Metatarsophalangeal resurfacing joint
View Patent ↗The present invention provides a prosthesis for implantation at the proximal articular surface of a proximal phalange, of a human great toe. The prosthesis comprises a base portion having a generally concave bearing surface shaped to articulate with the distal articular surface of a metatarsal bone, and a flat surface opposite the bearing surface for emplacement against a resected surface of the proximal phalange of the great toe of the human subject. A stem extends distally from the flat surface of the base portion, for implantation in the intramedulary canal of a proximal phalange of the great toe of the human subject. The stem has a generally frustoconical shape, with a substantially oval wide end at the flat surface of the base portion, tapering to a substantially circular end. The generally frustoconically shaped stem has a longitudinal axis that is inclined at an anatomical angle, of about 94° to the base portion, to align with the intramedulary canal of a proximal phalanx of the great toe of the human subject.
1. A prosthesis for implantation at the proximal articular surface of a proximal phalange, of a human great toe, comprising:
a base portion having a generally concave bearing surface shaped to articulate with the distal articular surface of a metatarsal bone, and a flat surface opposite the bearing surface for emplacement against a resected surface of the proximal phalange of the great toe of the human subject; and
a stem extending distally from said flat surface of said base portion, for implantation in the intramedulary canal of a proximal phalange of the great toe of the human subject, said stem having a generally frustoconical shape, with a substantially oval wide end at the said flat surface of the base portion, tapering to a substantially circular end, said generally frustoconically shaped stem having a longitudinal axis that is inclined at an anatomical angle, of about 94° to the base portion, to align with the intramedulary canal of a proximal phalanx of the great of the human subject.
2. A prosthesis as claimed in claim 1 , wherein said stem has a side surface that tapers inwardly.
3. A prosthesis as claimed in claim 2 , wherein said side surface of said stem is somewhat flattened in three aspects, between the base and end of the stem.
4. A prosthesis as claimed in claim 1 , wherein said surface of said stem is textured for adhesion to the inner surface of a said intramedulary canal.
5. A prosthesis as claimed in 1 , wherein said surface of said stem is ridged in a series of ridges that extend around said stem, parallel to said base portion.
6. A prosthesis as claimed in claim 5 , wherein said ridges are substantially barb-like.
7. A prosthesis as claimed in claim 6 , wherein each said barb-like ridge includes a long flat portion almost parallel to the side surface of the stem, and a short inwardly directed portion at a greater angle to said side surface.
8. A prosthesis as claimed in claim 3 , wherein said side surfaces of said stem, where flattened, are knurled by cross-hatching.
9. A prosthesis as claimed in claim 8 , wherein said stem, in corner areas between said flattened aspects, is provided with barb-like ridges.
10. A prosthesis as claimed in claim 9 , wherein each said barb-like ridge comprises an arcuate portion having a surface almost parallel to the side surface of said stem, and a short inwardly directed portion at a greater angle to said side surface.