Stem Vibrator for Hip Replacement Insertion
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Solution Overview
Problem
Current hip replacement surgeries rely heavily on manual techniques and tactile feedback, which can be subjective and imprecise, leading to variability in the insertion and fitting of prosthetic stems into the femoral canal.
Innovation Solution
The STEM-FIT apparatus utilizes a stem vibrator and driver to generate vibrations and apply force, controlled by a controller, to precisely insert and extract prosthetic stems into the femoral canal, with optional torquing and attitude control systems for accurate alignment and a sensor system for real-time feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manual techniques and tactile feedback are used for stem insertion, then the surgeon can perform the procedure with simple equipment, but the precision and consistency of stem insertion deteriorates due to subjectivity and variability
Solution Approach 1:
The patent applies mechanical vibration through a stem vibrator that generates vibrations in the prosthetic stem during insertion into the femoral canal. The vibrator is coupled to the stem and excited to vibrate at specific frequencies, reducing friction and facilitating precise, consistent insertion while eliminating reliance on subjective tactile feedback. The vibration mechanism directly addresses the precision problem by providing objective, controllable insertion forces.
Solution Approach 2:
The patent implements feedback through sensors that detect vibrations, forces, and insertion depth, with this information fed to a controller that adjusts vibration parameters and insertion forces in real-time. This closed-loop feedback system replaces subjective surgeon judgment with objective measurements, ensuring consistent and precise stem insertion while managing the complexity through automated control algorithms.
2Ease of operation
If manual tapping with mallet and impactor is used, then the equipment remains simple and easy to operate, but the control over insertion force and depth deteriorates leading to variability
Solution Approach 1:
The system employs self-service through automated control where the controller autonomously regulates vibration amplitude, frequency, and insertion forces based on sensor feedback. The apparatus serves itself by automatically adjusting parameters to maintain optimal insertion conditions, reducing the need for complex manual coordination while improving depth and force control consistency.
Solution Approach 2:
The patent substitutes manual mechanical tapping with an automated system combining controlled vibration and programmable force application. The stem vibrator and controlled driver replace the mallet and impactor, transforming uncontrolled manual strikes into precisely regulated mechanical forces and vibrations, thereby improving insertion control while maintaining operational simplicity through automation.
3Manufacturing precision
If vibrations are applied to the stem during insertion, then the precision of stem fitting improves, but the complexity of the apparatus increases due to additional vibration generation and control systems
Solution Approach 1:
The stem vibrator serves multiple functions: it generates vibrations to reduce friction during insertion, facilitates torque transmission for rotational alignment, and provides vibration signals for sensor-based feedback control. This multi-functionality reduces overall system complexity by consolidating vibration generation and control into a single versatile component rather than requiring separate systems for each function.
Solution Approach 2:
The patent merges the vibration generation system with the insertion control system, where the same vibrator that facilitates stem insertion also provides the vibration signals detected by sensors for feedback control. This consolidation integrates multiple functions into unified subsystems, managing complexity through functional integration rather than separate independent systems.
4Manufacturing precision
If torquing system is used to rotate the stem for alignment, then the accuracy of azimuthal angle positioning improves, but the device complexity increases due to additional torque transmission mechanisms
Solution Approach 1:
The torquing system utilizes mechanical vibration transmitted through the stem vibrator to facilitate rotational movement of the prosthetic stem to the desired azimuthal angle. The vibrations reduce friction and enable precise angular positioning through controlled oscillatory motion, improving alignment accuracy while avoiding the need for complex direct-drive torque mechanisms. The same vibration mechanism serves both insertion and rotational alignment functions.
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
Enhances the precision and consistency of stem insertion and alignment, reducing the reliance on manual dexterity and improving the accuracy of hip replacement surgeries.
Implementation Method 1
a vibrator configured to be coupled to a stem and be excited to generate vibrations in the stem during a joint replacement operation to insert the stem into and/or to extract the stem out from a bone canal
Implementation Method 2
the torquing system comprises at least one piezoelectric vibrator, hereinafter referred to as a torquing vibrator, and a torque transmission that couples vibrations of the torquing vibrator to apply a torque that rotates the stem
Implementation Method 3
at least one sensor that generates and transmits sensor signals to the controller responsive to amplitudes and frequencies of vibrations excited in the stem by vibrations of the stem vibrator
Data Source
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AI summary
Apparatus for performing a joint replacement procedure comprising: a vibrator configured to be coupled to a stem and be excited to generate vibrations in the stem during a joint replacement operation to insert the stem into and/or to extract the stem out from a bone canal; a driver operable to apply continuous force to the stem; and a controller operable to control the vibrator and the driver to respectively generate vibrations in and apply continuous force to the stem that cooperate to insert the stem into or extract the stem out from the canal.