RU2488363C1 - Compression osteosynthesis of femoral bone neck - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medical equipment, namely to devices, which are applied in traumatology. Device consists of rod, two screw nuts and washer. Rod has monodirectional screwing with different step, which is 3 mm high on its front end and 2 mm step, and on back end is 0.3 mm high and 0.6 mm step. Thread on back end of rod corresponds to internal thread of screw nuts. Washer has quadrangular shape with 1 mm high kinks on corners. Projecting above surface of bone segment of rod is "pinched off" with pliers after final "lock-nutting" of nuts.

EFFECT: invention ensures increased efficiency and reduction of terms of treating patients with femol bone neck fractures.

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Description

The invention relates to medical equipment, namely to devices used in traumatology and orthopedics.

Fractures of the femoral neck are a problem of great social significance and at the same time difficult for the health system. In Russia, the frequency of fractures of the proximal end of the femur is about 60 cases per 100 thousand people, and the overall mortality rate for this type of injury is close to 12%. This is due to the fact that medial fractures of the femoral neck, being a marker of osteoporosis and the sad privilege of the elderly and senile, as a rule, they do not grow together without surgery. The risk of hypostatic complications (pressure sores, cardiorespiratory disorders, decompensation of intercurrent pathology, etc.) in case of refusal of surgical intervention is even higher than the risk of surgical aggression. Therefore, the development of reliable, highly effective and atraumatic methods of osteosynthesis, which is considered a priority task of domestic and world traumatology, is especially important in the treatment of femoral neck fractures (A.V. Kaplan, 1979; N.A. Shesternya, Yu.S. Gamdi, S.V. Ivannikov, 2005; N.V. Kornilov and E.G. Gryaznukhin, 2006 and others).

Criticism of analogues

Of the existing methods for treating femoral neck fractures, the most common are open and closed methods for osteosynthesis of the femoral neck and hip replacement. Open methods of osteosynthesis, despite the possibility of accurate reposition and stable fixation of bone fragments, are associated with aggravation of the blood supply to the neck of the femoral bone ischemia of bone fragments due to anatomical features. The latter is often complicated by the non-fusion of a neck fracture and the development of aseptic necrosis of the femoral head. Endoprosthetics, being a radical high-tech method for treating diseases and injuries of the hip joint, has its drawbacks as a high aggression of surgical intervention, many early and late complications and significant economic costs.

Prototype

As the closest analogue, we give a method of closed osteosynthesis of the femoral neck with spongy screws (Traumatology: national leadership / Edited by G.P. Kotelnikov, S.P. Mironov. - M.: GEOTAR-Media, 2008. - 808 p. - S. 377-386), selected as a prototype. It consists in the fact that the reposition of a femoral neck fracture is performed closed on the Hawley table, and osteosynthesis of bone fragments is performed through external access in the region of the greater trochanter (without penetrating into the cavity of the hip joint) with spongy screws as follows.

On the table, Hawley repositions of bone fragments: bending at right angles in the knee and hip joints, pulling the thigh upward with increasing force, then rotating the thigh inwards with abduction with uninterrupted axial thrust; then extension of the lower leg and thigh with simultaneous traction of the limb along the length and maintaining internal rotation and abduction of the thigh. The limb is fixed to the foot supports of the Hawley table in moderate tension. Parallel to the pupartic ligament on the skin of the abdomen, a bar with holes is hemmed and the knitting needles are cutaneous on the neck of the femur.

After X-ray inspection, which verifies the reposition of the fragments, the optimal spoke is left as a guideline, all the other knitting needles are removed and the next step of the operation is started.

A linear longitudinal incision is made of the skin from the level of the greater trochanter down by 7-8 cm.The subcutaneous tissue, fascia, abducting muscles of the thigh and periosteum are cut with exposure of the bone area below the base of the greater trochanter, through which 3 Kirschner spokes are drawn along the axis of the femoral neck. X-ray control is performed in 2 projections and 2-3 spongy screws are inserted along the optimal spoke, after which the spoke is removed and control radiography is performed in a direct projection. The wound is washed with antiseptic solutions and sutured in layers, leaving drainage. An aseptic sticker is placed on the wound and a derotational plaster “boot” on the foot.

Prototype criticism

The prototype device and its use in the reposition of sagging condyles of the tibia have the following disadvantages:

- the need for precision accuracy in calculating the length of the screws; the excess of the required length of the screw leads to perforation of the femoral head with the exit of the screw into the joint cavity and the lack of mutual adaptation and stable fixation of bone fragments; insufficient screw length leads to the inability to achieve adaptation of bone fragments, which is due, firstly, to the fact that the screw does not adequately capture the proximal bone fragment, and secondly, the spongy screw lobes of the screw capture not only the proximal bone fragment, but also distal, which excludes the attractive effect of the screw and mutual compression between bone fragments and, therefore, the stability of osteosynthesis, especially with osteoporosis;

- the difficulty of dispensing compression between bone fragments, which, when the screw is undershot (under-screwed), is associated with a lack of mutual adaptation between bone fragments, and when tugged, the thread (blades) of the screw formed in the bone is torn off, which is especially important for osteoporosis and leads to instability and failure osteosynthesis;

- frequent disruption of the faces of the screw head and / or screwdriver when the screw is screwed into the bone; this leads to the difficulty of screwing and unscrewing the screw, as well as the need for traumatic and weakening bone strength drilling or hollowing out the bone around the screw to capture the screw head with twisting and replacing it.

