G. J. M. Tuijthof

Behavior of arthroscopic irrigation systems

In the literature, no consensus exists about optimal irrigation of joints during arthroscopic operations. The goal of this paper is to study the behavior of irrigation systems resulting in the proposal of guidelines for optimal irrigation. To this end, optimal irrigation is defined as the steady state of irrigation of a joint in which a sufficient positive intra-articular pressure and a sufficient flow are maintained. A model of the complete irrigation system was created to schematically elucidate the behavior of pump systems. Additionally, clinical experiments were performed during arthroscopic knee operations in which the pressure at different locations and the irrigation flow were measured. The combination of model prediction and clinical results could well be used to derive guidelines, since the clinical results, which showed considerable variation, were used to verify the model, and the model could be used to explain the typical trends. The main findings are twofold the set pressure is always higher than the intra-articular pressure, and the scope–sheath combination has a significant influence on irrigation control, because of its large restriction. Based on the results, we advice to increase the set pressure during active suction, and to include the sheath–scope combination in the control loop.

Validation of the ArthroS virtual reality simulator for arthroscopic skills

AbstractPurpose Virtual reality simulator training has become important for acquiring arthroscopic skills. A new simulator for knee arthroscopy ArthroS™ has been developed. The purpose of this study was to demonstrate face and construct validity, executed according to a protocol used previously to validate arthroscopic simulators.MethodsTwenty-seven participants were divided into three groups having different levels of arthroscopic experience. Participants answered questions regarding general information and the outer appearance of the simulator for face validity. Construct validity was assessed with one standardized navigation task. Face validity, educational value and user friendliness were further determined by giving participants three exercises and by asking them to fill out the questionnaire.ResultsConstruct validity was demonstrated between experts and beginners. Median task times were not significantly different for all repetitions between novices and intermediates, and between intermediates and experts. Median face validity was 8.3 for the outer appearance, 6.5 for the intra-articular joint and 4.7 for surgical instruments. Educational value and user friendliness were perceived as nonsatisfactory, especially because of the lack of tactile feedback.ConclusionThe ArthroS™ demonstrated construct validity between novices and experts, but did not demonstrate full face validity. Future improvements should be mainly focused on the development of tactile feedback. It is necessary that a newly presented simulator is validated to prove it actually contributes to proficiency of skills.

Influence of tool geometry on drilling performance of cortical and trabecular bone

Minimally invasive surgery poses high demands on tool design. The goal was to measure the influence of drill bit geometry on maximum thrust forces required for drilling, and compare this relative to the known influence of feed rate and bone composition. Blind holes were drilled perpendicular to the iliac crest up to 10 mm depth in cadaveric pelvic bones of 20 pigs (adolescent) and 11 goats (full grown) with eight substantially different drill bits of ∅ 3-3.2 mm. Subsequently, boreholes were drilled perpendicular to the ilium with the same drill bits at three different feed rates (0.58 mm/s, 0.83 mm/s, 1.08 mm/s). The mean maximum thrust force ranges from 10 to 110 N for cortical bone, and from 3 to 65 N for trabecular bone. The results show that both drill bit geometry and feed rate have a significant influence on the maximum thrust forces, with a dominant influence of drill bit geometry in terms of shape of the flutes, sharpness of cutting edges and value of point angle. The differences in thrust forces between cortical and trabecular bone are substantial for all measured conditions. The measured values can be used for drill design.

Steerable Mechanical Joint for High Load Transmission in Minimally Invasive Instruments

As minimally invasive operations are performed through small portals, the limited manipulation capability of straight surgical instruments is an issue. Access to the pathology site can be challenging, especially in confined anatomic areas with few available portals, such as the knee joint. The goal in this paper is to present and evaluate a new sideways-steerable instrument joint that fits within a small diameter and enables transmission of relative high forces (e. g., for cutting of tough tissue). Meniscectomy was selected as a target procedure for which quantitative design criteria were formulated. The steering mechanism consists of a crossed configuration of a compliant rolling-contact element that forms the instrument joint, which is rotated by flexural steering beams that are configured in a parallelogram mechanism. The actuation of cutting is performed by steel wire that runs through the center of rotation of the instrument joint. A prototype of the concept was fabricated and evaluated technically. The prototype demonstrated a range of motion between -22 degrees and 25 degrees with a steering stiffness of 17.6 Nmm/rad (min 16.9 - max 18.2 Nmm/rad). Mechanical tests confirmed that the prototype can transmit an axial load of 200 N on the tip with a maximum parasitic deflection of 4.4 degrees. A new sideways steerable mechanical instrument joint was designed to improve sideways range of motion while enabling the cutting of strong tissues in a minimally invasive procedure. Proof of principle was achieved for the main criteria, which encourages the future development of a complete instrument.[DOI: 10.1115/1.4004649]

How valid are commercially available medical simulators

Background Since simulators offer important advantages, they are increasingly used in medical education and medical skills training that require physical actions. A wide variety of simulators have become commercially available. It is of high importance that evidence is provided that training on these simulators can actually improve clinical performance on live patients. Therefore, the aim of this review is to determine the availability of different types of simulators and the evidence of their validation, to offer insight regarding which simulators are suitable to use in the clinical setting as a training modality. Summary Four hundred and thirty-three commercially available simulators were found, from which 405 (94%) were physical models. One hundred and thirty validation studies evaluated 35 (8%) commercially available medical simulators for levels of validity ranging from face to predictive validity. Solely simulators that are used for surgical skills training were validated for the highest validity level (predictive validity). Twenty-four (37%) simulators that give objective feedback had been validated. Studies that tested more powerful levels of validity (concurrent and predictive validity) were methodologically stronger than studies that tested more elementary levels of validity (face, content, and construct validity). Conclusion Ninety-three point five percent of the commercially available simulators are not known to be tested for validity. Although the importance of (a high level of) validation depends on the difficulty level of skills training and possible consequences when skills are insufficient, it is advisable for medical professionals, trainees, medical educators, and companies who manufacture medical simulators to critically judge the available medical simulators for proper validation. This way adequate, safe, and affordable medical psychomotor skills training can be achieved.

