Table 1.

Current status of haptic feedback in CES

Subject	Study objective(s)	Conclusion	Level of evidencea	Literature reference
Instrumentation
Consequences of interposition of endoscopic instruments		Haptic feedback is decreased in conventional endoscopic surgery	3b/4	[4–6] [25, 31–33]
		Due to an interaction force of the instrument tips contacting organs or tissue, a certain amount of haptic feedback remains
Quantification of haptics	Evaluate feedback quality laparoscopic dissectors	Haptic feedback is best felt through:	3b	[32] [26, 36, 37]
		1. Bare hands
		2. Instruments for open surgery
		3. Endoscopic instruments
	Determine ability of novice surgeons to interpret haptic feedback	There is a 8–20× sensitivity loss when using endoscopic instrument instead of bare fingers.
	Characterize laparoscopic gestures	Using the instrument as a lever, theoretically, the force generated from contact with an organ can be fed back to the surgeon 0.2–4.5 times the force generated by organ-instrument interaction
	Analyze strain and working volume of existing endoscopic instruments	The forces applied at the extremity of the instrument by the surgeon during a laparoscopic gesture range from 0.5–1	3b	[38]
		The translated force exerted at the instrument tips range from 0.4–10.5 N
	Characterize laparoscopic gestures and quantitative measurement of interactions between organs and the instrument	The forces of interaction between organs and instrument tips during endoscopic gestures range from 0.1–10 N	3b	[26]
		Frictional forces of endoscopic instruments with the trocar can exceed 3 N
	Investigate the dynamic changes in friction for various trocars at different instrument velocities	The fluctuation in frictional forces, 0.2–2.5 N, depends on the type of trocar used and the movement direction and velocity of endoscopic instruments	3b	[39]
		High variance in interfering forces may worsen an endoscopic surgeon’s performance during tasks requiring utmost precision
	Determine the ability of experienced surgeons to interpret haptic feedback	Interpretation of the texture, shape, and consistency of objects can be performed using endoscopic instruments. In some situations, endoscopic instruments seem to amplify the haptic information available	3b	[37]
	Determine the ability of novice surgeons to interpret haptic feedback	While endoscopic instruments change the information available to the surgeon, interpretation of the texture, shape, and consistency of objects can be performed	3b	[37]
Mechanical efficiency	Determine influences of visual feedback, force feedback, and the experience of the surgeon, both on grasping tissue and on holding tissue	The exerted pinch force on the tissue was not influenced by the mechanical efficiency of the forceps	3b	[25]
	Evaluate the feedback quality of commercially available reusable and disposable laparoscopic dissectors	Enhancing instrumental mechanical efficiency enhances haptic feedback	3b	[32] [34]
	Gaining tactile and kinesthetic information for new user interfaces in MIS
	Developing new technologies to rectify loss of sensory feedback	Optimal mechanical efficiency of forceps depends on specific task being performed.	3b	[40–43]
Vision
Influence of vision on surgical performance	Evaluate the role of force feedback with applications to minimally invasive surgery	Vision and haptic feedback combined improve tissue consistency determination	3b	[5]
	Determination of influences of visual feedback, force feedback, and the experience of the surgeon, both on grasping tissue and on holding tissue	The exerted pinch force on tissue is not influenced by visual feedback alone	3b	[25]
Miscellaneous
Haptic feedback is not essential when performing MIS	Gaining tactile and kinesthetic information for new user interfaces in MIS	Experienced surgeons are able to perform both CES and RAS without complications, without force feedback	3b	[25] [39] [60]
		Force feedback, visual feedback, and laparoscopic experience provided to be less important than initially expected in the particular task of holding tissue
	Determination of influences of visual feedback, force feedback, and the experience of the surgeon, both on grasping tissue and on holding tissue	The optimal mechanical efficiency of laparoscopic forceps depends on the specific tasks performed with the forceps
	To characterize laparoscopic gestures and quantitative measurement of the various interactions between organs and the instrument	Haptic feedback should not be taken into account because it is subject to other forces	3b	[26]
Absence of haptic feedback causes slippage and tissue damage	Determination of influences of visual feedback, force feedback, and the experience of the surgeon, both on grasping tissue and on holding tissue	7% tissue slippage in grasping actions	3b	[37]
		Pinch force necessary to prevent slippage was on average 3 N
	To investigate the effectiveness of grasping and the duration of tissue-clamping using laparoscopic forceps	62% of grasping actions were successful	3b	[45]
		7–10% of clamping actions were repeated actions.
		Tissue slippage occurred in 7–17%
		Video analysis showed that applying the correct amount of force when grasping tissue without force feedback leads to slippage and tissue damage	3b	[40] [44]

All studies were conducted as individual case–control study

^aBased on the guidelines of the Oxford Centre of Evidence-based Medicine Levels of Evidence [17]