Bone orthotropic remodeling as a thermodynamically-driven evolution

International audienceIn this contribution we present and discuss a model of bone remodeling set up in the framework of the theory of generalized continuum mechanics and first introduced by DiCarlo et al.[1]. Bone is described as an orthotropic body experiencing remodeling as a rotation of its microstruc-ture. Thus, the complete kinematic description of a material point is provided by its position in space and a rotation tensor describing the orientation of its microstructure. Material motion is driven by energetic considerations , namely by the application of the Clausius-Duhem inequality to the microstructured material. Within this framework of orthotropic re-modeling, some key features of the remodeling equilibrium configurations are deduced in the case of homogeneous strain or stress loading conditions. First, it is shown that remodeling equilibrium configurations correspond to energy extrema. Second, stability of the remodeling equilibrium configurations is assessed in terms of the local convexity of the strain and complementary energy functionals hence recovering some classical energy theorems. Eventually, it is shown that the remodeling equilibrium configurations are not only highly dependent on the loading conditions, but also on the material properties

Trapped in the morphospace: The relationship between morphological integration and functional performance

The evolution of complex morphological structures can be characterized by the interplay between different anatomical regions evolving under functional integration in response to shared selective pressures. Using the highly derived humeral morphology of talpid moles as a model, here we test whether functional performance is linked to increased levels of evolutionary integration between humerus subunits and, if so, what the strength is of the relationship. Combining two-dimensional geometric morphometrics, phylogenetic comparative methods, and functional landscape modeling, we demonstrate that the high biomechanical performance of subterranean moles’ humeri is coupled with elevated levels of integration, whereas taxa with low-performance values show intermediate or low integration. Theoretical morphs occurring in high-performance areas of the functional landscape are not occupied by any species, and show a marked drop in covariation levels, suggesting the existence of a strong relationship between integration and performance in the evolution of talpid moles’ humeri. We argue that the relative temporal invariance of the subterranean environment may have contributed to stabilize humeral morphology, trapping subterranean moles in a narrow region of the landscape and impeding any attempt to reposition on a new ascending slope

New systematic insights about Plio-Pleistocene moles from Poland

The generic attribution of the Plio-Pleistocene Polish moles Neurotrichus? polonicus and Neurotrichus? skoczeni has been questioned several times in the past. The fossil material belonging to Neurotrichus? polonicus and Neurotrichus? skoczeni is re-evaluated here and a new diagnosis is provided on the basis of qualitative considerations. In addition, a Geometric Morphometric analysis of the humerus has been performed including both extant and extinct Neurotrichini and Urotrichini taxa for comparison. Our results proved the unique morphology of the Polish material suggesting a distinct taxonomic state. The morphological variations evidenced by the humeral shape analysis agree with the observed qualitative differences and support a new generic allocation. The new genus Rzebikia gen. nov. is proposed for all the material previoulsly ascribed to Neurotrichus? polonicus and Neurotrichus? skoczeni

Repair of sphincter urethral strictures preserving urinary continence: surgical technique and outcomes

Introduction Repair of post-TURP sphincter urethral strictures represents challenging problem, due to the risk of urinary incontinence after the repair. We described a surgical technique we use to repair these strictures preserving urinary continence in patients with incompetent bladder neck. Materials and methods An observational, retrospective, study was conducted to include patients with post-TURP urethral strictures in the area of distal sphincter. We included only patients with complete clinical data and follow-up who previously underwent TURP or HOLEP or TUIP, and subsequently developed proximal bulbar urethral strictures close to the membranous urethra and the related distal urethral sphincter. Patients were included, if they were fully continent after TURP or other procedures to treat BPH. The primary outcome of the study was treatment failure, defined as the need for any post-operative instrumentation. Secondary outcome was post-urethroplasty urinary continence. Patients showing stricture recurrence or post-operative incontinence were classified as failure. Results Overall, 69 patients were included in the study. Median patient's age was 67 years; median stricture length was 4 cm. Thirty-tree patients (47.8%) underwent previous urethrotomy. Median follow-up was 52 months. Out of 69 patients, 55 (79.7%) were classified as success and 14 (20.3%) as failure. Out of the whole cohort, thus, 11/69 (16%) have a risk of recurrent strictures and 3/69 (4.3%) have incontinence. Conclusions The use of modified ventral onlay graft urethroplasty, using particular non-aggressive steps, is a suitable surgical technique for repair of sphincter urethral stricture in patients who underwent BPH transurethral surgery, using different procedures (TURP, HOLEP, TUIP)

Decoupling Functional and Morphological Convergence, the Study Case of Fossorial Mammalia

Morphological similarity between biological structures in phylogenetically distant species is usually regarded as evidence of convergent evolution. Yet, phenotypic similarity is not always a sign of natural selection acting on a particular trait, therefore adaptation to similar conditions may fail to generate convergent lineages. Herein we tested whether convergent evolution occurred in the humerus of fossorial mammals, one of the most derived biological structures among mammals. Clades adapting to digging kinematics possess unusual, by mammalian standards, humeral shapes. The application of a new, computationally fast morphological test revealed a single significant instance of convergence pertaining to the Japanese fossorial moles (Mogera) and the North-American fossorial moles (Scalopini). Yet, the pattern only manifests when trade-off performance data (derived from finite element analysis) are added to shape data. This result indicates that fossorial mammals have found multiple solutions to the same adaptive challenge, independently moving around multiple adaptive peaks. This study suggests the importance of accounting for functional trade-off measures when studying morpho-functional convergence. We revealed that fossorial mammals, a classic example of convergent evolution, evolved multiple strategies to exploit the subterranean ecotope, characterized by different functional trade-offs rather than converging toward a single adaptive optimum

Focus on Internal Urethrotomy as Primary Treatment for Untreated Bulbar Urethral Strictures: Results from a Multivariable Analysis

Background: The use of internal urethrotomy for treatment of urethral stricture remains a controversial topic in urology.Objective: To investigate outcomes and predictors of failure for internal urethrotomy as primary treatment for untreated bulbar urethral strictures.Design, setting, and participants: We performed a retrospective analysis of patients who underwent internal urethrotomy. Patients with bulbar urethral stricture who did not receive any previous treatment were included. Patients with traumatic, penile or posterior urethral strictures, lichen sclerosus, failed hypospadias repair, or stricture length >4 cm were excluded.Outcome measurements and statistical analysis: The primary outcome was treatment failure. Kaplan-Meyer plots were used to depict treatment failure-free survival. Univariate and multivariable Cox regression analyses were used to test the association between predictors (age, body mass index, diabetes, history of smoking, etiology, stenosis type and length, preoperative maximum flow [pQ(max)]) and treatment failure.Results and limitations: Overall, 136 patients were included. The median stricture length was 2 cm. Median follow-up was 55 mo. At 5-yr follow-up the failure-free survival rate was 57%. On univariate analysis, diabetes, nonidiopathic etiology, stricture length of 3-4 cm, and pQ(max) were significantly associated with treatment failure. These predictors were included in a multivariable analysis, in which pQ(max) was the only significant predictor of treatment failure.Conclusions: Failure of internal urethrotomy for untreated bulbar urethral strictures greatly depends on pQ(max) flow at uroflowmetry. Patients with pQ(max >) 8 ml/s have a high probability of success, while patients with pQ(max) <5 ml/s have a low probability of success.Patient summary: The use of internal urethrotomy in patients with an untreated bulbar urethral stricture should only be considered in selected cases. (C) 2018 European Association of Urology. Published by Elsevier B.V. All rights reserved