RU209391U1 - Magnetically controlled spinal rod - Google Patents

Abstract

The utility model relates to orthopedic/neurosurgical implants, in particular to devices for the surgical treatment of scoliotic spinal deformities in children with incomplete bone growth. telescopic movement relative to the body of the regulated part, a cover-rod installed on the opposite side of the body of the regulated part, a lead screw with an external thread connecting the rotating magnetic assembly and the distraction rod by means of a screw gear, while the screw gear includes an internal thread made on the inner hollow part of the distraction rod, while the rotating magnetic assembly is made of a magnet in the form of a hollow cylinder, rigidly mounted on a shaft with supports, connected to the lead screw. the mustache of the adjustable part should be made composite, consisting of a magnet body and a distraction rod body, preferably connected by a threaded connection, and the rod cover should be connected to the magnet body also by means of a threaded connection. The reliability of the device also increases the coating of all its elements from the outside with an antibacterial composition, for example, a coating of ZnO -Ag2O-Ag2S. 3 w.p. f-ly, 1 ill.

Description

The utility model relates to orthopedic/neurosurgical implants, in particular to devices for the surgical treatment of scoliotic spinal deformities in children with incomplete bone growth.

Scoliotic deformities of the spine occupy one of the leading places in the pathology of the musculoskeletal system in children and adolescents with a tendency to increase the incidence (> 450 million children in the world). The percentage of patients with severe forms of scoliosis who require surgical treatment is 0.6%. Thus, according to preliminary estimates, more than 150 million children in the world and about 1.5 million in Russia have scoliotic spinal deformity. Of these, about 1 million in the world and 8 thousand in Russia have severe deformities that require surgical treatment [1–4].

If scoliosis is not corrected, then in the case of an early progressive form of scoliosis (early onset scoliosis - EOS), children do not live up to 20 years. Timely operation can save these patients. EOS are complex and very severe progressive deformities of various etiologies that grossly violate the anatomy of the spine and chest and often lead to the development of complications (thoracic insufficiency syndrome, etc.). The main problem in the treatment of EOS is the need to combine the correction of progressive spinal deformity and maintain growth potential [5].

The most common technique for surgical treatment of EOS is the technique of growing rods (growing rods - GR), which in recent years has been increasingly referred to as "traditional growing rods" (TGR). The advantages of TGR are well known: relative simplicity and quite satisfactory results. However, there are a number of serious shortcomings [5-7]:

surgical interventions (staged distractions) every 6-9 months under general anesthesia. Some children underwent up to 15 operations during the treatment;

a large dose of ionizing radiation due to the need for frequent radiographs;

numerous complications - each subsequent operation increases the risk of complications by 24%;

frequent hospitalizations;

negative impact on the child's psyche;

separation of children from school and their parents from work;

economic losses.

In 2014, the FDA ("Food and Drug Administration" - US Food and Drug Administration) approved the only magnetically controlled rod (MCGR - magnetic control growing rods) - the MAGEC system, which can significantly reduce the number of operations due to ambulatory non-invasive lengthening system (see, for example: https://www.nuvasive.com/procedures/spine/magec/). This became possible due to the appearance of an actuator in the rod - a growing part of the rod. Nevertheless, the installation of this implant with a reduction in the number of operations is accompanied by the appearance of a number of complications:

frequent breakage and corrosion of the rod (fracture of the locking pin);

soft tissue metallosis (23%), pseudocapsule formation around the implant, and rod destabilization. This occurs due to the pin fracture, the occurrence of the pistoning effect (telescope), as a result of which metal debris is formed inside and outside the actuator [5, 8-14];

“clunking effect” (clatter) is a sound and palpation phenomenon that occurs during magnetically controlled rod elongation due to the development of the “Slippage” phenomenon that occurs when the rod slippage in the actuator, when full internal rotation is impossible and the rod returns to starting position [12];

infectious complications and suppuration [5, 8, 9, 12, 13].

Thus, despite the reduction in the number of complications and operations compared with TGR, the use of MCGR increases implant-associated complications by 5.6 times and the risk of unscheduled operations by 4.6 times - up to 42-46% of reoperations [5, 12, 15 ]. The overall percentage of complications of MCGR use reaches 46% [16]. This necessitates further research in order to develop a more perfect type of magnetically controlled rod.

The MAGEC system is protected by several patents (US9186183(B2), US9757159(B2), US9848914(B2)), patent applications pending.

The technical solution "Magnetic implant with improved anatomical compatibility", disclosed in the application US 2020155201 (A1), the applicant NUVASIVE SPECIALIZED ORTHOPEDICS INC [US] was taken as a prototype. This technical solution is (in accordance with the first paragraph of the formula and Fig. 9A of the description) a distraction device, including an adjustable part containing a rotating magnetic assembly, and a distraction rod connected to the rotating magnetic assembly through a lead screw with an external thread, and an intermediate sleeve with with an internal thread, while the distraction rod is made with the possibility of telescopic movement relative to the body of the regulated part, and on the other side of the regulated part there is a cover-rod rigidly connected to the body of the regulated part.

