1,721,081 research outputs found
21 - Validation of Finite Element Models
No full textWhile in natural sciences, empiricism is predominant, mathematical modeling is traditionally limited to induc- tive models that extrapolate from repeated experimental observations. The extreme specialization of research has slowly separated mathematical modeling skills from ex- perimental skills in most research groups, and it is not rare to see groups where only one of these skills is truly developed. This is a pity: the complexity involved with understanding the biomechanical behavior of the muscu- loskeletal system is overwhelming; to advance compre- hension, one should be ready to use every technique available
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Fracture non-union epidemiology and treatment
No full textIntroduction
Non-union (NU) is a fracture that will not unite. With over one million fractures per annum in the UK long bone non-union has serious social and economical implications. There is little epidemiological data available specifically looking at this NU patient cohort. Studies that are bone specific quote rates of non-union as a proportion of their study group but there is no data quantifying the incidence of NU in the population or per fracture. Studies have highlighted risk factors associated with atrophic non-union including age, diabetes, non-steroidals, and cigarette smoking. There is scientific interest regarding how best to classify non-unions and the role of biological agents in treating them. Aims
• To quantify the incidence of non-union in a large population and calculate the risk of non-union per fracture according to age, sex and anatomical distribution.
• To assess the causes contributing to non-union and outcomes of treatment in a non-union cohort and validate a new non-union scoring system.
• To test the treatment potential of a novel molecule (monobutyrin) and a growth factor in a small animal model of non-union.
Method
• Using the ICD-10 data from the Scottish population as collected by NHS Scotland the incidence of non-union and fractures were calculated.
• A cohort of 100 non-union patients were studied for risk factors associated with their non-union, treatment outcome and to assess a new NU classification system.
• A rat model of tibial non-union was used to assess the potential of monobutyrin and BMP-2 in treating non-union in an animal model.
Results
• Fracture non-union is very rarely found in children (1 in 500 fractures) and occurs in up to 1 in 50 adult fractures. Non-union of a fracture has a significantly higher risk in young adults than the elderly by about 3 fold. Osteoporosis may not be a risk for non-union. The tibia and clavicle are the sites with the greatest potential for fracture non-union.
• Non-union is multifactorial in two out of three patients. Biomechanical stability, patient host factors and infection must all be considered in every patient. Occult or unexpected recurrent infection is present in up to 10% of patients. When all factors are considered in treatment the outcome is 95% successful with 88% requiring 2 or less procedures to heal the non-union and only a minority requiring adjuvant graft or biological agents. The proposed new classification system is complex and did not clearly identify those patients who would require adjuvant treatment (eg bone grafting or BMP) or those likely to have unsuccessful non-union treatment.
• Monobutyrin and BMP-2 when tested on the small animal non-union model did not improve the success rate of union.
Conclusions
Non-union affects approximately 1000 people per year in Scotland, this figure is not as high as 5-10% of all fractures. It is associated with fractures in young adults and of the clavicle and tibia, treatment can have a very high success rate without the need for adjuvant biological polytherapy when all contributing factors are considered and managed appropriately. A new non-union classification needs to incorporate the multifactorial aspects of non-union without being too complex to use in everyday clinical situations
Epidemiology and outcome of fractures in elderly and super-elderly patients
Full text linkIntroduction Over the next decade it is predicted that there will be an increase in the elderly (≥65 years old) population within Western society especially those aged 80 years or more (super-elderly). Associated with this there is an anticipated increase in the number of patients presenting with fractures in these age groups. There is a paucity of literature describing the outcome of fractures in the elderly and super-elderly, other than those affecting the hip. Aims To describe the epidemiology and outcome of common fractures in the elderly and super-elderly patients. Methods Two prospective fractures databases were used to describe the epidemiology and change in incidence of fractures sustained by elderly and super-elderly patients over a decade for the same patient population. Case-mix and outcome variables for 1310 super-elderly patients sustaining acute fractures were recorded. A cohort of 318 veryelderly (90+ years) patients was compared with a group of 992 elderly (80-89 years) patients. During a three-year period, a prospective consecutive series of 162 elderly patients that underwent internal fixation for an undisplaced intracapsular hip fracture was collected. An established database of proximal humeral fractures was used to describe epidemiology and outcome of these fractures in the elderly. Two hundred and twenty-eight displaced distal radial fractures in super-elderly patients were retrospectively identified from a prospective database of 4024 distal radial fractures. 