Comparison of extracapsular pseudotumors seen in magnetic resonance imaging and in revision surgery of 167 failed metal-on-metal hip replacements

Background and purpose

Magnetic resonance imaging (MRI) is important for detecting extracapsular pseudotumors, but there is little information on the accuracy of MRI and appropriate intervals for repeated imaging. We evaluated the sensitivity and specificity of MRI for detecting pseudotumors in 155 patients (167 hips) with metal-on-metal (MoM) hip arthroplasties that failed due to adverse reactions to metal debris (ARMD).

Methods

Preoperative MRIs were performed with two 1.5 T MRI scanners and graded by a senior musculoskeletal radiologist using a previously described MRI pseudotumor grading system. Revision findings were retrieved from surgical notes, and pseudotumors were retrospectively graded as fluid-filled, mixed-type, or solid.

Results

The sensitivity of MRI was 71% and the specificity was 87% for detecting extracapsular pseudotumors. The sensitivity was 88% (95% CI: 70–96) when MRI was performed less than 3 months before the revision surgery. Interestingly, when the time that elapsed between MRI and revision was more than 1 year, the sensitivity calculated was only 29% (95% CI: 14–56). Comparison between MRI and revision classifications gave moderate agreement (Cohen’s kappa = 0.4).

Interpretation

A recent MRI predicts the presence of a pseudotumor well, but there is more discrepancy when the MRI examination is over a year old, most likely due to the formation of new pseudotumors. 1 year could be a justifiable limit for considering a new MRI if development of ARMD is suspected. MRI images over a year old should not be used in decision making or in planning of revision surgery for MoM hips.Metal-on-metal (MoM) hip replacements have been widely used for the treatment of hip osteoarthritis, particularly in young and active patients (Bozic et al. 2009). During the last few years, an increased risk of developing soft tissue reactions linked to increased wear of MoM articulation has been reported (Pandit et al. 2008, Kwon et al. 2010, Langton et al. 2011). An umbrella term “adverse reaction to metal debris” (ARMD) has been used to describe these tissue reactions, which include metallosis, aseptic lymphocytic vasculitis-associated lesions, and the fluid-filled or solid extracapsular lesions often referred to as pseudotumors (Langton et al. 2011). Most patients have high blood metal ions and many experience pain in the groin and thigh region, but ARMD may also be found in patients presenting with no clinical symptoms and normal whole-blood metal ion levels (Hart et al. 2011, Wynn-Jones et al. 2011). Asymptomatic extracapsular pseudotumors have been reported to increase and decrease in size with occasional remission of small masses, and they may involve the abductor and iliopsoas muscles (Almousa et al. 2013). Revision surgeries because of pseudotumors have been reported to have significantly poorer outcome than hip revisions for other reasons (Grammatopolous et al. 2009). Imaging is therefore needed to identify these patients for closer follow-up or revision surgery. Preoperative magnetic resonance imaging (MRI) is also of importance for surgeons to visualize the location and dimensions of the pseudotumor for optimal resection (Liddle et al. 2013).MRI and ultrasonography are the main imaging modalities for assessment of ARMD lesions. Modern MRI techniques allow good visibility in the hip region, even though intracapsular lesions cannot be reliably assessed in some cases due to metal artifacts. To our knowledge, only 1 study has compared pseudotumors seen in MRI with those actually found in revision surgery (Liddle et al. 2013).The main aim of this study was to evaluate the ability of preoperative MRI to detect extracapsular pseudotumors encountered in revision surgery and to assess appropriate intervals for repeated imaging, when development/progression of soft tissue pathologies is suspected. A secondary aim was to ascertain whether pseudotumors fall into the same categories in both MRI and revision surgery classifications.     

Acute leukocyte,cytokine and adipocytokine responses to maximal and hypertrophic resistance exercise bouts

The purpose of this study was to examine the acute immune response (circulating levels of leukocytes, cytokines and adipocytokines) to maximal resistance (MAX, 15 × 1RM) and hypertrophic resistance (HYP, 5 × 10RM) exercise bouts. Twelve healthy men (age = 28.2 ± 3.5 years, weight = 78.6 ± 10.4 kg, height 178.8 ± 5.0 cm, fat percentage = 16.5 ± 3.5 %) participated in the study. Blood was sampled before, immediately after and 15 and 30 min after exercise. Leukocytes (WBC) significantly increased immediately after HYP (p < 0.01), whereas in MAX, increases in WBC became significant after 30 min (p < 0.05). Lymphocytes increased only after HYP (p < 0.001), while MAX induced lymphopenia during recovery (p < 0.01). Monocyte chemoattractant protein-1 (MCP-1) decreased (p < 0.05) and interleukin-1 receptor antagonist (IL-1ra) increased after HYP, which were not observed after MAX. Adipsin and resistin decreased after both exercise bouts (p < 0.05), which suggest that heavy resistance exercise is at least transiently beneficial for adipocytokine profile. Immediate mechanical stress seemed similar as no differences in myoglobin response were observed. The higher magnitude of metabolic demand reflected in higher lactate response in HYP could be the reason for the significantly high responses in WBC, IL-1ra and decrease in MCP-1.     

