Device for plate osteosynthesis

 

The invention relates to medicine, namely to traumatology, orthopedics, and can be used as a means of treatment of plate osteosynthesis of fractures, necroshine, false joints and deformities. The technical result from the use of the invention is to improve the reliability of plate osteosynthesis and decrease the morbidity. The device comprises a plate with holes with cylindrical thread and screws made with cylindrical thread of different diameter to its length. The outer diameter of the cylindrical thread, which is located closer to the end portion of the screw is less than the diameter of a cylindrical thread of the screw, second cylindrical threaded plate. Between the sections of the screw with cylindrical thread is a transitional area, the values of the external thread diameters which vary between the values of the external diameter of the thread of the cylindrical sections, and screw protrusions thread one section directly continue in the helical projections on the other site. The thread pitch of the transition, adjacent cylindrical sections and the thread pitch of the holes of the plate are the same. 6 Il.

The invention relates to medicine, namely to travmatolog joints and strain.

A device for external fixations, made in the form of plates with holes are not threaded and screws, which contain cylindrical thread on the site outside of the head [1].

The design has the following disadvantages.

1. The unreliability of using the device with poor bone quality due to non-rigid connection of screws and plates, caused by the impossibility of sufficient pressure plate heads of the screws to the bone to create the necessary friction between the plate and fragments. In conditions when the maximum friction force between the design and the fragments become smaller component of the external load directed on the slide plate relative to the bone, the difference between this component and the maximum friction force is directly transferred to the connection plate with the screw head. This causes movement of the plate relative to the bone due to the lack of fixation of screws in the holes of the plate, increasing the risk of delayed consolidation, necromania.

2. The unreliability of using design in monocortical form, i.e. in terms of fixing screws to one (nearest) cortical layer of the bone, also due to the loose nature of the connections between the directly on the screw head, the latter can easily be rotated in the near cortical layer of the fragment and in the hole of the plate, with which the screw loosely interacts, as the moment produced one of the cortical layer of the bone, has a short shoulder, limited by the thickness of the cortical layer.

Therefore, to increase the internal moment counteracting the external load, it is necessary according to the requirements of technology of application of this latch to enter screws through both the cortical layer of the fragment, but this leads to significant disruption of blood supply to the bones, increasing the risk of aseptic and infectious complications.

3. Significant damage to the periosteal circulation, due to the need of the pressing plate to the fragment due to non-rigid connection plate and screws. Circulatory disorders of the bones leads to osteonecrosis, osteoporosis, high risk of infectious complications, refractor, delayed consolidation and necromany.

Known compressible screw [2], containing the thrust rod with thread and installed on its mounting end of the sleeve with an external thread, a step which is less than the step buttress threads of the rod, and the connection of the sleeve with the screw threaded end, and sopryazheny the connection of the sleeve with the end of the rod, in this case the rod and sleeve “become a single rod with threaded ends different step, the rotation of which is ensured by the compression of the bone fragments”. The device as described is intended for the treatment of hip fractures.

The disadvantages of the device are as follows.

1. The unacceptability create compression, and therefore, a stable connection with the use of this device in the transverse, or close to it fractures diaphyseal division of bone. To ensure the effect of compression is necessary in this case, the compression of bone fragments along the axis, that is, you need the combination of the axis of fragments axis compressicauda screw, as the latter develops a compressing force along its axis, rather than at an angle thereto. However, the introduction of such a screw axis of fragments will inevitably cause damage to the articular ends of bones, as their axis in most cases continue in the cavity of the respective joints. In addition, this technique is compression will require the use of screws considerable size, namely cross-section corresponding to the cross section of the bone channel, axis - length of the bone, which will lead to a significant surgical trauma and risk of complications.

2. The inability of the POPs is this device together with the plate, provided with a female threaded, second outer thread of the sleeve compressicauda screw, and placed at some distance from the bone to prevent damage to the periosteum. The achievement of this goal will require eccentric introduction of the screw into the hole of the plate as illustrated in the analysis of the prototype of Fig.2. The difference between steps buttress threads of the rod and thread the holes of the plate, second outer thread of the sleeve, and the lack of direct transition spiral protrusions buttress threads of the rod in the screw tabs on the sleeve lead in this case to contact the end face of the bushing with the hole edge of the plate and offset it with fragments as described and shown for the prototype (Fig.3).

