Unilateral external fixation device

• US 4,895,141 A
• Filed: 11/19/1987
• Issued: 01/23/1990
• Est. Priority Date: 04/26/1984
• Status: Expired due to Term

• Current Assignee: Orthotic Limited Partnership
• Original Assignee: Harrington Arthritis Research Center
• Inventors: Phillips, Mark, Weinstein, Allan M., Koeneman, James B., Hansen, Thomas M.
• Primary Examiner(s): Hafer, Robert A.
• Assistant Examiner(s): ROONEY, KEVIN
• Application Number:
  US07/122,397
• Time in Patent Office: 796 Days
• Field of Search: 128/92 Z, 128/92 ZZ, 128/92 ZY, 128/92 ZK, 128/92 ZW
• US Class Current: 606/54
• CPC Class Codes: A61B 17/6416 with non-continuous, e.g. hinged, pin-clamp connecting element A61B17/6425, A61B17/6441 take precedence
• CPC Class Codes: A61B 17/645 comprising a framework A61B17/6425, A61B17/6441 take precedence
• CPC Class Codes: A61B 17/66 Alignment, compression or distraction mechanisms

Abstract

A unilateral external fixation device comprises a distal frame and a proximal frame interconnected by a hinge formed of mating, partially spherical-shaped surfaces which permits relative movement of the distal frame and proximal frame. Each of the frames includes one or more pin clamps which mount half pins inserted with the proximal or distal segments of a fractured bone to immobilize the bone segments and permit reduction of the fracture. The focal point of the partially spherical-shaped surfaces of the hinge is positioned in direct alignment with the fracture, preferably in a vertical plane passing through the fracture transverse to the longitudinal axis of the bone, so that manipulation of one or both of the distal and proximal frames permits a relatively slight and precise movement of the bone segments connected thereto by the half pins to ensure proper reduction of the fracture.

Claims

1. An external fixation device for positioning and immobilizing the distal segment and proximal segment of a fractured bone to reduce the fracture, comprising:

a distal frame having means for clamping half pins insertable within the distal segment of the fractured bone, said distal frame being formed with a distal hinge element having an arcuate surface;

a proximal frame having means for clamping half pins insertable within the proximal segment of the fractured bone, said proximal frame being formed with a proximal hinge element having an arcuate surface matable with said arcuate surface of said distal hinge element of said distal frame;

means for interconnecting said distal hinge element with said proximal hinge element so that said mating arcuate surfaces thereof are movable relative to one another along a partially spherical-shaped surface defined by a radius of fixed length having an origin at approximately the center of the fracture to permit pivotal movement of said distal frame relative to said proximal frame for aligning the distal segment with the proximal segment of the fractured bone.

2. The external fixation device of claim 1 in which said distal frame and said proximal frame each include substantially non-cylindrical shaped rods formed with a non-cylindrical-shaped, central core of foam material and an outer wall of composite material.

3. The external fixation device of claim 2 in which said rods of said distal frame and proximal frame are elliptical or oval in shape.

4. The external fixation device of claim 1 in which said distal hinge element and said proximal hinge element are each substantially cup-shaped in cross section each having a convexly arcuate outer surface and a concavely arcuate inner surface, said concavely arcuate inner surface of said distal hinge element being slidable relative to said convexly arcuate outer surface of said proximal hinge element along said partially spherical-shaped surface defined by said radius of fixed length having an origin at approximately the center of the fracture to permit pivotal movement of said distal frame relative to said proximal frame.

5. The external fixation device of claim 4 in which said means for interconnecting said arcuate surface of said distal hinge element with said arcuate surface of said proximal hinge element comprises a hinge cap engagable with one of said convexly arcuate outer surface of said distal hinge element and said concavely arcuate inner surface of said proximal hinge element, a bolt insertable through said hinge cap and said distal and proximal hinge element s and a nut threadable onto said bolt for mounting said distal and proximal hinge elements in fixed relation to said cap.

6. The external fixation device of claim 1 in which said means for clamping half pins comprises:

a pin block formed with a threaded outer surface and an internal slot for receiving a rod portion of said distal frame or said proximal frame;

means for clamping said pin block to said distal frame or said proximal frame, comprising;

(i) a spacer insertable within said internal slot of said pin block, said spacer being formed with a first end engagable with said rod portion of said distal or proximal frames and a second end extending exteriorly of said internal slot in said pin block;

(ii) a clamping cap formed with a hollow interior defining a cylindrical wall terminating at a bearing surface, said cylindrical wall being formed with threads matable with said threaded outer surface of said pin block, said clamping cap being threaded onto said pin block so that said bearing surface contacts and forces said spacer against said rod portion of said proximal or distal frames to mount said pin block thereto;

a seat formed in said pin block;

pin clamping means movable means movable within said seat, said pin clamping means being formed with a throughbore defining a wall, said throughbore being adapted to receive a half pin;

means mounted in said pin block for contacting said pin clamping means and urging said wall of said throughbore against the half pin to clamp the half pin in position on said distal frame or said proximal frame.

