Spinal Receiver Body Non-Uniform Wall Thickness
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Solution Overview
Problem
Current spinal fixation systems require significant force to advance or secure a fixation rod into a receiver body, causing stress on the receiver body and potential disengagement of the screw threads.
Innovation Solution
The design of a receiver body with external geometries that facilitate easy and secure attachment of instruments, provide pivot points, and distribute wall thickness non-uniformly to withstand shear forces, allowing for efficient rod insertion and locking without radial splaying, and accommodating various instruments for different operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If significant force is applied to advance or secure the fixation rod into the receiver body, then the rod is properly positioned and fixed, but stress on the receiver body increases and screw threads may disengage
Solution Approach 1:
The receiver body is segmented into distinct functional zones: a head portion for instrument engagement, a body portion for rod reception, and a tail portion for bone screw engagement. This segmentation allows each zone to be optimized for its specific function, distributing stresses appropriately and preventing force concentration that could compromise overall integrity.
Solution Approach 2:
The receiver body exhibits varying wall thicknesses at different locations - thicker walls in the head and tail portions to withstand instrument and screw forces, and thinner walls in the body portion to facilitate rod insertion. This local quality variation optimizes strength where needed while reducing unnecessary material and stress concentration elsewhere.
2Strength
If significant force is applied to secure the rod in the channel within the receiver body, then the rod is firmly fixed, but the screw threads may disengage from the bone screw
Solution Approach 1:
The receiver body is segmented into distinct functional zones: a head portion for instrument engagement, a body portion for rod reception, and a tail portion for bone screw engagement. This segmentation allows each zone to be optimized for its specific function, distributing stresses appropriately and preventing force concentration that could compromise overall integrity.
Solution Approach 2:
The receiver body exhibits varying wall thicknesses at different locations - thicker walls in the head and tail portions to withstand instrument and screw forces, and thinner walls in the body portion to facilitate rod insertion. This local quality variation optimizes strength where needed while reducing unnecessary material and stress concentration elsewhere.
3Ease of manufacture
If the receiver body has uniform wall thickness, then manufacturing is simplified, but it cannot withstand shear forces during rod insertion without radial splaying
Solution Approach 1:
The receiver body exhibits varying wall thicknesses at different locations - thicker walls in the head and tail portions to withstand instrument and screw forces, and thinner walls in the body portion to facilitate rod insertion. This local quality variation optimizes strength where needed while reducing unnecessary material and stress concentration elsewhere.
Data Source
AI summary
A receiver body for an elongated spinal fixation element includes a housing portion with one or more flanges extending outwardly. In one embodiment, the receiver body includes first and second flanges extending outwardly from the housing portion. The housing portion includes first and second slots that form a passage through the housing portion. Each flange has a circular perimeter edge and a chamfered section, the chamfered section having a notched undercut for engagement with an instrument. In another embodiment, the receiver body includes a housing portion having a circular flange with a first chamfered section and a second chamfered section diametrically opposite the first chamfered section. The first chamfered section has a first aperture that opens out beneath the flange, and the second chamfered section has a second aperture that opens out beneath the flange. The first and second apertures form diametrically opposed pivot-attachment points for an instrument.