Antimicrobial Activity of the Most Common Antibiotic-Releasing Systems Employed in Current Orthopedic Surgery: in vitro Study

PURPOSE OF THE STUDY Infections of joint replacements represent one of the most serious problems in contemporary orthopedics. The joint infections treatment is usually multimodal and involves various combinations of drug delivery and surgical procedures. The aim of this study was to evaluate and compare the bacteriostatic and bactericidal properties of the most common antibiotic carriers used in orthopedic surgery: bone cements mixed with antibiotic and porous calcium sulfate mixed with antibiotic. MATERIAL AND METHODS Three commercial bone cements (Palacos®, Palacos® R+G, Vancogenx®) and commercial porous sulfate (Stimulan®) were prepared with a known concentration of vancomycin (a glycopeptide antibiotic). Specifically, for the purpose of our study, the testing specimens were prepared to release 0, 1, 2, 4, 8, 16, 32, 64, 128, 256, and 512 mg of vancomycin into 1 liter of solution. The specimens with increasing amount of antibiotic were placed in a separate tubes containing 5 mL of Mueller-Hinton broth inoculated with a suspension (0.1 m, McFarland 1) of the reference strain CCM 4223 Staphylococcus aureus to evaluate their bacteriostatic properties (broth dilution method). After this initial incubation and evaluation of the broth dilution method, an inoculum from each tube was transferred onto blood agar plates. After another 24-hour incubation under the same conditions, we evaluated the bactericidal properties (agar plate method). As many as 132 of independent experiments were performed (4 specimens × 11 concentrations × 3 repetitions = 132). RESULTS The bacteriostatic properties of all investigated samples were excellent, perhaps with the exception of the first bone cement (Palacos®). The sample Palacos® started to exhibit bacteriostatic properties at concentrations ≥ 8 mg/mL, while all other samples (Palacos R+G®, Vancogenx®, and Stimulan®) were bacteriostatic in the whole concentration range starting from 1 mg/mL. The bacteriocidic properties did not show such clear trends, but correlated quite well with different properties of the investigated samples during mixing - the most homogeneous samples seemed to exhibit the best and the most reproducible results. DISCUSSION The reliable and reproducible comparison of ATB carriers is a difficult task. The situation is complicated by high numbers of local antibiotic carriers on the market, numerous antibiotics used, and differences in clinical trials at different laboratories. Simple in vitro testing of bacteriostatic and bacteriocidic properties represents a simple and efficient approach to the problem. CONCLUSIONS The study confirmed that the two most common commercial systems used in the orthopedic surgery (bone cements and porous calcium sulfate) prevent bacterial growth (bacteriostatic effect), but they may not be 100% efficient in complete elimination of bacteria (bacteriocidic effect). The scattered results in the case of bacteriocidic tests seemed to be connected with the homogeneity of ATB dispersion in the systems and with the lower reproducibility of the employed agar plate method. Key words: local release of antibiotics; bone cements; calcium sulfate; antimicrobial susceptibility.

[Repeated Sterilization of Articular Components of Joint Replacements with Ethylene Oxide Does Not Affect the Structure and Properties of UHMWPE]

PURPOSE OF THE STUDY In clinical practice UHMWPE is the most commonly used material for manufacturing articular components of joint replacements. The purpose of this study is to find out whether repeated ethylene oxide sterilization results in oxidative degradation of UHMWPE or not and also whether the oxidative degradation of various types of ethylene oxide-sterilized UHMWPE depends on storage time or not. MATERIAL AND METHODS The set included 12 samples of UHMWPE (three samples with different modifications (virgin PE, with E vitamin and cross-linked with thermal treatment) and different number of sterilizations (0×-3×)). The set also included 8 samples of commercial components of hip or knee replacements sterilized with ethylene oxide and stored for different storage periods. The oxidative degradation was assessed by infrared microspectroscopy, based on which the oxidation index (OI), transvinylene index (VI), crystallinity index (CI) and E vitamin index (EI) were calculated. Mechanical properties of UHMWPE were obtained through microhardness measurements. Statistical processing of the results was performed. RESULTS In all the samples, very low oxidative degradation values were reported (most OI values < 0.1). All radiation crosslinked UHMWPE samples showed an increased VI index and a slightly lower crystallinity index. All unmodified samples (irrespective of whether or not and how many times or how long ago the samples were sterilized with EtO) had almost zero value of VI. Changes in crystallinity were negligible (in the rage of 0.56-0.63), which required very accurate measurements of micromechanical properties. Yet, linear correlation was established between microhardness and crystallinity. DISCUSSION All the mentioned indices changed as anticipated: OIs were very low and slightly increased with time of storage, VIs of radiation crosslinked samples grew in proportion to the total gama radiation dose, CIs decreased in samples thermally treated by remelting, and EIs were very low due to negligible concentration of stabiliser (0.1%) in the samples of medical grade UHMWPE. CONCLUSIONS All samples showed zero or minimum oxidative degradation. This confirmed that neither ethylene oxide sterilization, nor multiple EtO sterilization or longer storage of polymer after ethylene oxide sterilization result in major oxidative degradation. Key words: UHMWPE, ethylene oxide, sterilization, oxidation, infrared spectroscopy, microhardness.

