Force-based assessment of tissue handling skills

Force-based assessment of tissue handling skills

Horeman, T.

Dankelman, J. (promotor)
Jansen, F.W. (promotor)
van den Dobbelsteen, J.J. (copromotor)

Mechanical, Maritime and Materials Engineering

BioMechanical Engineering

2014-04-01

In laparoscopic surgery, special instruments with long and slender shafts are inserted through small incisions in the abdominal wall. A laparoscope is used for a clear vision inside the inflated abdominal cavity while laparoscopic graspers and cutters are used for manipulation of tissue. The use of long instruments makes it difficult to “feel” the force exerted on tissue during manipulation especially when friction factors disturb the force sensation even further. Tissue manipulation plays an important role in surgery and there is relatively little knowledge of forces applied on tissue during surgery. The main objectives of this thesis were to develop force measurement systems to measure the forces during training, to combine motion and force measurements to come to objective assessment of training of basic MIS skills, and finally to develop force feedback systems to improve force application during training. The first part of this thesis focuses on the force exerted by the instrument tips during placement of surgical sutures. In many educational programs in surgery, the suture task is used to test the technical skills of the trainee. We proved that the force exerted on the suture pad can be recorded without modification of the instruments or suture pad if a 3DOF force sensor is placed under the suture pad in a box trainer. We showed that performance parameters can be calculated from recorded force data to expose skills important for safe tissue handling during suturing. A validation study showed that it is possible to classify participants with an accuracy of 84% if only force parameters are used. The second part of this thesis describes a method to reduce the tissue handling force of trainees. By generating a virtual arrow in the laparoscopic image that represents the size and direction of the exerted force during suturing in real time, we found that training with well explained visual feedback can help trainees to minimize the interaction force during needle insertion in a box trainer. For training of wound suturing outside the box trainer, we found that colours, representing the exerted force on the tissue, can help trainees to balance forces between the two tensioned threads during knot tying and to improve the quality of the knot. In another study we showed that it is possible to inform the surgeon about the pulling force during surgery if a small and lightweight sensor is used that can be easily attached to the tensioned thread. The third part of this thesis we integrated the TrEndo and a force platform into ForMoST, a box trainer that measures both tissue handling force as instrument motion. For this box trainer we developed and validated two new bimanual training tasks for training of tissue handling. The validation study performed with novices, intermediates and experts indicated that force parameters are not strongly correlated to motion parameters and that force and motion parameters have similar discriminative power in both tasks. A study performed with novices that received visual force feedback or visual time feedback during training indicated that visual force feedback during training reduces the tissue manipulation force significantly even when a post task is performed that is different from the training task. We showed that training with visual force feedback improves tissue handling skills with no negative effect on task time and instrument motion and that training with visual time feedback improves instrument motion and task time, but does not improve tissue manipulation skills. This thesis contributes to the field of training of surgical skills in multiple ways. Mechanical force sensors were developed that can be used for training of tissue handling, to find force thresholds for traction on tissues or for safety monitoring during suturing of incisions. It is shown that force parameters that reflect tissue handling or suture tension, can now be used to inform surgeons about the risk of tissue damage while training laparoscopic skills or suturing tissues.

tissue handling skills
force parameters
motion parameters
surgical sutures
laparoscopy
training

https://doi.org/10.4233/uuid:0fdc13c0-af9a-4f67-96f5-28107bbec3c0

9789461862686

Institutional Repository

doctoral thesis

(c) 2014 Horeman, T.