Development of a device to assist force generation for high-load orthopaedic actions

Master thesis (2011)

Contributors

J. Dankelman (mentor)
G.J. Tuijthof (mentor)
Department
BioMechanical Engineering (Mechanical, Maritime and Materials Engineering) (TU Delft)
Copyright: © 2011 Van Gorkum, R.F.P.
Orthopedic Rongeur Gripping force Mechanical amplification Ratchet mechanism
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Published Date

30-05-2011

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Faculty

Mechanical, Maritime and Materials Engineering

Department

BioMechanical Engineering

Abstract

Orthopaedic surgery includes frequent removal of bony tissue with large instruments that require a significant force to operate. An increasing number of surgeons, especially female and older surgeons, cannot operate high-load orthopedic instruments properly because they lack the necessary force or hand span. The goal of this study is to develop a device that assists surgeons with force generation for high-load orthopaedic actions. It should enable surgeons of any age, gender and gripping strength to operate bone excision instruments with their dominant hand only by amplifying the users gripping force. Methods: The device was designed for the “worst case scenario”: a 60 year old female surgeon cutting hard cortical bone with a large rongeur. The device amplification (2.2x) was determined by calculating the discrepancy between the available gripping force for this person (207N) and the maximum bone cutting force (474N), determined by cutting 90 slices of tibia with a large Luer-Stille rongeur. Several qualitative requirements were taken into account, such as maintaining haptic feedback and sterilizibility. The prototype features an amplification mechanism based on ratchets that enables two operating modes: it can either be used like a traditional rongeur or with extra amplification where needed. The device was evaluated by experimentally comparing the amplification of the prototype with the intended amplification. Results: The prototype provided more than the necessary amplification: gripping force is amplified at least 2.8 times in amplification mode. Conclusions: The proposed design shows potential to be a valuable addition to orthopedic instruments because it enables surgeons with less gripping force to cut through hard tissue with one hand. The presented prototype delivers the necessary amplification of gripping force but shows some limitations, for which solutions were presented. When these limitations are solved, clinical testing can be initiated.