Negative Cast for Brace with Corrective Forces to Control PLC Deficiencies
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Solution Overview
Problem
Traditional methods for producing orthoses, such as knee orthoses (KO) and knee ankle foot orthoses (KAFO), fail to provide tri-planar support for posterolateral corner (PLC) deficiencies, which are essential for controlling knee movement in all three planes, leading to inadequate alignment and increased pain due to unaddressed rotational deformities.
Innovation Solution
A method involving specific positioning and application of corrective forces during the casting process, where the knee is bent between 15° and 50°, then flexed to 70°-90°, and extended while applying valgus pressure and external tibial rotation to achieve tri-planar support, allowing the casting material to dry before removal, resulting in a negative cast that captures these corrective forces for fabricating a custom orthosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional casting methods are used with the knee in full extension without corrective forces, then the casting process is simple and quick, but the knee alignment is inadequate and rotational deformities are not addressed
Solution Approach 1:
The patent applies corrective forces (valgus pressure and external rotation) to the knee during the casting process before the orthosis is fabricated. This preliminary correction of alignment during casting ensures the positive cast captures the corrected alignment, which is then used to manufacture the orthosis with built-in corrective capabilities, resolving the contradiction between alignment precision and process complexity
Solution Approach 2:
The patent introduces a third plane of control (transverse plane rotation) in addition to the traditional two planes (coronal and sagittal). By applying external rotation force during casting, the method achieves tri-planar support, improving knee alignment precision in all three planes simultaneously without significantly increasing process complexity
2Reliability
If traditional two-plane support is provided, then the casting process is straightforward, but posterolateral corner deficiencies are not adequately controlled
Solution Approach 1:
The patent applies corrective forces during the casting process to pre-establish the desired tri-planar alignment. By positioning the knee in correct alignment (with external rotation and valgus pressure) before fabricating the orthosis, the positive cast captures this corrected position, ensuring the final product provides reliable posterolateral corner control without requiring complex post-casting modifications
Solution Approach 2:
The patent transitions from traditional two-plane support (coronal and sagittal) to tri-planar support by adding control in the transverse plane through external rotation. This dimensional expansion ensures adequate control of posterolateral corner deficiencies by addressing rotational deformities that were previously unaddressed, improving reliability without excessive complexity increase
3Manufacturing precision
If corrective forces are applied during casting, then tri-planar support is achieved, but the casting procedure becomes more time-consuming and complex
Solution Approach 1:
The patent applies corrective forces during the initial casting process rather than requiring separate correction steps later. By establishing the corrected tri-planar alignment during casting itself, the method achieves high alignment accuracy while avoiding additional time-consuming post-casting modification procedures, as the correction is integrated into the single casting operation
Solution Approach 2:
The patent combines the alignment correction process with the casting process into a single integrated procedure. Instead of performing casting and then separately applying corrective forces or modifications, the method merges these operations by applying corrective forces during casting, achieving tri-planar alignment accuracy while reducing total procedure time
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
This method effectively controls posterolateral movement, reduces pain, and prevents deterioration of the knee joint by providing tri-planar support, aligning the knee in a more natural position, thereby reducing medial compartment loading and progression of osteoarthritis.
Implementation Method 1
allowing the casting material to dry
Data Source
AI summary
A casting method for a brace having corrective forces is disclosed. The foot is externally rotated during casting and corrective forces are applied at the lateral knee and anteromedial ankle. With the knee flexed at between about 70° to 90°, the cast is fully extended, which places the knee in a position which will reduce the pressures on the medial knee. This is the position desired during the casting process with the knee flexed and then held while extending the knee. The result is control of the posterior lateral rotation, therefore controlling the posterior subluxation of the tibial plateau to achieve the motion and alignment that the screw home motion produces.