A single port surgical robot system with novel elbow joint mechanism for high force transmission

BACKGROUND

Despite its evident clinical benefits, single-incision laparoscopic surgery (SILS) imposes inherent limitations of collision between external arms and inadequate triangulation because multiple instruments are inserted through a single port at the same time.

METHODS

A robot platform appropriate for SILS was developed wherein an elbowed instrument can be equipped to easily create surgical triangulation without the interference of robot arms. A novel joint mechanism for a surgical instrument actuated by a rigid link was designed for high torque transmission capability.

RESULTS

The feasibility and effectiveness of the robot was checked through three kinds of preliminary tests: payload, block transfer, and ex vivo test. Measurements showed that the proposed robot has a payload capability >15 N with 7 mm diameter.

CONCLUSIONS

The proposed robot is effective and appropriate for SILS, overcoming inadequate triangulation and improving workspace and traction force capability.

Modeling and test of a kinaesthetic actuator based on MR fluid for haptic applications

Haptic display units have been widely used for conveying button sensations to users, primarily employing vibrotactile actuators. However, the human feeling for pressing buttons mainly relies on kinaesthetic sensations (rather than vibrotactile sensations), and little studies exist on small-scale kinaesthetic haptic units. Thus, the primary goals of this paper are to design a miniature kinaesthetic actuator based on Magneto-Rheological (MR) fluid that can convey various button-clicking sensations and to experimentally evaluate its haptic performance. The design focuses of the proposed actuator were to produce sufficiently large actuation forces (resistive forces) for human users in a given size constraint and to offer a wide range of actuation forces for conveying vivid haptic sensations to users. To this end, this study first performed a series of parametric studies using mathematical force models for multiple operating modes of MR fluid in conjunction with finite element electromagnetism analysis. After selecting design parameters based on parametric studies, a prototype actuator was constructed, and its performance was evaluated using a dynamic mechanical analyzer. It measured the actuator's resistive force with a varying stroke (pressed depth) up to 1 mm and a varying input current from 0 A to 200 mA. The results show that the proposed actuator creates a wide range of resistive forces from around 2 N (off-state) to over 9.5 N at 200 mA. In order to assess the prototype's performance in the terms of the haptic application prospective, a maximum force rate was calculated to determine just noticeable difference in force changes for the 1 mm stoke of the actuator. The results show that the force rate is sufficient to mimic various levels of button sensations, indicating that the proposed kinaesthetic actuator can offer a wide range of resistive force changes that can be conveyed to human operators.

Stability and Performance of Haptic Interfaces with Active/Passive Actuators—Theory and Experiments

This paper addresses both theoretical and experimental studies of the stability and performance of haptic interfaces containing active/passive actuators. Three different realizations of haptic interfaces are introduced to investigate their stability and performance: an active system equipped with a motor; a passive system equipped with a brake; and a hybrid system equipped with both brake and motor. The first objective is to demonstrate that a hybrid system is superior in its stability and performance to an active system via passivity theorem and Z-width. The second objective of this paper is to show that the conditions for the asymptotic stability of haptic interfaces during the static friction display are investigated via the absolute stability theory. Theoretical and experimental results are compared. An alternative haptic interface is proposed that provides its highly stable haptic interaction with high performance.

Surgical robot system for single-port surgery with novel joint mechanism

Single-port surgery is a new surgical method performed by inserting several surgical tools and a laparoscope through an umbilical incision. Compared with conventional laparoscopic surgery, the smaller incision in this procedure produces a lower amount of trauma, which leads to shorter hospitalization. However, with the current laparoscopic tools and surgical robots, the surgeon must overcome several difficulties, such as a limited range of motion and collisions between the surgical instruments and the laparoscope. This paper proposes a new surgical robot system for single-port surgery that uses a novel joint mechanism. The proposed joint mechanism is suitable for surgical instruments with multiple degrees of freedom (DOF). Thus, it can prevent hysteresis of the joint and achieve more accurate motion with a large force. A 6-DOF surgical instrument with this joint mechanism can avoid collisions between surgical tools or arms and approach the surgical target more easily than a conventional straight surgical tool. The external arm with 2-DOF passive joints can extend the workspace of the system during surgery. Preliminary tests and validations were performed with a prototype of the system.

Morbidity and mortality of the Hartmann procedure for diverticular disease over 18 years in a single institution

AIM

Hartmann's procedure for perforated diverticulitis is associated with substantial morbidity and mortality. This study analyses factors associated with morbidity/mortality and possible changes over time.