937 elderly patients with pelvic fractures presenting to the study centre over a 15-year period were identified. Two hundred and thirty-three tibial diaphyseal fractures were prospectively compiled for 225 elderly patients over a ten-year period. One hundred and nineteen (5.1% of all elderly fractures) elderly patients presented with multiple fractures during a one-year period were used to describe the epidemiology and outcome. Results More than a third of all fractures occur in elderly (≥65 years) patients, of which half occur in super-elderly (≥80 years) patients. The risk of sustaining a fracture was significantly increased for elderly (odds ratio (OR) 2.3) and super-elderly patients (OR 2.7) relative to those aged 15 to 64 years old. More than 90% of fractures in the elderly were sustained after a fall from standing height. There was a significant increase in the incidence for the elderly (2025 vs 2318/105/yr, p<0.0001) and super-elderly (3733 vs 4045/105/yr, p=0.0003) fractures between the years 2000 and 2010. The elderly and super-elderly population increased during this time but so did the number of fractures which increased disproportionally. There was an increased incidence in distal radial, proximal humeral and ankle fractures for the elderly and super-elderly populations. The very-elderly (≥90 years) group accounted for only 0.6% of the overall population, but they represented 4.1% of all fractures and 9.3% of all orthopaedic admissions. Patients in the very-elderly cohort were more likely to require hospital admission, were less likely to return to independent living. Lower American Society of Anesthesiologists (ASA) grade and the presence of posterior tilt (p<0.0001) were significant independent predictors of fixation failure of undisplaced intracapsular hip fracture. More than a quarter of elderly patients sustaining proximal humeral fractures had a poor functional outcome, with those patients not living in their own home (p=0.04), participating in recreational activities (p=0.01), able to perform their own shopping (p<0.001) or ability to dress themselves (p=0.02) being at an increased risk of a poor outcome which was independent of fracture severity (p=0.001). The premanipulation dorsal angulation of distal radial fractures was a significant independent predictor of the degree of improvement in the final dorsal angulation (p<0.001) and ulnar variance (p=0.01). No significant difference was observed in activities of daily living (p=0.28), wrist pain (p=0.14), whether the wrist had returned to its normal level function (p=0.25), grip strength (p=0.31) or range of movement (p=0.41) between the malunion group and the non-malunion group. The incidence of pelvic fractures increased from 7.9/105/yr to 13.1/105/yr, of which the majority were fragility fractures of the pubic rami (84%). Pre-injury independence and mobility, socioeconomic status, associated fractures, energy of injury, and male gender were independent predictors of length of stay, return to original place of domicile and one-year mortality. Tibial diaphyseal fractures in the elderly (≥65 years) predominantly occurred in females (73%) after a fall (61%). The overall standardised mortality ratio (SMR) was significantly increased (4.4 p<0.0001) relative to the population at risk and was greatest for elderly female patients (8.1 p<0.0001). These frailer patients had more severe injuries with an increased rate of open fractures (30%) and suffered a greater non-union rate (10%). Distal radial, proximal humeral and pelvic fractures were associated with a significantly (p<0.0001) increased risk of sustaining associated fractures. 