Minimal-invasive anterior approach to the hip provides a better surgery-related and early postoperative functional outcome than conventional lateral approach after hip hemiarthroplasty following femoral neck fractures.

INTRODUCTION: Femoral neck fractures (FNF) are one of the most frequent fractures among elderly patients and commonly require surgical treatment. Bipolar hip hemiarthroplasty (BHHA) is mostly performed in these cases. MATERIAL AND METHODS: In the present retrospective study geriatric patients with FNF (n = 100) treated either by anterior minimal-invasive surgery (AMIS; n = 50) or lateral conventional surgery (LCS; n = 50) were characterized (age at the time of surgery, sex, health status/ASA score, walking distance and need for walking aids before the injury) and intraoperative parameters (duration of surgery, blood loss, complications), as well as postoperative functional performance early (duration of in-patient stay, radiological leg length discrepancy, ability to full weight-bearing, mobilization with walking aids) and 12 months (radiological signs of sintering, clinical parameters, complication rate) after surgery were analyzed. RESULTS: Patients in the AMIS group demonstrated a reduced blood loss intraoperatively, while the duration of surgery and complication rates did not differ between the two groups. Further, more patients in the AMIS group achieved full weight-bearing of the injured leg and were able to walk with a rollator or less support during their in-patient stay. Of interest, patients in the AMIS group achieved this level of mobility earlier than those of the LCS group, although their walking distance before the acute injury was reduced. Moreover, patients of the AMIS group showed equal leg lengths postoperatively more often than patients of the LCS group. No significant differences in functional and surgery-related performance could be observed between AMIS and LCS group at 12 months postoperatively. CONCLUSIONS: In conclusion, geriatric patients treated by AMIS experience less surgery-related strain and recover faster in the early postoperative phase compared to LCS after displaced FNF. Hence, AMIS should be recommended for BHHA in these vulnerable patients.

[A new continuous gait analysis system for ankle fracture aftercare]. / Ein neues, kontinuierliches Ganganalysesystem zur Nachbehandlung von Sprunggelenkfrakturen.

BACKGROUND: Correct aftercare following lower extremity fractures remains a controversial issue. Reliable, clinically applicable weight-bearing recommendations have not yet been defined. The aim of the current study was to establish a new gait analysis insole during physical therapy aftercare of ankle fractures to test patients' continuous, long-term compliance to partial weight-bearing restrictions and investigate whether patients can estimate their weight-bearing compliance. MATERIALS AND METHODS: The postoperative gait of 14 patients after operative treatment of Weber B-type ankle fractures was monitored continuously for six weeks (OpenGO, Moticon GmbH, Munich). All patients were instructed and trained by physical therapists on how to maintain partial weight-bearing for this time. Discontinuous (three, six and twelve weeks) clinical (patient questionnaire, visual analogue pain score [VAS]) and radiographic controls were performed. RESULTS: Despite the set weight-bearing limits, individual ranges for overall weight-bearing (range 5-107% of the contralateral side) and patient activity (range 0-366 min/day) could be shown. A good correlation between weight-bearing and pain was seen (rs = -0.68; p = <0.0001). Patients significantly underestimated their weight-bearing time over the set limit (2.3 ± 1.4 min/day vs. real: 12.6 ± 5.9 min/day; p < 0.01). CONCLUSIONS: Standardized aftercare protocols and repeated training alone cannot ensure compliance to postoperative partial weight-bearing. Patients unconsciously increased weight-bearing based on their pain level. This study shows that new, individual and possibly technology-assisted weight-bearing regimes are needed. The introduced measuring device is feasible to monitor and steer patient weight-bearing during future studies.

BMP-2-coated mineral coated microparticles improve bone repair in atrophic non-unions.

