Changes in habitat associations during range expansion: disentangling the effects of climate and residence time

The distributions of many species are not at equilibrium with their environment. This includes spreading non-native species and species undergoing range shifts in response to climate change. The habitat associations of these species may change during range expansion as less favourable climatic conditions at expanding range margins may constrain species to use only the most favourable habitats, violating the species distribution model assumption of stationarity. Alternatively, changes in habitat associations could result from density-dependent habitat selection; at range margins, population densities are initially low so species can exhibit density-independent selection of the most favourable habitats, while in the range core, where population densities are higher, species spread into less favourable habitat. We investigate if the habitat preferences of the non-native common waxbill Estrilda astrild changed as they spread in three directions (north, east and south-east) in the Iberian Peninsula. There are different degrees of climatic suitability and colonization speed across range expansion axes, allowing us to separate the effects of climate from residence time. In contrast to previous studies we find a stronger effect of residence time than climate in influencing the prevalence of common waxbills. As well as a strong additive effect of residence time, there were some changes in habitat associations, which were consistent with density-dependent habitat selection. The combination of broader habitat associations and higher prevalence in areas that have been colonised for longer means that species distribution models constructed early in the invasion process are likely to underestimate species’ potential distribution

Hip arthroplasty in patients younger than 30 years: excellent ten to 16-year follow-up results with a HA-coated stem

It is well accepted that youth and high activity levels are among the factors that increase the risk of mechanical failure of total hip prostheses. However, there are few reports of long-term results in very young patients. In this study, we evaluated the results of total 49 hip replacements (THRs) using an uncemented total hip prosthesis in 44 patients (28 females) who were 30 years or younger (range: 15–30 years). The diagnosis was ostearthritis due to congenital dislocations in 28 patients, with the remaining patients having diagnoses of sequelae of fracture, infection, Calve-Legg-Perthes disease, avascular necrosis, chondrodystrophia and epiphyseal dysplasia. In all cases we used an uncemented straight stem fully coated with hydroxyapatite (HA). In 36 cases we used a hemispherical cup inserted with press fit, and in seven cases we used a hemispherical screw cup. The patients were evaluated ten to 16 years (mean: 13 years) after the operation by radiographic and clinical examinations, including the Harris Hip, WOMAC and EuroQol-5D scores. In a sub-group of nine patients with a unilateral prosthesis, the muscle strength of the quadriceps and hamstrings was tested using a Cybex 6000. None of the stems were revised at the follow-up examination, and all were classified as well integrated, with no signs of radiological loosening. Twenty-four hips had revision of the acetabular component due to mechanical failure. The Harris Hip score was, on average, 88 (range: 62–100), the WOMAC score 80 (range: 37–100) and the EuroQol score 0.68 (range: −0.14–1). Isokinetic muscle strength testing showed that seven of the nine tested patients were weaker on the operated side. In conclusion, we found mechanical failures at the acetabular side, but excellent results with a fully HA-coated femoral stem, with no revisions after ten to 16 years

Twenty-year results of the cementless Corail stem

The concept of an extensive hydroxyapatite (HA) coating for the fixation of a tapered femoral stem (Corail®) was introduced 25 years ago in the hope that we could achieve durable biological fixation while preserving normal periprosthetic bone activity. The value of uncemented fixation using HA-coated implants is now widely admitted. However, the characteristics of implant coating and more specifically its extent still remain a subject of debate or even controversy. This prospective study conducted over a 20-year period has greatly contributed to demonstrating the reliability of the Corail® prosthesis, in terms of functional abilities, radiographic evidence and global survivorship. A full HA coating applied on a straight and proximally flared stem induces substantial short-, mid- and long-term benefits without any deleterious effects reported. Modifications of the bone pattern have been strictly limited: slight resorption at the calcar level, absence of cortical hypertrophy and alleged stress shielding. The radiological “silence” is one of the paramount facts clearly demonstrated