HRP980332A2 - Differential conical screw for a bone as a periosteal bone autotransplant growth inductor - Google Patents

Description

The field to which the invention relates

This invention relates to the field of reconstructive bone surgery in orthopedics and traumatology, in the treatment of "pseudarthrosis defect" when a part of the bone is missing due to the resulting defect, and it needs to be replaced with one of the grafts due to successful healing. These bone defects occur as a result of major trauma (e.g. gunshot wounds), in open fractures when it is necessary to surgically remove pieces of crushed bone, then after infections (osteomyelitis) when bone sequestrations are also removed, and finally after the removal of bone tumors and cysts. In addition to the aforementioned "pseudarthrosis defect", the area also includes "avascular pseudarthrosis", in which there is a lack of vital bone cells in the area of the fracture as a result of devascularization of the bone by more severe surgical procedures, and later bone healing does not occur (even though the ends of the bone are in contact). For this reason, one of the methods of osteoinduction (stimulation of bone formation) is applied here, which also includes bone autotransplantation operations.

Technical problem

The purpose of a bone graft is twofold:

1. It represents a medium for the growth of bone cells from the edges of the bone defect. Because of this, and because of faster revascularization, a spongy structure is more suitable than a homogeneous one.

2. The transplant should have a local osteoinductive effect. which can have the only vital tissue with living bone cells that produce bone (osteoblasts) by secreting osteoid - a protein in which calcium hydroxyapatite is deposited, and thus the mineral, solid inorganic part of the bone is formed.

The basic technical problem is obtaining a high-quality graft (as vital as possible) that will cause strong osteoinduction, with the action of living transplanted cells (osteoblasts). In addition to the above, induction with BMP (bone morphogenic protein), extracted from bovine bone, is increasingly used, that is, some other locally modified growth factors are also being investigated. they are easily not living cells. BMP placed locally in the area of bone injury stimulates the surrounding cells to intensify bone formation.

In my earlier patent application to the State Institute for Intellectual Property of the Republic of Croatia dated October 9, 1997. and under the application number P970539A I presented a static and dynamic method of mechanical induction of periosteal reactive bone growth. Of them, the static method is the one that uses conical screws with a self-tapping tip and is much simpler in the procedure, because no subsequent stimulation is required after their placement in the bone. It was found that the most optimal wedge screw is at an angle of about 7 degrees. It is placed in a hole in the bone drilled with a conical drill which is also at 7 degrees. However, the width of the upper opening of the hole corresponds to the initial part of the screw, which then becomes wider, so the diameter in the upper part of the screw is more than 0.5 mm larger than the diameter of the entrance part of the hole. Going deeper and deeper like this, the screw behaves like a wedge that overstresses the bone to the side. Because of this, over the course of a month or more, a bone reaction occurs on the surface around the screws, which, after removal with a chisel, is surgically transferred to the area of the bone defect.

State of the art

The methods used for surgical treatment of bone defects are the methods of free bone grafts, segment transport according to Ilizarov, and microsurgical vascularized bone graft. Free bone grafts are the most numerous, the simplest to apply, and therefore the most used, and they include:

1. Autologous spongioplasty (own spongy bone - red bone marrow) which is definitely and everywhere considered the best osteoinduction material because it has its own vital cells and is spongy in structure. It is usually taken from the pelvis (cristae or acae).

2. Corticospongioplasty, in addition to the spongy inner part of the bone, also uses the outer hard cortical part. The cortical part itself is less valuable as an osteoinductor, because it has very few osteoblasts. and in terms of structure, it is a homogeneous hard bone (even dead after transplantation), and later it must be completely rebuilt with new cells from the environment. However, it has a good side because it has mechanical strength. It is usually taken from the pelvis or the middle third of the fibula.

3. Homologous spongioplasty (spongy bone from another person) from bone banks is increasingly being abandoned (AIDS, hepatitis, reaction to foreign proteins, infections, etc.), and is turning to the use of artificial bone grafts.

