Adjustable Spinal Implant Assembly with Pivotable Cradle

Solution Overview

Problem

Polyaxial and multi-axial screws used in spinal fixation systems can be difficult to control, leading to undesirable movement during vertebral or pelvic body rotation, as they allow pivoting in all directions, which is not always desirable.

Innovation Solution

An adjustable implant assembly with a bone anchor and a pivotable cradle within the proximal head portion allows controlled angulation of a spinal fixation element relative to the screw body, enabling movement in selected directions and providing a locking mechanism to secure the desired orientation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If polyaxial and multi-axial screws are used to allow pivoting in all directions, then adaptability for positioning bone anchors is improved, but control during vertebral or pelvic body rotation deteriorates

Engineering Contradiction:

Improvepositioning flexibilityVSAvoidcontrol

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The screw is divided into functionally independent segments: a head portion for receiving the spinal fixation element and a shank portion for bone engagement. The polyaxial joint connects these segments, allowing independent optimization of each portion's function while maintaining overall system performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The screw transitions from a static, fixed-orientation design to a dynamic, adjustable-orientation design. The polyaxial joint enables the shank portion to pivot relative to the head portion, allowing the screw to adapt its orientation dynamically during insertion and fixation while maintaining controlled stability once positioned.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If the threaded shank is rigidly connected to the head portion in fixed pedicle screws, then control and stability are improved, but adaptability for different vertebral positions deteriorates

Engineering Contradiction:

ImprovecontrolVSAvoidpositioning flexibility

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The screw transitions from a static, fixed-orientation design to a dynamic, adjustable-orientation design. The polyaxial joint enables the shank portion to pivot relative to the head portion, allowing the screw to adapt its orientation dynamically during insertion and fixation while maintaining controlled stability once positioned.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The screw's orientation parameters can be changed during the fixation process. The polyaxial joint allows adjustment of the shank's angular position relative to the head, enabling the surgeon to optimize the screw's orientation to match the specific anatomical requirements of different vertebral positions before locking the configuration.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If polyaxial screws allow pivoting in all directions, then interference between bone anchors on adjacent vertebrae is reduced, but unwanted movement of the screw shank deteriorates

Engineering Contradiction:

Improvepositioning flexibilityVSAvoidfixation stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The screw transitions from a static, fixed-orientation design to a dynamic, adjustable-orientation design. The polyaxial joint enables the shank portion to pivot relative to the head portion, allowing the screw to adapt its orientation dynamically during insertion and fixation while maintaining controlled stability once positioned.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The desired orientation and position of the screw shank relative to the head portion is established during the insertion and positioning phase, before final locking. This preliminary positioning allows the surgeon to optimize the configuration to avoid interference with adjacent vertebrae, and subsequent locking preserves this optimized configuration, preventing unwanted movement.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11992245B2Adjustable implant assembly

Publication Date: 2024.05.28 DEPUY SYNTHES PROD INC

AI summary

An implant assembly includes a screw body, including anchor portion and proximal head portion, and a cradle movably mounted in the screw body to allow for controlled angulation between a spinal connection element disposed in the cradle and the screw body. The cradle is pivotable in one or more selected directions about one or more axes relative to the screw body. The cradle may be generally, substantially spherical in shape and allow for unrestricted movement in one or more directions around one or more axis.