Bioresorbable Tip Connecting Rod for Spinal Stabilization

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Solution Overview

Problem

Conventional surgical implants, such as pedicle screws, often cause impingement of facet joints during minimally invasive procedures, leading to limited movement and discomfort due to their bulkiness and disruptive nature, necessitating a solution that provides effective stabilization while minimizing disruption to normal vertebral functioning.

Innovation Solution

A connecting rod with a non-bioresorbable main shaft and a bioresorbable tip portion, designed for percutaneous insertion, where the bioresorbable tip is gradually absorbed after placement, reducing impingement and allowing for normal vertebral movement without the need for additional surgery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a conventional connecting rod with a permanent tip is used for percutaneous insertion, then insertion is facilitated, but the tip remains attached and impinges on facet joints causing limited movement and discomfort

Engineering Contradiction:

Improveinsertion facilitationVSAvoidfacet joint impingement

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The tip is constructed from bioresorbable material that changes its physical state over time through hydrolysis and enzymatic degradation, transitioning from a solid structural component to dissolved products (lactic acid, carbon dioxide, water) that are eliminated by the body, thereby eliminating the impingement problem while maintaining insertion functionality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The bioresorbable tip performs its insertion function and then is gradually discarded by the body through natural metabolic processes, with the degradation products being recovered and eliminated, eliminating the need for additional surgery to remove the tip

Inventive Principle:

Principle #34Discarding and recovering

2Strength

If a bulky connecting rod is used to provide effective stabilization, then bone fixation is improved, but normal vertebral functioning and facet joint movement are disrupted

Engineering Contradiction:

Improvebone stabilizationVSAvoidvertebral functioning disruption

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The connecting rod is divided into two distinct portions: a non-bioresorbable shaft that provides structural strength and stabilization, and a bioresorbable tip that facilitates insertion but eventually degrades, allowing the stabilizing function to be separated from the function that causes disruption

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The tip material undergoes parameter changes through controlled degradation, transitioning from a rigid structural component to dissolved metabolic products, thereby reducing its disruptive effect on vertebral functioning while the shaft maintains necessary stabilization strength

Inventive Principle:

Principle #35Parameter changes

3Strength

If a non-bioresorbable implant is used for bone stabilization, then structural support is maintained, but the implant obscures imaging results and may cause immune reactions

Engineering Contradiction:

Improvestructural supportVSAvoidimaging obstruction and immune reactions

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The implant material undergoes parameter changes through controlled degradation, transitioning from a permanent opaque structure to dissolved products that do not obstruct imaging, while the degradation timeline is controlled to maintain necessary structural support during the bone healing period

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The connecting rod uses composite construction with non-bioresorbable shaft material (metal or ceramic) for structural support and bioresorbable tip material (polymer) that degrades without causing imaging obstruction or immune reactions

Inventive Principle:

Principle #40Composite materials

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 connecting rod effectively stabilizes bone anchors while minimizing disruption to vertebral functioning, reducing post-operative complications like facet joint impingement and facilitating recovery by allowing for natural bone healing without long-term structural dependency on the implant.

Implementation Method 1

Most bioresorbable materials are polymers that are slowly hydrolyzed into lactic acid which is then metabolized by the liver into carbon dioxide and water

Methodology Applied

Scientific EffectHydrolysis: Hydrolysis

Implementation Method 2

the tip portion that is bioresorbable... After placement, the bioresorbable tip is resorbed into the patient's body

Methodology Applied

Scientific EffectBiological absorption: Absorption (physical)

Implementation Method 3

lactic acid which is then metabolized by the liver into carbon dioxide and water and easily eliminated by the body

Methodology Applied

Scientific EffectMetabolism: Aerobic Digestion

Data Source

PatentUS8439952B2Connecting rod for bone anchors having a bioresorbable tip

Publication Date: 2013.05.14 NUVASIVE INC

AI summary

The invention provides a connecting rod for bone anchors such as pedicle screws. The rod is constructed to include a main shaft portion that is not bioresorbable and a tip portion that is bioresorbable. The tip facilitates percutaneous insertion into a patient's body. After placement of the rod, the bioresorbable tip is resorbed preventing post-operative complications such as impingement of adjacent spinal facet joints.