Locking mechanism for acetabular cup

An implantable orthopedic prosthesis comprising:

• a shell having a substantially concave inner surface and a substantially annular groove formed therein, and also having a substantially annular circumferential rim at a distal end, wherein a plurality of legs extend from said rim;
• and
• a polymeric insert positionable within said cavity, said insert having a substantially annular circumferential rim with a plurality of recesses having a size such that said legs of said shell may fit within said recesses, and said insert further having a substantially convex outer surface and a circumferential protrusion extending therefrom, said circumferential protrusion having a cross-section defined by a first surface extending radially outwardly from the outer surface of the insert and in a distal direction at an obtuse angle, a second surface adjacent said first surface and being substantially parallel to an axis of symmetry of said insert, and a third surface extending radially outwardly and in a proximal direction at an obtuse angle from said outer surface of said insert to said second surface of said circumferential protrusion, said cross-section of said protrusion being substantially congruent to a cross-section of said annular groove.

An implantable orthopedic prosthesis comprising:

• a shell having a substantially concave inner surface defining a cavity and a substantially annular groove formed therein, and also having a substantially annular circumferential rim at a distal end, wherein a plurality of leas extend from said rim;
• and
• a polymeric insert positionable within said cavity, said insert having a substantially annular circumferential rim with a plurality of recesses having a size such that said legs of said shell may fit within said recesses, and said insert further having a substantially convex outer surface and a plurality of protrusions projecting therefrom, each of said protrusions having a substantially trapezoidal cross-section wherein at least one side of said trapezoid is substantially parallel to an axis of symmetry of said insert, a cross-section of said protrusion being substantially congruent to a cross-section of said annular groove, and said inner surface of said shell being substantially congruent with a corresponding portion of the outer surface of said insert when said insert is properly positioned within said cavity of said shell.