Design of an In-situ Spinal Rod Cutter for Orthopaedic Surgeons

Surgical Tool;Rod Cutter;Engineering Design;Spinal Rod Cutter;Mechanical Design

Bodo, Andreadvisor:Medley, John ; affiliation1:Faculty of Applied Health Sciences ; advisor:Parham, Rasoulinejad ; advisor:Yang, Victor ; Medley, John ; Parham, Rasoulinejad ; Yang, Victor ;

University of Waterloo

关键词: Rod Cutter;    Spinal Rod Cutter;    Master Thesis;    Surgical Tool;    Mechanical Design;    Engineering Design;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/12403/5/Bodo_Andre.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

As spine deformities scoliosis and kyphosis progress in severity, surgical treatmentis often required. Implant rods are attached by bone screws to the spinal vertebrae tocorrect these deformities and stabilize the spine. It can be difficult to cut these rods to theideal length before implantation and sometimes these rods are too long and must be cutin-situ. Also, when revision surgery is performed to replace a rod section, in-situ rodcutting must be performed. The rods are difficult to cut and only manual rod cutting toolsare available. These rod cutters are physically demanding to use and difficult to positionwhile avoiding any spurious with the exposed spine. There is a clear need for an improvedin-situ rod cutter. Thus, the objective of this thesis is to develop a new and improveddesign for an in-situ rod cutter.Experimental work was done to show that shear cutting and bolt-cutting techniquesproduced the most desirable results for cutting spinal rods in-situ. The shear cuttingtechniques required slightly less force than bolt cutting techniques and produced acleaner rod cut with less deformation. It was found that cutting force increased with thediameter of the spinal rod, regardless of the rod material. Constraints and criteria wereestablished to guide the design of a new in-situ rod cutter. It was decided that any attemptat designing a new in-situ cutter must include a non-manual power source for operation.Two design alternatives, a shear cutting design and bolt-cutting design were presentedand scored in an engineering design process. A shear cutter design was initially chosenand work was done to implement the shear cutter design. However, the prototypefractured in initial testing and the shear cutter design was abandoned. A bolt-cutter designwas then developed and a 3D printed prototype was made to demonstrate the mechanisminvolved. Analysis was performed to estimate the mechanical advantage of themechanism used to amplify the force applied by a pneumatic cylinder used as the powersource. Further development was required to implement the bolt-cutting design but initialprogress in this design project was achieved. It is recommended that stress analysis,prototyping and testing be done to move this design towards application in spinal surgery.