Tibial Base Pin-and-Lug Mechanism for Insert Stability
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Solution Overview
Problem
Existing prosthetic tibial bases and inserts experience clearance issues along the anteroposterior direction, leading to friction and premature wear, which can cause osteolysis due to debris generation.
Innovation Solution
A prosthetic tibial base with specific geometric features such as posterior and anterior pins, lugs, and a smooth plate surface, designed to securely attach the tibial insert without clearance, utilizing materials like cobalt-chrome alloy and ultra-high-molecular-weight polyethylene to minimize friction and ensure a tight fit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tibial insert is attached onto a conventional tibial base using pins at lateral and medial edges, then the assembly is simple to manufacture, but clearance is generated along the anteroposterior direction causing friction and wear
Solution Approach 1:
The platen is segmented into multiple functional zones: a smooth plate surface for insert contact, posterior pins with flat sections for anteroposterior positioning, and lateral/medial lugs for securing the insert. This segmentation allows each zone to perform its specific function optimally while collectively eliminating clearance issues
Solution Approach 2:
The invention adds dimensional constraints by introducing posterior pins that extend vertically above the plate surface, creating a third-dimensional constraint in the anteroposterior direction. This prevents the insert from moving forward or backward, eliminating clearance without complicating the overall assembly process
2Reliability
If the plate surface is made smooth to reduce friction, then wear is minimized, but clearance may increase affecting stability
Solution Approach 1:
The plate surface is given a specifically smooth local quality with reduced roughness to minimize friction and wear between the plate and insert contact surfaces. Meanwhile, the posterior pins and lugs maintain their structural integrity and positioning function, ensuring stability is not compromised by the smooth surface treatment
3Reliability
If pins are added to eliminate clearance, then attachment stability improves, but manufacturing complexity increases
Solution Approach 1:
The posterior pins, lateral lugs, and medial lugs are merged into a single integrated platen structure. This allows all clearance-elimination features to be manufactured as one piece, reducing assembly steps and overall manufacturing complexity despite the added functional complexity of the pins themselves
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 effectively prevents clearance and premature wear of the prosthetic tibial insert, ensuring a secure attachment and reducing the risk of osteolysis by using a press-fit mechanism and low-friction materials.
Implementation Method 1
The wear caused by this friction risks generating small debris of tibial insert, which may cause osteolysis
Implementation Method 2
the distance separating the posterior flat section from the anterior flat section, measured along an anteroposterior direction, is determined in such a manner as to press-fit the prosthetic tibial insert
Data Source
AI summary
The invention relates to a base that includes a unit for osseous attachment onto a tibia, and a plate having posterior, anterior, medial and lateral edges; a posterior pin and an anterior pin having a posterior flat section and an anterior flat section; two posterior lugs protruding above the plate and arranged on the posterior edge of each side of the posterior pin; and two anterior lugs arranged on each side of the anterior pin. The posterior flat section and the anterior flat section are arranged so as to simultaneously engage with the insert. Each posterior tab includes a support extension for inserting, in an anteroposterior direction, a complementary support tab of the insert. Each anterior lug includes a unit for snap-coupling the insert onto the base.