4.5% of patients after a simple fall sustained multiple fractures, but due to the frequency of falls in the elderly this mechanism resulted in 80.7% of all multiple fractures. The SMR at one year was significantly greater after sustaining multiple fractures which included fractures of the pelvis, proximal humerus and proximal femur (p<0.001). Conclusion The incidence of elderly and super-elderly fractures increased over the last decade. This increase in incidence was specifically observed for fractures involving the distal radius, proximal humerus, and ankle in the elderly and super-elderly populations. The very-elderly group form a small proportion of the population but are more likely to require hospital admission and are less likely to return to independent living with a longer hospital stay. Lower ASA grade and posterior tilt of the femoral neck were independent predictors of fixation failure of undisplaced intracapsular hip fractures. A poor functional outcome after a proximal humeral fracture was not independently influenced by age and factors associated with social independence were more predictive of outcome. Patients with a high risk of distal radial malunion or poor improvement in the fracture position can be identified pre-manipulation, however malunion does not seem to influence the functional outcome of independent superelderly patients. The incidence of elderly pelvic fractures is increasing, and patient demographics could be used to predict length of stay, return to domicile, and oneyear mortality after a pubic rami fracture. Tibial diaphyseal fractures in the elderly are more common in females after a fall, which are more likely to be open and are associated with a higher prevalence of non-union. There will be financial repercussions associated with the management and ongoing care for these frail elderly patients especially those sustaining multiple fractures, with high admission rates, prolonged length of stay, and the increased level of care needed upon discharge
Growth and differentiation of bone marrow-derived mesenchymal stem cells (BM-MSCs) seeded on calcium sulfate (CaSO4) based scaffolds
Full text linkTissue engineering therapies have been developed over the past few decades for bone repair and regeneration. Tissue-engineered constructs can be fabricated using a range of different materials. Calcium sulfate (CaSO4) based scaffolds have been used as a bone substitute for more than a century and are now commercially available. CaSO4 scaffolds have been reported to be of benefit for the healing of fracture nonunions. Bone marrow-derived mesenchymal stem cells (BM-MSCs) possess the ability to differentiate into osteoblasts. Studies have implanted scaffolds loaded with BM-MSCs into injured areas and discovered that it enhanced the recovery.
In this study, human BM-MSCs were seeded onto two types of disk-shaped CaSO4 based scaffolds – Stimulan (CaSO4) and Genex (CaSO4/ β-TCP) to observe and compare growth, proliferation and osteogenic differentiation of BM-MSCs on the scaffolds. Two time points (7 days and 21 days) were used for each scaffold.
BM-MSCs attached to plastic culture flask surface when observed using microscope. BM-MSCs differentiation assays showed that these cells were able to undergo osteogenic and adipogenic differentiation. Flow cytometry indicated BM-MSCs expressed a specific set of MSCs surface markers which were CD90, CD44, CD73 and CD105. The 4′,6-diamidino-2-phenylindole (DAPI) assay indicated that the number of cells on the scaffolds’ surface increased at day 21 compared to day 7. The DAPI imaged side of half-cut scaffolds showed similar penetration depth of BM-MSCs at day 7 and 21. The cell viability assay– 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay, demonstrated that BM-MSCs were able to remain viable on the scaffolds after cultured for three weeks. BM-MSCs seeded on both types of scaffolds secreted enzyme alkaline phosphatase (ALP) but revealed no significant difference in ALP level between the two types of scaffolds. Variation in donors’ cells behaviour was observed in this study as the patterns differed between donors. In conclusion, both Stimulan and Genex supported BM-MSCs growth, proliferation and osteogenic differentiation. More research on this cell-scaffold construct is needed to optimise its use in clinical practice
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Kneeling function following total knee arthroplasty
Full text linkThe ability to kneel is an important function of the knee joint, as it is required
for many daily activities, including religious practices, professional
occupations and recreational pursuits. The inability to kneel following total
knee arthroplasty (TKA) is frequently a source of disappointment. This work
investigates patients’ understanding of the term ‘kneeling’ and what
proportion of patients can kneel before and after TKA, as well as identifying
the factors that can affect the ability to kneel following TKA. The underlying
hypothesis tested was: “There are no differences between kneeling ability
before and after TKA”.
Kneeling ability after TKA may be affected by many factors, including patient-specific
factors, the extent of wear on RPC (Retro patellar Cartilage), postoperative
AKP (Anterior Knee Pain) and post-operative ROM (Range of
Motion). Thus a consecutive series of TKA patients were assessed to test the
afore-mentioned hypothesis. In particular, the thesis has examined:
• Interpretation of kneeling and perceptions of kneeling ability after
TKA.
• The extent of wear on Retro Patellar Cartilage (RPC) and its
correlation to kneeling ability.
• Sensory changes in the knee after TKA.
• Preoperative and Postoperative Anterior Knee Pain (AKP)
assessment.