Atrophic non-unions are a major clinical problem. Mineral coated microparticles (MCM) are electrolyte-coated hydroxyapatite particles that have been shown in vitro to bind growth factors electrostatically and enable a tuneable sustained release. Herein, we studied whether MCM can be used in vivo to apply Bone Morphogenetic Protein-2 (BMP-2) to improve bone repair of atrophic non-unions. For this purpose, atrophic non-unions were induced in femurs of CD-1 mice (n = 48). Animals either received BMP-2-coated MCM (MCM + BMP; n = 16), uncoated MCM (MCM; n = 16) or no MCM (NONE; n = 16). Bone healing was evaluated 2 and 10 weeks postoperatively by micro-computed tomographic (µCT), biomechanical, histomorphometric and immunohistochemical analyses. µCT revealed more bone volume with more highly mineralised bone in MCM + BMP femurs. Femurs of MCM + BMP animals showed a significantly higher bending stiffness compared to other groups. Histomorphometry further demonstrated that the callus of MCM + BMP femurs was larger and contained more bone and less fibrous tissue. After 10 weeks, 7 of 8 MCM + BMP femurs presented with complete osseous bridging, whereas NONE femurs exhibited a non-union rate of 100 %. Of interest, immunohistochemistry could not detect macrophages within the callus, indicating a good biocompatibility of MCM. In conclusion, the local application of BMP-2-coated MCM improved bone healing in a challenging murine non-union model and, thus, should be of clinical interest in the treatment of non-unions.

New risk and protective factors for severe hypoglycaemia in people with type 1 diabetes.

AIMS: To evaluate risk factors for severe hypoglycaemia (SH) in patients with type 1 diabetes (T1DM). METHODS AND RESULTS: Retrospective observational and comparative study. All SH occurring between 2007 and 2014 in a German population (Lippe-Detmold) were captured. Characteristics of patients with T1DM and SH were compared with a control group being equivalent concerning age, diabetes duration, HbA1c, comorbidity, and ß-blocker treatment. SH was defined as a symptomatic event requiring treatment with intravenous glucose or glucagon administration and being confirmed by a blood glucose measurement of <2.8 mmol/l. Predictive factors for SH were analysed by a multivariable regression model. As many as 405 cases of SH in T1DM occurred in 206 subjects; 50% of episodes were related to 31 patients who experienced ≥3 SH. Need for nursing care (OR 4.88), treatment with NPH (OR 3.68), and impaired hypoglycaemia awareness (OR 2.06) were the strongest risk factors for SH (all p < 0.05, all pFDR-adjusted < 0.10; false discovery rate (FDR)). Depression (OR 0.14), treatment with CSII (OR 0.39) and short-acting insulin analogues (OR 0.31) appeared to be protective (all p < 0.10; FDR-adjusted). The probability of SH onset was significantly higher in patients who had previously experienced recurrent SH episodes. ß-Blocker treatment did not appear to be a risk factor. CONCLUSION: The complex risk for SH in people with T1DM can be reduced by treatment with CSII and short-acting analogues. Future structures of diabetes care will be challenged by the need of treating increasingly geriatric subjects with T1DM having a high risk of SH.

[Talus Fractures - an Update]. / Talusfrakturen ­ ein Update.

Background: Talus fractures are rare and often result from axial trauma. As most of the talus surface is covered by cartilage, the blood supply is limited. Thus talus fractures are seen as one of the most severe fractures and often lead to significant long-term complications. Several studies suggest that the initial fracture classification can lead to correct treatment and that this can influence the long-term outcome. The aim of the current study was to investigate the importance of the initial fracture classification in respect to the radiological outcome in a large patient cohort. Patients and Methods: Over a span of 12 years, 61 patients with talus fractures were treated at our institution. Overall 45 patients were available for a retrospective analysis. Correlation analysis was performed between the initial fracture severity and the radiological outcome. Results: The average follow-up was 17.3 months (range 6-68). Significant correlations were found between the Marti-Weber Classification and Bargon Score (rs = 0.78; p < 0.0001), as well as between the Hawkins Classification and the Bargon Score (rs = 0.80; p < 0.0001). Conclusions: Precise prediction of the expected radiological outcome of talar neck and body fractures is possible through the initial fracture classification alone. Computed tomography is the accepted standard to determine the exact diagnosis and extent of injury.

Characterization of the healing process in non-stabilized and stabilized femur fractures in mice.

