Slotted Alignment Guide for Accurate Humeral and Femoral Stem Placement
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Solution Overview
Problem
Conventional methods for replacing the humeral and femoral heads with prosthetics face challenges in accurately positioning the stem, leading to misalignment, which can cause issues such as loosened stems, shoulder joint instability, and altered biomechanics, necessitating additional surgical procedures.
Innovation Solution
The use of an alignment guide, such as a slotted disk, to ensure proper alignment of the prosthetic stem within the medullary canal, which can be configured to fit the bone cut surface and guide the stem into the desired position, allowing for precise rotational and anterior-posterior alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to position the prosthetic stem, then the surgical procedure is simpler, but misalignment occurs leading to loosened stems and joint instability
Solution Approach 1:
The patent introduces an alignment guide as an intermediary device between the surgeon and the prosthetic stem. This guide includes a guide bore that directs the stem along the correct trajectory into the medullary canal, eliminating the need for complex manual positioning techniques while ensuring precise alignment. The guide acts as a mediator that translates the surgeon's intent into accurate stem placement.
Solution Approach 2:
The alignment guide is prepared and positioned in the bone cavity before the prosthetic stem is inserted. This preliminary positioning establishes the correct alignment pathway in advance, allowing the stem to be inserted along a pre-determined accurate trajectory rather than requiring complex real-time adjustment during insertion.
2Measurement precision
If manual positioning techniques are used, then fewer additional devices are required, but alignment accuracy decreases causing joint instability
Solution Approach 1:
The alignment guide serves as a specialized intermediary device that provides precise alignment control. It includes features such as a guide bore with specific angular orientation and positioning elements that ensure accurate stem placement. This single specialized device replaces multiple manual positioning techniques and measurements, improving alignment accuracy while adding only one essential device to the surgical suite.
3Reliability
If the stem is inserted without guidance, then the insertion process is faster, but misalignment leads to early surface wear and revision surgery
Solution Approach 1:
The alignment guide is positioned and secured in the bone cavity before stem insertion begins. This preliminary action establishes the correct alignment pathway in advance, allowing the stem to be inserted quickly along a pre-determined accurate trajectory. The guide remains in place during insertion, providing continuous alignment guidance that ensures implant longevity without significantly extending surgical time.
Solution Approach 2:
The alignment guide mediates between the insertion force and the desired stem trajectory. It includes a guide bore that physically constrains the stem to follow the correct path, and positioning elements that secure the guide relative to the bone cavity. This intermediary structure enables rapid, accurate insertion that protects against misalignment-related failures.
Data Source
AI summary
Systems and methods for assisting alignment of humeral or femoral stems during replacement surgery. In some embodiments, a slotted disk is configured to position a prosthetic stem into a canal in the humerus when the stem is driven through the slot. In another illustrative embodiment, a similar slotted disk structure is configured to position a prosthetic stem into a canal in the femur. In some embodiments, the dimensions of the slotted disk are configured to fit the surface of a surgical bone cut after the natural humeral head has been removed. The slotted disk may have a slot that is an integral part of the disk or one that is separately attachable.