Surgical Reamer With Undercut Bone Shelf For Dowel Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for fusing spinal facet joints often fail due to dowel migration out of the drilled hole, as there is no feature to retain the dowel within the smooth hole, necessitating repeated surgical procedures.
Innovation Solution
A kit and method using a surgical instrument to create an undercut in the facet joint, featuring a cutter that forms a shelf of bone to retain the dowel, ensuring it is trapped within the joint as the joint closes over it, preventing migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a smooth hole is drilled through the facet joint for dowel insertion, then the surgical procedure is simple and quick, but the dowel migrates out of the hole before bone fusion occurs
Solution Approach 1:
The cutter creates an undercut feature (bone shelf) in advance within the drilled hole before dowel insertion. This preliminary structural modification ensures that when the dowel is inserted, the pre-formed undercut engages with the dowel to prevent migration, thus resolving the contradiction between simple insertion and reliable retention.
Solution Approach 2:
The cutter introduces an asymmetric undercut geometry (bone shelf) into the otherwise symmetric cylindrical hole. This asymmetric feature creates a mechanical interlock with the dowel, preventing it from migrating out along the insertion path, thereby maintaining both ease of insertion and reliable retention.
2Reliability
If the joint is expanded to insert the dowel, then the dowel can be retained within the joint, but the cutting instrument must be removed through the same narrow plane of insertion
Solution Approach 1:
The cutter is designed with a flattened profile in the opposing plane, allowing it to be inserted through the narrow joint plane and then removed by rotating or translating in a different dimensional orientation. This dimensional maneuvering enables instrument removal without requiring excessive joint expansion, thus maintaining dowel retention while simplifying instrument extraction.
Data Source
AI summary
A surgical reamer for cutting an opening in a facet joint for placement of a dowel between the sides of the facet joint to immobilize the joint and create a fusion. The reamer is used with a set of surgical instruments to prepare facet joints for insertion of dowels. The reamer creates a bone shelf above the opening for the dowel to prevent migration of the dowel. The reamer is configured with a flat profile in one plane to allow insertion into the facet joint and the profile of the dowel in the perpendicular plane to create a shape corresponding to the dowel when rotated. The neck of the reamer is smaller in diameter at the coronal end to allow creation of a bone shelf in the facet above the opening for the dowel. The bone shelf resists migration of the dowel out of the prepared opening in the facet.