• The reality of kneeling ability before and after TKA.
• Postoperative ROM of the knee and its correlation to kneeling
function.
The advice offered by healthcare professionals may contribute to a low postoperative
rate of kneeling. The patellofemoral joint plays an essential role in
knee function and a person’s kneeling ability, may be greatly affected by the
performance of this joint.
Firstly, this study analysed the responses of two samples of participants
drawn from diverse cultural backgrounds (Christian and Muslim), it examined
their primary interpretation of what kneeling constitutes, along with a
subjective assessment of the importance of kneeling in their everyday lives.
Secondly, it explored patients’ perceptions of their kneeling ability after TKA,
with a comparative analysis of their responses to the kneeling questionnaire
specifically constructed by the author and also the question in relation to
kneeling in the Oxford Knee Score (OKS). The third component investigated
retro-patellar cartilage (RPC) morphology using intraoperative examination
and standardised photography. Fourthly, a cohort of patients listed for TKAs
was followed prospectively, in order to assess their kneeling ability prior to
and following treatment, along with identifying the factors that could affect
this function, i.e. knee pain, range of motion, sensory changes and sensitivity
to pain on the anterior aspect of the knee as assessed with dolorimetry.
Differences were detected in the subjective interpretation of the kneeling
function, as well as its importance, for the two diverse cultures involved in
this study.
Pain, as opposed to poor range of movement, was identified as the main
reason which led to kneeling difficulties. The majority of respondents
reported that it was either extremely difficult or impossible to kneel on the
operated knee. The high flexed position (required for prayer in certain
cultures) was the most difficult position to achieve for most of the patients.
Prior to surgery, 30 patients were seen during this period, 15 (50%) out of 30
consecutive patients were unable to kneel in any position whatsoever. Of
those who could kneel to some degree, the most common posture that they
could achieve was the upright kneeling position.
Considerable variations were found to occur in patients’ understanding of the
term ‘kneeling’. Consequently, this has significant implications for the design
and interpretation of questions in relation to kneeling for diverse cultures,
which are characterised by distinct lifestyles. The current patient-based selfV
administered questionnaires, such as the OKS, although useful as a simple
measure of overall knee function, were found to have limitations as an
effective assessment tool in the measurement of kneeling function either
before or after TKA and indicate that there is a need for a culturally
appropriate questionnaire to assess kneeling function.
Retro-patellar cartilage lesions were very prevalent in patients undergoing
TKA. However, no significant correlation existed between the total amount of
retro-patellar cartilage wear and the ability to kneel. Patients were more likely
to be able to kneel if the cartilage of the superior facets of the patella were
disease free (P=0.02).
At the six months post-surgery stage, of the 14 consecutive patients, who
could kneel pre-operatively 6 were able to kneel post-operatively. Of the 13
consecutive patients who were unable to kneel pre-operatively, all were
unable to kneel post-operatively. Knee pain was the main reason attributed
to this difficulty. However, no link was found to occur between sensory
changes and kneeling function in the patients who participated in the study,
after TKA performed via an anterior midline incision
Effect of cortical bone decollagenisation on fracture biomechanics at low strain rate
Full text linkINTRODUCTION:
The ability of bone to resist failure is directly dependant on the intrinsic properties, namely the inorganic (hydroxyapetite) and organic (collagen) contents.
Traditionally, inorganic content has been associated with stiffness of bone, whereas organic content has been associate with toughness. The aim of this research is to study the biomechanical effects of staged demineralisation and decollagenisation of femoral cortical segments. The staged protocol for decollagenisation should be considered a novel component of this study.
A clinical correlation study to complement the biomechanical work was also undertaken. Femoral shaft fracture patterns in all ages were clinically and radiologically assessed to delineate if any correlation exists with the biomechanical findings of manipulated bone.
METHODS:
Ovine femoral cortical bone specimens were demineralised in 10% EDTA under ultrasonic assistance. Decollagenisation was achieved using 5M and 10M NaOH solution at 44 degrees celsius. Bone processing was undertaken at time points 0, 6, 12, 24 and 48 hours. Samples were mechanically tested under low strain four-point bending. ANOVA testing was undertaken to compare groups with p<0.05 significant.
