Understanding frictional behavior in fascia tissues through tribological modeling and material substitution.

The objective of this study is to develop a reliable tribological model to enable a more thorough investigation of the frictional behavior of fascia tissues connected to non-specific lower back pain. Several models were designed and evaluated based on their coefficient of friction, using a low-frequency, low-load reciprocating motion. The study found that two technical elastomers, layered on PDMS to simulate the fascia and underlying muscle, are suitable substitutes for biological tissue in the model. The influence of tribopair geometry was also examined, and the results showed that greater conformity of contact leads to a lower COF, regardless of the material combination used. Finally, the friction properties of HA of various molecular weights and concentrations were tested.

On the observation of lubrication mechanisms within hip joint replacements. Part II: Hard-on-hard bearing pairs.

The present paper represents Part II of the extensive study focused on the lubrication of hip joint replacements. The main goal is to assess the fundamentals of lubrication considering both hard-on-soft (Part I) and hard-on-hard (Part II) bearing pairs. In addition, the effect of individual constituents contained in the model fluid is clarified. For this purpose, multiple model fluids of various composition were employed. In this part of the study, metal-on-glass contact representing hard bearing pairs was observed in situ using pendulum hip joint simulator in combination with thin film colorimetric interferometry method. The designed test consists of initial static loading/unloading phase for the determination of adsorption of molecules on rubbing surfaces. This period is followed by swinging of the pendulum and latest static part under constant load. Three groups of measurements were carried out while fourteen different lubricants were tested. Initially, the experiments were performed with albumin-based model fluid. In that case a substantial positive effect of hyaluronic acid was identified. In contrast, the fluids with γ-globulin as a base constituent showed improved lubrication conditions when phospholipids were added to the solution. Finally, considering the complex fluid, a combined effect of hyaluronic acid and phospholipids caused a better endurance of the lubricant film. The latest part of the paper aims on the comparison of film formation considering hard and soft pairs, highlighting some clear differences. In general, hard pairs exhibit clear decreasing tendency of the film during swinging motion while opposite behaviour was observed for soft pairs.

On the observation of lubrication mechanisms within hip joint replacements. Part I: Hard-on-soft bearing pairs.

The present study describes the lubrication mechanisms within artificial hip joints considering real conformity of rubbing surfaces. Part I is focused on hard-on-soft material combination, introducing the fundamentals of lubrication performance. These pairs have not been explored in terms of in situ observation before. The contact of metal femoral component articulating with transparent polymer acetabular cup was studied using a hip joint simulator. The film formation was evaluated by fluorescent microscopy method. Various model synovial fluids were employed while the key constituents, i.e. albumin, γ-globulin, and hyaluronic acid were fluorescently stained to determine its role in film formation process. Two types of the tests were performed. The first dynamic test aimed on the development of film thickness under constant load during motor driven swinging motion mimicking flexion-extension. Subsequently, a combined test was designed consisting of the three phases; static part with loading/unloading phase (1), pendulum swinging till spontaneous damping of the motion due to friction (2), and static observation under the constant load (3). The results clearly confirmed that the interaction of constituents of synovial fluid plays a dominant role and substantially influences the lubrication conditions. In particular, the main finding coming from the present study is that γ-globulin together with hyaluronic acid form relatively thin stable boundary layer enabling the enhanced adsorption of albumin, thus increasing the lubricant film. Part II of the present study is focused on hard-on-hard pairs while the main differences in film formation process are highlighted among others.

In situ observation of lubricant film formation in THR considering real conformity: The effect of diameter, clearance and material.

The aim of the present study is to provide an analysis of protein film formation in hip joint replacements considering real conformity based on in situ observation of the contact zone. The main attention is focused on the effect of implant nominal diameter, diametric clearance and material. For this purpose, a pendulum hip joint simulator equipped with electromagnetic motors enabling to apply continuous swinging flexion-extension motion was employed. The experimental configuration consists of femoral component (CoCrMo, BIOLOX®forte, BIOLOX®delta) and acetabular cup from optical glass fabricated according to the dimensions of real cups. Two nominal diameters were studied, 28 and 36mm, respectively, while different diametric clearances were considered. Initially, a static test focused on the protein adsorption onto rubbing surfaces was performed with 36mm implants. It was found that the development of adsorbed layer is much more stable in the case of metal head, indicating that the adsorption forces are stronger compared to ceramic. A consequential swinging test revealed that the fundamental parameter influencing the protein film formation is diametric clearance. Independently of implant diameter, film was much thicker when a smaller clearance was considered. An increase of implant size from 28mm to 36mm did not cause a substantial difference in film formation; however, the total film thickness was higher for smaller implant. In terms of material, metal heads formed a thicker film, while this fact can be, among others, also attributed to clearance, which is more than two times higher in the case of ceramic implant.

