Spinal Fusion Cage Drill Targeting Device
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Solution Overview
Problem
The difficulty in accurately placing a guide pin through a fusion cage using x-ray guidance leads to larger fenestrations, which can result in fusion cage displacement and disturbance of bone grafting material, compromising the success of spinal fusion surgeries.
Innovation Solution
The use of a rigid or articulating drill targeting device that allows precise alignment and insertion of a guide pin without x-ray guidance, enabling the creation of smaller fixation screw holes that match the screw diameter, and incorporating a tilting snap ring mechanism to secure the screw in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If x-ray guidance is used to place the guide pin through the fusion cage, then the surgeon can visualize the cage fenestration, but the fenestration must be significantly larger than the fixation screw to accommodate the guide pin
Solution Approach 1:
The drill targeting device is attached to the fusion cage before the surgery begins, establishing a predetermined trajectory that aligns with the center of the fixation screwhole. This preliminary positioning eliminates the need for large fenestrations during the actual screw placement, as the path is pre-established
Solution Approach 2:
The drill targeting device acts as an intermediary tool that bridges the gap between the surgeon's external perspective and the internal cage fenestration. It provides mechanical guidance through the cage without requiring the surgeon to directly visualize the fenestration, allowing for precise placement through smaller openings
2Ease of operation
If a large screwhole fenestration is used to pass the guide pin, then the guide pin can be inserted, but the fusion cage may partially displace out of the disc
Solution Approach 1:
The drill targeting device is pre-attached to the fusion cage with a predetermined trajectory that centers on the fixation screwhole. This preliminary setup ensures that the guide pin follows the exact path needed, eliminating the need for large fenestrations and preventing cage displacement during insertion
Solution Approach 2:
The patent replaces the x-ray guidance mechanical system with a direct mechanical guidance system (drill targeting device) that is physically attached to the cage. This substitution provides more reliable and precise guidance without the radiation and visualization limitations of x-ray, while maintaining ease of operation
3Ease of operation
If a large screwhole fenestration is used, then the guide pin can pass through, but most of the bone grafting material is placed in the screwhole fenestration which is unwanted
Solution Approach 1:
The drill targeting device establishes a predetermined trajectory through the center of the fixation screwhole before bone grafting material is placed. This preliminary action ensures that the guide pin passes through the exact center, allowing for minimal fenestration size and preventing bone graft material from being displaced into the screwhole
Solution Approach 2:
The patent separates the functions of guide pin passage and bone grafting material containment. By using a precisely centered, minimal fenestration for the guide pin and fixation screw, the remaining larger fenestrations can be dedicated entirely to holding bone grafting material without interference
Data Source
AI summary
A system for implementing an improved spinal fusion cage having a centrally-located fixation screwhole of diameter minimized to accommodate a variable-angle, intervertebral, cannulated fixation screw is disclosed. The system includes a rigid connection between the spinal fusion cage to the shaft of the fixation screw, and a variable angle drill targeting device for directing the fixation screw through the non-visually acquirable, centrally-located fixation screwhole without X-ray or other imaging guidance.