Unicondylar Balancer With Force-Locking Jaw Adjustment
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Solution Overview
Problem
Existing knee surgery distraction devices fail to balance distraction height with force, and do not allow precise measurement of the distance and force between the femoral condyle and tibial plateau, which is crucial for accurate prosthetic implant placement.
Innovation Solution
A unicondylar balancer with a first and second jaw for contacting the femoral condyle and tibial plateau, respectively, featuring a threaded collar and rod adjustment mechanism, a biasing element to apply distraction force, and a manually operable locking mechanism to stabilize the jaws at a predetermined force for precise distance and force measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a torque handle design is used to apply distraction force, then force application is simplified, but the ability to balance distraction height with force is lost
Solution Approach 1:
The device transitions from a static torque handle to a dynamic spring-loaded system where the distraction force can be adjusted by compressing the spring to different degrees, allowing the user to balance distraction height with force dynamically during the procedure
Solution Approach 2:
The spring mechanism allows changing the force parameter by varying the compression amount, enabling the user to apply different levels of distraction force while maintaining control over the distraction height through the adjustable mechanism
2Measurement precision
If a sprung platform is used to assess distraction force, then force measurement capability is improved, but the device complexity increases
Solution Approach 1:
The spring mechanism serves dual purposes: it both applies the distraction force and provides the measurement capability through its compression degree, eliminating the need for separate complex measurement systems
Solution Approach 2:
The spring component performs multiple functions simultaneously - it acts as both the force application mechanism and the force measurement indicator, reducing overall device complexity while maintaining measurement precision
3Device complexity
If no locking mechanism is used, then the adjustment mechanism remains simple, but the stability of the jaws at predetermined force is compromised
Solution Approach 1:
The locking mechanism is designed as a separate, independent component that can be added to the adjustment mechanism without fundamentally redesigning the entire system, maintaining simplicity while adding necessary stability
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 convenient and accurate measurement of distance and force between the femoral condyle and tibial plateau, allowing for precise determination of the resection plane for prosthetic implant placement, reducing measurement errors and simplifying the surgical process.
Implementation Method 1
a biasing element to apply a distraction force
Implementation Method 2
an adjustment mechanism comprising a threaded collar captured in a slot in the second body portion, and a threaded rod received through the threaded collar
Data Source
AI summary
A unicondylar balancer (10) for knee surgery and a method of knee surgery. The balancer includes a first body portion (6) including a first jaw (2). The balancer also includes a second body portion (8) slideably attached to the first body portion, the second body portion comprising second jaw (4). The balancer further includes an adjustment mechanism selectively to distance the first jaw from the second jaw. The adjustment mechanism includes a threaded collar (20) captured in a slot (26) in the second body portion, and a threaded rod (30). The first body portion is coupled to the threaded rod via a biasing element (50), which biases the first jaw away from the second jaw. The balancer further includes a manually operable locking mechanism (140), to lock the first body portion with respect to the second body portion.