Bone fixation system with low profile fastener

Abstract

A low profile orthopedic device is used to fix and stabilize bones to correct anomalies in skeletal structure occurring naturally or by trauma. Bone screws are screwed into bones by application of torque. Clamps are movably attached to the screws. Each clamp includes a compression ring. A connecting rod connects several screws through slots in the clamps. The clamps are tightened to hold the rod and the heads in a pre-selected position by linear movement of the compression rings.

1. An orthopedic device for stabilizing bones including at least one bone pin, at least one elongated connector rod and at least one link interconnecting the elongated connector rod and bone pin, each bone pin comprising a shank for penetrating a bone with a head on one end, a clamp universally connected to said head for locking said pin to a link, said clamp having a body including exterior walls forming an inner receptacle enclosing said head, a first compression ring surrounding the outside of said exterior walls in one position, a slot through said exterior walls of said body opposite said receptacle, said slot slidably contacting said link, said first compression ring linearly movable along said outside of said exterior walls to a second position by application of a force consisting of a linear force along a longitudinal axis of said body whereby said exterior walls of said receptacle and said slot exert compressive force securely locking said clamp about said head and said link, said link having an arm with one end and a journal at the other end, said journal has a split sleeve and a second compression ring surrounding the outside of said split sleeve, said second compression ring being movable linearly along said split sleeve by application of a force consisting of a linear force along an axis of said link to move said sleeve from an open position to a closed position, said open position permitting adjustment of said connector rod in said journal and said closed position securing said connector rod and journal together. 
     
     
       2. An orthopedic device of  claim 1  wherein said head of said bone pin is approximately spherical and said receptacle has a complementary shape whereby said bone pin and said clamp may be universally oriented. 
     
     
       3. An orthopedic device of  claim 1  wherein said shank is formed with an exterior helical thread. 
     
     
       4. An orthopedic device of  claim 1  wherein said slot is adjacent said receptacle whereby said head and said link are in close proximity producing a low profile. 
     
     
       5. In an orthopedic system for stabilizing and fixing bones across a discontinuity, at least two bone screws, an elongated connector rod of a length to span the discontinuity, and at least one link, each said bone screw comprising a threaded shank with a head, said head including a means for applying torque to said shank and a means for attaching one end of said link, the other end of said link formed as a clamp, said clamp having an elongated body with exterior walls, a slot extending across said exterior walls of said clamp, said connector rod movably disposed in said slot, a compression ring surrounding said exterior walls in one position linearly along said exterior walls to a second position by application of a force consisting of a linear force along a longitudinal axis of said link whereby said exterior walls exert a compressive force in said slot when said compression ring is moved by said linear force to said second position. 
     
     
       6. In an orthopedic system of  claim 5  wherein said connector rod is slidably engaged in said slot when said compression ring is in said one position, said connector rod is held in said slot when said compression ring is in said second position. 
     
     
       7. In an orthopedic device for stabilizing bones comprising in combination a bone pin having a first end and a second end, said first end constructed and arranged as a shank portion for securement to a bone, said second end constructed and arranged as a head portion, a clamp universally connected to said head portion of said bone pin, said clamp having an elongated body with exterior walls, a slot extending across said exterior walls, said slot constructed and arranged to accept a rod member, a compression ring surrounding said exterior walls, said compression ring linearly traversable along said exterior walls between a first position and a second position by a force consisting of a linear force, whereby traversal of said compression ring from said first position to said second position compresses said clamp to substantially fix said clamp and said rod to said bone pin in a predetermined orientation, the improvement comprising:
 at least one annular bulge positioned along the length of said exterior walls of said clamp to provide a change in the external diameter along the length thereof, said at least one annular bulge constructed and arranged to cooperate with said compression ring to apply compressive forces to said clamp for immobilizing at least one of the connections between said clamp and said rod or said clamp and said bone pin.   
     
