Odontoid Screw with Movable Compression Device
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Solution Overview
Problem
Conventional odontoid screw systems for stabilizing type II odontoid fractures lack the ability to effectively reduce fractures and face challenges in selecting the correct screw length, leading to high failure rates or injury to vital structures.
Innovation Solution
A spinal implant system with an elongated implant featuring a distal threaded portion and a proximal portion with a compression device, allowing for dual compression forces to stabilize the fracture, and a cutting device to adjust and secure the implant length in vivo.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional odontoid screw is used to stabilize a type II odontoid fracture, then the fracture can be immobilized, but the screw lacks the ability to effectively reduce the fracture and has high failure rates due to incorrect length selection
Solution Approach 1:
The implant incorporates a movable compression device that can be adjusted along the longitudinal axis of the elongated implant body after insertion. This dynamic adjustment capability allows the compression force to be optimized post-operatively, resolving the static limitation of conventional screws and enabling effective fracture reduction without requiring precise pre-operative length prediction
Solution Approach 2:
The implant is divided into distinct functional segments: an elongated implant body with threaded distal portion for bone engagement, and a separate movable compression device that can be independently adjusted. This segmentation allows the compression function to be decoupled from the fixation function, enabling reliable stabilization while maintaining ease of compression force adjustment
2Strength
If the odontoid screw is made longer to ensure bicortical purchase, then screw purchase is improved, but the risk of injuring the brainstem or vascular structures increases
Solution Approach 1:
The movable compression device allows the effective length of the implant to be adjusted after insertion. The implant can be inserted with a safe length that avoids vital structures, and then the compression device is moved along the implant body to achieve the desired compression force, eliminating the need to over-lengthen the screw for fear of insufficient purchase
Solution Approach 2:
The movable compression device acts as an intermediary mechanism that transfers compression force to the fracture site without requiring the screw itself to extend excessively into the bone. This intermediary allows bicortical purchase to be achieved with a safer screw length by using the compression device as the primary source of compressive force rather than relying solely on screw length
3Object-affected harmful factors
If the odontoid screw is made shorter to avoid vital structures, then safety is improved, but the screw fails to achieve bicortical purchase and stabilization reliability decreases
Solution Approach 1:
The movable compression device provides dynamic adjustment capability that compensates for the shorter implant length. By allowing post-insertion adjustment of the compression force, the system achieves reliable stabilization with a safer, shorter screw that avoids vital structures while still providing adequate compression through the adjustable mechanism
Solution Approach 2:
The system changes the parameter of compression force delivery from being fixed by screw length to being adjustable by the movable compression device. This parameter change allows the compression force to be optimized independently of implant length, enabling reliable stabilization with shorter, safer implants
4Reliability
If C1 to C2 fusion is performed to stabilize the fracture, then fracture stabilization is achieved, but the patient's ability to move the head and neck is significantly restricted
Solution Approach 1:
The implant applies compression force locally at the fracture site through the movable compression device, rather than requiring global fusion of C1 to C2. This localized treatment stabilizes the fracture while preserving the mobility of the surrounding spinal segments, maintaining head and neck movement capability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides enhanced compression force control and eliminates the need for precise screw length prediction, reducing failure rates and minimizing risk to surrounding structures by allowing in vivo adjustment and securement of the implant.
Implementation Method 1
the distal portion including a set of threads for joining the distal portion with a distal part of the bone fracture
Implementation Method 2
the compression device is movable from an end of the proximal portion towards the distal portion of the elongated implant, wherein the compression device is structured to apply a compression force against a proximal part of the bone fracture
Data Source
AI summary
A spinal implant system includes an elongated implant defining a distal portion interconnected to a proximal portion. The distal portion includes a set of threads for joining the distal portion with a distal part of the bone fracture. The system also includes a compression device coupled to the proximal portion of the elongated implant. The compression device is movable from an end of the proximal portion towards the distal portion of the elongated implant, wherein the compression device is structured to apply a compression force to a proximal part of the bone fracture.