Needs analysis for developing a virtual-reality NOTES simulator

Introduction and study aim

Natural orifice translumenal endoscopic surgery (NOTES) is an emerging surgical technique that requires a cautious adoption approach to ensure patient safety. High-fidelity virtual-reality-based simulators allow development of new surgical procedures and tools and train medical personnel without risk to human patients. As part of a project funded by the National Institutes of Health, we are developing the virtual transluminal endoscopic surgery trainer (VTEST?) for this purpose. The objective of this study is to conduct a structured needs analysis to identify the design parameters for such a virtual-reality-based simulator for NOTES.

Methods

A 30-point questionnaire was distributed at the 2011 National Orifice Surgery Consortium for Assessment and Research meeting to obtain responses from experts. Ordinal logistic regression and the Wilcoxon rank-sum test were used for analysis.

Results

A total of 22 NOTES experts participated in the study. Cholecystectomy (CE, 68 %) followed by appendectomy (AE, 63 %) (CE vs AE, p = 0.0521) was selected as the first choice for simulation. Flexible (FL, 47 %) and hybrid (HY, 47 %) approaches were equally favorable compared with rigid (RI, 6 %) with p < 0.001 for both FL versus RI and HY versus RI. The transvaginal approach was preferred 3 to 1 to the transgastric. Most participants preferred two-channel (2C) scopes (65 %) compared with single (1C) or three (3C) or more channels with p < 0.001 for both 2C versus 1C and 2C versus 3C. The importance of force feedback and the utility of a virtual NOTES simulator in training and testing new tools for NOTES were rated very high by the participants.

Conclusion

Our study reinforces the importance of developing a virtual NOTES simulator and clearly presents expert preferences. The results of this analysis will direct our initial development of the VTEST? platform.     

Electromyographic analysis of equinovarus following stroke

The pattern of muscle activity was determined in 40 hemiplegic stroke patients with equinus, equinovarus or varus deformities. Although the exact pattern of muscle activity varied with each patient, the following general conclusions are possible. Premature firing of the triceps surae due to release of primitive locomotor control mechanisms and a hyperactive stretch response during limb loading are important causes of equinus. Prolonged firing of the tibialis anterior during stance and inactivity of the peroneus brevis are the principal factors responsible for varus.     

Electromyographic analysis of shoulder muscle load

The influence of hand tool weight and arm position on shoulder muscle load was studied by electromyography. The investigation was made to facilitate recommendations on work place design. The aim is to reduce the occurrence of occupational shoulder disorders in industry. Nine volunteers held 21 different arm positions with the hand over waist level. In each position, the hand was loaded with 0, 1, and 2 kg. Each load was maintained for 15 s. The myoelectric activity in six shoulder muscles was recorded and analyzed automatically with respect to the amplitude. The results indicate that the degree of upper arm elevation is the most important parameter influencing shoulder muscle load. Short rotator muscles stabilizing the shoulder joint were found to be more hand-load dependent than the deltoid muscle. The ergonomic implications of this study are that work situations should be designed so that the arm can be kept close to the body and the hand load minimized.     

Dynamic analysis of the Harrington system using a spinal simulator

The authors constructed a spinal simulator for the thoracolumbar spine with mechanical properties similar to those of cadaver specimens, and studied the effectiveness of the Harrington system in unstable fractures of the thoracolumbar spine. Distraction and compression rods were applied under various conditions. External bending moment was applied to the model to measure the internal bending moment on the vertebral body and ligaments. Optimal spinal stability was obtained when the distraction system was combined with the compression system with hooks at laminas three levels above and below the fracture.     

Electromyographic analysis of muscles across the elbow joint

An electromyographic (EMG) technique was developed to study simultaneously the eight major elbow muscles in five normal subjects. Recordings of EMG activity in elbow muscles were obtained while the elbow joint was subjected to resisted flexion, extension, abduction, and adduction functions. The results indicate that activity in the major elbow muscles is determined by the size of the resultant flexion and extension moments created about the elbow joint, but not by varus and valgus moments. These results support the hypothesis that determination of muscle force about a joint depends on joint constraint, namely, the degree of freedom, the resultant joint forces and moments due to externally applied load, and also the function of the muscle, i.e., the line of action of the muscle that crosses the joint. The data may be used to further refine the calculation of muscle force distribution across the elbow joint.     

