A Novel Technique for Producing Three-Dimensional Data Using Serial Sectioning and Semi-Automatic Image Classification.

The three-dimensional characterization of internal features, via metrics such as orientation, porosity, and connectivity, is important to a wide variety of scientific questions. Many spatial and morphological metrics only can be measured accurately through direct in situ three-dimensional observations of large (i.e., big enough to be statistically representative) volumes. For samples that lack material contrast between phases, serial grinding and imaging­which relies solely on color and textural characteristics to differentiate features­is a viable option for extracting such information. Here, we present the Grinding, Imaging, Reconstruction Instrument (GIRI), which automatically serially grinds and photographs centimeter-scale samples at micron resolution. Although the technique is destructive, GIRI produces an archival digital image stack. This digital image stack is run through a supervised machine-learning-based image processing technique that quickly and accurately segments data into predefined classes. These classified data then can be loaded into three-dimensional visualization software for measurement. We share three case studies to illustrate how GIRI can address questions with a significant morphological component for which two-dimensional or small-volume three-dimensional measurements are inadequate. The analyzed metrics include: the morphologies of objects and pores in a granular material, the bulk mineralogy of polyminerallic solids, and measurements of the internal angles and symmetry of crystals.

Prosthetic Neck Fracture in Exeter V40 Stems: A Report of Two Cases and Review of Literature.

This report contains 2 acute fractures of the Exeter V40 stem with 2 different types of neck fracture, one at the subcapital level and another at the base of the neck. A review of relevant literature provides an insight into a similar pattern of failures reported in a certain subset of cases. We hypothesize that for high-BMI cases, attention to proper preoperative templating is mandatory. The operating surgeon should try to restore offset without having to use a long head in this subgroup of patients. We feel that trying to compensate for the offset with a long head may lead to high-stress concentration in the neck. This, in turn, may be responsible for the failure of the stem, as seen in the reported cases. We advocate, based on the literature, the need to recreate the offset carefully with as big a stem as possible to avoid these unique and rare complications. Reducing such failures may further improve the overall survivorship of the V40 Exeter stem.

Three-dimensional reconstructions of the putative metazoan Namapoikia show that it was a microbial construction.

Strata from the Ediacaran Period (635 million to 538 million years ago [Ma]) contain several examples of enigmatic, putative shell-building metazoan fossils. These fossils may provide insight into the evolution and environmental impact of biomineralization on Earth, especially if their biological affinities and modern analogs can be identified. Recently, apparent morphological similarities with extant coralline demosponges have been used to assign a poriferan affinity to Namapoikia rietoogensis, a modular encrusting construction that is found growing between (and on) microbial buildups in Namibia. Here, we present three-dimensional reconstructions of Namapoikia that we use to assess the organism's proposed affinity. Our morphological analyses, which comprise quantitative measurements of thickness, spacing, and connectivity, reveal that Namapoikia produced approximately millimeter-thick meandering and branching/merging sheets. We evaluate this reconstructed morphology in the context of poriferan biology and determine that Namapoikia likely is not a sponge-grade organism.

Geologic evidence for an icehouse Earth before the Sturtian global glaciation.

Snowball Earth episodes, times when the planet was covered in ice, represent the most extreme climate events in Earth's history. Yet, the mechanisms that drive their initiation remain poorly constrained. Current climate models require a cool Earth to enter a Snowball state. However, existing geologic evidence suggests that Earth had a stable, warm, and ice-free climate before the Neoproterozoic Sturtian global glaciation [ca. 717 million years (Ma) ago]. Here, we present eruption ages for three felsic volcanic units interbedded with glaciolacustrine sedimentary rocks from southwest Virginia, USA, that demonstrate that glacially influenced sedimentation occurred at tropical latitudes ca. 751 Ma ago. Our findings are the first geologic evidence of a cool climate teetering on the edge of global glaciation several million years before the Sturtian Snowball Earth.

Multiscale approach reveals that Cloudina aggregates are detritus and not in situ reef constructions.

The earliest metazoans capable of biomineralization appeared during the late Ediacaran Period (635-541 Ma) in strata associated with shallow water microbial reefs. It has been suggested that some Ediacaran microbial reefs were dominated (and possibly built) by an abundant and globally distributed tubular organism known as Cloudina If true, this interpretation implies that metazoan framework reef building-a complex behavior that is responsible for some of the largest bioconstructions and most diverse environments in modern oceans-emerged much earlier than previously thought. Here, we present 3D reconstructions of Cloudina populations, produced using an automated serial grinding and imaging system coupled with a recently developed neural network image classifier. Our reconstructions show that Cloudina aggregates are composed of transported remains while detailed field observations demonstrate that the studied reef outcrops contain only detrital Cloudina buildups, suggesting that Cloudina played a minor role in Ediacaran reef systems. These techniques have wide applicability to problems that require 3D reconstructions where physical separation is impossible and a lack of density contrast precludes tomographic imaging techniques.

Birmingham Hip Resurfacing: A Single Surgeon Series Reported at a Minimum of 10 Years Follow-Up.

