Bone cement removal and apparatus

• US 5,462,552 A
• Filed: 07/15/1994
• Issued: 10/31/1995
• Est. Priority Date: 11/20/1992
• Status: Expired due to Fees

• Current Assignee: Kiester P. Douglas
• Original Assignee: Kiester P. Douglas
• Inventors: Kiester, P. Douglas
• Primary Examiner(s): Hafer, Robert A.
• Assistant Examiner(s): KENEALY, DAVID
• Application Number:
  US08/275,939
• Time in Patent Office: 473 Days
• Field of Search: 606/86, 606/99, 606/92, 606/93, 606/94, 606/100, 606/127, 606/128, 606/129, 606/27-31, 607/98, 607/99
• US Class Current: 606/92
• CPC Class Codes: A61B 17/16 Bone cutting, breaking or removal means other than saws, e.g. Osteoclasts; Drills or chisels for bones; Trepans arthroscopic bone cutters A61B17/320016; dental implant drills potentially for other surgical use A61C8/0089; bone grinders A61F2/4644, A22C17/06; A61B17/1662 takes precedence over all other subgroups except A61B17/17
• CPC Class Codes: A61B 17/8847 for removing cement from a bone cavity using surgical bone chisels, drills, mills, rasps, reamers or scrapers A61B17/16; using laser A61B18/20; using ultrasonic surgical instruments A61N7/00
• CPC Class Codes: A61B 18/082 Probes or electrodes therefor
• CPC Class Codes: A61F 2002/465 using heating means
• CPC Class Codes: A61F 2002/4681 by applying mechanical shocks, e.g. by hammering

Abstract

An improved instrument for removing thermoplastic bone cement by applying a heater tip of heating wire to the cement to melt the bone cement inserting the hot heater tip into the bone cement, allowing it to cool embedded in the bone cement and to pull the instrument and, through the embedded heater tip, pull the bone cement from the bone.

Claims

1. An instrument assembly for removing, as a single piece, a mass of previously formed thermoplastic bone cement from a bone in a patient,

said instrument assembly being an elongate structure having proximal and distal ends and being constructed and configured to be grasped by the user during use, said elongate structure comprising;

a heater tip assembly forming the proximal end of the elongate structure, said heater tip assembly being constructed and configured to be inserted proximate a bone of a patient from which a mass of thermoplastic bone cement is to be removed and comprising;

an elongate probe having proximal and distal ends; and

an electrical resistivity heater tip rigidly mounted on the proximal end of said elongate probe;

a striker secured to the elongate probe distally from the heater tip;

an electrical system for supplying electricity to the heater tip assembly for heating the heater tip; and

hammer means, mounted for movement distally relative to the heater tip assembly, when the instrument is in use, for impacting the striker, the striker being so constructed and secured as part of the instrument assembly that force applied to the striker is applied through the instrument assembly to the heater tip assembly, said hammer means being constructed and configured for applying a removal force to the striker and through the instrument to the heater tip assembly;

the electrical system comprising electrical conductors and means for selectively connecting electricity through said electrical conductors to the heater tip, the electrical resistance of said conductors being so low relative to the electrical resistance of the heater tip that heating occurs substantially only in the heater tip;

the electrical system being constructed, configured and connected, when the instrument assembly is in use, as to heat the heater tip to a temperature sufficient to soften thermoplastic bone cement;

the instrument being so constructed and configured as to permit the user to force the heated tip into the mass of thermoplastic bone cement to be removed from the patient and, after permitting the thermoplastic bone cement to cool to a solid, to impact the striker with the hammer means for apply a pulling force through the heater tip to the solid mass of thermoplastic bone cement in which the heater tip is embedded to thereby remove said mass of thermoplastic bone cement substantially as one piece from the patient;

said elongate structure comprising an elongate shaft having proximal and distal ends, the proximal end secured to the probe and the shaft extending from the distal end of the probe, and wherein the hammer means is slidably received on said shaft and the hammer means and probe, respectively, comprise electrical contacts for applying electricity to the heater tip only when said hammer means is positioned adjacent the distal end of said shaft.

15. The instrument assembly of claim 1 wherein the heater tip comprises a molly-bolt sleeve and an enlarged bead at the end of the probe, the molly-bolt sleeve being slidably received on the probe closely adjacent the bead.