Reverse Total Shoulder Arthroplasty: 14-Year Clinical Experience with 496 Performed Arthroplasties

PURPOSE OF THE STUDY Reverse total shoulder arthroplasty (RSA) can be considered a proven method for the treatment of the most severe shoulder joint affections. In this study, we present 14-year experiences of the authors with the LimaCorporate SMR® RSA system in 496 cases. MATERIAL AND METHODS Included in the study are 496 RSAs performed between 2007 and 2020. We successfully followed up 368 shoulders in 358 patients. This was a prospective study with function being evaluated preoperatively and at the last follow-up in 2020. We evaluated the range of motion in active elevation and the classic Constant Score (CS). According to this score, the pain level was also evaluated. Standard statistical methods were used with a paired t-test used for comparisons of values. RESULTS The mean follow-up in our group was 5.5 years (0.7-13.6, SD 3.22, median 4.96). Indications were: primary osteoarthritis (84), acute trauma (69), posttraumatic sequelae (79), cuff tear arthropathy (37), RA (29), chronic dislocations (18), final treatment of infectious complications (7), avascular necrosis (6), tumours (4) and TSA revisions (9). The mean post-operative CS of all patients was 71.9 (2-94, SD 11.26, median 73). The mean post-operative active elevation was 127.35° (30°-180°, SD 28.36, median 130°). The mean pain level at final follow-up was 0.65 (0-3, SD 0.65, median 1). There was a statistically significant improvement In the CS (26.9 to 71) and the final achieved elevation (48.5° to 127.35°) in all groups except acute traumas for obvious reasons. A significant decrease in pain (2.8 to 0.65) was observed in all groups. We saw no implant failures or UHMWPE component wear. DISCUSSION We compared our results with those published by other authors. When considering the functional outcomes, our results are comparable with those published previously. Compared to other studies, an interesting result is the low incidence of scapular notching. In our cohort of patients, it was only present in 10 (2.7%) cases. We attribute this to the design of the SMR® implant which meets the main criterium of a modern shoulder arthroplasty system: modularity of both glenoid components. The glenospheres are available in 36, 40 and 44mm sizes with standard and distalised options. Furthermore, the system also contains the Axioma® revision glenoid component. Humeral stems are available in a range of sizes and lengths including revision stems. The humeral body is also available in two sizes. The short variant is optimal for revision with hemiarthroplasty to reverse conversion. CONCLUSIONS During a period of 14 years, we performed 496 implantations of RSAs using the SMR® system. We evaluated 368 cases with an average follow-up of 5.5 years. During long-term follow-up we experienced no implant failures or complications indicative of any constructional insufficiencies. We saw no signs of UHMWPE liner wear. The SMR® system allows for treatment of even the most complex shoulder affections due to its high modularity. Key words: shoulder joint replacement, reverse shoulder arthroplasty, SMR®, Axioma®, outcomes, ROM, scapular notching, complication, polyethylene wear, UHMWPE.

Does the Femoral CCD Angle Measurement in a Standard AP Projection Correlate with the True Anatomical Shape of the Femur?

PURPOSE OF THE STUDY This study aims to ascertain whether a high anteversion of the femoral neck can influence the measurement of the caputcollum-diaphyseal (CCD) angle on a plain anteroposterior (AP) radiograph of the proximal femur. MATERIAL AND METHODS We developed a new method of measuring the CCD angle and femoral neck version of the femur. This was done with the use of a computer program that utilised the measurement of the entire visualised area of femoral neck and shaft to calculate their long axis. Using this method, we measured the CCD angle and femoral neck version (FNV) of 100 photographed cadaveric femurs in two projections: The condylar line (CL) projection and the femoral neck (FN) projection. The same method was applied to 50 radiographs of the same femurs. The femurs were divided into three groups depending on the femoral neck version: Retro (FNV of <0°), Normal (FNV of 0-15°) and Ante (FNV of >15°) RESULTS We found a statistically significant difference in the CCD angle measured in the FN and CL projections in the Normal and Ante groups but not in the Retro group. There is a significant correlation between the increase in FNV and the difference between the measured CCD values in the FL and CL projections. The femoral neck version of our cadaveric femurs varied from -14. 4° to 31. 5° which is a range of more than 35°. CONCLUSIONS From the results, it is clear that with an increase in femoral neck anteversion, there is a statistically significant difference in the CCD angle measured between the two projections. This difference can be up to almost 10°. Surgeons should be aware of the limitation of the AP projection when planning for surgery on the hip. Key words: femoral neck anteversion, CCD angle, templating, preoperative planning.

[Comparison of the Quality of the Most Frequently Used New UHMWPE Articulation Inserts of the Total Hip Replacement]

PURPOSE OF THE STUDY For an orthopedic surgeon it is difficult or even impossible to estimate the real quality of ultrahigh molecular weight polyethylene (UHMWPE) liners that are used in the total joint replacements (TJR) just on the basis of information given by the manufacturers. At the same time, the quality of the UHMWPE liner can impact strongly on the total lifespan of the implanted TJR. This work aims at independent, objective comparison of properties of the UHMWPE liners for total hip replacements (THR), which are most frequently used in the Czech Republic. MATERIAL AND METHODS We analyzed seventeen most frequently implanted UHMWPE cups of different manufacturers implanted in the Czech Republic between 2014 and 2015 and four control samples prepared by standard industrial-scale procedures according to our instructions, whose modification (crosslinking, thermal treatment, stabilization and sterilization) was known in detail. The UHMWPE polymer was characterized by four independent microscale methods, suitable for relatively small and irregular specimens such as THR cups: infrared microspectroscopy (IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). RESULTS The employed methods yielded quite complete information about the investigated UHMWPE materials. IR spectra enabled us to calculate oxidation indexes (OI, measure of oxidative damage), trans-vinylene indexes (VI, measure of absorbed radiation dose during crosslinking and/or sterilization) and crystallinity indexes (CI, amount of crystalline phase that strongly influences mechanical performance). DSC curves were employed in calculation of crystallinities (wc, proportional to CI) and melting points (Tm, proportional to the average thickness of crystalline lamellae). MH measurements confirmed that the observed structure changes showed a real impact on mechanical properties. TGA experiments gave rough estimate of stabilization and, consequently, possible long-term oxidation resistance. Significant correlations among oxidative damage (OI), crystallinity (CI, wc) and microhardness (Hv) were statistically proven. The highest oxidative degradation was usually observed in samples thermally treated by annealing and/or sterilized by gamma irradiation. DISCUSSION The results confirmed our expectations that the UHMWPE liners from various manufacturers can be significantly different as far as their molecular structure, supermolecular structure, and mechanical properties are concerned. The differences among the various UHMWPE can be expected to increase after the implantation during in vivo. CONCLUSIONS From the clinical practice point of view, the results showed the following facts: (i) In the field of THR, all manufactures prefer crosslinked types of UHMWPE due to their increased wear resistance; non-crosslinked UHMWPEs are regarded as obsolete. (ii) Most of the manufacturers prefer ethylene oxide or gas plasma sterilization to gamma sterilization because the gammasterilized UHMWPEs exhibit lower long-term oxidation resistance. (iii) Modern trend is the stabilization of UHMWPEs with vitamin E. Key words: UHMWPE, hip replacements, oxidative degradation, infrared spectroscopy, microhardness.