BACKGROUND: Although a variety of suitable fracture models for mice exist, in many studies bone healing was still analyzed without fracture stabilization. Because there is little information whether the healing of non-stabilized fractures differs from that of stabilized fractures, we herein studied the healing process of non-stabilized compared to stabilized femur fractures. MATERIALS AND METHODS: Twenty-one CD-1 mice were stabilized after midshaft fracture of the femur with an intramedullary screw allowing micromovements and endochondral healing. In another 22 mice the femur fractures were left unstabilized. Bone healing was studied by radiological, biomechanical, histomorphometric and protein expression analyses. RESULTS: Non-stabilized femur fractures revealed a significantly lower biomechanical stiffness compared to stabilized fractures. During the early phase of fracture healing non-stabilized fractures demonstrated a significantly lower amount of osseous tissue and a higher amount of cartilage tissue. During the late phase of fracture healing both non-stabilized and stabilized fractures showed almost 100 % osseous callus tissue. However, in stabilized fractures remodeling was almost completed with lamellar bone while non-stabilized fractures still showed large callus with great amounts of woven bone, indicating a delay in bone remodeling. Of interest, western blot analyses of callus tissue demonstrated in non-stabilized fractures a significantly reduced expression of vascular endothelial growth factor and a slightly lowered expression of bone morphogenetic protein-2 and collagen-10. CONCLUSION: Non-stabilized femur fractures in mice show a marked delay in bone healing compared to stabilized fractures. Therefore, non-stabilized fracture models may not be used to analyze the mechanisms of normal bone healing.

[Influence of the pelvic trauma registry of the DGU on treatment of pelvic ring fractures]. / Einfluss des Beckenregisters der DGU auf die Versorgung von Beckenringfrakturen.

Fractures of the pelvic ring are comparatively rare with an incidence of 2-8 % of all fractures depending on the study in question. The severity of pelvic ring fractures can be very different ranging from simple and mostly "harmless" type A fractures up to life-threatening complex type C fractures. Although it was previously postulated that high-energy trauma was necessary to induce a pelvic ring fracture, over the past decades it became more and more evident, not least from data in the pelvic trauma registry of the German Society for Trauma Surgery (DGU), that low-energy minor trauma can also cause pelvic ring fractures of osteoporotic bone and in a rapidly increasing population of geriatric patients insufficiency fractures of the pelvic ring are nowadays observed with no preceding trauma.Even in large trauma centers the number of patients with pelvic ring fractures is mostly insufficient to perform valid and sufficiently powerful monocentric studies on epidemiological, diagnostic or therapeutic issues. For this reason, in 1991 the first and still the only registry worldwide for the documentation and evaluation of pelvic ring fractures was introduced by the Working Group Pelvis (AG Becken) of the DGU. Originally, the main objectives of the documentation were epidemiological and diagnostic issues; however, in the course of time it developed into an increasingly expanding dataset with comprehensive parameters on injury patterns, operative and conservative therapy regimens and short-term and long-term outcome of patients. Originally starting with 10 institutions, in the meantime more than 30 hospitals in Germany and other European countries participate in the documentation of data. In the third phase of the registry alone, which was started in 2004, data from approximately 15,000 patients with pelvic ring and acetabular fractures were documented. In addition to the scientific impact of the pelvic trauma registry, which is reflected in the numerous national and international publications, the dramatically changing epidemiology of pelvic ring fractures, further developments in diagnostics and the changes in operative procedures over time could be demonstrated. Last but not least the now well-established diagnostic and therapeutic algorithms for pelvic ring fractures, which could be derived from the information collated in registry studies, reflect the clinical impact of the registry.

[Data validity in a French diagnosis-related group information program]. / Validité de la description d'un groupe spécifique de patients par le PMSI-SSR.

BACKGROUND: Long-term intratracheal ventilated patients need continuous artificial ventilation support. After the acute periods, these patients may benefit from dedicated follow-up in rehabilitation care centers. In this paper, we aimed to study the validity of the data provided by a French diagnosis-related group (DRG) information system. METHODS: For a sample of intratracheal ventilated patients in two rehabilitation units, we compared the data provided in the DRG information system with the data available in the medical charts. Furthermore, we asked the medical, nursing and allied health staff to assess the data provided by the French DRG information system. RESULTS: The diagnosis was found accurate for 86% of hospital stays. In the DRG information system, 77% of the medical care, and 39% of the nursing and allied health care were mentioned correctly. Overall, 55% of the nursing and allied health care procedures in the DRG information system were not reported in the medical charts. The healthcare providers estimated that the frequency of the care provided was underestimated in the DRG information system for 30% of the nursing and allied health care. CONCLUSION: The patients' main characteristics were found correctly reported in the DRG information system. However, the diversity and the frequency of the care provided were underestimated. These underestimates were mainly related to care frequently provided in these patients (for example, urinary catheterization, massages, counseling for relatives).

