Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2001-02-27
2002-06-04
Smith, Jeffrey A. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C411S411000, C411S415000
Reexamination Certificate
active
06398786
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/HR98/00004 which has an international filing date of Jun. 17, 1998, which designated the United States of America.
BACKGROUND FIELD OF THE INVENTION
The invention pertains to the area of bone reconstruction in orthopaedic surgery and traumatology and it will find its application in the management of “pseudoarthrosis defects” in which a bone fragment is missing due to a bone defect. The bone fragment must be replaced by a transplant in order to facilitate a successful healing process. Such bone defects are usually consequences of a major trauma (for example gunshot wounds). They are also seen in open fractures for which a surgical procedure is required to remove a destroyed bone fragment, also following infections (osteomyelitis), requiring the removal of bone sequesters, and finally after the removal of bone tumours or cysts. Besides the aforementioned “pseudoarthrosis defect”, the area also encompasses the so called “avascular pseudoarthroses” in which there is a lack of viable bone cells in the area of the fracture as a result of bone devascularisation due to a radical surgical procedure, so that the healing process falls to occur (although the bone edges may be in contact). That is why a method of osteoinduction, including autologous bone transplant is also applied for these cases.
DESCRIPTION OF THE PRIOR ART
The purpose of a bone transplant is of two kinds:
1. It represents a medium for the appositional growth of bone cells from the edges of a bone defect. For this reason, and owing to its faster revascularisation, a spongy structure is more suitable than the homogenous one.
2. A transplant should have the local osteoinductive effect, which can only be found in a viable tissue contaning the living bone cells (osteoblast) which generate a new bone by the secretion of osteoid—protein into which calcium hydroxyapatit is deposited, thus forming a mineral, solid inorganic part of the bone.
The basic technical problem is how to obtain a transplant of a highest possible quality (with the highest degree of viability), which will produce strong osteoinduction using the effect of the living transplanted cells (osteoblast cells). In addition the above mentioned transplant, the bone morphogenic protein induction method, using the bone morphogenic protein (BMP) extracted from the ox-bone, is becoming increasingly more popular. Some other methods, involving locally altered growth factors, are currently in the stage of experimental research work. Although none of these cells are the living cells, BMP placed locally into the traumatised area stimulates the growth of the neighbouring cells and induces more intensive bone formation.
In my previous patent application submitted to the State Office for Intellectual Property on Oct. 9, 1997, the reference number P970539A, I presented the static and dynamical method of the mechanical induction of the periosteal reactive bone growth. The former method is the one using conus screws with a self-tapping tip which provides for a much simpler procedure, since its application does not require any subsequent stimulation. It has been found that the optimum result is achieved by a wedge-shaped screw placed at an angle of 7°. However, the width of the upper part of the opening corresponds only to the diameter of initial part of the screw. The latter gradually widens so that the final diameter of the upper part of the screw is over 0.5 mm bigger than the diameter of the its diameter at the entry. Thus, as it keeps penetrating deeper into the bone, the screw behaves as a wedge which overstrains the bone and pushes it laterally. This results in an osseous reaction, induced during the period of 4 to 8 weeks on the surfaces around the screw. These newly ossified surfaces are then removed by a chisel and transferred to the operative field in the area of the bone defect.
The methods for the surgical management of bone defect involve free bone transplants, the Ilizarov method of segment transplantation and microsurgical vascularised bone transplant. Free bone transplants methods are the most numerous, the simplest for application and therefore the most widely used ones. They comprise:
1. Autologous spongioplasty (the recipient's own cancellous bone—red bone marrow) which is widely accepted as the best osteoinduction material since it contains its own viable cells, and is of a spongy structure. It is usually taken from the pelvis (crista iliaca).
2. Corticospongioplasty—besides the internal, spongy part of the bone, this method also uses the external, solid, cortical part of the bone. The cortical part itself is less valuable as an osteoinduction medium, since it contains a low osteoblast count, and by its structure it is a homogenous, solid bone (which becomes dead after the transplantation), so that at a later stage it has to be totally turnovered by new cells from the neighbouring bone tissue. However, its advantage lies in the fact that it has very good mechanical hardness. It is usually taken from the pelvis area or from the medium third of the fibula.
3. Homologous spongioplasty (human cancerous bone taken from a bone bank) is being abandoned (AIDS, hepatitis, reaction to foreign proteins, infection etc.) and is being replaced by the use of artificial osseous tranplants.
4. Transplantation of an artificial bone. This method is gaining in popularity owing to its major advantage which lies in the fact that the transplanted tissue is not the recipient's own bone, which reduces the surgical trauma sustained by the recipient. A shortcoming of this method lies in the fact that these transplants do not contain viable cells, but they serve as a spongy medium for the implantation of the neigbouring cells, so that the healing process is much slower and of a much lower quality than with the application of autologous spongioplasty. This group consists of two types of transplants. The first group are the transplants originating from biological tissue (bovine spongiosis, collagen, collar minerals and so on). The second group is relative to transplants of inorganic origin (hydroxiapatit). Many of these are protected under different names such as Bio-Oss® (Geistlich AG, Switzerland), Osteovit® (B. Braun Melsungen AG), and others.
5. Decortication of Judet (M. E. Mueller and all, Manual of Internal Fixation, Springer-Verlag, Third Ed. 1991,720).
6. BMP (bone morphogenic protein) osteoinduction (OP-1™ striker® BIOTECH).
7. Periosteum transplantation is mentioned only sporadically in literature and it is described in all insignificant number of cases. It is not widely used due to the uncertainty regarding the subsequent bone formation, i.e. due to a much higher degree of efficiency and safety of the previously mentioned methods.
8. Reactive Cambiplasty by means of a conical screw induces periosteal reaction which is then used as an periosteal autologous bone transplant (P970539A).
The second group of operative methods for the surgical management of bone defects consists of the segment transport according to Ilizarov and a microsurgical method involving the transplantation of a vascularised bone transplant. However, these two methods differ significantly from the previously described ones since they do not involve a free bone transplant so no comparison is possible between them.
And finally, it should be pointed out that the method of autologous spongioplasty is until now considered to be the best osteoinduction method. This has been corroborated by many scientific research results. Due to the simplicity of its application, this method is also the most widely used one.
The essence of the invention is based on the scientifically proven fact. First presentation of the Adoptive periosteal cambiplasty method and differential conical screw was a IV European FECAVA/SCIVAC Congress, Bologna, Italy Jun. 18-21 1998. Second presentation was at XXIII World WSAVA Congress, Buenos Aires, Argentina Oct. 5-9 1998. That the recipient's own mechanically induced periosteal reactio
Priddy Michael B.
Smith Jeffrey A.
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