A reamer, which comprises: a) a cutting shell having a shell wall with spaced apart exterior and interior shell surfaces (26, 28), a shell wall thickness therebetween, the shell having a curvature comprising at least a portion of a first hemisphere from an apex to a lower edge, the cutting shell being rotatable about a rotational axis (A-A) that extends through the apex, wherein at least one slit extends through the shell wall thickness; b) a plurality of cutting teeth, each having a primary tissue cutting surface, wherein the primary tissue cutting surface extends outwardly from the exterior surface of the shell; c) a ring secured to the shell lower edge, the ring having a ring thickness that extends from a ring proximal surface to a ring distal surface, a ring slot having a slot length and a slot depth, wherein the slot depth extends through the ring distal surface and at least partially through the ring thickness; d) a second blade comprising a second blade sidewall having a sidewall first end spaced from a sidewall second end, wherein the sidewall first end comprises a secondary tissue cutting surface, and wherein the sidewall second end is received within the ring slot; wherein e) a cam having opposed proximal and distal cam surfaces, wherein the cam is rotatably secured to the ring proximal surface adjacent to the shell lower edge, a ridge having a ramped surface extending from the cam distal surface, wherein the blade sidewall second end is in contact with the ridge ramped surface; and f) wherein rotation of the cam in either a clockwise or counterclockwise first direction causes the blade sidewall second end to ride up the ridge ramped surface thereby causing the secondary tissue cutting surface to extend through the at least one slit, and wherein rotation of the cam in an opposite second direction causes the blade sidewall second end to ride down the ridge ramped surface thereby causing the secondary tissue cutting surface to retract within the shell interior. a) a cutting shell having a shell wall with spaced apart exterior and interior shell surfaces (26, 28), a shell wall thickness therebetween, the shell having a curvature comprising at least a portion of a first hemisphere from an apex to a lower edge, the cutting shell being rotatable about a rotational axis (A-A) that extends through the apex, wherein at least one slit extends through the shell wall thickness; b) a plurality of cutting teeth, each having a primary tissue cutting surface, wherein the primary tissue cutting surface extends outwardly from the exterior surface of the shell; c) a ring secured to the shell lower edge, the ring having a ring thickness that extends from a ring proximal surface to a ring distal surface, a ring slot having a slot length and a slot depth, wherein the slot depth extends through the ring distal surface and at least partially through the ring thickness; d) a second blade comprising a second blade sidewall having a sidewall first end spaced from a sidewall second end, wherein the sidewall first end comprises a secondary tissue cutting surface, and wherein the sidewall second end is received within the ring slot; wherein e) a cam having opposed proximal and distal cam surfaces, wherein the cam is rotatably secured to the ring proximal surface adjacent to the shell lower edge, a ridge having a ramped surface extending from the cam distal surface, wherein the blade sidewall second end is in contact with the ridge ramped surface; and f) wherein rotation of the cam in either a clockwise or counterclockwise first direction causes the blade sidewall second end to ride up the ridge ramped surface thereby causing the secondary tissue cutting surface to extend through the at least one slit, and wherein rotation of the cam in an opposite second direction causes the blade sidewall second end to ride down the ridge ramped surface thereby causing the secondary tissue cutting surface to retract within the shell interior.