A surgical tool for removing a block of material from a body, the surgical tool comprising a tool head including: (a) an elongated support element having a direction of elongation and configured for insertion along a first slit parallel to said direction of elongation into the material of the body; (b) characterized in that a first blade assembly includes: (i) a pair of arms (18a, 18b) having at least one cutting edge pivotally mounted relative to said support element so as to concomitantly rotate and cut about a first axis perpendicular to said direction of elongation, a plane passing through said support element parallel to both said direction of elongation and said first axis being referred to as a tool plane, and (ii) a first blade element pivotally mounted on said arms (18a, 18b) so as to be pivotable about a second axis parallel to, but displaced from, said first axis, said first blade element including a rear cutting edge, said first blade assembly assuming an insertion state in which said pair of bladed arms (18a, 18b) and said first blade element are deployed substantially in said tool plane, and a deflected state in which said first blade element is deployed to cut rearward in a direction forming an acute angle with said tool plane; (c) a second blade element pivotally mounted relative to said support element so as to be pivotable about a third axis substantially parallel to said first axis, said second blade element assuming an initial state in which said second blade element is deployed substantially in said tool plane and being pivotable to an inclined state in which said second blade element is arranged to cut in a direction inclined to said tool plane; and (d) a mechanical actuation arrangement including a plurality of spring elements and configured to resiliently bias said first blade assembly from said insertion state to said deflected state and to resiliently bias said second blade element from said initial state to said inclined state, wherein said first blade element has an upper surface, said mechanical actuation arrangement further including a resilient biasing arrangement deployed such that, when said pair of arms (18a, 18b) assume a final state projecting outward from said support element, said resilient biasing arrangement biases said first blade element to a position with said upper surface substantially parallel to said tool plane and wherein said resilient biasing arrangement includes a spring deployed between at least one of said arms (18a, 18b) and said first blade element. (a) an elongated support element having a direction of elongation and configured for insertion along a first slit parallel to said direction of elongation into the material of the body; (b) characterized in that a first blade assembly includes: (i) a pair of arms (18a, 18b) having at least one cutting edge pivotally mounted relative to said support element so as to concomitantly rotate and cut about a first axis perpendicular to said direction of elongation, a plane passing through said support element parallel to both said direction of elongation and said first axis being referred to as a tool plane, and (ii) a first blade element pivotally mounted on said arms (18a, 18b) so as to be pivotable about a second axis parallel to, but displaced from, said first axis, said first blade element including a rear cutting edge, said first blade assembly assuming an insertion state in which said pair of bladed arms (18a, 18b) and said first blade element are deployed substantially in said tool plane, and a deflected state in which said first blade element is deployed to cut rearward in a direction forming an acute angle with said tool plane; (i) a pair of arms (18a, 18b) having at least one cutting edge pivotally mounted relative to said support element so as to concomitantly rotate and cut about a first axis perpendicular to said direction of elongation, a plane passing through said support element parallel to both said direction of elongation and said first axis being referred to as a tool plane, and (ii) a first blade element pivotally mounted on said arms (18a, 18b) so as to be pivotable about a second axis parallel to, but displaced from, said first axis, said first blade element including a rear cutting edge, (c) a second blade element pivotally mounted relative to said support element so as to be pivotable about a third axis substantially parallel to said first axis, said second blade element assuming an initial state in which said second blade element is deployed substantially in said tool plane and being pivotable to an inclined state in which said second blade element is arranged to cut in a direction inclined to said tool plane; and (d) a mechanical actuation arrangement including a plurality of spring elements and configured to resiliently bias said first blade assembly from said insertion state to said deflected state and to resiliently bias said second blade element from said initial state to said inclined state,