Polyaxial Bone Fixation Element In-Situ Assembly
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Solution Overview
Problem
Existing spinal fixation systems lack simplicity and flexibility in securely mounting spinal rods to vertebrae, particularly in polyaxial rotation, which complicates surgical procedures and access during spinal stabilization and fusion.
Innovation Solution
A polyaxial bone fixation element comprising a bone anchor, a collet, and a body with a rod-receiving channel, allowing in-situ assembly where the bone anchor is secured to the vertebra before being received within the body, enabling maximum visibility and access, and featuring a locking cap for secure rod positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the bone anchor is secured to the vertebra before being received within the body, then maximum visibility and access around the anchoring site is achieved, but the device complexity increases due to in-situ assembly requirements
Solution Approach 1:
The fixation element is divided into separate components (body, collet, bone anchor) that can be implanted in a sequence. The bone anchor is first secured to the vertebra, then the body and collet are assembled in-situ, allowing surgical access and visibility to be maintained while achieving secure fixation.
Solution Approach 2:
The bone anchor is implanted and secured to the vertebra before the body and collet are assembled around it. This preliminary action allows the anchoring site to be prepared and accessed optimally before the final fixation structure is assembled.
2Adaptability or versatility
If polyaxial rotation capability is provided, then flexibility in positioning the spinal rod and pedicle screws is improved, but the device complexity increases due to additional rotational degrees of freedom
Solution Approach 1:
The collet is designed with flexible arms that can dynamically adjust to accommodate bone anchors inserted at various angles. The polyaxial capability is achieved through the flexible arms' ability to bend and conform, rather than through complex mechanical joints, maintaining simplicity while providing rotational flexibility.
Solution Approach 2:
The collet's flexible arms act as thin, compliant structures that can bend and adapt to different insertion angles of the bone anchor. This flexibility provides polyaxial rotation capability without requiring complex mechanical mechanisms, thus avoiding increased device complexity.
3Reliability
If a locking cap is used to secure the rod position, then the reliability of rod mounting is improved, but the ease of operation decreases due to additional locking steps
Solution Approach 1:
The locking cap is designed to be engaged and disengaged by the surgeon using standard surgical instruments without requiring additional tools or complex procedures. The self-contained locking mechanism allows the surgeon to secure the rod position reliably while maintaining ease of operation through intuitive engagement and disengagement.
Data Source
AI summary
The present disclosure includes a polyaxial bone fixation element for use in spinal fixation to interconnect a longitudinal spinal rod with a patient's vertebra. The polyaxial bone fixation element preferably includes a bone anchor, a collet, a body, and a locking cap. The polyaxial bone fixation element preferably enables in-situ assembly. That is, the polyaxial bone fixation element is preferably configured so that in use, the bone anchor may be secured to the patient's vertebra prior to being received within the body. Accordingly, the polyaxial bone fixation element enables a surgeon to implant the bone anchor without the body to maximize visibility and access around the anchoring site. Once the bone anchor has been secured to the patient's vertebra, the body can be snapped-onto the bone anchor. The bone anchor preferably also includes a second tool interface so that a surgical instrument can be directly coupled to the bone anchor.