Differences in treatment response between female and male psoriatic arthritis patients during IL-12/23 therapy with or without methotrexate: post hoc analysis of results from the randomised MUST trial.

BACKGROUND: The influence of sex on treatment outcomes during interleukin-12/23 therapy in patients with psoriatic arthritis (PsA) has not been explored. OBJECTIVE: To conduct exploratory post hoc analyses of sex-stratified data from the MUST trial, an investigator-initiated, multicentre, phase 3b study in which patients with active PsA initiating treatment with open-label ustekinumab were randomised to treatment with placebo or methotrexate (MTX). METHODS: We evaluated baseline characteristics, key treatment outcomes and adverse events stratified by sex, with a focus on outcomes that did not include erythrocyte sedimentation rate (ESR) as a component due to the known elevation of ESR in females. RESULTS: A total of 166 patients were treated with ustekinumab+MTX (37 female, 50 male) or ustekinumab+placebo (32 female, 47 male). At baseline, females had a significantly longer time since PsA diagnosis and greater impairment in physical function, but similar joint counts. At week 24, both females and males showed marked improvements to ustekinumab with or without MTX. Females generally had numerically reduced treatment responses compared with males, although differences did not achieve statistical significance. MTX did not show an overall effect on treatment outcomes, but was associated with faster enthesitis responses in males only. Adverse events were generally comparable, but females in the ustekinumab+MTX group had higher levels of gastrointestinal disorders. CONCLUSION: Females and males with PsA had differences in baseline characteristics, treatment responses and adverse events during therapy. A better understanding of sex-based differences in PsA may help optimise treatment.

Comparison of Implant Stability Between Conventional Drilling and Piezosurgical Implant Bed Preparation Techniques.

This prospective study compared the stability of implants placed using piezoelectric surgery (piezo group) and those placed using conventional rotary drills (bur group) during the first 90 days postoperatively. Teeth in the posterior maxillary regions of 21 patients were randomly assigned to 2 groups. The implant stability quotient (ISQ) was measured at days 0, 7, 14, 21, 28, 42, 56, and 90 postoperatively. Twenty-eight of 29 implants were successfully integrated at day 90 (1 implant in the test group was lost). Although both groups showed a significant overall increase in implant stability with time (P < .0001) and a high final mean ISQ value, no statistically significant difference in stability was seen between the groups. The bur group showed greater variance in ISQ values than the piezo group did (P < .001) at all time points. Long-term studies with larger samples are needed to investigate the bone response to the use of piezoelectric surgery for implant preparation.

Development of ASAS quality standards to improve the quality of health and care services for patients with axial spondyloarthritis.

OBJECTIVES: The Assessment of SpondyloArthritis International Society (ASAS) aimed to develop a set of quality standards (QS) to help improve the quality of healthcare provided to adult patients affected by axial spondyloarthritis (axSpA) worldwide. METHODS: An ASAS task force developed a set of QS using a stepwise approach. First, key areas for quality improvement were identified, discussed, rated and agreed on. Thereafter, areas were prioritised and statements for the most important key areas were phrased on consensus. Appropriate quality measures were defined to allow quantification of the QS at the community level. RESULTS: The ASAS task force, consisting of 20 rheumatologists, two physiotherapists and two patients, selected and proposed 34 potential key areas for quality improvement which were then commented by 140 ASAS members and patients. Within that process three new key areas came up, which led to a re-evaluation of all 37 key areas by 120 ASAS members and patients. Five key areas were identified as most important to determine quality of care: referral including rapid access, rheumatology assessment, treatment, education/self-management and comorbidities. Finally, nine QS were agreed on and endorsed by the whole ASAS membership. CONCLUSIONS: ASAS successfully developed the first set of QS to help improving healthcare for adult patients with axSpA. Even though it may currently not be realistic to achieve the QS in all healthcare systems, they provide high-quality of care framework for patients with axSpA that should be aimed for.

