Haptics is the combination of kinesthetic, tactile, and proprioceptive information. Kinesthetic feedback provides position, force, and movement information and can be measured using a force/torque sensor. Tactile feedback includes the sensation of vibration, shape, and texture. Proprioception provides the sense of position and
movement of body segments [1]. For a complete depiction of haptic interactions between surgical instruments and tissue, kinesthetic, tactile, and proprioception feedback must be acquired [1-3].
During robotics-assisted surgery, the indirect manipulation of tissue through the master– slave configuration of the robotic system prevents realistic interaction forces among the surgeon, the therapeutic instruments, and the tissue [4]. This absence of haptic feedback may be detrimental in dexterous fine movements such as intracorporeal suturing and knot tying, which require accurate control of applied forces and instrument positions [1, 5– 7]. Furthermore, without haptic feedback, insufficient forces might be applied when grasping tissue or sutures, resulting in loose knots [1, 4]. Conversely, excessive forces
may be applied to tissue leading to increased trauma and damage [1, 4]. This is
particularly important in robotics-assisted mitral valve repair, which requires fine motor skill to suture an annuloplasty band to the cardiac tissue surrounding the mitral valve annulus. Without tactile and force information, surgeons must rely on visual cues to estimate the force being applied [1, 8–10]. Advanced surgical skills require not only fine motor skills but also depth perception. Minimizing tissue trauma while performing surgery may ultimately affect surgical performance, operative time, and morbidity. In the currently used minimally invasive surgical robotic system (the da Vinci from Intuitive Surgical Inc.), the master–slave configuration and the absence of haptic feedback prevent the transmission of tool–tissue interaction forces to the surgeon
[11]. Some have argued that the da Vinci’s superior three-dimensional (3D) visualization capabilities compensate for lack of haptic feedback, others assert that visualization alone cannot replace the value of haptic feedback [12].
In fact, we have previously found that despite high-quality binocular images, both the experts and the novices applied significantly more force to the cardiac tissue during 3D robotics-assisted mitral valve annuloplasty than during conventional open mitral valve annuloplasty. This finding suggests that 3D visualization does not fully compensate for the absence of haptic feedback in robotics-assisted cardiac surgery [13]. Furthermore, although a complete depiction of haptic interactions has not been integrated into robotics- assisted surgical systems, other researchers have investigated the potential benefits of the addition of either direct force feedback or visual force feedback into robotics-assisted surgical systems [14–18].
Direct force feedback involves the kinesthetic perception of reflected weight and
Wagner and colleagues found that direct force feedback for a minimally invasive cannulation task using endoscopic visualization reduces applied forces [14]. Another study by Wagner and colleagues examined the effects of direct force feedback on blunt dissection of an artery in a synthetic model using endoscopic visualization [15]. The absence of direct force feedback increased the average force magnitude applied to the tissue by at least fifty percent, increased the peak force magnitude by at least 100%, and increased the number of errors that damage tissue by over a factor of three. Kazi and colleagues also showed that using direct force feedback during minimally invasive catheter insertion into a vessel could lower the magnitude of the force applied to tissue during a procedure [16].
Visual force feedback involves sensory substitution and provides force feedback by using size and/or color to represent the magnitude of forces applied by a surgical instrument [12]. For example, Reiley and colleagues examined the effects of visual force feedback during surgical knot tying using a modified da Vinci robotic system equipped with force- sensing instrument tips [17]. They found no differences in measured performance parameters between robotics-assisted knot ties executed with and without visual force feedback among surgeons with robotics-assisted surgical experience. However, visual force feedback was associated with lower suture breakage rates, peak applied forces, and standard deviations of applied forces among surgeons without robotics-assisted surgery experience. These results suggested that visual force feedback primarily benefits novice robotics-assisted surgeons. Finally, Tholey and colleagues developed an automated laparoscopic grasper with both direct force and visual feedback to help surgeons differentiate tissue stiffness [18]. These investigators found that the addition of both visual and direct force feedback led to better tissue stiffness characterization than either visual or direct force feedback alone.
Despite this evidence for the benefits of direct force or visual force feedback in robotics- assisted and laparoscopic surgery, many robotics-assisted mitral valve repair surgeries are performed in the absence of any haptic feedback with excellent results [20–24].
Furthermore, some have suggested that the addition of additional stimuli during task learning made the process more difficult, as novice trainees may have less attentional resources to attend to force feedback while learning a skill [25].
Therefore, the objective of this study is to determine the effect of both direct force feedback and visual force feedback on the amount of force applied to mitral valve tissue during ex vivo mitral valve annuloplasty using robotics-assisted techniques. In addition, our aim is to determine whether these effects are consistent between novices and experts in robotics-assisted cardiac surgery. We expect that the addition of either direct or visual force feedback will decrease the magnitude of force applied to cardiac tissue during robotics-assisted mitral valve annuloplasty. Furthermore, we expect that these
differences will be more pronounced in novices, as they have less experience using visual cues to estimate the amount of force applied to tissue during robotics-assisted cardiac surgery.