The present study showed promising results for the use of antimicrobial peptides and other biomarkers in synovial fluid for the diagnosis of periprosthetic joint infection, and analysis of the levels in synovial fluid was more accurate than analysis of serum.

Locally destructive soft tissue pseudotumor has been reported in patients following metal-on-metal hip resurfacing arthroplasty (MoMHRA). A delayed hypersensitivity reaction type IV to nickel (Ni), chromium (Cr), or cobalt (Co) has been suggested to play a role in its aetiology. The aim of this study was to investigate the incidence and level of metal-induced systemic hypersensitivity in patients with MoMHRA, both with and without pseudotumor by measuring lymphocyte proliferation responses to metals. A total of 92 patients were investigated: (1) MoMHRA patients with pseudotumors (nine female, one male); (2) MoMHRA patients without pseudotumors (30 female, 30 male); and (3) age-matched control subjects without metal implants (9 female, 13 male). The venous blood samples were collected for serum Ni, Co, and Cr ion level measurements and lymphocyte transformation tests (LTT). A higher incidence and level of enhanced lymphocyte reactivity only to Ni was found in patients with MoMHRA compared to the patients without MoM implants, reflecting exposure and immune reactivity. However, lymphocyte reactivity to Co, Cr, and Ni did not significantly differ in patients with pseudotumors compared to those patients without pseudotumors. This suggests that systemic hypersensitivity type IV reactions, as measured by lymphocyte proliferation response to these metals, may not be the dominant biological reaction involved in the occurrence of the soft tissue pseudotumors. ß

There are very few reports on hypersensitivity reactions in association with titanium-based materials so that the existence of allergy to titanium is still put in question. We report on a patient in whom impaired fracture healing and eczema localized to the perioperative area developed upon titaniumbased osteosynthesis. Patch testing gave no reactions to titanium nor to nickel, chromium, or cobalt. However, in the lymphocyte transformation test, the patient's lymphocytes showed markedly enhanced proliferation in vitro to titanium. After removal of the titanium material, fracture healing was achieved and the eczema cleared. Parallel to this, in vitro hyperreactivity to titanium disappeared. Although contact allergic reactions to titanium have been very rarely reported, these findings support a diagnosis of titanium allergy in our patient. Metallic alloys are used in large number for osteosynthesis and long-term implants. In association with stainless-steel-based and cobalt-based materials, contact hypersensitivity reactions have been described and were mostly attributed to chromium, cobalt, nickel, and occasionally to molybdenum. In contrast, due to its excellent biocompatibility (1), titanium is not considered to provoke allergic reactions. However, in view of the few reports on contact dermatitis or granulomatous reactions to titanium upon its use in pacemakers or implants (2-4), the discussion about 'titanium allergy' is still ongoing. Patients and MethodsA 35-year-old male was referred for evaluation of suspected hypersensitivity to implant materials. He presented with a several months history of hand eczema and failure of healing of a hand fracture. Eczema had started within few weeks after an osteosynthesis of right metacarpal fracture by use of a pure titanium miniplate and screws. The patient had gradually developed itching, erythema, and scaling of the right hand together with a vesiculopapular eruption on several fingers, mainly on their ventral parts. Over the next weeks, lesions extended also to the left hand ( Fig. 1) and proximal part of the forearms. There was a history of seasonal rhinoconjunctivitis and asthma but not of previous contact or atopic eczema or hypersensitivity reactions to metals. The patient was otherwise healthy. Under the diagnosis of contact dermatitis, a corticosteroid-containing cream was prescribed and patch testing was planned. Patch testing was performed according to the guidelines of the German Contact Dermatitis Research Group on the patient's upper back with the following series: standard, vehicles, disinfectants, and preservatives. In addition, TiO 2 was tested. Evaluation of the reactions was done after 2, 3, and 7 days. Removed implant materials were not available for subsequent, additional testing.For the lymphocyte transformation test, peripheral blood mononuclear cells (PBMC) were isolated from heparinized blood samples of the patient and a healthy control, as well as of 49 additional controls over the next months. Within

Electromagnetic fields (EMF) have been shown to exert beneficial effects on cartilage tissue. Nowadays, differentiated human mesenchymal stem cells (hMSCs) are discussed as an alternative approach for cartilage repair. Therefore, the aim of this study was to examine the impact of EMF on hMSCs during chondrogenic differentiation. HMSCs at cell passages five and six were differentiated in pellet cultures in vitro under the addition of human fibroblast growth factor 2 (FGF-2) and human transforming growth factor-β(3) (TGF-β(3) ). Cultures were exposed to homogeneous sinusoidal extremely low-frequency magnetic fields (5 mT) produced by a solenoid or were kept in a control system. After 3 weeks of culture, chondrogenesis was assessed by toluidine blue and safranin-O staining, immunohistochemistry, quantitative real-time polymerase chain reaction (PCR) for cartilage-specific proteins, and a DMMB dye-binding assay for glycosaminoglycans. Under EMF, hMSCs showed a significant increase in collagen type II expression at passage 6. Aggrecan and SOX9 expression did not change significantly after EMF exposure. Collagen type X expression decreased under electromagnetic stimulation. Pellet cultures at passage 5 that had been treated with EMF provided a higher glycosaminoglycan (GAG)/DNA content than cultures that had not been exposed to EMF. Chondrogenic differentiation of hMSCs may be improved by EMF regarding collagen type II expression and GAG content of cultures. EMF might be a way to stimulate and maintain chondrogenesis of hMSCs and, therefore, provide a new step in regenerative medicine regarding tissue engineering of cartilage.

Skin test, examination of peri-implantar tissue, and the prompt healing after replacement of the osteosynthesis material suggest an allergic reaction. PCR analysis of peri-implantar tissue can further help to identify and understand allergy-mediated implant intolerance reactions.