Calling attention to the use of haptic feedback in training devices used in other domains, Adrian Hendrickse, B.M., FRCA and Karl Reinig, Ph.D., assert that for effective training on appropriate procedures, medical simulators should include haptic functioning. 

For hundreds of years, medical professionals were trained the same way – see one, do one, and then soon thereafter, do more, independently. Cadavers offered some ability to practice, but a doctor’s skills were largely honed on live patients – initially under supervision, and then in live surgical situations. The few simulators available were mechanical, and only offered crude approximations for skills training.

Today’s training methods provide the opportunity for doctors to practice until proficient, using a new generation of surgical simulators. In today’s environment, where initiatives to improve patient outcomes predominate many medical subspecialties have embraced technology as a better and safer way.

Students are looking for new ways to learn. Most clinicians involved in training learners – seek different ways of  fostering learning, for two reasons: students respond to different learning styles and learning that's fun or experiential seems to work best. Indeed the game-like factor cannot be overlooked.  A generational change led to today’s students arriving at medical school with a natural sophisticated ability to play screen-based games and manipulate 3-D objects.

Today medical simulators vary from low to high end in both cost and fidelity from;

  • fake tissue on which to practice suturing
  • simple 3-D textbooks that visualize the learning experience
  • Virtual Reality (VR) trainers akin to video games teaching small core skills but without haptics to
  • VR simulators with kinesthetic or haptic feedback for discrete procedural training and eventually for certification on various surgical specialties.
Surgical Theater's Surgery Rehearsal Platform (SRP) uses haptic devices and patients' own CT and MRI images to enable surgeons to practice and warm-up on the patient's unique anatomical variations in advance. Image Credit: Surgical Theater, LLC.
Surgical Theater's Surgery Rehearsal Platform (SRP) uses haptic devices and patients' own CT and MRI images to enable surgeons to practice and warm-up on the patient's unique anatomical variations in advance. Image Credit: Surgical Theater, LLC. 

Feeling, as well as Seeing: Research Update

The question of whether haptic feedback in simulators is required has interested researchers across various domains.  Often, seeing anatomy in 3-D space and in readily manipulated ways is only part of achieving proficiency and competency at a quantifiable and clinical level. This is particularly true when learning a blind procedure, or one where the unseen and unobservable anatomy is key to successful performance and proficiency.

The authors assert that for effective training on appropriate procedures, simulators should include haptic functioning. The literature reflects that many colleagues across other medical specialties agree, including M. Zhou, et al in a 2012 study in laparoscopic surgical skill acquisition, S. Liang et al. in a 2009 study in ophthalmology, and A.F. Abate et al. in a 2010 study in obstetrics.  It’s only logical that to achieve finger memory and/or dexterous manual proficiency with the sizes and kinds of instruments used today, we must practice so that our senses of touch, sight and hearing are activated.

The oft-presented argument for haptics is its use in other training domains: aviation, space exploration, military and the nuclear industry.  Pilots don't simulate attributes of flight without it feeling right in their hands.  For instance, the controls stiffen the angle of the flight deck changes. These simulators are expensive, and in aviation no one complains; it “feels right” and that is what matters.  Furthermore, instances such as the “Miracle on the Hudson” where a pilot with extensive simulator experience could perform the near miraculous, smooth landing intuitively reaffirm the role of ultra-realistic simulation as a training vehicle. Quantitatively proving where and when haptics make a difference, however, becomes trickier.

In a 2011 literature review of simulation and quality improvement in anesthesiology, C.S. Park summarized that simulation has a proven relationship to improving the effectiveness of education (T1 training), and to improve how skills are transferred to clinical performance (T2 training).   Simulation’s effect on clinical outcomes – T3 training – was evidenced in a more limited extent, particularly in elucidating latent conditions, for which simulation interventions later can be designed.  Tasks that require spatial awareness may benefit from the experience of force feedback, but are probably not as great a fit for haptics as, say, the need to develop tissue feel.

