Resorptive intramedullary implant between two bones or two bone fragments

What is this patent about?

’074 is related to the field of orthopedic implants, specifically intramedullary devices used for arthrodesis or osteosynthesis in the small bones of the hand or foot. Traditional metal implants often require secondary surgeries for removal or can cause long-term irritation, leading to the development of bioresorbable alternatives. However, creating a stable, load-bearing connection using resorbable polymers like PLA or PGA is challenging because these materials lack the inherent stiffness of metal, necessitating a specialized geometry to ensure primary stability and compression during the bone healing process.

The underlying idea behind ’074 is the use of a hybrid anchoring geometry that combines a rigid mechanical screw interface with an elastic, multi-directional friction fit. By utilizing a bioresorbable polymer body, the inventor recognized that a single anchoring method might not provide sufficient rotational and axial stability. The solution employs a threaded cylindrical post on one end to provide high-torque fixation in the first bone fragment, paired with a deformable flat section on the other end that acts as an internal spring-loaded barb to grip the second bone fragment.

The claims of ’074 focus on an intramedullary implant featuring a first threaded end and a second end characterized by a specific arrangement of outwardly projecting teeth. These teeth are strategically distributed along the longitudinal axis, with at least two teeth spaced apart axially while pointing in the same direction, and a third tooth oriented in a different direction to provide multi-axis resistance. Furthermore, the second end includes a central opening that allows the body to compress and expand elastically, ensuring the teeth maintain constant pressure against the internal bone walls.

In practice, the implant is installed by first screwing the cylindrical threaded end into a pre-tapped hole in the proximal bone until a central transition zone acts as a physical stop. The distal bone fragment is then pressed onto the flat end, where the elastic deformation of the bifurcated arms allows the teeth to bypass the bone's internal cortical surface before springing outward to lock the assembly in place. This transition zone is specifically thickened to withstand the shear and flexion forces that occur at the joint line during the six-month resorption window.

This design differentiates itself from prior art by optimizing the geometry for the mechanical limitations of resorbable plastics. Unlike traditional X-shaped elastic implants or simple threaded pins, this hybrid approach uses a bifurcated flat section to provide lateral stability and anti-rotation that a standard screw cannot achieve in soft cancellous bone. By combining a high-strength threaded anchor with a flexible, barbed distal end, the implant ensures the two bone fragments remain compressed and aligned without the need for permanent metallic hardware.