Surgical Prostheses With Surface Treatment Alignment Marks
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Solution Overview
Problem
Conventional acetabular cup placement is challenging due to incorrect alignment, increased wear rate, and tissue abrasion from rough surfaces, particularly for inexperienced surgeons who struggle with compound angles and surface treatments.
Innovation Solution
A rotationally symmetrical cup with a convex surface featuring alignment marks created by interruptions in the coating or surface treatment, promoting osseointegration and aiding correct positioning by indicating intended protrusion from the bone cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cup surface is treated to promote osseointegration (e.g., etching, porous coating), then bone bonding is improved, but surface roughness increases causing tissue abrasion
Solution Approach 1:
The patent applies different surface treatments to different zones of the cup: the bone-contacting surface receives osseointegration promotion treatment (etching or porous coating) while the protruding rim portion maintains a smooth finish. This local differentiation allows the bone bonding function to be enhanced where needed without causing tissue abrasion on the soft tissue-contacting rim.
Solution Approach 2:
The cup surface is divided into distinct functional zones: a smooth rim portion for soft tissue compatibility and a separately treated bone-contacting surface for osseointegration. This segmentation allows each zone to have optimized surface properties suited to its specific function, resolving the contradiction between bone bonding and tissue safety.
2Ease of operation
If the cup is positioned flush with the acetabulum rim to replicate natural orientation, then alignment is simplified, but hip movement is restricted
Solution Approach 1:
The cup is designed with an asymmetric configuration where the rim protrudes above the acetabular rim rather than sitting flush. This asymmetric positioning, combined with the alignment marks, guides the surgeon to the correct eccentric position that preserves hip movement while maintaining proper orientation relative to bone landmarks.
Solution Approach 2:
Alignment marks are pre-positioned on the cup at predetermined angles relative to the rim, indicating the correct protrusion position before implantation. This preliminary visual guidance eliminates the need for complex intraoperative angle calculations and ensures correct positioning is achieved intuitively, resolving the contradiction between ease of operation and movement preservation.
3Measurement precision
If alignment marks are created by interruptions in coating or surface treatment, then positioning accuracy is improved, but manufacturing complexity increases
Solution Approach 1:
The alignment marks are created by applying the bone-contacting surface treatment (etching or porous coating) selectively to specific zones while leaving other areas smooth. This local quality differentiation creates visible contrast that serves as alignment guidance during implantation without requiring complex manufacturing processes.
Solution Approach 2:
The alignment marks are created through visual contrast in surface appearance (analogous to color changes) - the treated areas have different surface properties (roughness, porosity, or coating presence) compared to untreated areas. This visual differentiation provides clear positioning guidance without adding complex manufacturing steps, as the surface treatment process itself creates the marking contrast.
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 alignment marks assist surgeons in correctly positioning the cup relative to bone landmarks, reducing incorrect implantation and wear rates while minimizing surface roughness for tissue safety.
Implementation Method 1
Osseointegration is the direct structural and functional connection between living bone and the surface of a prosthesis. Osseointegration may either result from mechanical retention whereby bone ingrowth into surface features of a prosthesis, in particular a metal prosthesis, secures the prosthesis to the bone, or bioactive retention whereby the implant is coated with a bioactive material which stimulates bone formation leading to a chemical bond in which the implant is ankylosed with the bone.
Implementation Method 2
Osseointegration may either result from mechanical retention whereby bone ingrowth into surface features of a prosthesis, in particular a metal prosthesis, secures the prosthesis to the bone
Data Source
Figure 1~3
AI summary
A prosthesis arranged to be coupled to a bone. The prosthesis comprises a substrate (2) having a surface (6). The surface (6) of the substrate (2) has a first area and a second area, the first area being treated such that osteointegration is promoted more than in the second area. The interface (12) between the first and second areas forms an alignment mark to assist alignment of the prosthesis relative to a bone. The prosthesis is arranged to be at least partially inserted into a bone cavity such that the position of the alignment mark relative to the bone cavity is indicative of the angle of insertion of the prosthesis or the alignment mark provides a position reference for determining the implanted position of the prosthesis in the cavity. A method of manufacturing the prosthesis and a method of implanting the prosthesis are also provided.