The objective of the utility model was to develop a new magnetically controlled growing rod with design features that ensure simplicity and, as a result, higher reliability compared to the prototype.

This task is solved by a magnetically controlled spinal rod, including an adjustable part containing a rotating magnetic assembly, a distraction rod that can be telescopically moved relative to the body of the adjustable part, a rod cover installed on the opposite side of the body of the adjustable part, a lead screw with external thread connecting by means of a screw gear, a rotating magnetic assembly and a distraction rod, in which, according to the proposal, the screw gear includes an internal thread made on the inner hollow part of the distraction rod, while the rotating magnetic assembly is made of a magnet in the form of a hollow cylinder rigidly mounted on a shaft with supports connected to lead screw.

For easy disassembly of the device, it is expedient to make the housing of the adjustable part a composite one, consisting of a magnet housing and a distraction rod housing, preferably connected by a threaded connection.

For the same purpose, it is expedient to connect the cover-rod to the magnet body by means of a threaded connection.

The reliability of the device also increases the coating of all its elements on the outside with an antibacterial composition, for example, a coating of ZnO-Ag ₂ O-Ag ₂ S nanocomposite.

The utility model is illustrated by a drawing showing a longitudinal section of a magnetically controlled spinal rod.

The following positions are indicated on the drawing:

Magnet shaft.

Distraction rod.

Magnet body.

Magnet.

Support.

Cover-rod.

Distraction rod body.

Pad.

lead screw.

Limit pin.

Magnet shaft pin.

Sealant.

The device works as follows.

Under the influence of an external magnetic field from the remote control, the magnet 4, which has a rigid grip with the shaft 1, begins to rotate. The shaft 1 of the magnet 4 is installed in supports 5. The linear movement of the magnet 4 is limited by the presence of gaskets 8. Due to the rigid coupling of the shaft 1 of the magnet 4 with the lead screw 9, through the pin 11, torque is transmitted to the lead screw 9, which, through a threaded connection (screw drive), imparts rod 2 linear (longitudinal) movement. The linear and rotational movement of the rod 2 is limited by pins 10 and grooves in the body of the rod 2. The drive of the rod of the adjustable part of the rod is installed inside a sealed housing, consisting of a magnet housing 3, a distraction rod housing 7 and a rod cover 6. The tightness between the piston and the piston housing is ensured seal 12.

The utility model allows to achieve the following technical result in terms of reliability:

Composite execution of a rotating magnetic assembly (magnet + shaft) simplifies the manufacture and installation of reinforced supports.

The design of the screw drive without an intermediate sleeve eliminates the need for high precision and, as a result, eliminates the possibility of “sticking” and jamming.

The connection of the device elements with detachable (threaded connections) simplifies the assembly / disassembly of the device.

In addition, the design of the magnetically controlled spinal rod additionally allows:

increase the power of the neodymium magnet, which solves the problem of the development of the "Slippage" phenomenon (slippage of the rod, due to insufficient power of the magnet);

reduce the length of rod 2 in order to reduce the load on the rod to prevent rod breakage;

to reduce the length of the pin 11, which makes it more resistant to the load;

reduce the maximum elongation from 48 to 44 mm in order to reduce the load on the connection of the lead screw 9 and the magnet shaft 1, which will allow avoiding breakages of the pin 11 and at the same time keep the possible accepted Tail gaiting technique for increasing the magnetically controlled rod, taking into account the growth of the vertebral bodies in children ( elongation of 2.2 cm per year in children under the age of 5 years, 1.1 cm - at the age of 5-10 years and 1.8 cm - over 10 years).

The antibacterial coating of the ZnO-Ag ₂ O-Ag ₂ S nanocomposite makes it possible to reduce the number of infectious complications by 2 times.

Reinforced seals 12 seal the inside of the rod and prevent the development of metallosis.

Bibliography

[1] M.V.V. Nadirov N.N., Kokushin D.N., Khusainov N.O. "Comparative analysis of the results of correction of idiopathic scoliosis in children with transpedicular metal structures". Modern Problems of Science and Education, no. 1, 2017.

[2] B.S.V. Lavrov E.A. "Change in the population of the countries of the world for the period 1991-2016". Scientific Thought, vol. 23, no. 1, pp.99-104, 2017.

[3] K. O. N. Korolenko A. V. "The results of the demographic development of Russia in 2000-2016", Social space, vol. 11, no. 4, 2017.

[4] S. Negrini et al., "2011 SOSORT guidelines: Orthopaedic and Rehabilitation treatment of idiopathic scoliosis during growth", (in eng), Scoliosis, vol. 7, no. 1, p.3, Jan 2012, doi: 10.1186/1748-7161-7-3.

[5] A.A.A.M.V. Mikhailovsky "Magnetically controlled rods in early scoliosis surgery: a review of the English-language literature", Spine Surgery, vol. 17, no. 1, pp.25-41, 2020.