METHOD

Patients treated by urgent Hartmann's procedure for perforated diverticulitis between 1992 and 2010 were studied, and information was collected on age, sex, perioperative details, 30-day morbidity and mortality recorded in an institutional review board approved database supplemented by chart review. Patients were divided into four groups based on the year of surgery. Univariate and multivariate logistic regression analysis was performed to identify risk factors associated with morbidity and mortality.

RESULTS

In all, 199 patients (51% female, mean age 65 years, mean body mass index 28 kg/m(2)) were identified. The American Society of Anesthesiologists (ASA) score was 4 in 30% of patients and Hinchey Stage IV in 16%. The mean length of stay was 12.5 ± 10 days. Mortality was 15% and did not change significantly over time. Overall morbidity was 52% and significantly increased over time on univariate analysis (P = 0.007) but not on multivariate analysis (P = 0.11). Independent predictors of morbidity on multivariate analysis were Hinchey IV (P < 0.001) and hypoproteinaemia (P = 0.001). Independent predictors for mortality were ASA > 3 (P = 0.01), abnormal creatinine (P = 0.007), steroid use (P = 0.007), Hinchey IV (P = 0.032), low albumin (P < 0.001) and low body mass index (P = 0.001).

CONCLUSION

Mortality after Hartmann's procedure for perforated diverticulitis has not decreased during the last 18 years. Morbidity has actually increased over time although this is related to increased disease severity and comorbidity. Future efforts should focus on the identification of patient subgroups benefiting from earlier elective surgery and alternative surgical approaches when perforated diverticulitis does occur.

Effect of frequency difference on sensitivity of beats perception

Two vibrations with slightly different frequencies induce the beats phenomenon. In tactile perception, when two pins of different frequencies stimulate the fingertips, an individual perceives a beats caused by a summation stimulus of the two vibrations. The present study demonstrates experimentally that humans can perceive another vibration based on the beats phenomenon when two tactile stimuli with slightly different frequencies are stimulated on the finger pad with a small contactor in different locations at the same time. Moreover, we examined the amplitude of the detection threshold to be able to perceive beats phenomenon on the index finger with 5 carrier frequency (63.1, 100, 158.5, 251.2, and 398.1 Hz) and 4 beats frequency (2.5, 3.98, 6.31, and 10 Hz) when two stimuli 1 mm distance apart are vibrated at a slightly different frequency. From the experiments, it is concluded that the amplitude threshold to be able to perceive beats decreases as the standard frequency increases under 398 Hz. Furthermore, from comparing the absolute detection threshold and beats detection threshold, as the carrier frequency increases, the required amplitude at two pins for the detection of beats decreases compared to absolute vibration.

An anatomic study on the junctura tendinum in the 4th intermetacarpal space and its clinical implication

We report results of anatomic study in the fourth intermetacarpal space, focusing on the pattern of junctura tendinum and variations of extensor tendons of the little finger with its clinical implication on snapping of the little finger. Fifty unpaired cadaveric hands were dissected from the wrist to the middle phalanx of the ring and little fingers. The type of junctura tendinum was judged based on Von Schroder's classification and the relationship with EDC were recorded. EDC to the little finger and EDM were dissected and the numbers were recorded. Forty six hands (92%) exhibited a junctura tendinum in the fourth intermetacarpal space and it was Type III in 42 hands (84%). The EDC-little finger was absent in 76% (38 of 50 hands). When present, EDC-little finger originated most commonly as single thin tendon. The absence of an EDC-little finger was associated with increased incidence of Type III junctura tendinum (37 of 38 hands). An EDM was present in all 50 hands running from the fifth dorsal compartment. Based on these clinical and anatomic studies, we considered that the snapping of the little finger is more likely subluxation of junctura tendinum rather than subluxation/dislocation of EDC of the little finger.

Evolutionary programming-based univector field navigation method for past mobile robots

Most of navigation techniques with obstacle avoidance do not consider the robot orientation at the target position. These techniques deal with the robot position only and are independent of its orientation and velocity. To solve these problems this paper proposes a novel univector field method for fast mobile robot navigation which introduces a normalized two dimensional vector field. The method provides fast moving robots with the desired posture at the target position and obstacle avoidance. To obtain the sub-optimal vector field, a function approximator is used and trained by evolutionary programming. Two kinds of vector fields are trained, one for the final posture acquisition and the other for obstacle avoidance. Computer simulations and real experiments are carried out for a fast moving mobile robot to demonstrate the effectiveness of the proposed scheme.