AIMS Tissue responses to debris formed by abrasion of polymethylmethacrylate (PMMA) spacers at two-stage revision arthroplasty for prosthetic joint infection are not well described. We hypothesised that PMMA debris induces immunomodulation in periprosthetic tissues. PATIENTS AND METHODS Samples of tissue were taken during 35 two-stage revision arthroplasties (nine total hip and 26 total knee arthroplasties) in patients whose mean age was 67 years (44 to 85). Fourier transform infrared microscopy was used to confirm the presence of PMMA particles. Histomorphometry was performed using Sudan Red and Haematoxylin-Eosin staining. CD-68, CD-20, CD-11(c), CD-3 and IL-17 antibodies were used to immunophenotype the inflammatory cells. All slides were scored semi-quantitatively using the modified Willert scoring system. RESULTS The mean CD-68 scores did not show any significant change during the six weeks between the stages. Perivascular and diffuse scores showed significant difference in CD-3, CD-20, CD-11(c) and IL-17. At the time of re-implantation, a shift in the pattern of the expression of dendritic cells towards a perivascular arrangement and towards the periphery of PMMA particles was observed. Positive microbiological cultures were found at the time of re-implantation in three patients. Five further revisions were required for other reasons. CONCLUSION Our results represent a biological reaction of the synovial tissues to spacers with a less diffuse expression of dendritic cells and an increased expression of perivascular lymphocytes. The use of spacers in two-stage revision for infection probably induces an immunomodulation of synovial tissues. Cite this article: Bone Joint J 2016;98-B:1062-8.

The peri-prosthetic tissue response to wear debris is complex and influenced by various factors including the size, area and number of particles. We hypothesised that the 'biologically active area' of all metal wear particles may predict the type of peri-prosthetic tissue response. Peri-prosthetic tissue was sampled from 21 patients undergoing revision of a small diameter metal-on-metal (MoM) total hip arthroplasty (THA) for aseptic loosening. An enzymatic protocol was used for tissue digestion and scanning electron microscope was used to characterise particles. Equivalent circle diameters and particle areas were calculated. Histomorphometric analyses were performed on all tissue specimens. Aspirates of synovial fluid were collected for analysis of the cytokine profile analysis, and compared with a control group of patients undergoing primary THA (n = 11) and revision of a failed ceramic-on-polyethylene arthroplasty (n = 6). The overall distribution of the size and area of the particles in both lymphocyte and non-lymphocyte-dominated responses were similar; however, the subgroup with lymphocyte-dominated peri-prosthetic tissue responses had a significantly larger total number of particles. 14 cytokines (interleukin (IL)-1ß, IL-2, IL-4, IL-5, IL-6, IL-10, IL-13, IL-17, interferon (IFN)-γ, and IFN-gamma-inducible protein 10), chemokines (macrophage inflammatory protein (MIP)-1α and MIP-1ß), and growth factors (granulocyte macrophage colony stimulating factor (GM-CSF) and platelet derived growth factor) were detected at significantly higher levels in patients with metal wear debris compared with the control group. Significantly higher levels for IL-1ß, IL-5, IL-10 and GM-CSF were found in the subgroup of tissues from failed MoM THAs with a lymphocyte-dominated peri-prosthetic response compared with those without this response. These results suggest that the 'biologically active area' predicts the type of peri-prosthetic tissue response. The cytokines IL-1ß, IL-5, IL-10, and GM-CSF are associated with lymphocyte-dominated tissue responses from failed small-diameter MoM THA.

PURPOSE OF THE STUDY This prospective, open, non-controlled clinical investigation evaluated the performance of a modern post-operative wound dressing versus conventional dressings used on wounds of patients after undergoing hip or knee replacement. METHODS The clinical investigation started with a two-week observation phase of conventional wound dressings, followed by an intervention phase where patients were treated with Mepilex® Border Post-Op dressings. The primary objective was to evaluate the occurrence of blisters. RESULTS There was no blistering in any of the patients in the Mepilex group (n = 49), whereas blistering occurred in 27.3% (n = 3) of patients in the conventional group (n =  11, p < 0.01). The Mepilex dressing was left on for seven days in 70% of patients. There was a significant reduction in the total cost for dressing changes with the Mepilex dressings (p = 0.006). CONCLUSION By using Mepilex dressings, the risk of blistering was negated and the reduced frequency of dressing changes was associated with the reduced overall cost. Therefore, we recommend the use of Mepilex Border Post-Op dressings.

Two-stage exchange arthroplasty is the current standard of care for arthroplasty-related infections. Reinfection rates up to 30% are reported, and there is significant morbidity for the patient. In cases of failure, arthrodesis or amputation may result. Ultrasonic treatment has the potential to eradicate biofilms and avoid two-stage exchange arthroplasty. Data in the specific context of arthroplasty infections is scant, and there is debate regarding optimal frequency and intensity of treatment. Surface topography alterations of the endoprosthetic components and damage to adjacent bone and cartilage have not been investigated. We found incomplete biofilm eradication and significant increase in surface roughness (maximum peak-to-valley height) of cobalt-chrome unicondylar knee components as well as reduction in articular cartilage thickness area from 10 retrieved femoral heads after low-frequency sonication treatment according to manufacturer-specified recommendations. Our data collectively suggest that sonication treatment for biofilm eradication in arthroplasty infections may not be effective and surface topography alterations may potentially reduce implant longevity.