     
       8. The orthopedic device for stabilizing bones of claim 7 wherein said compression ring includes at least one inner annular ridge constructed and arranged to engage said at least one annular bulge in an overlapping manner while said compression ring is in said second position, whereby engagement of said bulge and said ridge applies compressive forces to said clamp for immobilizing the connections between said clamp and said rod with respect to said bone pin. 
     
     
       9. The orthopedic device for stabilizing bones of claim 7 wherein the at least one annular bulge is constructed and arranged to cooperate with said compression ring to apply compressive forces to said clamp for immobilizing the connections between said clamp and said rod, the at least one annular bulge constructed and arranged to cooperate with said compression ring to apply compressive forces to said clamp for immobilizing the connections between said clamp and said bone pin, said compression ring constructed and arranged to progressively engage said annular bulge, whereby said connections may be immobilized one at a time. 
     
     
       10. The orthopedic device for stabilizing bones of claim 9 wherein said compression ring includes at least one inner annular ridge constructed and arranged to engage the at least one annular bulge in an overlapping manner while said compression ring is in said second position. 
     
     
       11. The orthopedic device for stabilizing bones of claim 7, wherein the first position is defined when the compression ring is adjacent the head portion of the bone pin. 
     
     
       12. The orthopedic device for stabilizing bones of claim 7 wherein said bone pin is a bone screw wherein said first end includes at least one helical thread for penetrating and engaging a bone and wherein said head portion is substantially spherical in shape. 
     
     
       13. An orthopedic device for stabilizing bones comprising:
 a bone pin having a first end and a second end, said first end constructed and arranged as a shank portion for penetrating securement to a bone, said second end constructed and arranged as a head portion;   a clamp universally connected to said head portion of said bone pin for securing said bone pin to a rod or link member, said clamp having an elongated body with exterior walls, said exterior walls including at least one annular bulge to provide a change in the external diameter of said exterior walls, a slot extending across said exterior walls, said slot constructed and arranged to accept said rod or said link member;   a compression ring surrounding said exterior walls, said compression ring linearly traversable along said exterior walls between a first position and a second position by application of a force consisting of a linear force along a longitudinal axis of said clamp, whereby traversal of said compression ring from said first position to said second position causes said compression ring to cooperate with said at least one annular bulge to apply compressive forces to said clamp to immobilize at least one of the connections between said clamp and said rod or link member or said clamp and said bone pin.   
     
     
       14. The orthopedic device for stabilizing bones of claim 13 wherein said compression ring includes at least one inner annular ridge constructed and arranged to engage said at least one annular bulge in an overlapping manner while said compression ring is in said second position, whereby engagement of said at least one bulge and said at least one ridge applies compressive forces to said clamp for immobilizing at least one of said connections. 
     
     
       15. The orthopedic device for stabilizing bones of claim 13 wherein said at least one annular bulge is constructed and arranged to cooperate with said compression ring to apply compressive forces to said clamp for immobilizing at least one of said connections. 
     
     
       16. The orthopedic device for stabilizing bones of claim 15 wherein the at least one annular bulge is constructed and arranged to cooperate with said compression ring while said compression ring is in said second position to immobilize the connection between said clamp and said bone pin said second bulge constructed and arranged to cooperate with said compression ring to immobilize the connection between said clamp and said rod or link member while said compression ring is in said second position, whereby said compression ring may independently engage said first or said second bulges during translation thereof. 
     
     
       17. The orthopedic device for stabilizing bones of claim 15 wherein said compression ring includes at least one inner annular ridge constructed and arranged to engage the at least one annular bulge in an overlapping manner while said compression ring is in said second position, whereby engagement of said annular bulge and said annular ridge applies compressive forces to said clamp for immobilizing said connections. 
     
     
       18. The orthopedic device for stabilizing bones of claim 17 wherein the first position is defined when the compression ring is adjacent the head portion of the bone pin. 
     
     
       19. The orthopedic device for stabilizing bones of claim 13 wherein said bone pin is a bone screw wherein said first end includes at least one helical thread for penetrating and engaging a bone and wherein said head portion is at least partially spherical in shape. 
     
