Patient-Specific Contact Stress Does Not Predict Polyethylene Wear Rate in a Specific Pressfit Cup.

BACKGROUND: The most common reason for revision total hip arthroplasty remains polyethylene wear. Development dysplasia of the hip and revision situations requires a conscious compromise of implant position. The surgeon should know about the consequence on wear via a possible change in hip contact force. The objective of this study is to investigate whether annual wear is dependent on hip contact force. METHODS: Forty-five inserts (DuraLoc, DePuy) that were explanted in our department were included. Three-dimensional gravimetric determination of the wear was performed by fluid displacement. Then, the hip contact force was determined using radiographs according to the Blumentritt model. RESULTS: No correlation was found between patient-specific factors and the annual wear. The hip contact force estimated by the Blumentritt model also showed no correlation between hip contact force and annual wear. Two single model parameters correlated significantly with wear: VRECAB as a ratio of the lever length of the spinocrural and the pelvitrochanteric muscles and the angle Alpha as a measure of the position of the center of rotation in relation to the greater trochanter. The greater the ratio spinocrural/pelvitrochanteric lever arm (R = 0.408, P = .005) and the greater the Alpha angle (more valgus the femoral neck) (R = 0.377, P = .011) were, the greater was the wear. CONCLUSION: These results lead to the conclusion that neither patient-specific factors nor the estimated hip contact force have a major influence on annual wear in the case of DuraLoc cups. Only a coxa valga and a small femoral offset contribute in a limited amount to an increase in wear.

Silver-loaded seaweed-based cellulosic fiber improves epidermal skin physiology in atopic dermatitis: safety assessment, mode of action and controlled, randomized single-blinded exploratory in vivo study.

BACKGROUND: The epidermal part of the skin is the major interface between the internal body and the external environment. The skin has a specific physiology and is to different degrees adapted for protection against multiple exogenous stress factors. Clothing is the material with the longest and most intensive contact to human skin. It plays a critical role especially in inflammatory dermatoses or skin conditions with an increased susceptibility of bacterial and fungal infections like atopic dermatitis. Previously, we have shown a dose-dependent antibacterial and antifungal activity of silver-loaded seaweed-based cellulosic fibres. AIM OF THE STUDY: We studied the mode of action of silver-loaded seaweed-based cellulosic fiber and performed a broad safety assessment. The principal aim was to analyse the effects of wearing the textile on epidermal skin physiology in 37 patients with atopic dermatitis in a controlled, randomized single-blinded in vivo study. Furthermore, the sensitization potential was tested in a patch test in 111 panellists. RESULTS: We could demonstrate in vitro a dose-dependent scavenging of induced reactive oxygen species by silver-loaded seaweed-based cellulosic fibers. Safety assessment of these fibres showed no detectable release of silver ions. Furthermore, ex vivo assessment after 24 h application both in healthy volunteers and patients with atopic dermatitis by sequential tape stripping and subsequently raster electron microscopy and energy dispersive microanalysis analysis revealed no detectable amounts of silver in any of stratum corneum layers. Serum analysis of silver showed no detectable levels. The in vivo patch testing of 111 volunteers revealed no sensitization against different SeaCell Active (SeaCell GmbH, Rudolstadt, Germany) containing fabrics. The in vivo study on 37 patients with known atopic dermatitis and mild-to-moderate eczema on their arms were randomly assigned to either silver-loaded seaweed fibre T-shirts or to cotton T-shirts for 8 weeks. A significant reduction in Staphylococcus aureus colonization was detectable for the silver T-shirts compared with cotton T-shirts without any changes in non-pathogenic surface bacteria colonization. Furthermore, a more pronounced improvement in barrier function (transepidermal water loss) was observed in mildly involved eczema areas during the first 4 weeks of the study. Stratum corneum hydration and surface pH improved in both treatment groups over time. CONCLUSION: The tested silver-loaded seaweed fibre can be regarded as safe and seams to be suited for application in bio-active textiles in atopic dermatitis based on its positive in vivo activity.

Short-time pre-washing of brushite-forming calcium phosphate cement improves its in vitro cytocompatibility.

A pre-washing protocol was developed for resorbable, brushite-forming calcium phosphate cements (CPCs) to avoid harmful in vitro effects on cells. CPC discs (JectOS+, Kasios; self-developed CPC) were pre-washed with repeated changes of phosphate-buffered saline (PBS; 24h total). Unwashed or PBS-pre-washed discs were incubated in culture medium (5% fetal calf serum; up to 10days) and then tested for their influence on pH/calcium/phosphate levels in H2O extracts. Effects on pH/calcium/phosphate levels in culture supernatants, and morphology, adherence, number, and viability of ATDC5 cells and adipose-tissue derived stem cells were analyzed in co-culture. Pre-washing did not alter CPC surface morphology or Ca/P ratio (scanning electron microscopy; energy-dispersive X-ray spectroscopy). However, acidic pH of unwashed JectOS+ and self-developed CPC (5.82; 5.11), and high concentrations of Ca (2.17; 2.40mM) and PO4 (38.15; 49.28mM) in H2O extracts were significantly counteracted by PBS-pre-washing (pH: 7.92; 7.92; Ca: 0.64; 1.11mM; PO4: 5.39-5.97mM). Also, PBS-pre-washing led to physiological pH (approx. 7.5) and PO4 levels (max. 5mM), and sub-medium Ca levels (0.5-1mM) in supernatants and normalized cell morphology, adherence, number, and viability. This CPC pre-washing protocol improves in vitro co-culture conditions without influencing its structure or chemical composition.