3. Low fatigue strength compressicauda screw, due to the implementation it is not monolithic, and containing the rod and the sleeve. The latter interact with each other on the thread and conical surfaces, which are “rasprashivat” deleting a construction it is Obvious that in the course of such interaction in the zone of connection occur prior voltage, which reduces the total strength of the structure, which increases the risk of fracture or plastic deformation of WMD is a clamp for plate osteosynthesis [3], contains a plate with holes with cylindrical thread and screws made with cylindrical thread of different diameter to its length, and the outer diameter of the cylindrical thread located closer to the end portion of the screw less, and the step is larger than the external diameter and pitch of the cylindrical screw thread, second thread of the plate, while a direct extension of the helical ridges of the thread of one section of the screw in the screw tabs on the thread section of the screw with a different diameter is missing.

The disadvantages of the design are as follows.

1. The creation of pre-stress in the design and bones during sequential introduction of screws through the screw holes in the plate in fragments because of a difference of steps cylindrical threaded sections. There are different scenarios depending on the type of interaction between plate and bone fragments. If the location of the plate at some distance from the introduction of the first bone screw through the plate into the fragments will lead to the effect of the proximity of the plate to him at a distance equal to the number of revolutions of the screw in the plate and bone, multiplied by the difference between the steps in the threads of cylindrical sections, without creating a pre-stresses in the area to which they prevent the first screw, coupled with carvings tomcom and plate. Under these conditions, the difference between the steps in the thread will rezultirase in deformation structures and bone and, consequently, the occurrence of pre-stress. If the location of the plate on the bone prior voltage at the point of contact of the plate and screw with the bone will occur during the introduction of the first screw. Pre-stressing reduce the margin of safety of the structure and its connections with fragments, this increases the risk of fracture, plastic deformation of the locking mechanism of strength loss of his connection with the bone, delayed consolidation, necromania. The reduction factor of safety of each screw connection can be partly compensated by an increase in the total number of input screws. However, this technique increases the invasiveness of the surgery and the associated risk of aseptic and infectious complications.

2. The danger of interfering with the mapping of fragments (reposition) due to the above-described effect reciprocal movement of the plate and the bone, caused by the difference of the steps is threaded cylindrical sections of the screw. Violation repositions not only leads to deformation of the bone segment that could adversely affect its subsequent function of the increased risk of delayed consolidation, necromania.

3. The inability to create axial compression of bone fragments in the transverse or very close to the fracture due to eccentric insertion of the screw into the hole of the plate in the absence of direct contact of the plate with the bone and periosteum. Due to the difference of the steps in the thread holes of the plate and the end portion of the screw, there is no immediate transition spiral protrusions thread the end portion of the screw in the screw tabs on the screw thread, second thread plate, eccentric introduction of such a screw contact occurs between the lower surface of the first wrap of the cylindrical screw thread, second thread holes of the plate, with the edge of the hole (Fig.2). Side screws on the plate acts directed normal to the ground contact force F, which can be represented as a sum of F1and F2. When considering the equilibrium condition of the structure in the coordinate system with the center at the point O (line break) power F1balanced force F3acting on behalf of another screw in the opposite direction, and time |S|F1balanced by the oppositely directed moment |S|F3. Component Fb) to the contact plate with the bone (point C in Fig.3) and, therefore, the violation of the periosteal circulation;

C) violation of the parallelism of the axis of the screw L and the axis of the hole of the plate and thus be unable in the future to create a rigid connection of the screw and the plate.

Achieving necessary to create a stable connection axial compression is possible either in the original positioning of the plate on the bone (component F2in this case, is balanced by the force of the support reaction), resulting in crushing of the periosteum and nourishing bone vessels, or with the use of additional compressicauda devices fixed to the bone and the plate outside of the latter, which requires an increase in surgical access and is accompanied by an increase of the operative trauma and the risk of complications.

The task of application of the invention is to improve results of treatment of fractures of long bones and their consequences.

The technical result from the use of the invention is to improve the reliability of plate osteosynthesis and decrease the morbidity.

This technical result is achieved by Thu screws, containing sections with cylindrical thread of different diameter to its length, while the outer diameter of the cylindrical thread located closer to the end portion of the screw is less than the diameter of a cylindrical thread of the screw, second cylindrical threaded plate, and between the parts of the screw with cylindrical thread is threaded transition section, the external diameter of the thread which vary between the values of the external diameter of the thread of the cylindrical sections, and screw protrusions thread one section directly continue in a spiral protrusions thread on another site, and the thread pitch of the transition, adjacent cylindrical sections and the thread pitch of the holes of the plate are the same.

In Fig.1 presents the proposed device, side view; Fig.2 - calculation scheme to determine the conditions of equilibrium in the interaction of fragments and device prototype with eccentric introduction of the screw into the hole of the plate; Fig.3 is a diagram of displacement of bone fragments and design with eccentric introduction of the screw device of the prototype of Fig.4 (a-d) stages eccentric proposed screw in the hole of the plate and in the cortical layer of the fragment of Fig.5, 6 - scheme of things, the distance from the bone.

