In-Bone Implantable Shaft with Longitudinal Slots for Osseolocking
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Solution Overview
Problem
Existing prosthetic implant attachment methods in bones often lead to loosening due to the destruction of endosteal bone trabeculae during installation and natural limitations in bone remodeling volume, which restricts the anchoring effectiveness.
Innovation Solution
The method involves preparing the bone walls with longitudinal slots during standard drilling of the medullary canal, allowing the implant's side elements to fit into these slots, promoting ossification and natural locking without the complications of traditional methods like inter-locking nailing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the medullary canal is drilled to prepare the bone for implant insertion, then the implant can be fitted into the bone, but the endosteal bone trabeculae are destroyed and the natural anchoring mechanism is compromised
Solution Approach 1:
The invention divides the anchoring mechanism into two independent components: (1) the drilled medullary canal for implant insertion, and (2) longitudinal slots cut into the cortical bone walls for protruding side elements. This segmentation allows each component to serve its specific function without interfering with the other, preserving the endosteum while enabling secure anchoring.
Solution Approach 2:
The protruding side elements of the implant are nested into the longitudinal slots cut in the cortical bone walls, creating a hierarchical structure where the implant shaft resides in the medullary canal while its side elements extend into and lock within the cortical bone, achieving multi-level anchoring.
2Reliability
If screws are inserted to secure the implant, then additional anchoring is achieved, but operation time and positioning complexity increase
Solution Approach 1:
The longitudinal slots are cut into the cortical bone walls during the initial bone preparation phase, before implant insertion. This preliminary action ensures that when the implant is inserted with its protruding side elements, the anchoring slots are already in place, eliminating the need for subsequent screw insertion and reducing surgical time.
Solution Approach 2:
The implant's own structure (protruding side elements) serves the dual function of both structural support and anchoring, eliminating the need for separate anchoring elements like screws. The side elements naturally lock into the pre-cut slots, making the implant self-anchoring.
3Ease of operation
If the endosteum is destroyed during drilling, then implant insertion is facilitated, but the volume of remodeled bone tissue is limited
Solution Approach 1:
The invention transitions from relying solely on radial ossification (outward-inward direction limited by endosteum) to utilizing longitudinal ossification along the bone's length. The protruding side elements in longitudinal slots create anchoring surfaces that extend along the longitudinal axis, accessing a much larger volume of bone tissue for remodeling and ossification.
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
This approach enhances osseolocking by increasing the volume of remodeled bone tissue, effectively preventing implant loosening and providing a stable anchoring effect similar to inter-locking nailing without its complexities.
Implementation Method 1
osteocytes begin to remodel the internal canal walls and fill the gaps between the implant and the walls, including the specially designed cavities or pores in the implant. The remodeling proceeds in the direction out from the outer walls toward the interior walls of the medullary canal. Such ossification fixes the implant inside the bone canal by developing multiple micro locks
Implementation Method 2
bone lengthening techniques, when an external apparatus is applied for the fixation of the bone fragments that are created after the bone is dissected perpendicularly to its longitudinal axis. Then, with the aid of the given external apparatus, bone fragments are moved apart 1-2 mm per day. Continued ossification, when properly controlled, allows the bone to lengthen up to 33% of its original length
Data Source
AI summary
An in-bone implantable shaft for prosthetic joints or for direct skeletal attachment of external limb prostheses, comprised of a central body fitted in the zone of the bone's medullary cavity conventionally prepared for implantation, and of side elements attached to the central body and fitted in the slots specially made in the bone's walls surrounding said medullary canal; said side elements have spaces between them, arranged to be filled by bone cells to provide a natural and safe osseolocking of the shaft. A method of preparing the bone for implantation of a prosthetic shaft, comprising the steps of: placing a cylindrical guide with slots made in the longitudinal direction of said guide inside said bone's canal which is conventionally prepared for implantation; cutting said bone's walls by progressing a saw along the edges of the slots of said guide; removing the guide; fitting the shaft in the bone's canal, provided that the side elements are fitted to the slots in the bone's walls.