Plastic Patellar Prosthesis with Deformable Pin Projections
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Solution Overview
Problem
Conventional plastic patellar prostheses require a patellar clamp to secure the prosthesis during bone cement curing, interrupting the knee replacement surgery process.
Innovation Solution
The development of patellar prostheses with anterior surfaces featuring a plurality of pins, each with projections that deform upon insertion into the patella, providing a mechanical restraint to secure the prosthesis without the need for a patellar clamp, allowing the surgery to proceed uninterrupted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bone cement is used to secure the patellar prosthesis, then the prosthesis can be attached to the patella, but the surgery must be interrupted while the cement cures
Solution Approach 1:
The prosthesis is segmented with multiple pins extending from its anterior surface, each pin capable of being inserted into the patella to provide independent mechanical anchoring. This segmentation allows the prosthesis to achieve secure attachment through multiple discrete points rather than relying solely on bone cement curing time.
Solution Approach 2:
The pins are pre-formed with projections that will mechanically engage the patella tissue upon insertion. This preliminary preparation of the pins with engagement features allows them to provide immediate mechanical restraint as soon as they are inserted, eliminating the need to wait for bone cement to cure.
2Reliability
If a patellar clamp is used to apply compressive force while bone cement sets, then the prosthesis remains secure during curing, but additional tools and surgical complexity are required
Solution Approach 1:
The prosthesis itself provides the stabilization function through its pins with projections that mechanically engage the patella. The prosthesis structure serves dual purposes: as the functional implant and as its own securing mechanism, eliminating the need for separate patellar clamps or other stabilization tools.
Solution Approach 2:
The securing function is merged with the prosthesis structure itself. The pins with projections are integrated into the prosthesis body, combining the implant and fixation mechanism into a single unified device, thereby eliminating the need for separate clamping tools.
3Measurement precision
If conventional lugs and receptacles are used for orientation, then the prosthesis can be oriented relative to the patella and femoral component, but mechanical security during cement curing is insufficient
Solution Approach 1:
The prosthesis combines plastic material with integrated metal or reinforced pins featuring projections. This composite construction provides both the orientation function of the pins and the mechanical security of the projections, achieving dual functionality within a unified structure.
Solution Approach 2:
The pins are designed with asymmetric projections that provide both orientation guidance and mechanical engagement. The projections create an asymmetric geometry that prevents rotation and provides directional stability, combining orientation and security functions in a single asymmetric feature.
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
Enables continuous surgery during cement hardening, providing additional mechanical security post-curing, reducing the need for additional tools and potentially lowering surgical time and costs.
Implementation Method 1
each of the plurality of pins has an outer surface between an end and the anterior surface. The one or more projections on the at least one plastic pin may extend outwardly from the outer surface of the at least one plastic pin. The one or more projections on the at least one plastic pin may contact a surface of a hole formed in the prepared surface of the patella into which the pin is inserted and thereby mechanically restrain the patellar prothesis from moving relative to the natural patella while bone cement cures between the anterior surface and the prepared surface of the natural patella.
Data Source
AI summary
A plastic patellar prosthesis having a plurality of orienting pins, each pin having one or more projections that define a maximum diameter greater than the diameter of the patellar hole into which the orienting pin is inserted. The diametrical interference causes the projections to deform and thereby mechanically secure the patellar prosthesis to the resurfaced patella as the cement cures without the need for a patellar clamp to hold the prosthesis in place.