Modern Implants Research Articles

Polyethylene liner dissociation in cementless total hip arthroplasty: Ensuring accurate diagnosis.

Uncemented acetabular components are widely used in modern total hip arthroplasty (THA). Modularity has numerous advantages including the ability to use supplementary screw fixation for the shell, and allow to switch from ceramic to polyethylene (PE) bearings and vice versa, and the use of lipped and face-changing liners. Despite these advantages, a problem with modular PE liners is dissociation. This is a rare complication in modern implants. The rate of liner dissociation is reported to be very low between 0.17% and 0.8%. Typical symptoms are sudden onset of groin pain in a previously well-functioning hip joint, followed by grinding or clicking sensations during hip joint motions indicating, that the femoral head is articulating with the metal acetabular shell rather than with the PE liner. Any newly observed noise or squeaking from a THA should undergo radiographic investigation to exclude liner dissociation. We present the case of an 88-yearold male patient who developed PE liner dissociation in a cementless THA with a Pinnacle acetabular component six years after the index operation. We recommended revision of the left hip, which was performed two days later. In the interim, the patient was advised to use a pair of crutches. During revision surgery, it was observed that the metal head made contact with the cementless cup shell without damaging it from a macroscopic standpoint. Consequently, a simple exchange of the PE liner was conducted, and a 36 mm metal head was implanted due to scratches on the original head. Early diagnosis facilitates a straightforward exchange of the liner along with the head, potentially preserving the osseous integrated cup shell and stem integrity. Routine radiologic follow-up allows to distinguish between PE liner dissociation and severe PE wear.

Pathogen inactivation mechanism with application in implantology

At the present time, a special attention is given to the large-scale using of implant treatments. Modern implants have a good rate of success, reliability and longevity, they are minimally invasive, delicate and resistant. Due to the development of some forms of pathogens at the implant-tissue contact, there are situations of poor adhesion of the implant surface to the organic tissue. The application of chemical or surgical methods in such situations are difficult. But in order to solve these phenomena, new techniques are needed to be implemented. That why it is proposed to apply ultraviolet radiation on the optical system (photonic crystals and photonic fiber crystals) of modern implants to treat the infection that can appear on the surface between the implant and the cellular tissue in the process of poor adhesion. These combinations of periodic quartz optical structures are deposited and regularly arranged (set of fibers or spheres) on the implant surface, which can be used as a large volume dispersion of ultraviolet C radiation to treat the infection at the surface between the implant and adhesion tissue. The proposed periodic optical structure contributes considerably to increasing the adhesion of the implant to the cellular tissue, thus stimulating cellular growth between the elements and the implant.

Metal-Based Implants: Review of Materials and Designs

The purpose of implants is to replace, restore, maintain or improve the functionality of various tissues and organs of the human body. Their use in modern medicine has significantly improved treatment methods and increased the quality and life expectancy of patients. The most preferable from the point of view of the possibility of imparting the required mechanical properties, the relatively low cost of the material and low production costs are metal implants. Metals and their alloys in the production of implants are superior to ceramic and polymer materials in a range of properties such as tensile strength, endurance limit, wear resistance, hardness, elasticity, viscosity, shape memory effect. The paper provides an overview of the designs of modern implants for various purposes and the metal materials used for their production. An analysis of literature sources has shown that modern implants made of metal materials represent a wide range and have significant differences in shape and size. Some of them are characterized by a small cross-section and rigidity, while possessing elastic properties. Other products are load-bearing, in some cases massive, structures. According to the proposed classification, according to their purpose, metal implants are divided into: dental, cranial, maxillofacial, vertebral, traumatological, cardiovascular and joint endoprostheses. An analysis of the advantages and disadvantages of the main metal materials used in the production of implants (corrosion-resistant steel, titanium and titanium alloys, cobalt-chromium alloys and nitinol) has been performed. It has been established that all currently used biocompatible metal materials are not completely inert towards the body. Each material in any case causes some reaction in the surrounding tissues. The greatest biocompatibility and corrosion resistance in the body is provided by technical titanium, which, however, has low strength characteristics.

