Stemless Expandable Hip Prosthesis Bone Preservation
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Solution Overview
Problem
Current hip prostheses, especially those with stems, cause significant bone stock loss and stress shielding, leading to pain and limited mobility, and require extensive bone resection and revision surgeries, which are not ideal for younger patients with higher expectations for mobility and durability.
Innovation Solution
An expandable hip prosthesis without a stem, featuring a grooved shaft, spherical head, and expandable levers that allow for fixation at the trochanter neck, providing rotational stability and maximum motion while minimizing bone resection and promoting bone stock preservation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a stem is used in hip prosthesis to provide fixation and load transmission, then primary stability and fixation strength are improved, but bone stock loss and stress shielding increase
Solution Approach 1:
The invention extracts and removes the stem component from the prosthesis design, creating a stemless hip prosthesis that fixes directly to the femoral head. This eliminates the need for extensive bone resection required for stem insertion while maintaining fixation through direct bone-to-prosthesis contact at the femoral head level.
Solution Approach 2:
The invention transitions from longitudinal load transmission through a stem to radial load distribution through expandable levers that engage the femoral head in multiple directions. The expandable lever mechanism distributes forces across multiple dimensions of the femoral head, providing stable fixation without requiring a stem extending down the femoral shaft.
2Stability of the object's composition
If a stem is used in hip prosthesis to ensure fixation, then primary stability is improved, but stress shielding and pain occur
Solution Approach 1:
By removing the stem entirely, the invention eliminates the source of stress shielding that occurs when a stiff stem carries load away from the surrounding bone. The stemless design allows physiological stress distribution to continue through the femoral head and neck, preventing stress shielding while maintaining primary stability through direct fixation.
3Strength
If extensive bone resection is performed to accommodate stem placement, then fixation is improved, but revision surgery complexity increases
Solution Approach 1:
The stemless design removes the need for creating a stem canal through extensive bone resection. This preserves the patient's native bone stock and anatomical structure, making future revision surgeries significantly easier and less complex compared to removing a deeply embedded stem that requires substantial bone work.
4Loss of substance
If a stemless design is used to preserve bone stock, then bone preservation is improved, but rotational stability may be compromised
Solution Approach 1:
The invention employs dynamically expandable levers that transition from a compact insertion state to an expanded fixation state. During insertion, the levers are collapsed to allow easy placement into the femoral head. Once positioned, the levers are expanded outward to engage the femoral head cortex, providing robust rotational stability while maintaining bone stock preservation throughout the process.
Solution Approach 2:
The prosthesis is segmented into multiple expandable lever components rather than a single rigid stem. These segmented levers can be independently positioned and expanded to engage different aspects of the femoral head, providing multi-directional rotational stability while distributing fixation forces across multiple contact points, thereby preserving bone stock.
Data Source
Figure 1~2
Figure 3~4B
AI summary
The invention is an expandable hip prosthesis (1), to be used in patients whose femur head (F) in femur (K) is damaged due to any reason, which can replace the femur head (B), without any stem and configured in a manner such that it limits the motion within the trochanter; characterized in that; it comprises the following; a grooved shaft (15), a lower plate (4) comprising a groove in the hole in the middle in the lower section of said grooved shaft (15), an upper plate (3) fixed to the upper section where the grooved section of the grooved shaft (15) is not present, a plurality of sphere slot (5) which is disposed on the lower surface of the upper plate (3) and the upper surface of the lower plate (4), is engaged with spherical headed levers (9) and slot and spherical headed levers (8), a plurality of slot and spherical headed lever (8) and a spherical headed lever (9) which are disposed in the sphere slots (5) positioned on the lower surface of the upper plate (3) alt and the upper surface of the lower plate (4), are engaged with each other in a manner such that they can move through the joint sides (16) thereof, a spherical head (2) which is attached to the neck (10) on the upper portion of the grooved shaft (15), is appropriate to the femur head (F) anatomy.