Christopher J. Martin

Virtual reality simulators: Current status in acquisition and assessment of surgical skills

Medical technology is currently evolving so rapidly that its impact cannot be analysed. Robotics and telesurgery loom on the horizon, and the technology used to drive these advances has serendipitous side‐effects for the education and training arena. The graphical and haptic interfaces used to provide remote feedback to the operator – by passing control to a computer – may be used to generate simulations of the operative environment that are useful for training candidates in surgical procedures. One additional advantage is that the metrics calculated inherently in the controlling software in order to run the simulation may be used to provide performance feedback to individual trainees and mentors. New interfaces will be required to undergo evaluation of the simulation fidelity before being deemed acceptable. The potential benefits fall into one of two general categories: those benefits related to skill acquisition, and those related to skill assessment. The educational value of the simulation will require assessment, and comparison to currently available methods of training in any given procedure. It is also necessary to determine – by repeated trials – whether a given simulation actually measures the performance parameters it purports to measure. This trains the spotlight on what constitutes good surgical skill, and how it is to be objectively measured. Early results suggest that virtual reality simulators have an important role to play in this aspect of surgical training.

Resistance forces acting on suture needles

Understanding the resistance forces encountered by a suture needle during tissue penetration is important for the development of robotic surgical devices and virtual reality surgical simulators. Tensile forces applied to skin and tendon during suturing were measured. Fresh sheep achilles tendons were tensioned with a static load 4.9 N, 9.8 N or 19.6 N and sheepskin with 0.98 N, 2.9 N or 4.9 N static load. A straight 2/0 cutting suture needle in series with a load cell on a materials testing machine penetrated the tissue at 90 degrees with a velocity of 1, 5 or 10mm/s for each tissue tension (n=5). Continuous load versus displacement data was obtained and penetration load and stiffness were noted. The load versus displacement curve for skin during needle penetration demonstrated two characteristic peaks, corresponding to initial penetration and emergence of needle from the undersurface of the tissue. Increasing the tension within the tissue (skin and tendon) increased the amount of force required to penetrate the tissue with a suture needle (p<0.05). Needle displacement rate did not affect the resistance to needle penetration (p<0.05). This study provides a simple model for measuring force-feedback during needle penetration of soft tissues and is a good starting point for future studies of the penetration resistance properties of human tissues.

Esophageal histology does not provide additional useful information over clinical assessment in identifying reflux patients presenting for esophagogastroduodenoscopy.

We prospectively evaluated the value of histology in identifying gastroesophageal reflux disease (GERD) in consecutive patients enrolled for upper endoscopy. GERD was defined as heartburn occurring at least weekly. Macroscopic esophagitis was graded and an esophageal biopsy was taken 2 cm above the gastroesophageal junction. Histological esophagitis was identified by: (1) basal cell hyperplasia >15%, (2) increased papillary length >66%, and (3) infiltration by leukocytes/eosinophils. The sensitivity, specificity, and positive and negative predictive value of histological esophagitis in patients with and without typical reflux symptoms, with and without endoscopic changes, or both were evaluated. Of 178 patients, reflux symptoms were present in 59% (N = 105) and esophageal erosions in 19% (N = 34); 75 patients had reflux symptoms but no erosions. While the specificity of histology was adequate (78%), it was insensitive (30%). The positive and negative predictive values were 67% and 44%, respectively. No single individual parameter was better than any other. Thus, histology appears to be of no additional value in identifying GERD.

Quality of life following laparoscopic anterior 90 degrees versus Nissen fundoplication: Results from a multicenter randomized trial.

