Perceived realism of haptic rendering methods for bimanual high force tasks: original and replication study.

Realistic haptic feedback is a key for virtual reality applications in order to transition from solely procedural training to motor-skill training. Currently, haptic feedback is mostly used in low-force medical procedures in dentistry, laparoscopy, arthroscopy and alike. However, joint replacement procedures at hip, knee or shoulder, require the simulation of high-forces in order to enable motor-skill training. In this work a prototype of a haptic device capable of delivering double the force (35 N to 70 N) of state-of-the-art devices is used to examine the four most common haptic rendering methods (penalty-, impulse-, constraint-, rigid body-based haptic rendering) in three bimanual tasks (contact, rotation, uniaxial transition with increasing forces from 30 to 60 N) regarding their capabilities to provide a realistic haptic feedback. In order to provide baseline data, a worst-case scenario of a steel/steel interaction was chosen. The participants needed to compare a real steel/steel interaction with a simulated one. In order to substantiate our results, we replicated the study using the same study protocol and experimental setup at another laboratory. The results of the original study and the replication study deliver almost identical results. We found that certain investigated haptic rendering method are likely able to deliver a realistic sensation for bone-cartilage/steel contact but not for steel/steel contact. Whilst no clear best haptic rendering method emerged, penalty-based haptic rendering performed worst. For simulating high force bimanual tasks, we recommend a mixed implementation approach of using impulse-based haptic rendering for simulating contacts and combine it with constraint or rigid body-based haptic rendering for rotational and translational movements.

[Presentation and evaluation of the haptic-visual ear surgery training system "HaptiVisT"]. / Vorstellung und Evaluation des haptisch-visuellen, ohrchirurgischen Trainingssystems "HaptiVisT".

BACKGROUND: Operations on the temporal bone are a special challenge for ENT surgeons. The aim of the BMBF-funded project was to develop a realistic training system for ear operations in the form of a "serious game". METHODS: The presented prototype of the HaptiVisT system functions as a training system for ear surgeries with visual feedback through a glasses-free 3D monitor and feedback by means of a haptic arm simulating the drill. A variety of training options is guaranteed by three available surgical procedures (antrotomy, mastoidectomy, posterior tympanotomy). A weighted point system enables the measurability of the training success. Following the technical development of the prototype, a prospective evaluation was carried out by eight ENT physicians and four students regarding "learning content" and "user experience". A standardized questionnaire was used (ordinal scale: 1=very good to 5=very bad). RESULTS: Regarding the learning content, the aspects "strengthening anatomy (mean=1.58)", "training hand-eye coordination (1.67)", "transferability into practice (1.83)", "usefulness for practice (1.33)" yielded good to very good scores. "User experience" also showed good results for the aspects "realism (2.29)", "interaction of haptics and optics (2.33)" and "immersion in the training system (1.89)". The "motivation factor" was very high for all test subjects (1.2). CONCLUSIONS: The training system for ear surgeries "HaptiVisT" offers the possibility of immersive training. Integration into the daily clinical routine and in particular into the medical training to become an ENT specialist therefore seems to make sense.

Force-feedback assisted and virtual fixtures based K-wire drilling simulation.

One common method to fix fractures of the human hand after an accident is an osteosynthesis with Kirschner wires (K-wires) to stabilize the bone fragments. The insertion of K-wires is a delicate minimally invasive surgery, because surgeons operate almost without a sight. Since realistic training methods are time consuming, costly and insufficient, a virtual-reality (VR) based training system for the placement of K-wires was developed. As part of this, the current work deals with the real-time bone drilling simulation using a haptic force-feedback device. To simulate the drilling, we introduce a virtual fixture based force-feedback drilling approach. By decomposition of the drilling task into individual phases, each phase can be handled individually to perfectly control the drilling procedure. We report about the related finite state machine (FSM), describe the haptic feedback of each state and explain, how to avoid jerking of the haptic force-feedback during state transition. The usage of the virtual fixture approach results in a good haptic performance and a stable drilling behavior. This was confirmed by 26 expert surgeons, who evaluated the virtual drilling on the simulator and rated it as very realistic. To make the system even more convincing, we determined real drilling feed rates through experimental pig bone drilling and transferred them to our system. Due to a constant simulation thread we can guarantee a precise drilling motion. Virtual fixtures based force-feedback calculation is able to simulate force-feedback assisted bone drilling with high quality and, thus, will have a great potential in developing medical applications.