Tensioned meniscus prosthetic devices and associated methods
A prosthetic device for use as an artificial meniscus is disclosed. The prosthetic device restores shock absorption, stability, and function to the knee joint after removal of the damaged natural meniscus. In some embodiments, the prosthetic device is pre-tensioned to improve the fit of the prosthetic device within the knee joint and, thereby, maximize the contact area of the load-bearing surfaces to distribute loading through the prosthetic device in a manner substantially similar to that of a healthy natural meniscus. In some embodiments, the pre-tensioned prosthetic device is smaller, or scaled-down, relative to the size of a healthy natural meniscus.
1. A prosthetic device for replacing a damaged meniscus, the prosthetic device comprising:
a central portion having a concave upper surface for engagement with a portion of a femur and an opposing partially concave lower surface for engagement with a portion of a tibia, the central portion comprising a flexible resilient polymeric material having a modulus of elasticity between about 1 MPa and about 10 MPa, wherein the central portion has a minimum thickness less than about 3 mm between the upper surface and the lower surface;
an outer portion surrounding the central portion and having an increased thickness relative to the central portion, the outer portion comprising the resilient polymeric material and tensioned with at least one reinforcing fiber embedded within the resilient polymeric material;
wherein the outer portion is sized and shaped such that a compression force imparted on the prosthetic device by the femur and the tibia displaces the outer portion radially outward from the central portion;
wherein the outer portion is further sized and shaped such that the prosthetic device is configured for implantation within a knee joint between the femur and the tibia without being rigidly fixed to either of the femur and the tibia and the outer portion prevents unwanted expulsion of the prosthetic device from the knee joint when the prosthetic device is implanted within the knee joint without being rigidly fixed to either of the femur and the tibia.
2. The prosthetic device of claim 1 , wherein the at least one reinforcing fiber is tensioned at a force between about 5 N and about 78 N.
3. The prosthetic device of claim 2 , wherein the at least one reinforcing fiber is tensioned at a force between about 7 N and about 8 N.
4. The prosthetic device of claim 2 , wherein the at least one reinforcing fiber is tensioned at a force between about 8 percent and about 12 percent of the at least one reinforcing fiber's maximum tension.
5. The prosthetic device of claim 1 , wherein the compression force imparted on the prosthetic device is at least partially transformed into a tensile load on the at least one reinforcing fiber.
6. The prosthetic device of claim 5 , wherein the at least one reinforcing fiber extends completely around the central portion within the outer portion.
7. The prosthetic device of claim 1 , wherein the central portion stretches as the outer portion is displaced radially outward by the compression force.
8. The prosthetic device of claim 7 , wherein a contact area between the portion of the femur and the upper surface of the central portion increases with the stretching of the central portion.
9. The prosthetic device of claim 7 , wherein a contact area between the portion of the tibia and the lower surface of the central portion increases with the stretching of the central portion.
10. The prosthetic device of claim 1 , wherein the resilient polymeric material is a medical grade polyurethane based material.
11. The prosthetic device of claim 10 ,wherein the resilient polymeric material is a polycarbonate polyurethane.
12. The prosthetic device of claim 11 , wherein the at least one embedded fiber comprises an ultra high molecular weight polyethylene.
13. The prosthetic device of claim 1 , wherein the outer portion comprises a first section comprising a semi-ellipsoidal profile similar to a natural meniscus.
14. The prosthetic device of claim 13 , wherein the outer portion comprises a bridge portion connecting first and second ends of the semi-ellipsoidal profile of outer portion.
15. The prosthetic device of claim 14 , wherein the bridge portion is sized to engage a femur notch.