Hip Implant Compression Resistance and Self-Centering
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Solution Overview
Problem
Current hip implants for total hip replacement face challenges in durability due to osteonecrosis progression, particularly in the femoral neck region, leading to potential failure and the need for early replacement, especially in younger patients who wish to maintain an active lifestyle.
Innovation Solution
A hip implant design featuring a tapered femoral neck rod with a diagonal hole in the main body shaft, secured by a compression screw set, providing a stable and adjustable interface that resists axial and bending forces, using bio-compatible materials like cobalt, chromium, titanium, and polymers to ensure long-term durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If bone cement is added to secure the implant parts to the remaining bone material, then the implant stability is improved, but the implant durability is still compromised due to progressive osteonecrosis degradation
Solution Approach 1:
The implant is divided into multiple segments: a main body shaft inserted into the femoral shaft, a femoral neck rod inserted into the femoral neck, and bone cement applied at both interfaces. This segmentation allows each component to bear specific loads and provides redundant fixation points, preventing single-point failure even as osteonecrosis progresses.
Solution Approach 2:
Bone cement is applied in advance to both the femoral shaft interface and the femoral neck interface before final implant assembly. This preliminary action ensures that the cement has sufficient time to cure and bond the implant components to the bone structure, creating a stable foundation that resists progressive bone degradation.
2Force
If the femoral neck rod is made thinner to reduce stress on the implant, then the stress on the implant is reduced, but the rod becomes more susceptible to bending and failure
Solution Approach 1:
The femoral neck rod features localized structural variations: it has a thinner midsection to reduce stress concentration, but incorporates thicker reinforced sections near the ends where it connects to the main body shaft and the femoral head. This local quality optimization allows the rod to be lightweight and stress-resistant while maintaining sufficient bending strength through strategic reinforcement at critical locations.
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 design significantly enhances implant stability and durability, reducing the risk of failure and extending the lifespan of the implant, even in patients with or at risk of osteonecrosis, by securely engaging the femoral neck rod and main body shaft, thus accommodating varying femur angles and loads.
Implementation Method 1
A secured lock mechanism in the form of a compression screw set is insertable into the main body shaft above the diagonal hole and can be screwed down to compressively engage the tapered end of the femoral neck rod
Implementation Method 2
the femoral neck rod has a tapered end that engages in a hole through the main body shaft. That is, the main body shaft has a diagonal hole therethrough located at the center line of the neck of the femur to receive the tapered end of the femoral neck rod at a specified angle
Data Source
AI summary
A hip implant comprises an acetabular cup to be inserted into an acetabulum of a pelvis, together with a femoral head and neck portion and a main body shaft to be inserted into the femoral neck and proximal femoral shaft. The femoral head and acetabular cup form a smooth spherical-surface joint. The femoral head on a femoral head base is attached to a femoral neck rod, which has a tapered end that engages in a hole through the main body shaft, i.e. the main body shaft has a diagonal hole therethrough located at the center line of the neck of the femur to receive the tapered end at a specified angle that aligns with center line of the neck. A secured lock mechanism, insertable into the main body shaft above the diagonal hole, can be screwed down to compressively engage the tapered end of the femoral neck rod. The diagonal hole (and matching tapered end of the femoral neck) can have an overlapping two-circle cross-section, can have a specified taper angle, and a choice of incline to match a patient's femoral angle between the neck and shaft. The tapered neck rod can have wedge-shaped locking surface features to provide even more stability.