Device for plate osteosynthesis (Fig.1) is made in the form of a plate 1 with holes with cylindrical thread 2 and 3 screws with cylindrical thread 4 of smaller diameter located closer to the end portion of the screw, cylindrical thread 5 of larger diameter, second threaded holes of the plate, and a transition area 6 with a thread of variable diameter. The thread pitch of the transition, related sites screws with cylindrical thread and the thread pitch of the holes of the plate are the same.

Because the thread pitch of the cylindrical sections of the screw in the proposed device is identical to the sequential insertion of screws through the screw holes in the plate in the fragments relative displacement of the plate and the bone, as well as deformation of the plate and the bone in contact with the screws not observed. The absence of pre-stress at the site of contact of the screw with the bone allows to increase the resistance of the external design loads, to minimize the number of screws, which increases reliability and reduces the invasiveness of osteosynthesis.

When eccentric introduction of the screw in the proposed device in the first stage, the threaded end portion of the screw interacts with the bone and threaded holes in the plate as p is thread the holes and screw the same. During the further insertion of the screw in the screw grooves of the thread holes of the plate fall into the helical projections of the transition section, as they are a direct continuation of the spiral protrusions cylindrical thread, which thus acts as the sender thread of the transition area. Since the values of the external diameter of the thread of the transition area increase with respect to the value of the outer diameter of the cylindrical thread section located closer to the end portion of the screw during rotation of the screw is the distance from its axis to the top of the spiral protrusions increases. This leads to exposure of the upper and lower surfaces of the screw tabs on the appropriate surfaces of the helical grooves forces Q1and Q2respectively (Fig.4, b).

Because the thread pitch of the transition and the adjacent cylindrical sections are equal, the forces acting on the plate by the upper and lower surfaces of the spiral ledge will also be the same, and the resultant of these efforts Q3it will be directed perpendicular to the axis of the screw direction, resulting in the displacement of screw hole center (distance m in Fig.4, a) and compression of bone fragments along the axis of the force R (Fig.5, 6) without what atom, the effect of axial compression in the absence of direct contact between the plate and the bone is only possible with the cooperation of all features specified in the description of the device, and the exclusion of any of them makes the implementation of this effect is impossible. The presence of a plate with holes with cylindrical thread, second largest cylindrical thread of the screw, allows for eccentric introduction of the screw into the hole of the plate to develop compressible force transverse to the axis of the screw direction and, therefore, to compress the fragments axis in the transverse, or very close to the fracture, thereby to ensure the stability of the connection. The difference between the diameters of the two cylindrical threads of the screw gives the opportunity to shift its axis to the edge of the orifice plate by the amount necessary to create compression. The presence of the transition between the two cylindrical threads of the plot, the diameter of the external thread of which varies in the range between the values of the external thread diameters of cylindrical sections, the immediate transition of the screw lugs of one section in the screw lugs of the other section and equality the steps of carving transition, adjacent cylindrical sections of the screw and the threaded hole is on the next screw lug screw recess, and not with the edge of the hole plate. This is necessary for the development of compressive efforts along the axis of fragments without any angular deformation in the fracture area and direct contact of the plate with the bone. Equality of steps the thread of the transition, adjacent cylindrical sections of the screw and the threaded hole of the plate causes rotation of the screw of the value of its movement relative to the plate and the bone will be the same, allowing you to maintain a specified distance between the bone and plate.

With the device are as follows. At the first stage performs the reposition of bone fragments, preferably by indirect techniques. Then position the plate on the bone or at some distance from it, preventing the periosteum from damage, fix the plate to one fragment by sequential insertion of screws into the threaded holes of the plate, overlapping the axis of the screw hole axis. When transverse or very close to the turn of the introduction of the first screw in the second of the fragments through the hole of the plate produce eccentric to create mejregionalnoi compression. Next the screws enter as the first of the fragments.

Sources of information

1. M. E. Muller, M. Allgower, R. Schneider, X. In A1, MCI AND 61 IN 17/58.

3. Journal of AO/ASIF “Dialogue”, volume 10, edition 1, June 1997, page 12, of the prototype.

Claims

Device for plate osteosynthesis containing a plate with holes with cylindrical thread and screws made with cylindrical thread of different diameter to its length, and the outer diameter of the cylindrical thread located closer to the end portion of the screw is less than the diameter of a cylindrical thread of the screw, second cylindrical threaded plate, characterized in that between the parts of the screw with cylindrical thread is threaded transition section, the external diameter of the thread which vary between the values of the external diameter of the thread of the cylindrical sections, and screw protrusions thread one section directly continue in a spiral protrusions thread on another site, while the thread pitch of the transition, adjacent cylindrical sections and the thread pitch of the holes of the plate are the same.

 

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