Clinical evaluation of laboratory-made and CAD-CAM-fabricated occlusal devices to treat oral parafunction.

STATEMENT OF PROBLEM: The demand for occlusal devices to treat oral parafunction is rising. Conventionally, these occlusal devices are produced in the dental laboratory, which requires impressions and gypsum casts. Computer-aided design and computer-aided manufacturing (CAD-CAM) require fewer production steps and may offer greater comfort. Whether this is an improvement on conventional procedures is unclear. PURPOSE: The purpose of this crossover clinical study was to examine whether a digital workflow is feasible for fabricating occlusal devices to treat oral parafunction and to compare CAD-CAM-fabricated occlusal devices with conventionally produced ones to determine whether the digital method provides better results. MATERIAL AND METHODS: Thirty participants wore digitally fabricated occlusal devices for 3 months and then conventionally produced occlusal devices for another 3 months or vice versa. The main target parameter was the participant's preference for 1 of the device types. RESULTS: Both types had specific advantages and disadvantages, but the differences in participants' preference were not statistically significant. After completing the 2 testing periods, 16 participants preferred the laboratory-made device, whereas 12 participants preferred the digital occlusal device. Two participants dropped out during the study. CONCLUSIONS: Given the absence of statistically significant differences, the digitally fabricated device can be considered a suitable alternative to laboratory-made devices. Laboratory-made occlusal devices are now the gold standard. However, given the savings in terms of cost and treatment time, they may be replaced, particularly if the production process can be improved.

Conical zirconia telescoping into electroformed gold: A retrospective study of prostheses supported by teeth and/or implants.

BACKGROUND: Telescopic prostheses are an evidence-based treatment modality, and conical zirconia crowns and electro-formed gold copings have been used for dentures supported by teeth and/or implants. PURPOSE: We aimed to evaluate the survival rates of zirconia-based tooth/implant restorations. MATERIALS AND METHODS: A total of 126 telescopic overdentures, all retained by conical zirconia crowns and electro-formed gold copings, were retrospectively evaluated and failures analyzed for abutment configurations. Survival rates and modifying factors were evaluated by Kaplan-Meier analysis, log-rank testing, and Cox regression analysis. RESULTS: We evaluated observation periods of up to 11.5 years (mean: 45.25 ± 25.11 months). Five-year prosthesis survival was 96.9 ± 2.2% (95% CI: 92.6-100). Six dentures had been lost, and these failures were significantly associated with specific abutment configurations. CONCLUSIONS: Within the limitations of this retrospective study, the concept of conical zirconia telescoping into electro-formed gold provides a viable alternative to other telescopic designs used for removable dental prostheses. The concept is well suited especially for tooth/implant-supported prosthetic rehabilitation.

Locator® versus ceramic/electroplated double-crown attachments: a prospective study on the intraindividual comparison of implant-supported mandibular prostheses.

OBJECTIVES: Implant-supported overdentures are an established dental treatment mode. The aim of this prospective study was and interindividual comparison of patient satisfaction with restorations retained by a prefabricated and thus inexpensive attachment system (Locator®) or with a technologically complex and thus expensive attachment system (ceramic/electroplated double crowns) with similar retentive performance. MATERIALS AND METHODS: Twelve patients received a Locator and a double-crown prosthesis in a crossover study for test periods of 3 months each. The main target parameter was the patient's final decision in favor of one of the two prosthesis types. RESULTS: After completing both test phases, seven patients opted for the Locator prosthesis and five patients opted for the double-crown prosthesis. CONCLUSION: Given the predominant lack of statistically significant differences, the two types of prostheses can be described as equivalent. A recommendation in favor of the Locator prosthesis can be motivated by its lower cost. CLINICAL RELEVANCE: The results of the study show that the more cost-effective variant was comparable to the more expensive double-crown prosthesis under the conditions prevailing in the study. Depending on the indication, this may influence the decision-making process in daily clinical practice and support the clinician's patient information and consultation efforts.