[The Risk of Total Joint Replacement Infectious Complications in Relation to the UHMWPE Particle Adhesion Area]

PURPOSE OF THE STUDY Periprosthetic joint infection is a major complication which in most of the cases requires a long-term administration of antibiotics and often necessitates undergoing multiple challenging surgeries. Bacterial adhesion to foreign material is one of the key risk factors associated with periprosthetic joint infection. The foreign material with large adhesion area might be also the UHMWPE (Ultrahigh molecular weight polyethylene) particles released during the wear process from the surface of articulating components. The purpose of this study is to evaluate potential adhesion areas of wear particles in relation to diverse distribution of the size and shapes of wear particles in periprosthetic tissue and to assess an increase in the risk of infectious complications associated with an increase in the adhesion area of wear particles. MATERIAL AND METHODS The size and morphology of model and real UHMWPE particles were determined with the use of light microscopy and scanning electron microscopy. By determining the morphological descriptors, the surfaces of individual particles for different distributions of polyethylene particles were calculated. When measuring the model wear particles, 6 model situations were simulated, in which comparisons with the control measurement by the BET (Brunauer-Emmet-Teller) method were made. RESULTS The variability of individual morphological descriptors demonstrates the effect on the total surface of particles. The calculated coefficient defines how many times the particle surface increases when corrected to the given descriptor (elongation, flattening, roughness, porosity). The total area of real wear particles at 1 year is 4,622 cm2, at 20 years it is 92,440 cm2. Based on our calculations, the area of particles where a biofilm is actually formed (approximately 50 bacteria may adhere to a particle of 3µm in diameter) is 809.5 cm2 at 1 year and 16,190 cm2 at 20 years. DISCUSSION According to the measurements, the size of the potential adhesion area of metal parts and polyethylene particles becomes equal already after several weeks of endoprosthesis usage and after a few years it is many times larger. The question is whether the risk of bacterial adhesion, i.e. also the risk of infectious complications of TEP actually increases. The clinical practice suggests that the number of infections e.g. 10, 15 or 20 years after the primary implantation is not statistically higher, despite the confirmed growth of potential adhesion area in the form of UHMWPE particles. This fact could be explained by a partially equal regulatory pathway of infection and polyethylene disease. The immune system stimulated by wear particles might better resist the hematogenic infection. CONCLUSIONS The study outcomes clearly indicate that the area of polyethylene wear particles considerably increases over time. In spite of the fact that only approximately 10% of wear particles show parameters (also with respect to the size of particles and bacteria) for potential bacterial adhesion, this area is many times larger than the area of metal parts of the endoprosthesis. Key words: UHMWPE particle, adhesion, biofilm, wear, TJR infection.

[Comparison of Explanted UHMWPE Hip Replacement Components of Various Manufacturers after 10 Years in vivo]

PURPOSE OF THE STUDY Considered to be one of the most common causes of aseptic loosening of endoprostheses is the THA failure due to the wear of articulating components, UHMWPE in particular. The purpose of this study is to verify, in terms of oxidative damage and other parameters, the differences between the UHMWPE implants made by various manufacturers explanted for aseptic loosening with the same life span in vivo. MATERIAL AND METHODS In the period 2010-2015, a total of 21 THA articulating components (cups) made of Ultrahigh molecular weight polyethylene by seven different manufacturers were explanted. For each manufacturer, three UHMWPE cups with the same life span (10-12 years after the primary implantation) were evaluated. The damage to the examined joint replacements was described in complexity using three different criteria, namely independently by three evaluators - experienced orthopaedic surgeons. The evaluated criteria were the following: degree of osteolysis determined based on the preoperative radiographs, wear rate of the explanted UHMWPE component, and extent of perioperatively detected granuloma. Oxidative damage and other structural characteristics of explanted cups were studied by means of infrared spectroscopy and microhardness testing. The correlation between the clinical orthopaedic assessment and oxidative damage were statistically processed. RESULTS Strong correlations between the oxidative damage and crystallinity, strong correlations between all types of orthopaedic assessments, negligible correlations between trans-vinylene index and all the other quantities, and moderate correlations between the oxidative damage and clinical evaluation were identified. It was confirmed by experimental measurement that the observed high oxidative damage, resulting in increased crystallinity, manifested itself also in micromechanical properties of the material at the respective site of the THA articulating component. DISCUSSION The discussion includes the comparison of correlations of individual quantities as well as potential effects on the differences in values of components made by individual manufacturers. The values are related to the data in literature and generally accepted claims. CONCLUSIONS At the time of failure almost all the components showed severe or even critical oxidative damage that strongly correlated with the overall clinical evaluation of the damage to the implant. This confirmed that the oxidative degradation is one of the main causes of THA failure. Key words: UHMWPE, oxidation index, crystallinity, THA failure, wear.

