Bone Fixation Strap With Locking Head For Sternal Compression
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Solution Overview
Problem
Conventional sternal fixation methods using stainless steel wires for approximating and compressing the sternum during open heart procedures face issues of wire breakage due to tensile forces and require surgeon experience for proper tightening, leading to compromised compression or wire damage.
Innovation Solution
A bone fixation member comprising a flexible strap with teeth and a locking head, along with a leader portion and needle, that secures bone segments by translating through a slot with complementary teeth to prevent backsliding, allowing for controlled tension and reduced irritation, and a bone punch for forming holes in sternal portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If stainless steel wires are twisted to tighten against the sternum, then sternal compression is achieved, but wire breakage occurs due to tensile forces
Solution Approach 1:
The fixation system is divided into separate functional components: a flexible strap for compression, a locking head with teeth for secure engagement, and a needle for insertion. This segmentation allows each component to perform its specific function optimally without the compromises inherent in a monolithic wire system.
Solution Approach 2:
Instead of tightening the wire by twisting (which creates tensile stress), the invention uses a ratchet-like mechanism where the strap is pulled through the locking head in one direction to tighten, while the teeth prevent reverse movement. This inverts the tightening mechanism from rotational tension to linear pull-with-lock.
2Force
If wires are tightened more to improve sternal compression, then compression is enhanced, but wire breakage and cutting into bone increases
Solution Approach 1:
The locking head with its teeth and slot configuration provides inherent feedback control. As the strap is pulled through, the teeth engage at specific intervals, providing tactile and mechanical feedback that prevents over-tightening. The system self-regulates the compression force applied to the sternum.
Solution Approach 2:
The flexible strap material and the ratchet mechanism provide a cushioning effect by allowing gradual, controlled tightening in discrete steps. This prevents sudden excessive forces that could damage the wire or cut into the bone, as the mechanism absorbs and distributes the tightening force over multiple engagement points.
3Ease of operation
If surgeon experience is relied upon for wire tightening, then flexibility in adjustment is achieved, but inconsistent compression and wire failure occur
Solution Approach 1:
The locking head mechanism is designed to be self-regulating. The teeth and slot geometry automatically control the tightening process, allowing the surgeon to simply pull the strap without requiring expertise in applying the correct amount of force. The system itself ensures consistent, reliable engagement.
Solution Approach 2:
The invention changes the operational parameter from requiring manual twisting force (which varies with surgeon skill) to a simple pull-through action with mechanical locking. This parameter change makes the procedure more reliable and less dependent on surgeon experience while maintaining ease of operation.
Data Source
AI summary
A bone fixation member can be configured to secure first and second bone segments of a target bone together in a compressed approximated position. The bone fixation member can include a strap made of a first material, a locking head extending from a proximal end of the strap, and a leader portion extending from a distal end of the strap. The locking head can have a housing and a strap receiving slot that extends through the housing, slot is configured to receive a distal end of the strap. The housing can be tapered such that a distal end of the housing has a thickness that is greater than the thickness of a proximal end of the housing. The leader portion can be configured to be more flexible than the strap. The leader portion can be made of a second material that is different than the first material.