Compact Spindle Drive for Growing Prosthesis Lengthening
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Solution Overview
Problem
Existing growing prostheses with planetary roller drives are too large in diameter and length, making them unsuitable for children and adolescents, as they require excessive bone removal for implantation and have stability issues due to predefined lengths.
Innovation Solution
A modular growing prosthesis with a spindle element drive and a stem-anchoring element of reduced length and diameter, featuring a modular design with a spindle element and drive that can be easily removed, allowing for postoperative lengthening and adapted to individual anatomical needs, using implant-grade materials for stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If planetary roller drives are used in growing prostheses, then the prosthesis can achieve reliable lengthening function, but the prosthesis diameter and length become too large for children and adolescents
Solution Approach 1:
The invention extracts the drive mechanism from the traditional planetary roller system and replaces it with a compact spindle element system. The spindle element with integrated drive unit is inserted into the medullary cavity through a minimally invasive approach, eliminating the need for large diameter prosthesis components while maintaining the lengthening function.
Solution Approach 2:
The invention replaces the complex mechanical planetary roller drive with a simpler spindle-based mechanical system. The spindle element converts rotational motion from the drive unit into linear motion for lengthening, achieving the same function with significantly reduced component size and simpler mechanics suitable for pediatric applications.
2Device complexity
If long predefined length prosthesis are used, then the drive unit can be adequately housed, but excessive healthy bone must be removed for implantation
Solution Approach 1:
The invention nests the drive unit within the spindle element, which itself is inserted into the existing medullary cavity. This nested arrangement allows the drive mechanism to be housed within the bone cavity itself rather than requiring external housing, minimizing the need to remove healthy bone while accommodating the drive unit.
Solution Approach 2:
The prosthesis is designed with dynamic adjustability through the spindle element system, allowing the length to be modified post-implantation. This eliminates the need for a long predefined length, as the prosthesis can be adjusted to the required length after implantation, thereby preserving healthy bone.
3Ease of manufacture
If intramedullary distraction pins are used for bone lengthening, then the procedure is simple, but the pins lack sufficient stability for permanent implantation
Solution Approach 1:
The invention merges the temporary distraction pin function with the permanent prosthesis components. The spindle element is designed to serve both as the distraction mechanism during bone growth and as a permanent stabilizing component, eliminating the need for separate temporary pins and subsequent replacement procedures.
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 compact design reduces bone removal and enhances stability, enabling effective length adjustment and easier implantation in young patients, while allowing for delayed drive installation, suitable for children and adolescents with smaller bones and adaptable for various medical conditions.
Implementation Method 1
Spindle roller systems are mostly used as the electric drive. A drive unit of this kind is disclosed in EP 0 776 432 B1. The device converts a rotary movement into an axial movement using planetary rollers
Data Source
AI summary
A growing prosthesis comprising a joint replacement part, a prosthesis stem, a stem-anchoring element, and an element with corresponding drive provided for the lengthening of the growing prosthesis. The element provided for the lengthening of the growing prosthesis is a spindle element arranged in the stem-anchoring element.