Directional bone fixation device

• US 5,868,747 A
• Filed: 09/29/1997
• Issued: 02/09/1999
• Est. Priority Date: 12/02/1994
• Status: Expired due to Term

• Current Assignee: Biomet Incorporated (Zimmer Biomet Holdings, Inc.)
• Original Assignee: Johnson & Johnson Professional Company Incorporated (Johnson & Johnson)
• Inventors: Rogers, Laurel, Ochoa, Jorge A.
• Primary Examiner(s): Tucker, Guy V.
• Application Number:
  US08/939,558
• Time in Patent Office: 498 Days
• Field of Search: 606/73, 606/72, 606/54, 606/59, 606/61, 606/62, 606/63, 606/64, 606/76
• US Class Current: 606/300
• CPC Class Codes: A61B 17/68 Internal fixation devices , including fasteners and spinal fixators, even if a part thereof projects from the skin bone staples A61B17/0642
• CPC Class Codes: A61B 17/72 Intramedullary pins, nails or other devices A61B17/744 takes precedence
• CPC Class Codes: A61B 17/8625 Shanks, i.e. parts contacting bone tissue
• CPC Class Codes: A61B 17/869 characterised by an open form, e.g. wire helix
• CPC Class Codes: A61B 2017/00858 high friction, non-slip on handles A61B2017/00429
• CPC Class Codes: A61B 2017/8655 with special features for locking in the bone
• CPC Class Codes: A61F 2/0077 Special surfaces of prostheses, e.g. for improving ingrowth A61F2/30767 takes precedence
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• CPC Class Codes: A61F 2002/30836 knurled
• CPC Class Codes: A61F 2002/30838 Microstructures

Abstract

A bone fixation device such as a screw, pin, staple, cable or anchor has a microtextured contact surface to enhance installation or gripping characteristics, preferably by providing directional or anisotropic engagement. A surface texture comprised of patterned microfeatures imparts a roughness or actual mechanical engagement that prevents loosening. In different embodiments the features resemble an array of microbumps or pyramids, or anisotropic features such as rasp teeth, shingles, or slanted cantilevered fiber/rods. The use of microbumps present a smaller surface area when moving, while providing full area contact after the surfaces have relaxed or decompressed; installation may be effected with low force, while high static or resting friction prevents disengagement. Features with directional asymmetry or angled suspension allow the textured surface to slide or deflect when the fixation device moves in one direction, while presenting a high resistance to torque or linear motion when moved in the other direction. Manufacturing is achieved with ion beams or directional treatment with energetic radiation, and regular arrays of the microfeatures may be produced as stationary surface growth phenomena without the use of pattern masks or mechanical contact. One manufacturing apparatus rotates the fixation device about a longitudinal axis while it is irradiated along an oblique axis. A bone pin may have centrally-directed spurs that allow a multi-segment fracture to be securely pinned without threading. An elastic fastener body such as a screw or pin can be pre-tensioned to place the bone under a torsional or compressive load, or introduce strain at the healing site.

Claims

1. A method of bone fixation comprising forming an opening in a bone and inserting a fixation device in the opening, wherein the fixation device has a regular pattern of microfeatures on a bone contacting surface to effect high and low gripping characteristics, and wherein the step of inserting includes inserting with said low gripping characteristic such that said high gripping characteristic impedes disengagement of the fixation device.

2. A method of bone fixation, comprising the steps of;

forming an opening in a bone;

providing a bone fixation device having a fixation body which bears load along a load direction and a bone engaging surface having a plurality of microfeatures effective to contact the bone and being oriented to provide a first resistance to movement along one direction which is greater than a second resistance to movement along an opposite direction; and

inserting the bone fixation device in the opening such that resistance of the bone fixation device to insertion within the opening is less than resistance of the bone fixation device to removal from the opening.