Taxonomy and ecology of the Western Australian Soldier Crab, Mictyris Occidentalis (Crustacea: Decapoda: Brachyura: Mictyridae)

The taxonomy and autoecology of the Western Australian soldier crab, Mictyris occidentalis Unno, 2008 is presented including a new species description, a comprehensive ichnology, sampling methods, an extensive habitat description and a decadal population dynamics study. Such a wide ranging, holistic study has not been carried out for any mictyrid specious previously. In detail, a taxonomy component compares M. occidentalis with congeners, clearly establishing it as a separate species from M. longicarpus to which it was previously referred, and the issues affecting taxonomic classification in the Mictyris genus in general are discussed. A species identification key is provided for the genus. A full suite of ichnological products created by M. occidentalis including cavities, shafts, exit holes, pellets, rosettes, tunnels and pustular structures, is described and related to the behaviour and life stages of the crab from juvenile to adult. The principle of understanding the behaviour of a species before designing sampling strategies is illustrated, using the example of the rapid burrowing escape mechanism employed by M. occidentalis. The habitats of M. occidentalis are described across its entire geographic range encompassing thousands of kilometres of coastline. Factors characterising the soldier crab habitat are investigated from the regional, to large, to local, to micro-geomorphic habitat scale including the abiotic factors of wave energy, tidal level, submergence frequency, the sediment characteristics of grain size, composition, moisture content, salinity and also groundwater salinity. Also, the biotic factors of the densities of sea couch roots and mangrove pneumatophores are considered. A model of the soldier crab habitat is provided for prediction of the presence/absence of soldier crab populations in any particular coastal zone. The results of a 30 year study of the population dynamics of M. occidentalis in King Bay, Dampier Archipelago are presented in which the juvenile recruitment patterns, intra and interannual abundance and size classes of the population and gender composition and size classes of swarms and subsurface population components are determined. Periods of ovigery of M. occidentalis females are compared with those of other mictyrid species. The lifecyle of M. occidentalis is determined to consist of a cryptic infaunal phase for most of the crab’s life followed by an emergent adult stage. Swarms comprise predominantly adult males with most females and all juveniles remaining in the subsurface during a swarm event. The extended period of swarming adults on a tidal flat is explained by the extended period of juvenile recruitment resulting in a continuous series of cohorts reaching maturity and commencing the emergent phase. Environmental management recommendations to conserve populations of M. occidentalis are provided based on a synthesis of the findings of this ecological study

A Variant of the Sciatic Nerve and its Clinical Implications.

Variants of gluteal neural anatomy are important to consider, especially during surgical approaches to the hip. During the routine dissection of the gluteal region, a variant of the sciatic nerve was found where the nerve left the pelvis fully split into its tibial and common fibular components. Intrapelvically and extrapelvically, there was no splitting of the two components by the piriformis muscle. Distally, the two parts of the nerve were draped over the medial and lateral edges of the ischial tuberosity. To avoid iatrogenic injury to the sciatic nerve during invasive or surgical approaches to this region, all possible anatomical variations, such as the one presented herein, should be appreciated by the clinician

Docteur, ma fracture est-elle solide?

The adequate treatment of fractures consists of a conservative or surgical approach whose goal is to assure a rapid solidity of the fracture site that will lead to a durable complete healing without complications. Fracture healing criteria remain controversial. In this article we are trying to present the tools used in the evaluation of bone consolidation and propose therapeutical guidelines aiming at the return to daily activities in full security

Ablation du matériel d'ostéosynthèse: un mal nécessaire?

Hardware removal should be decided only after careful examination of the medical and economic implications. Current literature fails to offer systematic guidelines. Infected hardware, non-union after surgery or obvious mechanical problems are straightforward indications for implant removal. However, when motivated by pain alone, the procedure can have disappointing results, and patients' expectations should be consequently moderated. Protection against toxicity, allergy, carcinogenesis or possible implant failure should not prompt systematic removal. Hardware removal in children should be considered separately, since metallic implants can interfere with normal growth patterns. Overall, implant removal should not be considered a routine procedure, and indications for surgery should reflect the thorough examination of the risks and the benefits

Epidemiology and imaging of the subchondral bone in articular cartilage repair

Articular cartilage and the subchondral bone act as a functional unit. Following trauma, osteochondritis dissecans, osteonecrosis or osteoarthritis, this intimate connection may become disrupted. Osteochondral defects-the type of defects that extend into the subchondral bone-account for about 5% of all articular cartilage lesions. They are very often caused by trauma, in about one-third of the cases by osteoarthritis and rarely by osteochondritis dissecans. Osteochondral defects are predominantly located on the medial femoral condyle and also on the patella. Frequently, they are associated with lesions of the menisci or the anterior cruciate ligament. Because of the close relationship between the articular cartilage and the subchondral bone, imaging of cartilage defects or cartilage repair should also focus on the subchondral bone. Magnetic resonance imaging is currently considered to be the key modality for the evaluation of cartilage and underlying subchondral bone. However, the choice of imaging technique also depends on the nature of the disease that caused the subchondral bone lesion. For example, radiography is still the golden standard for imaging features of osteoarthritis. Bone scintigraphy is one of the most valuable techniques for early diagnosis of spontaneous osteonecrosis about the knee. A CT scan is a useful technique to rule out a possible depression of the subchondral bone plate, whereas a CT arthrography is highly accurate to evaluate the stability of the osteochondral fragment in osteochondritis dissecans. Particularly for the problem of subchondral bone lesions, image evaluation methods need to be refined for adequate and reproducible analysis. This article highlights recent studies on the epidemiology and imaging of the subchondral bone, with an emphasis on magnetic resonance imaging

Are criteria for islet and pancreas donors sufficiently different to minimize competition?

