Medical implants including negative Poisson's ratio materials
A medical implant includes a first implant body and a pre-coating covering at least a portion of an outer surface of the first implant body. The pre-coating has a negative Poisson's ratio. A method of making a medical implant includes applying a precursor material on a surface of a first implant body, the first implant body having a positive Poisson's ratio. A stimulus is applied to the precursor material, the stimulus causing the precursor material to form a coating having a negative Poisson's ratio
1. A medical implant comprising:
a first implant body comprising:
a first portion having a positive Poisson's ratio, and
an internal second portion embedded in the first portion, the internal second portion having a negative Poisson's ratio; and
a pre-coating covering at least a portion of an outer surface of the first implant body, the pre-coating having a negative Poisson's ratio.
2. The medical implant of claim 1 , wherein the first implant body comprises an inner cup of an acetabular cup.
3. The medical implant of claim 2 , wherein the first portion of the inner cup comprises ultra-high-molecular-weight polyethylene.
4. The medical implant of claim 1 , wherein the first implant body comprises a prosthetic femoral stem.
5. The medical implant of claim 1 , wherein the pre-coating comprises polymethyl methacrylate having a negative Poisson's ratio.
6. The medical implant of claim 1 , wherein the pre-coating comprises a bone ingrowth-promoting material having a negative Poisson's ratio.
7. The medical implant of claim 1 , wherein the pre-coating has a thickness between 1 mm and 5 mm.
8. The medical implant of claim 1 , wherein the first portion of the first implant body comprises a metal capable of forming a native oxide layer, and
wherein the pre-coating is directly in contact with the metal of the first portion of the first implant body, without the native oxide layer in-between.
9. A method of making a medical implant, the method comprising:
applying a precursor material on a surface of a first implant body, the first implant body comprising:
a first portion having a positive Poisson's ratio, and
an internal second portion embedded in the first portion, the internal second portion having a negative Poisson's ratio; and
applying a stimulus to the precursor material, the stimulus causing the precursor material to form a coating having a negative Poisson's ratio.
10. The method of claim 9 , wherein the stimulus comprises at least one of heat or pressure.
11. The method of claim 9 , comprising, prior to applying the precursor material, removing an oxide layer from the surface of the first implant body.
12. The method of claim 9 , wherein the coating has a thickness between 1 mm and 5 mm.
13. The method of claim 9 , wherein the first implant body comprises an inner cup of an acetabular cup.
14. The method of claim 9 , wherein the first implant body comprises a prosthetic femoral stem.
15. The method of claim 9 , wherein the precursor material comprises a porous foam.
16. The method of claim 9 , wherein the coating comprises polymethyl methacrylate having a negative Poisson's ratio.
17. The method of claim 9 , wherein the coating comprises a bone ingrowth-promoting material having a negative Poisson's ratio.