Hip Prosthesis Femoral Stem Asymmetric Cross-Section
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Solution Overview
Problem
Conventional hip prostheses face issues such as detachment of the femur stem, bone removal, difficulty in revisions, and complications with mini-invasive techniques due to standard length and shape, which lead to rotation and sinking phenomena within the femur channel, and inadequate osteo-integration.
Innovation Solution
A hip prosthesis with a femoral stem having an arc-shaped medial portion and longitudinal reliefs with specific angle and groove designs to enhance bone integration, allowing for a shorter stem length that distributes mechanical tension and preserves bone tissue, featuring a tapered shape and beveled edges for improved insertion and removal, and a prosthetic neck with adjustable angles for anatomical compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If standard length femur stems are used, then stability is improved, but bone tissue preservation deteriorates and mini-invasive technique application becomes difficult
Solution Approach 1:
The patent changes the geometric parameters of the femur stem, specifically creating an asymmetric cross-section with a convex medial side and conc lateral side, along with specific longitudinal reliefs and grooves. This allows optimization of the stem length and dimensions to achieve stability with reduced bone removal, enabling mini-invasive techniques while maintaining fixation strength.
Solution Approach 2:
The femur stem features an asymmetric design with the medial side having a convex shape and the lateral side having a concave shape. This asymmetry allows the stem to better fit the natural anatomy of the femoral canal, improving stability while requiring less bone removal for proper positioning and fixation.
2Ease of manufacture
If standard prosthesis design is used, then manufacturing simplicity is maintained, but rotation and sinking phenomena occur
Solution Approach 1:
The femur stem is segmented with multiple longitudinal reliefs and grooves along its length. These segments increase the surface area for bone contact and interlocking, preventing rotation and sinking while maintaining a relatively simple overall stem structure that can be manufactured using conventional processes.
Solution Approach 2:
The medial side of the femur stem features a convex curved surface that contacts the medial cortical bone, while the lateral side has a concave curvature. This curvilinear design improves contact with the femoral canal walls, enhancing anti-rotation capability and preventing sinking without complicating manufacturing.
3Ease of operation
If femur stem is inserted with recto or acute angle, then insertion is simplified, but bone/prosthesis structure continuity is disrupted requiring osteotomy
Solution Approach 1:
The asymmetric cross-section of the femur stem, with convex medial side and conc lateral side, provides inherent orientation guidance during insertion. This asymmetry ensures proper angular alignment with the femoral canal, allowing insertion while maintaining bone-prosthesis structure continuity and eliminating the need for osteotomy to correct angular mismatches.
4Stability of the object's composition
If broken trapezoidal cross-section stem is used, then stereo-stability is increased, but four point contacts with cortical bone are imposed and stem volume is under-dimensioned
Solution Approach 1:
The patent replaces the angular broken trapezoidal cross-section with a design featuring convex and concave curved surfaces on the medial and lateral sides respectively. This curvilinear geometry provides continuous surface contact with the cortical bone rather than discrete point contacts, distributing stresses more evenly while maintaining stereo-stability.
Solution Approach 2:
The femur stem employs different surface geometries in different locations: the medial side has a convex shape for cortical bone contact, while the lateral side has a concave shape. This local differentiation optimizes contact characteristics in each region, providing stable fixation without stress concentration at discrete points.
Data Source
Figure 1~8
Figure 4
AI summary
The present invention relates to a hip prosthesis (1) comprising a femoral stem (20) that can be inserted within the medullar channel of a patient femur, the medial side (21) of said femoral stem (20) having, in the proximal portion (40), the shape of an arc, said femoral stem (20) being provided with substantially longitudinal lateral reliefs (60, 61), so that said stem (20) can be fixed to the bone tissue by pressure, and a prosthetic neck (30), provided with means for coupling with a morse cone type spherical head (31), said prosthesis (1) being characterised in that the cross section of said longitudinal reliefs (60, 61 ) has an apex portion (60'), having the lateral walls included within a first angle (c), and a base portion having the lateral walls included within a second angle (d), which is minor or equal to said first angle (c), and in that grooves (63) are provided between said longitudinal reliefs (60, 61), that can be homogeneously filled with spongious bone tissue.