[Long-Term Results of the Ludloff Procedure in Relation to the Intraoperative Finding on Acetabular Labrum]

PURPOSE OF THE STUDY Developmental dysplasia of the hip still remains one of the most discussed topics in paediatric orthopaedics. The comprehensive care of paediatric patients with congenital developmental dysplasia of the hip at our department in the period from 1970 to 1985 included, among other things, the open reduction using Ludloff s approach in hip joints where closed reduction was not possible. This technique was supported by some of our own previous observations, such as the original classification of intraoperative findings on acetabular labrum (limbus). This study aims to evaluate the long-term results of treatment of our patients where Ludloff s open reduction was used and seeks to establish a conclusive correlation between the final result and the method of treatment of individual types of limbus, possibly confirming or ruling out that the dependence of later development of the acetabulum is dependent on correct and sparing treatment of this barrier to reduction. MATERIAL AND METHODS In the period from 1970 to 1985, the Ludloff s open reduction was performed in 70 patients. In 8 cases bilateral surgery was carried out. A total of 78 hip joints were operated on. The patients underwent the surgery at the age of 5-23 months. Postoperatively, the Hanausek biomechanical apparatus was applied to complete the treatment. In total, documentation of 21 surgeries performed in 20 patients was successfully tracked down. Two patients were removed from the group for incomplete documentation. The final group of patients included a total of 18 patients, of whom there were 13 women and 5 men. In one female patient the surgery was performed bilaterally. The shape of the femoral head, the center-edge (CE) angle and the degree of osteoarthritic changes were assessed on the pelvic radiograph of each patient. The functional result was evaluated using the Harris Hip Score (HHS). RESULTS For the purpose of assessment, the patients were divided into sub-groups based on the intraoperative finding on acetabular labrum. Type I limbus was found in a total of 5 cases. The mean HHS was 93, the mean CE angle was 22.5°. Aseptic necrosis occurred in one patient. Type II limbus was found in a total of 3 patients. The mean HHS was 84, the mean CE angle was 22°. Aseptic necrosis was observed in one patient. Type III limbus was found in 8 patients. The mean HHS was 79, the mean CE angle was 19.4°. Osteoarthritic changes of degree II-III were identified. Necrosis of the femoral head was recorded in 2 patients. Type IV limbus was found three times. The mean HHS was 73, the mean CE angle was 13.3°. Osteoarthritic changes of type III were present. Necrosis of the femoral head was recorded altogether in 2 patients. DISCUSSION The results of the Ludloff procedure reported in the available literature differ markedly as to the resulting function of the hip joint and the incidence of avascular necrosis. No author gave a description of the actual acetabular labrum deformity or showed a detailed description of individual vessel ligations. The advantage of this method is beyond any doubt its low invasiveness and when correctly performed also the minimal burden to the child. Its disadvantage is a certain degree of difficulty in performing this surgery, a worse visualisation of all barriers to reduction and a more challenging treatment of the posterior portion of the hip joint compared to techniques using the anterior approach. CONCLUSIONS Our outcomes indicate that the resulting Harris Hip Score was best in patients with the intraoperative finding of type I limbus. All the other types (II-IV) showed worse HHS results. From the current perspective, it is in all likelihood more advantageous to use surgical approaches that enable better visualisation of the anatomical deformities and allow for better options for their treatment. Key words: congenital hip dislocation, surgical treatment, open reduction, Ludloff procedure, acetabular labrum.

[Longterm Results of Non-Anatomical Reconstruction of Proximal Humerus]

PURPOSE OF THE STUDY Treatment of comminuted three- and four-part displaced proximal humerus fractures continues to be discussed in daily trauma practice. In fractures with metaphyseal comminuted fractures the anatomical reconstruction is often technically unfeasible. For cases of comminuted metaphyseal proximal humerus fractures we proposed the so called non-anatomical reconstruction with simple osteosynthesis. Even today, when nailing and plating are commonly used in osteosynthesis, the non-anatomical reconstruction plays an irreplaceable role. Its application is conditioned by at least partially preserved vascular blood supply of the head fragment. This paper describes our original technique to manage these fractures and provides an evaluation of results of the group of patients in whom this procedure was performed. MATERIAL AND METHODS Our group included a total of 72 patients (who underwent surgery in the period from 1 January 1989 to 22 March 2016), of whom 57 were clinically assessed (8 patients died, 7 patients failed to be traced back). The mean age at the time of procedure was 53.61 years (range 19-81 years). The mean follow-up was 14.3 years (range 0.3-26.3 years) after the surgery. The method consists in removing the comminution zone, impacted modified diaphyseal fragment to head spongiosis and osteosynthesis of greater and lesser tubercle or their remainders to diaphyseal fragment using tensile cerclage. RESULTS The mean post-operative Constant score was 81.4 (range 30-100 points). The mean abduction was 120.4 degrees (range 60-165 degrees) and ventral flexion was 129.2 degrees (range 70-170 degrees). Excellent clinical outcome according to the Constant score was achieved in 19 patients, good outcome in 23 patients, fair in 8 patients and poor in 7 patients. DISCUSSION We have been using our original method for 27 years. Compared to osteosynthesis by locking plates, minimally invasive procedures and trauma shoulder joint replacement, our method helps achieve very good clinical outcomes. Its main advantage, however, is the fact that by this technique the specific type of fractures can be treated, otherwise manageable exclusively by arthroplasty. CONCLUSIONS At our clinic, the non-anatomical reconstruction belongs to irreplaceable methods for treating certain proximal humerus fractures. The clinical outcomes of this method can be described as very good. The method of non-anatomical reconstruction eliminates the disadvantages and risks of arthroplasty. Nonetheless, it shall be stressed that this method can be successful exclusively when applied to precisely indicated types of fractures and when performed with technical precision. Its another advantage are the minimal financial requirements. Key words: non-anatomical reconstruction, osteosynthesis, proximal humerus, cerclage.

