RU236057U1 - Device for positioning the acetabular fragment during periacetabular osteotomy - Google Patents

Abstract

The utility model relates to the field of medicine, namely traumatology and orthopedics, and can be used when performing periacetabular osteotomy. The device for positioning the acetabular fragment when performing periacetabular osteotomy is a housing with a two-stage profile, each stage of which has a contact surface, the contact surface of the first stage is made congruent to the inner surface of the iliac wing, the contact surface of the second stage is made congruent to the inner surface of the acetabular fragment, and the height of the second stage corresponds to the value that ensures the tilt and rotation of the acetabular fragment to the optimal anatomical and functional position. The technical result is an increase in the accuracy of performing periacetabular osteotomy while minimizing radiation damage and the risk of incorrect positioning of the acetabular fragment.

Description

The utility model relates to the field of medicine, namely traumatology and orthopedics, and can be used in performing periacetabular osteotomy surgery.

When performing periacetabular osteotomy, the key stage determining the success of the intervention is the correct spatial orientation of the acetabular fragment containing the acetabulum, which is performed after sequential osteotomies of the pubic, ilium and ischium. In clinical practice, this stage is implemented by installing a Shantz rod fixed to a T-shaped handle in the specified acetabular fragment, followed by its mobilization in the required direction. The direction of displacement of the acetabular fragment and its final position are assessed by direct visual control by the surgeon in combination with constant X-ray monitoring. [1] Errors made in positioning the acetabulum subsequently lead to uneven distribution of the load in the hip joint, which causes a sharp progression of deforming arthrosis [2].

The closest in technical essence is a device that fixes the mutual spatial orientation of bone fragments in an optimal anatomical and functional position during pelvic osteotomy for hip dysplasia [3], which is two fixators connected to each other by a bridge, the first of which is made in a congruent shape with the possibility of a tight fit on the iliac wing in the area of its anterior superior spine, and the second is congruent in shape to the lateral cortex of the anterior inferior spine of the acetabular fragment [3]. The bridge connecting the fixators is made in the form of an arcuate rod. Transposition of the acetabulum (acetabular fragment) is performed as follows: the first fixator is placed on the anterior superior spine, after which the acetabular fragment is rotated until the lateral cortex of the anterior inferior spine is aligned with the second fixator, then the achieved position of correction of the pelvic bone fragments is fixed, the wound is sutured.

However, the described device selected as a prototype does not provide effective treatment, namely, it does not allow for the reposition of the acetabulum to a position that ensures uniform distribution of the contact load in the loaded zone of the hip joint. This is due to the fact that, in essence, the prototype device only serves as a reference point when performing reposition: one of the device fixators acts as a reference point to which the fragment is brought during reposition, and the actual displacement of the acetabular fragment is performed using a standard set of instruments (reposition clamps, bone holders, etc.). Such a prototype device cannot perform the function of a repositioning instrument due to the following reasons. The fixators are made congruent to the spines of the ilium (the anterior superior and anteroinferior spines), which have an insignificant surface area. Since the area of the connection of each fixator with the corresponding spine is extremely small, a large force must be applied to the bridge connecting the fixators, made in the form of an arcuate rod, to displace the acetabular fragment. However, the design features of this device (small cross-section of the arcuate rod and elastic properties of the material (photopolymer)) do not provide a sufficient degree of rigidity that allows the bridge connecting the fixators to resist deforming forces during the displacement of the acetabular fragment. As a result, when using the prototype device (as a repositioning instrument), an attempt to perform reposition will result in a breakage of the device in the area of the bridge connecting the two fixators. In addition, the spatial arrangement of the second fixator is such that it is impossible to set the vector of displacement of the acetabular fragment in the required direction. It is only possible to align the anterior-inferior spine with this fixator during repositioning of the acetabular fragment using a standard set of repositioning instruments.

When mentioning the possibility of deformation of the bridge connecting the fixators, made in the form of an arcuate rod, it is worth noting that due to its small cross-section and the elastic properties of the material (photopolymer), when exposed to load during repositioning, there is a risk of displacement of one fixator relative to another by bone fragments, which as a result can lead to errors in the positioning of the anterior inferior iliac spine, and, accordingly, the acetabulum.

It is also worth noting that the design features of this prototype do not allow for temporary fixation of the acetabular fragment, which is necessary for inserting screws. As a result, the operating surgeon must fix the acetabular fragment with screws or pins, while simultaneously holding the acetabular fragment and constantly monitoring the correctness of its position relative to the prototype, which increases the risk of malposition and the preservation of residual displacement in the postoperative period.