[Complex pelvic traumas : data linkage of the German Pelvic Injury Register and the TraumaRegister DGU®]. / Das komplexe Beckentrauma : Matching des Beckenregisters DGU mit dem TraumaRegister DGU®.

BACKGROUND: Complex pelvic traumas, i.e., pelvic fractures accompanied by pelvic soft tissue injuries, still have an unacceptably high mortality rate of about 18 %. PATIENTS AND METHODS: We retrospectively evaluated an intersection set of data from the TraumaRegister DGU® and the German Pelvic Injury Register from 2004-2009. Patients with complex and noncomplex pelvic traumas were compared regarding their vital parameters, emergency management, stay in the ICU, and outcome. RESULTS: From a total of 344 patients with pelvic injuries, 21 % of patients had a complex and 79 % a noncomplex trauma. Complex traumas were significantly less likely to survive (16.7 % vs. 5.9 %). Whereas vital parameters and emergency treatment in the preclinical setting did not differ substantially, patients with complex traumas were more often in shock and showed acute traumatic coagulopathy on hospital arrival, which resulted in more fluid volumes and transfusions when compared to patients with noncomplex traumas. Furthermore, patients with complex traumas had more complications and longer ICU stays. CONCLUSION: Prevention of exsanguination and complications like multiple organ dysfunction syndrome still pose a major challenge in the management of complex pelvic traumas.

Invariom refinement of a new monoclinic solvate of thiostrepton at 0.64†Šresolution.

A new monoclinic solvate containing two molecules of the thiopeptide antibiotic thiostrepton in the asymmetric unit has been crystallized in space group P2(1). Single-crystal diffraction data to a resolution of 0.64 Šwere collected at the SLS synchrotron, allowing structure solution by direct methods and resolution of the disorder present. Valence electron density can be observed in the Fourier residual density from refinement with the independent-atom model, which is a prerequisite for successful application of more sophisticated aspherical-atom scattering factors such as the invariom model when aiming to improve the structural model. Invariom refinement improves quality indicators such as R1(F) for thiostrepton, as previously demonstrated for small molecules. The nonspherical electron-density model also allows the direct derivation of a dipole moment and an electrostatic potential for the whole molecule, which is discussed in the context of antibiotic activity and molecular recognition.

Rodent animal models of delayed bone healing and non-union formation: a comprehensive review.

Despite the growing knowledge on the mechanisms of fracture healing, delayed healing and non-union formation remain a major clinical challenge. Animal models are needed to study the complex process of normal and impaired fracture healing and to develop new therapeutic strategies. Whereas in the past mainly large animals have been used to study normal and impaired fracture healing, nowadays rodent models are of increasing interest. New osteosynthesis techniques for rat and mice have been developed during the last years, which allowed for the first time stable osteosynthesis in these animals comparable to the standards in large animals and humans. Based on these new implants, different models in rat and mice have been established to study delayed healing and non-union formation. Although in humans the terms delayed union and non-union are well defined, in rodents definitions are lacking. However, especially in scientific studies clear definitions are necessary to develop a uniform scientific language and allow comparison of the results between different studies. In this consensus report, we define the basic terms "union", "delayed healing" and "non-union" in rodent animal models. Based on a review of the literature and our own experience, we further provide an overview on available models of delayed healing and non-union formation in rats and mice. We further summarise the value of different approaches to study normal and delayed fracture healing as well as non-union formation, and discuss different methods of data evaluation.

[Analysis of clinical pathway in changing and disabling neurological diseases]. / Analyse du parcours de santé au cours des maladies neurologiques handicapantes et évolutives.