We report outcomes on 120 Birmingham Hip Resurfacings (BHRs) (mean age 50 years) at a minimum of ten-years follow-up. Cases were performed by one surgeon and included his learning curve. Six hips were revised, with no revisions for infection, dislocation, or adverse reaction to metal debris. Ten-year survival was 94.2% (95% confidence interval (CI) 88.8%-98.7%) for all revisions and 96.1% (95% CI 91.5%-99.8%) for revisions for aseptic loosening. Gender (P = 0.463) and head size (P = 0.114) did not affect revision risk. Mean post-operative Harris hip score was 84.0. Contrary to previous independent reports, good outcomes into the second decade were achieved with the BHR in both men and women. Longer term follow-up will confirm whether these promising outcomes in women continue.

Assessing leg lengths intraoperatively in total hip arthroplasty: comparison of two methods.

Leg length discrepancy post total hip arthroplasty surgery is common. Unequal leg lengths after total hip arthroplasty is the single most common reason for litigation against orthopaedic surgeons. Different methods for leg length assessment are used intraoperatively by surgeons, but no one method is 100% reliable and reproducible. The aim of this study was to compare 2 methods of intraoperative leg length assessment. Leg length discrepancy of 5 mm or less was achieved in 72.5% (37/51) of patients using method 1 and in 67% (34/51) of patients using method 2. Both methods assessed produced a discrepancy of greater than 5 mm in about a quarter of the patients. The difference was not found to be statistically significant (p < 0.05). Assessment of leg lengths intraoperatively is challenging even for experienced surgeons. The leg lengths may be better restored if more than one method of assessment is used during surgery.

Computer navigation experience in hip resurfacing improves femoral component alignment using a conventional jig.

BACKGROUND: The use of computer navigation has been shown to improve the accuracy of femoral component placement compared to conventional instrumentation in hip resurfacing. Whether exposure to computer navigation improves accuracy when the procedure is subsequently performed with conventional instrumentation without navigation has not been explored. We examined whether femoral component alignment utilizing a conventional jig improves following experience with the use of imageless computer navigation for hip resurfacing. MATERIALS AND METHODS: Between December 2004 and December 2008, 213 consecutive hip resurfacings were performed by a single surgeon. The first 17 (Cohort 1) and the last 9 (Cohort 2) hip resurfacings were performed using a conventional guidewire alignment jig. In 187 cases, the femoral component was implanted using the imageless computer navigation. Cohorts 1 and 2 were compared for femoral component alignment accuracy. RESULTS: All components in Cohort 2 achieved the position determined by the preoperative plan. The mean deviation of the stem-shaft angle (SSA) from the preoperatively planned target position was 2.2° in Cohort 2 and 5.6° in Cohort 1 (P = 0.01). Four implants in Cohort 1 were positioned at least 10° varus compared to the target SSA position and another four were retroverted. CONCLUSIONS: Femoral component placement utilizing conventional instrumentation may be more accurate following experience using imageless computer navigation.

Is estimated peri-operative glomerular filtration rate associated with post-operative mortality in fractured neck of femur patients?

AIM: Comparison of renal function in patients who died within 30 days of surgery for hip fractures with surviving patients matched for age, type of surgery, type of anaesthesia and clinical assessment of fitness for surgery. MATERIALS & METHODS: A retrospective case-control study of 80 patients was performed. Pre- and post-operative urea, creatinine, estimated glomerular filtration rate (eGFR), sodium and potassium of 40 patients who died within 30 days post-surgery (cases) were compared with 40 patients who survived matched for age, sex, surgical procedure and pre-operative ASA grade (controls). Statistical analysis involved univariable analysis by paired t-test and logistic conditional regression analysis. RESULTS: Pre- and post-operative mean serum creatinine were significantly higher in patients who died compared with surviving controls (pre-op 108.2 vs. 90.2 micromol/l [p=0.002], post-op 103.9 vs. 87.1 micromol/l [p=0.003]). However, mean creatinine values for both groups were still within normal laboratory reference ranges. Mean serum urea was also higher in patients who died (pre-op 8.81 vs. 6.75 mmol/l [p=0.010] and post-op 9.30 vs. 6.63 mmol/l [p=0.004], respectively). Pre- and post-operative eGFR was significantly lower in those patients who died within 30 days of hip fracture surgery (pre-op 61.75 vs. 68.78 ml/min per 1.73 m(2) [p=0.011], post-op 63.03 vs. 76.03 ml/min per 1.73 m(2) [p=0.009]). The mean eGFR values for survivors and non-survivors fell in the chronic kidney disease mild renal impairment category. There were no significant differences in mean serum sodium or potassium concentration between groups. Stepwise conditional logistic regression analysis, showed that after allowing for creatinine, urea was no longer significantly related to mortality. CONCLUSION: These results suggest that when allowance is made for demography, fitness for surgery and surgical procedure, subtle reductions in eGFR are still associated with mortality risk. However, these are of questionable clinical use.