniques was evaluated. Thirty-one studies were identified for inclusion. For arthrocentesis, the superolateral approach in a supine position, with a 0°-30° knee flexion was generally recommended. 18-gage needles, mechanical compression and ultrasound-guidance were found to give superior results. For blind and image-guided synovial biopsy techniques, superolateral and infrapatellar approaches were recommended. Single-handed tools were preconized, including Parker-Pearson needles and forceps. Sample quantity ranged approximately from 2 to 20. Suggestions were compiled for arthrocentesis regarding approach portal and patient position. Further evidence regarding needle size, ultrasound-guidance and mechanical compression were found. More comparative studies are needed before evidence-based protocols can be developed

Hydraulic actuator selection for a compliant surgical bone drill: A theoretical approach

A compliant bone drill provides advantages over conventional straight drills, because it allows surgical access via a minimally invasive approach. Hydropower allows the transfer of pressurized water with a compliant hose. The goal is to select the hydraulic actuator for this compliant bone drill by reviewing existing actuator principles. The selection was performed with a theoretical analysis. Design requirements were derived from a challenging minimally invasive bone drill procedure, and were set: a speed of 750 rpm, a torque of 0.015 Nm and a maximum dimensional volume of 5 mm × 5 mm × 10 mm to drill Ø 1.5 mm holes in human bone. A literature search was performed. For each actuator, the fluid flow and the required pressure difference were described as a function of the actuator dimensions and the rotational speed. Selection of the actuator was performed by it meeting the set output power, the torque, realistic input dimensions, and requiring the lowest pressure and number of parts. Existing literature provided six hydraulic actuators: external gear motor, gear ring motor, axial turbine, radial turbine, Pelton wheel, and Ossberger turbine. The latter four are hydrodynamic turbines, which could not meet the rotational speed. The external gear motor was selected for its lowest required pressure difference (11.5×105 Pa) and design simplicity. This theoretical design approach can be used for other applications.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Medical Instruments & Bio-Inspired Technolog

Werktuigkundige Systemen

Het boek Werktuigkundige Systemen is een compacte inleiding op het systeemdenken in de werktuigbouwkunde, met nadruk op inzicht en grafische methoden, gelardeerd met prikkelende werkingsprincipes en constructie-elementen. Velen merken dat ze nog lang nadat ze het vak gedaan hebben dit boek als naslagwerk gebruiken en het steeds meer gaan waarderen, ook omdat het boek de basis legt voor veel vervolgvakken en projecten.Het boek is al jarenlang in gebruik bij eerstejaars studenten Werktuigbouwkunde aan de TU Delft. Diverse docenten gebruiken het bij vakken of ontwerp­projecten.De oorsprong van dit boek in de tachtiger jaren is een college geweest, waarin op eenvoudige wijze de werking van bestaande apparaten en machines werd geanalyseerd. In een later stadium is deze stof uitgebreid met een aantal constructieve bijzonderheden. Daarbij heeft de systeemleer en de modelvorming een belangrijke basis gevormd.Meer uitgebreid: De fundamentele principes bij ontwerpen komen in dit boek ‘Werktuigkundige Systemen’ naar voren. Zo wordt de systeemleer toegepast op werktuigkundige constructies en wordt in het hoofdstuk over modelvorming de weg aangegeven om de complexe fysische werkelijkheid om te zetten in een overzichtelijk werkingsinzicht. Ook onder meer mechanische versterkers komen aan bod en is een hoofdstuk gewijd aan de belangrijke begrippen sterkte en stijfheid. Er is ruim aandacht gegeven aan wrijving en weerstand, alsmede aan de middelen om deze te vergroten of te verkleinen. Omdat veren tot de essentiële werktuigonderdelen behoren is een hoofdstuk gewijd aan de toepassing van veren in een ontwerp. Hier is het belangrijke begrip voorspanning behandeld. Het onderwerp Aandrijving wordt behandeld en daarin wordt aangegeven op welke wijze een motor met een last moet worden gekoppeld. Het hoofdstuk over comparalogie laat de problemen zien bij het verkleinen of vergroten van reeds bestaande constructies en bij de vaak noodzakelijke modelproeven. Het hoofdstuk over energie ten slotte, geeft een inleiding in de ‘warme werktuigbouwkunde’. Hierin is een technologisch rendement beschreven dat aangeeft in welke mate een machine warmtetechnisch goed is geconstrueerd.Dit boek kan gebruikt worden bij verschillende soorten technisch hoger onderwijs; zowel door het globale overzicht van de gehele werktuigbouwkunde, de introductie van systeemleer en modelvorming, als door de specialistische behandeling van enkele bijzondere onderwerpen.Mechatronic Systems Desig

Translation of 3D Anatomy to 2D Radiographic Angle Measurements in the Ankle Joint: Validity and Reliability

