Self-Broaching Hip Stem for Femoral Neck Bone Preservation
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Solution Overview
Problem
Conventional hip prostheses require extensive instrumentation and resection of healthy bone stock, leading to decreased stability and increased surgical complexity, while conventional stems load the femur distally, leaving minimal bone at the femoral neck.
Innovation Solution
A self-broaching hip prosthesis with a curved, tapering stem featuring rasp teeth on its distal-lateral surface that carves its own path during implantation, preserving bone stock and reducing the need for pre-operative canal preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional stems are used to extend deep into the femoral canal for adequate fixation, then initial stability and long-term fixation are achieved, but significant healthy bone stock is resected and lost
Solution Approach 1:
The patent inverts the conventional approach by having the stem load the femur proximally at the calcar region rather than distally. This reversal of loading direction allows the stem to achieve fixation without requiring deep insertion that would compromise healthy bone stock, as the load is transferred through the preserved proximal femoral structures.
Solution Approach 2:
The stem features a self-broaching distal-lateral surface with rasp teeth that carve its own insertion path during implantation. This self-preparation mechanism eliminates the need for extensive pre-operative canal preparation with multiple broaches, preserving bone stock while still achieving adequate fixation depth.
2Manufacturing precision
If sequentially increasing sizes of broaches are used to prepare the femoral canal, then the canal is prepared to the required depth, but surgical complexity and equipment requirements increase
Solution Approach 1:
The stem's distal-lateral surface incorporates rasp teeth that enable the stem to self-broach the femoral canal during insertion. This eliminates the need for a family of sequentially increasing broaches, simplifying the instrumentation required while still achieving the necessary canal preparation depth and precision.
Solution Approach 2:
The patent combines the canal preparation function and the implant insertion function into a single action. The self-broaching stem performs both the canal shaping and the implantation in one step, merging what were previously separate processes requiring multiple instruments into a unified procedure.
3Ease of operation
If the standard level of resection is distal to the femoral neck, then the stem can be inserted, but little to no bone remains at the femoral neck
Solution Approach 1:
The patent inverts the resection level from distal to proximal to the femoral neck. By resecting proximal to the neck and preserving the distal neck, the procedure maintains adequate bone stock at the femoral neck while still allowing stem insertion. This inversion of the resection approach preserves critical bone structures.
Solution Approach 2:
The proximal resection is performed in advance to create the necessary access and space for stem insertion, while deliberately preserving the distal neck bone. This preliminary action of selective resection enables subsequent stem implantation without compromising the femoral neck bone stock.
4Reliability
If conventional stems load the femur distally, then fixation is achieved, but bone stock in the proximal femur is not preserved
Solution Approach 1:
The patent inverts the loading direction from distal to proximal. The stem is designed to load the femur at the calcar region proximally rather than distally, which preserves bone stock in the proximal femur by maintaining physiological load transfer through the preserved bone structures while still achieving reliable fixation.
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 solution provides improved implant load distribution, reduced risk of trochanteric fractures, enhanced joint stability, and easier revision options by preserving bone stock, while simplifying the surgical workflow.
Implementation Method 1
rasp teeth on a distal-lateral surface capable of self-broaching upon implantation
Data Source
Figure 1A
Figure 1B~1C
Figure 2
AI summary
A self-broaching, neck-preserving hip stem includes a set of rasp teeth on a distal-lateral portion of the stem to allow the stem to be impacted into a femur without the use of surgical broaches. The rasp teeth are disposed on a relief surface. The stem includes a length, radius of curvature, and a dual-taper in the anterior-posterior and distal-lateral directions which allow the neck to self-broach and seat itself proximal to the conventional resection level to preserve greater bone stock in the femur.