Outcomes of Total Knee Arthroplasty in Patients Who Have Ehlers-Danlos Syndrome: A Matched Cohort Study

BackgroundTotal knee arthroplasty (TKA) is an excellent surgical option for patients who have end-stage knee osteoarthritis. While rates of major postoperative complications have steadily decreased with modern implants and operative techniques, contemporary outcome data for patients who have Ehlers-Danlos syndrome (EDS) are scarce. The goal of this study was to compare complication rates after primary TKA in patients who have EDS versus matched controls. MethodsA large administrative database was used to identify patients who underwent primary TKA from 2009 to 2020. Patients who had a diagnosis of EDS were identified by International Classification of Diseases Coding. Propensity scores were utilized to match these patients with controls at a 1:4 ratio based on age, sex, and various comorbidities. Multivariable logistic regression analysis was used to compare the rates of medical and surgical complications at 90 days and 2 years. A total of 188 patients who had EDS and 752 controls were included in this study. ResultsAfter univariate analysis, Ehlers-Danlos patients exhibited significantly higher rates of wound complications (4.8 versus 0.9%, P = .001) at 90 days. When adjusted for comorbidities, Ehlers-Danlos patients still exhibited significantly increased odds of developing wound complications (odds ratio: 7.06; P < .001). ConclusionsPatients who have EDS undergoing TKA exhibited significantly higher rates of wound complications within 90 days postoperatively compared to matched controls. Rates of instability, manipulation under anesthesia, periprosthetic joint infection, aseptic loosening, and aseptic revision arthroplasty did not significantly differ between the cohorts. This study found generally favorable short-term outcomes of TKA in this population; however, the inability to control for implant type and other confounding variables may have influenced the lack of difference in complication rates at 2 years. Surgeons should monitor for the potentially increased risk of wound complications and consider the possible need for increased constraint in this population during preoperative planning.

Midterm follow-up of the Nexel total elbow arthroplasty

IntroductionAseptic loosening is one of the most common complications of total elbow arthroplasty (TEA). Modern implants, such as the Nexel, have been designed in an attempt to decrease loosening. The present study aims to report implant survivorship, radiographic assessment of loosening and lucency, and patient-reported outcome measures (PROMs) in patients treated with the Nexel TEA at mid-term follow-up. MethodsConsecutive series of adult patients underwent TEA using the Nexel by a single surgeon via standardized technique. Patients with minimum 3 year follow-up with radiographic and PROM data were included. Survivorship was defined by the absence of revision. Loosening was assessed via Wrightington method by three independent fellowship-trained shoulder and elbow surgeons. Lucency was analyzed across individual radiographic zones on orthogonal radiographs. PROMs included the Quick Dash (QDASH), Patient Rated Elbow Evaluation (PREE), and EuroQoL (EQ5D). Results38 consecutive patients (22 female, 16 male) with mean age of 67 underwent TEA via triceps-sparing isolated medial window approach. Mean follow-up was 5.5 years (range 3-9). Primary diagnoses were: 19 osteoarthritis (OA), 9 rheumatoid arthritis (RA), 9 post-traumatic arthritis (PA), 1 conversion of elbow arthrodesis. Overall survivorship was 97.4%, with one patient undergoing revision for infection. Loosening was found in 5.3% of elbows, averaged across three observers. Lucency was most pronounced at the level of the humeral condyles. PROMs demonstrated significant and clinically meaningful improvements in 76%, 92%, and 73% of patients for QDASH, PREE, and EQ5D, respectively. No significant correlations were found between patient age, gender, loosening, lucency, and PROMs. ConclusionAt mid-term follow-up, the Nexel TEA demonstrated excellent overall survivorship and low rate of implant loosening. The single failure requiring revision for infection was conversion of a prior elbow arthrodesis. PROMs overall exhibited marked and consistent improvement from preop to final postop follow-up. Although promising, these results should be interpreted with some caution as long term data regarding this prosthesis are still lacking.