2. An instrument assembly for removing, as a single piece, a mass of previously formed thermoplastic bone cement from a bone in a patient,

said instrument assembly being an elongate structure having proximal and distal ends and being constructed and configured to be grasped by the user during use, said elongate structure comprising;

a heater tip assembly forming the proximal end of the elongate structure, said heater tip assembly being constructed and configured to be inserted proximate a bone of a patient from which a mass of thermoplastic bone cement is to be removed and comprising;

an elongate probe having proximal and distal ends; and

an electrical resistivity heater tip rigidly mounted on the proximal end of said elongate probe;

a striker secured to the elongate probe distally from the heater tip;

an electrical system for supplying electricity to the heater tip assembly for heating the heater tip; and

hammer means, mounted for movement distally relative to the heater tip assembly, when the instrument is in use, for impacting the striker, the striker being so constructed and secured as part of the instrument assembly that force applied to the striker is applied through the instrument assembly to the heater tip assembly, said hammer means being constructed and configured for applying a removal force to the striker and through the instrument to the heater tip assembly;

the electrical system comprising electrical conductors and means for selectively connecting electricity through said electrical conductors to the heater tip, the electrical resistance of said conductors being so low relative to the electrical resistance of the heater tip that heating occurs substantially only in the heater tip;

the electrical system being constructed, configured and connected, when the instrument assembly is in use, as to heat the heater tip to a temperature sufficient to soften thermoplastic bone cement;

the instrument being so constructed and configured as to permit the user to force the heated tip into the mass of thermoplastic bone cement to be removed from the patient and, after permitting the thermoplastic bone cement to cool to a solid, to impact the striker with the hammer means for apply a pulling force through the heater tip to the solid mass of thermoplastic bone cement in which the heater tip is embedded to thereby remove said mass of thermoplastic bone cement substantially as one piece from the patient;

said heater tip comprising nichrome wire of about 14 to about 18 gauge having first and second ends, said ends being so secured as to be carried by the proximal end of the probe, at least a portion of said wire extending generally perpendicularly from the axis of the probe.

3. An instrument assembly for removing, as a single piece, a mass of previously formed thermoplastic bone cement from a bone in a patient,

said instrument assembly being an elongate structure having proximal and distal ends and being constructed and configured to be grasped by the user during use, said elongate structure comprising;

a heater tip assembly forming the proximal end of the elongate structure, said heater tip assembly being constructed and configured to be inserted proximate a bone of a patient from which a mass of thermoplastic bone cement is to be removed and comprising;

an elongate probe having proximal and distal ends; and

an electrical resistivity heater tip rigidly mounted on the proximal end of said elongate probe;

a striker secured to the elongate probe distally from the heater tip;

an electrical system for supplying electricity to the heater tip assembly for heating the heater tip; and

hammer means, mounted for movement distally relative to the heater tip assembly, when the instrument is in use, for impacting the striker, the striker being so constructed and secured as part of the instrument assembly that force applied to the striker is applied through the instrument assembly to the heater tip assembly, said hammer means being constructed and configured for applying a removal force to the striker and through the instrument to the heater tip assembly;

the electrical system comprising electrical conductors and means for selectively connecting electricity through said electrical conductors to the heater tip, the electrical resistance of said conductors being so low relative to the electrical resistance of the heater tip that heating occurs substantially only in the heater tip;

the electrical system being constructed, configured and connected, when the instrument assembly is in use, as to heat the heater tip to a temperature sufficient to soften thermoplastic bone cement;

the instrument being so constructed and configured as to permit the user to force the heated tip into the mass of thermoplastic bone cement to be removed from the patient and after permitting the thermoplastic bone cement to cool to a solid, to impact the striker with the hammer means for apply a pulling force through the heater tip to the solid mass of thermoplastic bone cement in which the heater tip is embedded to thereby remove said mass of thermoplastic bone cement substantially as one piece from the patient;

said heater tip comprising a pair of tip supports extending from the proximal end of the probe and heater wire forming a bridge portion between the tip supports, the bridge portion being so constructed and configured as to form a cutting edge portion.

4. The instrument assembly of claim 3 wherein the bridge portion of the wire has a smaller transverse cross-section than the transverse cross-section of the tip supports.

5. The instrument assembly of claim 3 wherein the tip supports are spaced from about 0.2 to about 0.4 inch apart and are substantially straight.

6. An instrument assembly for removing, as a single piece, a mass of previously formed thermoplastic bone cement from a bone in a patient,

said instrument assembly being an elongate structure having proximal and distal ends and being constructed and configured to be grasped by the user during use, said elongate structure comprising;

a heater tip assembly forming the proximal end of the elongate structure, said heater tip assembly being constructed and configured to be inserted proximate a bone of a patient from which a mass of thermoplastic bone cement is to be removed arid comprising;

an elongate probe having proximal and distal ends; and

an electrical resistivity heater tip rigidly mounted on the proximal end of said elongate probe;

a striker secured to the elongate probe distally from the heater tip;

an electrical system for supplying electricity to the heater tip assembly for heating the heater tip; and

