Breakdown and Modification of Microplastic Beads by Aeolian Abrasion.

Saltation is an important wind erosion process that can cause the modification and breakdown of particles by aeolian abrasion. It is recognized that microplastic particles can be transported by wind, but the effect of saltation on microplastic properties is unknown. This study examined the impact of simulated saltation alongside quartz grains on the size, shape, and surface properties of spherical microplastic beads. The diameter of the microplastics was reduced by 30-50% over 240-300 h of abrasion with a mass loss of c. 80%. For abrasion periods up to 200 h, the microplastic beads remained spherical with minimal change to overall shape. Over 95% of the fragments of plastic removed from the surface of the microbeads during the abrasion process had a diameter of ≤10 µm. In addition, during the abrasion process, fine particles derived from breakdown of the quartz grains became attached to the surfaces of the microbeads resulting in a reduction in carbon and an increase in silicon detected on the particle surface. The results suggest that microplastics may be mechanically broken down during aeolian saltation and small fragments produced have the potential for long distance transport as well as being within the size range for human respiration.

De novo Propionibacterium acnes septic arthritis.

We report the third identifiable case of septic arthritis due to Propionibacterium acnes arising in the absence of prior surgical intervention. This anaerobic Gram-positive bacillus is now recognised as an important cause of postoperative infections, typically presenting in an indolent fashion some months after surgery. Reports of de novo septic arthritis due to P. acnes are exceedingly rare. Our case adds to the literature and significantly broadens the reported pathogenic potential of the organism, which in this instance has caused rapid and serious joint destruction.

Ten-year survival and clinical outcome of the AcroFlex lumbar disc replacement for the treatment of symptomatic disc degeneration.

BACKGROUND CONTEXT: We have previously reported on the osseointegration, stability, and preserved motion of the AcroFlex lumbar disc replacement (LDR) in a nonhuman primate model. Detailed biomechanical testing of the device predicted implant survival for at least 10 years of in vivo use. Significant improvements in the clinical outcome were reported at 2 years. However, mechanical failure of the polyolefin rubber was detected by fine-cut computed tomography (CT) in a number of subjects within 2 years. As a result, no further devices were implanted. PURPOSE: To report on the 10-year survival and clinical outcome of the AcroFlex elastomeric LDR when used for the treatment of one- or two-level symptomatic disc degeneration between L4 and S1. STUDY DESIGN: Prospective nonrandomized clinical trial with a mean 10-year follow-up. PATIENT SAMPLE: Twenty-eight patients with symptomatic disc degeneration who underwent AcroFlex LDR at one or two levels. OUTCOME MEASURES: Clinical: Visual Analog Score for back pain, Oswestry Disability Index (ODI), Low Back Outcome Score (LBOS), and Short Form-36 (SF-36). Survival: Kaplan-Meier analysis over 10 years with first revision surgery as the end point. Radiographic: Dynamic flexion/extension radiographs at 2 years. Magnetic resonance imaging (MRI) and CT scans at 10 years. METHODS: Twenty-eight subjects (14 male, mean age 41 years) with symptomatic disc degeneration unresponsive to nonsurgical treatment were enrolled into a prospective nonrandomized trial of the AcroFlex LDR. Visual analog score for back pain, ODI, LBOS, and SF-36 questionnaires were administered preoperatively at 6 months, 1, 2, and 10 years after the index procedure. All subjects were invited to undergo an MRI and for those with the device remaining in situ, a lumbar CT scan. Kaplan-Meier survival analysis was performed with first revision surgery as the end point. RESULTS: At a mean of 9 years, 8 months (range, 8 years, 8 months-11 years, 3 months) after surgery, 17 of 28 patients did not require a revision surgery, representing a cumulative survival of 60.7%. In contrast, 11 of 28 patients (39.3%) underwent a total of 14 revision procedures; 9 of 11 patients underwent a conversion to anterior lumbar interbody fusion supplemented with pedicle screw fixation. Indications for a revision included device failure in seven and disabling pain in four patients. Mean time to revision was 3 years, 10 months (range, 23 months-8 years, 4 months). Mean ODI at 10 years for nonrevision cases was 27.5 (±17.6) compared with 41.8 (±26) for revision cases. Mean improvement over 10 years in the ODI for nonrevision cases was 17.9 (±16.9) compared with 12 (±16.1) for revision cases. Similar trends were observed in LBOS and SF-36 scores. Radiographic findings in the revision group included midsubstance tears in the rubber, osteolysis, and implant displacement. CT findings in 11 of 17 survivors included heterotopic bone formation (85%), osteolysis (50%), and subsidence (14%). Magnetic resonance imaging in 14 of 23 subjects at the final follow-up demonstrated an adjacent-level disc degeneration in 68% of those with the AcroFlex LDR in situ and in 40% of those who had been converted to fusion. Skip-level disc degeneration was present in 44% of those with AcroFlex device in situ and in 20% of those who had been converted to fusion. CONCLUSIONS: The cumulative survival was 60.7% at 10 years when the first revision surgery was taken as the end point. The etiology of the implant failure prompting the revision included failure of osseointegration, midsubstance elastomeric tears, and osteolysis. Further use of this implant is not justified. The incidence of adjacent-level disc degeneration for the AcroFlex was comparable with that observed adjacent to the spinal fusion. Salvage procedures involving conversion to spinal fusion are technically demanding, but appear to improve outcomes modestly.

Prevalence of interdigital nerve enlargements in an asymptomatic population.

BACKGROUND: Morton's neuroma is a common primary diagnosis for referral to foot and ankle surgeons. On presentation, many patients have had an ultrasound reporting the presence of Morton's neuroma, which may not correlate with the clinical examination findings. The prevalence of such sonographic findings in the general population remains unknown. METHODS: In this observational prospective study, patients with asymptomatic forefeet who were seen by two foot and ankle surgeons for unrelated mid- or hind foot pathology were examined clinically and sonographically for the presence of interdigital nerve thickening. Forty-eight volunteers participated in the study (96 feet). For the purpose of this study, asymptomatic thickenings greater than 5 mm in diameter were termed sonographic neuromas. Ultrasound examination was performed by two specialist musculoskeletal radiologists. RESULTS: Fifty-four percent of the volunteers (26 of 48) had sonographic nerve thickening and in 17 cases (35.4%) enlarged nerves were found bilaterally. Differences for gender, original diagnosis or side of original pathology were not significant. Older subjects were more likely to have a sonographic neuroma (p = 0.018). Feet with a positive Mulder's click were more likely to have a sonographic neuroma (p = 0.015). CONCLUSION: Ultrasound, even in highly skilled hands, has a high rate of incidental finding of an asymptomatic interdigital nerve enlargement, which can lead to a false diagnosis of a Morton's neuroma. Sonographic evidence of Morton's neuroma per se is unreliable unless it is correlated with an equivocal clinical examination. Clinical examination is still the gold standard for the diagnosis of a Morton's neuroma.