Is 80% satisfaction still the expectation in modern TKA mechanically aligned with robot assist? We think not

Several studies reported that20% of patients were unhappy with the outcome of their total knee arthroplasty (TKA). Having commenced robot assist TKA whilst maintaining the goal of implanting the prosthesis to a neutral mechanical axis, we reviewed our patients to find out if we also have a 20% rate of patients being unhappy with the outcome of their knee replacement surgery. We hypothesized that rate of patient satisfaction would be higher than 90% with robot-surgical assistant (ROSA) technique. The first 175 patients who underwent ROSA TKA were reviewed at a minimum of 1 year postoperatively. All TKAs were performed using ROSA technique with Persona cementless prosthesis aiming to restore neutral mechanical coronal alignment with flexion gap balancing. We investigated whether or not the patients were happy they had their knee replacement surgery and whether they were happy with the outcome. 165 (94%) of 175 patients, were contactable with 1 deceased and 9 uncontactable. From the 165 patients who participated in the study, 95% of patients were happy they had the surgery done and 93% were happy with the outcome of their knee replacement. A sub analysis showed that patients who had simultaneous bilateral TKA were significantly less likely to be happy than staged procedures (p < 0.05). Total knee replacement utilising robot technique with modern implants and aiming for mechanical coronal alignment of the implants to restore the mechanical axis with flexion gap balancing may result in > 90% of patients being happy with the outcome of their surgery.

The Evolution &amp; Outcomes of Total Wrist Arthroplasty: Current Concepts

Over the last several decades, total wrist arthroplasty design and outcomes have significantly improved. The development of modern wrist arthroplasty began in the 1960s with a silicone spacer implant, which has progressively evolved to the metal-on polyethylene modular implants utilized today. Modern implants have been shown to have high patient satisfaction and increased 5-10 year survivorship; however, the overall utilization of total wrist arthroplasty has decreased in the United States since 2001. This could be due to several reasons, including improved modern therapies for rheumatoid arthritis preventing end-stage wrist disease, reliable outcomes with arthrodesis, and the high complication and revision rates of early total wrist implants. This review will discuss the design evolution of total wrist implants, which can be divided into four distinct generations. This review also presents the most recent outcome, complication, and survivorship results for the modern 4th generation of total wrist implants.

Is the anterior approach still superior to posterior correction in AIS regarding correction, fusion levels and kyphosis when modern posterior systems are used?

PurposeThe aim of our study is to compare anterior and posterior corrections of thoracic (Lenke I) and lumbar (Lenke V) curves when modern posterior pedicle screw systems with vertebral derotation techniques are used. Curves that could not be corrected with both systems were excluded.MethodsA thoracic group (N = 56) of Lenke I AIS patients (18 anterior and 38 posterior) and a lumbar group (N = 42) of Lenke V patients (14 anterior and 28 posterior) with similar curves < 65° were identified.ResultsThoracic group The mean postoperative correction (POC) was 68 ± 13.4% in the anterior and 72 ± 10.5% in the posterior group. The postoperative change in thoracic kyphosis was +4° and +5° respectively. The median length of fusion was eight segments in the posterior and seven segments in the anterior groups. In 89% the LIV was EV or shorter in the anterior, and in 71% of the posterior corrections.Lumbar group The mean POC was 75 ± 18.3% (anterior) and 72 ± 8.5% (posterior). The postoperative gain in lumbar lordosis was 0.8° (anterior) and 4° (posterior). The median length of fusion was five segments in both groups and there was no difference in relation of the LIV to the EV.ConclusionWith modern implants and derotation techniques, the posterior approach can achieve similar coronal correction, apical derotation and thoracic kyphosis with similar length of fusion and better lumbar lordosis restoration.