Satisfaction level in dental-phobic patients with implant-supported rehabilitation performed under general anaesthesia: a prospective study.

BACKGROUND: Phobic patients avoid dental treatment impairing their oral health and making it challenging to offer them prosthetic rehabilitation. This study evaluated patients' experience of implant-supported prosthetic treatment after implantation performed under general anaesthesia due to dental phobia and severe pharyngeal reflexes (SPR). The effect of gender, age and location of implantation on patient satisfaction was tested. METHODS: Two hundred five patients underwent implantation under general anesthesia both in maxilla and mandible, respectively. After a trans-gingival healing period of 6-8 weeks, fixed implant bridges were inserted. Patients completed oral health impact profile questionnaire (OHIP-14). An additional set of six special questions was also developed and considered. Analysis of the OHIP-14 total score was made using logistics regression. Wald chi-square test was used to analyse the effect of age, gender and location of implantation. Effect sizes were estimated as odds-ratios and associated 95% Wald confidence intervals. RESULTS: Eighty two of 205 patients were included after prosthetic treatment. After start, 38 patients were excluded (4 died and 34 couldn't be reached). OHIP-14-analyses were made by 43 patients (30-90 years). 67% of patients were totally satisfied with the whole implant rehabilitation (scoring 0). Mean of total score was 2.5. Only age affected significantly (p = 0.014) patients satisfaction. The obtained data indicate that younger patients (30-64 years) especially women are less satisfied (4.95) than older patients (0.3) for age group (65-90 years).Special questions' data showed that 94.5% were satisfied with their treatment. 77.3% continued regular check-up after treatment and 96.9% would undergo the same treatment again. 95.5% would recommend implants to a friend of colleague. CONCLUSION: Gender and location of implantation have no significant influence on patient satisfaction. Younger patients especially women are less satisfied than older patients. Phobic patients are totally satisfied with implant rehabilitation under general anaesthesia which means that this treatment can be considered as a treatment of choice giving these patients the same opportunity like others to improve their oral health and well-being.

Accuracy of a Template-Guided Implant Surgery System with a CAD/CAM-Based Measurement Method: An In Vitro Study.

PURPOSE: The aim of this in vitro study was to evaluate the accuracy of template-guided implantation planned with implant-planning software (Implant Studio), comparing computer-aided design/computer-assisted manufacture (CAD/CAM)-based measurements with measurements via cone beam computed tomography (CBCT). MATERIALS AND METHODS: Thirty template-guided implantations were planned and performed on acrylic-resin models. The implant positions were detected with an intraoral scanner, evaluated with CAD quality-control software, and compared with the planned positions in the test group. Preliminary deviations were measured via CBCT in the control group of the first 10 samples and compared with the first 10 samples of the test group. RESULTS: When directly compared, measurements obtained using CBCT (control group) showed a trend toward greater deviations. In the CAD/CAM-based evaluation of the 30 samples, the mean ± SD deviation of the insertion axis from the planned implant axis was 2.011 ± 0.855 degrees. The mean deviations of the implant shoulders in the horizontal direction and at the implant apices were 0.725 ± 0.142 mm and 0.990 ± 0.244 mm, respectively. In the vertical direction, the mean deviation was 0.541 ± 0.129 mm. CONCLUSION: CAD/CAM-based measurements are more accurate than CBCT measurements. Therefore, this radiation-free measurement method is a viable diagnostic alternative. Implant planning with planning software and subsequent placement using surgical templates appears to be a reliable and precise therapeutic option in vitro. However, these findings will still have to be supported by in vivo studies.

The influence of geometric design variables on the kinematic performance of a surface-guided total knee replacement.