[Analysis of Oxidative Damage to Components Removed from Beznoska/Poldi Total Hip Replacements]

PURPOSE OF THE STUDY Ultrahigh molecular weight polyethylene (UHMWPE) is today the most frequently used bearing surface in total joint replacements (TJR) because of its properties, i.e., excellent biocompatibility, good mechanical and tribological performance and high wear resistance. UHMWPE liners are the most loaded TJR components and, therefore, their properties are decisive for TJR longevity. This study had three objectives: 1) to evaluate the oxidative degradation of explanted UHMWPE components; 2) to look for a statistically significant relationship between the extent of oxidative degradation and the durability of joint replacements; and 3) to investigate whether the durability of a TJR was related to the type of sterilisation used in manufacture. MATERIAL AND METHODS The study included 26 acetabular components obtained at revision arthroplasty between 2004 and 2013 from patients in whom a Beznoska/Poldi total hip replacement was used in the period from 1977 to 2002. The average age of the patients at the time of primary implantation was 57.9 years, the average longevity of the components removed was 18.63 years (range, 6.9 to 27.9 years). Samples of worn out and unworn areas from explanted components were processed in a three-step procedure in order to finally obtain 2-mm microtome sections. These were studied by infrared microspectroscopy. Oxidative damage to UHMWPE was determined as the oxidation index (OI); radiation damage to UHMWPE during sterilization was evaluated as the transvinylene index (VI); oxidation-induced changes in the polymer structure and its properties were characterised as the crystallinity index (CI); and local changes in mechanical properties due to oxidative degradation were assessed as microhardness (MH). Spearman's correlation coefficient and the Wilcoxon two-sample test were used for statistical analysis. RESULTS The OI values (average and maximum) in both worn out and unworn surface areas were related to component longevity. The difference between the oxidation index of ruptured components and that of the other components was statistically significant. Significant differences were also found between the average and maximum OI values of worn out areas and those of unworn surfaces. The relationship between the average oxidation index in both the unworn and worn out areas of UHMWPE components and the longevity of cracked components was statistically significant. DISCUSSION Our results show that the OI values obtained by microspectroscopy correlated with both the microscopic damage and the longevity of UHMWPE liners and the correlation was statistically significant also in relation to the longevity of total replacements. Relationships amongst OI, VI, CI and MH values as well as their relation to failure and longevity of total replacements are discussed. CONCLUSIONS It can be concluded that infrared microspectroscopic measurement of OI values is a simple and fast method to characterise UHMWPE liners. In addition, the IR spectra also show other supplementary characteristics, such as VI and CI indices. These values provide information on the quality of various UHMWPE types currently used in TJR surgery. The types of UHMWPE which exhibit high oxidative degradation should be avoided in clinical practice due to increased risk of early TJR failure. Responsible orthopedic surgeons should be aware of this fact and, if possible, collaborate with an independent, noncommercial laboratory in order to evaluate the quality of various UHMWPE liners used in their hospitals.

KEY WORDS

UHMWPE, oxidation, total joint replacement, infrared spectroscopy, microhardness.

PCR diagnostic system in the treatment of prosthetic joint infections

In our prospective study, we examined whether a multiplex PCR diagnostic method is suitable for the primary detection of pathogens. We also examined the possibility and sensitivity of detecting genes responsible for biofilm production and methicillin resistance. From 2007 to 2009, 94 patients were included in the study. A UNB (universal detection of 16S ribosomal bacterial DNA) and UNF (universal detection of pathogenic fungi) were used in the primary detection. A multiplex assay for biofilm production, methicillin resistance allowed us to distinguish between Gram positivity and negativity and to detect Staphylococci. From all the samples, the culture was positive in 53.2 % of cases, and by using the UNB method, we detected bacteria in 79.8 % of cases-the UNF detection of fungi was positive in 10.6 % of cases. In 75 % of positive findings, we detected a Gram-negative bacterium in 65.3 % of cases. In 47.2 % of Staphylococci detected, the ability to produce biofilm was confirmed. 61.1 % of the Staphylococci exhibited a methicillin resistance. Our multiplex scheme cannot yet fully replace microbial cultivation but can be a rational guide when choosing an appropriate antibiotic therapy in cases where the microbial culture is negative.

[Effect of sterilisation with formaldehyde, gamma irradiation and ethylene oxide on the properties of polyethylene joint replacement components]

PURPOSE OF THE STUDY

Each method of sterilisation has some effect on the structure and properties of UHMWPE and thus also on joint replacement longevity. This study was designed to compare, using objective methods of measurement, several kinds of sterilisation and to recommend the one which has the best prospect for making joint replacements last longer.

MATERIAL AND METHODS

Two groups of UHMWPE samples were tested. Group 1 included virgin GUR 1020 polyethylene, non-modified and non-sterilised (Meditech, Germany). Group 2 comprised of three sets of samples sterilised with formaldehyde, gamma irradiation and ethylene oxide, respectively. In both groups, physicochemical properties were assessed by infrared spectroscopy (IR), and the oxidation (OI) and trans-vinyl (VI) indices, which show the degree of oxidation of a material, were determined. Free-radical concentrations were measured by the method of electron spin resonance (ESR). The mechanical properties of each sample were studied using small punch tests (SPT) and testing microhardness (MH). Any change in mechanical properties can affect, to various degrees, the quality and longevity of a prosthetic joint.

RESULTS

The samples sterilised by gamma irradiation showed higher values of both the OI (0.37) and the VI index (0.038) than the other samples (OI, 0.02 to 0.05 and VI, 0). Also, the free-radical concentration was detectable only in the gamma-sterilised sample. Values obtained for mechanical properties were as follows: peak load in the range of 58.48 N (gamma irradiation) to 59.60 N (ethylene oxide); ultimate load in the range of 46.69 N (gamma irradiation) to 57.50 N (ethylene oxide); ultimate displacement in the range of 4.29 mm (gamma irradiation) to 4.58 mm (virgin polyethylene and formaldehyde); and work to failure in the range of 185.18 mJ (gamma irradiation) to 205.89 mJ (virgin polyethylene). Microhardness values were obtained in the following ranges: 41.2 to 44.6 MPa (virgin polyethylene); 40.2 to 44.1 MPa (formaldehyde); 46.1 to 49.3 MPa (gamma irradiation); and 40.3 to 44.2 MPa (ethylene oxide).