All of the above determines the impossibility of using this prototype as a combination of two instruments in one: a repositioning and navigation device. In addition, the prototype device is designed to perform Salter pelvic osteotomies, which are used exclusively in pediatric patients (who have an unclosed triangular cartilage) and are not applicable when performing Ganz periacetabular osteotomy in young adult patients (with a closed triangular cartilage), since these interventions differ in the direction of the pelvic bone osteotomy lines, as well as the shape of the acetabular fragment and the direction of its displacement.

Currently, when performing periacetabular osteotomy, the spatial orientation of the acetabular fragment is assessed by direct visual control, as well as by constant intraoperative use of X-ray equipment, after which the specified bone fragment containing the acetabulum is fixed in the required position.

The disadvantage of this method of periacetabular osteotomy is its high complexity, since the positioning of the acetabular fragment is based on the surgeon's experience and requires constant intraoperative X-ray control, which increases the influence of the "human factor" and creates risks of pincer-type femoroacetabular impingement or the preservation of "residual" hip dysplasia in the postoperative period. The use of multiple X-ray control leads to an increase in radiation exposure for both the patient and the medical staff in the operating room, which increases the risk of negative consequences in the long term.

The technical task is to develop a device that allows for the correct spatial orientation of the acetabular fragment during periacetabular osteotomy in young adult patients (from 18 to 44 years old according to WHO data) without intraoperative X-ray control with high accuracy, according to preoperative planning.

The technical result consists in increasing the accuracy of performing periacetabular osteotomy while minimizing radiation damage and the risk of incorrect positioning of the acetabular fragment.

The technical result is achieved in that the device for positioning the acetabular fragment during periacetabular osteotomy is a housing with a two-stage profile, each stage of which has a contact surface, wherein the contact surface of the first (lower) stage is made congruent to the inner surface of the iliac wing, the contact surface of the second (upper) stage is made congruent to the inner surface of the acetabular fragment, and the height of the second stage corresponds to a value that ensures the tilt and rotation of the acetabular fragment to an optimal anatomical and functional position.

In specific embodiments of the device:

- in the second stage, a cutout is made with the possibility of ensuring the passage of cortical screws from the iliac crest through its thickness in the direction of the acetabular fragment;

- the contact surfaces of the steps are rectangular in plan, 3-4.5 cm long and 2-3.5 cm wide;

- through holes are made for fixing elements.

The design features of the device provide the ability to directly perform repositioning of the acetabular fragment (without using repositioning clamps, bone holders, etc., as in the prototype), increasing the accuracy of acetabulum positioning while reducing the time of intraoperative use of X-ray equipment, which reduces the radiation load and reduces the time of surgical intervention, and also avoids errors in determining the position of the acetabulum. The implementation of the body as a single piece (with a two-stage profile) eliminates the risks of relative displacement of the contact surfaces of the steps, in contrast to the prototype device, in which the contact surfaces are labile relative to each other. At the same time, the implementation of the contact surfaces congruent to the corresponding surfaces of the bone on which they are applied (the fixed fragment of the ilium and the acetabular fragment) ensures their reliable, stable and accurate conjugation during the operation. The above, together with the implementation of the second stage of the specified height, ensures controlled tilt and rotation of the acetabular fragment to the optimal anatomical and functional position, without the risk of incorrect positioning of the acetabulum due to the human factor or accidental displacement of the device elements, in one stage, i.e. without the need for X-ray control. The optimal anatomical and functional position of the acetabulum ensures adequate congruence in the hip joint, and, consequently, uniformity of load distribution on the articular cartilage.

Private embodiments of the device enhance the achievement of the declared technical result. Thus, making a cut in the second step provides the ability to visually control the passage of cortical screws from the iliac crest in its thickness in the direction of the acetabular fragment to the required depth, excluding hitting the joint. Making through holes in the body (steps) allows fixing the device on the bone surface, which eliminates the risks of its displacement during the operation. Making steps of a rectangular shape in plan, 3-4.5 cm long and 2-3.5 cm wide provides an optimal (sufficient, but not excessive) area of conjugation of the device with the surfaces of the fragments, taking into account the dimensions of access, the possibility of performing manipulations.

The essence of the claimed device is explained by the drawings:

Fig. 1. Device for positioning the acetabular fragment during periacetabular osteotomy (oblique view from below).

Fig. 2. Device for positioning the acetabular fragment during periacetabular osteotomy (side view).

Fig. 3. Device for positioning the acetabular fragment during periacetabular osteotomy, oriented towards the congruent contact surfaces of the ilium and the acetabular fragment (contact surfaces are shown, the device is raised 4 cm above the contact surfaces).

Fig. 4. Positioning of the acetabular fragment before fixing it with screws (the device is fixed to the pelvic bones with pins, the arrows indicate the direction of displacement of the acetabular fragment).

Fig. 5. Fixation of the acetabular fragment with cortical screws.

Fig. 6. Clinical example.

Fig. 7. Clinical example.

Fig. 8. Clinical example.

Fig. 9. Clinical example.