OBJECTIVE: Tibiofemoral geometries in a total knee replacement (TKR) affect the performance of an implant during activities of daily living. The specially shaped components of a surface-guided TKR aim to control the tibiofemoral motion, such that a normal pattern of motion is achieved, even at high flexion angles. The purpose of this study was to assess the influence of the design parameters on the kinematic behavior of such an implant. A combination of design variables was determined that resulted in the least deviation from the design kinematic target. METHODS: Six major design variables were considered to generate customized surface-guided TKR candidates. The contribution of these variables was evaluated by principal component analysis considering the input design variables and the results of the kinematic performance from a virtual simulation of deep squatting. The tibial internal-external rotation and the anterior-posterior translation of the medial and lateral femoral condyles were recorded for each design candidate. A quantified objective function of the kinematic behavior was used to define the design with a maximum agreement with the target pattern of motion. RESULTS: The location and orientation of the flexion-extension axis and the tibial slope were the most contributing parameters on the modes of variation. On the other hand, the conformity between the lateral guiding arcs had the least contribution. CONCLUSION: Virtual simulation showed that the current TKR reached deep flexion angles under squat load, while the tibia pivoted around the medial center. The tibial rotation was within the expected range of the IE rotation from healthy joints.

Kinematic behavior of a customized surface-guided knee implant during simulated knee-bending.

Different designs of total knee replacements (TKRs) aim to enhance the satisfaction of the patients by providing close to normal kinematics. In the surface-guided TKRs, the guidance of the motion in a normal pattern should be achieved through specially shaped articulating geometries. This study used virtual simulation along with a load-controlled knee wear simulator to evaluate the kinematic performance of a customized surface-guided TKR under weight-bearing conditions of lunging and squatting activities. The outcome pattern of TKR motion almost agreed with the predefined design target. The tibial insert rotated internally through a maximum angle of 10.6° and 19.94° for the experimentally simulated lunging and squatting cycles, respectively. This rotation occurred around a medial center, as indicated by a small amount of posterior translation of the medial condyle (maximum of 2.5mm and 6.4mm for lunging and squatting) versus the posterior translation of the lateral condyle (maximum of 12mm and 24.2mm for lunging and squatting). The contact forces mainly provided the guidance of the motion at the tibiofemoral articulating surfaces.The normalized root mean square error between outcomes of the virtual simulations and tests for the angle of internal-external rotation of the tibial insert was less than 8% for one cycle of lunging and squatting. These measures confirm the validity of the virtual simulation for future evaluations of the customized surface-guided TKRs.

In vivo study for tooth colour determination-visual versus digital.

OBJECTIVES: Tooth colour determination is an essential component in the preservative and prosthetic workflow during production of tooth-coloured restorations. The aim of the study was to compare the clinical suitability of conventional, visual tooth colour determination and digital methods. MATERIALS AND METHODS: Tooth colour of vital, natural central incisors among a total of 107 subjects was determined visually by a dentist (VD) and dental technician (VDT) using VITA Toothguide 3D-MASTER®, digitally by the spectrophotometer VITA Easyshade Advance 4.0 (reference instrument) and Trios®Color intra-oral scanner (test subject). Reliability was examined by repeating the digital measurements of 20 teeth three times. The analysis was based on the recorded 3D-MASTER values and L*a*b/L*C*h parameters. RESULTS: The measuring accuracy was 43.9% with the Trios®Color scanner, 35.5% for VD and 34.6% for VDT. In 25.5% of cases, the scanner's results corresponded with VD and in 33.6% with VDT. The visual methods corresponded with 45.8%. All mean values of the recorded colour differences fell within the clinically acceptable range of ΔE ≤ 6.8. The intra-oral scanner attained repeatability of 78.3% and the VITA Easyshade system of 76.6%. CONCLUSIONS: The Trios®Color intra-oral scanner appears to be a good alternative to the current standard of visual tooth colour determination. The new module attains better results than the visual method and is comparable to the reference instrument. CLINICAL RELEVANCE: Dentistry becomes increasingly digitalized and tooth colour determination devices have generally to be improved. Therefore, the investigation of a new digital device is important for future developments.

Design and virtual evaluation of a customized surface-guided knee implant.