Evaluation of pure-tone audiometric protocols in vestibular schwannoma screening

The objective was to evaluate the pure-tone audiogram-based screening protocols in VS diagnostics. We retrospectively analyzed presenting symptoms, pure tone audiometry and MRI finding from 246 VS patients and 442 controls were collected to test screening protocols (AAO-HNS, AMCLASS-A/B, Charing Cross, Cueva, DOH, Nashville, Oxford, Rule3000, Schlauch, Seattle, Sunderland) for sensitivity and specificity. Results were pooled with data from five other studies, and analysis of sensitivity, specificity and positive likelihood ratio (LR+) for each protocol was performed. Our results show that protocols with significantly higher sensitivity (AMCLASS-A/B, Nashville) show also significantly lowest specificity, and tend to have low association (positive likelihood ratio, LR+) to the VS. The highest LR+ was found for protocols AAO-HNS, Rule3000 and Seattle. In conclusions, knowing their properties, screening protocols are simple decision-making tools in VS diagnostic. To use the advantage of the highest sensitivity, protocols AMCLASS-A + B or Nashville can be of choice. For more reasonable approach, applying the protocols with high LR+ (AAO-HNS, Rule3000, Seattle) may reduce the overall number of MRI scans at expense of only few primarily undiagnosed VS.     

Repair bond strength of restorative resin composite applied to fiber-reinforced composite substrate

Delamination or fracture of composite veneers can occur as a result of improper design of the fiber-reinforced composite (FRC) framework. This in vitro study tested the repair bond strength of restorative composite to aged FRC. The substrate was multiphase polymer matrix FRC (everStick) aged by boiling for 8 h and storing at 37 degrees C in water for 6 weeks. The aged substrate surfaces were wet-ground flat with 1200-grit silicon carbide paper and subjected randomly to 5 different surface treatments: 1) An adhesion primer (Composite Activator) and resin (CA), 2) Silane (EspeSil) and resin (SIL-MP), 3) Silane, adhesive primer, and resin (Clearfil Repair) (CF), 4) Air particle-abrading (CoJet), silane, and resin (CJ-SIL-MP), 5) Resin (Scotchbond Multipurpose Resin) only as control (MP). Restorative composite resin (Z250) was added to the substrate in 2 mm layer increments and light-cured. Subsequently, every surface treatment group was divided into 2 subgroups of 12 specimens each. The specimens were either 48 h water-stored or thermocycled (6000 x 5-55 degrees C). The shear bond strengths of composite resin to FRC were measured at a crosshead speed of 1.0 mm/min. The data were analyzed by ANOVA for factors 'treatment type' and 'storage condition'; Tukey's post-hoc tests and Weibull analysis were performed. ANOVA showed a significant difference as a function of surface treatment (P<0.05) and storage condition (P<0.05). The CJ-SIL-MP group showed highest bond strength and Weibull modulus after thermocycling. Repair of multiphase polymer matrix FRC may show reliable bond strength when silane treatment is used along with air-particle abrading.     

Subjective ratings of fear are associated with frontal late positive potential asymmetry,but not with early brain activity over the occipital and centro-parietal cortices

The human frontal cortex is asymmetrically involved in motivational and affective processing. Several studies have shown that the left-frontal hemisphere is related to positive and approach-related affect, whereas the right-frontal hemisphere is related to negative and withdrawal-related affect. The present study aimed to investigate whether evolutionarily threatening stimuli modulate asymmetrical frontal activity. We examined hemispheric differences in frontal late positive potentials (f-LPP asymmetry) and frontal alpha power activation (frontal alpha asymmetry, FAA) in response to images depicting snakes, spiders, butterflies, and birds. Results showed that the late component of f-LPP asymmetry, but not FAA, was modulated by the category of stimuli. Specifically, threatening stimuli (snakes and spiders) evoked a relatively large late f-LPP over the right-frontal hemisphere than non-threatening stimuli (birds and butterflies). Moreover, this relatively great right-frontal activity was positively associated with the subjective ratings of fear. Importantly, the subjective ratings of fear were not associated with early brain activity over the occipital or centro-parietal cortices. These results suggest that late f-LPP asymmetry may reflect higher order affective processes, specifically the subjective appraisal of threatening stimuli and the subjective experience of fear, that are independent of the fast and automatic processing of evolutionarily significant and affectively arousing stimuli.