Neurological diseases are characterized by the complexity of care and by a constant and changing disability. More and more frequently, their impact on the clinical pathway remains unknown. Seven postgraduate rehabilitation students (Master coordination du handicap, université Pierre-et-Marie-Curie, Paris) reconstructed the clinical pathway of 123 patients with various neurological diseases: multiple sclerosis, Alzheimer disease, amyotrophic lateral sclerosis, spinal trauma, Parkinson disease and brain tumors. There was a significant correlation between disease duration and the number of specialists involved in care, the number of prescribed drugs and the number of short-term hospitalizations; there was no correlation with age. This result suggests that with time an increasing number of complications related to the initial neurological disease developed. Hospitalization in rehabilitation units was highly correlated with the degree of disability and also with the help received by the patients during the course of their disease. This result suggests that these hospitalizations were a direct consequence of burn out among relatives. General practitioners (GP) were highly involved only during the initial part of the pathway, and their involvement rapidly declined thereafter, suggesting a probable relation with the specificities and the complexity of care for neurological diseases which induces a progressive transfer of responsibilities from the GP to the hospital. Social care was always incomplete and occurred too late during the course of the disease. The feeling by the patients that their care pathway was chaotic was highly correlated with the quality of the information given to the patient at the time of the announcement of their disease. This study confirms that cares for neurological diseases is highly specific and that expert centers and coordination networks are in a key position to ensure an efficient care pathway.

[Anterior approaches to the pelvic ring]. / Anteriore Zugänge zum Beckenring.

Anterior approaches for the stabilization of anterior and also posterior B and C type instability of the pelvic ring were the standard procedures before minimally invasive percutaneous methods supported by image intensifiers or navigation devices were established. Anterior approaches are currently still of high relevance for difficult or impossible closed reductions in multiple trauma surgery where the patient must remain in a supine position. They are also used for stabilization of an increasing number of osteoporotic fractures in the elderly which are no longer only treated in specialized pelvic trauma centres. The anterior as well as the posterior part of the pelvic ring can be stabilized via various anterior approaches. A Pfannenstiel incision is appropriate for plating of ruptures of the pubic symphysis and can be extended to a modified Stoppa approach if necessary. Fractures of the iliac wings can be approached either laterally or less traumatically, via an anterolateral approach. The latter equates the lateral window of the ilioinguinal approach to the acetabulum, allows visualization of the entire sacroiliac joint and therefore stabilization of not only iliosacral luxation but also luxated fractures with a small iliac fragment. By a combination of the different approaches it is possible to simultaneously stabilize ventral and dorsal instabilities in type C fractures of the pelvic ring with a minimal amount of iatrogenic soft tissue trauma. Although the described anterior approaches are considered as simple exact knowledge of the endangered structures and general risks for each approach are essential for a safe exposure of the anatomical region addressed.

Pantoprazole, a proton pump inhibitor, delays fracture healing in mice.

Proton pump inhibitors (PPIs), which are widely used in the treatment of dyspeptic problems, have been shown to reduce osteoclast activity. There is no information, however, on whether PPIs affect fracture healing. We therefore studied the effect of the PPI pantoprazole on callus formation and biomechanics during fracture repair. Bone healing was analyzed in a murine fracture model using radiological, biomechanical, histomorphometric, and protein biochemical analyses at 2 and 5 weeks after fracture. Twenty-one mice received 100 mg/kg body weight pantoprazole i.p. daily. Controls (n = 21) received equivalent amounts of vehicle. In pantoprazole-treated animals biomechanical analysis revealed a significantly reduced bending stiffness at 5 weeks after fracture compared to controls. This was associated with a significantly lower amount of bony tissue within the callus and higher amounts of cartilaginous and fibrous tissue. Western blot analysis showed reduced expression of the bone formation markers bone morphogenetic protein (BMP)-2, BMP-4, and cysteine-rich protein (CYR61). In addition, significantly lower expression of proliferating cell nuclear antigen indicated reduced cell proliferation after pantoprazole treatment. Of interest, the reduced expression of bone formation markers was associated with a significantly diminished expression of RANKL, indicating osteoclast inhibition. Pantoprazole delays fracture healing by affecting both bone formation and bone remodeling.

[Acetabular fractures in the elderly. Outcome of open reduction and internal fixation]. / Osteosynthese bei Acetabulumfrakturen im Alter. Ist eine Rekonstruktion sinnvoll?

