Intramedullary nail

Details Intramedullary nail Intramedullary nail

1998-12-01

2001-03-06

Hirsch, Paul J. (Department: 3732)

Surgery

Instruments

Orthopedic instrumentation

Reexamination Certificate

active

06197029

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an intramedullary nail which can be suitably used for the purpose of fixating of joints and fracture locations, and more specifically for the purpose of arthrodesis of the ankle joint.
BACKGROUND TECHNOLOGY
Intramedullary nails are considered to be effective for internal fixation in the treatment of fractures, etc.; and recently, the use of such nails has become common. Specifically, in this method, the intramedullary nail is inserted into the bone marrow through the fracture site, and internal fixation is accomplished by passing at least two transfixation screws through screw holes formed in the intramedullary nail on both sides of the fracture site. In this method, however, depending on the location of the fracture, there may be cases in which the transfixation screws do not pass through.
Meanwhile, the destruction of the ankle joint is also common in patient with rheumatoid arthritis, etc. In such cases, arthrodesis of the ankle joint is considered to be effective. However, arthrodesis of the ankle joint is extremely difficult. Therefore, there are several conventionally utilized methods to fix these joints, and these include the following: 1) Methods in which cancellous screws are passed obliquely through the tibia and screwed into the talus or calcaneus. 2) Methods in which a plate is positioned along the talus, tibia and/or calcaneus and fixed using screws. 3) Methods in which pins are inserted in the tibia, talus and/or calcaneus, and then fixed to an external fixation device.
However, one problem that is common to these methods is that fixation is not rigid. In particular, they do no sufficiently control rotation and bending of the ankle joint. As a result, long period of immobilization without weight-bearing is required after surgery. Furthermore, in cases where an external fixation device is used, the pin insertion areas tend to become contaminated, so that repeated dressings is required.
Meanwhile, arthrodesis of the ankle joint, the use of conventional intramedullary nails is also considered. However, even if used in combination with transfixation screw, intramedullary nails do not sufficiently control rotation, pronation and supination, and dorsal and plantar flexion of the ankle-joint, particularly in patients with rheumatoid arthritis who have osteoporotic bone.
The present invention solves such problems. In short, the object of the present invention is to provide an intramedullary nail which makes it possible to obtain a firm fixation and which can easily perform operation.
DISCLOSURE OF THE INVENTION
In view of the object described above, the intramedullary nail of the present invention is characterized by the fact that a plurality of fins which protrude radially are formed on the outer circumference of the nail. Furthermore, the intramedullary nail of the present invention is characterized by the fact that in this construction, a screw hole is formed in the distal end, and a screw which has a large-diameter head part is screwed into this hole.
As a result of the adoption of the above-described means, the plurality of fins formed on the intramedullary nail act as a resistance to bone marrow and cortical bone, so that the movement of joints and the fracture can be prevented. In particular, the checking force with respect to any rotational force is strong; and in this regard, the present invention is extremely effective for arthrodesis of the joints. Furthermore, since these fins serve as substitutes for transfixation screws, the transfixation screws conventionally considered necessary are no longer needed.
Meanwhile, by the use of the screw with a large-diameter head which is screwed into the screw hole formed in the distal end of intramedullary nail, joints or bones clamped between the intramedullary nail and the screw can be tightened, thereby strengthen the fixing force. This fixing force can be adjusted to a wide extent by this tightening, which can be done even with preliminary pressure being applied.


REFERENCES:
patent: 3990438 (1976-11-01), Pritchard
patent: 4261351 (1981-04-01), Scherfel
patent: 5034013 (1991-07-01), Kyle et al.
patent: 5053035 (1991-10-01), McLaren
patent: 5454813 (1995-10-01), Lawes
patent: 5561437 (1971-02-01), Orlich
patent: 5766174 (1998-06-01), Perry
patent: 07222753 (1995-08-01), None

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