Device for minimizing porosity in bone cement utilizing centrifugation and vacuum

• US 5,472,445 A
• Filed: 09/20/1993
• Issued: 12/05/1995
• Est. Priority Date: 09/20/1993
• Status: Expired due to Term

• Current Assignee: Zimmer Technology Incorporated (Zimmer Biomet Holdings, Inc.)
• Original Assignee: Zimmer Incorporated (Zimmer Biomet Holdings, Inc.)
• Inventors: Hoag, Steve, Yakimicki, Don, Case, Kirt
• Primary Examiner(s): Willse, David H.
• Application Number:
  US08/122,956
• Time in Patent Office: 806 Days
• Field of Search: 366/139, 494/32, 494/33, 494/39, 494/61, 606/92
• US Class Current: 606/92
• CPC Class Codes: A61B 17/8827 with filtering, degassing, venting or pressure relief means
• CPC Class Codes: A61F 2002/4685 by means of vacuum
• CPC Class Codes: B01F 2101/20 Mixing of ingredients for bone cement
• CPC Class Codes: B01F 33/5011 portable during use, e.g. hand-held

Abstract

The mixing apparatus and method of this invention combines centrifugation and vacuum mixing to provide a device for the centrifugation of cement under a partial vacuum for the reduction of porosity within bone cement. The results of centrifugation under a vacuum are an improvement over the results achieved in standard centrifugation or standard vacuum mixing techniques. The device includes a receptacle which is spun rapidly about an axis under a partial vacuum. Creating a partial vacuum within the receptacle causes the air bubbles trapped within the cement to grow in size. The centrifugation causes the larger air bubbles to migrate through the cement toward the axis of rotation. Centrifugation works especially well under a partial vacuum due to the increased size of the air bubbles, in that larger bubbles migrate easier and quicker than smaller bubbles. Under centrifugation, the smaller air bubbles are compressed to such a degree that they become insignificant within the cement.

Claims

1. A device for minimizing the porosity in bone cement caused by air entrapped in the cement, the device including a cylinder configured to hold a predetermined quantity of uncured bone cement, the cylinder being configured for placement within a cement delivery device, a motor means connected to the cylinder for rotating the cylinder about a central axis, and vacuum means operatively associated with the cylinder for creating a vacuum within the cylinder as the motor means rotates the cartridge about the central axis, wherein the vacuum means includes a second cylinder and a weighted plunger, the second cylinder being connected to the motor means, the plunger being shiftable within the second cylinder and forming an airtight seal with interior sidewalls of the second cylinder, the second cylinder having a first end which is vented to ambient atmosphere and a second end which is in air flow communication with the first mentioned cylinder, said plunger being shiftable from a first position adjacent the second end and a second position adjacent said first end as said motor rotates the first and second cylinder to create a vacuum in said first cylinder.

2. A device for minimizing the porosity in bone cement caused by air entrapped in the cement, the device including a first cylinder configured to hold a predetermined quantity of uncured bone cement, the first cylinder being configured for placement within a cement delivery device, a motor means connected to the first cylinder for rotating the first cylinder about a central axis wherein the first cylinder is positioned radially to the central axis, and vacuum means operatively associated with the first cylinder for creating a vacuum within the first cylinder as the motor means rotates the first cylinder about the central axis, the vacuum means including a second cylinder and a weighted plunger, the second cylinder being connected to the motor means, the plunger being shiftable within one of said first and second cylinders and forming an airtight seal with interior sidewalls thereof, each of the first and second cylinders having a first end and a second end, said plunger being shiftable from a first position adjacent the first end and a second position adjacent said second end as said motor rotates the first and second cylinder to create a pressure less than ambient adjacent said first end.

3. The device of claim 2 wherein the plunger is carried within said second cylinder, the first end of the second cylinder being connected in flow communication with the first cylinder, the second end of said second cylinder including a vent, and as said plunger shifts from its first position toward its second position the plunger creates a pressure less than ambient in the first ends of the first and second cylinders.

4. The device of claim 2 wherein the plunger is carried within the first cylinder adjacent a quantity of uncured bone cement carried within the first cylinder adjacent the first end, the second end of the first cylinder including a vent, and as said motor rotates the first and second cylinder, the weighted plunger is shifted from a position adjacent the first end toward a position adjacent the second end thereby creating an area of reduced atmosphere adjacent the first end of the first cylinder, wherein the quantity of uncured bone cement carried within the first cylinder is subjected to the reduced atmosphere.