Fig. 10. Clinical example.

Fig. 11. Clinical example.

The figures indicate:

1 - body;

2 - the first (lower) step for the fixed fragment of the ilium;

3 - the second (upper) step for the acetabular fragment;

4 - contact surface of the first stage 2;

5 - contact surface of the second stage 3;

6 - holes for fixing elements;

7 - cutout;

8 - iliac wing (fixed fragment);

9 - osteotomy line of the ilium from the anterior superior iliac spine to the arcuate line of the pelvis;

10 - line 1.5-2 cm from osteotomy line 9;

11 - acetabular fragment;

12 - a line running from the upper border of the anterior inferior iliac spine perpendicular to the section of the arcuate line of the pelvis in the region of the acetabulum;

13 - knitting needles;

14 - cortical screws.

The device for positioning the acetabular fragment during periacetabular osteotomy is a body 1 with a two-stage profile, namely with a first (lower) stage 2 for a fixed fragment of the ilium and a second (upper) stage 3 for the acetabular fragment.

Grade 2 has a contact surface 4, which is congruent with the inner surface of the iliac wing.

Step 3 has a contact surface 5, made congruent with the inner surface of the acetabular fragment.

The height of the second step 3 corresponds to the value that ensures the tilt and rotation of the acetabular fragment to the optimal anatomical and functional position. Moreover, the second step 3 can have a variable height, i.e. with one H, and with the other H*. The absolute values of H and H*, as well as their ratio, determine the angle of tilt and rotation of the acetabular fragment.

The tilt of the acetabular fragment (and the acetabulum, respectively) is understood as a change in its position relative to the pelvic axis in the frontal plane, and rotation (version) is understood as a change in position relative to the pelvic axis in the axial projection.

Contact surfaces 4 and 5 are made with a surface area that ensures reliable coupling with the patient's bone surfaces, i.e. large enough, but not excessively so (taking into account the possibility of manipulation in the operation area). It is preferable to make contact surfaces 4 and 5 rectangular in plan, 3-4.5 cm long and 2-3.5 cm wide. Other shapes of contact surfaces 4 and 5 are possible depending on the osteotomy lines.

The contact surface 4 of step 2 is made in such a way that it provides a congruent coating of the inner surface of the wing 8 of the ilium (fixed fragment), limited on four sides, where the first side corresponds to the line 9 of the osteotomy of the ilium from the anterior superior os to the arcuate line of the pelvis, the second side corresponds to the part of the iliac crest from the line 9 of the osteotomy, the third side corresponds to the line 10, located 1.5-2 cm from the line 9 of the osteotomy, and the fourth side corresponds to the arcuate line of the pelvis.

The contact surface 5 of the step 3 is made in such a way that it provides a congruent coating of the inner surface of the acetabular fragment 11, limited on four sides, where the first side corresponds to 9 osteotomy of the ilium from the anterior superior spine to the arcuate line of the pelvis, the second side corresponds to a part of the iliac crest from the osteotomy line 9, the third side corresponds to line 12, passing from the upper border of the anterior inferior spine perpendicular to the section of the arcuate line of the pelvis in the region of the acetabulum, and the fourth side corresponds to the arcuate line of the pelvis.

In steps 2 and 3, holes 6 are made for fixing elements.

In the second stage 3, a cutout 7 is made in such a way as to ensure the possibility of visual control of the passage of cortical screws from the iliac crest through its thickness in the direction of the acetabular fragment.

The device can be manufactured based on a preliminary CT scan of the patient's pelvis using medically approved materials used for 3D printing.

The device is used as follows.

At the preoperative planning stage, a CT scan of the patient's pelvis is performed, a periacetabular osteotomy is modeled, namely, the position of the osteotomy planes of the pubic, ilium and ischium is determined, and thus the configuration of the required acetabular fragment and its reposition parameters (tilt and rotation). After that, based on the data obtained, a device for positioning the acetabular fragment with geometric dimensions that ensure the desired anatomical and functional reposition of the acetabular fragment is modeled and manufactured, for example, on a 3D printer. Then, access is gained to the pelvic bones, osteotomies are performed, obtaining an acetabular fragment of the planned configuration. After this, step 2 with contact surface 4 is positioned congruently to the inner surface of the wing 8 of the ilium and fixed with pins 13. Step 3 with contact surface 5 is positioned congruently to the inner surface of the acetabular fragment 11 and fixed with pins 13. From the crest of the ilium 8 through the plane of osteotomy of the said bone and the notch of 7 degree 3 into the acetabular fragment 11, three to four cortical screws 14 are inserted in order to fix the acetabular fragment 11 in a given position. The device is removed, the wound is closed in a generally accepted manner.

Clinical example No. 1.

