A system for guiding an instrument during a surgical procedure relative to an anatomy, comprising: a drive system adopted to be positioned relative to the anatomy, the drive system including: a drive section that moves along a drive axis to drive an instrument into the anatomy; a guide fixture positioned relative to the drive section and having a guide section substantially aligned with the drive axis; a plurality of guide members each defining a plurality of guide portions in section walls thereof and being moveably connected to the guide fixture, wherein each guide member is operable to move relative to the guide section along a set of radial axis (A-A'") transverse to the drive axis from a first position to a second position, wherein in the first position, the guide members are moved along the radial axes (A-A'") toward a center of the guide section and transverse to the drive axis, wherein in the second position the guide members are moved apart from one another along the radial axes (A-A'") and transverse to the drive axis; wherein the plurality of guide portions of each of the plurality of guide members are configured to cooperate with a sub-plurality of the plurality of guide portions of at least another two of the plurality of guide members in the first position to form a plurality of first guide areas defining a set of axes when at least a first sub-plurality of the plurality of guide members is in the first position; and a second guide portion defined by the guide section of the guide fixture having a plurality of second guide areas defining a set of axes, the axes being substantially coaxial with axes; wherein the plurality of first guide areas are coaxially aligned with the plurality of second guide areas when the first sub-plurality of guide members is in the first position to guide the instrument through the guide fixture. a drive section that moves along a drive axis to drive an instrument into the anatomy; a guide fixture positioned relative to the drive section and having a guide section substantially aligned with the drive axis; a plurality of guide members each defining a plurality of guide portions in section walls thereof and being moveably connected to the guide fixture, wherein each guide member is operable to move relative to the guide section along a set of radial axis (A-A'") transverse to the drive axis from a first position to a second position, wherein in the first position, the guide members are moved along the radial axes (A-A'") toward a center of the guide section and transverse to the drive axis, wherein in the second position the guide members are moved apart from one another along the radial axes (A-A'") and transverse to the drive axis; wherein the plurality of guide portions of each of the plurality of guide members are configured to cooperate with a sub-plurality of the plurality of guide portions of at least another two of the plurality of guide members in the first position to form a plurality of first guide areas defining a set of axes when at least a first sub-plurality of the plurality of guide members is in the first position; and a second guide portion defined by the guide section of the guide fixture having a plurality of second guide areas defining a set of axes, the axes being substantially coaxial with axes; wherein the plurality of first guide areas are coaxially aligned with the plurality of second guide areas when the first sub-plurality of guide members is in the first position to guide the instrument through the guide fixture.