Intramedullary Nail System with Adjustable Length and Bone Anchor

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Solution Overview

Problem

Existing flexible intramedullary nails face challenges such as unpredictable nail length requirements, risk of screw stripping, nail migration, and postoperative complications like fracture shifting and tissue irritation, particularly in skeletally immature patients and those with displaced fractures.

Innovation Solution

An intramedullary nail system with a rigid link to an anchor, featuring a tulip bed cavity for precise screw insertion, a mechanism to determine and cut the exact nail length, and a bone anchor with a tightening mechanism to prevent axial and rotational movement, ensuring stable fixation and minimal tissue irritation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a flexible intramedullary nail with a slot is used to avoid growth plate injury, then the nail can enter the medullary cavity away from the growth plate, but the nail may migrate axially and rotate after implantation causing screw loosening, breakage or pull-out

Engineering Contradiction:

Improvegrowth plate injuryVSAvoidnail fixation stability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

A bone anchor is installed in the bone before inserting the intramedullary nail. The anchor serves as a pre-prepared fixation point that prevents nail migration and rotation after implantation, eliminating the need for post-implantation adjustment while maintaining growth plate safety

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A bone anchor acts as an intermediary component between the intramedullary nail and the bone. The anchor provides a stable attachment point that secures the nail against axial movement and rotation, solving the reliability issue without compromising the flexible nail's ability to avoid the growth plate

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If multiple nail lengths are stocked to accommodate different fracture patterns, then various nail lengths can be provided in 1 cm increments, but the inventory complexity increases and trial pins may not follow the same path as the final nail

Engineering Contradiction:

Improvenail length varietyVSAvoidinventory management

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The intramedullary nail is designed with a variable length feature, allowing a single nail design to be adjusted to different lengths during surgery. This eliminates the need to stock multiple pre-cut nail lengths while maintaining the ability to accommodate different fracture patterns and patient anatomies

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The nail system transitions from static pre-cut lengths to a dynamic adjustable length configuration. The nail can be inserted at full length and then trimmed to the exact required length after the anchor is in place, allowing adaptation to different fracture patterns without inventory complexity

Inventive Principle:

Principle #15Dynamics

3Ease of repair

If the nail end and bone screw head sit on top of the outer bone surface to prevent burial, then extraction is facilitated, but surrounding tissue is irritated causing prominent, palpable and painful implants

Engineering Contradiction:

Improvenail extractionVSAvoidtissue irritation

Core Design Contradiction:

Ease of repairVSObject-affected harmful factors

Solution Approach 1:

A countersink cavity is prepared in the bone before installing the bone anchor. This preliminary action creates a recess that allows the anchor and nail end to sit flush with or slightly below the bone surface, preventing soft tissue irritation while maintaining easy access for future nail extraction

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The solution moves the nail end from a protruding position (causing tissue irritation) to a recessed position within the countersink cavity. This dimensional change eliminates soft tissue prominence and pain while the anchor's external portion remains accessible for future nail removal

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Reliability

If a bone screw is used to secure the nail end to the bone through the slot, then the nail is anchored to the bone, but screw thread stripping occurs when over-tightening or when bone thickness or density is insufficient

Engineering Contradiction:

Improvenail anchoringVSAvoidscrew fixation strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The bone anchor serves as an intermediary fixation device that replaces the bone screw. The anchor provides a larger surface area and more distributed load path into the bone, eliminating the risk of screw thread stripping while maintaining secure nail anchoring. The anchor's design allows for proper load distribution regardless of bone thickness or density variations

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10426529B2Surgical systems, kits and methods for setting bone segments

Publication Date: 2019.10.01 BARRY MARK A

AI summary

An intramedullary nail system is provided with at least one resilient, elongate nail body configured to extend axially along a medullary bone cavity, and at least one bone anchor. The bone anchor includes a distal bone engagement portion configured to secure the anchor to a bone, a proximal nail engagement portion configured to receive a portion of the nail body therethrough, and a tightening mechanism configured to move from a movable state in which the nail body may slide axially and rotate through the engagement portion and a fixed state in which the nail body is prevented from moving relative to the engagement portion. Methods of use and surgical kits are also provided.