M. Boffano

Interplay between surface properties of standard, vitamin E blended and oxidised ultra high molecular weight polyethylene used in total joint replacement and adhesion of Staphylococcus aureus and Escherichia coli

We have assessed the different adhesive properties of some of the most common bacteria associated with periprosthetic joint infection on various types of ultra high molecular Weight Polyethylene (UHMWPE). Quantitative in vitro analysis of the adhesion of biofilm producing strains of Staphylococcus aureus and Escherichia coli to physically and chemically characterised standard UHMWPE (PE), vitamin E blended UHMWPE (VE-PE) and oxidised UHMWPE (OX-PE) was performed using a sonication protocol. A significant decreased bacterial adhesion was registered for both strains on VE-PE, in comparison with that observed on PE, within 48 hours of observation (S. aureus p = 0.024 and E. coli p = 0.008). Since Vitamin E reduces bacterial adhesive ability, VE-stabilised UHMWPE could be valuable in joint replacement by presenting excellent mechanical properties, while reducing bacterial adhesiveness.

Management of the first episode of traumatic shoulder dislocation

Shoulder joint dislocation is the most common joint dislocation seen in the emergency department. Traumatic dislocation may cause damage to the soft-tissues surrounding the shoulder joint and sometimes to the bone. The treatment, which aims at restoration of a fully functioning, pain-free and stable shoulder, includes either conservative or surgical management preceded by closed reduction of the acute dislocation. Conservative management usually requires a period of rest, generally involving immobilisation of the arm in a sling, even though it is still debated whether to immobilise the shoulder in internal or external rotation. Operative management, with no significant differences in term of re-dislocation rates between open and arthroscopic repair, incorporates soft-tissue reconstructions and/or bony procedures and is recommended in young male adults engaged in highly demanding physical activities. At our institution, non-operative management is favoured particularly for patients with multi-directional instability or soft-tissue laxity. Conservative measures are often preferred in older patients or younger patients that are not actively engaged in overhead activities. Immediate surgery on all first-time dislocations may subject many patients to surgery who would not have had any future subluxation. For these reasons, initially we will always try physical therapy and activity modification for the vast majority of our patients. Cite this article: EFORT Open Rev 2017;2:35-40.DOI: 10.1302/2058-5241.2.160018.

Ultra high molecular weight polyethylene is cytotoxic and causes oxidative stress, even when modified

Ultra High Molecular Weight (UHMW) Polyethylene (PE) is the most used biomaterial for articulating surface of total joint replacements (TJR). Since its introduction decades ago, many efforts have been made to improve its properties and to understand its behaviour with the final goal to provide a longer duration of the implants. Mechanical abrasion with particles production is an unavoidable process, but catastrophic PE wear with a huge quantity of PE reactive debris production was observed in the last years, with consequent severe periprosthetic osteolysis and aseptic loosenings. Now it is well known that the severe PE particle disease is due to UHMWPE oxidative degradation caused by a ysterilization in air (1-4). In order to solve this problem, the evolution of the conventional UHMWPE drove to alternative sterilization methods (ethylene oxide and gas plasma) and to the development of new PE derivatives with a supposed increased resistance to abrasion in vivo, such as the crosslinked PE (X-PE) and the vitamin Estabilized PE (E-PE), Unfortunately, particle disease and periprosthetic osteolysis still remain an unsolved problem (5-9). The osteolysis is an inflammatory process caused by a foreign body (10), wherein the particles trigger monocyte recruitment and macrophage activation, leading to chronic inflammation, with release of cytokines and proteases, and bone reabsorption (8). It is well recognized that PE particles induce different reactions according to dimension (fragments larger than 10 J.1m produce foreign body-induced giant cell granuloma, whereas smaller fragments are phagocytized), number, shape, superficial hydrophobicity and oxidation (11-14). The majority of the studies have been focused on how conventional and new PEs develop debris particles different in sizes and behaviours, reacting in different ways with human cells and conducting to unpredictable clinical results (7, 15-17). But beside the shape and the dimension of a PE particle, the chemico-physical properties of its surface might playa fundamental role in stimulating the inflammatory reaction, the cytotoxicity and the apoptosis. In particular, it has been suggested that PE particles per se do not cause any response although macrophages are activated, probably due to the superficial characteristics of PE and macrophage binding receptors. Different approaches have shown that some markers of inflammation and oxidative stress were induced after exposure to UHMWPE, in particular to their debris: among them, lactate dehydrogenase (LDH) release and lipid peroxidation (19) and cytokines production (20) have been observed. The mechanisms by which these events occur are not still well elucidated. Some authors demonstrated that in particular the oxidized UHMWPE is toxic in different cellular models: Reno et al. (21) showed that oxidized UHMWPE reduced proliferation in human fibroblasts and induced a strong release of gelatinase B (matrix metalloproteinase 2, MMP-2), and the surface oxidation of UHMWPE has been correlated to increased apoptosis and necrosis in human granulocytes (22). Moreover, the oxidation of UHMWPE has been strongly related to the development of inflammation around the implants (23) and Fiorito et al. (24) demonstrated that, in this inflammatory status, the production of reactive oxygen species (ROS) by inflamed synovial cells plays a very crucial role. The supplementation ofX-PE and E-PE hasbeen shown

The surgical treatment of acromioclavicular joint injuries

Acromioclavicular joint (ACJ) injuries are common, but their incidence is probably underestimated. As the treatment of some sub-types is still debated, we reviewed the available literature to obtain an overview of current management. We analysed the literature using the PubMed search engine. There is consensus on the treatment of Rockwood type I and type II lesions and for high-grade injuries of types IV, V and VI. The treatment of type III injuries remains controversial, as none of the studies has proven a significant benefit of one procedure when compared with another. Several approaches can be considered in reaching a valid solution for treating ACJ lesions. The final outcome is affected by both vertical and horizontal post-operative ACJ stability. Synthetic devices, positioned using early open or arthroscopic procedures, are the main choice for young people. Type III injuries should be managed surgically only in cases with high-demand sporting or working activities. Cite this article: EFORT Open Rev 2017;2:432–437. DOI: 10.1302/2058-5241.2.160085.