Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2001-04-25
2002-12-03
Lucchesi, Nicholas D. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S067000
Reexamination Certificate
active
06488684
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an intramedullary nail system for reducing and fixing bone portions across a fracture therebetween providing a means of fixation through the use of tangs, screws or a combination of both.
BACKGROUND OF THE INVENTION
In its most basic construct bones are formed of a relatively soft, spongy cancellous material surrounded by a much harder cortex. The cancellous bone yields under relatively low loading, while the much more dense cortical bone supports much higher loading. There have been a number of techniques used historically for treatment of fractures of the femur, humerus or tibia (referred to as the long bones). In early parts of this century, patients were merely placed in bed-or in traction for prolonged periods, frequently resulting in deformity or death.
In the 1930s, the Smith-Peterson nail was introduced. This device was inserted into the intramedullary canal of the femur resulting in immediate fixation of hip fractures, early mobilization of the patient, and a lower morbidity and mortality. A number of nails have been introduced for intramedullary fracture fixation of long bones, including the Jewett Nail and Enders Nail.
Later intramedullary nails increased in diameter and surgeons/inventors began to experiment with cross section designs and radii of curvature along the nail's length. Since the femur curves slightly along its length, it was preferred that the nails have a similar long radius of curvature of, for example 50 inches. These nails were inserted down the entire length of the femoral canal to provide a basis for the construct. Fixation methods for certain types of fractures often required the nail to bear a portion of the patient's weight during the recovery period. Threaded wires, standard bone screws or cannulated bone screws were then inserted through or along side the nail and into the outer cortex to provide enough fixation and rotational stability to bear weight during recovery.
As these intramedullary nails became longer other problems occurred. In longer nails the distal tip of the nail tends to rotate out of plane which forces the surgeon to target the distal screw holes using fluoroscopy by a method commonly known as “free-handing”. Under this technique the surgeon utilizes fluoroscopic images in search of perfectly circular screw holes. Once found a mark is made on the patient, an incision is made and a pathway cleared to the cortical bone. A dimple is placed on the lateral cortex to reduce “drill walking” and the hole is then drilled and a screw inserted. Adjustments to this procedure are quite common; even to those skilled in the art of free handing.
Numerous patents, both domestic and foreign, have been granted citing devices which reduce the complications associated with distal screw targeting. The methods of accomplishing this task are varied, but the results are the same: Very few of the ideas have been developed and marketed as useful products. The majority of surgeons still return to free handing because there is a perceived time savings. Therefore, external methods for distal screw targeting have not gained favor.
DESCRIPTION OF THE PRIOR ART
Newer devices and inventions explored additions to the nail to eliminate the need to locate the distal screw holes and improve the fixation. These newer devices are commonly classified as “expanding devices” and expand in size after placement to fill the intramedullary cavity. In the early 1980s, the Brooker-Wills Nail came on the scene and others soon followed. Freedland, U.S. Pat. Nos. 4,632,101, 4,862,883 and 4,721,103, Chemello, U.S. Pat. No. 6,077,264, and Davis, U.S. Pat. No. 5,057,103, describe methods of fixation which provide points which contact the internal cortical wall. In these patents a mechanism is actuated deploying arms or anchor blades through the cancellous bone to contact the inner cortical wall. These methods are complex and the arms are difficult to retract should the nail or lag screw assembly requires extraction. These arms do not deploy through the cortical bone.
Other expanding devices provide surface contact with the internal cortical wall resulting in a wedge effect. Kurth, U.S. Pat. No. 4,590,930, Raftopoulos, U.S. Pat. No. 4,453,539, and Aginski, U.S. Pat. No. 4,236,512, among others have described mechanisms which deploy or expand with a molly bolt concept. These methods are complex and the devices are difficult to retract should the nail require extraction. Neither do these devices deploy through the cortical bone.
Bolesky, U.S. Pat. No. 4,275,717, was the first to discuss engagement within the cortical wall. However, Bolesky's invention does not address controlled penetration into the wall and required permanent implantation of the actuation rod. In addition, Bolesky does not address the fundamental problem of the actuation rod's protrusion extramedullarly into the surrounding musculature.
In U.S. Pat. Nos. 5,976,139 and 6,183,474B1, Bramlet et al describe a surgical anchor which has deployable tangs. These tangs are simple in design, internally positioned, yet easily deployed into, and if desired through, cortical bone providing improved purchase for compression of a proximal femur fracture, especially in osteogenic bone. These tangs are just as easily retracted should the device require explantation.
SUMMARY OF THE INVENTION
The intramedullary nail system according to this invention is especially suitable for installation within the medullary canal of a fractured long bone, such as a femur, humerus, or tibia and subsequently interlocking the nail and bone thereby preventing axial translation and axial rotation.
The intramedullary nail is, preferably, roughly circular in cross section and elongated although any number of cross sectional shapes may be used. The nail is, preferably, cannulated and anatomically curved to fit the shape of a bone.
The cannulated intramedullary nail allows passage of one or more anchoring tang assemblies. These anchoring tang assemblies are inserted from the proximal end and telescoped through the axial bore towards the distal end by a insertion/deployment/retraction instrument. An alternate embodiment has a retracted tang mounted on a tang assembly that is permanently placed within the intramedullary nail and is deployed and retracted by the above mentioned instrument.
The proximal end of the nail contains a securing arrangement for a tool for driving and extracting the nail. The tool advantageously cooperates with a slot in the proximal end of the nail so that the desired angular disposition of the nail is indicated and easily maintained during insertion of the nail.
When the intramedullary nail is placed into position, the anchoring tang assembly is actuated to deploy the tangs outwardly from their stowed position through the portals and into the cortical bone. The interlocking of the intramedullary nail to the cortical shell of the long bone may be achieved, at least once, using at least one screw or at least one tang assembly. In the preferred embodiment, several tang assemblies would be positioned longitudinally within the nail based on the fracture location and the surgeon's assessment for proper fixation. The tangs are deployed to any desired position thereby achieving a desired fixation and rotation prevention based upon the quality of the bone. Should the system require additional load carrying capability, cortical screws may be placed to further secure the nail with the surrounding bone.
The anchoring tang assembly contains arcuate shaped tangs that are permanently attached to the tang assembly body. These tangs are initially formed into a prescribed position for storage. As the assembly is actuated, the tangs deploy and are formed into their final shape through interaction with the portal in the nail.
The end cap preferably contains a coating of ultra-high molecular weight polyethylene (UHMWPE) within the threads. This provides constant positive engagement between the end cap external threads and the intramedullary nail internal threads
Bramlet Dale G.
Cosgrove Patrick J.
Sodeika John A.
Sterghos Peter M.
Lucchesi Nicholas D.
McHale & Slavin P.A.
Priddy Michael B.
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