Although total knee arthroplasty is generally a successful operation, many studies have shown that it results in significant alterations in the kinematics of the joint, which cause limitations in performing the activities of daily living. This study aimed to define the design features for a customized surface-guided total knee replacement and to evaluate the kinematic outcomes. Magnetic resonance imaging data of the knee joint are used to generate the design features as they relate to the functionality of the implant. The motion is guided by considering a partial ball and socket configuration on the medial condyle and varying radii of curvature on the lateral articulating surface. A virtual simulation of the behavior of the surface-guided total knee replacement was performed to investigate the motion patterns of this total knee replacement under gait and squatting loading conditions. Results of the virtual simulation show that flexion and extension of the knee make the center of the lateral condyle move more naturally in the posterior and anterior directions, in comparison to the center of the medial condyle. Such guidance is achieved as a result of the novel customized designed contact between the articulating surfaces. The proposed customized surface-guided total knee replacement provides patterns of motion close to the expected more natural target, not only during a gait cycle but also as the knee flexes to higher degrees during squatting. Major design features include location and orientation of the flexion and pivoting axes, the trace of the contact points on the tibia, and the radii of the guiding arcs on the lateral condyle.

Multicenter Clinical Randomized Controlled Trial Evaluation of an Implant System Designed for Enhanced Primary Stability.

PURPOSE: This intention-to-treat (ITT) non-inferiority multicenter study was performed to evaluate implant system design, surgical and prosthetic aspects, and the effect on marginal bone levels of two related implant systems. Implant design alterations consisted of modifications in implant body shape and abutment connections. Drilling procedures and drill design were adapted to the implant design. MATERIALS AND METHODS: Five clinics participated in this study; all had institutional review board approval. Two versions of the implant system were used: test and predicate. One hundred twenty partially dentate subjects with healed sites were randomized to either test or predicate implants. Fifty-nine subjects received 79 test implants and 61 received 87 predicate implants. Bone classification, insertion torque values (ITV), and the surgeon's perception of primary stability were recorded. Definitive restorations with a titanium abutment were made approximately 6 to 8 weeks following implant placement. All restorations were cement retained. Marginal bone levels were evaluated on radiographs at implant placement, at restoration, and at 6 and 12 months postloading. RESULTS: Most subjects received one implant placed in the premolar or molar area (95% of sites). Fifty-three percent of the implants were placed in the maxilla. Median ITV at placement was 31 ± 13 Ncm for the test system and 22 ± 9 Ncm for predicate system, respectively. Time to loading was similar (test, 63.1 ± 24.8; predicate, 62.9 ± 26.9 days). Mean marginal bone loss 12 months after functional loading was 0.07 ± 0.73 mm in the test group and 0.03 ± 0.84 mm in the predicate group, with no statistically significant difference (P = .6895). Five implants were lost (four test, one predicate) from implant placement, all within the first 8 weeks following placement; none were restored. The 1-year postloading cumulative implant survival rate was 94.9% (73 implants at risk) for the test system and 98.9% (84 implants at risk) for the predicate system. CONCLUSION: Treatment with the test implant system, utilizing its bone classification for guidance regarding drilling protocol, resulted in enhanced implant stability. Marginal bone levels were stable 12 months after functional loading.

Clinical experience with the European Ankylosing Spondylitis Infliximab Cohort (EASIC): long-term extension over 7 years with focus on clinical efficacy and safety.