Islet and pancreas transplantation may compete for a limited number of organs. We analyzed records from the national Swiss transplant registry during a 4-year period to investigate the proportion of donors that are suitable for islet and pancreas transplantation. Suitability for pancreas transplantation was mainly defined as: age 10-45 years; weight <or= 80 kg; BMI <or= 25 kg/m(2); amylasemia <or= 150 U/l; ICU stay <or= 3 days and absence of severe hypotension (MAP <or= 60 mmHG). Between 1.1.1997 and 31.12.2000, data of 407 donors were collected, from which 321 donors were included in the study. Thirty-three (10%), 143 (45%), and 23 (7%) donors fulfilled the criteria for pancreas, islet transplantation, and both procedures, respectively. Giving priority to pancreas transplantation and accepting the absence of one selection criterion, 90 (28%) pancreas and 100 (31%) islet donors were identified. We conclude that with current allocation policies prioritizing pancreas transplantation, pancreas and islet transplantation may coexist with little competition

Cement augmentation in sacroiliac screw fixation offers modest biomechanical advantages in a cadaver model

BACKGROUND: Sacroiliac screw fixation in elderly patients with pelvic fractures is prone to failure owing to impaired bone quality. Cement augmentation has been proposed as a possible solution, because in other anatomic areas this has been shown to reduce screw loosening. However, to our knowledge, this has not been evaluated for sacroiliac screws. QUESTIONS/PURPOSES: We investigated the potential biomechanical benefit of cement augmentation of sacroiliac screw fixation in a cadaver model of osteoporotic bone, specifically with respect to screw loosening, construct survival, and fracture-site motion. METHODS: Standardized complete sacral ala fractures with intact posterior ligaments in combination with ipsilateral upper and lower pubic rami fractures were created in osteoporotic cadaver pelves and stabilized by three fixation techniques: sacroiliac (n = 5) with sacroiliac screws in S1 and S2, cemented (n = 5) with addition of cement augmentation, and transsacral (n = 5) with a single transsacral screw in S1. A cyclic loading protocol was applied with torque (1.5 Nm) and increasing axial force (250-750 N). Screw loosening, construct survival, and sacral fracture-site motion were measured by optoelectric motion tracking. A sample-size calculation revealed five samples per group to be required to achieve a power of 0.80 to detect 50% reduction in screw loosening. RESULTS: Screw motion in relation to the sacrum during loading with 250 N/1.5 Nm was not different among the three groups (sacroiliac: 1.2 mm, range, 0.6-1.9; cemented: 0.7 mm, range, 0.5-1.3; transsacral: 1.1 mm, range, 0.6-2.3) (p = 0.940). Screw subsidence was less in the cemented group (3.0 mm, range, 1.2-3.7) compared with the sacroiliac (5.7 mm, range, 4.7-10.4) or transsacral group (5.6 mm, range, 3.8-10.5) (p = 0.031). There was no difference with the numbers available in the median number of cycles needed until failure; this was 2921 cycles (range, 2586-5450) in the cemented group, 2570 cycles (range, 2500-5107) for the sacroiliac specimens, and 2578 cycles (range, 2540-2623) in the transsacral group (p = 0.153). The cemented group absorbed more energy before failure (8.2 × 10(5) N*cycles; range, 6.6 × 10(5)-22.6 × 10(5)) compared with the transsacral group (6.5 × 10(5) N*cycles; range, 6.4 × 10(5)-6.7 × 10(5)) (p = 0.016). There was no difference with the numbers available in terms of fracture site motion (sacroiliac: 2.9 mm, range, 0.7-5.4; cemented: 1.2 mm, range, 0.6-1.9; transsacral: 2.1 mm, range, 1.2-4.8). Probability values for all between-group comparisons were greater than 0.05. CONCLUSIONS: The addition of cement to standard sacroiliac screw fixation seemed to change the mode and dynamics of failure in this cadaveric mechanical model. Although no advantages to cement were observed in terms of screw motion or cycles to failure among the different constructs, a cemented, two-screw sacroiliac screw construct resulted in less screw subsidence and greater energy absorbed to failure than an uncemented single transsacral screw. CLINICAL RELEVANCE: In osteoporotic bone, the addition of cement to sacroiliac screw fixation might improve screw anchorage. However, larger mechanical studies using these findings as pilot data should be performed before applying these preliminary findings clinically