     
       20. An orthopedic kit for stabilizing bones comprising:
 at least one bone pin having a first end and a second end, said first end constructed and arranged as a shank portion for penetrating securement to a bone, said second end constructed and arranged as a head portion;   a clamp universally connected to said head portion of each said bone pin for securing said bone pin to a rod or a link, said clamp having an elongated body with exterior walls, a slot extending across said exterior walls, said slot constructed and arranged to slidably accept said rod or said link;   a first compression ring surrounding said exterior walls of said clamp, said first compression ring linearly traversable along said exterior walls between a first position and a second position by a force consisting of a linear force along a longitudinal axis of said clamp, said first position permitting adjustment of said rod or link, said second position compressing said clamp to immobilize said rod or link with respect to said bone pin;   at least one link having an arm on one end and a journal at the other end, said journal having a split sleeve and a second compression ring surrounding an outer surface of said split sleeve, said second compression ring being movable linearly along said split sleeve by application of a force consisting of a linear force along a longitudinal axis of said link to move said sleeve from an open position to a closed position, said open position permitting adjustment of said connector rod in said journal and said closed position securing said connector rod and said journal together;   at least one elongated connector rod constructed and arranged to cooperate with said slot or said journal.   
     
     
       21. The orthopedic kit for stabilizing bones of claim 20 wherein said clamp includes at least one annular bulge positioned along the length of said exterior walls thereof to provide a change in the external diameter of said clamp, said at least one annular bulge constructed and arranged to cooperate with said first compression ring to apply compressive forces to said clamp for immobilizing the connections between said clamp and said rod or said link with respect to said bone pin. 
     
     
       22. The orthopedic kit for stabilizing bones of claim 21 wherein said exterior walls of said clamp include two or more annular bulges to provide a change in the external diameter along the length of said exterior walls, said two or more annular bulges constructed and arranged to cooperate with said first compression ring to apply compressive forces to said clamp for immobilizing the connections between said clamp and said rod or said link with respect to said bone pin. 
     
     
       23. The orthopedic kit for stabilizing bones of claim 22 wherein a first of said two or more annular bulges is positioned at a first end of said clamp and second of said two or more annular bulges is positioned at second end of said clamp, said first bulge constructed and arranged to cooperate with said first compression ring while said first compression ring is in said second position to immobilize the connection between said clamp and said bone pin said second ring constructed and arranged to immobilize the connection between said clamp and said rod or said link while said compression ring is in said second position. 
     
     
       24. The orthopedic kit for stabilizing bones of claim 22 wherein said first compression ring includes at least one inner annular ridge constructed and arranged to engage at least one of said two or more annular bulges in an overlapping manner while said first compression ring is in said second position, whereby engagement of said bulge and said ridge applies compressive forces to said clamp for immobilizing the connections between said clamp and said rod or said link with respect to said bone pin. 
     
     
       25. The orthopedic kit for stabilizing bones of claim 24 wherein said first compression ring includes two or more inner annular ridges, at least one of said ridges constructed and arranged to fit between said two or more annular bulges of said clamp while said compression ring is in said first position and at least one of said ridges constructed and arranged to engage at least one of said two or more annular bulges in an overlapping manner while said compression ring is in said second position to provide compressive forces to said clamp. 
     
     
       26. The orthopedic kit for stabilizing bones of claim 20 wherein said bone pin is a bone screw wherein said first end includes at least one helical thread for penetrating and engaging a bone and wherein said head portion is substantially spherical in shape. 
     