DISCUSSION

The samples sterilised with formaldehyde and ethylene oxide have mechanical properties very similar to virgin polyethylene, they are not damaged by oxidation and do not contain free radicals. Owing to these characteristics, the immediate and long-term oxidation stability of the three samples is higher. The sample sterilised by gamma irradiation showed the presence of free radicals and immediate and long-term oxidative degradation. This results in the deterioration of mechanical properties and the growth of crystallinity due to enhanced oxidation and leads to higher polyethylene microhardness.

CONCLUSIONS

Sterilisation with gamma irradiation results in oxidative degradation and mechanical property deterioration, which is one of the potential risks of a shorter life span of joint replacements. The use of ethylene oxide or formaldehyde does not change polymer properties nor has any effect on oxidation of materials. Therefore, a longer life expectancy of the joint replacements sterilised with ethylene oxide can be expected. The life span of their joint replacements is a key issue for the patients. Prosthetic joint loosening is painful and the patient often requires re-implantation. A higher number of re-implantations is associated with higher costs for the institution involved and, consequently, for the whole health care system. Although this study basically deals with chemical issues, it informs the surgeon of the latest developments leading to the improvement of implanted materials, which can increase the life expectancy of joint replacements and patients' satisfaction.

[Current knowledge on the effect of technology and sterilization on the structure, properties and longevity of UHMWPE in total joint replacement]

Ultrahigh molecular weight polyethylene (UHMWPE) is the most frequently used bearing surface in currently used total joint replacements (TJR). According to the literature available, UHMWPE is the best polymer material, in terms of biocompatibility, mechanical properties and wear resistance, for this application. In spite of this fact, UHMWPE wear (i.e., release of microscopic particles from the polymer surface) remains one of the main reasons of TJR failures. Consequently, the wear of UHMWPE is a subject of intensive study by both materials scientists and orthopaedic surgeons. The structure and properties of UHMWPE strongly depend on the way of processing and post-processing modifications. The processing includes polymer resin preparation (microparticles about 100 ěm in size) and resin consolidation (forming bulk material). Post-processing modifications aim at increasing wear resistance and oxidation stability which are regarded as major factors involved in TJR failure. In order to maintain high purity materials for medical application, it is not allowed to use additional chemicals during the modification processes. The only exception is the use of vitamin E, a natural stabilizer and antioxidant. Considering all the above mentioned facts, the modifications can be based on (I) ionizing radiation such as gamma rays or accelerated electrons, (II) thermal modification, (III) additional stabilization with vitamin E, and (IV) sterilization. According to the modifications, we usually differentiate three generations of UHMWPE. The 1st generation UHMWPE is not modified except for obligatory sterilization. The sterilization procedures based on chemical procedures (formaldehyde vapours, hot water) have lately been forbidden, abandoned and replaced by gamma-irradiation with doses of 25-45 kGy. In the course of time, sterilization by means of gamma-irradiation showed to be unsuitable due to oxidative degradation of UHMWPE, which resulted in lower wear resistance, worse material properties and a decrease in longevity of joint replacements. The 2nd generation UHMWPE or highly cross-linked UHMWPE is material treated with ionizing radiation (gamma-rays or accelerated electrons) at higher doses (usually 50-100 kGy). The irradiation is followed by thermal treatment in order to eliminate residual radicals and limit oxidative degradation that occurs in the 1st generation UHMWPE types. Finally, the material is sterilized usually by modern procedures using ethylene oxide or gas plasma neither of which causes oxidative degradation (as opposed to gamma-irradiation sterilization). The 3rd generation UHMWPE is basically the same as that of the 2nd generation. The main difference consists in slightly better mechanical properties (strength, fatigue) and further stabilization to oxidative degradation. This is achieved by special procedures, some of which are either controversial (sequential irradiation) or well-accepted by a great majority of the orthopaedic community (vitamin E stabilization). Only the future will show whether the difference between the 2nd and 3rd generations of UHMWPE will play any role in increasing TJR longevity and therefore the quality of its performance. The final objective of all of UHMWPE modifications is, as already mentioned, to increase wear resistance, oxidative resistance and mechanical performance of the polymer. These changes, especially an increase in wear resistance, have been confirmed to prolong the longevity of total joint replacements based on UHMWPE.

[MORF method for assessment of the size and shape of UHMWPE wear microparticles and nanoparticles in periprosthetic tissues]

PURPOSE OF STUDY

Aseptic loosening of total joint replacement (TJR) due to wear of ultra-high molecular weight polyethylene (UHMWPE) is regarded as one of the major problems in the field of arthroplasty. This work describes a newly developed method, called MORF, which completely describes the morphology of UHMWPE wear particles. The differences in wear particle morphology may help to elucidate individual differences in TJR failures.

MATERIAL AND METHODS

During the years 2002-2010, a set of 47 typical damaged periprosthetic tissues, coming from 16 TJR revisions, was collected. Isolated on polycarbonate (PC) filters were quantified. Quantification of the particles consisted in determination of their concentration and description of their morphology by means of the newly developed MORF method. Firstly, the micrographs of isolated UHMWPE particles were obtained with a scanning electron microscope (Quanta 200 FEG; FEI) at two magnifications: x1200 and x6000. Secondly, both high- and low-magnification micrographs were processed by a standard image analysis software (program NIS Elements; Laboratory Imaging) in order to obtain basic morphological descriptors. Finally, the results from image analysis of high- and low- magnification micrographs were combined by means of our own program MDISTR in order to obtain correct particle sizes and shapes.