4. Artificial bone transplantation. The method with the advantage of not taking one's own bone, which reduces surgical trauma, is being used more and more. The disadvantage is that these transplants do not have living cells, but serve as a spongy medium for the ingrowth of the surrounding own cells, and the healing is slower and of lower quality than when using autologous spongioplasty. This group includes two types of transplants. First, those that originate from biological tissue (bovine spongiosa, collagen, coral mineral, etc.) or are of inorganic origin (hydroxyapatite). Many of them are trademarked under various names, Bio-Oss® (Geistlich AG, Switzerland), Osteovit(R) (B.Braun Melsungen AG) and others.

5. Corticotomy according to Judet

6. Osteoinduction with BMP

7. Transplantation of the periosteum is mentioned only sporadically in the literature in a few cases, and is not used due to the uncertainty of subsequent bone formation, or due to the significantly greater efficiency and safety of the previously mentioned methods.

8. Reactive camboplasty using a conical screw causes the formation of a periosteal reaction, which is later used as an autologous bone graft.

Another group of operative methods for treating bone defects is the Ilizarov segment transport method and the microsurgical method of transplanting a vascularized bone graft. However, they are fundamentally different, because they do not represent free bone grafts, and cannot be compared.

We should also only mention a group of other non-surgical osteoinduction methods (magnetotherapy, current induction, etc.), but like the ones mentioned above, they cannot be compared here.

And finally, it should be emphasized that the method of autologous spongioplasty is considered, and it is definitely scientifically proven, the best osteoinduction method in the group of free bone grafts. Due to its simplicity of application, it is generally the most widespread.

Presentation of the essence of the invention

The basis of the invention is based on the scientifically researched and confirmed fact (not yet published) that the own mechanically induced periosteal bone reaction formed on the bone surface after 4-8 weeks has a significantly (even twice) stronger osteoinduction capacity than the own cancellous bone (red bone marrow). It should be noted right away that this reaction cannot be considered the usual periosteal callus that occurs in fractures, for two reasons:

1. This reaction occurs as an adaptation to a new load, not a reaction to trauma. Namely, the induction of the growth of new bone cells (osteoblasts) results from the partition due to the changed and on our part induced and increased internal stress in an otherwise healthy bone of uninterrupted continuity, and not as a result of a fracture and the sequence of its natural healing.

2. Histologically, only bone tissue is found here, while in fracture callus it is mixed with the surrounding callus from the hematoma, endosteal part, muscle, and sometimes cartilaginous elements, etc. Microscopically, this difference is obvious and proven in several ways.

In an earlier patent application, I called the mentioned method "cambiplastica reactiva" (reactive formation of cambium), because that name completely defines it anatomically, and thus significantly distinguishes it from periosteum transplantation (surface sheath of bone). The periosteum is mainly made up of two layers, the outer fibrous layer that has blood vessels and capillaries, and the inner cambium layer that has a very thin layer called osteoprogenitor cells, precursors of osteoblasts. According to some anatomists, this cambium layer does not belong to the periosteum but to the bone, which is proven in a certain sense by my research. As stated earlier, neither the periosteum nor the cambium layer is transplanted, but mechanical changes in the internal stress are induced surgically, which stimulate the formation of the reaction of the cambium layer. After 4-8 weeks, there is a sufficient amount of this reaction, i.e. newly formed bone, and it can be transplanted to another part of the body where bone tissue is lacking or osteoinduction is needed (eg atrophic pseudarthrosis or prolonged bone healing, etc.). This delayed transplantation of the resulting bone reaction after previous mechanical stimulation is a novelty and the essence of the invention itself. Hence the name "cambiplastica reactiva", not just cambiplastica. Namely, cambiplasty as such does not even exist, but would fall under periosteum transplantation, in which part of the cambium layer is also removed by scraping from the surface. However, at this stage (without previous mechanical stimulation) it is a microscopic layer of soft tissue, and not hard bone (slightly spongy consistency) as a reaction in "cambiplastica reactiva". In addition, it has already been stated earlier that the method of periosteum transplantation is generally not accepted due to the uncertainty of the results.

