1. A corpectomy cage, comprising:
an inner member having a cylindrical sidewall, a first end and a second end opposite the first end, the cylindrical sidewall having a circumferential groove;
an outer member having a cylindrical sidewall, a first end and a second end opposite the first end, the cylindrical sidewall having a circumferential groove, wherein the cylindrical side wall and the second end of the inner member is at least partially disposed within the cylindrical side wall and the second end of the outer member in a telescoping, non-load bearing engagement to allow axial movement between extendable and retractable positions, wherein the first end of the inner member is located opposite to the first end of the outer member; and
a cylindrical sleeve configured to bear axial loads on the cage and having a fixed length, a first end, a second end, a first lip extending radially inward proximate the first end of the sleeve, and a second lip extending radially inward proximate the second end of the sleeve, the sleeve fit over the outer member with the first lip engaging the circumferential groove on the inner member and the second lip engaging the circumferential groove on the outer member.
2. The corpectomy cage of claim 1 wherein the sleeve is snap fit onto the outer member.
3. The corpectomy cage of claim 1 wherein the sleeve comprises resilient sidewalls such that the sleeve can be snap fit over the inner and outer members.
4. The corpectomy cage of claim 1 wherein the inner member, outer member, and sleeve have a substantially round cross-section when assembled.
5. The corpectomy cage of claim 1 wherein the sleeve has an axial opening for receiving the inner member and outer member.
6. The corpectomy cage of claim 1 wherein the sleeve is selected from a set of sleeves each having a different length.
7. The corpectomy cage of claim 1 wherein the inner member and the outer member have a circular profile, and the sleeve has a C-shaped profile.
8. The corpectomy cage of claim 1 wherein the inner member comprises an end plate disposed at the first end thereof, the outer member comprises an end plate disposed at the first end thereof.
9. The corpectomy cage of claim 8 wherein each of the end plates comprises a perimeter groove configured to be engaged by a tool.
10. A corpectomy cage for use between a first vertebra and a second vertebra in place of removed intervertebral discs and at last a portion of a vertebral body of a third vertebra located between the first vertebra and the second vertebra, the corpectomy cage comprising:
a first segment with a cylindrical sidewall, a circumferential groove, and an end plate, the end plate configured to engage the first vertebra;
a second segment with a cylindrical sidewall, a circumferential groove, and an end plate, the end plate configured to engage the second vertebra;
a C-shaped cover with a fixed length, the cover having a first radial lip and a second radial lip extending inwardly and spaced apart from the first radial lip;
the first and second segments being slidably assembled; and
the cover removably mounted over the assembled first and second segments between the end plates so as to support physiologic loads on the cage, wherein the first radial lip engages the circumferential groove on the first segment and the second radial lip engages the circumferential groove on the second segment.
11. The corpectomy cage of claim 10 wherein the cover is snap fit onto one of the segments.
12. The corpectomy cage of claim 10 wherein the cover has resilient side walls.
13. The corpectomy cage of claim 10 wherein the cover is selected from a set of covers each having a different length.
14. The corpectomy cage of claim 10 wherein the assembled first and second segments have an adjustable length.
15. The corpectomy cage of claim 14 wherein the first and second segments are free from mechanical fasteners connecting the segments together.
16. The corpectomy cage of claim 10 wherein the cover is load bearing and the first and second segments are non-load bearing.
17. The corpectomy cage of claim 10 wherein the cage has an unobstructed internal cavity.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A self-driven synchronous DC-DC converter circuit, comprising:
an input circuit comprising a switching device configured for selectively generating a pulsed DC input voltage responsive to an input switch control signal, said pulsed DC input voltage comprising a plurality of DC voltage pulses;
an output circuit coupled to said input circuit, said output circuit comprising an active device having a device input node, a device output node, and a device control node, said device control node responsive to a control voltage for selectively varying a conductivity between said device input node and said device output node; and
a control circuit coupled to said device control node and configured for generating said control voltage responsive to said pulsed DC input voltage;
wherein said control voltage is synchronized with said pulsed DC input voltage, and varies non-linearly during an interval between said DC voltage pulses for selectively reducing said conductivity in accordance with a non-linear function following each of said voltage pulses.
2. The converter circuit of claim 1, wherein said control voltage varies exponentially during said interval.
3. The converter circuit of claim 1, wherein said control circuit is a reactive network.
4. The converter circuit of claim 1, said active device further having at least one capacitive element between said device control node and said device output node, and wherein said control circuit comprises a resistor-capacitor network.
5. The converter circuit of claim 4, wherein said active device is a MOS transistor.
6. The converter circuit of claim 4, said control circuit further comprising:
a switch having a switch control node and first and second switch nodes, said switch control node coupled to said device input node, and said first node coupled to a reference voltage, said switch device switching between a current blocking state and a current conducting state between said first and said second switch nodes responsive to said pulsed DC input voltage.
7. The converter circuit of claim 6, wherein said resistor-capacitor network is comprised of:
a first resistor coupled from said device output node to said device control node, and
an impedance network coupled to from said device control node to said second switch node, said impedance network comprising one or more capacitive elements and one or more second resistor elements.
8. The converter circuit of claim 7, wherein said second resistor elements are connected in parallel with said capacitor elements.
9. The converter circuit of claim 8, wherein a capacitance of said capacitor elements is greater than a capacitance of said capacitive element in said active device.
10. The converter circuit of claim 8, wherein a resistance of said second resistor elements is greater than a resistance of said first resistor.
11. A method for converting a first DC voltage to a second DC voltage, comprising:
generating a pulsed DC input voltage responsive to an input switch control signal, said pulsed DC input voltage comprising a plurality of DC voltage pulses;
generating a control voltage at a device control node of an active device responsive to said pulsed DC input voltage;
selectively varying a conductivity between a device input node and a device output node of said active device in response to said control voltage; and
synchronizing said control voltage with said pulsed DC input voltage, and varying said control voltage non-linearly during an interval between said DC voltage pulses for selectively reducing said conductivity in accordance with a non-linear function following each of said voltage pulses.
12. The method of claim 11, wherein varying step further comprises varying said control voltage exponentially during said interval.
13. The method of claim 11, wherein said generating step further comprises generating said control voltage using a reactive network.
14. The method of claim 11, further comprising providing an active device having at least one capacitive element between said device control node and said device output node, and wherein said generating step further comprises generating said control voltage by using said capacitive element and a control circuit comprising a resistor-capacitor network.
15. The method of claim 14, further comprising selecting a MOS transistor for said active device.
16. The method of claim 14, further comprising selecting a switch for said control circuit, said switch having a switch control node and first and second switch nodes, said switch control node coupled to said device input node, and said first node coupled to a reference voltage, said switch device switching between a current blocking state and a current conducting state between said first and said second switch nodes responsive to said pulsed DC input voltage.
17. The method of claim 16, further comprising selecting for said resistor-capacitor network a first resistor coupled from said device output node to said device control node, and an impedance network coupled to from said device control node to said second switch node, said impedance network comprising one or more capacitive elements and one or more second resistor elements.
18. The method of claim 17, further comprising arranging said second resistor elements and said capacitor elements in parallel.
19. The method of claim 18, further comprising selecting said capacitor elements to have a capacitance greater than a capacitance of said capacitive element in said active device.
20. The method of claim 18, further comprising selecting said second resistor elements to have a resistance greater than a resistance of said first resistor.