Dynamic Compression Bone Screw for Maintaining Fixation During Subsidence
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Solution Overview
Problem
Existing bone screws and fasteners fail to provide sufficient fixation and strength against bending loads, multi-axial forces, and off-axis loading during the healing process, leading to subsidence and pressure loss at the bone interface.
Innovation Solution
A dynamic compression implant with a distal and proximal member, a tension member, and an interpositional member that transmits torque and limits length, ensuring continuous compression across bone portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing bone screws and fasteners are used, then initial fixation is provided, but fixation strength and reliability deteriorate over time due to subsidence, resorption, and loosening under bending loads and multi-axial forces
Solution Approach 1:
The bone screw incorporates a dynamic tension member (spring or elastomeric element) that allows the screw to adapt its length and maintain compression force over time. The tension member elongates as bone subsides or resorbs, preventing loss of compression and maintaining fixation reliability throughout the healing process.
Solution Approach 2:
The tension member's elastic properties enable the screw to change its mechanical parameters (length, compression force) in response to bone healing dynamics. As bone subsides or the interface changes, the tension member adjusts its elongation to maintain optimal compression force at the bone interface.
2Stability of the object's composition
If bone portions move or subside during healing, then natural healing process occurs, but compression force at bone interface is lost leading to fixation failure
Solution Approach 1:
The dynamic tension member allows the screw to adapt to bone motion and subsidence while maintaining stable compression. The spring or elastomeric element dynamically adjusts its length to accommodate healing bone movement while continuously applying compressive force to the bone interface.
Solution Approach 2:
The tension member acts as a feedback mechanism that responds to changes in bone position and compression force. As bone subsides or moves, the tension member elongates accordingly, automatically adjusting to maintain the desired compression force without requiring external intervention.
3Strength
If rigid bone fixation is applied, then initial stability is achieved, but the fixation cannot accommodate bone subsidence and motion leading to loosening
Solution Approach 1:
The bone screw transitions from a rigid structure to a dynamic system with a tension member that can elongate. This allows the fixation to maintain strength while adapting to subsidence and motion, preventing loosening by continuously maintaining compression at the bone interface.
Solution Approach 2:
The tension member functions as a flexible element within the screw structure, allowing deformation and elongation to accommodate bone subsidence while maintaining the overall structural integrity and compression force of the fixation device.
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 implant maintains consistent compressive force despite subsidence and motion, enhancing bone fixation and healing by preventing loosening and maintaining pressure at the bone interface.
Implementation Method 1
a tension member with a proximal end coupled to the proximal member, and a distal end coupled to the distal member such that, in response to motion of the distal member distally away from the proximal member, the tension member elongates and urges the distal member to move proximally toward the proximal member
Data Source
AI summary
A dynamic compression implant may be insertable into a bone, and may have a distal member with distal bone-engaging threads, a proximal member that slidably engages the distal member, and a tension member with a proximal end coupled to the proximal member, and a distal end coupled to the distal member such that, in response to motion of the distal member distally away from the proximal member, the tension member elongates and urges the distal member to move proximally toward the proximal member. The bone screw may further have an interpositional member, formed separately from the proximal member and the distal member, that cooperates with the proximal member and the distal member to form a torque transmission feature that transmits torque between the proximal member and the distal member. The dynamic compression implant may be a bone screw, intramedullary implant, or other implant that applies compression across two bone portions.