Background: The objective consisted of 2 elements, primarily to define 2 bone geometry variations of the ankle that may be of prognostic value on ankle instability and secondly to translate these bone variations from a 3D model to a simple 2D radiographic measurement for clinical use. Methods: The 3D tibial and talar shape differences derived from earlier studies were translated to two 2D radiographic parameters: the medial malleolar height angle (MMHA) and talar convexity angle (TCA) respectively to ensure clinical use. To assess validity, the MMHA and TCA were measured on 3D polygons derived from lower leg computed tomographic (CT) scans and 2D digitally reconstructed radiographs (DRRs) of these polygons. To assess reliability, the MMHA and TCA were measured on standard radiographs by 2 observers calculating the intraclass correlation coefficient (ICC). Results: The 3D angle measurements on the polygons showed substantial to excellent agreement with the 2D measurements on DRR for both the MMHA (ICC 0.84-0.93) and TCA (ICC 0.88-0.96). The interobserver reliability was moderate with an ICC of 0.58 and an ICC of 0.64 for both the MMHA and TCA, respectively. The intraobserver reliability was excellent with an ICC of 0.96 and 0.97 for the MMHA and the TCA, respectively. Conclusion: Two newly defined radiographic parameters (MMHA and TCA) are valid and can be assessed with excellent intraobserver reliability on standard radiographs. The interobserver reliability was moderate and indicates training is required to ensure uniformity in measurement technique. The current method may be used to translate more variations in bone shape prior to implementation in clinical practice. Level of Evidence: Level III, cohort study

Translation of 3D Anatomy to 2D Radiographic Angle Measurements in the Ankle Joint: Validity and Reliability

Background: The objective consisted of 2 elements, primarily to define 2 bone geometry variations of the ankle that may be of prognostic value on ankle instability and secondly to translate these bone variations from a 3D model to a simple 2D radiographic measurement for clinical use. Methods: The 3D tibial and talar shape differences derived from earlier studies were translated to two 2D radiographic parameters: the medial malleolar height angle (MMHA) and talar convexity angle (TCA) respectively to ensure clinical use. To assess validity, the MMHA and TCA were measured on 3D polygons derived from lower leg computed tomographic (CT) scans and 2D digitally reconstructed radiographs (DRRs) of these polygons. To assess reliability, the MMHA and TCA were measured on standard radiographs by 2 observers calculating the intraclass correlation coefficient (ICC). Results: The 3D angle measurements on the polygons showed substantial to excellent agreement with the 2D measurements on DRR for both the MMHA (ICC 0.84-0.93) and TCA (ICC 0.88-0.96). The interobserver reliability was moderate with an ICC of 0.58 and an ICC of 0.64 for both the MMHA and TCA, respectively. The intraobserver reliability was excellent with an ICC of 0.96 and 0.97 for the MMHA and the TCA, respectively. Conclusion: Two newly defined radiographic parameters (MMHA and TCA) are valid and can be assessed with excellent intraobserver reliability on standard radiographs. The interobserver reliability was moderate and indicates training is required to ensure uniformity in measurement technique. The current method may be used to translate more variations in bone shape prior to implementation in clinical practice. Level of Evidence: Level III, cohort study.Biomaterials & Tissue Biomechanic

Arthroscopic localization of the ulnar nerve behind the medial capsule is unreliable

Purpose: Ulnar nerve injury is the most common neurologic complication of elbow arthroscopy. The purpose of this cadaveric study was to quantify the ability of surgeons to locate the ulnar nerve behind the posteromedial capsule during elbow arthroscopy using sole arthroscopic vision. Methods: Twenty-one surgeons were asked to pin the ulnar nerve at the medial gutter and the posteromedial compartment using arthroscopic visualization of the medial capsule only. Pinning of the ulnar nerve was performed from extra-articular. Then, the cadaveric specimens were dissected and the shortest distances between the pins and ulnar nerve measured. Results: Median pin-to-nerve distances at the medial gutter and posteromedial compartment were 0 mm (interquartile range [IQR], 0-3 mm) and 2 mm (IQR, 0-6 mm), respectively. The ulnar nerve was pinned by 11/21 surgeons (52%) at the medial gutter, and 7/21 surgeons (33%) at the posteromedial compartment. Three of 21 surgeons (14%) pinned the ulnar nerve at both the medial gutter and the posteromedial compartment. Surgeon's experience and operation volume did not affect these outcomes (P >.05). Conclusions: Surgeons' ability to locate the ulnar nerve behind the posteromedial capsule using sole arthroscopic visualization, without external palpation, is poor. We recommend to proceed carefully when performing arthroscopic procedures in the posteromedial elbow, and identify and mobilize the ulnar nerve prior to any posteromedial capsular procedures