Novel Method for Comprehensively Assessing the Biomechanical Risks Associated With the Use of Minimally-invasive Surgical Instruments

As the incidence of neuromuscular disorders among laparoscopic surgeons increases, research to understand the biomechanical risks associated with the use of minimally-invasive surgical instruments has been underdeveloped. A method using detailed simultaneous biomechanical measurements was developed in order to analyze the quantities that are closely related to potential risks and to yield information relevant to the operating characteristics of these instruments, including ergonomic functionality and efficiency.

The following metrics and respective analytic modalities are used in the developed method and are employed simultaneously in the collection of data during a simulated surgical task.

  • Postures, Movement Patterns, and Technique. An Opto-Electronic Motion Capture (OEMC) system is used to track the head, neck, torso, and upper extremities of the surgeon and the handle and tip of the laparoscopic instrument. OEMC data generates simultaneous three-dimensional movements and movement durations of the human-instrument system, identifying typical postures, movement patterns, and techniques that are inherent to the surgical task and/or instrument.
  • Muscle Activity and Fatigue. Surface Electromyographic electrodes are placed over the Flexor Carpi Ulnaris and Extensor Carpi Ulnaris muscles to record activity levels of these wrist stabilizers and assess instrument task demands and fatigue. Data is analyzed for differences in static and dynamic muscle activity during instrument usage and complements OEMC measurements to yield an intrinsic physiological correlate of observed posture and movement. EMG also provides assessments of various user forces that accompany awkward/strained postures and dynamic movements, which are critical to patterns of discomfort and can lead to biomechanical inefficiency and injury.
  • Grip Force and Push/Pull Force. Thin-film force sensors are mounted on the handle and the common gripping/operating points of the surgical instrument to directly measure levels of dynamic and static grip forces during use. Grip force exertions is a good predictor of potential injurious conditions, such as repetitive strain and fatigue. A force plate is used to measure the ground reaction forces of the surgeon, calculate the push/pull forces associated with instrument use, and to tracking of the surgeon’s overall center of gravity, which are critical to understanding operator technique and stability. Force measurements provide a better understanding of awkward postures, inefficient ranges of motion, and abnormal patterns of movement.

A laparoscopic trainer, having no vertical walls, was also developed to allow the OEMC system to track position, movement, and articulation angle of the instrument tip. Tip tracking assists with understanding surgeon technique and accuracy and potential correlations between instrument design and surgical plane perception.

Results generated from this method will identify and isolate significant biomechanic behaviors of the human and human-instrument system and differentiate between efficient and inefficient postures, movement patterns, muscle recruitment, forces and moments, etc. Data interpretation can establish criteria to be used as a basis for design and development of the instruments, including proper use technique and acceptable biomechanical loadings. Future research involves the prediction of potential short-term and long-term injuries associated with minimally-invasive surgical instrument use. 

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