Through further scientific study, I came to other insights that, by changing the definitions of the above-mentioned cambium reaction, led to a minor change in the name of the method, which is now called "Adaptive periosteal camboplasty". Adaptive means that it is about adapting the bone to a new load, and not just a periosteal reaction. The name periosteal more closely indicates the area, while camboplasty indicates which part is transplanted.

The essence of this invention is the improved mechanical performance of the differential taper screw (Figure 1) versus the taper-only screw of earlier patent application P970539A. It is not placed in a conical hole without a cut thread, but in a flat hole in the bone, usually through only one cortex in the area of the diaphysis of the tibia. In this flat hole, a thread of the same pitch and diameter as the lower (cylindrical) part of the screw is cut with a tapping drill. When screwing this screw into the bone, due to its conical shape, distraction forces appear circularly around the hole in the bone, and due to the conicity, they are greater in the surface parts of the bone. This difference in the distribution of distraction forces in the surface and deep parts distinguishes the action of this differential conical screw from the conical screw of the previously mentioned application.

1. The second difference is contained in the name differential, which is a functional name that describes the kinematics of screwing this screw into the hole in the bone. This screw, in addition to having a conical shape, also has a variable pitch of the thread in the conical part, which grows from the lower cylindrical part towards the head continuously with a certain increase in height for each thread, whereby the variability of the pitch of the thread lies in the interval of 0.01-0.1 mm/ thread. This variability of its ascent is a characteristic of the form that achieves the mentioned differential function, and is made possible by the difference in the ascent of the thread, which is already smaller and already pre-cut in the bony part. For this reason, when screwing such a screw into a cylindrical hole in the bone with a cut thread rise, as well as in the cylindrical part of the screw, the screwing starts normally at the beginning, but as it progresses in depth, distraction forces appear longitudinally from the axis of the screw itself. This stretching of the bone gives additional stimulation to the formation of the aforementioned adaptation reaction on the bone surface for the purpose of obtaining an autologous bone graft. The pitch height of the thread of the differential conical screw in the cylindrical part can preferably be between 0.3 - 2 mm. This later becomes variable in the cylindrical part, either increasing or decreasing. The differential cone screw is made of stainless non-magnetic bone implant steel ISO 5832/6 or 5832/IV or 5832-8 or titanium alloy for implants ISO 5832-3.

Ways of realizing the invention

In contrast to the previous already cited application P970539A, only the static method enriched with another stimulation force that occurs when twisting this differential conical screw, and which is axial from the axis of the screw itself, is used to perform the procedure mentioned under the name of adaptive periosteal camboplasty.

In addition, when screwing this differential conical screw into the bone, a purpose-made torque wrench is used (Figure 2), which can be used to accurately control and thus predict the stimulation force in the bone, and prevent the possibility of bone cracking due to the occurrence of the aforementioned forces. Due to the simplicity of application between the wrench and the differential conical screw, an adapter was made which, due to the round sextant of the final part of the torque wrench, has the effect of a cardan joint. Its use during twisting reduces the possibility of bending forces in the screw and makes work easier.

When drilling a hole in the bone, a drill guide is used with a lateral water inlet and outlet, through which saline solution is injected with an injection syringe during drilling. This has two beneficial effects. Firstly, the temperature that occurs as a result of drilling, which damages the bone next to the hole, is reduced, and secondly, this water washes away bone detritus (sawdust) and thus improves the quality and precision of drilling.

Method of application of the invention

The invention is applied as mentioned earlier in the patent application P970539A in such a way that in the presence of any of the bone defects (trauma, bone cysts, consequences of earlier operations, etc.) a stimulation operation is performed 4-8 weeks before the planned main operation, in which the adaptation the bony reaction of the cambium part formed in the area of stimulation with a chisel is removed (as a standard procedure for taking an autologous bone graft) and transferred to the necessary part of the body where it needs to be grown to cause osteoinduction.

