SummaryExposure to titanium (Ti) from implants and from personal care products as nanoparticles (NPs) is common. This article reviews exposure sources, ion release, skin penetration, allergenic effects, and diagnostic possibilities. We conclude that human exposure to Ti mainly derives from dental and medical implants, personal care products, and foods. Despite being considered to be highly biocompatible relative to other metals, Ti is released in the presence of biological fluids and tissue, especially under certain circumstances, which seem to be more likely with regard to dental implants. Although most of the studies reviewed have important limitations, Ti seems not to penetrate a competent skin barrier, either as pure Ti, alloy, or as Ti oxide NPs. However, there are some indications of Ti penetration through the oral mucosa. We conclude that patch testing with the available Ti preparations for detection of type IV hypersensitivity is currently inadequate for Ti. Although several other methods for contact allergy detection have been suggested, including lymphocyte stimulation tests, none has yet been generally accepted, and the diagnosis of Ti allergy is therefore still based primarily on clinical evaluation. Reports on clinical allergy and adverse events have rarely been published. Whether this is because of unawareness of possible adverse reactions to this specific metal, difficulties in detection methods, or the metal actually being relatively safe to use, is still unresolved.Key words: contact allergy; corrosion; dermatitis; hypersensitivity; lymphocyte transformation test; patch test; penetration; release; titanium; toxicity. Titanium (Ti) is a non-essential metallic element with the atomic number 22 and a silvery colour. It is the ninth most abundant element in the earth's crust and the seventh most abundant metal overall (1). Major deposits of Ti minerals are found in Australia, Canada, India, Norway, South Africa, Ukraine, and the United States. The +4 oxidation state dominates Ti chemistry, but compounds in the +3 oxidation state are also common. TheCorrespondence: Jacob P. Thyssen, National Allergy Research Centre, Department of Dermato-Allergology, Copenhagen University Hospital HerlevGentofte, University of Copenhagen, Kildegaardsvej, DK-2900 Hellerup, Denmark. Tel: +45 3977 7307; Fax: +45 3977 7118. E-mail: jacob.p. thyssen@regionh.dk Accepted for publication 8 February 2016most important oxide is Ti dioxide (TiO 2 ), which exists in three different crystalline forms -anatase, brookite, and rutile -in addition to an amorphous phase (2, 3). Both the anatase, rutile and brookite mineral forms of TiO 2 occur naturally.TiO 2 is widely applied as microparticles and nanoparticles (NPs) in consumer goods, including cosmetics and foods, to obtain a white colour and ultraviolet light protection (4). Moreover, Ti is combined with a variety of other elements to produce strong lightweight alloys that provide resistance against corrosion and show a very high strength/density ratio (5). Because of this and the...

Background and purpose It has been speculated that the prevalence of metal allergy may be higher in patients with implant failure. We compared the prevalence and cause of revisions following total hip arthroplasty (THA) in dermatitis patients suspected to have contact allergy and in patients in general with THA. Furthermore, we compared the prevalence of metal allergy in dermatitis patients with and without THA.Materials and methods The Danish Hip Arthroplasty Registry (DHAR) contained detailed information on 90,697 operations. The Gentofte patch-test database contained test results for patients suspected of having allergic contact dermatitis (n = 18,794). Cases (n = 356) were defined as patch-tested dermatitis patients who also had primary THA performed. Two age- and sex-matched controls (n = 712) from the patch-test database were sought for each case.Results The prevalence of revision was similar in cases (12%) and in patients from the DHAR (13%). The prevalence of metal allergy was similar in cases and controls. However, the prevalence of metal allergy was lower in cases who were patch-tested after operation (6%) than in those who were patch-tested before operation (16%) (OR = 2.9; 95% CI = 1–8).Interpretation We found that the risk of surgical revision was not increased in patients with metal allergies and that the risk of metal allergy was not increased in cases who were operated, in comparison to controls. Despite some important study limitations, our observations add to the evidence that the risk of complications in metal allergic patients seems limited.

The primary aim was to identify muscle-tendon-related pain in 100 patients with hip dysplasia. The secondary aim was to test whether muscle-tendon-related pain is associated with self-reported hip disability and muscle strength in patient with hip dysplasia. One hundred patients (17 men) with a mean age of 29 years (SD 9) were included. Clinical entity approach was carried out to identify muscle-tendon-related pain. Associations between muscle-tendon-related pain and self-reported hip disability and muscle strength were tested with multiple regression analysis, including adjustments for age and gender. Self-reported hip disability was recorded with the Copenhagen Hip and Groin Outcome Score (HAGOS), and muscle strength was assessed with a handheld dynamometer. Iliopsoas- and abductor-related pain were most prevalent with prevalences of 56% (CI 46; 66) and 42% (CI 32; 52), respectively. Adductor-, hamstrings- and rectus abdominis-related pain were less common. There was a significant inverse linear association between muscle-tendon-related pain and self-reported hip disability ranging from −3.35 to − 7.51 HAGOS points in the adjusted analysis (P < 0.05). Besides the association between muscle-tendon-related pain and hip extension a significant inverse linear association between muscle-tendon-related pain and muscle strength was found ranging from −0.11 to − 0.12 Nm/kg in the adjusted analysis (P < 0.05). Muscle-tendon-related pain exists in about half of patients with hip dysplasia with a high prevalence of muscle-tendon-related pain in the iliopsoas and the hip abductors and affects patients' self-reported hip disability and muscle strength negatively.

It is often difficult to interpret the relevance of a positive patch test reaction to cobalt, and there is a need for further studies to determine sources of cobalt exposure.

Background and purpose — Larger prospective studies investigating periacetabular osteotomy (PAO) with patient-reported outcome measures developed for young patients are lacking. We investigated changes in patient-reported outcome (PRO), changes in muscle–tendon pain, and any associations between them from before to 1 year after PAO.Patients and methods — Outcome after PAO was investigated in 82 patients. PRO was investigated with the Copenhagen Hip and Groin Outcome Score (HAGOS). Muscle–tendon pain in the hip and groin region was identified with standardized clinical tests, and any associations between them were analyzed with multivariable linear regressions.Results — HAGOS subscales improved statistically significantly from before to 1 year after PAO with effect sizes ranging from medium to very large (0.66–1.37). Muscle–tendon pain in the hip and groin region showed a large decrease in prevalence from 74% (95% CI 64–83) before PAO to 35% (95% CI 25–47) 1 year after PAO. Statistically significant associations were observed between changes in HAGOS and change in the sum of muscle–tendon pain, ranging from –4.7 (95% CI –8.4 to –1.0) to –8.2 (95% CI –13 to –3.3) HAGOS points per extra painful entity across all subscales from before to 1 year after PAO.Interpretation — Patients with hip dysplasia experience medium to very large improvements in PRO 1 year after PAO, associated with decreased muscle–tendon pain. The understanding of hip dysplasia as solely a joint disease should be reconsidered since muscle–tendon pain seems to play an important role in relation to the outcome after PAO.