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The prospect of biomaterial hypersensitivity developing in response to joint implant materials was first presented more than 30 years ago. Many studies have established probable causation between first-generation metal-on-metal hip implants and hypersensitivity reactions. In a limited patient population, implant failure may ultimately be related to metal hypersensitivity. The examination of hypersensitivity reactions in current-generation metal-on-metal knee implants is comparatively limited. The purpose of this study is to summarize all available literature regarding biomaterial hypersensitivity after total knee arthroplasty, elucidate overall trends about this topic in the current literature, and provide a foundation for clinical approach considerations when biomaterial hypersensitivity is suspected.

Background/ObjectivesExpanding visceral adiposity is associated with increased inflammation and increased risk for developing obesity-related comorbidities. The goal of this study was to examine high fat diet (HFD)-induced differences in adipocyte size and cytokine/chemokine expression in visceral and subcutaneous adipose depots in obesity-prone (OP) and obesity-resistant (OR) rats.MethodsOP and OR rats were fed either a low fat diet (LFD, 10% kilocalories from fat) or HFD (60% kilocalories from fat) for 7 weeks. Adipocyte size and the presence of crown-like structures in epididymal and inguinal adipose tissue were determined. A multiplex cytokine/chemokine panel was used to assess the expression of inflammatory markers in epididymal and inguinal adipose tissues.ResultsA higher percentage of large adipocytes (> 5000 μm2) was detected in the epididymal and inguinal adipose tissues of OP rats and a higher percentage of small adipocytes (< 4000 μm2) was detected in the epididymal and inguinal adipose tissues of OR rats. More crown-like structures were identified in epididymal adipose tissue of OP rats fed a LFD, compared to OR rats. Consumption of a HFD increased the number of crown-like structures in OR, but not OP rats. Epididymal expression of pro-inflammatory cytokines (IL-1β, TNF-α) was higher in OP rats, compared to OR rats fed LFD. HFD consumption increased epididymal expression of GM-CSF, IL-1α, IL-1β, IL-6, MIP-2, and TNF-α in OP and OR rats. Inguinal expression of pro-inflammatory cytokines (IL-1α, IL-1β, TNF-α) was higher in OP rats, compared to OR rats.ConclusionsOverall, these data suggest that a higher susceptibility to developing obesity is characterized by large adipocytes and increased visceral adipose inflammation. Interestingly, in OR rats, the detrimental effects of HFD consumption on visceral adipose inflammation are evident with only small increases in weight and adiposity, suggesting that HFD also increases the risk for obesity-related comorbidities in OR rats.

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Acrylic bone cement has a variety of applications in orthopedic surgery. Primary uses in total arthroplasties are limited to prostheses fixation and antibiotic delivery. With the large number of total joint arthroplasties expected to continue to rise, understanding the role bone cement plays in the success of total joint arthroplasty can have a significant impact on daily practice. The literature is inconclusive on whether cemented or cementless fixation technique is superior, and choice of fixation type is mainly determined by surgeon preference and experience. Surgeons should understand that if poor techniques exist, short-term outcomes of the replaced joint may be at risk. Statement of clinical significance: This article attempts to clarify some points of bone cement use through a review of the mechanical properties related to bone cement, a comparison to alternative materials, influence of additives, and the effects on surgical outcomes. ß