Electromyographic and gait analysis of forty-three patients after rotationplasty

BACKGROUND: Rotationplasty is considered to be a treatment option for patients who have had a primary malignant bone tumor of the distal part of the femur or the proximal part of the tibia. The present study was performed to evaluate the muscle activity, the kinetics (range of motion of the hip and knee joints), and the kinematics (joint moments) after rotationplasty and to determine whether there was an association between these parameters and the functional outcome. METHODS: Forty-three patients who had been managed with rotationplasty for the treatment of a femoral or tibial bone tumor were evaluated clinically and functionally. The mean age (and standard deviation) at the time of follow-up was 24.4 +/- 10.7 years (range, eight to sixty-eight years), the mean age at the time of the procedure was 17.8 +/- 10.2 years (range, seven to sixty-three years), and the mean duration of follow-up was 6.7 +/- 4.9 years (range, 0.7 to eighteen years). Instrumented gait and electromyographic analyses were performed. The qualitative data were compared with the functional outcome, which was determined with the functional evaluation score of the Musculoskeletal Tumor Society. RESULTS: Gait analysis revealed a fairly normal walking pattern with a slight limp and a lateral lean of the trunk over the ipsilateral limb that led to a reduced joint moment in the hip (moment on involved side, 68 percent [compared with a control group]; moment on uninvolved side, 81 percent). The ranges of motion of the hips (uninvolved side, 42.0 +/- 8.2 degrees; involved side, 42.4 +/- 8.0 degrees) and the knees (uninvolved side, 59.7 +/- 5.0 degrees; involved side [former ankle joint], 58.1 +/- 11.6 degrees) were symmetrical even though the knee-motion pattern of the involved limb indicated a slightly reduced extensor mechanism in 51 percent (twenty-two) and a markedly reduced extensor mechanism in 35 percent (fifteen) of the forty-three patients. Electromyography revealed function of the muscles of the involved limb, with comparable amplitudes in the involved and uninvolved limbs. The leg muscles of the involved limb were active in the stance phase (the soleus and the lateral and medial heads of the gastrocnemius) and the swing phase (the peroneus longus and the tibialis anterior) according to their function in relation to the new knee joint. The patients had a good functional result, with a mean score of 23.9 +/- 2.7 of 30 points. With the numbers available for study, we could not show the duration of follow-up to be related to the overall outcome, but the age at the time of the operation was related to the total functional score as well as to gait and walking ability (p < 0.05). CONCLUSIONS: The results of the electromyographic and gait analyses demonstrated good functional restoration of gait following rotationplasty.     

Electromyographic analysis of muscle function after latissimus dorsi tendon transfer

The latissimus dorsi transfer is an established method for irreparable tears of the rotator cuff. The original task of the muscle is to move the arm downward and to rotate it internally. After the transfer, it has to perform the completely new function of elevating the arm. We used surface electromyography to calculate the mean values of the activity pattern in relation to the Constant score in 45 patients. We assessed patients after 6 weeks and at 6, 9, and 19 months. After the operation, most patients showed a typical activity pattern of the latissimus dorsi on electromyography, which improved in the course of the study. We also found a strong correlation between the activity pattern on electromyography and the Constant score in different areas. We conclude that the functional improvement is due to an active muscle contraction as shown on electromyography and is not just an interposition or tenodesis effect.     

Electromyographic analysis of the thumb: a study of isometric forces in pinch and grasp

An electromyographic study of thumb muscles was performed on eight subjects by means of integrated polyelectromyography and simultaneous recordings of isometric flexion-extension, abduction-adduction, and prehensile pinch and grasp of the thumb. The integrated electromyographic signal proved to be an excellent index of thumb muscle activity, with a linear relationship found at low to middle levels of muscle strength. To facilitate understanding of thumb function, thumb muscles can be classified as primary or secondary on the basis of electrical potential activity. In isometric flexion, the flexor pollicis longus (FPL) was primary, whereas in extension, the extensor pollicis longus (EPL) and abductor pollicis longus were primary. In adduction, the adductor pollicis and EPL were primary and the FPL was secondary. In abduction, the abductor pollicis brevis and opponens pollicis were primary. The adductor pollicis, and FPL were nearly equal during pinch and grasp, with significant electrical activity increasing with greater force requirements. The first dorsal interosseous and EPL contributed secondarily in both pinch and grasp. When surgeons consider tendon transfers for nonfunctioning thumb muscles, the primary muscles should be replaced first to best restore pinch and grasp strength.     