     
       27. A method of using an orthopedic device to stabilize bones across a discontinuity comprising the steps of:
 providing a first bone pin having a first end and a second end, said first end constructed and arranged as a shank portion for penetrating securement to a bone, said second end constructed and arranged as a head portion;   connecting a first clamp member to said head portion of said first bone pin for universal movement therebetween, said first clamp member having an elongated body with exterior walls, a first compression ring surrounding said exterior walls, said first compression ring located in a first position, a first slot extending across said exterior walls, said first slot constructed and arranged to accept a rod member;   securing said shank portion of said first bone pin to a first bone portion on a first side of said discontinuity;   providing a second bone pin having a first end and a second end, said first end constructed and arranged as a shank portion for penetrating securement to a bone, said second end constructed and arranged as a head portion;   connecting a second clamp member to said head portion of said second bone pin for universal movement therebetween, said second clamp member having an elongated body with exterior walls, a second compression ring surrounding said exterior walls, said second compression ring located in a first position, a second slot extending across said exterior walls, said second slot constructed and arranged to accept a rod member;   securing said shank portion of said second bone pin to a second bone portion on a second side of said discontinuity;   placing a rod member in said first and said second slots, whereby said rod member extends across said discontinuity;   applying a force consisting of a linear force along the longitudinal centerline of said first clamp member for traversing said first compression ring to a second position along said exterior walls of said first clamp member to compress said first clamp member to substantially fix said first clamp and said rod member in a predetermined orientation with respect to said first bone pin;   applying a force consisting of a linear force along the longitudinal centerline of said second clamp member for traversing said second compression ring to a second position along said exterior walls of said second clamp member to compress said second clamp member to substantially fix said second clamp member and said rod member in a predetermined orientation with respect to said first bone pin;   whereby said bones are stabilized across said discontinuity.   
     
     
       28. The method of using an orthopedic device to stabilize bones across a discontinuity of claim 27 wherein said first and said second bone pins are bone screws wherein said first end of each includes at least one helical thread for penetrating and engaging a bone and wherein said head portion of each is substantially spherical in shape. 
     
     
       29. The method of using an orthopedic device to stabilize bones across a discontinuity of claim 27 wherein said exterior walls of said first and said second clamp each include at least one annular bulge to provide a change in the external diameter along the length of said exterior walls, said at least one annular bulge constructed and arranged to cooperate with each said respective compression ring to apply compressive forces to said respective clamp for immobilizing the connections between each said respective clamp and said rod with respect to each said respective bone pin. 
     
     
       30. The method of using an orthopedic device to stabilize bones across a discontinuity of claim 29 wherein said first and said second compression ring each include at least one inner annular ridge constructed and arranged to engage said at least one annular bulge of a respective clamp in an overlapping manner while each said respective compression ring is located in said second position, whereby engagement between said respective bulges and said ridges apply compressive forces to said respective clamp for immobilizing the connections between said respective clamp and said rod with respect to said respective bone pin. 
     
     
       31. An apparatus comprising:
 a bone screw having a threaded shaft and a screw head;   a clamp body having a receptacle sized to accommodate the head of the bone screw with the threaded shaft extending downwardly out of the receptacle; and   a compression ring around exterior walls of the clamp body and movable along the exterior walls from an open position to a closed position, the compression ring including an annular flange at the upper edge thereof, the open position defined when the compression ring is moved towards the receptacle.   
     
     
       32. The apparatus of claim 31 wherein the screw head is spherical. 
     
     
       33. The apparatus of claim 32 wherein the receptacle is configured to receive the spherical screw head. 
     
     
       34. The apparatus of claim 31 wherein the receptacle is slotted. 
     
     
       35. The apparatus of claim 31 wherein the clamp body has annular bulges which engage annular ridges on the inside of the compression ring with the compression ring in the closed position. 
     
     
       36. The apparatus of claim 31 wherein the connection between the screw and the clamp body is a universal connection and the orientation of the screw relative to the clamp body is adjustable with the compression ring in the open position and the orientation between the screw and the clamp body is fixed with the compression ring in the closed position. 
     
     
       37. The apparatus of claim 31 wherein the clamp body further comprises a slot to receive a connector rod. 
     
     
       38. The apparatus of claim 37 wherein the slot has upper and lower longitudinal ridges to grip the connector rod. 
     
     
       39. The apparatus of claim 37 wherein the position of the rod in the slot is adjustable with the compression ring in the open position and is fixed with compression ring in the closed position. 
     