[6] AB Bess S., Thompson G., Sponseller P., Skaggs, Shah S., Canale S., Poe-Kochert C. "Complications in 910 growing rod surgeries: use of dual rods and submuscular placement of rods decreases complications ", Spine Journal, no. 8, pp.138-148, 2008, doi: DOI: 10.1016/j.spinee.2008.06.031.

[7] J. M. Flynn, H. Matsumoto, F. Torres, N. Ramirez, and M. G. Vitale "Psychological dysfunction in children who require repetitive surgery for early onset scoliosis", (in eng), J Pediatr Orthop, vol. 32, no. 6, pp.594-9, Sep 2012, doi: 10.1097/BPO.0b013e31826028ea.

[8] A. Ahmad, T. Subramanian, P. Panteliadis, J. Wilson-Macdonald, D. A. Rothenfluh, and C. Nnadi, "Quantifying the 'law of diminishing returns' in magnetically controlled growing rods," (in eng), Bone Joint J, vol. 99-B, no. 12, pp.1658-1664, Dec 2017, doi: 10.1302/0301-620X.99B12.BJJ-2017-0402.R2.

[9] E. Choi et al., "Implant Complications After Magnetically Controlled Growing Rods for Early Onset Scoliosis: A Multicenter Retrospective Review", (in eng), J Pediatr Orthop, vol. 37, no. 8, pp.e588-e592, Dec 2017, doi: 10.1097/BPO.0000000000000803.

[10] B. Dahl, C. Dragsted, S. Ohrt-Nissen, T. Andersen, and M. Gehrchen, "Use of a distraction-to-stall lengthening procedure in magnetically controlled growing rods: A single-center cohort study" , (in eng), J Orthop Surg (Hong Kong), vol. 26, no. 2, p.2309499018779833, 2018 May-Aug 2018, doi: 10.1177/2309499018779833.

[11] Z. Dannawi, F. Altaf, NS Harshavardhana, H. El Sebaie, and H. Noordeen "Early results of a remotely-operated magnetic growth rod in early-onset scoliosis", (in eng), Bone Joint J, vol. 95-B, no. 1, pp.75-80, Jan 2013, doi: 10.1302/0301-620X.95B1.29565.

[12] JP Cheung, P. Cahill, B. Yaszay, BA Akbarnia, and KM Cheung "Special article: Update on the magnetically controlled growing rod: tips and pitfalls", (in eng), J Orthop Surg (Hong Kong), vol. 23, no. 3, pp. 383-90, Dec 2015, doi: 10.1177/230949901502300327.

[13] H. Keskinen et al. "Preliminary comparison of primary and conversion surgery with magnetically controlled growing rods in children with early onset scoliosis", (in eng), Eur Spine J, vol. 25, no. 10, pp. 3294-3300, 10 2016, doi: 10.1007/s00586-016-4597-y.

[14] G. La Rosa, L. Oggiano, and L. Ruzzini "Magnetically Controlled Growing Rods for the Management of Early-onset Scoliosis: A Preliminary Report", (in eng), J Pediatr Orthop, vol. 37, no. 2, pp.79-85, Mar 2017, doi: 10.1097/BPO.0000000000000597.

[15] K. Y. H. Kwan et al. "Unplanned Reoperations in Magnetically Controlled Growing Rod Surgery for Early Onset Scoliosis With a Minimum of Two-Year Follow-Up", (in eng), Spine (Phila Pa 1976), vol. 42, no. 24, pp. E1410-E1414, Dec 15 2017, doi: 10.1097/BRS.0000000000002297.

[16] M.H. Hung C.W., Campbell M., Vitale M., Roye D., Roye B. "Magnetically controlled growing rod systems have higher hazard of adverse events compared to prosthetic rib constructs", In: Final Program of the 53rd SRS Meeting and Course. Bologna, Italy, p. 222. 2018.

Claims (4)

1. A magnetically controlled spinal rod, including an adjustable part containing a rotating magnetic assembly, a distraction rod made with the possibility of telescopic movement relative to the body of the adjustable part, a rod cover mounted on the opposite side of the body of the adjustable part, a lead screw with an external thread connecting by means of screw gear, a rotating magnetic assembly and a distraction rod, characterized in that the screw gear includes an internal thread made on the inner hollow part of the distraction rod, while the rotating magnetic assembly is made of a magnet in the form of a hollow cylinder, rigidly mounted on a shaft with supports, connected to the running screw, and all elements of the rod are covered with an antibacterial composition from the outside. 2. Magnetically controlled spinal rod according to claim 1, characterized in that the body of the adjustable part is made of a composite, consisting of a magnet body and a distraction rod body. 3. Magnetically controlled spinal rod according to claim 2, characterized in that the magnet body and the distraction rod body are connected by means of a threaded connection. 4. Magnetically controlled spinal rod according to claim 3, characterized in that the cover-rod is connected to the magnet body by means of a threaded connection.

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