OBJECTIVES: Knowledge on the long-term effects of anti-TNF therapy in patients with ankylosing spondylitis (AS) is still limited. Our objective was to study the long-term efficacy and safety of anti-TNF therapy in AS. METHODS: After having completed the first part of the EASIC trial a total of 71 patients were enrolled into this 96-week extension study. Patients were treated with the same dosages and dosing intervals of infliximab as in the EASIC core study. Efficacy was assessed by using standardised assessment tools such as BASDAI, BASFI, BASMI, patient global assessment, CRP levels and the proportion of patients without any sign of enthesitis or arthritis. Long-term safety was assessed by documenting adverse events (AE), serious adverse events (SAE) and reasons for dropping out. RESULTS: Of the 71 patients included, 64 (90.1%) completed the trial , and 7 discontinued: one was lost to follow-up, 3 withdrew informed consent and in 3 patients therapy was stopped for different reasons: secondary loss of response, recurrent infections and basal cell carcinoma of the skin. The completers showed rather stable low scores of BASDAI (mean 2.4, median 2.52), BASFI (mean 3.1, median 2.76) and BASMI (mean 3.2, median 3) as well as patients global assessment and CRP. The vast majority of patients did not have enthesitis or arthritis. A total of 476 AE were observed, 13 of which were SAE. The majority of these were infections and most of them affected the respiratory tract. Two malignancies occurred: one basal cell carcinoma and one malignant melanoma. These were the only SAE judged to be possibly related to the study drug. CONCLUSIONS: Anti-TNF treatment with infliximab is efficacious over long periods of time in patients with AS. The observation of two skin related malignancies, including one melanoma, during the whole study period of 7 years is in line with reports from previous large AS data sets.

Predictive validity of the ASAS classification criteria for axial and peripheral spondyloarthritis after follow-up in the ASAS cohort: a final analysis.

OBJECTIVE: To establish the predictive validity of the Assessment of SpondyloArthritis international Society (ASAS) spondyloarthritis (SpA) classification criteria. METHODS: 22 centres (N=909 patients) from the initial 29 ASAS centres (N=975) participated in the ASAS-cohort follow-up study. Patients had either chronic (>3 months) back pain of unknown origin and age of onset below 45 years (N=658) or peripheral arthritis and/or enthesitis and/or dactylitis (N=251). At follow-up, information was obtained at a clinic visit or by telephone. The positive predictive value (PPV) of the baseline classification by the ASAS criteria was calculated using rheumatologist's diagnosis at follow-up as external standard. RESULTS: In total, 564 patients were assessed at follow-up (345 visits; 219 telephone) with a mean follow-up of 4.4 years (range: 1.9; 6.8) and 70.2% received a SpA diagnosis by the rheumatologist. 335 patients fulfilled the axial SpA (axSpA) or peripheral SpA (pSpA) criteria at baseline and of these, 309 were diagnosed SpA after follow-up (PPV SpA criteria: 92.2%). The PPV of the axSpA and pSpA criteria was 93.3% and 89.5%, respectively. The PPV for the 'clinical arm only' was 88.0% and for the 'clinical arm'±'imaging arm' 96.0%, for the 'imaging arm only' 86.2% and for the 'imaging arm'+/-'clinical arm' 94.7%. A series of sensitivity analyses yielded similar results (range: 85.1-98.2%). CONCLUSIONS: The PPV of the axSpA and pSpA criteria to forecast an expert's diagnosis of 'SpA' after more than 4 years is excellent. The 'imaging arm' and 'clinical arm' of the axSpA criteria have similar predictive validity and are truly complementary.

Digital process for an implant-supported fixed dental prosthesis: A clinical report.

A digital process is presented for an implant-supported single-tooth and a 3-unit fixed dental prosthesis (FDP) with customized abutments and monolithic prosthetic zirconia restorations. The digital impression on the implant level was made with a TRIOS intraoral scanner (3Shape). This process included the fabrication of an implant cast with the fused deposition modeling technique and a 3-dimensional printing process with integrated implant analogs. The process enabled the FDPs to be designed with CAD/CAM on the cast before patient contact. Designing a printed implant cast expands the use of the digital workflow in the dental field.

The biochemical characteristics of wear testing lubricants affect polyethylene wear in orthopaedic pin-on-disc testing.