7. The external fixation device of claim 6 in which said pin block is formed with a first bore and a second bore intersecting said first bore, said second bore defining an internal wall formed with threads, said pin clamping means comprising:

a projection mounted to said pin block within said first bore, said projection being formed with an arcuate surface facing said second bore;

a retainer insertable within said second bore, said retainer having an arcuate surface extending into said first bore and facing said arcuate surface of said projection, said arcuate surfaces of said retainer and said projection forming a seat;

a ball formed with a throughbore defining a cylindrical wall, a portion of said cylindrical wall being tapered radially inwardly, said ball being received within said seat and movable therein relative to said pin block;

a hollow sleeve insertable within said throughbore of said ball, said sleeve being formed with a radially inwardly tapering slotted end portion which mates with said radially inwardly tapered portion of said cylindrical wall formed in said bore, said sleeve being adapted to receive an end of a half pin;

a screw having a cylindrical stem connected to a head, said cylindrical stem being formed with external threads matable with said threaded second bore, said screw being threaded into said second bore so that said cylindrical stem forces said retainer against said ball, said tapered portion of said cylindrical wall of said ball being collapsed radially inwardly to clamp said slotted end portion of said sleeve against the half pin to retain the half pin within said pin block.

8. The external fixation device of claim 6 in which said pin block is formed with a threaded outer surface and an internal slot for receiving a rod portion of said distal or proximal frames, said means for clamping said pin block to said distal frame or said proximal frame comprising:

a spacer insertable within said internal slot of said pin block, said spacer being formed with a first end engagable with said rod portion of said distal or proximal frames and a second end;

a clamping cap formed with a hollow interior defining a cylindrical wall connected to a head portion, said head portion being fixedly mounted to said second end of said spacer, said cylindrical wall being formed with threads matable with said outer threaded surface of said pin block, said spacer being inserted within said internal slot and said clamping cap being threaded onto said pin block so that said first end of said spacer contacts said rod portion to mount said pin block onto said distal or proximal frame.

9. An external fixation device for positioning and immobilizing the distal segment and proximal segment of a fractured bone to reduce the fracture, comprising:

a distal frame having means for clamping half pins insertable within the distal segment of the fractured bone, said distal frame being formed with a distal hinge element having an arcuate surface;

a proximal frame having means for clamping half pins insertable within the proximal segment of the fractured bone, said proximal frame being formed with a proximal hinge element having an arcuate surface matable with said arcuate surface of said distal hinge element of said distal frame portion;

means for interconnecting said distal hinge element with said proximal hinge element so that said mating surfaces thereof are movable relative to one another along a partially spherical-shaped surface defined by a radius of fixed length having an origin at approximately the center of the fracture to permit pivotal movement of said distal frame relative to said proximal frame for aligning the distal segment with the proximal segment of the fractured bone;

compression-distraction means engagable with said pin clamp means of at least one of said distal and proximal frames for axially moving said pin clamp means relative to the longitudinal axis of the fractured bone, said pin clamp means axially moving one of the distal and proximal bone segments of the fractured bone connected thereto by half pins relative to the other of the distal and proximal bone segments.

10. The external fixation device of claim 9 in which said compression-distraction means comprises:

a threaded rod rotatably carried by said means for interconnecting said arcuate surface of said distal hinge element with said arcuate surface of said proximal hinge element;

a nut having internal threads matable with said threaded rod, said nut being movable axially along said threaded rod in response to rotation of said threaded rod;

yoke means interconnecting said nut with said pin clamp means of one of said distal and proximal frame portions, said nut contacting and moving said yoke means axially along said threaded rod, said yoke means in turn axially moving said pin clamp means and the distal or proximal bone segment connected to said pin clamp means by half pins.

11. The external fixation device of claim 10 in which said yoke means comprises a pair of spaced yoke elements connected by a leg member, each of said yoke elements having an upper end formed with a bore adapted to receive said threaded rod and a lower end formed with spaced arms adapted to straddle said distal or proximal frame portion, said yoke elements being spaced to capture said nut between said upper ends thereof and said pin clamping means between said lower ends thereof.

12. The external fixation device of claim 10 in which said distal frame and said proximal frame each include a rod portion connected to said distal hinge element and said proximal hinge element, respectively, said threaded rod being connected to one of said rod portions for mounting said compression-distraction means.

13. A method of positioning and immobilizing the distal segment and proximal segment of a fractured bone to reduce the fracture, comprising:

clamping one end of a half pin inserted within the distal segment of the fractured bone to a pin clamp carried by a distal frame of an external fixation device, said distal frame being formed with a distal hinge element having an arcuate surface;

clamping one end of a half pin inserted within the proximal segment of the fractured bone to a pin clamp carried by a proximal frame of said external fixation device, said proximal frame being formed with a proximal hinge element having an arcuated surface which mates with said arcuate surface of said distal hinge element for permitting pivotal movement therebetween;

positioning said distal hinge element and said proximal hinge element relative to the fracture so that said arcuate surface of said distal hinge element and said mating arcuate surface of said proximal hinge element pivot with respect to one another about a partially spherical-shaped surface defined by a radius of fixed length having its origin at the approximate center of the fracture of the bone so as to permit precise adjustment of the position of the distal segment at the fracture for alignment with the proximal segment.

14. The method of claim 13 in which said step of positioning said distal hinge element and said proximal hinge element comprises spacing said mating arcuate surfaces of said distal hinge element and said proximal hinge element at a distance from the center of the fracture of the bone which is approximately equal to the length of the radius having its origin at the center of the fracture.

15. The method of claim 13 in which said step of positioning said distal hinge element and said proximal hinge element comprises spacing said mating arcuate surfaces of said distal hinge element and said proximal hinge element at a distance from the center of the fracture of the bone in the range of about two inches to four inches.

16. The method of claim 13 in which said step of positioning said distal hinge element and said proximal hinge element comprises positioning the focal point of said arcuate surface of one of said distal hinge element and said proximal hinge element substantially coincident with a vertical plane extending through the center of the fracture of the bone transverse to the longitudinal axis of the bone.