Electromyographic analysis of quadriceps fatigue after anterior cruciate ligament reconstruction

STUDY DESIGN: Prospective, observational study. OBJECTIVES: To document changes in surface electromyographic activity during sustained maximum quadriceps contractions in patients before and 5 weeks after anterior cruciate ligament (ACL) reconstruction. BACKGROUND: Quadriceps weakness after injury and reconstruction of the ACL is well documented. The effect of weakness on muscle fatigue, however, is not well understood. METHODS AND MEASURES: Electromyographic signals were recorded from the vastus lateralis, vastus medialis, and rectus femoris muscles during 30-second maximum isometric contractions at 30 degrees, in 42 patients preoperatively and 5 weeks postoperatively. Signal amplitude was quantified by integrating the rectified signal (iEMG) for the initial and final 5 seconds and comparing the involved and uninvolved sides. Median frequency (MF) was computed from 4,096 point fast Fourier Transforms performed at the beginning and end of the 30-second contractions. RESULTS: Patients had moderate preoperative quadriceps weakness (16% deficit) and gross postoperative weakness (41% deficit). Weakness was associated with deficits in both MF and iEMG (r = 0.69-0.67). During the preoperative fatigue test, torque declined similarly on the involved and uninvolved sides (significant fatigue effect). During the postoperative fatigue tests, however, torque increased on the involved side and declined on the uninvolved side (significant side by fatigue interaction). For the initial 5 seconds, MF was lower on the involved than the uninvolved side but subsequently showed a smaller decline over 30 seconds preoperatively and postoperatively (significant side by fatigue interactions). IEMG was lower on the involved side preoperatively and postoperatively. During the fatigue tests, iEMG increased similarly in the involved and uninvolved sides both preoperatively and postoperatively. CONCLUSION: Quadriceps endurance exercises are not indicated after ACL reconstruction. Quadriceps weakness after ACL reconstruction was associated with fatigue resistance. Lower initial MF and smaller decline in MF during sustained contraction is consistent with fast-twitch fiber atrophy and explains fatigue resistance.     

Electromyographic analysis of hip abductor exercises performed by a sample of total hip arthroplasty patients

Weakness of the hip abductors after total hip arthroplasty may result in pain and/or functional limitation. Non-weight-bearing (NWB) exercises are often performed to target the hip abductors; however, muscle activation of NWB exercises has not been compared to weight-bearing (WB) exercises. Our purpose was to evaluate gluteus medius activation during 2 WB and 2 NWB hip abductor strengthening exercises. Fifteen patients at least 6 weeks post unilateral total hip arthroplasty volunteered for the study. Electromyographic amplitude for each exercise was normalized to each patient's maximal voluntary isometric contraction. There were no significant differences in gluteus medius electromyographic amplitudes between the 4 exercises (P = .15). Based on our results, NWB exercises provided no clear benefit in terms of gluteus medius activation when compared to potentially more functional WB exercises in the early postoperative period.     

Kinematic analysis of mobile-bearing total knee arthroplasty using a 6-DOF knee simulator

Background  The purpose of this study was to investigate the kinematics of the polyethylene insert in two designs of mobilebearing total knee arthroplasty, using a six-degrees-of-freedom knee simulator. It was consequently not clear whether the motion of the polyethylene bearing in mobile-bearing total knee arthroplasty could be demonstrated during the gait cycle or more rapid movement. Methods  A mobile-bearing knee (Zimmer) and a low contact stress rotating-platform design (Depuy) were mounted on a simulator which was regulated by the kinematic data of gait. The simulating test was conducted under a static condition as well as under dynamic conditions of 0.5 Hz and 1.0 Hz. We recorded the motions of the implants with two charge-coupled device (CCD) cameras, and the positions of the insert were calculated. Results  In spite of the same relative motion between the femoral component and the tibial tray, the polyethylene insert showed unique relative motion according to the given condition. The motion of the insert during the dynamic conditions was considerably decreased in comparison to the static condition in both mobile-bearing designs. In addition, the insert showed a smaller amplitude and frequency of rotations under increasing speed in the low contact stress rotating-platform design. The low contact stress rotating-platform design showed a larger amplitude and frequency of rotations than the mobilebearing knee. Conclusions  Despite the mobility of the insert in the mobilebearing total knee arthroplasty, the motion of the insert was decreased during dynamic conditions because of the disruption of full contact between the femoral component and the polyethylene insert. Differences in the rotation between the mobile-bearing knee and the low contact stress rotatingplatform design were due to the fixed axis of the internalexternal rotation in the low contact stress rotating-platform design. The theoretical advantages for the mobile-bearing design over the fixed-bearing design were not demonstrated in this study.