In the domain of anesthesia, when learning to perform a femoral block, it’s actually the identification of fascial boundaries, -- which one cannot see unless using ultrasound techniques,  that helps the trainee find the right location. Palpation over the femoral artery helps them to predict the location of structures within the inguinal region and hence the location of needle insertion but the femoral nerve will only be found by using a mixture of nerve stimulation and tissue feel. Kulcśar, et al. in 2011 characterized eight tactile elements associated with successful performance of spinal anesthesia, from touching skin and bone, to the “pop” sensations of skin and dura mater, to the sensations associated with advancement of spinal needle through three different tissue types. The study’s focus was to determine if haptically enabled simulation could distinguish between novices and experts, and thus if haptically enabled simulators represent a viable means to certify competency in spinal anesthesia.  It did, however, with considerable inter-rater variation when experts were presented with the same haptic rendering on more than one occasion for bone surfaces, skin pops, dura pops and subcutaneous tissue sensations. This finding suggests that it is indeed possible for simulators to “feel real”. Experts agreed that the structures they were feeling virtually, felt real and that there was a wide range of real.

The Kulcśar et al. study discussed the role of explicit knowledge – learning that is formal and easily specified – vs. tacit knowledge – learning that is less easily defined and measured.  Tacit knowledge is difficult to transfer to trainees in a clinical setting under traditional apprenticeship models, and is primarily acquired through experience – exactly the kind of knowledge that simulators seek to provide.

Simulators may be vital in providing experience with anatomic variation – something a surgical resident only really begins to appreciate with experience. ffering a simulator experience that feels real over a variety of situations greatly assists in this context.  Ideally the simulator can then vary parameters to make distances and feedback slightly different but still real to provide a wealth of experience.

Haptically-Enabled Simulation – Best-Fit Scenarios

The above studies and our own sentiment bear out the belief that there are procedures where haptics provide a clear benefit to the simulation experience, so that haptically enabling the simulation is a must.

  • Bone/Tissue distortion and feel.
The Ohio Supercomputer Center (OSC), a publicly-funded research partner to Ohio universities and industries, has won national recognition for its Virtual Temporal Bone Project, which utilizes a Phantom® haptic device (made by Geomagic, Morrisville NC). Developed in partnership with Nationwide Children’s Hospital and The Ohio State University Department of Otolaryngology, OSC’s simulator presents a true-to-life experience encountered in ear surgery.

The temporal bone contains the structures for hearing and balance, and the simulator allows future surgeons to practice delicate surgical drilling techniques on a computer-based teaching system instead of cadavers or as apprentices in operating rooms.

The use of haptics in OSC’s simulator allows surgeons to “feel” the surgery they are performing, as well as see and hear it.  The haptic device and accompanying software employ force-feedback technology to literally push back on the trainee’s hand as they look through a 3-D stereo view that replicates what a surgeon would see through a microscope during surgery. Drilling sounds are then modulated based upon the pressures and area of bone being removed. In this context, haptics enhances the realism and hence the teaching value of the simulator

OSC’s temporal bone simulator is presently being used at 10 sites around the US and has even assisted in the training of surgical residents in Nicaragua, where access to cadaveric temporal bone samples is extremely limited. The group is currently conducting a multi-institutional study to define objective assessments for integration into an automated assessment tool for resident evaluations. Study participants are Duke University, Stanford University, University of California Irvine, University of Mississippi, University of Iowa, University of Cincinnati, Baylor College of Medicine, Albert Einstein College of Medicine, University of Texas, Southwestern, Henry Ford Medical Center and The Ohio State University.

  1. Blind procedures.
Touch of Life Technologies (ToLTech), in collaboration with the University of Colorado Center for Human Simulation, has developed a virtual environment to practice multiple medical procedures. The Common Platform Medical Skills Trainer (CPMST)[1]collocates 3-D stereo graphics with high-fidelity haptic devices to create a totally immersive bi-manual environment in which to train and prove proficiency. Initial applications include diagnosis and treatment of compartment syndrome, regional anesthesia, joint injection, and ophthalmic procedures. An associated Mentor program eavesdrops on the state variables of the simulations to guide, critique and score the users, providing an autonomous experience that replicates the apprenticeship method, but on demand and without risk.