Lubrication within hip replacements - Implication for ceramic-on-hard bearing couples.

The objective of the present study is to clarify the lubrication processes within artificial joints considering the ceramic femoral heads focusing on the role of particular proteins. Two optical methods were employed; colorimetric interferometry and fluorescent microscopy. The experiments were conducted in ball-on-disc configuration, where the ball is made from ceramic (Sulox(TM), BIOLOX(®)delta) and the disc from optical glass. The measurements were realized under pure rolling, partial negative and partial positive sliding, to get a complex information about the protein film behaviour under various conditions. Moreover, two different speeds were investigated; 5.7 and 22 mm/s, respectively. The contact was lubricated by saline solutions containing albumin and γ-globulin in a ratio 2:1, while the total protein concentration was 10.5 mg/ml. Under pure rolling conditions, the film thickness gradually increases with time/rolling distance independently of material and rolling speed, while the dominant fluid constituent is albumin. In the case of negative sliding, the film formation is time/distance/speed dependent. At lower speed, both proteins contribute to film thickness; at higher speed, the effect of γ-globulin is not substantial. When the disc is faster, the character of film formation is similar to the metal component in the case of Sulox ceramic. Biolox ceramic shows a different behaviour, while for both materials, the contribution of γ-globulin increases with increasing speed. As most of the results can be well explained in terms of specific proteins, it can be concluded that the experimental approach is suitable for the investigation of protein film formation considering the ceramic materials.

[Determination of a Friction Coefficient for THA Bearing Couples]. / Stanovení soucinitele trení hlavic a jamek TEP kycle.

PURPOSE OF THE STUDY: The wear of articular surfaces is considered one of the most important factors limiting the life of total hip arthroplasty (THA). It is assumed that the particles released from the surface of a softer material induce a complex inflammatory response, which will eventually result in osteolysis and aseptic loosening. Implant wear is related to a friction coefficient which depends on combination of the materials used, roughness of the articulating surfaces, internal clearance, and dimensions of the prosthesis. MATERIAL AND METHODS: The selected parameters of the bearing couples tested were studied using an experimental device based on the principle of a pendulum. Bovine serum was used as a lubricant and the load corresponded to a human body mass of 75 kg. The friction coefficient was derived from a curve of slowdown of pendulum oscillations. Roughness was measured with a device working on the principle of interferometry. Clearance was assessed by measuring diameters of the acetabular and femoral heads with a 3D optical scanner. The specimens tested included unused metal-on-highly cross-linked polyethylene, ceramic-on-highly cross-linked polyethylene and ceramic-on-ceramic bearing couples with the diameters of 28 mm and 36 mm. For each measured parameter, an arithmetic mean was calculated from 10 measurements. RESULTS: 1) The roughness of polyethylene surfaces was higher by about one order of magnitude than the roughness of metal and ceramic components. The Protasul metal head had the least rough surface (0.003 µm). 2) The ceramic-on-ceramic couples had the lowest clearance. Bearing couples with polyethylene acetabular liners had markedly higher clearances ranging from 150 µm to 545 µm. A clearance increased with large femoral heads (up to 4-fold in one of the couple tested). 3) The friction coefficient was related to the combination of materials; it was lowest in ceramic-on-ceramic surfaces (0.11 to 0.12) and then in ceramic-on-polyethylene implants (0.13 to 0.14). The friction coefficient is supposed to increase with a decreasing femoral head diameter. However, in the bearing couples with polyethylene liners manufactured by one company, paradoxically, the friction coefficient slightly increased with an increase in femoral head size from 28 mm to 36 mm. 4) The lowest friction moment (< 3.5 Nm) was found for ceramic-on-ceramic implants 28 mm in diameter; the highest values were recorded in metal-on-polyethylene bearing couples 36 mm in diameter (> 7 Nm). DISCUSSION: Although our study confirmed that the bearing couples produced by different manufacturers varied to some extent in the parameters studied, in our opinion, this variability was not significant because it was not within an order of magnitude in any of the tests. CONCLUSIONS: The study showed that both the friction coefficient and the friction moment are affected more by the combination of materials than by the diameter of a femoral head. The best results were achieved in ceramic-on-ceramic implants.

