Poly-axial fixation posts for orthopedic compression maintenance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Orthopedic screws often lose compression over time, limiting their ability to provide structural support and maintain implant stability in bone attachment.
Innovation Solution
A fixation post system with a quasi-spherical head and porous metal sleeve that creates initial compression between an orthopedic device and bone, utilizing a textured surface for secure locking and bone ingrowth to maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If screws are used to attach an implant to bone, then structural support is provided, but compression between the implant and bone is lost over time
Solution Approach 1:
The fixation post incorporates a porous metal sleeve that allows bone ingrowth into its structure. This biological integration mechanism maintains compression between the baseplate and bone over time, resolving the reliability issue where conventional screws lose compression. The porous material enables osteointegration while preserving the structural support function.
2Reliability
If a textured outer surface is used on the quasi-spherical head, then secure locking to the baseplate is achieved, but manufacturing complexity increases
Solution Approach 1:
The textured outer surface on the quasi-spherical head is created by modifying surface parameters (roughness, pattern density, depth) rather than changing the fundamental spherical geometry. This allows the head to maintain its simple form for easy manufacturing while achieving enhanced locking stability through controlled surface texture variations that increase friction and mechanical interlocking with the baseplate.
3Reliability
If a porous metal sleeve is used to promote bone ingrowth, then compression maintenance is improved, but device complexity increases
Solution Approach 1:
The porous metal sleeve is nested within the fixation post structure, surrounding the central shaft. This nested configuration allows the porous sleeve to perform its bone-ingrowth function independently while being integrated into the overall fixation post assembly. The sleeve's porous structure promotes osteointegration and compression maintenance without requiring a completely redesign of the fixation post, thus limiting the increase in device complexity.
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 system effectively maintains initial compression and promotes bone integration, enhancing the stability and longevity of orthopedic device attachment.
Implementation Method 1
the porous metal sleeve is configured to receive bone ingrowth into the porous metal sleeve for maintaining said initial compression between the baseplate and the glenoid
Implementation Method 2
the textured outer surface of the quasi-spherical head contacts at least the first wall of the first fastener bore so as to removeably lock the quasi-spherical head to the baseplate
Data Source
AI summary
This disclosure includes apparatus and methods to attach an orthopedic device to a bone. The method can comprise locating a baseplate on a glenoid of a patient, the base plate including at least a first fastener bore, creating a first post hole in the glenoid for locating a first fixation post, the first fixation post including a quasi-spherical head and a porous metal sleeve, and driving the first fixation post through the first fastener bore and into the first post hole. The porous metal sleeve can engage the first post hole and the quasi-spherical head can contact at least the first wall of the first fastener bore to removeably lock the quasi-spherical head to the baseplate. Driving the first fixation post can create an initial compression between the baseplate and the glenoid. The porous metal sleeve can receive bone ingrowth to maintain the initial compression.