Intramedullary Nail With Dynamic Compression Springs
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Solution Overview
Problem
Current intramedullary nail systems fail to maintain continuous dynamic compression across fracture or fusion sites during the healing process due to biological resorption of materials like stainless steel and titanium, leading to loss of compression and increased risk of non-union or pseudo-arthrosis.
Innovation Solution
An intramedullary nail with a cannulated design incorporating mechanical compression members such as springs or elastic bands that provide predictable and reproducible compression, allowing for adjustable compressive force and rotational stability without the need for external mechanisms or weight-bearing forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stainless steel or titanium fixation constructs are used to provide initial stability, then axial and torsional stability is achieved, but compression is lost over time due to biological resorption
Solution Approach 1:
The intramedullary nail incorporates a dynamic compression mechanism that allows the nail to move relative to the bone fragments, maintaining compression force as the bone heals and resorbs. This dynamic adjustment compensates for the biological resorption process, keeping the fracture surfaces compressed throughout the healing period rather than losing compression as occurs with static fixation constructs.
Solution Approach 2:
The compression force parameter is made variable through the dynamic mechanism, allowing the compression level to change in response to bone resorption and healing progress. The system transitions from a static compression state to a dynamic one where compression parameters automatically adjust to maintain optimal fracture surface contact throughout the healing timeline.
2Reliability
If compression is applied to prevent interfragmentary motion, then bone healing is promoted, but excessive compression can damage blood supply to the fracture site
Solution Approach 1:
The dynamic compression mechanism automatically self-regulates the compression force applied to the fracture site. As the bone heals and the gap closes, the mechanism naturally adjusts the compression level, providing sufficient force to maintain stability while avoiding excessive compression that would compromise blood supply. The system serves itself by responding to the actual state of the fracture rather than applying fixed compression.
3Strength
If standard intramedullary nails are used to provide axial stability, then fracture fixation is achieved, but rotational stability is insufficient
Solution Approach 1:
The intramedullary nail incorporates an asymmetric cross-sectional shape rather than a symmetric circular design. This asymmetric geometry creates inherent rotational resistance by engaging differently with the bone cortex in different orientations, preventing unwanted rotation while maintaining axial stability. The asymmetric profile acts as a mechanical key that locks into the bone, providing both axial and rotational control.
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 nail system ensures continuous dynamic compression across the fracture or fusion site from the time of surgery through the healing process, reducing the risk of non-union and promoting bone regeneration by maintaining stable compression and rotational stability.
Implementation Method 1
a compression spring contained within the inner channel, the compression spring having a proximal end and a distal end
Implementation Method 2
an elastic band contained within the inner channel, the elastic band having a proximal end and a distal end
Implementation Method 3
Sustained compressive therapy can also be osteoinductive, due to its piezoelectric effects on osteoblasts themselves
Data Source
AI summary
The present invention describes an intramedullary nail for use in orthopedic surgery for the fixation of bone fractures and fusion sites. The nail employs one or more internal loaded springs, biocompatible elastic or rubber bands, or other mechanism that provides continuous dynamic compression across the healing site throughout the healing process. By altering the size, tension and/or number of the internal compression devices, the amount of compression may be customized on a case-by-case basis. Further, the slots within the nail for its attachment can be utilized to create a torsional force when desired. The nail can have a cross-sectional shape that prevents its rotation. A system and method of use is also described.