hammer means, mounted for movement distally relative to the heater tip assembly, when the instrument is in use, for impacting the striker, the striker being so constructed and secured as part of the instrument assembly that force applied to the striker is applied through the instrument assembly to the heater tip assembly, said hammer means being constructed and configured for applying a removal force to the striker and through the instrument to the heater tip assembly;

the electrical system comprising electrical conductors and means for selectively connecting electricity through said electrical conductors to the heater tip, the electrical resistance of said conductors being so low relative to the electrical resistance of the heater tip that heating occurs substantially only in the heater tip;

the electrical system being constructed, configured and connected, when the instrument assembly is in use, as to heat the heater tip to a temperature sufficient to soften thermoplastic bone cement;

the instrument being so constructed and configured as to permit the user to force the heated tip into the mass of thermoplastic bone cement to be removed from the patient and, after permitting the thermoplastic bone cement to cool to a solid, to impact the striker with the hammer means for apply a pulling force through the heater tip to the solid mass of thermoplastic bone cement in which the heater tip is embedded to thereby remove said mass of thermoplastic bone cement substantially as one piece from the patient;

said elongate structure comprising an elongate shaft having proximal and distal ends, the proximal end secured to the probe extending distally from the distal end of the probe, and wherein the hammer means is slidably received on said shaft and comprises the electrical system, said electrical system comprising one or more electric cells, said striker comprising means at the distal end of the shaft for stopping the slidable movement of said hammer means.

7. The instrument assembly of claim 6 wherein said hammer means and probe, respectively, comprise electrical contacts for applying electricity to the heater tip only when said hammer is positioned adjacent the distal end of the probe.

8. The instrument assembly for removing mass of thermoplastic bone cement of claim 7 wherein the heater tip comprises nichrome wire of about 14 to about 18 gauge having first and second ends, said ends being so secured as to be carried by the proximal end of the probe, at least a portion of said wire extending generally perpendicularly from the axis of the probe.

9. The instrument assembly of claim 7 wherein the heater tip comprises a pair of tip supports extending from the proximal end of the probe and heater wire forming a bridge portion between the tip supports, the bridge portion being so constructed and configured as to form a cutting edge portion.

10. The instrument assembly of claim 9 wherein the bridge portion of the wire has a smaller transverse cross-section than the transverse cross-section of the tip supports.

11. The instrument assembly of claim 6 wherein the tip supports are spaced from about 0.2 to about 0.4 inch apart and are substantially straight.

12. The instrument assembly of claim 6 wherein the probe has an axis and wherein the tip extensions extend substantially parallel to the axis of the probe.

13. The instrument assembly of claim 6 wherein the probe has an axis and wherein the tip extensions extend generally transversely to the axis of the probe.

14. The instrument assembly of claim 6 wherein the heater supports comprise means on the surface thereof and extending outwardly to provide greater gripping power.

16. A self-contained thermoplastic bone cement removal system comprising, in combination:

an elongate probe having proximal and distal ends, the proximal end constructed and configured to be inserted into a bone containing such cement to be removed;

a heater tip substantially rigidly mounted in and extending from the proximal end of the probe;

a hammer shaft connected to the distal end of the probe, electric means comprising electric cells and means for selectively connecting said cells electrically to the heater tip for heating the heater tip to a temperature sufficient to soften the cement to be removed, and means for exerting a removal force through the probe and the heater tip and to the cement to be removed, the means for exerting a removal force comprising a plurality of said electric cells bundled together and slidably mounted on said hammer shaft to form a hammer, the probe, heater tip, electric means and force exerting means being constructed and configured to selectively heat the heater tip to a temperature sufficient to soften said bone cement and, after permitting the bone cement to cool to a solid mass, to apply through the probe a pulling removing force to the heater tip embedded in the cement for removing such mass of cement from such bone.

17. A method for removing as a single piece a mass of thermoplastic bone cement formed previously in a bone from said bone comprising the steps of:

a) heating by electrical current flow through a resistivity electrical heater loop to a temperature sufficient to soften a portion of the previously formed thermoplastic bone cement mass to be removed, said heater loop being substantially rigidly mounted to and extending from the end of an elongate probe, said loop being heated substantially independently of the probe;

b) inserting the heated heater loop into the previously formed mass of thermoplastic bone cement by melting only a portion of the previously formed mass of thermoplastic bone cement;

c) allowing the heater loop to cool in the melted portion of the previously formed mass of thermoplastic cement to form a solid mass comprising the melted and cooled and the unmelted portions of previously formed thermoplastic bone cement with the heater loop embedded therein; and

thereafter

d) pulling the heater loop thereby removing substantially all of the solid mass formed of said melted and cooled and unmelted portions of bone cement as a single mass.