(158) Comparison Implants for Penile Girth Enlargement: PPLA Shaft vs Silicone Implant

Abstract Introduction Male dissatisfaction with the penis size is the most common manifestation of penile dysmorphophobia. Despite the diversity of penis enlargement methods a single safe technique that fully satisfies patients has not yet been developed. Objective The aim of this work is to compare the results of a combined operation on installation of a silicone implant or a porous polylactic acid (PPLA) scaffold impregnated with autologous stem cells with simultaneous ligamenotaxis to increase the length and circumference of the penis. Methods In 2017–2023 there were performed penis enlargement surgeries in 3 centers. In Ukraine and Poland 38 patients from were operated with implantation of a porous Max Pol PLLA scaffold, and in Mexico implantation of silicone implants Peniflex in 36 patients was performed. The results of penis enlargement were evaluated in the early (2 months) and long-term (36 months) periods. Results While implanting a silicone implant the majority of the patients - 31 (86.1%) are satisfied with the result, 27 (75%) patients mention an improvement in sexual life, 31 (86.1%) also mention an increase in their own self-sufficiency. At the same time, some patients mentioned the following complications: 2 (5.6%) patients mentioned displacement of the silicone matrix, 1 (2.8%) patient mentioned prolapse of the implant, 1 (2.8%) patient mentioned a decrease in erection (which did not improve after removal of the implant), in 1 (2.8%) case the silicone implant had to be removed due to the fact that the patient did not liked the appearance. While using a collagen-like matrix made of polymerized polylactic acid impregnated with autological stem cells in 38 patients, we have seen one significant complication - prolapse that caused the removal of the matrix (in men that had denied circumcision before implantation). However, 5 (13.2%) patients required additional polylactic acid gel injections between 6 and 36 months to optimize the shape or volume of the penis. 34 (89.5%) patients mentioned an improvement in the sexual function and sexual sensations of their partner, harmonization of relationships in a couple, and 36 (97.4%) men - an increase in a sense of self-sufficiency. In 3 years most of the patients 26 (68,4%) have been satisfied with particularly resolved implant but 13 (34.2) patients want to add some PLA gel as injection for penile girth recovery. Conclusions Thus, modern implants can improve the size and appearance of the penis, improve the quality of sexual life and the feeling of self-sufficiency in operated men. The use of silicone implants is simpler, it require only long drain 3–5 days. Most of operated patients were satisfied results of silicone implant. The use of a polymer matrix impregnated with autologuous stem cells requires a special biostem cell laboratory, more time for preoperative rehabilitation, but can be considered as more philological. Both methods can be considered as permanent and quite safe for penis enlargement. Disclosure No.

New Horizons of Cementless Total Knee Arthroplasty.

Considering the increasing number of young and active patients needing TKA, orthopedic surgeons are looking for a long-lasting and physiological bond for the prosthetic implant. Multiple advantages have been associated with cementless fixation including higher preservation of the native bone stock, avoidance of cement debris with subsequent potential third-body wear, and the achievement of a natural bond and osseointegration between the implant and the bone that will provide a durable and stable fixation. Innovations in technology and design have helped modern cementless TKA implants to improve dramatically. Better coefficient of friction and reduced Young's modulus mismatch between the implant and host bone have been related to the use of porous metal surfaces. Moreover, biologically active coatings have been used on modern implants such as periapatite and hydroxyapatite. These factors have increased the potential for ingrowth by reducing micromotion and increasing osteoconductive properties. New materials with better biocompatibility, porosity, and roughness have been introduced to increase implant stability. Innovations in technology and design have helped modern cementless TKA implants improve primary stability in both the femur and tibia. This means that short-term follow-up are comparable to cemented. These positive prognostic factors may lead to a future in which cementless fixation may be considered the gold-standard technique in young and active patients.

Failure Rate and Early Complications of Thumb Carpometacarpal Joint Replacement-A Multicenter Retrospective Study of Two Modern Implant Designs.

Joint replacement arthroplasty for the treatment of thumb osteoarthritis is gaining popularity as recent studies have demonstrated better pinch and grip strength and faster rehabilitation. Our aim was to identify early complications in modern implant designs using a multicenter study. A total of 381 patients who underwent thumb carpometacarpal replacement surgery in six participating hospitals were enrolled. The complications included were fractures, dislocations, infections, tendon and nerve injuries, and complex regional pain syndrome. Major complications were defined as a failure to implant the prosthesis, revision surgery to remove the implant, and any other need for further surgical intervention. The secondary outcomes were any other complications treated non-surgically and the timing of the complications. Eleven procedures failed, and these patients were treated with trapeziectomies. Twelve other patients required repeat surgical interventions. Minor adverse events occurred in 25.4% of the cases, and transient irritation of the superficial radial nerve and De Quervain tendinopathy were the most prevalent complications. Although this cohort depicted the learning curves of multiple surgeons, our study demonstrated low short-term failure rates. An inability to achieve primary stability of the cup in the trapezium was the leading cause of failure. Dislocations and other major complications with modern implants were very few.