The purpose of the invention is to increase the effectiveness of the treatment of patients with fractures of the femoral neck.

SUMMARY OF THE INVENTION

The goal is realized by using the device (Fig. 1), consisting of a rod with multi-step unidirectional thread (at its front end, the thread has a height of 3 mm and a pitch of 2 mm (item 1), and at the rear end, a height of 0.3 mm and pitch 0.6 mm (pos. 2)), two nuts (pos. 33) and a washer (pos. 4). In this case, the thread at the rear end of the shaft (item 2) corresponds to the internal thread of the nuts (item 3). Screwing the rod into the bone is carried out with a socket wrench No. 8 and provide locking (counter screwing and thereby locking on the rod) of both nuts (figure 2). Locking is carried out with two wrenches No. 8, and one of the keys, namely the one that holds the nut closest to the front end of the shaft, must be flat, and the second wrench - flat or socket. Locking both nuts provides the immobility of these nuts on the thread of the rod and the ability to manipulate this rod, namely screwing it into the bone and unscrewing it from the bone, performed using a socket wrench No. 8, unscrewing is performed with two wrenches No. 8, one of which, namely the one that holds the nut closest to the front end of the shaft should be flat, and the second key should be a socket. In this case, the flat key holds the nut closest to the front end of the shaft, and counterclockwise rotates the nut furthest from the front end of the shaft with the socket wrench. Compression between bone fragments is performed by screwing clockwise the nut that is closest to the front end of the rod. Since the rod has a multi-step unidirectional thread, the difference between the height and the thread pitch at the front and rear ends of the rod (at the front is 3 mm and pitch 2 mm, and at the rear is 0.3 mm and 0.6 mm, respectively), when screwing the to the front end of the shaft of the nut, it is not so much the further screwing of the shaft into the bone that ensures the mutual compression between the bone fragments. Consequently, a multi-step unidirectional thread of the rod provides precise accuracy of dosing compression at the junction of bone fragments, which does not depend on the accuracy of calculating the length of the rod. A washer is pre-installed between the nut and the bone closest to the front end of the shaft in order to reduce the load on the bone under the nut and prevent the nut from sinking into the bone. The washer has a quadrangular shape with teeth at the corners, 1-2 mm high, which prevents it from rolling over the surface of the bone when tightening or unscrewing the nut. This reduces the trauma of tissues (bones, periosteum) and the risk of developing metallosis (tissue reaction to metal) and suppuration. After adequate compression is achieved at the junction of the bone fragments, both nuts are finally locked (the nut closest to the front end is immovably held with a flat wrench, and the distant nut is screwed clockwise until it stops), and the piece of the shaft protruding above the bone surface is bitten off with pliers.

Device application example

As an example of the use of a device for compression osteosynthesis of the femoral neck, we present the following observation.

Patient G., 67 years old, was admitted to the Republican Orthopedic and Trauma Center in the city of Makhachkala on 10/23/2010 with a diagnosis of Closed abduction transcervical fracture of the neck of the left femur with displacement.

From the anamnesis: 3 hours before admission to the hospital when falling on his side, the patient received a personal injury. An emergency blockade of the fracture site was performed with a 2% novocaine solution and under local anesthesia they imposed skeletal traction on the femoral condyles with a load of 5 kg.

10/29/10, in a planned manner, the operation was performed: Closed osteosynthesis of the neck of the left femur with a compression device. The patient was placed on an orthopedic table and repositioned of bone fragments by abduction of the lower limb by 25 degrees, traction along its axis and internal rotation of the thigh by 40 degrees. The success of the reposition was verified by x-ray of the hip joint in two projections - anteroposterior (direct) and axial. Then, parallel to the pupartic ligament, a metal plate with holes from the set of Ilizarov’s apparatus was sutured to the skin of the patient’s abdomen, and several Kirschner spokes were drawn from the underdent region, orienting along the neck of the thigh, and then radiography was performed again. After X-ray control, a needle was left that was optimally passing through the center of the neck of the femur, parallel to which two bone fragments transcervically through both bone fragments had two compression devices consisting of a rod with multidirectional unidirectional thread (at its front end, the thread of the rod has a height of 3 mm and a pitch of 2 mm, and at the rear the end is a height of 0.3 mm and a pitch of 0.6 mm), two nuts and a washer. In this case, the thread at the rear end of the shaft corresponds to the internal thread of the nuts. Screwing the rod into the bone was performed with a socket wrench No. 8 and provided with counter-tightening (locking) of both nuts. Locking was carried out with two No. 8 wrenches, and the one closest to the front end of the rod was flat, and the second one had a socket wrench. Locking both nuts ensured the immobility of these nuts on the thread of the rod and the possibility of screwing the rods into the bone. Compression between the bone fragments was performed by screwing clockwise the nut that was closest to the front end of the rod (de-opening was also done with two No. 8 wrenches). The difference between the height and the pitch of the thread at the front and rear ends of the shaft (at the front height of 3 mm and a pitch of 2 mm, and at the rear - 0.3 mm and 0.6 mm, respectively) when tightening the nut closest to the front end of the shaft provided not so much further screwing the rod into the bone, how much is the increase in mutual compression between bone fragments and thereby the precision accuracy of dosing compression at the junction of bone fragments. Washers were pre-installed between the nut and bone closest to the front end of both rods to reduce the load on the bone under the nut and prevent the nut from sinking into the bone. The washers had a quadrangular shape with denticles at the corners, 1-2 mm high, which prevented them from rolling over the surface of the bone when tightening or unscrewing the nuts, and thus minimized bone trauma and the risk of suppuration. After adequate compression was achieved at the junction of the bone fragments, the final contraction was performed, and the segment of the shaft protruding above the surface of the bone was bitten with pliers. The wound is washed with antiseptic solutions and sutured in layers by interrupted sutures. On the control radiographs, a satisfactory position of the bone fragments with their adequate mutual adaptation was verified.