The aim of this study was to analyze the clinical outcome and incidence of hip arthritis in elderly patients with acetabular fractures. Because of poor bone quality in the elderly, even a low-energy trauma may lead to an acetabular fracture. An anatomical reconstruction of the acetabulum is necessary to achieve sufficient stability also for a potential hip arthroplasty. So far, there is very limited information on the outcome of acetabular fractures in the elderly. During a period of 6 years (2001-2006), 48 patients older than 60 years were admitted to our department with an acetabular fracture. Thirty-nine patients were treated operatively and nine patients non-operatively. Twenty-nine operatively treated patients were followed up. Nineteen of them were assessed using EQ-5D, SF-12 and Merle d'Aubigné questionnaires in addition to their clinical examination. Ten other surgical patients were only examined using the questionnaires. Of the 29 patients that were followed up, 5 underwent total hip arthroplasty due to secondary post-traumatic hip arthritis after open reduction and internal fixation (ORIF). The range of motion of the operated hip was comparable to that of the non-operated contralateral side. However, the internal rotation was found to be slightly decreased at the operated side when compared to the non-operated contralateral side. Merle d'Aubigné score and physical and mental SF-12 score components as well as quality of life were better in patients treated with ORIF compared to those patients that were treated by secondary hip arthroplasty. Regarding the different treatment strategies (ORIF vs primary hip arthroplasty vs non-operative treatment) of acetabular fractures in the elderly, data from the literature are conflicting. Our results indicate that ORIF represents a good treatment option for acetabular fractures in the elderly. In patients that did not develop secondary hip arthritis, a good clinical outcome and quality of life was documented.

Isolation and reactivity of an elusive diazoalkene.

Most functional groups, especially those consisting of the abundant elements of organic matter-carbon, nitrogen and oxygen-have been extensively studied and only very few remain speculative due to their high intrinsic reactivity. In contrast to the well-explored chemistry of diazoalkanes (R2C=N2), diazoalkenes (R2C=C=N2) have been postulated in several organic transformations, but remain elusive long-sought intermediates. Here, we present a room-temperature stable diazoalkene, utilizing a dinitrogen transfer from nitrous oxide. This functional group shows dual-site nucleophilicity (C and N atoms) and features a bent C-C-N entity (124°) and a long N-N bond together with a remarkable low infrared absorption (1,944 cm-1). Substitution of N2 by an isocyanide leads to a vinylidene ketenimine. Furthermore, photochemically triggered loss of dinitrogen might proceed through a transient triplet vinylidene. We anticipate the existence of a stable diazoalkene functional group to pave an exciting avenue into the chemistry of low-valent carbon and unsaturated carbenes.

ZM447439, a novel promising aurora kinase inhibitor, provokes antiproliferative and proapoptotic effects alone and in combination with bio- and chemotherapeutic agents in gastroenteropancreatic neuroendocrine tumor cell lines.

BACKGROUND: Therapeutic approaches to gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are still not satisfactory. A new direction in treatment options could be the novel aurora kinase inhibitor ZM447439, which was previously reported to interfere with the mitotic spindle integrity checkpoint and chromosome segregation, but does not interfere with other kinases when used up to 5 muM. METHODS: We evaluated the antineoplastic effects of ZM447439 on growth and apoptosis of the GEP-NET cell lines BON, QGP-1 and MIP-101, representing the different malignant tumor types, using standard cell biological tests as crystal violet assays, caspase activation, DNA fragmentation and cell cycle analysis. RESULTS: ZM447439 dose-dependently inhibited proliferation of all three cell lines with IC(50) values in the nanomolar to low micromolar range. Moreover, aurora kinase inhibition by ZM447439 potently induced apoptosis, which was accompanied by DNA fragmentation and caspase 3 and 7 activation. Furthermore, we observed cell cycle arrest at G(0)/G(1) phase as well as a block in G(2)/M transition. In addition, combined treatment with the chemotherapeutic agents streptozocin and cisplatin augmented significantly the antiproliferative effects of those agents. CONCLUSION: Aurora kinase inhibition by ZM447439 seems to be a promising new therapeutic approach in GEP-NETs, which should be evaluated in further clinical trials.

Validation of experimental charge densities: refinement of the macrolide antibiotic roxithromycin.

Multipole refinements of larger organic molecules have so far been limited to a few exceptional cases. We report an investigation of the detailed experimental electron-density distribution (EDD) of roxithromycin, a macrolide antibiotic consisting of 134 atoms. Although the experimental multipole refinement on high-resolution synchrotron data converged smoothly, validation of the electron density by calculation of an `experiment minus invariom' difference density revealed conformational disorder of the H atoms. Hydrogen disorder is shown to affect the EDD, the electrostatic potential and atomic properties as defined by Bader's quantum theory of atoms in molecules. A procedure to obtain the electron density distribution in the presence of disorder is proposed.