Arthroplasty of the hand and wrist

Arthrosis and autoimmune arthritis frequently lead to major impairment of hand function. Primary therapy consists of well- tried conservative treatments and joint preserving surgical options for special indications. In advanced stages silicon spacers remain the gold standard surgical option for replacement of proximal interphalangeal and metacarpophalgeal joints of the fingers. Alternatively, surface replacement prostheses can restore the biomechanical properties of these joints more porperly. In case of the carpometacarpal (CMC) joint of the thumb, arthroplasty is gaining popularity as modern implants show excellent mid-term outcome. Although current forth generation implants for wrist replacement are promising, total wrist arthroplasty is currently reserved for exceptional indications.

Total Hip Arthroplasty in the Ultrayoung.

Total hip arthroplasty (THA) procedures provide a surgical option for "ultrayoung" patients ≤30 years old with end-stage hip arthropathy. This has historically been coupled with concerns over early component failure and challenging surgical technique leading to increased risk of overall morbidity. The purpose of this study is to better elucidate the poorly defined indications and outcomes for THA in ultrayoung patients with end-stage hip disease. A total of 40 THAs in 35 patients ≤30 years old performed at our institution from 2009 to 2016 were retrospectively followed for an average of 2 years (median 11 months, interquartile range 1-31.25). Primary outcome measure was THA revision. Patient demographics were compared against outcomes. The effects on revision rate of hip joint pathology and type of bearing surface were investigated. T-test, chi-square test, and bivariate correlation were performed to determine statistical significance (P < .05). Machine learning was used to determine the normalized important factor leading to THA revision. Fifteen male and 25 female patients were included. Median patient age was 23 (interquartile range 19-27) years, with an average body mass index of 27.0 ± 7.9. A majority of THAs were indicated for osteonecrosis (32) and bearing surface type was predominantly metal-on-highly cross-linked polyethylene (36). The overall revision rate was 7.5%, without a correlation between revision and demographic characteristics. Revision surgery was significantly correlated with bearing surface type (P= .028). Important factors for revision were age (100%), bearing surface type (84.7%), and body mass index (52.1%). In patients ≤30 years old, THAs performed with the use of modern implants and surgical methods show satisfactory survivorship and functional outcomes with short-term follow-up.

Review of Contemporary Applications of Piezoelectric - Surgery in Modern Implant Dentistry

Review of Contemporary Applications of Piezoelectric - Surgery in Modern Implant Dentistry

Foreign Body Reaction (Immune Response) for Artificial Implants Can Be Avoided: An Example of Polyurethane in Mice for 1 Week.

Despite great success with artificial implants for the human body, modern implants cannot solve major health problems. The reason is an immune reaction of organisms to artificial implants, known as the foreign body reaction. We have found a way to avoid or decrease the foreign body reaction. The surface of an artificial implant is modified with condensed aromatic structures containing free radicals, which provide a covalent attachment of host proteins in a native conformation. The total protein coverage prevents the direct contact of immune cells with the implant surface, and the immune cells are not activated. As a result, the immune response of the organism is not generated, and the artificial implant is not isolated from the tissue; there is no collagen capsule, low activity of macrophages, low cell proliferation, and low inflammatory activity.

Total Knee Arthroplasty in Haemophilia: Long-Term Results and Survival Rate of a Modern Knee Implant with an Oxidized Zirconium Femoral Component.