Large-diameter metal-on-metal (MoM) bearings evolved from the success of hip resurfacing. These implants were used in revision surgery in cases with well-fixed acetabular cups but loose or failed femoral stems, to avoid cup revision. Early data showed low rates of dislocation and potentially low wear profiles due to better fluid film lubrication. The risk of impingement was also thought to be low due to the increased head-neck ratio. Subsequently large-diameter MoM heads gained popularity in primary hip replacement. Recent data has emerged on the unacceptably high revision rates among patients with large-diameter MoM total hip arthroplasties (THAs), high blood levels of metal ions, and adverse tissue reactions. The head-neck (cone-taper) modular interface probably represents the weak link in large metal heads that have been used on conventional tapers. Increased torque of the large head, micromotion, and instability at the cone-taper interface, synergistic interactions between corrosion and wear, edge loading, low clearance, and psoas impingement are the likely causes for early failure of these prostheses.

BACKGROUNDTissue responses to periprosthetic metal wear debris are complex and poorly understood. There are two predominant tissue responses: a nonspecific macrophage-mediated granulomatous response and lymphocyte-dominated response, which has immunological memory and is mediated by T cells. Delayed hypersensitivity-type responses may accelerate aseptic loosening of arthroplasty implants. We hypothesized that the metal content of periprosthetic tissue but not of serum would be predictive of the type of tissue response to metal wear debris.METHODSWe examined twenty-eight total hip arthroplasty implant retrievals from twenty-seven patients who had undergone revision arthroplasty at one institution. Indications for revision were pain and/or osteolysis; one patient had recurrent dislocations. Tissue samples were analyzed microscopically and the metal (Co, Cr, and Ni) content was determined. Explanted prosthetic components were examined for linear wear. Intraoperatively, periprosthetic metallosis was observed in twelve cases and formation of a bursa (pseudotumor) was observed in thirteen. The acetabular cup was loose in eleven cases, the femoral stem was loose in five, and both components were loose in five.RESULTSThe metal (Co, Cr, and Ni) content of the periprosthetic tissue ranged from 1.4 to 4604.0 μg/g. Histologically, macrophages containing metal particles as well as diffuse and perivascular lymphocytic infiltration were observed. Fibrin exudation was also visible. Tissues that displayed a predominantly lymphocytic response had a mean metal content of 222.2 ± 52.9 μg/g, whereas those that displayed a macrophage-dominated response had a metal content of 3.0 ± 0.9 μg/g; this difference was significant (p = 0.001). The mean serum metal content did not differ significantly between the two subgroups (60.7 ± 13.4 compared with 43.7 ± 3.8 μg/L, p = 0.105).CONCLUSIONSAn association between periprosthetic tissue metal content and hypersensitivity appears likely but needs to be validated with larger-scale retrieval studies.CLINICAL RELEVANCEThis study contributes to the understanding of tissue responses to metal wear debris after joint replacement and the factors that are predictive of a type-IV lymphocyte-dominated hypersensitivity reaction.

Background Metal-on-metal (MoM) THAs have reduced wear rates compared with metal-on-polyethylene. However, elevated serum metal ion levels and pseudotumors have been reported in large MoM articulations. Questions/purposes We therefore determined (1) if corrosion occurred at the cone/taper interface leading to instability in patients with large-diameter THAs; (2) how patients presented clinically and radiographically; (3) if adverse periprosthetic tissue reactions occurred; (4) whether metal was released from the implants into the periprosthetic tissues; and (5) if head size correlated with metal release. Methods We reviewed 114 patients who had revisions of large-diameter head MoM articulations. Mean time of implantation was 46 months. To identify adverse reactions and particle load, tissues were stained by hematoxylin and eosin and CD3/CD20/CD68 antibodies. Periprosthetic tissues were analyzed for metal content and distribution in different regions. Electrochemical reactions between the stem and adapter were investigated by a minicell electrode. Results Electrochemical studies on the stem and the head adapter showed a risk for galvanic corrosion. Ninety-four percent of patients had instability at the cone/taper interface. All patients presented with early clinical symptoms; 59 patients had radiographic signs of loosening. One hundred four patients had foreign body reactions and necrosis. The largest amounts of metal released were titanium or iron. We found no correlation between head size and metal ion release. Conclusions These findings suggest that in modular cone/taper connections, friction of the MoM articulations may cause failure of the cone/taper interface leading to galvanic corrosion and loosening. It is unclear whether the design of this MoM system provides sufficient stability at the taper.