Cam Coupling Rod Reducer for Minimally Invasive Spinal Surgery

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Solution Overview

Problem

Conventional rod reducers are bulky, require two-handed operation, and are not compatible with minimally invasive surgery, often applying excessive force, which can lead to complications during spinal deformity surgeries, especially when L5-S1 implants are close together or touching.

Innovation Solution

A cam coupling rod reducer with an inner tube, lever cam, and outer extension tube featuring positional markings and prongs, allowing for precise control and tactile feedback to safely reduce spondylothesis by guiding the spinal rod into a pedicle screw assembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional rod reducers are used, then rod reduction function is achieved, but the device becomes bulky and not minimally invasive surgery compatible

Engineering Contradiction:

Improveminimally invasive surgery compatibilityVSAvoiddevice size

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The rod reducer employs a telescopic design where the inner tube can slide within the outer tube, allowing the device to compact into a smaller configuration for minimally invasive access while extending to full operational length when needed. This nested structure enables the device to meet both size constraints for MIS and functional requirements for rod reduction.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Ease of operation

If conventional rod reducers are used, then rod reduction function is achieved, but two-handed operation is required

Engineering Contradiction:

Improveone-handed operation capabilityVSAvoidoperation complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The device integrates multiple functions into a single unified structure: the lever cam mechanism combines activation, rod engagement, and reduction control in one component that can be operated with a single hand. The telescopic tubes are integrated with the cam mechanism, eliminating the need for separate operations that would require two hands.

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If conventional rod reducers are used, then rod reduction function is achieved, but too much space is required in medial or lateral direction interfering with facet or transverse process

Engineering Contradiction:

Improvesurgical access compatibilityVSAvoidlateral space requirement

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The telescopic inner and outer tubes allow the device to collapse to a minimal lateral profile when not in use, enabling access through smaller incisions and navigation around anatomical structures like the facet and transverse process. The device only occupies its full lateral area when actively engaged in rod reduction.

Inventive Principle:

Principle #7Nested doll (Nesting)

4Ease of operation

If conventional rod reducers with threaded mechanism are used, then rod reduction function is achieved, but too much force is applied without tactile sensation

Engineering Contradiction:

Improvetactile feedbackVSAvoidforce control

Core Design Contradiction:

Ease of operationVSForce

Solution Approach 1:

The cam mechanism provides direct tactile feedback to the operator as it engages with the rod and progresses through the reduction motion. The operator can feel the engagement points and resistance changes, allowing for precise control of the reduction force and immediate detection of when the rod is properly positioned, eliminating the risk of excessive force application.

Inventive Principle:

Principle #23Feedback

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

Enables minimally invasive, one-handed operation with reduced risk of bone anchor dislodgment, facilitating precise rod reduction and alleviating pressure on nerves during spinal deformity surgeries.

Implementation Method 1

Methodology Applied

Scientific EffectCam mechanism: Cam

Data Source

PatentUS7608081B2Rod reducer

Publication Date: 2009.10.27 CUSTOM SPINE ACQUISITION INC

AI summary

A cam coupling rod reducer and method of operation comprises an inner tube comprising a first end having a hole and a second end having a plurality of prongs extending therefrom. The rod reducer further includes a lever cam connected to the first end, wherein the lever cam comprises a base and a pair of semicircular arms extending from the base, wherein each of the arms comprise a hole configured to align with the hole of the first end of the inner tube. The rod reducer also includes an outer extension tube connected to the inner tube, wherein the outer extension tube comprises positional markings on the body of the outer extension tube; a top end having a concave opening; and a bottom end comprising an opening configured to permit the prongs of the inner tube to extend therethrough; and a pair of pegs extending from the bottom end.