(1) Background: Total Knee Arthroplasty (TKA) in patient with haemophilia (PWH) has usually been performed with the use of cobalt-chrome femoral and titanium tibial components, coupled with standard polyethylene (PE) inserts. The aim of this retrospective study was to evaluate the long-term outcomes and survival rates of TKA in a series of consecutive PWH affected by severe knee arthropathy at a single institution. (2) Methods: We followed 65 patients undergoing 91 TKA, implanted using the same implant, characterized by an oxidized zirconium femoral component, coupled with a titanium tibial component, and a highly crosslinked PE. At 1, 6, and 12 months; then every year for 5 years; and finally, every other 3 years, all patients were scored for pain (VAS), function (HJHS; KSS), ROM, and radiographic changes. Kaplan-Meier survivorship curves were used to calculate the implant survival rates. (3) Results: The mean follow-up was 12.3 years (4.2-20.6). All clinical and functional scores improved significantly from preoperatively to the latest follow-up (VAS: from 6.9 to 1.3; HJHS: from 13.4 to 1.9; KSS: from 19.4 to 79; ROM: from 42.4° to 83.6°). The overall survivorship of the implants was 97.5% at the latest follow-up. (4) Conclusions: The present series showed a high survival rate of specific implants potentially linked to the choice of an oxidized zirconium coupled with a highly crosslinked PE. We promote the use of modern implants in these patients in order to ensure long-lasting positive outcomes.

INCIDENCE, TREATMENT, AND OUTCOME OF MODERN DUAL MOBILITY DISSOCIATIONS

Dual mobility (DM) components are increasingly used to prevent and treat dislocation after total hip arthroplasty (THA). Intraprosthetic dissociation (IPD) is a known rare complication of these implants and has reportedly decreased with modern implants. The purpose of this paper is to report the diagnosis and treatment of modern DM IPD.1453 DM components were implanted between 2010 and 2021. 695 in primary and 758 in revision THA. 49 hips sustained a dislocation of the large head and 5 sustained an IPD at presentation. 6 additional IPD occurred at the time of reduction of large head. The average age was 64, 54% were female and the mean follow-up was three years. Of the 11 IPD, 8 had a history of instability, 5 had abductor insufficiency, 4 had prior lumbar fusion, and 3 were conversions from fracture.The overall IPD incidence was 0.76%. Ten of the 11 DM IPD were missed at initial presentation or at the time of reduction, and all were discharged with presumed reduction. The mean time from IPD to surgical treatment was 3 weeks. One patient died with an IPD at 5 months. A DM head was reimplanted in six, two underwent revision of the acetabular component with exchange of DM head, and four were revised to a constrained liner. The re-revision rate was 55% at a mean 1.8 years. None of the patients who underwent cup revision required subsequent re-revision while half of the constrained liners and exchange of DM heads required re-revision.The overall rate of DM dislocation or IPD is low. It is critical to identify an IPD on radiographs as it was almost universally missed at presentation or when it occurred iatrogenically. For patients presenting with IPD, the surgeon should consider acetabular revision and conversion to a constrained liner or a larger DM, with special attention to removing impinging structures that could increase the risk of re-dislocation.

MRI surveillance after translabyrinthine vestibular schwannoma resection and cochlear implantation: is it feasible?

PurposeCochlear implantation in patients with vestibular schwannomas is of increasing importance and interest. Two remaining challenges are the assessment of conduction of the cochlear nerve and the possibility of postoperative surveillance with magnetic resonance imaging. The aim of the current study was to assess follow-up imaging and determine the visibility of the internal auditory canal after vestibular schwannoma resection and cochlear implantation as well as in patients with persistent vestibular schwannomas and cochlear implants in place. Visibility of the internal auditory canal, cerebellopontine angle, and labyrinth were evaluated and graded.MethodsFor this retrospective study, 15 MR examinations of 13 patients after translabyrinthine vestibular schwannoma resection and ipsilateral cochlear implantation were included. All patients had been implanted with an MED-EL cochlear implant. Magnetic resonance imaging was carried out on a 1.5T device. All patients were prepped according to the manufacturer’s recommendations.ResultsAll 15 examinations were carried out without any adverse event during imaging, such as pain, magnet dislocation, or malfunction. The internal auditory canal and the cerebellopontine angle were sufficiently visible in all cases to allow for vestibular schwannoma follow-up.ConclusionMagnetic resonance imaging surveillance of the internal auditory canal following vestibular schwannoma resection and cochlear implantation is feasible and safe with modern implants with a 1.5T magnetic resonance imaging device using metal artifact reduction sequences. Necessary follow-up imaging should not be a contraindication for cochlear implantation in patients with vestibular schwannomas.