The short-term clinical outcomes from a multicenter prospective randomized trial of laparoscopic Nissen versus anterior 90° partial fundoplication have been reported previously. These demonstrated a high level of satisfaction with the overall outcome following anterior 90° fundoplication. However, the results of postoperative objective tests and specific clinical symptoms are not always consistent with an individual patient’s functional status and general well being following surgery, and quality of life (QOL) is also an important outcome to consider following surgery for reflux. Hence, QOL information was collected in this trial to investigate the hypothesis: improvements in QOL following laparoscopic antireflux surgery are greater after anterior 90° partial fundoplication than after Nissen fundoplication. Patients undergoing a laparoscopic fundoplication for gastro-esophageal reflux at one of nine university teaching hospitals in six major cities in Australia and New Zealand were randomized to undergo either laparoscopic Nissen or anterior 90° partial fundoplication. Quality of life before and after surgery was assessed using validated questionnaires – the Short Formxa036 general health questionnaire (SF36) and an Illness Behavior Questionnaire (IBQ). Patients were asked to complete these questionnaires preoperatively and at 3, 6, 12 and 24 months postoperatively. One hundred and twelve patients were randomized to undergo a Nissen fundoplication (52) or a 90° anterior fundoplication (60). Patients who underwent anterior fundoplication reported significant improvements in eight of the nine SF36 scales compared to four of the nine following a Nissen fundoplication. The majority of these improvements occurred early in the postoperative period. With respect to the illness behavior data, there were no significant differences between the two procedures. Both groups had a significant improvement in disease conviction scores at all time points compared to their preoperative scores. Patients undergoing laparoscopic anterior 90° partial fundoplication reported more QOL improvements in the early postoperative period than patients undergoing a Nissen fundoplication. However, the QOL outcome for both procedures was similar at later follow-up.

Pattern of management of common bile duct stones in the laparoscopic era: A NSW survey

Background: The management of common bile duct (CBD) stones in the laparoscopic era remains controversial with various management strategies employed by surgeons. The aim of this study was to ascertain the common practice across a single Australian state, and to see if a ‘best practice’ for CBD stone management could be established.

Laparoscopic transcystic bile duct stenting in the management of common bile duct stones

Background: The management of patients with common bile duct stones associated with stones in the gall bladder remains controversial.

A compliant tip reduces the peak pressure of laparoscopic graspers

Background:u2003 Previous studies have demonstrated that high pressures are generated at the tips of laparoscopic graspers, which can cause tissue injury. This study examines the effect of a compliant edge on tip pressure.

A curved edge moderates high pressure generated by a laparoscopic grasper.

Background: Very high pressures are generated at the interface between the tip of laparoscopic graspers and tissue. The pressure profile suggests that the high pressure is due to stress concentration at the edge of the jaw. Stress concentration at an edge can be modified by curving the edge. This study sought to determine the effect of a curved edge on pressures generated by the jaw of a laparoscopic grasper. Methods: Pressure generated at the instrument tissue interface was measured by a thin film pressure transducer. The two instruments that we compared were identical in every respect except the profile of the jaw edge. One was unmodified; the other had a rounded grasping edge. Load and handle pressure were constant throughout. Tissue pressures generated by the grasper were recorded as the angle of load was increased from vertical (0°) to 135°. Results: Localized pressures at the tip of the unmodified instrument reached a maximum of 1500 kPa. Pressures at the tip of the curved instrument reached a maximum of 920 kPa under identical conditions. Conclusion: High pressures generated at the tip of laparoscopic graspers can be reduced by rounding the edge of the jaw.

Residual gallbladder and cystic duct stones after laparoscopic cholecystectomy

Retained stones in the residual Hartmanns pouch or cystic duct stump are an uncommon cause of post cholecystectomy pain. Two cases of residual gallbladder and one of a retained cystic duct stone are reported. All three cases followed a laparoscopic cholecystectomy where an operative cholangiogram was not performed.

Evaluation of DualMesh for repair of large hiatus hernia in a porcine model

BackgroundProsthetic fascial grafts are frequently used for augmentation of cruroplasty in large hiatus hernia repair to decrease the chances of recurrence. Potential complications such as intraluminal erosion may be related to the constant movement of mesh and diaphragm over the outer surface of the esophagus. This study aimed to evaluate DualMesh for repair of large hiatal defects in a porcine model.MethodsIn this study, 18 Landrace × large white × Duroc crossbred pigs underwent either primary hiatal repair or tension-free prosthetic repair using DualMesh (80 × 50 mm or 80 × 100 mm). The animals were killed at 3 or 28 weeks for macroscopic and histologic evaluation of the hiatal region and gastroesophageal junction.ResultsAll grafts had become encapsulated at 28 weeks, and the majority had filmy adhesions only to the visceral aspect. In all models, the esophagus moved freely over the cut edge of the prosthesis. No signs of intraluminal erosion were documented. At histologic examination, significant ingrowth was noted on the porous side of the mesh, whereas no defined mesothelial layer was identified on the capsule of the nonporous side.ConclusionIn this animal model of large hiatus hernia repair, DualMesh showed optimal characteristics in terms of host tissue incorporation on the porous side and absence of adhesions on the visceral side of the prosthesis. The absence of adhesions and intraluminal erosion in this study may provide reassurance to surgeons using mesh at the hiatus.