RESULTS

In the first stage, the method was applied to 25 samples and yielded an average particle size of 0.51 µm. In the second stage, the method was further improved in order to calculate not only the size of particles but also the shape of descriptors. The improved method was applied to eight samples and gave an average size of particles (equivalent diameter, D) in the range of 0.27 - 0.60 µm, circularity (C) of 0.66-0.85 and elongation (E) of 1.75-1.79, suggesting that the great majority of particles were approximately spherical. Finally, in the third stage, the MORF method was applied to two exceptional samples which contained extremely small wear particles (D = 18.5 nm and 21.2 nm). The shape of these small wear nano- particles (C = 0.97 and 0.93; E = 1.29 and 1.35) was even more spherical than that of wear microparticles described abo- ve. This was one of the first two studies which proved the presence of UHMWPE wear nanoparticles in vivo.

DISCUSSION

Our newly developed MORF method described in this contribution yields both size and shape descriptors of UHMWPE wear particles, with sizes from 0.1 to 10 µm, which are regarded as most biologically active. The main objective of the method is to yield the highest accuracy. This is achieved by parallel analyses of high- and low-magnification micrographs taken of the same sample. In the end, the two analyses are combined together in order to obtain the correct and complete size and shape description of all particles in the sample. The morphology of UHMWPE wear particles influences TJR lifetime both directly (size and shape of the particles is related to their biological activity) and indirectly (for the given total volumetric wear, size and shape of the particles influence their concentration, which is associated with the biological respon- se of the organism).

CONCLUSION

The authors have developed a new method which yields a complete description of the size and shape of UHMWPE wear particles in periprosthetic tissues. The method, which was called MORF, can be applied to studies of TJR failures and also used to evaluate the quality of different UHMWPE components of TJR. The method is quite universal and therefore can be used not only for analyses of wear particles, but also for other types of particles, such as microparticles in polymer blends or inorganic/metallic nanoparticles.

[Long-term results of the SVL total knee arthroplasty]

PURPOSE OF THE STUDY

The aim of the study was to evaluate the long-term results of the total knee replacement Beznoska SVL implanted at the 1st Department of Orthopaedic Surgery, 1st Faculty of Medicine, Charles University and Motol University Hospital Prague, in the 1997/2009 period.

MATERIAL AND METHODS

The SVL implant is a non-constrained knee replacement, anatomically similar to the bone it replaces, which preserves the posterior cruciate ligament. A total of 1101 knee joint replacements were evaluated in 973 patients, of whom 128 underwent bilateral arthroplasty. Kaplan-Meier curves were used to estimate the cumulative survival of implants. Clinical outcomes were assessed using the Knee Society clinical rating system (KS score) and radiographic data evaluation was also included.

RESULTS

Using KS scores, the results were excellent in 997, good in 75, satisfactory in 19 and poor in 10 knees. The average range of motion was 0.16 to 106.31 degrees. The complications included flexion contracture, as the most frequent problem (13 knees), 10 knees were infected, aseptic loosening due to polyethylene granuloma was found in eight knees and anterior knee pain was experienced in six cases. At follow-up of 12.5 years implant survivorship was 98 %, as evaluated by the Kaplan-Meier analysis.

DISCUSSION

A comparison of SVL implant survivorship with other knee replacement designs is discussed. It should be emphasized that the clinical outcome depends not only on implant quality, but also on the operative technique used and the surgeon's experience and skills. It is the SVL system that allows for the balancing of knee joint stability and thus enables even less experienced surgeons to make use of a more sophisticated implantation technique.

CONCLUSIONS

Total knee replacement using the SVL Beznoska implant is a safe, reliable and economic treatment with excellent clinical outcomes.

[Anatomical study of flexor hallucis brevis insertion: Implications for clinical practice]

PURPOSE OF THE STUDY

The flexor hallucis brevis (FHB) is one of the short muscles of the foot. It divides in front into two portions, which are inserted into the medial and lateral sides of the base of the first phalanx of the great toe. The detailed knowledge of its insertion into the proximal phalangeal base is decisive in any surgery involving the first metatarsophalangeal (MTP) joint, such as implant arthroplasty, resection arthroplasty or amputation. Complications resulting from injury to this insertion are commonly known. The aim of this study was to describe in detail the morphology of FHB insertion sites and to determine a safe extent of resection to be done at the base of the proximal phalanx.

MATERIAL AND METHODS

In 36 cadaver specimens we measured FHB insertion length from the plantar side of the proximal phalangeal base and from the plane perpendicular to the long axis of the phalanx and passing through the base of the concave articular surface of the phalanx.

RESULTS

Measured from the plantar base of the proximal phalanx, the mean length of the medial insertion site was 11.5 ± 0.9 mm (range, 9.5 to 13.0 mm) and that of the lateral insertion site was 9.5 ± 1.1 mm (range, 8.0 to 11.5 mm). After resection, the mean values for medial and lateral FBH insertion sites were 8.5 ± 1.7 mm (range, 6.5 to 11.0 mm) and 7.1 ± 1.4 mm (ran- ge, 5.5 to 9.5 mm), respectively. The mean total proximal phalangeal length was 33.1 ± 2.2 mm (range, 28.5 to 37.0 mm), reduced after resection to 30.5 ± 2.1 mm (range, 26.0 to 34.5 mm).

DISCUSSION

Our results show that the medial insertion site, where the medial FHB tendon and distal part of the abductor hallucis muscle are joining, is longer than the lateral site. Therefore the length of the lateral site is decisive for preserving FHB function. Since the plane perpendicular to the long axis of the phalanx and passing through the base of the concave articular surface of the phalanx is almost identical with the beginnings of FHB insertions, it seems optimal for clinical practice to perform the initial resection along this plane.