     
       40. An apparatus comprising:
 a bone screw having a threaded shaft and a screw head;   a clamp body having a receptacle sized to accommodate the head of the bone screw with the threaded shaft extending out the bottom of the clamp body, the clamp body having a slot to receive a rod;   a compression ring around exterior walls of the clamp body and movable along the exterior walls from an open position in which the position of the screw relative to the clamp body is adjustable to a closed position in which the position of the screw relative to the clamp body is fixed; and   a retainer which extends across and covers the slot, the retainer remaining rotationally stationary with respect to the clamp body during relative movement of the clamp body and the compression ring.   
     
     
       41. The apparatus of claim 40 wherein the retainer is a ring. 
     
     
       42. The apparatus of claim 41 wherein the retainer snaps into a groove on the clamp body. 
     
     
       43. The apparatus of claim 41 wherein the retainer is a clip. 
     
     
       44. The apparatus of claim 43 wherein the ends of the clip seat into a groove of the clamp body. 
     
     
       45. An apparatus comprising:
 a bone screw having a threaded shaft and a screw body;   a clamp body having a lower portion defining a receptacle sized to accommodate the head of the bone screw and an upper portion sized to accommodate a rod, the clamp body defining a first diameter near the receptacle and a second diameter near the upper portion, the first diameter being less than the second diameter;   a compression ring around exterior walls of the clamp body and movable along the exterior walls from an open position in which the orientation of the screw is adjustable relative to the clamp body and a closed position in which the orientation of the screw is fixed relative to the clamp body, the open position defined when the compression ring is moved towards the receptacle; and   a retainer for holding a connector rod and the clamp body together.   
     
     
       46. The apparatus of claim 45 wherein the retainer is a set screw retainer. 
     
     
       47. The apparatus of claim 45 wherein the clamp body includes a bore for receiving a rod. 
     
     
       48. The apparatus of claim 47 wherein the clamp body includes a threaded passage which intersects the bore. 
     
     
       49. The apparatus of claim 48 wherein the threaded passage is configured to receive a set screw retainer. 
     
     
       50. The apparatus of claim 48 further including a set screw retainer receivable in the threaded passage for holding a rod disposed in the bore and the clamp together. 
     
     
       51. An apparatus comprising:
 a bone screw having a head at one end thereof;   a clamp body having a receptacle for receiving the head of the bone screw, the receptacle being transitionable between a first state and a second state;   a retainer engageable with the clamp body to hold a connector rod in a relative position with respect to the clamp body; and   a ring member operably associated with the clamp body and repositionable from a first position to a second position, the first position defined when the ring member is adjacent the receptacle wherein:
 when the ring member is in the first position, the receptacle is in the first state and the bone screw is axially adjustable relative to the receptacle, and 
 when the ring member is in the second position, the receptacle is in the second state and the bone screw is fixed relative to the receptacle. 
   
     
     
       52. The apparatus of claim 51 wherein the clamp body includes a saddle for retaining a connector rod. 
     
     
       53. The apparatus of claim 51 wherein the ring member is slidably disposed on an outer surface of the clamp body. 
     
     
       54. The apparatus of claim 51 wherein the clamp body includes a slot such that opposing walls of the clamp body are repositionable towards and away from each other. 
     
     
       55. The apparatus of claim 54 wherein when the ring member is in the second position, the opposing walls of the clamp body are urged towards each other and frictionally engage the head of the bone screw. 
     
     
       56. The apparatus of claim 51 wherein the retainer is a clip. 
     
     
       57. The apparatus of claim 51 wherein the retainer is a set screw. 
     
     
       58. An apparatus comprising:
 a bone screw having a head at one end thereof;   a clamp body having a receptacle for receiving the head of the bone screw, the receptacle transitionable between a first state and a second state;   a retainer engageable with the clamp body;   a slot defined between the receptacle and the retainer for receiving a connector rod, the retainer holding the connector rod in the slot; and   a ring member operably associated with the clamp body such that when the ring member is in a first position the bone screw is axially adjustable relative to the receptacle, and when the ring member is in a second position the bone screw is fixed relative to the receptacle, the first position defined when the ring member is adjacent the receptacle of the clamp body.   
     
