Bicondylar Knee Prosthesis Lateral Insertion Design

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Solution Overview

Problem

Conventional knee resurfacing prostheses cause extensive soft tissue disruption and irreparable scarring due to their large size and the need for anterior surgical approaches, which violate the extensor mechanism and damage the quadriceps tendon, making them unsuitable for bicondylar knee resurfacing through a limited lateral approach.

Innovation Solution

A bicondylar knee resurfacing prosthesis with a thin metallic femoral component and a polyethylene tibial insert, featuring a dovetail fixation mechanism, designed for insertion through a limited lateral approach without disrupting the extensor mechanism or damaging the quadriceps tendon, utilizing a mini incision and computerized navigation for precise placement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional anterior surgical approach is used for knee resurfacing prosthesis insertion, then the prosthesis can be implanted, but extensive soft tissue disruption and irreparable scarring occur due to violation of the extensor mechanism and damage to the quadriceps tendon

Engineering Contradiction:

Improveprosthesis implantation successVSAvoidsoft tissue disruption and quadriceps tendon damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies the inversion principle by reversing the conventional surgical approach. Instead of using the traditional anterior approach that violates the extensor mechanism, the invention uses a lateral approach that avoids the quadriceps tendon and extensor mechanism entirely. The prosthesis is inserted through a lateral incision without dislocating the patella or disrupting the quadriceps mechanism, thereby eliminating soft tissue disruption and scarring while still achieving successful prosthesis implantation.

Inventive Principle:

Principle #13The other way round (Inversion)

2Area of stationary object

If conventional large-sized femoral component is used, then complete knee coverage is achieved, but the prosthesis cannot be inserted through a limited lateral approach

Engineering Contradiction:

Improveknee joint coverage areaVSAvoidinsertion through limited lateral approach

Core Design Contradiction:

Area of stationary objectVSEase of operation

Solution Approach 1:

The patent applies segmentation by dividing the femoral component into two separate condylar components (medial and lateral condyles) that can be inserted independently through the lateral approach. Each condylar component is designed to fit its respective condyle, allowing complete bicondylar coverage while enabling insertion through a limited lateral incision without requiring a single large monolithic component.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from the conventional anterior approach (one-dimensional access) to a lateral approach (introducing a new dimensional access route). By approaching the knee joint laterally rather than anteriorly, the surgery can access both condyles through a limited incision without violating the extensor mechanism, effectively using a different spatial dimension to solve the access problem.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of operation

If conventional anterior approach with patellar dislocation is used, then both condyles can be accessed, but the patellar tendon insertion is weakened causing postoperative pain

Engineering Contradiction:

Improveaccess to both condylesVSAvoidpatellar tendon weakening and postoperative pain

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the problematic step of patellar dislocation from the surgical procedure. By using a lateral approach, the surgery can access and resurface both condyles without ever dislocating or manipulating the patella. This eliminates the harmful effect of weakening the patellar tendon insertion and prevents postoperative pain associated with patellar manipulation while still achieving complete condylar access.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8114164B2Bicondylar resurfacing prosthesis and method for insertion through direct lateral approach

Publication Date: 2012.02.14 TERMANINI ZAFER

AI summary

A bicondylar implantable prosthesis resurfaces only the weight bearing portion of the patient's femur. The prosthesis includes a thin shell convexly curved outer articular surface including a medial condyle, a lateral condyle, and an intercondylar bridge, and a concave inner surface of the prosthesis that has at least one transverse ridge extending across the width of the prosthesis. When the prosthesis is implanted on the weight bearing portion of the femur, the entire outer surface of the curved articular surface is sized to resurface substantially only the weight bearing portion and no portion of the patello-femoral joint of the knee. The prosthesis is configured to be implantable by a lateral insertion through a direct lateral approach to a retropatellar region of the patient's knee joint, during which insertion the at least one transverse ridge guides the prosthesis along a laterally resected surface of the femur.