[What should an orthopaedic surgeon know about biotribology of total hip arthroplasty]. / Co by mel vedet ortoped o biotribologii totální endoprotézy kycelního kloubu.

The objective of this paper is to briefly review the engineering biotribology of total hip arthroplasty (THA). At present the issue of lubrication, wear and friction within a THA is being studied in detail and the results have been published in a number of papers. The reason is obvious since the rate at which the articulating surfaces wear off affects the longevity of a THA to a great extent. Seeking an optimal biotribological configuration remains an important task for both the researchers and orthopaedic surgeons. In order to enable the orthopaedic community to think over THA biotribology and, at the same time, communicate with the representatives of technical professions, knowledge of the basic principles of biotribology and their understanding is necessary.

[Comparative analysis of pancreatic scintigraphy and results of surgical treatment of patients with pancreatic cancer]. / Sravnitel'nyi analiz pankreatostsintigrafii i rezul'tatov operativnogo lecheniia bol'nykh rakom podzheludochnoi zhelezy.

The results of radiologic investigation in 47 patients admitted to the clinic for pancreatic cancer were compared with the findings of the performed operative intervention. Visualization of the pancreas with 75 Selenomethionine was performed on the gamma-camera FO-GAMMA-IV (USA). A number of differential diagnostic signs of the pancreatic pathology was revealed, dependence between the character and degree of pancreatic changes on a scintigram, and volume of the operative intervention performed was noted. A variant of computerized processing of scintigrams with regard to the activity of the administered radiopharmaceutical preparation is suggested.

[Prognosis of the development and prevention of primary post- operative peptic stricture of the esophagus]. / Prognozirovanie vozniknoveniia i profilaktika pervichnoi posle- operatsionnoi pepticheskoi striktury pishchevoda.

Examined were 58 patients with primary postoperative peptic esophageal stricture (PPPES). The ulcer disease of pyloroduodenal location and impaired function of the esophagus were the leading causes of a stricture. The prognostic algorithm for the PPPES development, which considers the presence of hiatal hernia, severe disorders in gastric evacuation and vomiting, pronounced weakness of a patient, severe complications of the ulcer disease before the operation, has been developed. The prophylactic measures in given pathology are suggested.

[A system for the automatic processing of radionuclide research (the SAORI-01) in clinical practice]. / Sistema avtomatizirovannoi obrabotki radionuklidnykh issledovanii (SAORI-01) v klinicheskoi praktikre.

The author described the results of clinical testing of a system CAOPH-01 designed for automated collection, storage and processing of data on radionuclide investigations. He gave examples of automated processing of RCG and the results of positive scintigraphy of tumors of different sites using 67Ga-citrate and 99mTc-pertechnetate in statistical and dynamic investigations. Short-comings and ways for updating 4 the system during its serial production were pointed out. The introduction of the system into clinical practice on a wide scale was shown to hold promise.

[Dynamics of carcinoembryonic antigen in patients with stomach cancer during treatment with cryotherapy]. / Dinamika rakogoémbrional'nogo antigena (REA) u bol'nykh rakom zheludka pri lechenii s ispol'zovaniem kriovozdeistviia.

Radioimmunologic assays of blood serum carcinoembryonic antigen (CEA) level were conducted at major stages of treatment of gastric cancer by subtotal stomach resection and gastrectomy with preliminary cryotreatment and thawing of tumor. A short-term rise in CEA level occurred in 53.9% of cases 3-4 days after combined therapy. A decrease in CEA concentration at discharge from hospital as compared with preoperative level and that registered 3-4 days after operation was observed in 50 and 75% of cases of combined therapy, respectively, and 47.5 and 37.5% of controls (surgery without cryotreatment). There was no correlation between cryotreatment and changes in CEA level in gastric ulcer patients.