Bladder-Driven Linear Actuator for Predictable Joint Manipulation
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Solution Overview
Problem
Current orthotic devices for treating arthrofibrosis, such as vigorous physical therapy, surgical manipulation, and specialized splints, are ineffective in consistently and predictably restoring full range of motion in joints due to unpredictable load variations and inability to apply high, instantaneous forces.
Innovation Solution
A bladder-driven linear actuator system comprising an inflatable bladder within a cylinder, which upon inflation, moves a piston to apply a consistent and adjustable force to a joint through a linkage, allowing for precise joint manipulation and treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If specialized splints (Dynasplint, Joint Active System) are used to apply loading to the joint, then the joint can be stretched, but the load is unpredictable and varies during the stretching process due to energy storage within the splint structure
Solution Approach 1:
The patent removes the energy-storing structural complexity from the splint design by using a simple, rigid bar that does not deform or store energy during stretching. The loading mechanism is extracted from the splint structure itself and placed in a separate, controlled pneumatic actuator system, ensuring that all loading is applied through the bar rather than through elastic deformation of the splint material.
Solution Approach 2:
The patent replaces complex mechanical spring-loaded or elastic splint structures with a pneumatic actuation system. The pneumatic pump provides controlled, predictable loading through a rigid bar mechanism, eliminating the unpredictable energy storage and release characteristics of traditional mechanical splints.
2Length of moving object
If vigorous physical therapy or surgical manipulation is used to gain range of motion, then the joint can be stretched, but there is high failure rate due to peri-articular bleeding and progression of arthrofibrosis
Solution Approach 1:
The patent incorporates a feedback mechanism where a sensor detects the position of the bar relative to the joint, and this information is fed back to a microprocessor that controls the pneumatic pump. This closed-loop control ensures that the bar is pulled only to the precise position needed for stretching, preventing excessive forces that could cause bleeding or worsen arthrofibrosis.
Solution Approach 2:
The patent uses controlled pneumatic pressure as an adjustable parameter to precisely control the stretching force applied to the joint. By regulating the pneumatic pressure and the resulting bar displacement, the system can apply optimal stretching forces without the chaotic, high-impact forces of manual manipulation or surgery.
3Duration of action of moving object
If continuous passive motion machines are used, then the joint can be moved, but they are not effective because they spend most time in the middle range of motion and not focused on stretching at end range
Solution Approach 1:
The patent employs periodic, controlled cycles of bar displacement to the end-range position followed by release. The bar is pulled to the precise end-range position, held there long enough to achieve stretching, then released. This periodic action at end-range positions is far more effective than continuous motion through the middle range, as it applies concentrated stretching force where it is most needed.
4Force
If serial casting splints are used, then the joint can be stretched, but they are not removable by the patient and have limited adjustability
Solution Approach 1:
The patent creates a dynamic, adjustable system where the bar length and pneumatic pressure can be modified to adapt to different joint sizes, stiffness levels, and stretching requirements. The bar can be adjusted in length to accommodate various joint geometries, and the pneumatic pressure can be tuned to provide appropriate stretching forces for different patients and conditions.
Data Source
AI summary
An apparatus for manipulating the joint of a patient is provided. The apparatus comprises an actuator and a linkage. The actuator itself comprises: 1) a cylinder portion defining an interior cavity; and 2) an inflatable bladder member at least partially inside the cavity of the cylinder portion. The linkage is operatively positioned intermediate the actuator and the joint of the patient, the linkage configured to be activated and to flex the joint upon inflation of the bladder. A piston portion may also be provided and configured to move relative to cylinder portion within the cavity in response to inflation of the bladder. A patient connection and manipulation device may also be provided within the apparatus and configured to be attached relative to the patient, attached intermediate the linkage and the patient, and configured to at least partially assist with treatment upon activation of the linkage.