Knee Tensor With Nested Paddles for Soft Tissue Balancing
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Solution Overview
Problem
Current joint replacement procedures face challenges in achieving proper soft tissue balancing and knee alignment due to the limitations of existing surgical tools, which often require dislocation of the patella, leading to potential soft tissue damage and incomplete assessment of joint balance.
Innovation Solution
The development of a tensor apparatus with a tibial paddle that can lie within a femoral paddle, along with a load sensor and a housing with a distractor, allows for soft tissue balancing and proper knee alignment without everting the patella, enabling accurate measurement of knee loads and adjustments for optimal joint biomechanics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a tensor with large paddles is used to withstand substantial loading during flexion and extension, then the load bearing capability is improved, but the tensor cannot be easily located within the tight joint space
Solution Approach 1:
The tibial paddle is designed to nest within the femoral paddle when the knee is in extension, creating a compact configuration that fits within the tight joint space. This nesting arrangement allows the tensor to achieve the necessary structural strength for load bearing while maintaining a compact profile for easy insertion and manipulation during surgery.
2Ease of operation
If long linking members are used to place the tensioner in anterior-to-posterior direction without everting the patella, then the ease of operation is improved, but the load bearing capability is reduced due to cantilever loading
Solution Approach 1:
The tensor is designed with offset paddles that are positioned to contact the femoral and tibial bones at specific locations before distraction occurs. This preliminary positioning allows the tensor to be placed in the anterior-to-posterior direction without requiring patellar eversion, while the offset design minimizes cantilever loading by pre-establishing load transmission paths.
3Ease of operation
If offset paddles are used to place the tensioner in anterior-to-posterior direction, then the ease of operation is improved, but the load bearing capability is reduced due to torsion loading
Solution Approach 1:
The tensor employs asymmetric offset paddles with specific dimensional relationships between the offset distances and paddle dimensions. The asymmetric design allows the tensor to be placed without patellar eversion while the carefully controlled offset dimensions minimize torsion loading by optimizing the load transmission geometry relative to the knee joint axes.
4Measurement precision
If load sensors are placed in contact with the paddles to provide real-time ligament tension measurement, then the measurement precision is improved, but the size of the tensor paddles increases making insertion difficult
Solution Approach 1:
The load sensor is integrated into the tensor structure by placing it in contact with the offset paddles, combining the measurement function with the existing tensor components. This merging approach allows real-time ligament tension measurement without requiring separate measurement devices, while the sensor placement utilizes the existing paddle geometry to minimize additional size increase.
Data Source
AI summary
Disclosed herein are apparatuses and methods for performing joint balancing procedures. The apparatus may have femoral paddle and a tibial paddle attached to a housing. The housing may include a distraction mechanism to vary the space between the femoral paddle and the tibial paddle. The tibial paddle may lie entirely within the femoral paddle in a closed position. A load sensor may be placed in the femoral paddle to measure ligament tension. The apparatus may be inserted into a knee joint and positioned to remain within the knee joint during flexion and extension of the knee without everting a patella.