CONCLUSIONS

To preserve at least one third of the FHB insertion, the final resection should not exceed 4 mm or 13 % of the proximal phalangeal length, as measured from the reference plane defined above.

[Distribution of UHMWPE wear particles in periprosthetic tissues of total hip replacements]

INTRODUCTION

Information on the distribution of UHMWPE wear particles around joint replacements is essential for the understanding of aseptic loosening of implants.

MATERIAL AND METHODS

Samples of soft tissue from around total hip arthroplasty (THA), which had a typical appearance of polyethylene granuloma, were collected from the places corresponding to the radiological zones of Gruen and DeLee. The samples were taken from 45 patients (group N1). Since the samples varied in macroscopic appearance and/or the technique of processing, a sub-group of 15 more uniform samples (group N2) were collected by the first author in order to ensure the maxi- mum reliability. The samples were examined for the extent of tissue damage and the amount of particles in each zone. The comprehensive orthopaedic evaluation of tissue damage was carried out as follows: the first author studied the joint replacement revision protocol and pre-operative radiograph in each patient. He evaluated the degree of damage in each zone and wrote down the results in the form of an ordered series according to increasing damage (relational statement). This ordered series was called orthopaedist's statement (OS). The amount of particles in each zone around THA was assessed by the IRc method developed in the laboratory of the second author. IRc method yielded numbers that were proportional to the volume of biologically active particles with size 0.1-10 microm in given zones. The set of numbers from IRc method for each individual case of THA was ordered in a series (relational statement). This ordered series was called a measurement statement (MS) and could be directly compared with orthopaedist's statement (OS). The OS's and MS's for each patient were statistically evaluated, independently for each group (N1=45, N2=15), and two hypotheses were tested: a) distribution of particles in various zones around THA is uniform, b) there is an agreement between OS and MS.

RESULTS

The number of UHMWPE wear particles in different periprosthetic zones within each patient was significantly different in both groups (N1 and N2) at the significance level of P=0.001. The OS's and MS's were identical at the significance level P=0.05. Moreover, maximum amount of particles was found in zones III and 7 in 40 patients out of 45.

DISCUSSION

Polyethylene wear debris is considered one of the major causes of THR failures. However, neither national nor international literature has provided a study that would show a statistically significant relationship between the numbers of wear particles in individual zones and the extent of tissue damage in these zones. This is most probably due to the fact that four independent methods had to be developed in order to compare OS's and MS's: 1) accurate technique of tissue sampling during THA revisions, 2) accurate method of isolating wear particles from the tissues collected, 3) efficient, reliable and reproducible quantification of UHMWPE particles and 4) correct method of statistical analysis for comparison of the orthopaedist's statements and the measurement statements for all patients involved.

CONCLUSION

The distribution of wear particles in the periprosthetic tissues of THA is not uniform, i.e. the amount of wear particles of each patient varies from zone to zone. The extent of tissue damage in each zone, as assessed by the orthopaedic surgeon (OS), was in a good agreement with the volume of 0.1-10 microm particles obtained by IRc measurement (MS) of the zone. We have provided conclusive evidence that the highest number of particles is accumulated in zone III and zone 7. As the number of particles the zones varies and the greatest damage is repeatedly found in areas with the highest particle numbers, it can be concluded with certainly that wear particles are one of the main causes of aseptic joint implant failure.

[Polyetheretherketone (PEEK). Part II: application in clinical practice]

Polyetheretherketone (PEEK) is one of the up-to-date organic polymer thermoplastics with applications in orthopaedics and trauma medicine. This study presents a detailed analysis of its tests and applications in clinical medicine. A wide range of PEEK modifications and composites are commercially available, e.g., PEEK-Classix, PEEK-Optima, Endolign and Motis. They differ in their physical properties, which makes them suitable for different applications. Other forms, so-called PEEK bioactive composites, contain beta-tricalcium phosphate and hydroxyapatite. Research in this field is also concerned with the surface finish of this polymer thermoplastic and involves macroporous titanium and hydroxyapatite layers, or treatment with laser for an exactly defined surface structure. The clinical applications of PEEK and its composites include, in addition to components for spinal surgery, osteosynthesis plates, screws, intramedullary nails or external fixators, which are implants still at the stage of prototypes. In this review, attention is paid to the use of PEEK thermoplastics for joint replacement. Mid-term studies involving hundreds of patients have shown that, for instance, the VerSys Epoch Fullcoat Hip System (Zimmer) has a markedly lower stress-shielding effect. Carbon fibre-reinforced (CFR-PEEK) composites are used to make articulating components for total hip replacement. Their convenient properties allow for production of much thinner liners and an enlargement of the femoral head diameter, thus reducing the wear of joint implants. CFR-PEEK composites are particularly effective for hip resurfacing in which the Mitch PCR (Stryker) acetabular component has been used with good results. The MOTIS polymer acetabular cup (Invibio Ltd.) is another example. Further PEEK applications include the construction of finger-joint prostheses (Mathys AG), suture anchors (Stryker) and various kinds of augmentations (Medin). Based on the information obtained, the authors suggest further use for CFR-PEEK composites, such as the construction of articulating liners for total shoulder joint replacement, particularly in reverse shoulder arthroplasty.

[Polyetheretherketone (PEEK). Part I: prospects for use in orthopaedics and traumatology]

On the basis of current studies, polyaryletherketone (PAEK) polymers appear to be materials with great prospects for medical application. The most important member of this family of semi-crystalline thermoplastics is polyetheretherketone (PEEK) with its composites. The excellent properties of this material find their use in the treatment of various disorders of the skeletal system. At present they are used with advantage to construct spinal implants, and replacements for other orthopaedic applications and for dental and trauma medicine are at advanced stages of clinical testing.