The invention is applied by simply using the aforementioned differential conical screw, which is placed percutaneously in the bone, most often in the area of the diaphysis of the tibia, where the bone is immediately under the skin, using several additional instruments. First of all, a drill guide is used with a side inlet (1 - Figure 1) and water outlet (2 - Figure 1), through which physiological solution is injected with a syringe during drilling. It consists of a handle (3 - picture 1) and a guide tube (4 - picture 1) of the drill bit. After that, a thread is tapped in the hole using a tapping drill of the same pitch and diameter as the cylindrical part of the differential cone screw. Then it is necessary to set the connection between the torque wrench and the differential conical screw, and this is achieved using an adapter (5 - picture 2) which has a key for the screw on one side and a key for the rounded (round) sextant on the lower end of the torque wrench (6 - picture 2) .). This is followed by the twisting of the differential conical screw using a torque wrench, which achieves the desired force of non-stretching and bone stimulation. The torque wrench transmits force via a torsion spring (7 - figure 2) in its lower part and is expressed as an angular displacement on the scale (8 - figure 2). The torque wrench is actuated via two handles (9 - Figure 2). The values of the moments of force were obtained by experimental measurements and expressed in a table, and refer to bone thickness, bone length, age, etc.

Claims (15)

1. Differential conical screw with variable thread pitch, which is used for the induction of osteogenesis on the surface of the bone and thus obtaining an autologous bone graft, and for use in human surgery and veterinary surgery, characterized by the fact that by introducing a new internal stress in the bone, it leads to the stimulation of adaptive biological reactions that create a new young bone on the periosteal part. 2. Differential conical screw according to claim 1, characterized by the fact that in the lower part (picture 3) it has a cylindrical part which after 2-5 threads turns into a conical part in which the thread becomes variable with a constantly increasing rise. 3. Differential conical screw according to claim 1 and 2, characterized by the fact that it has a sextant-shaped head as in Figure 3. 4. Differential conical screw according to claim 1 and 2, characterized in that it has a head in the connecting shape of an Allen key. 5. Differential conical screw according to claim 1 and 2, characterized in that it has a head in the form of a Philips connection. 6. Differential conical screw according to claim 1 and 2, characterized in that it has only a conical part and a variable rising rise. 7. Differential conical screw according to claim 1 and 2, characterized by the fact that it does not have a head, but is connected directly to the screwdriver via an Allen key. 8. Differential conical screw according to claim 1, 2 and 6, characterized in that it has a thread pitch variability of 0.01 - 0.1 mm/thread. 9. Differential conical screw according to claim 1 and 2, characterized by the fact that it has a thread height between 0.3 - 2 mm in the cylindrical part, which further in the cylindrical part becomes variable, either increasing or decreasing. 10. Differential conical screw according to claim 1, 2, 4, 5, 6, 7 and 8 characterized by the fact that it is made of stainless non-magnetic bone implant steel ISO 5832/6 or 5832/IV or 5832-8 or titanium alloy for implants ISO 5832-3. 11. Drill guide, for the purpose of setting the differential conical screw according to claim 10, characterized by the fact that it consists of a guide handle and a characteristic inlet and outlet tube (1, 2 - figure 1) for washing out detritus and sawdust when drilling bone. 12. Torque wrench, for twisting the differential conical screw according to claim 10, characterized by the fact that it consists of a round sextant (6 - picture 2) which, together with the adapter for the differential conical screw (5 - picture 2), forms a cardan joint . 13. The torque wrench according to claim 12, characterized by the fact that it achieves a repeatable and measurable moment of force through the torsion spring (7 - figure 2), which is expressed on the scale (8 - figure 2) as angular arcuate or longitudinal displacement. 14. Torque wrench according to claims 12 and 13, characterized by the fact that the turning mechanism is achieved via a lever with two handles (9 - picture 2) in the crank position. 15. Torque wrench according to claim 14, characterized by the fact that the turning mechanism is realized directly via one handle like an ordinary screwdriver.