Patient K.E.A., 29 years old (Fig. 6), was treated in hospital for symptomatic dysplasia of the left hip joint (Wiberg angle = 10.9°, Tonnis angle = 25.6°, femoral head extrusion index = 38.17%). Left periacetabular osteotomy was performed using a device for positioning the acetabular fragment during periacetabular osteotomy according to the described technique, which improved the accuracy of acetabulum orientation and reduced the need for intraoperative X-ray control and radiation exposure to the patient and the surgical team. The use of this device ensured that periacetabular osteotomy was performed according to the preoperative plan and avoided acetabular positioning errors and achieved the calculated angles. The second stage 3 of the device had a height of H = 22 mm on one side and H* = 5 mm on the other, the degree of correction of the Wiberg angle was 22°, the degree of correction of the acetabulum inclination angle (Sharp angle) was 15.50°. Postoperative radiographs (Fig. 7) show a satisfactory position (Wiberg angle = 31.6°, Tonnis angle = 8°, femoral head extrusion index = 12.97%) of the acetabulum fragment fixed with three cortical screws 8 (Fig. 7).

Clinical example No. 2.

Patient S.P.S., 20 years old (Fig. 8), underwent inpatient treatment for symptomatic dysplasia of the left hip joint (Wiberg angle = 19.2°, Tonnis angle = 17.2°, femoral head extrusion index = 29%). Left periacetabular osteotomy was performed using a device for positioning the acetabular fragment during periacetabular osteotomy according to the described technique. The use of this device ensured that periacetabular osteotomy was performed according to the preoperative plan and made it possible to avoid acetabular positioning errors and achieve the calculated angles. The second stage of the 3rd device had a height of H = 9 mm on one side and H* = 5 mm on the other; the degree of correction of the Wiberg angle was 16.70°, the degree of correction of the acetabular inclination angle (Sharp angle) was 12°. Postoperative radiographs (Fig. 8) show a satisfactory position (Wiberg angle = 35.9°, Tonnis angle = 5.6°, femoral head extrusion index = 10%) of the acetabulum fragment fixed with three cortical screws 8 (Fig. 9).

Clinical example 3.

Patient T.V.O., 19 years old (Fig. 10), underwent periacetabular osteotomy using a device for positioning the acetabular fragment during periacetabular osteotomy according to the described technique for symptomatic dysplasia of the right hip joint (Wiberg angle = 10.40°, Tonnis angle = 20.8°, femoral head extrusion index = 35.89%). The second stage 3 of the device had a height of H = 20 mm on one side and H* = 4 mm on the other, the degree of correction of the Wiberg angle was 21.70°, the degree of correction of the acetabulum inclination angle (Sharp angle) was 12.9°. Postoperative radiographs (Fig. 10) show a satisfactory position (Wiberg angle = 32.10°, Tonnis angle = 0.8°, femoral head extrusion index = 15.68%) of the acetabulum fragment fixed with three cortical screws 8 (Fig. 11).

Thus, the claimed utility model ensures the production of an effective device for positioning the acetabular fragment during periacetabular osteotomy, ensuring high accuracy in performing spatial orientation of the acetabulum while minimizing radiation damage.

Bibliography:

1. GANZ R. et al. A new periacetabular osteotomy for the treatment of hip dysplasias technique and preliminary results // Clinical Orthopedics and Related Research®. - 1988. - T. 232. - P. 26-36.

2. Ali M., Malviya A. Complications and outcome after periacetabular osteotomy-influence of surgical approach // Hip International. - 2020. - T. 30. - No. 1. - pp. 4-15.

3. Patent No. 2719652 C1 Russian Federation, IPC A61B 17/56, A61F 2/28, A61B 17/68. A device for fixing the mutual spatial orientation of bone fragments in an optimal anatomical and functional position during pelvic osteotomy for hip dysplasia: No. 2018146908: declared 26.12.2018: published 21.04.2020 / P.I. Baskov; applicant Federal State Budgetary Institution "Turner National Medical Research Center for Pediatric Traumatology and Orthopedics" of the Ministry of Health of the Russian Federation. - EDN LADLWA.

Claims (8)

1. A device for positioning the acetabular fragment during periacetabular osteotomy, which is a housing with a two-stage profile, each stage of which has a contact surface, the contact surface of the first stage is made congruent with the inner surface of the iliac wing, the contact surface of the second stage is made congruent with the inner surface of the acetabular fragment, and the height of the second step corresponds to the value that ensures the tilt and rotation of the acetabular fragment into the optimal anatomical and functional position. 2. The device according to item 1, characterized in that in the second stage a notch is made with the possibility of ensuring the passage of cortical screws from the iliac crest in its thickness in the direction of the acetabular fragment. 3. The device according to item 1, characterized in that the contact surfaces of the steps are made rectangular in plan, 3-4.5 cm long and 2-3.5 cm wide. 4. The device according to item 1, characterized in that through holes are made for the fixing elements.