     
       59. The apparatus of claim 58, wherein the clamp body includes a saddle, the saddle and the retainer defining the slot. 
     
     
       60. The apparatus of claim 58, wherein when the ring member is in the second position, the receptacle frictionally engages the head of the bone screw. 
     
     
       61. The apparatus of claim 58, wherein the receptacle includes opposing walls that are repositionable towards and away from each other. 
     
     
       62. The apparatus of claim 51, wherein the opposing walls frictionally engage the head of the bone screw when the ring member is in the second position. 
     
     
       63. The apparatus of claim 58, wherein the retainer is a clip. 
     
     
       64. The apparatus of claim 58, wherein the retainer is a set screw. 
     
     
       65. The apparatus of claim 58, wherein the ring member is disposed on an outer surface of the clamp body. 
     
     
       66. The apparatus of claim 58, wherein the clamp body includes a slot such that opposing walls of the clamp body are repositionable. 
     
     
       67. The apparatus of claim 31, wherein the bone screw is pivotable relative to the clamp body when the compression ring is in the open position. 
     
     
       68. The apparatus of claim 31, wherein said compression ring includes at least one annular ridge and the clamp body includes at least annular bulge, the annular ridge and the annular bulge engage in an overlapping manner while said compression ring is in said second position, whereby engagement of the annular bulge and the annular ridge applies compressive forces to said clamp for immobilizing said connections. 
     
     
       69. The apparatus of claim 31, wherein the annular flange extends radially outward. 
     
     
       70. A method of using an orthopedic device to stabilize bones across a discontinuity, comprising:
 providing a first bone pin assembly, the first bone pin assembly including a first bone screw having a threaded shaft and a screw head, a first clamp body having a receptacle at one end and a first slot at an opposing end, the receptacle sized to accommodate the head of the first bone screw with the threaded shaft extending downwardly out of the receptacle, and a first compression ring around exterior walls of the first clamp body and movable along the exterior walls between an open position and a closed position, the first compression ring including an annular flange at the upper edge thereof, the open position defined when the first compression ring is adjacent the receptacle such that the first bone screw is pivotable relative to the first clamp body;   securing the threaded shaft of the first bone pin assembly to a first bone portion on a first side of the discontinuity;   placing a rod member in the first slot, whereby the rod member extends across the discontinuity; and   repositioning the first compression ring from its open position to its closed position.   
     
     
       71. The method of using an orthopedic device to stabilize bones across a discontinuity of claim 70 wherein the exterior wall of the first clamp body includes at least one annular bulge cooperative with the first compression ring to apply compressive forces to the first clamp body for immobilizing the connection between the first clamp body and the rod with respect to the first bone screw. 
     
     
       72. The method of using an orthopedic device to stabilize bones across a discontinuity of claim 70, further comprising a second bone pin assembly, the second bone pin assembly including a second bone screw having a threaded shaft and a screw head, a second clamp body having a receptacle at one end and a second slot at an opposing end, the receptacle sized to accommodate the head of the second bone screw with the threaded shaft extending downwardly out of the receptacle, and a second compression ring around exterior walls of the second clamp body and movable along the exterior walls between an open position and a closed position, the second compression ring including an annular flange at the upper edge thereof, the open position defined when the second compression ring is adjacent the receptacle such that the second bone screw is pivotable relative to the second clamp body. 
     
     
       73. The method of using an orthopedic device to stabilize bones across a discontinuity of claim 72, further including:
 securing the threaded shaft of the second bone pin assembly to a second bone portion on a second side of the discontinuity; and   repositioning the second compression ring from its open position to its closed position.