Threadform for medical implant closure

Abstract

A thread located on a cylindrical closure for an open headed medical implant. The thread has a leading surface and a trailing surface that both slope rearwardly from an interior edge to an exterior edge thereof.

1 . A medical implant having a head with a pair of spaced arms and an implant closure sized to be operably threadedly received between said arms; said closure having a threadform thereon that is sized and shaped to be threadedly received in a mating threadform on said arms; said closure has a direction of advancement along an axis of rotation relative to said head; said threadform comprising:
 a) a leading surface that has an inner edge and an outer edge;   b) a trailing surface that has an inner edge and an outer edge; and wherein   c) intersections of a plane passing through said axis of rotation with both said leading surface and said trailing surface slope rearwardly relative to the direction of advancement from the respective inner edges to the outer edges thereof; and   d) the leading surface outer edge and the trailing surface outer edge are spaced apart.   
     
     
         2 . The implant according to  claim 1  wherein:
 a) the intersection of said trailing surface with a plane passing through said axis of rotation is at a first angle of from about 1° to about 45° relative to a line perpendicular to said axis of rotation. 
 
     
     
         3 . The implant according to  claim 2  wherein:
 a) said first angle is between about 5° and 20°. 
 
     
     
         4 . The implant according to  claim 2  wherein:
 a) said first angle is between about 7° and 15°. 
 
     
     
         5 . The implant according to  claim 2  wherein:
 a) the intersection of said leading surface with a plane passing through said axis of rotation is at a second angle of from about 30° to about 75° relative to a line perpendicular to said axis of rotation. 
 
     
     
         6 . The implant according to  claim 2  wherein:
 a) said second angle is in the range from 40° to 50°. 
 
     
     
         7 . The implant according to  claim 1  wherein:
 a) said trailing and leading surfaces are nonparallel. 
 
     
     
         8 . A medical device comprising:
 a) a first implant having a head with a channel sized and shaped to receive a rod member and a pair of spaced arms on opposite sides of said channel;   b) a second closure implant for closing between said arms; said closure implant having an axis of rotation and a thread on an outer surface thereof; said thread being in a helical pattern on said closure implant and having a leading surface and a trailing surface; said leading surface having inner and outer edges and said trailing surface having inner and outer edges; intersections of both said leading surface and said trailing surface with a plane passing through said axis of rotation slope from respective inner to outer edges rearwardly with respect to a direction of advancement of said closure implant in closing said first implant;   c) the outer edges of the leading and trailing surfaces are spaced to increase the strength of the outermost part of the thread; and   d) each of said arms include a threadform on inner facing surfaces thereof sized and shaped to matingly and threadedly receive the thread of said closure implant;   
     
     
         9 . The device of  claim 8  wherein:
 a) the inner and outer edges of both said leading surface and said trailing surfaces are each spaced from the axis of rotation at substantially the same radius over substantially the entire length of the thread. 
 
     
     
         10 . The device of  8  wherein:
 a) said inner edges of both said leading and trailing surfaces are substantially spaced and said outer edges of both said leading and trailing surfaces are in close proximity to each other throughout the length of the thread such that the thread is generally triangular in cross-section. 
 
     
     
         11 . The device according to  10  wherein:
 a) said cross-section has the general shape of an obtuse triangle. 
 
     
     
         12 . In a medical implant having a head with a pair of spaced upright arms and a closure operably located between the arms, a thread positioned on the closure and being sized and shaped to be threadedly received in a mating thread located on the pair of upright arms; said thread having an axis of rotation with a leading surface and a trailing surface relative to advancement along the axis of rotation; the improvement comprising:
 a) said trailing surface having an inner and an outer edge; said trailing surface sloping rearwardly from the inner edge to the outer edge thereof; and said inner edge having a generally constant radius over an entire length of said thread, such that, as said closure is advanced and applies force on a bottom side thereof, said thread resists splaying of said arms; the leading surface and the leading surface having an outer edge that is spaced apart from the trailing surface outer edge.   
     
     
         13 . In a medical implant sized and
 shaped for closing between a pair of arms of a head of a bone screw and having a lower surface adapted to engage and apply pressure to a rod received in the head; said implant further having a cylindrical shaped outer surface with a thread wound in a helical pattern about said outer surface and wherein said thread has a leading surface and a trailing surface relative to advancement of the implant along an axis of rotation; the improvement comprising:   a) said trailing surface having an inner and an outer edge; any intersection of said trailing surface with a plane passing through the axis of rotation slopes rearwardly from an inner radius to an outer radius of said trailing surface over substantially the entire length of said trailing surface; the leading and having an outer edge that is spaced from the trailing surface outer edge.   
     
