Hydropowered minimally invasive surgical bone drill

A flexible bone drill provides advantages over conventional rigid instruments, because it allows surgical access via a minimally invasive approach. A new concept is to achieve this using hydropower. Hydropower could provide the advantage of energy transfer via a compliant hose through which pressurized water is flowing. The goal is to design a hydropowered minimally invasive surgical bone drill. However, in this study is focused on the design of the key element of the instrument: the hydraulic actuator. The most suitable hydraulic actuator was selected with a theoretic analysis using design requirements set for a highly challenging medical case (bone marrow stimulation). First, a speed of 750 rpm, a torque of 0.015 Nm and a maximum dimensional volume of 5 x 10 x 10 mm were set from literature to drill a 1.5 mm hole in human bone. Second, the external gear motor was selected because it met the requirements, needed the least pressure difference, and had a simple design consisting of two gears and a housing. Third, an instrument based on the external gear motor was designed and built. Fourth, the prototype was tested and its performance evaluated. Experiments show that the prototype did not rotate under pressure while a high leakage could be noticed. Eventually, three main causes for the malfunctioning were identified and quantified: Jamming/skewing of the gears, excessive friction and excessive leakage. Recommendations to avoid those issues are presented. However, the feasibility of those recommendations is uncertain, because of the small dimensions of the instrument. Therefore, it is advised to reconsider hydrodynamic working principles since the influence of leakage on their performance is less critical.

Subject

Bone drill
miniature external gear motor
microfracturing
bone marrow stimulation

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http://resolver.tudelft.nl/uuid:31e8ebac-e9fd-494e-b978-1620b00aaff1

Embargo date

2016-06-16

Part of collection

Student theses

Document type

master thesis

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Thesis_Wouter_Gregoor.pdf

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