Dynamic axial nail for intramedullary treatment of long bone fractures
View Patent ↗An intramedullary nail for fixation and stabilization of a fractured bone that also allows for a controlled amount of longitudinal motion at the fracture site to encourage bone remodeling and healing is described. The intramedullary nail has a proximal portion and a distal portion that are coupled together in a manner by a biasing assembly that provides for a controlled movement of the proximal and distal portions relative to each other so that when a patient puts pressure on the bone, such as when walking, the fracture site compresses and the bone ends move together, and when the pressure is released from the bone, the bone ends are biased apart by a controlled amount.
1. An intramedullary nail configured for insertion across a fracture site of a bone, the fracture site comprising first and second portions, comprising:
a distal portion having a distal end having a first diameter and a proximal end having a second diameter smaller than the first diameter, the distal end also having a first land formed at an intersection of the proximal and distal ends of the distal portion;
a proximal portion having a proximal end and distal end, the distal end of the proximal portion configured to moveably receive the proximal end of the distal portion, the first land, and a portion of the distal end of the distal portion, the distal end of the proximal portion having a first bore having a first diameter extending from the distal end of the proximal portion to a second land formed by an intersection of the first bore with a second bore having a second diameter less than the first diameter of the first bore;
a space fined by the first land and second land;
a reversibly compressible bias member disposed in the space for biasing the distal and proximal portions apart along a longitudinal axis; and
an adjusting assembly configured to engage the distal and proximal portions such that actuation of the adjusting assembly alters a longitudinal length of the space so that an overall length of the intramedullary nail results in separation of the first and second portions of the fractured bone when the intramedullary nail is disposed across the fracture site.
2. The nail of claim 1 , wherein the distal and proximal portions are in a telescoping arrangement relative to each other.
3. The nail of claim 2 , wherein when the adjusting assembly is adjustable to allow a selected amount of movement along the longitudinal axis between the proximal and distal portions, applying a compressive force along the longitudinal axis causes a combined length of the distal and proximal portions to be reduced, and reducing the compressive force allows the combined length of the distal and proximal portions to increase.
4. The nail of claim 2 , further comprising an alignment assembly that engages the proximal and distal portions in a manner to maintain an alignment between the proximal and distal portions.
5. The nail of claim 1 , wherein an outer surface of the distal and proximal portions is covered with a material that enhances healing of a fracture.
6. The nail of claim 5 , wherein the material is zinc.
7. The nail of claim 1 , wherein the bias member is a spring.
8. The nail of claim 1 , wherein the bias member is formed from a reversibly compressible material.