Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2001-04-24
2002-09-03
Philogene, Pedro (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S065000, C606S075000, C606S075000
Reexamination Certificate
active
06443954
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an intramedullary system for coupling bone portions across a fracture therebetween and, more specifically, to an intramedullary hip pinning system for rigidly interconnecting a femoral head portion to the remaining portion(s) of the femur and across a fracture or fractures in the area of the femoral neck or the shaft of the femur or combinations of such fractures.
BACKGROUND OF THE INVENTION
Bones are the hard parts of the skeleton found in vertebrates. 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.
A hip joint is a heavily stressed, load-carrying bone joint in the human body. It is essentially a ball and socket joint formed by the top of the femur which rotates within a cup-shaped aceta bulum at the base of the pelvis. When a break or fracture occurs adjacent to the top of the femur, the separated portions of the femur must be held together while healing occurs.
Historically, there have been a number of techniques used for treatment of fractures of the proximal end of the femur. 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 fracture fixation of the femur in its proximal end, including the Jewett Nail and Enders Nail.
Intramedullary nails have been inserted down the entire length of the femoral canal to provide a basis for the fixation. Threaded wires, standard bone screws or cannulated bone screws were then inserted through or along side the proximal nail and into the femoral head to provide fixation and rotational stability. The conventional nails did not provide compression of the proximal bone fragments against each other. Also, in longer nails the distal tip of the nail tended to rotate out of plane which forced the surgeon to locate the distal screw holes using fluoroscopy by a method commonly known as “free-handing”.
In the 1960s, the compression hip screw was introduced, resulting in improved fixation of the proximal femur. A lag screw assembly was inserted into the femoral head, a plate was attached to the lateral femur, and a compression screw joined the two. These implants provided a more rigid structure for the patient and allowed the surgeon to compress the fractured fragments against each other thereby decreasing the time to mobility. A number of compression hip screws have been introduced for fracture fixation about the proximal femur, including the Dynamic Hip Screw.
During implantation these compression hip screws require an incision at least equal to the length of the plate being used which extends operative time and blood loss. The side plate also creates a protuberance on the lateral side which provides an annoyance to the patient. Compression hip screw systems also fail to provide adequate compression in oseteogenic patients because the lag screw assembly threads fail to obtain sufficient purchase due to poor bone stock. Poor purchase is known to contribute to nonunion, malunion and the lag screw assembly eroding through the superior bone of the head of the femur in a condition known as “cut out”. Additionally, many patients are dissatisfied with the results of compression hip screw surgery because of the excessive sliding to a medial displacement and shortening position which leads to a change in gait.
Newer devices and inventions include additions to the nail and lag screw assembly to ease or 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. 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 a method of fixation which provides 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 difficult to retract should the nail or lag screw assembly require extraction. Further, the screws do not deploy through the cortical bone.
Other expanding devices provide surface contact with the intemal 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 difficult to retract should the nail or lag screw assembly require extraction and, also, do not 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, the cortical bone providing improved purchase for compression of a fracture, especially in osteogenic bone. These tangs are just as easily retracted should the device require explantation.
Approximately 10 years ago Howmedica (Rutherford, N.J., United States) was the first to produce the “Gamma Nail”, named for its similarity in shape to the Greek letter, and other designs soon followed. These devices combined desirable aspects of both intramedullary nails and compression hip screws. These intramedullary hip compression screws required a few small incisions, allowed capture of the most proximal fragments of the femur, rigid fixation of the most proximal and distal fragments, and a sliding lag screw assembly or anchor which fits within a barreled sleeve for allowing improved compression of the fragments as the patient ambulates and begins to bear weight on the fractured limb. The nails are typically held in place on the distal end through interference forces with the intramedullary canal and through the use of locking screws.
The Gamma Nail's shape accommodates the relative shape of the greater trochanter and femoral neck and head fragments, and the shape of the hip is therefore preserved. Nonunions are less frequent because bone-to-bone contact is maintained and the bulk of an intramedullary hip screw blocks excessive sliding. Intramedullary hip screws work best in reverse obliquity fractures, a fracture, in which compression hip screws are least effective.
Osteogenic bone still provides a poor medium for purchase of the lag screw assembly of the Gamma Nail inhibiting adequate compression and rotational stability. Longer nails continue to see the distal tip of the nail rotating out of plane forcing the surgeon tolocate the distal screw holes by the free-hand method. The free-handing technique leads to an increased surgical time and exposes the surgeon and patient to increased radiation dosages.
Clearly a need exists for a system which is superior to the, “gold standard,” of compression hip screws while minimizing the surgical insult to the human body. Such a system, as disclosed and claimed herein, includes a simple, effective and controllable fixation device which allows greater purchase of the lag screw assembly within the femoral head, improved compression across the fracture line, provides a means of rotational st
Bramlet Dale G.
Cosgrove Patrick J.
Sodeika John A.
Sterghos Peter M.
McHale & Slavin
Philogene Pedro
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