Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-04-19
2001-08-07
Reip, David O. (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S062000, C606S067000
Reexamination Certificate
active
06270499
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns a device for fixation of bone fractures.
BACKGROUND OF THE INVENTION
When the head of the tibia is fractured, a load-bearing fracture surface must be reconstructed. The tibia is the only bone in the body where there is a continuous transition from a cubic bone with a load-bearing articular face into a tubular bone. In the area of the head of the tibia, load forces acting axially on the proximal articular tibia surfaces are converted continuously into a load on the tubular bone. No specific implants for these conditions have been available so far. An ideal load-bearing device for the head of the tibia must take these specific conditions into account.
In the related art various straight plates and angle plates as well as intramedullary nails are available for treating fractures of the head of the tibia. However, all these implants are designed for strong young bones and so far have been used mainly to treat accident-related fractures (sports and athletic accidents, labor accidents and traffic accidents).
However, due to aging of the general population and also the level of activity being pursued by the elderly population, the medical profession is increasingly confronted with the need for treating fractures in osteoporotic bones.
Osteoporosis is a growing problem in health care. The percentage of patients over 80 years of age has increased drastically, so there has also been a definite increase in fractures in patients with osteoporosis. Fractures of the proximal and distal tibia, the proximal and distal femur as well as the proximal humerus and the distal ulna and radius are of primary concern.
Previous osteosynthetic implants according to the related art are not very suitable for use with osteoporotic bones where the cortex is thin and spongy tissue is of an inferior quality. It is often difficult to correctly reposition fragments when the cortex is thin. Fixation and/or immobilization of a repositioned fracture is often extremely problematical in osteoporotic bones because osseous anchoring of the implants is difficult.
Regardless of bone quality, implants that arc truly optimized for treatment of proximal tibia fractures and in particular fractures of the head of the tibia have not been available. Only a few slightly modified plates and intramedullary nails are available.
European Patent No. 118,778 describes a locking nail with an elongated hollow body which is rounded at the proximal end and has an end with a widened head. In addition, at least two cross bores are provided in the body to accommodate one bone screw in each. The cross-sectional profile of the body forms a closed ring over its circumference.
Another locking nail made of solid material is disclosed in European Patent No. 447,824 FRIGG, where the proximal end part has a cross-sectional area with a trigonal shape in both the anterior and the posterior halves while being approximately quadratic as a whole. The distal end part has a cross-sectional area which is approximately trigonal in the anterior half and is approximately hemispherical in the posterior half. This specific design of the intramedullary nail according to this invention causes a high rotational stability in the proximal spongy part of the tibia while on the other hand permitting the most optimal possible adaptation to the geometry of the medullary space in the distal confocal part of the tibia.
Another locking nail is known from German Patent No. 43 41 677 SCHROEDER The nail body is rounded at the distal end and has a proximal concave end. Cross bores to accommodate one bone screw each are arranged in the nail body. In addition, the nail body is made of a solid material and has a funnel-shaped opening at least on one side of each cross bore.
SUMMARY OF THE INVENTION
The object of this invention is to create a device for fixation of bone fractures that can be used for optimal treatment of the following fractures even in patients with osteoporosis:
1. Fractures of the tibia shaft:
fractures of the proximal tibia shaft
ipsilateral fractures of the head of the tibia
2. Fractures of the head of the tibia:
fractures of the medial and lateral tibia plateau
fractures of the dorsal articular portions of the proximal tibia
ipsilateral tibia shaft fractures
3. Similar fractures of the distal or proximal femur (which meet the following conditions):
offering stable fixation even in osteoporosis patients due to optimal (axial) biomechanical positioning and fixation at a stable angle with a large contact area between bone and implant
easy and simple to handle (e.g., by avoiding posterior access in dorsoproximal fractures of the tibia head);
suitable for both right and left tibia and medial and lateral tibia plateau.
Another object of this invention is to be able to secure a bone fragment by means of a bone screw running across the axis of the intramedullary nail and tighten it against the intramedullary nail, so an intrafragment pressure can be produced.
This invention achieves in general the object formulated here with a device having the features of claim
1
.
An intramedullary nail in the head of the tibia is in the optimal position biomechianically as an axial implant. The intramedullary nail is secured in the medullary space of the tibia by means of pins. If the intramedullary nail is also tightened to the ventral cortex, the contact area between osteoporotic bone and implant is increased, and therefore the contact forces are reduced. The head of the tibia can be reconstructed using screws which are screwed into the intramedullary nail at a stable angle. Biomechanically, the intramedullary nail with the tibia head screws which are screwed into it at a stable angle thus assumes the function of an intramedullary angle plate. This combines the advantages of an axial implant (intramedullary nail) with the advantages of an implant at a stable angle (angle plate).
With the implant according to this invention in contrast with known osteosynthesis systems, the load-bearing element is first positioned in the biomechanical position and then is anchored in intact bone. The fracture is then repositioned on this fixedly anchored load-bearing clement and secured in a position at a stable angle. Since the fracture is secured in a fixedly anchored load-bearing element in a position at a stable angle, the quality of the bone (porosity) is of secondary importance.
A preferred refinement of this invention consists of the fact that the intramedullary nail has a bore running across the central axis in the area of the distal end as well as in the area of the proximal end in order to be able to lock the intramedullary nail in position.
The head of the intramedullary nail has one or preferably at least two or more bores whose axes may be parallel or divergent and which may have a thread.
The bone fixation means to be inserted in the intramedullary nail head is preferably a bone screw with a screw head and a screw shaft thread, said bone screw preferably having a continuous central channel. The thread near the screw head preferably has a smaller pitch than the thread of the screw shaft. An unthreaded section of shaft is preferably provided between the two different threads. It is thus possible to tighten a bone fragment secured with this bone screw to produce an intrafragment pressure.
The tip of this bone screw is preferably designed to be self-tapping and self-cutting. This simplifies the procedure.
Instead of bone screws, a blade or a plate may also be used as bone fixation means. The blade or the plate is preferably slotted or has a threaded bore to accommodate pins or screws.
This makes it possible to achieve an intramedullary screw connection at a stable angle.
REFERENCES:
patent: 5035697 (1991-07-01), Frigg
patent: 5122141 (1992-06-01), Simpson et al.
patent: 5531748 (1996-07-01), de la Caffiniere
patent: 5653709 (1997-08-01), Frigg
patent: 43 41 677 C1 (1995-07-01), None
patent: 0 447 824 A1 (1991-09-01), None
patent: WO 94/13219 (1994-06-01), None
patent: WO 95/26688 (1995-10-01), None
Däscher Peter
Leu Dieter
Pennie & Edmonds LLP
Reip David O.
Synthes (U.S.A.)
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