Lubricant protein concentration is known to affect crosslinked polyethylene wear in in vitro testing; however, the biochemical nature of these lubricants may also have a significant effect on wear and dictate its clinical relevance. A modified approach to pin-on-disc testing was implemented to explore the effect of four biochemically different lubricants on the wear of two types of crosslinked polyethylene materials (XLK™ and Marathon™; DePuy Synthes, Warsaw, IN, USA). XLK was associated with higher wear rates than Marathon. In comparison to lubricants containing deionized water, lubricants containing phosphate buffered saline solution and hyaluronic acid increased osmolality by up to 1.2 times and thermal stability by up to 1.4 times. This biochemical change reduced wear by up to 12.5 times. Wear rates for XLK and Marathon differed by a factor of 3.2 using lubricants with phosphate buffered saline solution as the dilutive media, but only 2.0 for lubricants with deionized water. Interestingly, varying the concentration of hyaluronic acid did not have a significant effect on wear, and differences between XLK and Marathon wear rates were not found to be statistically significant when hyaluronic acid was added to the lubricant. The findings of this study showed that increasing the osmolality and thermal stability of lubricants to more clinical levels decreased wear; however, the effect of hyaluronic acid on wear may not be apparent in simplistic pin-on-disc testing. It was suggested that phosphate buffered saline solution be used as the dilutive media of choice in order to better differentiate the ranking of materials while maintaining some clinical relevance.

Corrosion on the acetabular liner taper from retrieved modular metal-on-metal total hip replacements.

Eight retrieved metal-on-metal total hip replacements displayed corrosion damage along the cobalt-chromium alloy liner taper junction with the Ti alloy acetabular shell. Scanning electron microscopy indicated the primary mechanism of corrosion to be grain boundary and associated crevice corrosion, which was likely accelerated through mechanical micromotion and galvanic corrosion resulting from dissimilar alloys. Coordinate measurements revealed up to 4.3mm(3) of the cobalt-chromium alloy taper surface was removed due to corrosion, which is comparable to previous reports of corrosion damage on head-neck tapers. The acetabular liner-shell taper appears to be an additional source of metal corrosion products in modular total hip replacements. Patients with these prostheses should be closely monitored for signs of adverse reaction towards corrosion by-products.

An energy dissipation and cross shear time dependent computational wear model for the analysis of polyethylene wear in total knee replacements.

The cost and time efficiency of computational polyethylene wear simulations may enable the optimization of total knee replacements for the reduction of polyethylene wear. The present study proposes an energy dissipation wear model for polyethylene which considers the time dependent molecular behavior of polyethylene, aspects of tractive rolling and contact pressure. This time dependent - energy dissipation wear model was evaluated, along with several other wear models, by comparison to pin-on-disk results, knee simulator wear test results under various kinematic conditions and knee simulator wear test results that were performed following the ISO 14243-3 standard. The proposed time dependent - energy dissipation wear model resulted in improved accuracy for the prediction of pin-on-disk and knee simulator wear test results compared with several previously published wear models.

Biochemical analyses of human osteoarthritic and periprosthetic synovial fluid.

Biochemical analyses were performed on osteoarthritic and periprosthetic synovial fluid in order to propose changes to lubricant specifications currently outlined in orthopaedic wear testing standards. Osteoarthritic and periprosthetic synovial fluid samples were obtained from the hip and knee joints of 40 patients. The samples in each group were analysed and compared in order to identify differences between the protein concentration, constituent fractions, osmolality, thermal stability and the hyaluronic acid concentration and molecular weight distribution of osteoarthritic and periprosthetic synovial fluid. The average total protein concentration was approximately 30 g/L, which was much higher than the 20 g/L currently specified in the knee wear testing standard; however, the 30 g/L protein concentration matched the recently revised standard for hip simulator wear testing. No significant difference was found between the protein concentration, osmolality, thermal stability, and hyaluronic acid concentration of osteoarthritic and periprosthetic synovial fluid. The clinical data provided should be used to better define the composition of a more clinically relevant lubricant for orthopaedic wear testing.