(486) Different Methods Penile Girth Enlargement

Abstract Introduction Male dissatisfaction with the size of the penis is the most common manifestation of penile dysmorphophobia. Despite the variety of penis girth enlargement methods, a single safe technique that satisfies patients has not yet been developed. Objective The aim of the work was to compare the results of a combined operation to install a collagen-like matrix impregnated with autologous stem cells with simultaneous ligamentotomy to increase the circumference of the penis and Polylactic Gel injection. Methods In 2017-2022, penis enlargement surgeries were performed in 2 centers. In 38 patients from Ukraine and Poland, . performed the implantation of the Max Pol porous matrix, and injections of the polylactic acid gel were performed at the other Clinic. The results of penis enlargement were evaluated in the early (2 months) and long-term (36 months) terms. Results When using a collagen-like matrix -Scaffolf made of polymerized polylactic acid impregnated with own stem cells in 38 patients, we did not encounter complications that caused the removal of the matrix. However, 5 patients required additional polylactic acid gel injections between 6 and 36 months to optimize the shape or volume of the penis. In 4 cases (10.5%), patients underwent circumcision in the period up to 3 years, as the head did not open well due to the enlarged trunk. 34 (89.5%) patients noted an improvement in the sexual function and sexual sensations of their partner, harmonization of relationships in a couple, and 36 (94.7%) men - an increase in a sense of self-sufficiency and self-confidence. In 68 patients, Polylactic Acid Gel was used to enlarge the penis. It was injected under the skin of the penis in a volume of 15 ml per 1 procedure. As a rule, we performed 2-4 treatments (30-60 ml) with an interval of 1 month. No significant complications were noted. In 11 cases (16.4%), patients had to undergo circumcision within 3 years, due to the impossibility of retracting the foreskin. Most of patients noted an improvement in the sexual function and sexual sensations of their partner, harmonization of relationships in a couple, and 61 (91.%) men - an increase in a sense of self-sufficiency and self-confidence. Conclusions Thus, modern implants can improve the size and appearance of the penis, improve the quality of sexual life and the feeling of self-sufficiency in operated men. The use of a polymer matrix impregnated with one's own stem cells requires a special laboratory, more time for perioperative preparation and postoperative rehabilitation. The use of polylactic acid gel injections does not require anesthesia, operating room, is more physiological, and can be considered as the standard of safe penis enlargement. The frequency of the need for circumcision after gel injection is slightly higher at 3 years of follow-up compare with scaffold implantation, possibly due to the greater addition of penile volume. Disclosure No

TiNi Alloy Lattice Structures with Negative Poisson Ratio: Computer Simulation

Today, one of the problems of modern implants is their high rigidity, which can lead to bone resorption at the interface between the implant and the bone and to the gradual detachment of the implant. In addition, implant detachment can occur due to the positive Poisson's ratio of the implant along its entire length. This phenomenon is described in detail in [1]. As a possible solution to these problems, it is proposed to use lattice structures with negative Poisson's ratio from TiNi alloy. This alloy has a fairly low modulus of elasticity - about 48 GPa. The use of a porous (lattice) structure of an implant made of TiNi alloy will reduce the modulus of elasticity and bring it closer to the modulus of human cortical bone – 12-17 GPa [2], and possibly the modulus of elasticity of cancellous bone – 0.1-5 GPа [3]. In this work, a computer numerical simulation of strut based lattice structures with several variants of unit cell topology with a negative Poisson's ratio is carried out. For the obtained structures, the following characteristics were calculated - elastic modulus (Young's modulus), modulus of elasticity in shear, Poisson's ratio. The modeling process is implemented using the ANSYS 2019 R2 SpaceClaim finite element analysis package. The data obtained confirmed the promising possibility of modeling and fabricating lattice structures with a low elastic modulus and negative Poisson's ratio from a TiNi alloy. Also, on the basis of this data, conclusions about the influence of the topology and porosity of unit cells on the resulting characteristics of the lattice structure were made.