Modular Pedicle Screw Bottom-Loaded Head Assembly
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Solution Overview
Problem
Conventional 'top loaded' pedicle screw assemblies obstruct a surgeon's vision and access during operative tasks, and switching between polyaxial and uniplanar pedicle screws after implantation requires removal of the previously implanted screw, which can weaken the bone.
Innovation Solution
The development of 'bottom loaded' or 'modular' pedicle screw assemblies, where the modular head is configured to receive the bone screw after it has been secured to the bone, allowing for improved access and the ability to switch between polyaxial and uniplanar configurations without removing the screw from the bone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional top loaded pedicle screw assembly is used, then the housing can be positioned over the screw head during implantation, but the housing obstructs the surgeon's vision and access during operative tasks
Solution Approach 1:
The patent inverts the conventional loading sequence by implementing a bottom-loaded design where the bone screw is inserted into the housing from the distal end after the screw has been secured to the bone. This reversal eliminates the housing obstruction problem during critical operative tasks while maintaining proper assembly function.
Solution Approach 2:
The bone screw is implanted into the bone and secured in the desired position before the housing is attached. This preliminary action allows the surgeon to perform decortication and decompression tasks with unobstructed vision and access, then complete the assembly afterward.
2Ease of operation
If a conventional top loaded pedicle screw assembly is used, then the housing is positioned over the screw head, but the housing is subject to flop around the head of the screw which complicates handling and alignment
Solution Approach 1:
By inverting the loading sequence to bottom-loaded design, the housing is attached to the distal end of the already-positioned screw. This eliminates the flopping issue because the housing is secured after the screw is firmly anchored in bone, providing immediate stability without handling complications.
3Adaptability or versatility
If a conventional top loaded pedicle screw assembly is used, then the housing is positioned over the screw head, but switching from polyaxial to uniplanar configuration after implantation requires removal of the previously implanted screw which can weaken the bone
Solution Approach 1:
The pedicle screw assembly is divided into separable components: the bone screw and the housing. This segmentation allows the housing to be detached and replaced with a different type (polyaxial or uniplanar) without removing the already-implanted bone screw, thus preserving bone integrity while providing configuration flexibility.
Solution Approach 2:
The assembly design allows dynamic reconfiguration by enabling the housing to be removed and replaced after the screw is implanted. This dynamic capability provides adaptability for intraoperative decision-making without compromising the anchored screw or bone strength.
Data Source
AI summary
A modular pedicle screw for spinal fixation. The pedicle screw includes a bone screw and a modular head assembly. The bone screw having a head and a shank, the head defining at least one groove. The modular head assembly includes a housing having a proximal end, a distal end and a throughbore extending along a longitudinal axis of the housing between the proximal and distal ends of the housing, and an anvil disposed within the throughbore. The modular head assembly includes at least one protrusion sized and shaped to be received by the at least one groove for restricting relative movement between the housing and the bone screw to a single plane.