The wound healed first; sutures were removed on the 8th day. The patient was discharged for outpatient treatment under the supervision of a local doctor. The result of treatment is regarded by us as good.

Features of the invention, distinctive from the prototype

Design features (distinguishing features from the prototype) of a device for compression osteosynthesis of the femoral neck are:

- the presence of multi-step unidirectional threads (at its front end, the thread has a height of 3 mm and a pitch of 2 mm, and at the rear end, a height of 0.3 mm and a pitch of 0.6 mm);

- screwing the rod into the bone is carried out with a socket wrench and provide locking (counter-screwing and thereby blocking on the rod) of both nuts. Locking both nuts creates the immobility of these nuts on the thread of the rod;

- compression between the bone fragments is performed by screwing clockwise the dextralized nut closest to the front end of the rod;

- the presence of a multi-step unidirectional thread when screwing the de-aligned nut closest to the front end of the rod when the wrench is rotated clockwise provides not so much further screwing of the rod into the bone as an increase in mutual compression between the bone fragments;

- the washer between the nut and the bone closest to the front end of the shaft has a quadrangular shape with teeth at the corners, 1-2 mm high, which prevents it from rolling over the bone surface when the nut is screwed or unscrewed;

- after compression has been achieved at the junction of the bone fragments and the final locking of both nuts, the section of the shaft protruding above the bone surface is bitten off with pliers.

The technical result (advantages over the prototype) of the device for closed reposition of the sagging condyle of the tibia:

- the value of the achieved compression at the junction of bone fragments is higher than when using the prototype, which means that the conditions for consolidation of the fracture are better (compression enhances the mutual adaptation of bone fragments and increases the stability of fixation of the fracture zone);

- precision accuracy of compression dosing at the junction of bone fragments, not depending on the accuracy of calculating its length (in contrast to the prototype device);

- minimizing the risk of thread breakage in spongy tissue;

- unification of the size of devices with no need for a wide range of their sizes when used on bones of different sizes;

- the unidirectionality of the thread at both ends of the device, on the one hand, guarantees relaxation of one of them when tightening the other, and, on the other hand, minimizes the risk of thread breakage in the porous spongy bone tissue of the proximal bone fragment of the femoral neck (there is usually a porosity , since the fracture of the femoral neck itself is a “marker” of osteoporosis) with increased compression, which is achieved by tightening the nut with a small thread pitch. Compression when tightening a nut with a small thread pitch is, firstly, more dosed, and, secondly, achieved with a fixed large thread. The immobility of the coarse thread relative to the movable fine thread is due to the fact that the coarse carving blades wedge into the bone, and the friction force between the metal and the bone clearly prevails over that between the fine external thread of the rod and the corresponding internal thread of the nut. Therefore, although the thread is unidirectional, it is easy to adjust the screwing in both front and rear threads;

- eliminating the likelihood of disruption of the edges between the key and the nut (whereas when using a screwdriver and the edges of the screw head, disengagement of the edges is a frequent complication leading to damage to the screw and screwdriver;

- the presence of teeth on the corners of the washer of a quadrangular shape reduces the trauma of tissues (bones, periosteum) and the risk of developing metallosis (tissue reaction to metal) and suppuration when tightening or unscrewing the nut.

Thus, for compression osteosynthesis of the femoral neck, one can count on increasing the effectiveness of the treatment of these injuries, reducing their terms and improving the quality of life of patients.

Claims (1)

A device for compression osteosynthesis of the femoral neck, consisting of a shaft, two nuts and a washer, characterized in that the shaft has a multi-step unidirectional thread having a height of 3 mm and a pitch of 2 mm at its front end and a height of 0.3 mm at the rear end and pitch 0.6 mm; wherein the thread at the rear end of the shaft corresponds to the internal thread of the nuts; the washer has a quadrangular shape with teeth at the corners, 1 mm high, and a piece of the rod protruding above the surface of the bone after the nuts are finally locked in, “bite” with pliers.

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