     
         14 . In a medical implant having a head with a pair of spaced arms and a closure for positioning between and closing between the arms, the closure having a thread located thereon that is operably received in a mating thread located on said spaced arms; said thread having a leading surface and a trailing surface relative to advancement about an axis of rotation; the improvement comprising:
 a) both said leading and trailing surfaces having respective inner and outer edges with the outer edges being spaced apart; said trailing surface sloping rearwardly from the inner edge to the outer edge thereof; said trailing surface and leading surface inner edges being spaced.   
     
     
         15 . The implant according to  claim 14  wherein:
 a) said cross-section is generally in the shape of an obtuse triangle. 
 
     
     
         16 . In a medical implant having a cylindrical shaped outer surface with a thread helically wound about said outer surface and wherein said implant is sized and shaped to be threadedly received between a pair of arms of a bone screw head and has a bottom surface adapted to abut against a rod received in said head; said thread having a leading surface and a trailing surface relative to advancement of the implant along an axis of rotation and further wherein both said trailing surface and said leading surface have respective inner and outer edges; the improvement comprising:
 a) said leading and trailing surfaces both sloping rearwardly from respective inner to outer edges thereof with the outer edges being spaced apart; said trailing surface and leading surface inner edges being spaced.   
     
     
         17 . In an orthopedic medical implant having a head with a pair of spaced arms and including a closure for operably closing between the arms, the closure having a thread thereon and the arms having a mating thread; said thread having a leading surface and a trailing surface relative to advancement about an axis of rotation; the improvement comprising wherein:
 a) both of the intersections of said leading surface and said trailing surface with a plane passing through the axis of rotation slope rearwardly from a radially inner edge to outer edge thereof;   b) a first angle between the leading surface intersection and a line perpendicular to the axis of rotation is substantially greater than a second angle between the trailing surface intersection and a line perpendicular to the axis of rotation; and   c) the leading and trailing surfaces have respective outer edges that are spaced apart.   
     
     
         18 . The implant according to  claim 17  wherein:
 a) said second angle is between about 1° and 45°. 
 
     
     
         19 . The implant according to  claim 18  wherein:
 a) said first angle is greater than 30°. 
 
     
     
         20 . The implant according to  claim 17  wherein:
 a) said first angle is in the range from about 30° to 45° and said second angle is in the range from about 5° to 20°. 
 
     
     
         21 . In a medical implant having a head with a pair of spaced arms and including a closure for closing between said arms; said closure having thereon a thread sized and shaped to be threadedly received in a mating thread on said arms; said thread having a leading surface and a trailing surface relative to advancement about an axis of rotation; the improvement comprising:
 a) said leading surface and said trailing surface being non-parallel;   b) an intersection of a plane with said trailing surface slopes rearwardly from an inner edge to an outer edge of said trailing surface; and   c) the leading and trailing surfaces have respective outer edges that are spaced apart.   
     
     
         22 . A medical implant closure having a threadform; said closure being adapted to be threadedly receivable in a second medical implant bone screw head between spaced arms wherein said closure has a direction of advancement along an axis of rotation relative to said head; said threadform comprising:
 a) a leading surface that has an inner edge and an outer edge;   b) a trailing surface that has an inner edge and an outer edge; and wherein   c) intersections of a plane passing through said axis of rotation with both said leading surface and said trailing surface slope rearwardly relative to the direction of advancement from the respective inner edges to the outer edges thereof; and   d) the outer edges of the leading and trailing surfaces are spaced apart.   
     
     
         23 . The closure according to  claim 22  wherein:
 a) said threadform is helically wound about said cylindrical shaped body. 
 
     
     
         24 . The closure according to  claim 22  wherein:
 a) said threadform is continuous. 
 
     
     
         25 . The closure according to  claim 22  wherein:
 a) said threadform is in a helical pattern, but is discontinuous. 
 
     
     
         26 . The closure according to  claim 22  further including:
 a) the second implant having a receiving thread on an inner surface thereof; said receiving thread being sized and shaped to matingly and threadably receive said threadform. 
 
     
     
         27 . A medical implant for locking a rod in a bone anchor, the implant comprising:
 a) a closure body;   b) the body having a helically wound thread with leading and trailing surfaces that slope rearwardly and outwardly and remain spaced apart at a crest thereof, and   c) the body having a central opening for receiving a tool, the opening being restricted at a lower end thereof to block the tool from extending therethrough.