11/10/2017
This week we had an intensive creative brainstorming session for the mechanical design and amassed the following ideas:
We have learned that, despite the rod and the head of the pedicle screw being anodized, when the rod is tightened down and locked into place, the pressure bares the titanium and creates an electrical connection. This electrical connection effectively links both screws that share a rod and creates a much broader area of stimulation than intended. This is problematic because, not only do we want individual control over each screw, but it also adds much more potential for leak current. A possible solution to this is identifying a material that is biocompatible and meets the strength requirements but is non-conductive. Another option is to explore different designs for polymer spacers/sleeves that can be placed over the rod that will not compromise any of its structural integrity, but will prevent undesirable electrical connections from being made.
With regard to microwire placement, we are opposed to the wire being an exposed loop between the head of the screw and its attachment to the circuit, as we deem this a likely safety hazard (delicate wire, easy to displace). We have begun to design potential options that would integrate the electrical connection into the interface between the circuit and the head of the screw, eliminating the need for a microwire entirely. Another option is to have the circuit placement modified so that the stimulating wire output location is protected within the body of the pedicle screw tulip. However, this option will add more intricate wiring steps for the surgeon which is a major concern for the viability of the product.
Before our next group meeting, Nathan will research alternate materials that share a similar strength profile to titanium but are non-conductive. Natalie N. will research binary counters in preparation for more intensive programmable circuit design next week. Natalie O. will research variability in spine dimensions and vertebrae spacing that will be taken into account as factors for the mechanical design (ie. How important adjustability might be).
This week we had an intensive creative brainstorming session for the mechanical design and amassed the following ideas:
- A sleeve with adjustable positioning on the rod,
- A cap that will attach to the head of the pedicle screw tulip by threading the inside of the existing locking screw and creating a complimentary thread on the circuit housing,
- A cap that will attach to the end of the rod to give additional surface area,
- A design that is contoured to fit closely around the entire body of the pedicle screw tulip (“sticker”),
- A sleeve with a non-conductive rod to prevent stimulating the rod when attempting to stimulate a single screw,
- A sleeve with a notched channel in the rod filled with nonconductive polymer to carry the wire from sleeve to screw, and
- A sleeve placed in the position where the rod meets the pedicle screw to eliminate exposed wire on the rod.
We have learned that, despite the rod and the head of the pedicle screw being anodized, when the rod is tightened down and locked into place, the pressure bares the titanium and creates an electrical connection. This electrical connection effectively links both screws that share a rod and creates a much broader area of stimulation than intended. This is problematic because, not only do we want individual control over each screw, but it also adds much more potential for leak current. A possible solution to this is identifying a material that is biocompatible and meets the strength requirements but is non-conductive. Another option is to explore different designs for polymer spacers/sleeves that can be placed over the rod that will not compromise any of its structural integrity, but will prevent undesirable electrical connections from being made.
With regard to microwire placement, we are opposed to the wire being an exposed loop between the head of the screw and its attachment to the circuit, as we deem this a likely safety hazard (delicate wire, easy to displace). We have begun to design potential options that would integrate the electrical connection into the interface between the circuit and the head of the screw, eliminating the need for a microwire entirely. Another option is to have the circuit placement modified so that the stimulating wire output location is protected within the body of the pedicle screw tulip. However, this option will add more intricate wiring steps for the surgeon which is a major concern for the viability of the product.
Before our next group meeting, Nathan will research alternate materials that share a similar strength profile to titanium but are non-conductive. Natalie N. will research binary counters in preparation for more intensive programmable circuit design next week. Natalie O. will research variability in spine dimensions and vertebrae spacing that will be taken into account as factors for the mechanical design (ie. How important adjustability might be).