Lateral Approach Bicondylar Knee Prosthesis Fixation
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Solution Overview
Problem
Conventional knee replacement surgeries using bicondylar knee prostheses face issues with high failure rates due to loosening and dislocation, especially with unicondylar implants, and cause extensive soft tissue disruption and scarring through invasive anterior approaches, damaging anatomical structures like the patellar tendon and cruciate ligaments.
Innovation Solution
A mini bicondylar knee prosthesis designed for insertion through a direct lateral approach using an electromagnetic bone chipper device guided by surgical polygonal cutting blocks with inverted T slots, allowing precise bone resection without disrupting the extensor mechanism or damaging the quadriceps tendon, and incorporating a polyethylene tibial insert locked by a recess and tang mechanism for secure fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional anterior approach is used for knee replacement, then the surgeon can access the femoral condyles, but extensive soft tissue disruption and damage to patellar tendon and cruciate ligaments occurs
Solution Approach 1:
The patent applies the inversion principle by reversing the conventional surgical approach. Instead of accessing the femoral condyles through the anterior approach (as done in conventional knee replacement), the invention uses a posterior approach. This allows the surgeon to insert the prosthesis through the posterior aspect of the knee joint, thereby avoiding disruption of the extensor mechanism, quadriceps tendon, and cruciate ligaments while still achieving proper placement of the bicondylar prosthesis
Solution Approach 2:
The patent applies the dimensionality change principle by transitioning from the conventional anterior (front-to-back) approach to a posterior (back-to-front) approach. This dimensional reversal enables access to the same anatomical structures through a different spatial pathway, allowing implantation without compromising the integrity of the patellar tendon and cruciate ligaments
2Device complexity
If unicondylar implant is used for knee resurfacing, then the surgical procedure is simpler, but high failure rate occurs due to loosening and dislocation from poor weight distribution
Solution Approach 1:
The patent applies the merging principle by combining the coverage of both medial and lateral femoral condyles into a single bicondylar prosthesis design. This unified approach distributes weight-bearing forces across both condyles simultaneously, preventing the stress concentration and poor weight distribution that lead to loosening and dislocation in unicondylar implants, while maintaining surgical simplicity through a single implant insertion procedure
3Reliability
If bone cement is used for implant fixation, then secure fixation is achieved, but the implant cannot be removed or revised easily
Solution Approach 1:
The patent applies the segmentation principle by dividing the fixation system into modular components. The bicondylar prosthesis incorporates distinct fixation elements such as press-fit surfaces, porous coatings for bone ingrowth, and potentially modular cemented or uncemented fixation options. This segmented approach allows selection of appropriate fixation methods (cemented or uncemented) and enables easier removal and revision compared to monolithic cemented fixation, while still achieving secure initial and long-term fixation
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
The solution enables precise and minimally invasive bicondylar knee resurfacing with reduced risk of postoperative pain and scarring, improved accuracy in bone resection, and secure implant fixation, overcoming the limitations of conventional methods by maintaining the integrity of the quadriceps tendon and cruciate ligaments.
Implementation Method 1
using an electromagnetic bone chipper device guided by surgical polygonal cutting blocks
Data Source
AI summary
A bicondylar knee implants with improved fixation means for resurfacing only the weight-bearing surface of the femoral medial and lateral condyles, while preserving the cruciate ligaments and avoids displacing the patella. The inventive device includes metallic convex articular surfaces for resurfacing the medial and lateral femoral condyles, and concave multifacial non-articular surfaces to be affixed to the resected distal surfaces of the femur. The prosthesis provides claws situated at the anterior and posterior ends of the medial and lateral metallic condyles, which will firmly attach the implant against the resected femoral condyle. The prosthesis is designed to be implanted through a direct lateral approach and does not resurface the femoropatellar joint. Furthermore, a minirobot or electromechanical actuator is used to perform the femoral and tibial bone cuts using electromagnetic bone chipper.