Spherical Head Bone Fixation Device for Epiphyseal Fracture Stability
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Solution Overview
Problem
Current treatments for fractures in the epiphyseal portion of bones, such as femoral neck fractures, often result in inadequate fracture reduction due to limited contact area between bone fragments, leading to delayed healing and cyclic overload of the implant, which can cause loosening or implant cutout, especially in the sagittal plane where visualization is difficult.
Innovation Solution
A bone implant with a spherical head element and a longitudinal shaft that allows the epiphyseal fragment to pivot and axially displace, distributing load over a larger contact area, combined with a slidable configuration with a bone plate or intramedullary nail, enabling partial compensation for inadequate fracture reduction and improved stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a femoral neck screw is used to treat epiphyseal fractures, then angular stability between the screw and bone plate/intramedullary nail is provided, but the contact area between fractured bone portions remains limited
Solution Approach 1:
The fixation element allows dynamic adjustment of the epiphyseal fragment position through pivoting motion around the spherical head element center and axial displacement along the shaft. This dynamic capability enables the fragment to rotate and translate until optimal fracture reduction and maximum contact area are achieved, resolving the contradiction between maintaining angular stability and increasing bone fragment contact area
Solution Approach 2:
The spherical head element with radius R larger than shaft radius r creates a geometric relationship that enables angular rotation parameter changes. The ratio r/R (at least 0.65, preferably at least 0.7) determines the pivot range, allowing the epiphyseal fragment to change its orientation and position parameters to achieve better fracture reduction and increased contact area while maintaining stability
2Ease of manufacture
If fracture reduction is inadequate, then implantation can proceed, but cyclic overload occurs leading to implant loosening and/or cutout
Solution Approach 1:
The slidable configuration between the longitudinal shaft and bone plate/intramedullary nail allows axial displacement that dynamically adjusts to fracture healing stages. This enables the implant to accommodate movement and distribute loads more evenly, preventing cyclic overload and improving reliability without requiring perfect initial fracture reduction
Solution Approach 2:
The spherical head element acts as a cushioning mechanism that absorbs and distributes mechanical stresses before they can cause damage. By allowing controlled pivoting and displacement, the spherical geometry cushions the implant-bone interface against cyclic overload, preventing loosening and cutout even when fracture reduction is not optimal
3Adaptability or versatility
If the spherical head element allows pivoting, then compensation for inadequate fracture reduction is achieved, but the device complexity increases
Solution Approach 1:
The spherical head element with radius R larger than shaft radius r provides a simple yet effective geometric solution for enabling pivoting motion. This spherical geometry naturally allows angular rotation and position adjustment without complex mechanisms, achieving adaptability for compensating inadequate fracture reduction while maintaining relatively simple device structure
Solution Approach 2:
The fixation element merges multiple functions into a single integrated component: the longitudinal shaft provides axial stability and sliding capability, while the spherical head element provides pivoting motion and position adjustment. This combination achieves both angular stability and adaptability for compensating fracture reduction deficiencies without requiring separate complex mechanisms
Data Source
AI summary
A fixation device for treating an epiphyseal fracture, comprises a shaft extending longitudinally along a central axis from a first end to a second end configured to slidably engage a bone implant opening and a having a maximum radius r and a spherical head element attached to the first end of the shaft and having a radius R>r, the spherical head element configured to be inserted into a fragmented portion of bone such that the fragmented portion rotates about the spherical head element relative to the central axis of the shaft.