Ergonomic handle for an arthroscopic cutter

From an analysis of the routinely performed meniscectomy procedures, it was concluded that a punch with a side-ways steerable tip would improve the reachability of meniscal tissue. This potentially leads to a safer and more efficient meniscectomy. Furthermore, the current scissors handles of arthroscopic punches are ergonomically not sufficient. An ergonomic handle is designed with one lever that enables opening and closing of the instrument tip, and side-ways steering of the instrument tip. The design of the handle complies with ergonomic guidelines that were found in the literature. A model of the instrument tip was added to the new handle for comparison with conventional handles. Experiments were performed with a knee joint model, using objective and subjective criteria. The results show that the concept of a side-ways steerable punch is promising, since faster task times are achieved without increasing the risk of damaging healthy tissue. The current design of the ergonomic handle incorporates two degrees of freedom in an intuitive way, the handle is more comfortable to hold, and easy to control. The external memory capabilities of the new handle could be improved. Further development of this handle and the addition of a sufficient instrument tip and force transmission are recommended.

FEASIBILITY OF ULTRASOUND IMAGING OF OSTEOCHONDRAL DEFECTS IN THE ANKLE: A CLINICAL PILOT STUDY

Talar osteochondral defects (OCDs) are imaged using magnetic resonance imaging (MRI) or computed tomography (CT). For extensive follow-up, ultrasound might be a fast, non-invasive alternative that images both bone and cartilage. In this study the potential of ultrasound, as compared with CT, in the imaging and grading of OCDs is explored. On the basis of prior CT scans, nine ankles of patients without OCDs and nine ankles of patients with anterocentral OCDs were selected and classified using the Loomer CT classification. A blinded expert skeletal radiologist imaged all ankles with ultrasound and recorded the presence of OCDs. Similarly to CT, ultrasound revealed typical morphologic OCD features, for example, cortex irregularities and loose fragments. Cartilage disruptions, Loomer grades IV (displaced fragment) and V (cyst with fibrous roof), were visible as well. This study encourages further research on the use of ultrasound as a follow-up imaging modality for OCDs located anteriorly or centrally on the talar dome.

Sensitivity and Specificity of Ultrasound in Detecting (Osteo)Chondral Defects: A Cadaveric Study

The long-term prognosis of cartilage lesions evolving into an eroding subchondral bone defect is not known. Longitudinal monitoring using ultrasound could assist in overall understanding. The aim of the work described in this article was to determine the feasibility of using ultrasound to detect small (osteo)chondral defects. On the anterior talar surface of 10 human cadaveric ankles, at most four defects were arthroscopically created: two pure chondral defects 3 and 1.5 mm in diameter and two osteochondral defects 3 and 1.5 mm in diameter. All ankles were examined by two observers, and their ultrasound observations were validated using computed tomography scans and photographs. Overall sensitivity was 96% for observer 1 and 92% for observer 2, and specificity for both observers was 100%. Sixty-eight percent and 79% of defect sizes were within relevant limits of agreement (-0.2 ± 1.0 mm), respectively. Ultrasound imaging has the potential to detect small (osteo)chondral defects located within visible areas.

Experimental approach to study arthroscopic irrigation

The view during arthroscopic operations is kept clear by means of irrigation. The purpose was to determine dominant parameters on irrigation performance from which design considerations were formulated for optimization of joint irrigation. An experimental approach was chosen. The set up consisted of a human joint phantom with normal operative equipment for irrigation. Disturbances of the view were simulated with blue colored ink. With this, an objective and quantitative outcome measure was defined as the time from ink injection till complete clear view (irrigation time). The irrigation times for varying parameters were evaluated: pressure and flow, configuration of in- and outflow portals, location of bleeding, two- versus three-dimensionally shaped joint space, direction and location of inflow, and presence of an instrument. Apart from the level of pressure and flow (F(5,34)=245, p<0.05), the configuration of in- and outflow portals had a dominant significant influence on the irrigation time (F(2,23)=69, p<0.05) achieving a decrease of up to 64% and 77%, respectively. The experimental approach resulted in formulation of design criteria for new sheaths: cross-sectional area as large as possible, and stimulation of a turbulent inflow. The method can be used as a standard testing protocol for new arthroscopic devices and instruments.

Clinically-driven approach to improve arthroscopic techniques.

In this paper, a clinically-driven approach is introduced as the starting point for the improvement of arthroscopic techniques. The approach was divided into two phases. Phase 1 consisted of a combination of observations and discussions that resulted in the definition of clinically-relevant research topics. Phase 2 consisted of an interview which aimed at analysis of the general opinion on arthroscopy, and which assigned a priority ranking to the topics. Six research topics were defined. Based on the information collected, the conclusion is that the surgeons are satisfied with current arthroscopic techniques. A majority gives priority to the optimization of cartilage treatment and to the design of a steerable arthroscopic cutter. A minority gives priority to the expansion of arthroscopic techniques. The two-phase approach was fruitful in terms of establishing clinical problem areas, and of involving surgeons in the technical improvement of arthroscopic techniques.