Epidural Citrate Infusion for Spinal Stenosis Bone Resorption

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Solution Overview

Problem

Current treatments for spinal stenosis, such as decompression laminectomy, carry risks of worsening pain and nerve or spinal cord injury, and existing bone decalcification methods are not effective under physiologic conditions, while epidural injections have limitations like migration and infection.

Innovation Solution

Continuous infusion of an isotonic sodium citrate/citric acid buffer via an epidural catheter to resorb bone contiguous to the epidural space, utilizing citrate's ability to chelate calcium from calcium phosphate and calcium hydroxyapatite at neutral pH, thereby alleviating spinal stenosis symptoms without disrupting the ligamentum flavum or dura mater.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If decompression laminectomy is performed to treat spinal stenosis, then bone is removed to alleviate compression, but risks of worsening pain and nerve or spinal cord injury increase

Engineering Contradiction:

Improvespinal cord compressionVSAvoidrisk of nerve injury

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent replaces mechanical bone removal (laminectomy) with a chemical dissolution process using citrate solution infused through an epidural catheter. The citrate chemically dissolves the bone spur and ligamentum flavum causing stenosis, eliminating the need for mechanical cutting or drilling that carries risks of nerve injury

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces citrate solution as an intermediary substance that mediates between the epidural catheter and the bone tissue. The citrate acts as a chemical agent that selectively dissolves calcium in bone without directly contacting or damaging neural structures, serving as a safe intermediary that achieves bone removal without mechanical trauma

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If traditional bone decalcification methods are used, then bone can be removed, but they are not effective under physiologic conditions of pH, tonicity and temperature

Engineering Contradiction:

Improvebone decalcification rateVSAvoidphysiologic temperature

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The patent changes the chemical parameters of the decalcification solution by using citrate buffer at physiologic pH (7.4) and tonicity (300 mOsm/L) instead of traditional strong acids. This parameter change allows the solution to effectively dissolve bone at body temperature without requiring extreme conditions, making the process compatible with in vivo application

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent utilizes the phase transition of citrate from a solid buffer powder to an isotonic solution that can be infused through an epidural catheter. The solution transitions from a stable buffered state to an active decalcification state upon contact with the calcium-containing bone tissue, enabling controlled bone dissolution under physiologic conditions

Inventive Principle:

Principle #36Phase transitions

3Duration of action of moving object

If epidural catheter is implanted for long term infusion, then continuous treatment is provided, but complications like migration, bleeding, infection and granuloma formation occur

Engineering Contradiction:

Improvecontinuous infusion durationVSAvoidinfection risk

Core Design Contradiction:

Duration of action of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent employs a disposable epidural catheter system that is intended for short-term use (days to weeks) rather than long-term implantation. The catheter is discarded after completing the bone dissolution therapy, eliminating risks associated with chronic indwelling catheters such as infection, granuloma formation, and migration. The temporary nature of the catheter minimizes complication risks while providing sufficient treatment duration

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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

This method effectively resorbs spondylitic bone, providing pain relief for spinal stenosis without the risks associated with traditional surgical procedures and maintains the integrity of surrounding tissues, with citrate being non-toxic and FDA-approved for epidural administration.

Implementation Method 1

Citrate can chelate calcium from calcium phosphate and calcium hydroxyapatite, the two major components of cortical bone

Methodology Applied

Scientific EffectChelation:

Data Source

PatentUS9616040B2Citrate resorption of bone as a treatment for spinal stenosis

Publication Date: 2017.04.11 GOLDBERG JOEL STEVEN

AI summary

Spinal stenosis is a common debilitating illness that produces symptoms of neurogenic claudication, radiculopathy and weakness. Present therapies include administration of analgesics, epidural injections of local anesthetic with corticosteroids and decompression laminectomy. In vitro, citrate ion can resorb vertebral cortical bone by chelating calcium without destruction of the ligamentum flavum or dura mater. This non-enzymatic spontaneous chemical reaction occurs at neutral pH, 37° C. and in an isotonic solution and in vitro produces an average cortical bone weight loss of 17% after 168 hours. In this invention epidural infusion of citrate in the form of an isotonic solution of sodium citrate/citric acid buffer at neutral pH will resorb a significant amount of vertebral bone such that the symptoms of spinal stenosis are ameliorated.