In the CPMST’s femoral nerve block application, the trainee initially experiences blind needle advancement, utilizing palpation of bony landmarks, pulse, and the feel of various structures as the needle advances, to determine the proximity of the needle tip to the femoral nerve. This training would simply not work without the simulator’s ability to display the associated haptic forces. Follow on lessons include stimulation through the needle and ultrasound guidance as clinically useful methods to confirm the needle path.

3) Surgical rehearsal. Simulators can also be made into surgical rehearsal platforms where the marriage of patient CT and MRI files allow the ultimate in personalized rehearsal. Traditionally clinicians would look at CT scans before an operation and have to translate the flat, black-and-white image into a realistic picture in their heads. Working this way can add time during a critical operation, when of course the goal is to reduce time in surgery without sacrificing accuracy.

Surgical Theater’s Surgery Rehearsal Platform (SRP) is the first simulator on the market to use patients’ own CT and MRI images, enabling surgeons to practice and warm-up in advance on the patient’s unique anatomical variations. The SRP reconstructs CT and MRI images/scans and transforms those images into dynamic, interactive 3-D models with life-like tissue reaction and accurate modeling of surgery tools that allows surgeons to plan and rehearse a specific patient’s case before entering the operating room.

The initial offering has been developed for brain aneurysm surgery, one of the most technically complex procedures a neurosurgeon performs. A cerebral aneurysm is a ballooning of a blood vessel in the brain that is often treated by microsurgical techniques involving the placement of a small titanium clip across the neck of the aneurysm. Development of complicated brain surgeries that involve a complex approach in delicate areas of the brain such as pituitary and meningioma tumors is underway.

By holding a Phantom haptic stylus designed to operate as if he/she was holding a surgical instrument, the surgeon can “feel” the virtual tissues, note their reaction to different shaped surgical clips, feel the results of more or less pressure on the aneurysm, and practice different angles of insertion. Providing a realistic environment, allows the surgeon to make critical decisions in advance, on an exact replica of the patient, in a “risk free” virtual rehearsal environment, hence, to “pre-live the future” of a specific patient case.

The Common Platform Medical Skills Trainer, from Touch of Life Technologies. Image Credit: ToLTech.
The Common Platform Medical Skills Trainer, from Touch of Life Technologies. Image Credit: ToLTech.

Cost – The Bottom Line, or is it?

Another factor considered by both simulation purchaser and creators, is cost – as assessed by Thompson et al in 2011 specifically for laparoscopic cholecystectomy. Virtual reality simulators are more than just a PC and off-the-shelf software. Haptically enabling the training means the simulator system will require the addition of a haptic device and associated software/ programming development costs. The system price tag will reflect these, although with affordable PCs and off the shelf components haptically-enabled simulators exist on the market today starting at $15,000. However when the simulator is itself a platform for delivering more than one kind of training, to be used by more than one medical school or hospital department, the purchasing decision is easier to cost-justify. Beyond cost, there are “If/Then” scenarios that may extend far beyond cost-benefit analyses in the decision as to whether a haptically-enabled training experience leads to better training for specific procedures. As CMS-driven penalties for being the bottom quartile of hospital readmissions loom – and as penalties when adverse reactions are deemed avoidable also loom – the cost of a simulator may be minor in the light of the risk of reputation or financial damage arising from perceived gaps in training.


As resident training hours are limited while procedures become more complex – simulation fills a vital role in medical training. When the right tasks are haptically-enabled, simulation is a powerful adjunct to both training and certification.  

About the Authors

Adrian Hendrickse, BM, FRCA is associate professor of anesthesiology at University of Colorado Medical School and practices at the University of Colorado Hospital.  He also is the director of the department of Anesthesiology’s simulation education program and is a consultant with the School of Medicine’s Center for Human Simulation.

Karl Reinig, Ph.D. is assistant professor of Cell and Developmental Biology at the University of Colorado School of Medicine, and co-founder and director of engineering at Touch of Life Technologies. He also has over 20 years of experience creating realistic 3-D display of complex scenes to lead the development of virtual environments in which to gain, maintain, and prove medical skills.

[1] Funding for the CPMST has come from the Telemedicine and advanced Technology Research Center of the US Army Medical Research and Materiel Command.