Biomechanical evaluation of user fatigue during burring with the MAKO RIO surgical system

Student thesis: Doctoral Thesis

Abstract

The MAKO RIO (MAKO Surgical, Stryker, Mahwah, NJ, USA) is an assistive surgical robotic arm system developed to increase the accuracy of bone cuts in joint replacement surgery. A high-speed cutting burr is mounted on the arm and is manoeuvred by the surgeon. The robotic arm allows free movement of the burr through the calculated cutting volume but restricts movement, and hence cutting, outside of this volume.Localised fatigue anecdotally reported during burring from high output users of the MAKO RIO system is an issue. An ergonomic assessment of the MAKO RIO was carried out to review possible causes of the complaint of discomfort and fatigue. A clinical trial was observed and assessed for typical use of the system. This assessment culminated in a time analysis review of video footage recorded, defining a typical workflow of the surgery and details of its constituent parts. The clinical trial didn't represent a high output use of the system, but a number of users presented discomfort associated with fatigue.After observing fatigue in users of the system, the project explored the biomechanical reasons for potential causes of this fatigue. A testing protocol of optical tracking, EMG and a force transducer was developed to assess users performing repetitive burring stages of the surgery. The output from the assessment showed high levels of muscle activity, poor posture and large forces that ultimately led to fatiguing of muscles in the lower arm. Specifically, the most significant fatigue was seen in the intrinsic muscles of the hand, with the high grip forces being held for extended periods and a splayed hand over the handle of the robotic arm.A new prototype handle was also available for assessment to investigate if this would resolve the issues with the current handle. While there were some improvements in some muscles, extension and grip muscles were still presenting fatigue. The manoeuvring of the burr is still shown to take an extended length of time and require large forces from muscles that eventually cannot be met. Within high output users, either this accumulation of demand on these muscles over the day or the increased probability of a patient with sclerotic bone on a surgical list would lead these users to experience fatigue when working with the MAKO RIO system.Finally, some conceptual ideas for improvements to the system are suggested throughout the thesis. Fundamentally, however, the cutting method of a burr while enabling accurate cuts and ability to create unique shapes in the bone is not suitable for large volume resection of hard, sclerotic bone.
Date of Award1 Jan 2014
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council) & MAKO Surgical Corp.
SupervisorPhilip Rowe (Supervisor) & Hong Yue (Supervisor)

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