This biomechanical data was correlated with clinical data analysing femoral shaft fractures in three age groups; (paediatric (0-16), adult (17-54) and older age (>55)) to reflect immature, peak bone age and osteoporotic bone respectively.
Binary logistic analysis was used to assess significance of bone age with respect to fracture pattern (pvalue <0.05 was significant).
RESULTS:
Demineralised bone demonstrated a reduction of ultimate strength, yield strength and elastic modulus at 48 hours (p<0.05). There was significant increase in toughness at 48 hours.
Decollagenised bone showed a reduction in ultimate and yield strength at 12 hours. There was an initial increase in elastic modulus at 6 hours after immersion in both NaOH solutions (p<0.05), followed by progressive reduction. There was over 70% decrease in toughness in decollagenised samples at 48 hours (p<0.05).
A total of 163 patients with femoral shaft fractures were analysed. Paediatric, adult and older groups included 38, 37 and 88 patients respectively. One hundred and two (102) fractures were simple and 61 comminuted. Paediatric and older groups were more likely to sustain a simple fracture, with the adult group more likely to sustain a high energy comminuted fracture.
CONCLUSION:
Demineralised bone develops an increased ability to deform under bending with an increase in yield strain, ultimate strain and post-yield strain. This makes it tougher, behaving as a ductile material.
In contrast, decollagenised cortical bone behaves as a brittle material. There is a progressive decrease in yield and ultimate properties of stress and strain. Post-yield properties are almost zero with greater rates of decollagenisation.
This study demonstrates an association between degree of fracture comminution and physiological age, with simple fractures being significantly associated with immature and osteoporotic bone. High energy mechanism trauma was directly related to fracture comminution at peak bone age
Methods of estimating bone mineral density in digital radiography
Full text linkAssessment of bone mineral density (BMD) through Dual X-ray Absorptiometry
(DXA) is a well established clinical technique. However, use of DXA is limited to
the elective outpatient setting as a modality for detection of osteoporosis, and not
available in the acute trauma setting prior to fracture fixation. This limits its use as a
modality for estimating BMD prior to fracture fixation, and so limits its ability to
influence choice of fixation materials. Given the limited resources of the current
health system, such a technique of pre-operative BMD estimation would have to be
performed from pre-operative plain radiographs or, more recently, pre-operative
digital radiographs. Various measures have been suggested as indicators of BMD in
plain radiographs, including: use of cortical measures, cortical ratios and summation
of cortical measures; use of textural measures; and use of aluminium grading
systems. Promising results have been reported with these measures in plain
radiographs, however significant limitations exist with these techniques including
variations in film quality and magnification, failure to account for the effects of soft
tissue attenuation and scatter phenomenon, and inconsistent film processing
techniques. With the introduction of digital imaging to clinical practice, it has been
suggested that many of these limitations can been corrected for by the digital
processing technique. As such, digital radiography provides clinicians with a
potential tool to provide pre-operative BMD measures, allowing the potential to
modify choice of fracture fixation materials accordingly. However limited research
has been performed in this field to validate this technique.
In this thesis the possibility of estimating BMD from digital radiographs by
comparing various methods against results obtained from DXA scanning was
investigated. When considering radiographs of the hip, cortical measures and cortical
indices showed good correlations with hip DXA results, with the correlation being
strengthened by summations of cortical measures. Textural measure analysis showed
poor correlation with hip DXA results. Use of aluminium equivalent grading showed
poor correlation with hip DXA results. When considering radiographs of the wrist,
cortical measures and cortical ratios showed varying correlations with forearm and
hip DXA results, ranging from poor to good. Summation of cortical measures failed
to provide improved correlation values. Use of aluminium equivalent grading
showed good correlation with forearm and hip DXA results.
In conclusion, this thesis shows the potential for estimation of BMD from digital
radiographs in the pre-operative setting. For the proximal femur, the summation of
cortical measures provided the best estimation of bone density, whereas for the distal
radius aluminium equivalent grading provided the best estimate. Further analysis is
however required to establish if these techniques provide an adequate indicator of
fixation strength in bone and so effectively guide pre-operative selection of fracture
fixations materials
- …
